ZO-1), ZO-2 and ZO-3 and histone deacetylase 1 (HDAC1) and HDAC2 in AR patients compared to healthy controls. RNA samples were extracted from nasal epithelial cells of house dust mites (HDMs)-sensitized AR patients and healthy controls (n = 28 in each group). The RNAs were reverse transcribed into cDNAs for measurement of ZO-1, ZO-2, ZO-3, HDAC1 and HDAC2 expression levels by quantitative PCR. The mRNA expression of ZO-1 was significantly decreased in AR patients compared to healthy controls (p = 0.010). No significant difference was observed in the expression levels of ZO-2, ZO-3, HDAC1 and HDAC2 in AR patients compared to healthy controls. We found significant associations of higher HDAC2 levels in AR patients with lower frequency of changing bedsheet (p = 0.043) and with AR patients sensitized to Dermatophagoides farinae (p = 0.041). Higher expression of ZO-2 was observed in AR patients who had pets (p = 0.007). In conclusion, our data indicated that ZO-1 expression was lower in AR patients contributing to decreased integrity of nasal epithelial barrier integrity, and HDAC2 may be involved in the pathogenesis of the disease.Allergic rhinitis (AR) is a common allergic disease characterized by disruption of nasal epithelial barrier. In this study, we investigated the mRNA expression of zonula occludens-1 ( Dermatophagoides pteronyssinus (D. pteronyssinus) delivers cysteine proteases that increases the epithelial permeability by disrupting claudin-1, occludin and ZO-1 molecules (Allergic rhinitis (AR) is an IgE-mediated inflammation disorder of the nasal mucosa caused by infiltration of allergens . This leolecules .e.g., occludin, claudins and tricellulin) and junctional adhesion molecules  is a group of enzymes that can repress the transcription of gene through deacetylation of histone molecules. HDAC acts by removing an acetyl group from lysine on histones . HDACs red HDAC1 . HDAC2 ied HDAC1  and HDACed HDAC1 . Human lC1 (ZO-1 . In addiC1 (ZO-1 .Dermatophagoides farinae (D. farinae), D. pteronyssinus and Blomia tropicalis , which are the most common aeroallergens affecting AR population in Malaysia  and HDACs (HDAC1 and HDAC2) in AR patients compared to healthy controls in subjects recruited from Hospital Universiti Sains Malaysia, Kelantan, Malaysia. The associations of the expression levels of ZOs and HDACs with the clinico-demographical parameters of AR patients and healthy controls, as well as patients’ lifestyle were measured.Our gene expression studies and their associations with clinico-demographical and environmental parameters in AR patients are divided into two parts. The first part of this study focused on ZO proteins and HDACs, while the second part focused on occludin, claudins and desmogleins. In this study, we aimed to investigate the mRNA expression of ZOs (n = 28) were volunteers and they were staffs or students within the Health Campus, USM. Only adults of 18 years and above were chosen to participate in this study, and they were legally competent to fill in the written consent. The Human Research Ethics Committee of Universiti Sains Malaysia (JEPeM) authorized the study’s protocols (approved ethics code: USM/JEPeM/18060273).Participants were recruited from Otorhinolaryngology-Head & Neck Surgery (ORL-HNS) clinic, Universiti Sains Malaysia (USM), Kubang Kerian, Kelantan, Malaysia. A total of 28 moderate-severe persistent and intermittent AR patients were recruited, and classification of AR patients was based on the ARIA guidelines . Healthyn = 28 in each group).Sample size was calculated according to the difference of means between two independent groups using the software Power and Sample Size (PS) version 3.1.9.3  based on previous qPCR studies of nasal mucosa tissue samples . A two-tDuring the recruitment process, all participants were given detailed information about the study. The written consents were obtained from the participants for the investigators to proceed with the recruitment, performing SPT, taking participants’ nasal epithelial samples via nasal brushing for experiments and publish the results. All samples were labelled anonymously, and handling of all data was conducted anonymously where none of the participant’s private information such as name was disclosed. All experimental procedures were carried out in accordance with the institutional guidelines and regulations.i.e., D. pteronyssinus, D. farinae and B. tropicalis. Sterile lancets  were used to prick the skin gently through the drops of allergen. The reactions were observed after 15 to 30 min. The formation of wheal indicated the presence of antibodies against the allergen. Patients with wheal size of  ≥4 mm for HDM allergens and not for saline were considered positive for sensitization and they were recruited to participate in this study. Healthy controls were recruited if they did not show any reaction towards all the allergen extracts.Allergen SPT was performed to the subjects prior to collection of nasal epithelial cells samples. Saline was used as the negative control, histamine as the positive control and allergen extracts were applied to the skin. Allergen extracts consisted of three types of HDMs Cytology brush was used to collect nasal epithelial cells by brushing softly the surface of nasal inferior turbinate. Inferior turbinate tissue biopsy is an alternative method for the collection of nasal epithelium and detection of allergen-specific IgE, however tissue biopsy methodology is invasive and it has recently been shown that nasal mucosal brushing is comparable with inferior turbinate tissue biopsy for the diagnosis of local AR . In addi® Mini Kit (QIAGEN). Cells from nasal brushings in RLT buffer were pelleted by centrifugation . One volume of 70% ethanol was added to the lysate and transferred to an RNeasy Mini spin column placed in a 2 ml collection tube. After the centrifugation, buffer RW1 was added to the column. The extraction was further continued with DNA digestion by adding DNase I stock solution mixed with Buffer RDD from RNase-Free DNase Set. The RW1 washing buffer was added to the column and ethanol was added again to increase the purity of the RNA yield. To improve the quality of the RNAs, two times of RPE washing buffer were added to the column. After centrifugation, the spin column was transferred to new collection tube and then spun once more to remove excess solution. Lastly, RNeasy spin column was placed into new collection tube and 40 µl RNase-free water was added to elute RNA. RNA quantity and quality were measured using Epoch™ Microplate spectrophotometer .Total RNA was extracted using RNeasyRNA samples were reverse-transcribed to cDNA using iScriptTM Reverse Transcription Supermix for RT-qPCR . The RNA samples were synthesized to cDNA using the thermocycler GeneAmp® PCR System 9700 . The PCR condition was set up at 25 °C for 5 min at priming, 46 °C for 20 min at reverse transcription and RT inactivation for 1 min at 95 °C for 1 cycle. The synthesized cDNA samples were measured using EpochTM Microplate spectrophotometer.ZO-1, ZO-2, ZO-3, HDAC1 and HDAC2) using Mx3005p qPCR thermal cycler . The primers  were designed using NCBI Primer-BLAST  and designed primers . Shapiro–Wilk normality test was used to determine whether the data was normally distributed. Associations of the gene expression (median cut-off) with clinico-demographical and environmental parameters were examined using the n = 21 (75%) versus n = 7 (25%)]. The most commonly reported comorbidities by moderate-severe AR patients were sinusitis , and conjunctivitis . Other comorbidities include pharyngitis , asthma , otitis media  and lymphoid hypertrophy or obstructive sleep apnea . The number of participants exposed to secondhand cigarette smoke was higher in moderate-severe AR patients  than in healthy controls . There was no difference in home location  or living in an industrial area between healthy controls and moderate-severe AR patients.The demographic data of the subjects are shown in ZO-1, ZO-2, ZO-3, HDAC1 and HDAC2 mRNA expression were measured in NECs of AR patients and healthy controls. Shapiro–Wilk normality test showed that the data were not normally distributed. Thus, Mann–Whitney U test was used. ZO-1 expression was significantly lower in AR patients (p = 0.010) compared to controls (ZO-2 (p = 0.868) and ZO-3 (p = 0.351) in AR patients compared to controls  and HDAC2 (p = 0.693) in AR patients compared to healthy controls  (D. farinae)    of AR patients (The expression of each gene (median cut-off) was examined in terms of their association with demographical parameters of AR patients and healthy controls. Higher = 0.043)  and sens= 0.041)  in patied HDAC2) . Family patients .ZO-2 expression was significantly higher in those with pets at home    . Other pd HDAC2) .HDAC2 expression did not differ significantly between healthy controls and AR patients in terms of one or multiple types of HDMs sensitization  are thought to play important roles in producing and maintaining specialized membrane domains in various types of cells . Similare.g., pollens)  in Malaysia.Pertaining to HDACs, we did not observe significant difference in the expression levels of HDAC1 and HDAC2 in AR patients compared to controls. HDAC1 can suppress TWIK-related potassium channel-1 (Trek1) in the nasal mucosa essential in preserving the epithelial barrier function , establipollens)  but distD. farinae was detected on rhinitis children’s beddings compared to controls  We focused on HDM-sensitized AR patients only without the inclusion of other allergens during SPT. It is plausible that our cohort of AR patients were also allergic to other allergens which may contribute to the TJs disruption; (2) In our study, the gene expression was sufficient to demonstrate the presence of ZO and HDAC. Although protein expression data is important to confirm the existence of ZO and HDAC gene, however we could not perform the protein analysis in this study due to budget constraint. (3) We did not measure specific IgE tests for all the allergens. In the future, we would like to further investigate more on protein expression levels, which will help to strengthen our research.In summary, our data indicate that ZO-1 is a key TJ molecule whose reduced expression is associated with defective nasal epithelial barrier integrity in HDM-sensitized AR patients. These results support development of therapies that restore ZO-1 expression in nasal epithelial cells of AR patients. The expression profile of ZO-2, ZO-3 and HDAC2 were demonstrated in AR patients relative to non-allergic subjects for the first time. Collectively, dysregulated ZO-1 and HDAC2 expression levels may play key roles in the onset of AR through disruption of nasal epithelial barrier integrity.10.7717/peerj.13314/supp-1Figure S1HDAC2 expression in healthy controls (HC) and AR patients sensitized with any HDM allergen (AR-1-HDM), AR patients sensitized with two HDM allergens (AR-2-HDMs) and AR patients sensitized with three HDM allergens (AR-3-HDMs). (B) Relative HDAC2 expression in HCs and AR patients with their frequency of changing bedsheet of monthly (AR-monthly) and two-monthly (AR-2-Monthly). NS: Not significant.(A) Relative Click here for additional data file.10.7717/peerj.13314/supp-2File S1Click here for additional data file.


Immersive virtual therapy technology is a new method that uses head-mounted displays for rehabilitation purposes. It offers a realistic experience that puts the user in a virtual reality. This new type of therapy is used in the rehabilitation of stroke patients. Many patients after this disease have complications related to the upper extremities that limit independence in their everyday life, which affects the functioning of society. Conventional neurological rehabilitation can be supplemented by the use of immersive virtual therapy. The system allows patients with upper limb dysfunction to perform a motor and task-oriented training in virtual reality that is individually tailored to their performance. The complete immersion therapy itself is researched and evaluated by medical teams to determine the suitability for rehabilitation of the upper limb after a stroke. The purpose of this article is to provide an overview of the latest research (2019–2022) on immersive virtual reality with head-mounted displays using in rehabilitation of the upper extremities of stroke patients. In recent years, rehabilitation using virtual reality has become increasingly popular. VR technology offers capabilities based on human interaction in a simulated environment that receives continuous feedback on performance and efficiency . For effStroke is the second most common cause of death and the third cause of disability in the world. The recorded increase in the incidence of stroke is a serious public health problem, but also a problem of social and economic development of society . Stroke In the review, Guzsvincz, Szucs, and Sik-Lanyi divided reality into virtual, augmented, and mixed reality. Virtual reality is a synthetic environment in which interactions can take place. Augmented reality expands into our reality, as the name suggests, while mixed reality allows interaction with extended objects . The terImmersive VR enables a more comprehensive virtual reality experience in a three-dimensional environment. Computer equipment provides visual and acoustic visualization, which can also be reflected in the tactile interactions of the user. This makes it possible to experience the illusion of being in an imaginary environment that is not visible on the screen. Users who use this form of VR may need a special headband (HMD), but also can use haptic devices, motion trackers, data gloves, and wireless controllers . Visual-Neurological rehabilitation, consisting of platforms, cameras, and sensors used for virtual reality games, is well-tolerated by patients and arouses curiosity. Some studies show that conventional therapies appear monotonous and boring to patients ,25. ThisThe load on the neck and head when using the head-mounted display is an important criterion when choosing therapy for neurological patients having complications in the upper limbs and balance disorders. The use of an HMD causes changes in locomotion and postural control by manipulating optical flow . Neck stIn this review, we discussed rehabilitation using immersion therapy in post-stroke patients with upper limb complications, including: immersion therapy technology, clinical application and evidence of effective use in neurological rehabilitation, barriers that arise in the use of immersion therapy, and considerations for limitations and future use of immersion therapy among post-stroke patients with upper limb complications. This review provides an important contribution to insight into the effectiveness of immersive therapy rehabilitation in stroke patients. Immersion virtual reality therapy with the use of head-mounted displays gives the impression of the possibility of making rehabilitation more effective and engaging, due to the resulting motivation for a virtual reality with which patients interact . Many prImmersive therapy upper limb stroke;Rehabilitation after a VR stroke;HMD stroke rehabilitation;HMD rehabilitation of the upper limb;HMD stroke.The material gathered for this review was sourced from the following databases: PubMed, PubMed Central, Cochrane Library, Embase, Medline, Web of Science, and SCOPUS. The topics searched for included:In addition to the main issues, the abbreviations HMD and VR HMD were also searched. A total of 646 articles were analyzed. After removing the duplicates, 61 articles qualified as well as an additional 8 articles found by manually searching the reference lists. We excluded articles when: Head-mounted displays were not used for their rehabilitation; Rehabilitation was not used for the upper extremities; Rehabilitation was not for stroke patients; Rehabilitation with virtual reality was non-immersive or semi-immersive; Head-mounted displays were used for purposes other than rehabilitation of the upper extremities; Studies were published in a language other than English. Therefore, only 7 studies were approved to be studies included in our qualitative synthesis that met all requirements .Immerse VR is a relatively new form of neurological rehabilitation in patients with disorders in the upper limb after a stroke, which is why the number of studies in this area is limited. The research found from the last 5 years is presented in the tables below .The longest study involving patients lasted 12 weeks , the shoAll of the studies collected in the review used their own type of virtual games performed by patients to improve the indicators of the upper limb. Games that were used consisting of cooking, decorating trees with leaves and fruits, collecting vegetables, playing drums , climbinTwo studies conducted by Mekbib in 2020  and 2021The conducted studies presented their results as: an improvement in the function of the upper limbs ,48,49,50Of the seven studies, only one study conducted by Hsu et al. investigated the occurrence of adverse reactions to HMD. The authors did not record any adverse events such as dizziness, visual disturbances, or injuries to the upper extremity . This shNone of the seven articles addressed the head-mounted display, which could affect posture control and strain on the head and neck. These limitations may have been relevant to the results obtained by patients during rehabilitation.The purpose of this review was to look for studies with neurological rehabilitation of the upper limb for people after a stroke, in which immersion therapy with a head-mounted display (HMD) is used. This offers a broader view of a new and still rarely used technology that could have potential benefits in future rehabilitation. Virtual reality provides a rich and customized motor training, thanks to intensity modulation and sensory feedback ,52. The studies considered in this review had small samples of subjects; some of them were feasibility and pilot studies ,46. ThisThe use of immersive VR in neurological rehabilitation in patients with upper limb dysfunction after a stroke is still being studied. This is a relatively new advance in technology that is not as extensively researched as non-immersive VR . This reIn recent years, many studies have been conducted using fully immersive environments for imbalances ,54,55, gA major barrier of virtual reality rehabilitation for the elderly can be modern technologies with touch equipment, large screens, goggles covering the entire eyes, or even motion controllers. Such equipment, if patients have not previously shown interest in virtual technology, can be a novelty or even a misunderstanding, which affects the emergence of digital exclusion. In the study by Kamińska, Miller, Rotter et al., patients of mature age found that training in virtual reality technology was a way to stop the process of digital exclusion. The benefit of getting used to the virtual world allowed them to adapt to modern technologies . The deployment of new digital services and platforms has been caused by the COVID-19 pandemic. Accelerated change can be a problem and a challenge for older and less prosperous people. The phenomenon of the digital divide is becoming increasingly noticeable. Divide is described as an incongruity between groups in which one group has the resources, the will, and the ability to use digital technologies, and in the other group, the capacity and resources for an advanced approach are lacking. In this group, lack of measures can lead to demographic and socioeconomic inequalities around the world ,64,65. TTechnology is constantly changing, which can pose a threat to the profession of physiotherapists, who indicate that they feel unprepared. There is a concern about whether all physiotherapists will cope with the progress of the digital and technological age . EmployeLike any other therapy, rehabilitation with the use of virtual reality also has its drawbacks, in particular, fully immersive therapy. Studies relating to the side effects of immersive VR therapy are mixed. Some of them have shown that using full immersion had a negative effect on static balance and was associated with side effects: headaches, dizziness, eye strain, and motion sickness ,69. In aInterest in virtual technology in rehabilitation is constantly growing. The first scientific articles on rehabilitation and virtual reality date back to 1962, according to the PUBMED research viewer. In 2022, 2040 works had been published under the keyword “VR rehabilitation”. The keyword “Immersion Head Mounted Display rehabilitation” has been used in 65 articles since 1998, which shows that more and more people from the medical world are no longer interested only in using non-immersive reality for the rehabilitation of patients. Rehabilitation with the use of HMDs in virtual reality does not seem to have the danger of losing interest in therapy among patients. In order to preserve the progress of technology and motivation among users, the level and variety of games used in rehabilitation programs should be constantly improved. Program updates with the ability to get new games would contribute to maintaining clinical progress. Fully immersive virtual reality therapy with head-mounted displays (HMD) appears to be beneficial for patients with upper limb complications after a stroke. Despite the small amount of research, the therapy seems to be promising, affecting the regeneration of the upper limb. In order to clearly prove the positive effects of VR immersion therapy, a larger number of studies should be performed with a larger research sample and a longer study time.


Allergic rhinitis (AR) and asthma are closely related, and AR is regarded as an important risk factor for the onset of asthma. However, the pathogenesis of the development of asthma from AR is still undefined.The aim of this study was to investigate the mechanisms underlying the development of asthma from AR by comparing the transcriptome features of patients with AR with and without asthma.Patients with AR with or without asthma caused by weed pollen who presented to the Allergy Clinic of Peking Union Medical College Hospital were recruited for this study. Peripheral blood samples of all the patients were collected during the weed pollen season (September) when the patients had allergic symptoms and outside the pollen season (November) when the patients had no symptoms. Transcriptomic analysis was conducted, and the differentially expressed genes (DEGs) and enriched immune pathways between the patients with AR with asthma (AR-asthma group) and those without asthma (AR group) were identified. In addition, the expression levels of some pivotal differentially expressed RNAs were quantified using quantitative polymerase chain reaction (PCR).P value < 0.05, enriched by the upregulated genes in the AR-asthma group compared to the AR group included antifungal humoral response, neutrophil-mediated killing of bacterium, antibacterial humoral response, antimicrobial humoral immune response mediated by antimicrobial peptides, and regulation of the T cell receptor signaling pathway. The immune-related GO terms with P values <0.05 enriched by downregulated genes were positive regulation of natural killer cell-mediated cytotoxicity, microglial cell activation, natural killer cell activation, and leukocyte-mediated cytotoxicity. The GO term of antimicrobial humoral immune response mediated by antimicrobial peptides was upregulated both during and outside the pollen season, and the upregulated expression of three DEGs  included in this term was verified through quantitative PCR.During the weed pollen season, the immune-related Gene Ontology (GO) terms with The activation of the antimicrobial immune response mediated by neutrophils and the depression of cytotoxicity mediated by natural killer cells may play roles in the progression from AR to asthma. Allergic rhinitis (AR) is a common allergic airway disease that affects 14% of adults in the United States . The incThe pathogenesis underlying the development of asthma from AR is unclear. Some authors have discussed the predictors for the progression from AR to asthma and reported that cigarette smoking, female sex, and bronchial hyper-responsiveness are possible risk factors for the onset of asthma in patients with AR –12. PangThe aim of this study was to investigate the mechanisms underlying the development of asthma from AR by comparing the features of gene expression through transcriptome sequencing between patients with weed pollen induced AR and asthma and patients with weed pollen induced AR only. Because of the existence of persistent inflammation in the airway of patients with seasonal AR and asthma during and outside the pollen season , 17, theAll the patients included in this study were recruited from the Allergy Clinic of Peking Union Medical College Hospital. The inclusion criteria were as follows: 1) adult patients; 2) patients with typical symptoms of rhinitis , includiThis was a cross-sectional study conducted during the autumn and winter seasons of 2020. Peripheral blood samples of the patients were collected at two time points: during the weed pollen season, when all the patients had AR symptoms with or without concomitant asthma (September), and after the weed pollen season, when all the patients had no allergic symptoms (November). Transcriptomic analysis of all blood samples was conducted, and the transcriptomic features of the patients with AR and asthma (AR-asthma group) were compared with those of patients with AR only (AR group) during and outside the pollen season. The expression levels of some pivotal differentially expressed ribonucleic acids (RNAs) identified through transcriptome sequencing were further quantified using quantitative polymerase chain reaction (qPCR).Total RNA was isolated from the blood sample which was stored at −80 °C. Messenger RNA (mRNA) was purified from total RNA using polyT and fragmented into 300–350 bp fragments. First-strand complementary deoxyribonucleic acids (cDNAs) were reverse-transcribed with fragmented RNA and deoxynucleotide triphosphates (dNTPs), and second-strand cDNA synthesis was subsequently performed. After adenylation of the 3’ ends of the DNA fragments, sequencing adaptors were ligated to the cDNA and the library fragments were purified. The template was enriched using PCR, and the PCR product was purified to obtain the final library. After library construction, high-throughput sequencing was performed using the Illumina Novaseq6000 sequencing platform .P value < 0.05. Gene Ontology (GO) enrichment analysis of immune-related process was conducted using ClueGO v2.5.8  and adaptor sequences using Cutadapt v2.7. Thereafter, clean reads were mapped to the human reference genome GRCh38 using HISAT2 v2.1 . ExpressO v2.5.8  in Cytos-(ΔΔCt).Reverse transcription was conducted with the PrimeScript RT reagent Kit with gDNA Eraser for RT-PCR  and the thermal cycler  in a volume of 20 µL. The single cycle was 35 °C for 15 min and the incubation period was 85 °C for 5s. Relative qPCR was done with the Bio-Rad CFX Opus 96 Instrument and TB Green® Premix . Fold induction was calculated using the comparative Ct method and the formula 2P < 0.05. All statistical analyses were performed using SPSS statistical software .Normally distributed data are expressed as mean and standard deviation, while non-normally distributed data are expressed as median and interquartile range. Pearson χ2 test was used to compare sex ratios at baseline, whereas the differences in patient body mass index (BMI), length of AR course, and visual analog scale (VAS) scores between the AR and AR-asthma groups were verified using the Mann-Whitney U test. The expression levels of critical DEGs measured using quantitative PCR were compared between the two groups using t-tests. Statistical significance was set at P = 0.087).Twenty-five patients with AR allergic to weed pollen were recruited for this study. Of these, seven patients had concomitant asthma. As shown in P value < 0.05 were enriched from the 158 upregulated genes and ordered based on the rich factor: antifungal humoral response, neutrophil-mediated killing of bacterium, antibacterial humoral response, antimicrobial humoral immune response mediated by antimicrobial peptides, and regulation of the T cell receptor signaling pathway. Four immune-related GO terms with a P value < 0.05, which included positive regulation of natural killer cell-mediated cytotoxicity, microglial cell activation, natural killer cell activation, and leukocyte-mediated cytotoxicity, were enriched from the 200 downregulated genes and ordered based on the rich factor , regulation of germinal center formation, regulation of memory T cell differentiation, regulation of complement activation, and the Fc-γ receptor signaling pathway (During winter (outside the weed pollen season), when all the patients had no symptoms, 378 genes were upregulated and 507 genes were downregulated in the AR-asthma group compared to the AR group Figure 3The above-mentioned results indicated that the GO term of antimicrobial humoral immune response mediated by antimicrobial peptides was upregulated in the AR-asthma group compared to the AR group both during and outside the pollen season. The results also showed that if the DEGs between the two groups identified during and outside the pollen season were intersected, 39 DEGs were upregulated and 21 were downregulated at both time points Figure 4Based on the above results, LTF, PF4, and ELANE were considered possible key DEGs between the AR-asthma and AR groups, and their expression levels were validated through qPCR. The results of the qPCR showed that during the weed pollen season, the expression levels of ELANE and LTF in the AR-asthma group were significantly higher than those in the AR group, whereas the expression levels of PF4 in the two groups were not significantly different. Outside the weed pollen season, the expression levels of LTF, PF4, and ELANE in the AR-asthma group were significantly higher than those in the AR group Figure 5In this study, we compared the transcriptome features between the AR-asthma group and the AR group and found that the GO term, antimicrobial humoral immune response mediated by antimicrobial peptides, was upregulated in the AR-asthma group compared to the AR group during and outside the pollen season. Most DEGs of this term, including DEFA3, DEFA4, ELANE, and LTF, encode antimicrobial peptides in neutrophils, indicating that the upregulated antimicrobial immune response in the AR-asthma group is mainly mediated by neutrophils. The results also showed that the GO term of neutrophil-mediated killing of bacterium was upregulated in the AR-asthma group during the pollen season. The important role of airway mucosal neutrophils in the pathogenesis of allergic asthma has been reported in several studies. In animal models of allergic asthma, allergen challenge is associated with the recruitment of neutrophils to the airway mucosa , 25. In The enrichment analysis of downregulated DEGs in the AR-asthma group compared to the AR group showed that during the pollen season, the GO terms related to NK cell activation and NK cell-mediated cytotoxicity were downregulated in the AR-asthma group, whereas outside the pollen season, the GO term ADCC was downregulated in the AR-asthma group. ADCC reactions are mainly mediated by NK cells, suggesting that the top downregulated GO terms during and outside the pollen season are consistent and closely related to the activities of NK cells. Compared to the AR group, the AR-asthma group showed depressed cellular cytotoxicity mediated by NK cells. It has been reported that the number and activities of NK cells in patients with asthma are downregulated relative to those in healthy individuals, which is consistent with our findings . Duvall It has been reported that ELANE and PF4 are closely related to the pathogenesis of asthma. ELANE is a gene that encodes the protein elastase, which is a serine protease mainly found in neutrophils  and can The protein encoded by LTF is lacto-transferrin, which is derived from the granules of neutrophils. Lacto-transferrin can inhibit eotaxin-stimulated eosinophil migration into the airway  and prevThis study had some limitations. First, the sample size is relatively small, which may lead to bias. In this condition the heterogeneity among different patients may have interfered with the data analysis. Second, there are no healthy controls in this study, and the transcriptomic differences between the AR-asthma group and healthy subjects will provide more supportive evidence for the current findings. Third, we did not validate the results of RNA sequencing and qPCR with specific protein quantitation using western blot assay.This study focused on the GO terms related to immune reactions while analyzing the difference of transcriptome data between AR and asthma group, and found that the activation of the antimicrobial immune response mediated by neutrophils and the depression of cytotoxicity mediated by NK cells may be involved in the development of asthma from AR. However, prospective studies should be conducted in the future to verify the current findings, in which patients with only AR are recruited and followed up for years until asthma develops. The essential factors involved in the development from AR to asthma could be confirmed through the pair comparison between the AR stage and AR-asthma stage in the same person. Also further experiments in protein level and in animal models are needed to investigate the underlying specific mechanism in the future.The data presented in the study are deposited in the Genome Sequence Archive for Human repository of National Genomics Data Center of China, accession number HRA002991.The studies involving human participants were reviewed and approved by Peking Union Medical College Hospital Review Board. The patients/participants provided their written informed consent to participate in this study.We claim that we have directly participated in the planning, execution and analysis of the study. KG designed the project and guided the study. LL, ZW, LC, and YX contributed to the patient recruitment and quantitative PCR. LL, HZ, XW, and KG contributed to the transcriptomic RNA sequencing and bioinformatics analysis. LL wrote the manuscript. ZW, LC, YX, HZ, XW, and KG revised the manuscript. All authors contributed to the article and approved the submitted version.


Robot-assisted surgery is becoming popular in the operation room (OR) for, e.g., orthopedic surgery (among other surgeries). However, robotic executions related to surgical steps cannot simply rely on preoperative plans. Using pedicle screw placement as an example, extra adjustments are needed to adapt to the intraoperative changes when the preoperative planning is outdated. During surgery, adjusting a surgical plan is non-trivial and typically rather complex since the available interfaces used in current robotic systems are not always intuitive to use. Recently, thanks to technical advancements in head-mounted displays (HMD), augmented reality (AR)-based medical applications are emerging in the OR. The rendered virtual objects can be overlapped with real-world physical objects to offer intuitive displays of the surgical sites and anatomy. Moreover, the potential of combining AR with robotics is even more promising; however, it has not been fully exploited. In this paper, an innovative AR-based robotic approach is proposed and its technical feasibility in simulated pedicle screw placement is demonstrated. An approach for spatial calibration between the robot and HoloLens 2 without using an external 3D tracking system is proposed. The developed system offers an intuitive AR–robot interaction approach between the surgeon and the surgical robot by projecting the current surgical plan to the surgeon for fine-tuning and transferring the updated surgical plan immediately back to the robot side for execution. A series of bench-top experiments were conducted to evaluate system accuracy and human-related errors. A mean calibration error of 3.61 mm was found. The overall target pose error was 3.05 mm in translation and  Annually, 266 million individuals suffer from spinal diseases worldwide, with an incident rate of 5.7% in Europe . Spinal In conventional PSP, screw positioning is done by free-hand operation. In open surgery, the surgeon inserts screws based on bone landmarks. Traditionally, this happens without the assistance of image guidance. Experts rely on rich experiences to map the bony landmarks to the pre-operatively planned trajectory. Recently, computer-assisted navigation with medical imaging became popular in the operating room (OR) as it offers additional guidance for the surgeon. C-arm fluoroscopy is often used in PSP as it provides a live, continuous X-ray image that is visualized on a display. This intraoperative imaging provides information on how the drill is positioned with respect to the vertebra. Based on this image, the surgeon can update the instrument’s position. In-vivo studies showed that fluoroscopy-based guidance improves the pedicle screw insertion accuracy to 93.9% among 2003 cases . Though Recently, some navigation systems based on augmented reality (AR) or mixed reality (MR) were proposed for spine surgery ,6,7,8. MRobot-assisted approaches have been widely investigated to improve the feasibility and repeatability of screw placement ,11,12. SThe paper introduces an intuitive interactive control scheme for human–robot interaction (HRI) exploiting AR to guide a surgical robotic arm for pedicle screw placement. The system allows the user to visualize and adjust the surgical plan intraoperatively via the AR scene. The immersive user interface allows the user to monitor the robot’s execution and intervene. Hereto, the operator can co-manipulate the robot to perform surgical actions, such as positioning the robot, drilling, and retraction.The communication between the robot controller and the robotic arm was achieved using the robot operating system (ROS). To ensure real-time control, OROCOS (Open Robot Control Middleware) and eTaSL (expression graph-based Task Specification Language) were utilized . A User In this paper, admittance and position control were used in two different situations. The admittance controller was used to interact with the user’s motion during the calibration and registration. In this mode, the user could directly grab the drilling platform attached to the robot and co-manipulate it to the desired pose. This concept was based on mechanical admittance as presented in  where thThe position control was implemented to perform the automatic positioning and drilling after the calibration. The eTaSL optimization core sent the desired joint angle A dedicated AR application was developed in Unity to establish the interface for the human–robot interaction, using a HoloLens2 HMD. This HRI was achieved by visualizing the interactive 3D AR cues, such as spheres and arrows, and a dedicated graphical user interface (GUI). The interaction was based on the built-in hand gesture and voice commands of the HoloLens, as the user could grab and manipulate the AR cues, or interact with the buttons and sliders on the AR GUI using his/her fingers. Such interaction omits the need for a physical controller, e.g., mouse, keyboard, or control panel. With the GUI, the user was able to (1) add a new entry point, (2) start/stop motion, (3) control the drill and (4) set drilling parameters, such as drilling depth and rotation speed, as shown in The desired pose of the drill tip To be able to convert the pose of the virtual arrow to the robot frame, the transformation matrix between the HoloLens coordinate frame For this, the spatial calibration in this work proposes the use of six virtual spheres that were rendered in the HoloLens scene  problem . The floUser experiments were carried out to evaluate the positioning accuracy of the AR-based robotic system involving three participants. A 3D-printed phantom was used for quantitative assessment and validation. The phantom was filled with Eco-flex with nine holes as reference drilling targets, as shown in 1.Registration of the ground truth targets in 2.Spatial calibration of HoloLens and robot, as described in 3.Positioning of the drill to the nine targets using the AR interface.Before the user experiments, the phantom During the experiments, the accuracy and performance of the proposed system were assessed. Following the calibration of the robot and HoloLens, the participants placed the virtual arrow to the targets sequentially (from Point 1 to Point 9) on the phantom and then controlled the robot to the defined target pose using the AR interface, as shown in Following the user experiments, the assessment of the system was composed of four metrics, namely (1) the accuracy of the robot–HoloLens calibration, (2) the effect of the human factor, (3) the accuracy of the overall positioning of the drill, and (4) the execution time of defining an entry point. During the evaluation of the results, the ground truth values were affected by the calibration error between the phantom and x, y, and z axes byx, y, and z axis in The accuracy of the calibration between the HoloLens and robot was assessed by transforming the six calibration points from Independently from the calibration error, the human factor error also affected the participant’s performances. This human factor error is a combination of how well the user can perceive and position the AR cues, and the influence of hardware limitations on his or her performance, such as the 3D rendering error and resolution of the HoloLens. In some cases, it was difficult to make precise adjustments to the AR-rendered objects using hand gestures, which resulted in a slight offset from the intended pose.The human factor error was evaluated based on how well the users could estimate the relative distance between the target points when setting drilling poses. Point 1 was used as the reference point and the distances to the other target points were calculated based on the set targets by the users. These distances were then compared to the ground truth distances on the phantom.z coordinates were not taken into account, as it was noticed that the users tended to place the tip of the AR arrow slightly higher than the entry point on the surface of the phantom. This behavior is also expected during surgery when the user may feel safer doing so. The resulting drill tip positions were projected along the centerline of the drill onto the surface of the phantom. The overall performance of the target pose error was evaluated based on the positioning of the AR arrows at the nine targets of the phantom. The overall target pose error was calculated as the distance between the ground truth entry point and the projected entry point on this 2D plane usingx and y coordinates. To evaluate the orientation, the error was calculated between the measured and the reference Euler angles. The estimation of the correct angle was assessed by comparing the resulting orientation to the ground truth and calculating the error in the Euler angle about the x axis.When evaluating the positioning accuracy of the system, the d is the depth of the phantom, x axis, about which the targets were rotated, and Furthermore, after defining the pose of the entry point and moving the robot using the AR interface, the user drilled through the phantom. The pose error was also evaluated based on the distance error on the bottom surface of the phantom, called the drill target error asBesides the positioning accuracy, the execution time was also assessed, by measuring the time it took to define the entry point. Before each target, the AR arrow was moved ±500 mm above the phantom. When positioning the arrow, the time was measured between grabbing the arrow and the time when the arrow was considered as correctly placed at the entry point.z axis. In all other cases, the maximum errors were within 4 mm. The normalized mean error Three users with little experience with AR participated in the experiments. x axis. Therefore, the rotation errors were only calculated about the x axis and are summarized in To evaluate the human factor error and the consistency of the users, the distances between the indicated entry points were calculated with respect to Point 1. The final target pose errors consisting of the position and the angular accuracy during the user experiments are summarized in In this paper, an AR-based robot control scheme was developed for pedicle screw placement. The objective of the proposed approach was to simplify the complex robot control in spine surgery for clinical users and to allow a fast way for intra-operative adjustment of the surgical plan based on the updated patient anatomy or position. The system consists of a robotic arm, a HoloLens for AR visualization and interaction, and a PC for communication and control. The system was evaluated via a user study, where three participants executed a positioning task by placing a virtual arrow on a silicon phantom to define the drill tip pose at nine pre-defined reference entry points. The mean distance and the rotation error from the ground truth points for the three users were 3.05 mm and 2.15i et al. , who desAs the normalized mean calibration errors showed, there was almost a 3 mm difference between User 3 and User 2, who performed the best and the worst, respectively. The users attempted to precisely align the tip of the drill with the center of the virtual spheres, though having limited experience with the HoloLens. When the user moved his/her head, the AR spheres in the 3D hologram slightly moved as they were re-rendered for the new viewpoint. This movement of the holograms made it challenging to perfectly align the real and virtual points in 3D space. Guo et al.  proposedrding to .x axis with respect to Point 1. The larger the distance was from the reference, the larger the error became, except in Point 4, where the mean error was x axis for the human factor error as the entry points on the phantom were only rotated about the local x axis. However, the phantom was not perfectly aligned with the robot frame, thus a more thorough evaluation of the drilling target pose error would be worthwhile.When positioning the AR arrow to define the entry point for the drill, besides the calibration error, the human factor also affected the overall performance. This human factor error depends on the user’s assessment of the correct pose in 3D. Furthermore, the HoloLens was still tracking hand gestures when the user wanted to release the arrow. This resulted in slight movements away from the intended point. The human factor error was evaluated based on the consistency of positioning, by analyzing the translation and rotation error between the entry points. This factor was independent of the calibration error as the relative distances and rotations were measured. As After defining the pose at the entry point and positioning the robot using the AR interface, the drilling through the phantom was performed and the error on the bottom surface of the phantom, called