however , outcomes of anatomic arthroplasty with an osteoarthritic rotator - cuff - deficient shoulder have been limited .
the reverse shoulder arthroplasty ( rsa ) is a potential solution for shoulder osteoarthritis with deficient rotator cuff .
theoretical advantages of rsa are an increased lever arm of the deltoid muscle through a medialized center of rotation of the prosthesis ( increasing deltoid efficiency ) , increased prosthetic stabilization through humeral lengthening ( increasing deltoid tension ) , and decreased mechanical torque at the glenoid component ( decreasing glenoid loosening )
these factors are related to the indication for surgery , surgeon 's experience , characteristics of the implant , characteristics of the surgical technique , type of approach , or postoperative rehabilitation , among others .
unfortunately , the analysis of outcomes of rsa depending on the type of prosthesis , type of approach , and indication for surgery has not been well reported to date .
the purpose of this study was to compare the clinical and functional outcomes of rsa depending on the surgical approach , type of prosthesis , and indication for surgery through a comprehensive , systematic review of the literature .
the methodology for this study was reported following the prisma statement for systematic review and meta - analysis .
all human studies reporting clinical and/or functional outcomes in patients treated with primary or revision rsa were assessed for eligibility .
studies were included if they had a level of evidence between i and iv , were written in english , had a minimum of 2 years of follow - up and had a minimum sample size of 10 patients . studies reporting complications only , nonoriginal articles , or studies with insufficient outcome data
the authors are not aware of any relevant publication related to rsa before 1985 , so the search was limited to this period .
the keywords and search strategy employed in this study included the following : ( reverse or inverse ) and shoulder and ( arthroplasty or replacement or prosthesis ) , limited to human studies published in the above - mentioned period .
thus , cinahl , ebsco - sportdiscus , and the cochrane central register of controlled trials were also used to search for relevant publications in the same period .
articles of potential interest were reviewed in detail ( full text ) by two authors and a decision was made regarding inclusion or exclusion .
clinical and functional outcomes were extracted from all included studies in a systematic way using a table template by one author , which was then verified by another author . in cases of disagreement between both authors with regard to study inclusion or data extraction ,
a reference list of all included articles was reviewed to search for potential studies not previously identified .
mean , standard deviation ( sd ) , and range were extracted ( whenever provided ) in the preoperative and postoperative periods for the following variables : constant score , american shoulder and elbow society ( ases ) score , simple shoulder test , range of motion ( rom ) , and satisfaction .
furthermore , relevant information regarding level of evidence , type of prosthesis ( either with medialized or lateralized center of rotation ) , type of approach ( either deltopectoral or superolateral ) , indication for rsa , sample size , percentage of females in the sample , follow - up , and age of patients was extracted from all studies .
the pubmed search yielded 329 citations , from which 174 were clinical studies in humans that were reviewed in further detail .
about 32 met inclusion criteria and additional database searches and review of the reference list from included articles yielded a final number of 35 articles included in the descriptive analysis of clinical outcomes [ figure 1 ] . from all 174 articles assessed for eligibility ,
the senior author had to review four of them because of disagreement between the two authors conducting the systematic review .
literature search flow chart the 35 included studies were grouped depending on the approach and type of prosthesis : deltopectoral approach associated with prosthesis with a medialized center of rotation ( dm group ; n = 18 studies ) , lateralized ( dl group ; n = 8 studies ) , and a combination of approaches associated with a medialized prosthesis ( cm group ; n = 9 studies ) .
the latter group was created because the authors employed different approaches , but clinical outcomes were not specified depending on the type of approach ( all these studies employed a prosthesis with a medialized center of rotation ) .
prostheses with a medialized center of rotation included in this study were the following : delta iii ( depuy , france ) , delta xtend ( depuy , warsaw , in , usa ) , aequalis ( tornier , france ) , smr modular shoulder system ( systema multiplana randelli , lima - lto , san daniele de friuli , italy ) , and exactech ( gainesville , fl , usa ) .
prostheses with a more lateralized center of rotation included in this study were the following : reverse shoulder prosthesis ( djo surgical , austin , texas ) , and arrow anatomical shoulder system ( mulhouse , france ) .
