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Nerve injury following reverse shoulder arthroplasty (RSA) is a known risk factor with wide ranging incidences reported. This systematic review evaluates the overall incidence of nerve injury following primary and revision RSA and summarizes the characteristics of the nerve injuries reported in the current literature.A systematic review was performed using separate database searches (Pubmed, Embase, Web of Science, Cochrane) following the PRISMA guidelines. Search criteria included the title terms "reverse shoulder," "reverse total shoulder," "inverted shoulder," and "inverted total shoulder" with publication dates ranging from 01/01/2010 to 01/01/2022. Studies that reported neurological injuries and complications were included and evaluated for primary RSA, revision RSA, number of nerve injuries, and which nerves were affected.After exclusion, our systematic review consisted of 188 articles. A total of 40,146 patients were included, with 65% female. The weighted mean age was 70.3 years. The weighted mean follow-up was 35.4 months. The rate of nerve injury after RSA was 1.3% (510 of 40,146 RSAs). The rate of injury was greater in revision RSA compared to primary RSA (2.4% vs. 1.3%). Nerve injury was most common in RSAs done for a primary diagnosis of acute proximal humerus fracture (4.0%), followed by cuff tear arthropathy (3.0%), DJD (2.6%), and inflammatory arthritis (1.7%). Massive rotator cuff tears and post-traumatic arthritis cases had the lowest nerve injury rates (1.0% and 1.4%, respectively). The axillary nerve was the most commonly reported nerve that was injured in both primary and revision RSA (0.6%), followed by the ulnar nerve (0.26%) and median nerve (0.23%). Brachial plexus injury was reported in 0.19% of overall RSA cases.Based on current English literature, nerve injuries occur at a rate of 1.3% after primary RSA compared with 2.4% after revision RSA. The most common nerve injury was to the axillary nerve (0.64%), with the most common operative diagnosis associated with nerve injury after RSA being acute proximal humerus fracture (4.0%). Surgeons should carefully counsel patients prior to surgery regarding the risk of nerve injury.

This study's purpose is to compare clinical and radiographic outcomes of primary anatomic total shoulder arthroplasty (aTSA) and primary reverse total shoulder arthroplasty (rTSA) patients with osteoarthritis (OA) and an intact rotator cuff with no previous history of shoulder surgery using a single platform TSA system at a minimum follow-up of 2 years.A total of 370 aTSA patients and 370 rTSA patients matched for age, sex, and length of follow-up from an international multi-institutional Western Institutional Review Board approved registry with a minimum 2-year follow-up were reviewed for this study. All patients had a diagnosis of OA, an intact rotator cuff, and no previous shoulder surgery. All patients were evaluated and scored preoperatively and at latest follow-up using six outcome scoring metrics and four active range of motion measurements.Mean follow-up was 41 months, and the mean age was 73 years. Preoperatively, the rTSA patients had lower outcome metrics and less motion. Postoperatively, aTSA and rTSA patients had similar clinical outcomes, motion, and function, with the only exception being greater external rotation in aTSA exceeding the minimal clinically important difference. Pain relief was excellent, and patient satisfaction was high in both groups. Humeral radiolucent lines were similar in both groups (8%). Complications were significantly higher with aTSA (aTSA = 4.9%; rTSA = 2.2%; P = 0.045), but revisions were similar (aTSA = 3.2%; rTSA = 1.4%; P = 0.086).At a mean of 41 month follow-up, primary aTSA and rTSA patients with OA and an intact rotator cuff with no previous history of shoulder surgery had similar clinical and radiographic outcomes. Greater external rotation was noted in aTSA patients at follow-up. However, aTSA patients had a significantly greater rate of complications compared with rTSA patients. rTSA is a viable treatment option in patients with an intact rotator cuff and no previous shoulder surgery, offering similar clinical outcomes with a lower complication rate.Level III.