drill target error was assessed. This drill target error was the combination of the entry point error and the rotation error. Due to the rotation component, the error was expected to increase with increasing depth. Therefore, besides evaluating the error for the 30 mm depth of the phantom, y axis and only wanted to adjust the tip position along the x axis.The AR interaction was based on hand gestures and voice commands, where the user could set drilling parameters and move the robot using a dedicated GUI, and place a virtual arrow to define the drill tip pose. To improve the positioning, the user could lock 5 DOF out of the total 6, thus, only manipulating the remaining free DOF, e.g., translate along a single axis or rotate about a single axis. This was beneficial, e.g., when the user assessed the correct position along the In this paper, only a user study was conducted to assess its technical feasibility, its system accuracy, and related errors. This work has several limitations. First, only three users participated with no medical background due to limited time and access to clinical partners. Second, the current laboratory setting is a rather optimal condition when compared to that of in the OR. Based on the experience, with uniform background, the accuracy of depth drops. Since the current work proposes the technical feasibility of such AR-based HRI, the evaluation was carried out in an ideal (less uniform and dynamic) environment than an operating room. Therefore, before deploying to the OR, the experimental assessments of the system with a cohort of subjects, including clinicians, are foreseen in the future study and a simulated OR environment. The accuracy of the positioning might be negatively affected by non-ideal circumstances. Furthermore, while the spatial calibration without an external tracking device seems promising, it is also user-specific as it depends on how precisely the user aligns the drill tip with the calibration spheres. Further methods could be considered in the future that might also be easier to perform in the OR, for example, a quick bootstrap procedure to complete the calibration step. Lastly, the overall ergonomics of the system were not assessed, as it was out of the scope of this research. However, it is important to note that wearing the HoloLens for a longer time and working at relatively close distances might introduce fatigue and eye strain for the user. This will require a usability study focusing on subjective evaluation. In addition, besides defining the pose of the entry point and analyzing its accuracy, further evaluation would be directed to analyze drilling trajectory accuracy on the bony tissue from a cadaver or animal models.In summary, the developed system offers an intuitive interaction between the surgeon and surgical robot when performing surgical actions, e.g., pedicle screw placement and intra-operative surgical plan adjustment. The surgical plan can be made and adjusted by a surgeon on-site. Meanwhile, thanks to the real-time interaction, any changes made by the surgeon in AR can be immediately mapped to the robot side for execution. Such a promising augmented reality-based robot control scheme has great potential to change the paradigm of means of the controlling surgical robot for the end users. A major advantage of the proposed system is that no external tracking device was used to calibrate the system to find the transformation matrix between the HoloLens and the robot frame. In cases of external optical trackers, occlusions of the visual markers interrupt the operation. This can occur in a crowded OR. The proposed system eliminates this risk of occlusions. Furthermore, this simplifies the overall system that needs to be introduced in an operating room. The experiments showed that the readjustment of the position of the arrows took 26.56 s on average in a free-touch fashion. This allows a fast intra-operative update of the surgical plan and positioning of the robot to the desired pose. The overall position error might not be adequate for direct AR-based robotic-assisted PSP due to the positioning errors measured. However, the entry point could be fine-tuned by a vision-based system that identifies the anatomic landmarks. Such fast positioning of the pedicle screw to the region of interest could further enhance the performance of robotic-assisted PSP and reduce the operation time. Consequently, the proposed system would establish a new approach to the AR–robot interaction for medical applications in the OR.


This work analyzed the use of Microsoft HoloLens 2 in orthopedic oncological surgeries and compares it to its predecessor (Microsoft HoloLens 1). Specifically, we developed two equivalent applications, one for each device, and evaluated the augmented reality (AR) projection accuracy in an experimental scenario using phantoms based on two patients. We achieved automatic registration between virtual and real worlds using patient-specific surgical guides on each phantom. They contained a small adaptor for a 3D-printed AR marker, the characteristic patterns of which were easily recognized using both Microsoft HoloLens devices. The newest model improved the AR projection accuracy by almost 25%, and both of them yielded an RMSE below 3 mm. After ascertaining the enhancement of the second model in this aspect, we went a step further with Microsoft HoloLens 2 and tested it during the surgical intervention of one of the patients. During this experience, we collected the surgeons’ feedback in terms of comfortability, usability, and ergonomics. Our goal was to estimate whether the improved technical features of the newest model facilitate its implementation in actual surgical scenarios. All of the results point to Microsoft HoloLens 2 being better in all the aspects affecting surgical interventions and support its use in future experiences. Augmented reality (AR) superimposes computer-generated 3D virtual models to physical objects in real space, enabling users to interact with both worlds simultaneously . This toMixed reality (MR) is another type of display technology, together with AR and virtual reality (VR). The latter is out of the scope of this work because it completely immerses the users in a virtual environment, making them blind to their surroundings . Hence, One of the major problems associated with this technology is finding the appropriate transformations to align the displayed objects and the physical world ,14. In mAR can be deployed on universal devices, such as smartphones  or tableAccording to this, the purpose of our work is threefold. The first is to compare Microsoft HoloLens 1 and Microsoft HoloLens 2 for surgical guidance in orthopedic oncology. We selected these devices because they have already demonstrated their excellence in many clinical applications, including the one we are interested in ,25. Our Our second goal was to further analyze the Microsoft HoloLens 2 AR projection accuracy. With this purpose, we developed a new experimental scenario based on a patient with an undifferentiated pleomorphic sarcoma on the right shoulder. We 3D printed a larger phantom based on this patient and followed the same procedure as in  to analyThe ultimate objective was to test the usability of the newest device in actual surgical scenarios. With this intention, we tested the newest device during the surgical intervention of the second patient and evaluated some of the technical aspects that mainly affected this clinical context: adjustment, intuitiveness, comfortability, and ergonomics. We achieved automatic registration between real and virtual worlds with a 3D-printed, pattern-based marker in all the cases. To sum up, this work determined whether Microsoft HoloLens 2 improves the results presented in  with MicThe data for this study were obtained from two patients treated at the Department of Orthopedic Surgery and Traumatology at Hospital General Universitario Gregorio Marañón (HGUGM) in Madrid. The analysis was performed under the principles of the 1975 Declaration of Helsinki, as revised in 2013 and approved by the Research Ethics Committee at HGUGM, and after obtaining written informed consent from the participants and/or their legal representative. Both patients were assigned an alphanumeric code to preserve their anonymity: HL1HL2_Leg and HL2_Shoulder. 2). This marker contained a specific pattern in black and white which the AR system could easily recognize. We designed the position of the surgical guide (and the marker within it) in direct coordination with the surgeons considering the surgical approach. By doing so, we could guarantee these elements did not disturb the surgeon’s gaze during the interventions.We developed two 3D patient-specific phantoms from patient CT data, following the steps presented in  and summThe phantoms, surgical guides, and the AR marker for the experimental scenario were 3D printed in PLA with fused deposition modeling (FDM) using a double extruder desktop 3D printer Ultimaker 3 Extended . To evaluate Microsoft HoloLens 2 during the surgical procedure of patient HL2_Shoulder, we 3D printed a surgical guide in BioMed Clear V1 resin material (Formlabds Inc.) using a stereolithography 3D printer Form 2 . This material is USP class IV certified and can be in direct contact with the patient organs for long periods of time . The surhttps://github.com/Microsoft/MixedRealityToolkit-Unity, accessed on 28 February 2022) library. We developed the Microsoft HoloLens 1 AR application on Unity 2017.4 LTS (as presented in ) and useEven though Microsoft HoloLens incorporates an internal system to track the environment via spatial mapping, this feature could not be used in this study for two main reasons. First, the tracking accuracy achieved with this system ranges from several millimeters to more than one centimeter . This raThe virtual projected models were the anatomical structures of the patients (tumor and surrounding bone), the surgical guides, and the AR marker silhouette . To measWe measured the AR projection error as described in . First, Each user performed this process three times, removing and replacing the AR marker between repetitions. We decided to use the same number of users to perform this experiment as in , as wellWe compared the technical aspects of Microsoft HoloLens 1 and Microsoft HoloLens 2 which mainly affected our specific surgical application  and evaluated them for orthopedic oncological surgeries. To perform this evaluation, we created a survey in which users who had tried both models in this clinical context had to rate these features on a scale from 1 (terrible) to 5 (perfect). We based our survey on other studies which created similar questionnaires to evaluate their systems, such as ,33,34. TIn addition to evaluating the AR projection accuracy, we considered measuring the usability of Microsoft HoloLens 2 in actual surgical scenarios to be of great importance. Our goal was to analyze the glasses in terms of comfortability and ergonomics, considering the long duration of these surgical interventions. For this reason, we tested the Microsoft HoloLens 2 app during patient HL2_Shoulder’s surgery and evaluated the overall experience. The orthopedic surgeon put on the Microsoft HoloLens 2 before starting the intervention and raised the visor. He first performed an incision over the humerus until the bone was reached. Then, he fitted the surgical guide, fixed it with screws, and introduced the AR marker into the surgical guide socket. After that, a nurse lowered the visor on the glasses to start the augmented reality visualization. The virtual models of the tumor and the bone were automatically registered with the actual anatomical structures of the patient. The surgeon used the app buttons and sliders to tailor the visibility of each augmented model and assess the alignment of the projections. The surgery followed the pre-established surgical plan, and the tumor was completely resected. The surgical procedure continued without incidences.The Vuforia SDK detected the AR marker almost immediately in both applications. In addition, we could visually confirm a correct registration between the real and virtual world based on the good alignment of the AR marker silhouette with the actual AR marker. . In addition, To understand the discrepancy between the error obtained with Microsoft HoloLens 2 for phantoms HL1HL2_Leg and HL2_Shoulder , Finally, A video included in The surgeon gently moved the patient’s arm to guarantee that the AR marker remained fixed in the bone, checking how the virtual models followed the movement to always align with the anatomical structures. In addition, interaction on the user interface was intuitive, effective, and allowed the surgeon to accommodate the holograms’ visibility to his needs. When no longer needed, the AR marker was easily detached, and a nurse raised the Microsoft HoloLens 2 visor again to continue with the intervention. Indeed, the surgeon highly appreciated this feature because it greatly improved ergonomics. In addition, he acknowledged the lightness and comfortability of the new headset compared with its predecessor.In this work, we analyzed Microsoft HoloLens 2 improvements with respect to Microsoft HoloLens 1 in orthopedic oncology. We firstly assessed the AR projection accuracy of both devices and then compared some technical aspects, including comfortability and intuitiveness. To do so, we retrieved the data published in  which anCurrently, most studies that apply augmented reality in medicine perform a manual registration between real and virtual worlds . AlthougIn terms of the results regarding the AR projection error, the RMSE measured with Microsoft HoloLens 2 on phantom HL1HL2_Leg was almost 0.7 mm lower than with Microsoft HoloLens 1, which translated to a more accurate AR projection. The second experiment with Microsoft HoloLens 2 (on phantom HL2_Shoulder) resulted in an RMSE 1 mm larger than in the first case. This increased error is explained by the larger size and shape of the second phantom. With respect to the errors by axis, phantom HL1HL2_Leg yielded much lower error in the Z axis  than in the other two axes. This can be attributed to the short depth of this mannequin compared to the other dimensions. Concerning phantom HL2_Shoulder, there were no meaningful error differences in each axis, as the phantom size was more similar along the three dimensions. Concerning the error in each control point, we explored possible correlations between AR projection error and distance to the origin . HoweverEven so, the errors obtained in this study were much lower than the ones presented in , which pWith respect to the capabilities and technical differences, the newest device displayed great benefits compared to the first one. These results were expected considering the Microsoft HoloLens 2 technical datasheet and new features. First, even though the difference in weight is not very high (579 g in the first model versus 566 g in the second one), Microsoft HoloLens 2 relocates the battery pack on the back of the head, improving weight balance. In addition, it incorporates a dial-in fit system and a flipping visor. These highly increase the ergonomics and make the headset more comfortable for extended sessions. These two aspects were the most appreciated by the surgeon during the intervention of patient HL2_Shoulder. Regarding the visualization, the diagonal field of view of the second device (52°) highly surpasses the first one (30°). This larger value enhances the integration of the holograms in the 3D space and offers a more immersive experience. On the other hand, Microsoft HoloLens 2 greatly improves hand-gesture recognition. While Microsoft HoloLens 1 interaction was simply oriented to use the head like a mouse pointer and the finger tap gesture as the mouse button, the newer device recognizes twenty-five articulation points per hand considering wrist and fingers. This aspect permits a more intuitive interaction to grab, translate, rotate, and scale holograms. It was especially beneficial during surgical intervention for patient HL2_Shoulder, in which the surgeon could interact with the buttons’ interface as in an actual panel. Finally, Microsoft HoloLens 2 has upgraded processing power and RAM, providing a faster response speed and a more detailed experience.Once again, augmented reality has proven to be very promising in these surgical applications. AR head-mounted displays show relevant information in front of the surgeons, freeing their hands. In addition, new incorporations on Microsoft HoloLens 2 enhance device ergonomics and accuracy. Hence, it does not seem unreasonable to expect the introduction of these devices in clinical practice in the near future. Nevertheless, several aspects still have to be improved. On the one hand, Microsoft HoloLens sterilization is still not possible, so surgeons cannot touch the glasses at any point during the intervention. In addition, our solution relies on solid structures  to hold the surgical guides, so it cannot yet be directly extrapolated to surgeries only involving soft tissues. To finish, the AR marker detection is continuous, so the marker must be visible at all times, which might be inconvenient at some points. To overcome this limitation, we assigned different colors to the augmented AR marker silhouette according to the tracking state. These colors were green when the AR marker was visible and red when the tracking was lost. In the latter case, the virtual models remained in the last place the tracker was detected. Hence, the surgeon could always see the models, but he had a warning to see the reliability of the projection in real time. All of this was reflected in the surgeon’s positive feedback during the surgical experience.This work analyzed the improvements in Microsoft HoloLens 2 over Microsoft HoloLens 1 in terms of AR projection accuracy. To do so, we developed an AR application for Microsoft HoloLens 2 based on the one presented in  and usedThen, we developed a larger patient-specific, 3D-printed phantom to further analyze Microsoft HoloLens 2’s AR projection accuracy. In addition, we tested the newest device during the surgical intervention of the second patient. During this, we evaluated the technical aspects that mainly affect this clinical application. These include adjustment, hologram quality and interaction, and hand recognition. All of the procedures were based on patient-specific surgical guides and an AR marker containing easy-to-identify patterns which was detected using Vuforia SDK. To our knowledge, this is the best option for automatic registration and clearly recommends Microsoft HoloLens 2 rather than Microsoft HoloLens 1 in clinical interventions. We hope this work helps others decide which device to use in similar applications and that it establishes the basis for future studies of augmented reality in this clinical context.


There is a tremendous scope of hardware and software development going on in augmented reality (AR), also in trauma and orthopaedic surgery. However, there are only a few systems available for intra-operative 3D imaging and guidance, most of them rely on peri- and intra-operative X-ray imaging. Especially in complex situations such as pelvic surgery or multifragmentary multilevel fractures, intra-operative 3D imaging and implant tracking systems have proven to be of great advantage for the outcome of the surgery and can help reduce X-ray exposure, at least for the surgical team . Yet, the current systems do not provide the ability to have a dynamic live view from the perspective of the surgeon. Our study describes a prototype AR-based system for live tracking which does not rely on X-rays.A protype live-view intra-operative guidance system using an AR head-mounted device (HMD) was developed and tested on the implantation of a medullary nail in a tibia fracture model. Software algorithms that allow live view and tracking of the implant, fracture fragments and soft tissue without the intra-operative use of X-rays were derived.The implantation of a medullar tibia nail is possible while only relying on AR-guidance and live view without the intra-operative use of X-rays.The current paper describes a feasibility study with a prototype of an intra-operative dynamic live tracking and imaging system that does not require intra-operative use of X-rays and dynamically adjust to the perspective of the surgeons due to an AR HMD. To our knowledge, the current literature does not describe any similar systems. This could be the next step in surgical imaging and education and a promising way to improve patient care. There is a tremendous scope of hardware and software development going on in augmented reality (AR). This development also spreads into medicine; however, there are only a few established applications in use so far, especially as for trauma surgery. This also applies to intra-operative imaging and guidance. There are some systems available for intra-operative 3D imaging and guidance, most of them rely on peri- or intra-operative imaging deploying X-rays. Trauma surgeons are often faced with complex situations which arise intra-operatively, might it be in emergency procedures or complex elective cases. Especially in these complex situations such as pelvic surgery or multifragmentary multilevel fractures, intra-operative 3D imaging and implant tracking systems have proven to be of great advantage for the outcome of the surgery and can help reduce X-ray exposure, at least for the surgical team . MoreoveTo our mind, intra-operative AR-enhanced imaging using overlays of pre-operatively gathered CT or MRI scans on to the site greatly improves the knowledge of the orientation of the different fragments and the implant. This can lead to reduced X-ray exposure and faster procedures with better results.The aim of this study was to develop a system that allows an intra-operative overlay of different layers of the site starting with the skin up to the bone using a head mounted display at the example of closed reduction and nailing of a tibial fracture. Moreover, we examined if AR technologies can help to make surgical procedures safer and deepen the understanding of different intra-operative situations. We wanted to investigate if an AR device can be used under real-world conditions in the OR and be controlled with a virtual user interface while wearing sterile surgical gloves. Moreover, we wanted to examine if closed reduction and implant placement is possible without the use of X-rays just relying on the AR guidance und real-world conditions in the OR using a realistic sawbone model.For the prototype, we used the latest generation AR-HMD of Microsoft’s HoloLens . This device fulfills all the stated prerequisites. The conceptual idea and as well as the model were developed by the authors, additional coding support was provided by AmbiGate Motion Sensing GmbH, Tuebingen, Germany. First of all, a model consisting of an artificial tibia bone with a multifragmentary fracture and artificial soft tissue  forming a model of a lower leg was fitted with an external fixator .Tibia fractures are rather common and closed reduction and nail osteosyntheses is an established treatment .The successful treatment depends on the exact entry point and correct reposition as well as axis reconstruction .Closed reduction and insertion of the nail into the core canal of the distal fragment can be quite demanding and require several tries and multiple X-ray images resulting in a high X-ray exposure for the surgical team and patient .The tibia fracture was chosen for the following reasons:The AR glasses must not disturb or restrict the surgeon.Sterility must absolutely be guaranteed.The system must be easy to use with a clean user interface (UI).Direct visualization of the positional relation of the different fragments with high precision and low latency of the overlay CT/MRI data.The system must allow customizable 3D visualization with adjustable views as for zoom, rotation, position, and transparency.The surgeon should be able to select different layers of the segmented CT/MRI.Simultaneous view of the AR Phantom with bone and implant overlayed on the site.Live view of the reduction of the bone fragments.Implementation of recording and casting functions .In this situation, the AR augmented live tracking can provide significant advantages. To be able to use this technique intra-operatively, we defined the following prerequisites:This model see Fig.  was thenTibia nailAiming armExternal fixatorSoft tissues and skinBoneThese data were than segmented using Mimics Innovation suite . This provided separate high-quality three-dimensional image of all relevant structures:In order to project the data on the site, a user interface (UI) was developed which allow to live-visualize the implantation of the tibia nail as a hologram of the segmented data in all planes in space. Figure Use of the system under real life conditions in the operating room: The phantom was placed on an operating table, sterile draping was applied after disinfection, sterile surgical gowns were used to assess the impact of the AR-HMD on the surgeon and to test operationality of the system and the UI.The quality of the reduction and the implant position were visually assessed using a medial incision on the model Fig. .Closed reduction and nail insertion relying only on the AR-HMD were tested.The accuracy