the 35 studies included a total sample of 2049 patients with a mean ( sd ) percentage of females of 71.6% ( 13.4 ) , age of 71.5 years ( 3.7 ) , and follow - up of 43.1 months ( 18.8 ) ; the respective data separately in groups was , dm , 1085 patients , 73.4% ( 10.2 ) , 72.4 years ( 3.1 ) , and 38.1 months ( 8.2 ) .
dl , 241 patients , 69.7% ( 12.5 ) , 70.1 years ( 1.7 ) , and 40 months ( 7.6 ) and cm group , 723 patients , 73.1% ( 7.5 ) , 73 years ( 2.8 ) , and 50.6 months ( 33.9 ) .
clinical outcomes depending on the type of approach - type of prosthesis in the analysis of clinical outcomes depending on the indication for rsa , not all 35 studies could be included because results were not always specified by indication . the number of studies included ( total subjects involved ) by indications for rsa were cuff tear arthropathy 12 ( 581 ) ; revision of anatomic prosthesis 10 ( 263 ) ; failed rotator cuff repair 5 ( 150 ) ; fracture sequelae 4 ( 82 ) ; rheumatoid arthritis 3 ( 52 ) ; massive cuff tear 2 ( 68 ) ; primary osteoarthritis with degenerative cuff tear 2 ( 51 ) ; posttraumatic osteoarthritis 2 ( 59 ) ; and revision of reverse prosthesis 1 ( 14 ) .
indications of rsa for tumors and acute fractures were not included due to limited data .
mean ( sd ) for percentage of females , age , and follow - up depending on indications was the following : cuff tear arthropathy 74% ( 12 ) , 72.5 years ( 3.4 ) , and 34.6 months ( 8) , respectively ; revision of anatomic prosthesis 66.5% ( 11.7 ) , 68.2 years ( 2.7 ) , and 38.2 months ( 6.6 ) ; failed rotator cuff repair 69% ( 19.8 ) , 69.8 years ( 3.6 ) , and 39.6 months ( 11.8 ) ; fracture sequelae 70% ( 8.1 ) , 73.2 years ( 5.3 ) , and 37.6 months ( 8.2 ) ; and rheumatoid arthritis 87.6% ( 9.8 ) , 68.2 years ( 2.9 ) , and 56 months ( 22.2 ) , respectively . for massive cuff tear , primary osteoarthritis with degenerative rotator cuff , and posttraumatic osteoarthritis only the mean ( range ) follow - up was provided : 34 months ( range 24 - 118 ) , 38 months ( range 24 - 81 ) , and 42 months ( range 24 - 97 ) , respectively . for revision of reverse prosthesis , percentage of females , and mean ( sd ) of age and follow - up were 28% , 70.6 years ( 8.7 ) , and 33 months ( 11.2 ) , respectively .
table 2 summarizes the clinical outcomes depending on the most common indication for rsa in the included studies .
the purpose of this study was to compare the clinical and functional outcomes of rsa depending on the type of prosthesis ( with either medialized or lateralized center of rotation ) , type of approach , and indication for surgery .
the principal finding of this study was that both types of prostheses clearly improved the outcomes , but lateralized prostheses had more pre - to - postoperative differences ( improvement ) for ases total and pain scores and external rotation compared with medialized prostheses .
in addition , outcomes depending on each indication considerably improved , but those corresponding to revision of anatomic prosthesis , failed rotator cuff repair , and fracture sequelae demonstrated lower improvements compared to cuff tear arthropathy .
the postoperative patient 's satisfaction with surgery was very high ( overall mean of 90% ) in both types of prostheses and for all indications for surgery .
to the best of our knowledge , this is the first systematic review aimed to investigate the clinical and functional outcomes of rsa depending on the type of prosthesis , type of approach , and an indication for surgery .
khan et al . conducted a comprehensive , systematic review aimed to investigate the outcomes of rsa depending for cuff tear arthropathy , massive cuff tear , and rheumatoid arthritis .
however , the authors only included delta ii prostheses and the review included studies up to 2010 .