Previous studies have demonstrated that decreased impingement-free range of motion (ROM) can adversely influence clinical outcomes following reverse shoulder arthroplasty (RSA). Inferior placement of the glenosphere is thought to minimize impingement and its associated sequelae. This study evaluated the relationship between inferior overhang of the glenosphere and clinical outcomes in patients undergoing primary RSA using a lateralized humeral implant design.By use of a prospectively collected shoulder arthroplasty database, all primary RSAs performed at our institution between 2007 and 2015 with a single implant design (lateralized humerus and medialized glenoid) and minimum 2-year follow-up were evaluated. Glenosphere overhang in relation to the inferior rim of the glenoid was measured in millimeters on postoperative Grashey radiographs of the shoulder and categorized into tertiles (low,7.1 mm; medium, 7.1 to 9.9 mm; and high,9.9 mm). Clinical outcomes of interest comprised the changes between preoperative and postoperative values in the following ROM and outcome score measures: active forward elevation (aFE), active external rotation, American Shoulder and Elbow Surgeons score, Constant-Murley score, Shoulder Pain and Disability Index score, and Simple Shoulder Test score. Random-effects linear models were used to assess univariate and multivariable associations between overhang tertile and change in patient outcomes. Differences in outcomes were further compared using the minimal clinically important difference (MCID).The study identified 284 shoulders in 265 patients. The median follow-up period was 36 months (range, 24-108 months). The median glenosphere inferior overhang was 8.4 mm, with an interquartile range of 6.3-10.6 mm. Plots demonstrated nonlinear relationships between overhang and outcome scores and between overhang and ROM. Patients with high overhang experienced a significantly greater improvement in aFE compared with patients with low overhang (P = .019), which exceeded the MCID. No other differences in ROM and outcome scores between overhang groups exceeded the MCID. For other outcome scores and ROM measurements, there was no significant relationship with glenosphere overhang. Increased overhang was associated with a significantly lower incidence of scapular notching (P = .005).Patients undergoing RSA using a lateralized humerus design with greater inferior overhang of the glenosphere demonstrated a significantly greater improvement in aFE and lower rate of notching compared with those with low overhang. No ideal glenosphere overhang range was identified to maximize function in this study.

Introduction We use machine learning to create predictive models from preoperative data to predict the Shoulder Arthroplasty Smart (SAS) score, the American Shoulder and Elbow Surgeons (ASES) score, and the Constant score at multiple postoperative timepoints and compare the accuracy of each algorithm for anatomic (aTSA) and reverse (rTSA) total shoulder arthroplasty. Methods Clinical data from 2,270 aTSA and 4,198 rTSA patients were analyzed using 3 supervised machine learning techniques to create predictive models for the SAS, ASES, and Constant score at 6 different postoperative timepoints using a full input feature set and the 2 different minimal feature sets. Mean absolute errors (MAE) quantified the difference between actual and predicted outcome scores for each model at each postoperative timepoint. The performance of each model was also quantified by its ability to predict improvement greater than the minimal clinically important difference (MCID) and the substantial clinical benefit (SCB) patient satisfaction thresholds for each outcome measure at 2-3 years after surgery. Results All 3 machine learning techniques were more accurate at predicting aTSA and rTSA outcomes using the SAS score (aTSA: ±7.41 MAE; rTSA: ±7.79 MAE), followed by the Constant score (aTSA: ±8.32 MAE; rTSA: ±8.30 MAE), and finally the ASES score (aTSA: ±10.86 MAE; rTSA: ±10.60 MAE). These prediction accuracy trends were maintained across the 3 different model input categories for each of the SAS, ASES, and Constant models at each postoperative timepoint. For aTSA patients, the XGBoost predictive models achieved 94-97% accuracy in MCID with an AUROC between 0.90-0.97 and 89-94% accuracy in SCB with an AUROC between 0.89-0.92 for the 3 clinical scores using the full feature set of inputs. For rTSA patients, the XGBoost predictive models achieved 95-99% accuracy in MCID with an AUROC between 0.88-0.96 and 88-92% accuracy in SCB with an AUROC between 0.81-0.89 for the 3 clinical scores using the full feature set of inputs. Discussion Our study demonstrated that the SAS score predictions are more accurate than the ASES and Constant predictions for multiple supervised machine learning techniques, despite requiring less input data for the SAS model. Additionally, we predicted which patients will, and will not achieve clinical improvement that exceeds the MCID and SCB thresholds for each score; this highly accurate predictive capability effectively risk-stratifies patients for a variety of outcome measures using only preoperative data.