of the overlay was evaluated.The usability and operationality of the system regarding OR lighting conditions.With the prototype finished to the abovementioned specifications, the following scenarios were tested in the OR using the phantom:The tests were performed by four surgeons in a set of 5 runs a day using a rotation system so that each surgeon had a break between the individual implantations to reduce a habituation effect. Altogether, 40 runs were performed. Figures While using the prototype under OR conditions, the user interface (UI) was easy and comfortable to use with an intuitive control set.The correct insertion of the nail into the tibia using only AR guidance was achieved reproducibly. In all 40 test implantations, a correct implant position with an anatomical reduction was achieved relying only on the AR navigation Fig. .Fig. 6MeThe system showed some deviation of the overlay of the phantom to the site under severe head movements of the surgeons, these could be corrected by recalibrating the system intra-operatively by scanning the QR codes.The three-dimensional visualization and overlays were deemed excellent by all four users. All four users stated that the AR-augmented visualization delivered valuable information and facilitated the process. Figure None of the test users found the system to negatively affect the surgeon’s comfort, sterility, or liberty of movement.The visualization options were assessed excellent by the test users. However, during test implantation, several cases of loss of the tracking of the nail occurred. This happened when the QR codes of the aiming arm disappeared from the field of view and is attributed to the movement of the head of the surgeon.The changing lighting conditions in the OR with high contrast scenarios did not cause any problems; however, two cases of reduced picture quality of the HMD were reported when the HMD was in the direct ray of light of a surgical light.Last, the added functionality of showing the virtual OP Site of the phantom in any random position in space with any zoom level as a hologram was tested. This functionality was assessed as very useful by three surgeons, one surgeon assessed it as useful.Due to the wireless construction of the HMD, sterility was not compromised in the usage scenario. The tracking of the surgeon’s hand and the operation of the virtual user interface were not negatively affected using sterile surgical gloves.The AR glasses must not disturb or restrict the surgeon.Sterility must absolutely be guaranteed.The system must be easy to use with a clean user interface (UI).Direct visualization of the positional relation of the different fragments with high precision and low latency of the overlay CT/MRI data.The system must allow customizable 3D visualization with adjustable views as for zoom, rotation, position, and transparency.The surgeon should be able to select different layers of the segmented CT/MRI.Simultaneous view of the AR Phantom with bone and implant overlayed on the site.Live view of the reduction of the bone fragments.Implementation of recording and casting functions .To check how easy and intuitively the system is operable, we defined the core prerequisites:All of the abovementioned prerequisites were met with the exemption of prerequisite 4: several loss of tracking incidences occurred under severe head movements of the surgeon and precision of the overlay was reduced during very fast head movements.Up to date, to our knowledge, no other comparable feasibility study for the AR guided implantation of a tibia nail in a real-world scenario , 6, 7 alHybrid models such as the integration of C-Arm images and sonographically acquired images have been tried as well: Hajek et al. have used a HoloLens and a C-Arm for percutaneous interventions . Heide eAll these findings concur with our findings showing that a high level of precision can be reached with AR-guided implant placement, even without the use of X-rays.So far, we can conclude that there are several approaches to the use of AR in surgery. These approaches are on different evolutional levels. The described prototype opens a new perspective by using AR to guide the implantation of a tibia nail without the intra-operative use of X-ray.To our opinion, a key factor for clinical use of AR technology in the OR is the ease of use. The described prototype was easy to use for all testers. One future development should be the implementation of smaller QR markers or even a markerless system—further development is necessary. Further use-scenarios can be found in endoprosthetics, e.g., for planning and live-tracking of component placement. Reliable results for placement of the acetabular component have already been found by Ogawa . FurtherThe benefit of being able to intra-operatively adjust the views as for angle and zoom as well as other parameters was already shown by Gregory et al. when overlaying a CT scan and a three-dimensional planning sketch during implantation of an inverse shoulder prothesis . Ochs anWe found a high level of precision of the AR device which enabled us to precisely implant a tibia nail. However, there were some limitations: There were some cases of loss of tracking. We attribute this to a to some extent limited angle of view of the built-in cameras of the HMD. The limited field of view of the built in-cameras also limited the ability of the system to recognize hand gestures. Future technological development will probably also address this. Another limitation of our system is the need to mark all the relevant surfaces with QR markers. So far, all other systems described used some way of markers as well, another way is using a pattern of reflective cue points. Our focus right now lies on the development of a markerless system with enhanced precision. For clinical use in humans, the use of a backup X-ray system to verify implant positions seems inevitable at the current point. The future aim is a system that can be used as standalone device without intra-operative X-ray; this would not only reduce X-ray exposure for the patient and the surgical team but also the number of devices required in the OR.2 is in development.A markerless system would also allow to overcome another limitation of the present system: not all boney fragments were marked and thus not live tracked during surgery. In our model, all major fragments were tracked with the attached external fixator. A system which will be able to track at least all fragments bigger than 1 cmIn our opinion, the presented system provides possibilities of intra-operative planning and step by step verification that is unpreceded; also, there are some limitations which have to be tackled in future development.The current paper describes a feasibility study with a prototype of an intra-operative dynamic live tracking and imaging system that does not require intra-operative use of X-rays and dynamically adjust to the perspective of the surgeons due to an AR head-mounted display (HMD). To our knowledge, this is the first description of such a system. Our study showed that that the implantation of a tibia nail in a real-life model is possible relying only on AR guidance. Excellent visualization of the pre-operatively gained image data was shown, the ability to free rotate the hologram in physical space and to zoom as well as the precise overlay onto the surgical site were highly rated.We could prove that AR guidance works under real-life conditions in the OR without compromising sterility and that the system was easy to use even when sterilely dressed. Further development should improve precision and the ability to track small boney fragments. The development and use of hybrid models should be examined in further studies.


Looking back to the roots of modern Rehabilitation Medicine, 3 main streams can be identified.the First and Second World Wars in central Europe or the Vietnam War in The US)  . However The US) .The second stream consists of care programs for children with congenital disabilities, namely deformities in the musculoskeletal system. This type of care dynamically developed in the Nineteenth century . Though The third stream originates from the tradition of health resort medicine and treatment concepts that use balneological and physical modalities . These tcute, post-acute, and long-term care) and at all levels  of health care , the (synergistic) effects of combined treatments, and the duration of rehabilitation interventions. Additionally, knowledge of predictors, age- and gender-specific effects, and the adherence of effects need further elucidation.Mental disorders, including depression and anxiety, are frequent health conditions and have a high impact on participation in society and vocational performance , 14. Perwith the possible exceptions of cerebral palsy and juvenile rheumatoid arthritis). The gaps are obvious when looking at children with cancer and mental disorders  (Another recent topic for rehabilitation medicine research is long-term impairment following SARS-CoV-2 infection (VID-19”) . BesidesVID-19”) . In prinOther conditions as well as rehabilitation of persons with multimorbidity, rehabilitation for old people and patients with different types of cancer could have been taken as examples.With regard to mechanisms, the knowledge on neuroplasticity and brain repair, training of muscle functions, and influence on tropho-trophic tissues of the musculoskeletal system as well on cardiovascular, respiratory, and metabolic functions and its relevance for rehabilitation approaches have grown dramatically during the last decades; other pathophysiological and repair mechanisms have received much less attention. Examples for this are possible influences on the biomolecular mechanisms of wound healing, mechanisms of pain chronification, and the immune response.Another issue is that rehabilitation research—similar to the implementation of rehabilitation programs—focuses on the most frequent health conditions, such as back pain, osteoarthritis, diabetes, COPD, myocardial infarction, etc. The development of rehabilitation programs for rare diseases and the research about it is extremely scarce. From an ethical perspective and with regard to scientific relevance, this should be changed , and resThe abovementioned examples demonstrate that the field of medical and surgical rehabilitation needs much more attention in research. To conceptualize such fields, more systematic consideration is needed.For efficient rehabilitation, goal setting has an important role . For a sIn many clinical fields, the treatment strategies and intervention emerge very dynamically. This is the case for surgical techniques, pharmacological treatments, and cognitive-behavioral approaches. It is extremely important to investigate how this influences rehabilitation strategies and—on the other hand—how rehabilitation needs may be modified. Some examples for that are the implementation of endo-exo-prothesis after limb amputation, biologicals in the treatment of rheumatoid arthritis, organ transplantation surgery, and others. Furthermore, rehabilitation technology and assistive devices as well as robotics and it-approaches are developing fast. Both aspects must be considered in designing rehabilitation approaches and must be investigated in clinical trials.including post-treatment phase), infectious diseases, musculoskeletal pain disorders, metabolic disorders, and others. Recently, it has been described that post-COVID-19 syndrome to a high extent also includes suchs symptoms (in cancer) and mediators  are involved .Last but not least the organization of rehabilitation services and their interfaces with other health services may significantly influence service quality and outcomes . Here, iAll in all, it can be seen that the whole spectrum of rehabilitation research “from cell to society”  is of reThe author confirms being the sole contributor of this work and has approved it for publication.The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Revision total knee replacement (TKR) is a major operation with a long recovery period and many patients report suboptimal outcomes. Rehabilitation has the potential to improve outcomes. The aim of this study was to understand current provision of rehabilitation for revision TKR in England and evaluate the existing evidence.Phase 1: An online national survey of education and rehabilitation provision for patients receiving revision TKR was completed by physiotherapy staff at 22 hospitals across England that were high volume for revision TKR (response rate of 34%).Phase 2: Systematic review to identify studies evaluating rehabilitation programmes for revision joint replacement. Searches were conducted in