the present investigation found many references in the last 2 years and in addition , different type of prostheses , more indications , and a higher number of studies were analyzed .
based on the present study and on the existing literature , rsa is an excellent surgical solution with great improvements in clinical outcomes for cuff tear arthropathy , massive cuff tear , 42 failed rotator cuff repair , rheumatoid arthritis , fracture sequelae , revision of anatomic prosthesis , and revision of reverse prosthesis .
in addition , both types of prostheses demonstrated excellent improvements in the postoperative period with regard to all outcomes . the fact that prostheses with lateralized center of rotation had greater improvement in ases and external rotation have to be interpreted with caution , as this study had some limitations . first and foremost , a pooled analysis of the results ( meta - analysis with inferential statistics ) was not possible for methodological reasons , as nearly all studies did not report the sd in the outcomes and an accurate meta - analysis could not be , therefore , conducted .
in addition , most of the studies did not disclose the outcomes depending on the indications for surgery , so this parameter had to be considered separately to avoid a significant decrease in the number of studies included in the comparisons of outcomes .
thus , only the type of prosthesis and type of approach could be analyzed altogether .
second , as almost all included studies were case series , the comparison of outcomes depending on the type of prosthesis , approach , and an indication was indirect in nature with a greater potential influence of uncontrolled variables .
third , the influence of several factors potentially influencing the outcomes could not be assessed because of limited information , heterogeneity of studies , and small number of studies included for some comparisons ( which would decrease even more the available data if more subgroups were done ) .
finally , it must be mentioned that the ases score in medialized prosthesis was only reported by one study , which may decrease the value of the comparison of this parameter between medialized and lateralized prostheses .
it must be first recognized that there are a considerable number of potential factors not controlled in this analysis that may have a potential influence on the outcomes : different surgeon 's experience , different rehabilitation protocols ( given the multicentric nature of this study ) , type ( eccentric or concentric ) and size of glenosphere , location and orientation of the glenosphere and humeral components ( inferiorly placed glenosphere , anteversion / retroversion , of the humeral component ) degree of fatty infiltration of the teres minor muscle , degree of bone stock , soft tissue tensioning , status of the subscapularis muscle , humeral osteotomy angle , or previous surgery . in addition , no attempt was made to analyze data based on differences in humeral components , medialized versus lateralized , high neck angle versus low neck angle , sit - on - top versus sit inside , and cemented versus uncemented . in the present study , the influence of the type of approach on the outcomes of rsa could not be well determined .
some studies used a combination of approaches , and the outcomes were not specified depending on whether the approach was deltopectoral or superolateral .
therefore , some studies were grouped as cm to refer to studies using a combination of approaches ( and a medialized prosthesis ) . in some ways ,
differences between groups dm and cm may be explained by differences in the type of approach , as a type of prosthesis in both groups has a medialized center of rotation .
however , considering that the cm has a combination of approaches rather than a unique superolateral approach , no clear conclusions can be drawn regarding its influence on the outcomes of rsa .
there are some studies that have found that the surgical approach does not have an influence on the outcomes of rsa .
clearly , further research is needed in this aspect to better elucidate the influence of the type of approach on the outcomes of rsa .
well - designed level i- or ii - evidence comparative studies are needed before clear conclusions can be established . nonetheless , the clinical relevance of this research question ( influence of the type of approach ) may be questioned , as some surgeons may be forced to adopt a certain approach based on the surgical history of the patient or the characteristics of the patient 's disorder itself .
the type of prosthesis ( with a medialized or lateralized center of rotation ) seems to have a much more relevant influence on the outcomes of rsa .
given that many studies only employed the deltopectoral approach , the type of prosthesis was more easily isolated .
thus , the comparison between dm and dl may show the influence of the center of rotation on the outcomes . essentially , both groups demonstrated great improvements in outcomes in the postoperative period .
unfortunately , no studies employing a lateralized center of rotation reported the constant score , so no comparisons were possible between dm and dl for this parameter .
in addition , the ases score was only reported by one study in the dm group so no accurate conclusions can be drawn for this parameter .
specifically , the dl group demonstrated greater improvements in external rotation compared to the dm group .
the reasons for lower improvement in external rotation in medialized prostheses have been suggested by boileau et al . , and grammont and baulot .
a medialized center of rotation may imply that the humeral cup impinges the posterior neck of the scapula when the arm is at the side .
in addition , as the posterior deltoid theoretically provides some external rotation when coupled with some abduction , the medialization of the center of rotation may decrease the efficacy of the posterior deltoid to assist in the external rotation . also , the status of the teres minor may influence the degree of external rotation , but this variable was not controlled in the vast majority of studies .
conducted an interesting study in which the center of rotation of a medialized prosthesis was lateralized by placing a bone autograft from the humeral head between the base plate and the scapula .
this bony lateralization of the center of rotation demonstrated good integration and the authors found 53 of external rotation and a constant score of 66 .
unfortunately , this was a case series and comparisons with medialized prostheses were only conducted based on the existing literature .
the disadvantage of metallic , as opposed to bony , lateralization may be the higher torque or shear force applied to the glenoid component , which may lead to a higher rate of glenoid loosening and screw breakage witnessed .
therefore , bony lateralization was suggested to provide a benefit to external rotation without the potentially disastrous consequences of metallic lateralization . in a similar way , valenti et al . reported the outcomes of a lateralized prosthesis and concluded that less medialization of rsa improves external rotation , thus facilitating activities of daily living of older patients .
however , the authors did not compare the outcomes with a sample of patients undergoing rsa with a medialized prosthesis , so their conclusion was again based on a comparison with the existing literature . no level i- or ii - evidence studies aimed to compare the outcomes of rsa depending on the type of prosthesis were found in the literature .
most common indications for rsa were cuff tear arthropathy , revision of anatomic prosthesis , failed rotator cuff repair and fracture sequelae .
this study shows that the indication for surgery may have an impact on the outcomes of rsa , which is in accordance with the existing literature .
some authors found that patients with no previous surgery undergoing rsa had higher postoperative scores in ases ( total , pain , and function ) and constant ( total and pain ) compared to patients with previous surgery .
however , other authors observed no significant differences in the improvement or postoperative values of constant score , ases , simple shoulder test , visual analogue scale for pain and function , oxford shoulder score , university of california in los angeles ( ucla ) shoulder scale , and rom between patients with and without previous surgery .
for specific indications , the present study demonstrated that cuff tear arthropathy had higher improvements in constant score ( total , pain , and activity ) , ases score ( total , pain , and function ) , simple shoulder test , forward flexion , and abduction compared to revision of anatomic prosthesis .
although there were no inferential statistics in the present study , these results are both in agreement and disagreement with previous studies .
found that patients with cuff tear arthropathy had significantly higher improvements in constant score compared with patients undergoing revision of the prosthesis .
the authors found a higher improvement ( no p value provided ) in ases score and external rotation in cuff tear arthropathy compared with revision of prosthesis , but no differences ( no p value provided ) in forward flexion .
regarding the constant score , wall et al . found that cuff tear arthropathy and primary osteoarthritis with degenerative rotator cuff had a higher postoperative constant score ( no p value provided ) compared to revision of anatomic prosthesis , massive cuff tear , and posttraumatic osteoarthritis
in fact , revision of anatomic prosthesis and posttraumatic osteoarthritis had significantly worse postoperative constant score compared to the other indications .
found that patients with cuff tear arthropathy and posttraumatic osteoarthritis had higher improvements ( no p value provided ) in external rotation compared to revision of prosthesis , massive cuff tear , and primary osteoarthritis with degenerative rotator cuff .
for forward flexion , cuff tear arthropathy and revision of anatomic prosthesis had the highest improvement ( no p value provided ) compared with massive cuff tear , posttraumatic osteoarthritis , and primary osteoarthritis with degenerative rotator cuff .
reported a case series in which patients underwent hemiarthroplasty , anatomic total shoulder arthroplasty , or rsa and outcomes were analyzed depending on the indication for surgery .
the authors found that the primary osteoarthritis with degenerative rotator cuff and cuff tear arthropathy had a significantly higher improvement of the constant score compared to rheumatoid arthritis and avascular necrosis .