BACKGROUND Gradual loss of overhead range of motion (ROM) has been observed after reverse shoulder arthroplasty (RSA). It remains unclear if this is caused by the effect of RSA design on muscle fiber lengthening or is part of the natural aging process of the shoulder musculature. Although studies have attempted to evaluate deltoid fatigue after RSA, there is a paucity of literature evaluating this effect after anatomic shoulder arthroplasty (aTSA), which would be expected to occur due to aging alone. The purpose of this study is to evaluate the effect of time on overhead ROM after aTSA and compare this with previous data on a similar cohort of RSAs. We hypothesized that overhead ROM would decrease gradually over time in both groups without differences between prosthesis types. METHODS A retrospective review of 384 aTSAs without complications was performed over a 10-year period. All shoulders were treated for primary osteoarthritis using a single implant system. Patients were evaluated longitudinally at multiple postoperative time points. At least 1 follow-up visit was between 1 and 2 years postoperatively and another at least 5 years after surgery. ROM and patient reported outcome measures (PROMs) were evaluated using linear-mixed models for repeated measures. These results were compared with a previously evaluated cohort of 165 well-functioning RSAs analyzed using the same methodology. RESULTS Primary aTSA shoulders were observed to lose 0.7° of abduction per year starting 1 year postoperatively (P = .001). Smaller losses were observed in external rotation (-0.3°/yr, P = .06) and internal rotation (-0.04/yr, P < .001). However, no significant losses were observed in forward elevation (P = .8). All PROMs diminished slowly over time, but these changes did not exceed the minimally clinically important difference when modeled over 10 years (Simple Shoulder Test -0.08/yr, P < .001; American Shoulder Elbow Surgeons -0.5/yr, P < .001; University of California Los Angeles Shoulder Score -0.2/yr, P < .001). When compared with a similarly analyzed cohort of RSAs, overhead ROM decreased at a slower rate in the aTSA cohort (abduction -0.7° vs. -0.8°/yr, P = .9; FE -0.06° vs. -0.8°/yr, P = .05). DISCUSSION In the well-functioning aTSA, gradual loss of ROM occurs in all planes of motion except forward elevation. However, these losses are small and have little meaningful impact relative to minimally clinically important difference thresholds on PROMs. Progressive loss of abduction seen in both aTSA and RSA is likely secondary to aging of the periscapular and rotator cuff musculature. When compared with RSA, loss of motion after aTSA was statistically similar, calling into question the belief that RSA-induced deltoid fatigue leads to loss of overhead motion over time.

BACKGROUND Many patient-reported outcome measures (PROMs) have been used to follow clavicle fractures, providing an objective means to track outcomes. However, lack of standardization of PROM usage makes cross-study comparison difficult. Therefore, we reviewed articles on clavicle fractures from 11 of the most influential orthopedic journals to assess trends in PROM usage over time and based on geographic location. METHODS A focused systematic review of 11 of the most influential orthopedic journals was performed using PubMed. All articles published between 1981 and 2020 with greater than 9 patients reporting clinical outcomes of clavicle fractures were included. For each article, patient demographics, treatment modality, geographic location, and outcome measures used were recorded. Temporal trends were identified using the Cochran-Armitage test for trend and linear regression. Pearson chi-square and Kruskal-Wallis tests were used to compare between journals, geographic location, study type, and fracture classification. RESULTS From the initial literature search of 623 articles, 151 studies reporting on 15,853 primary clavicle fractures were included. Fractures of the middle one-third of the clavicle were most studied in the included literature (71%). Seventeen different PROMs were used, with an average of 1.6 outcome measures per study, and there was a significant increase in the number of PROMs used per article over time (P < .001). The Constant-Murley score was the most-reported outcome measure (44%) followed by the Disabilities of the Arm, Shoulder, and Hand score (27%), visual analog scale for pain (23%), and American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES; 14%). There was a significant difference between the measures used based on geography (P = .002), the most notable being that North American authors use the ASES score more frequently. CONCLUSIONS The use of PROMs in studies evaluating clavicle fracture treatment outcomes has increased over time, with recent studies reporting more PROMs than older studies, and there are notable differences in usage of the various scores based on geography and journal. Although there is no consensus on the most reliable PROM for assessing clavicle fractures, we recommend the use of at least 2 of the commonly reported PROMs in future studies to facilitate cross-study comparisons.

Background: The purpose of this study is to present surgical outcomes after humeral head allograft augmentation and glenoid-based procedures in patients with active, uncontrolled seizure activity and anterior shoulder instability. