Reproducibly achieving proper implant alignment is a critical step in total hip arthroplasty procedures that has been shown to substantially affect patient outcome. In current practice, correct alignment of the acetabular cup is verified in C-arm x-ray images that are acquired in an anterior–posterior (AP) view. Favorable surgical outcome is, therefore, heavily dependent on the surgeon’s experience in understanding the 3-D orientation of a hemispheric implant from 2-D AP projection images. This work proposes an easy to use intraoperative component planning system based on two C-arm x-ray images that are combined with 3-D augmented reality (AR) visualization that simplifies impactor and cup placement according to the planning by providing a real-time RGBD data overlay. We evaluate the feasibility of our system in a user study comprising four orthopedic surgeons at the Johns Hopkins Hospital and report errors in translation, anteversion, and abduction as low as 1.98 mm, 1.10 deg, and 0.53 deg, respectively. The promising performance of this AR solution shows that deploying this system could eliminate the need for excessive radiation, simplify the intervention, and enable reproducibly accurate placement of acetabular implants.
 Abstract We prospectively evaluated acetabular cup placement in total hip arthroplasty with an imageless computer navigation system or using conventional manual technique. The achieved cup orientation in the manual group had substantially larger variances and greater placement error than the navigation cases. The use of navigation was abandoned in 3 cases because of excessive pelvic tilt and unreliable registration of the pelvis. Computer navigation system helped improve the accuracy of the acetabular cup placement for total hip arthroplasty in this study. The variation between the intraoperative navigation readings and the computed tomographic values suggests that relying on palpation of bony landmarks through drapes and tissue is a limitation of this method. Further, the variation in pelvic tilt has an effect on cup placement that requires further studies. HipNav, an image-guided surgical navigation system, is presented. The system was developed to measure and guide the placement of prosthetic components in total hip replacement surgery (THR), it incorporates a 3-dimensional preoperative planner with a simulator and an intraoperative surgical navigator. Coupling optimized preoperative planning with accurate surgical navigation will assist the surgeon in properly orienting the components, minimizing the risk of impingement and dislocation. Intraoperatively, the system uses image-guided tools to assist in accurate placement of the acetabular cup. The acetabular implant is placed in the planned position with the aid of a simple "aim-and-shoot" interface. The actual measurements of version and abduction are also provided. The use of this new class of operative sensors has been incorporated into a regular surgical routine. There are few additional steps necessary, therefore, for the image-guided procedure, which does not add significantly to the total time of surgery. We expect that these tools will lead to less invasive and more accurate THR surgery and directly relate patient outcomes to measured surgical practice. Abstract Objective Traditional operation frequently depends on experience of doctors and anatomic landmark visual observation, which often leads to deviation in acetabular prosthesis implantation. Computer navigation technique greatly improves accuracy of prosthesis implantation. The present meta-analysis aimed at assessing the accuracy and clinical significance of computer navigation for acetabular implantation. Methods All studies published through March 2013 were systematically searched from PubMed, EMBnse, Science Direct, Cechrane library and other databases. Relevant journals or conference proceedings were searched manually. Only randomized controlled trials (RCTs) were included. Two independent reviewers identified and assessed the literature. Mean difference (MD) and Odds ratio (OR) of radiologic and clinical outcomes were pooled throughout the study between navigated and conventional THA. The meta-analysis was conducted by RevMan 5.1 software. Results Thirteen studies were included in the review, with a total sample size of 1071 hips. Statistically significant differences were observed between navigated and conventional groups in the number of acetabular cups implanted beyond the safe zone [OR = 0.13, 95 confidence interval (CI) (0.08–0.22); P P P = 0.004]. No significant differences in cup inclination, anteversion, incidence of postoperative dislocation or deep vein thrombosis were found. Conclusions The present meta-analysis indicated that the use of computer navigation in patients undergoing THA improves the precision of acetabular cup placement by decreasing the number of outliers, and decreases leg length discrepancy. More high quality RCTs are required to further confirm our results.