unfortunately , the number of rsa in the groups of primary osteoarthritis with degenerative rotator cuff , rheumatoid arthritis , and avascular necrosis was 2 , 6 , and 0 , respectively . therefore , the significant differences are likely explained by anatomic prostheses instead of rsa .
similarly , walch et al . found that cuff tear arthropathy , primary osteoarthritis with degenerative rotator cuff , and massive cuff tear had significantly higher improvement of the constant score compared with the revision of the prosthesis and posttraumatic osteoarthritis .
there is a clear need for future studies specifically comparing the use of medialized and lateralized rsa , as the present comparison was indirect in nature given that no comparative studies of this parameter have been published to date .
further clarification is needed to know to which extent there are significant differences in functional outcomes as well as in external rotation between both models .
it is probable that differences on the implanted humeral side may have profound outcome implications , yet there has been no focus on this side of the joint in rsa outcome studies .
in addition , the exact impact of the type of approach on the outcomes needs to be better delineated . in any further study utilizing more than one approach and type of prosthesis ,
furthermore , as the results of rsa may differ depending on the indications for surgery , disclosure of outcomes for indications is also warranted
. finally , there are two methodological recommendations regarding the presentation of studies to facilitate further meta - analyses .
first , it is important from a methodological and statistical point of view to report the sd in all parameters collected .
most studies employing prostheses with medialized center of rotation used the constant score , whereas studies utilizing lateralized prostheses used the ases score .
other investigations employed the simple shoulder test , the oxford shoulder score , or the ucla shoulder scale .
only rom is systematically provided in the published studies , but more homogeneity is required to facilitate further meta - analyses .
both types of prostheses ( with medialized and lateralized center of rotation ) clearly improved all the reported outcomes , but lateralized prostheses had more improvement in external rotation compared to medialized prostheses .
all outcomes of rsa implanted for all types of indications significantly improved in the postoperative period , but those corresponding to revision of anatomic prosthesis , failed rotator cuff repair , and fracture sequelae demonstrated lower improvements compared with cuff tear arthropaty .
the rsa is a surgical procedure with high patient satisfaction regardless of the type of prosthesis or the indication for surgery .
there is no conflict of interest or financial aid from any organization regarding the material discussed in the manuscript .
thomas w. wright , m.d . is a consultant for exactech , inc . , gainesville , florida , and receives royalties and institutional research support on products cited to this article .
 many factors influence the outcomes of reverse shoulder arthroplasty ( rsa ) . 
 the purpose of this study was to compare the clinical and functional outcomes of rsa depending on the surgical approach , type of prosthesis , and indication for surgery through a comprehensive , systematic review.a literature search was conducted ( 1985 to june 2012 ) using pubmed , cinahl , ebsco  
 sportdiscus , and cochrane central register of controlled trials . 
 levels i  iv evidence , in - vivo human studies ( written in english with minimum of 2 years of follow - up and sample size of 10 patients ) reporting clinical and/or functional outcomes after rsa were included . 
 the outcomes were analyzed depending on the surgical approach , type of prosthesis ( with medialized or lateralized center of rotation ) , or indication for surgery.a total of 35 studies were included involving 2049 patients ( mean [ sd ] percentage of females , age , and follow - up of 71.6% [ 13.4 ] , 71.5 years [ 3.7 ] , and 43.1 months [ 18.8 ] , respectively ) . 
 studies using deltopectoral approach with lateralized prostheses demonstrated greater improvement in external rotation compared with medialized prostheses with the same approach ( mean 22.9 and 5 , respectively ) . in general , rsa for cuff tear arthropathy demonstrated higher improvements in constant and american shoulder and elbow society scores , and range of motion compared with revision of anatomic prosthesis , failed rotator cuff repair , and fracture sequelae.lateralized prostheses provided more improvement in external rotation compared to medialized prostheses . 
 indications of rsa for cuff tear arthropathy demonstrated higher improvements in the outcomes compared with other indications . 
 rsa demonstrated high patient 's satisfaction regardless of the type of prosthesis or indication for surgery.level of evidence : level iv . 