MEDLINE, EMBASE, PsycINFO, CINAHL, and Cochrane databases from inception to 15th June 2022. Randomised controlled trials (RCTs) and observational studies that evaluated post-operative rehabilitation for adults undergoing revision joint replacement were included. Screening, data extraction and quality assessment was undertaken by two reviewers.Phase 1: Pre-operative education which aimed to prepare patients for surgery and recovery was provided in most hospitals, predominately involving a single session delivered by a multidisciplinary team. Inpatient physiotherapy commonly commenced on post-operative day 1 and was provided twice daily, with most hospitals also providing occupational therapy. Rehabilitation was often provided in the first four weeks after hospital discharge, either in an outpatient, community or home setting. In most hospitals, the education and rehabilitation provided to patients receiving revision TKR was the same as that provided to patients undergoing primary TKR.Phase 2: Of the 1,445 articles identified, three retrospective cohort studies based on hospital records review were included. The studies evaluated intensive inpatient rehabilitation programmes, consisting of 2–3 h of daily group or individual physiotherapy, with additional occupational therapy in one study. All three studies reported improvement in functional outcomes for patients undergoing rehabilitation after revision TKR. All studies were limited by their retrospective design, short duration of follow-up and lack of sample size calculation. No RCTs evaluating effectiveness of rehabilitation for revision TKR were identified.This study identified the need for future research to develop and evaluate tailored rehabilitation to optimise patient outcomes following revision TKR.The online version contains supplementary material available at 10.1186/s12891-023-06196-1. Over 100,000 primary total knee replacements (TKRs) are performed annually in the United Kingdom . The aimPatients often have high expectations of their outcomes after revision TKR , howeverPhysiotherapy, either provided alone or as part of a multidisciplinary rehabilitation package, can be provided to patients with the goal of facilitating functional recovery and improving outcomes after joint replacement. Current British Orthopaedic Surgery Standards for Trauma and Orthopaedics on revision TKR do not include guidance on rehabilitation provision . RehabilThe aim of our study was to scope current service provision and the existing evidence base for rehabilitation after revision TKR to identify if there is the need for future intervention development work. Specific objectives of the study were to 1.) gather information on current rehabilitation service provision for patients undergoing revision TKR in England using a national survey and 2.) conduct a systematic review of research evaluating rehabilitation interventions and outcomes following revision joint replacement.This was a 2-part study, with phase 1 comprising a national survey of rehabilitation provision for revision TKR and phase 2 comprising a systematic review of existing literature evaluating rehabilitation after revision joint replacement.www.onlinesurveys.ac.uk), consisted of 27 questions which were developed by the research team, informed by previous national surveys of rehabilitation services for primary TKR [The 100 highest-volume National Health Service (NHS) hospitals for revision TKR surgery in 2019 were identified from the National Joint Registry in February 2022 [mary TKR  and revimary TKR . The surSurvey responses were exported into Microsoft Excel. Frequency statistics were used to analyse categorical data. Free-text variables were reviewed and coded into categories by two authors, and a descriptive summary of service provision developed. The project was conducted as a Clinical Effectiveness project, with approval from the North Bristol Trust NHS Quality Governance Team (reference CE97788).The systematic review protocol was prospectively registered on PROSPERO (CRD42022340099) and reporting follows MOOSE guidance . Althougth June 2022. No restrictions were placed on study design or language. The searches combined free and MeSH search terms and combination of key words related to rehabilitation  and revision joint replacement. Reference lists of retrieved articles were manually scanned for all relevant additional studies and review articles. Further details of the search strategies and terms are provided in the online Searches were conducted in MEDLINE, EMBASE, PsycINFO, CINAHL, and Cochrane databases from inception to 15Studies were included if they evaluated post-operative rehabilitation interventions for adults undergoing revision joint replacement for any indication. All types of revision joint replacement operations were included to maximise the number of studies included in the review. The main outcomes of interest were joint pain and joint function. Eligible study designs included randomised controlled trials and observational studies . Studies that included both primary and revision joint replacement patients were eligible for inclusion if they reported results separately for patients undergoing revision joint replacement. Conference abstracts and theses were excluded.After removal of duplicates in Endnote, study records identified in the searches were imported into Excel for screening. Titles and abstracts were screened to remove clearly irrelevant articles. Detailed screening of potentially relevant articles was then conducted independently by two reviewers (IO and VW) to identify eligible studies for inclusion in the review.Data extraction was conducted by one reviewer and checked by a second reviewer. Data were extracted on study design, publication date, geographical location, participant demographics and surgical details, duration of follow-up, sample size, intervention content and timing, outcomes, results and information for assessment of study quality.For studies with a cohort design, it was planned that methodological quality would be assessed using the Methodological Index for Non-Randomised Studies (MINORS) instrument . MINORs 2 statistic.At protocol stage, meta-analysis was planned if two or more studies were identified with similar rehabilitation programmes and appropriate outcome data. Risk estimates (risk ratios for cohort studies and odds ratios for case–control) and/or mean differences would be used as the common measure of association across studies. Risk estimates would be calculated for studies that reported raw counts. When reported risk estimates could not be calculated, we planned to obtain the relevant estimates through correspondence with the study authors. The inverse variance weighted method would be used to combine summary measures using random-effects models to minimise the effect of between-study heterogeneity. Heterogeneity would be assessed using the IA meta-analysis was not possible due to the limited number of studies and therefore a narrative synthesis was conducted, with the findings of each study summarised in tables and described in a narrative format.Of the 100 highest-volume NHS hospitals for revision TKR, e-mail addresses were identified for 65 hospitals. An invitation e-mail containing the link to the online survey was sent to a named contact or department e-mail address at the 65 hospitals in March 2022. Of these, 24 physiotherapy staff at 22 hospitals (34%) completed the survey. Respondents were based in NHS hospitals across England, including the South East (10), South West (6), North East (3), North West (1), East Midlands (1) and West Midlands (1).n = 16) of the responding hospitals and details are provided in Table Pre-operative education was provided at 73% n = 6 of the Details of post-operative inpatient rehabilitation are provided in Table All hospitals provided post-discharge rehabilitation, either to all patients or to patients with poor mobility or range of motion Table . The posAfter removal of duplicates, searches identified 1,445 study records. After initial screening, 22 articles were identified as potentially relevant and screened in detail. Of these, three met the inclusion criteria and were included in the review –20 (Fig.Larsen et al. report a retrospective hospital register-based study of 51 patients with complications after revision TKR admitted to an inpatient rehabilitation hospital in Denmark between 2017 and 2018 . In the All three studies evaluated intensive rehabilitation programmes delivered in an inpatient hospital setting. The rehabilitation programmes consisted of 2–3 h of daily supervised group or individual physiotherapy, with additional occupational therapy in one study . One stuAll three studies evaluated patients on admission and discharge to the rehabilitation programme. All assessed patient-reported outcomes; Larsen et al. used the Knee injury and Osteoarthritis Outcome Score and a pain Numeric Rating Scale and both Vincent et al. and Walker et al. used the Functional Independence Measure. Additional, Larsen and colleagues assessed objective measures of functional ability including the 6-min walk test, stair climb test and knee range of motion. All three studies demonstrated improvements in these outcomes from admission to discharge from the rehabilitation hospital.This article reports on a national survey and systematic review to understand current service provision in England and the existing evidence-base for physiotherapy after revision TKR. The national survey found that most responding NHS hospitals provided patients undergoing revision TKR with pre-operative education, inpatient rehabilitation and outpatient rehabilitation after hospital discharge. However, the education and rehabilitation provided to patients following revision TKR was the same as that provided to patients undergoing primary TKR, suggesting that neither are tailored to the needs of patients recovering from revision TKR. The systematic review identified an important gap in the existing literature regarding rehabilitation after revision TKR, with only three published studies evaluating patient outcomes after rehabilitation following revision joint replacement. Narrative synthesis suggests that intensive, inpatient rehabilitation programmes have the potential to improve short-term patient outcomes after revision joint replacement. However, the conclusions that can be drawn from the narrative synthesis are very limited as it was based on a small number of retrospective observational studies. Due to the lack of randomised controlled trials, no inferences can be made about the effectiveness of rehabilitation for patients undergoing revision TKR.There are a number of strengths and limitations of this research that need to be considered when interpreting the findings. Although we obtained a good geographic spread of hospitals in our national survey, the response rate of 34% was lower than previous surveys, despite using established procedures , 21. AltWe identified a paucity of research evaluating the impact of rehabilitation interventions on pain and function following revision TKR. A number of systematic reviews of randomised controlled trials evaluating rehabilitation for primary TKR have been conducted, with the general consensus that physiotherapy is effective at improving short-term outcomes, although optimising format and content require further investigation , 23. In Our results highlight a paucity of research to guide the provision of evidence-based tailored rehabilitation for patients undergoing revision TKR. Surgical treatment of major adverse occurrences after primary TKR poses a major burden to patients and the NHS. There is a clear and pressing need for co-interventions to optimise outcomes after surgery and support patients through treatment and recovery. Tailored rehabilitation, within a broader integrated care pathway to address the physical, psychological, emotional, and social needs of patients undergoing revision TKR, could support patients through their treatment journey. Development of novel and individualised rehabilitation programmes would benefit from a co-production approach with key stakeholders, including patients, and use of a relevant theoretical framework to support behaviour change. Evaluation of such interventions would need to be within the framework of a multicentre randomised controlled trial, with longer-term follow-up, cost-effectiveness analysis, and assessment of outcomes that are important and meaningful to patients. Understanding how to measure outcomes following revision TKR in a way that is meaningful to patients is a top 10 research priority in the James Lind Priority Setting Partnership for revision knee replacement , and furAdditional file 1.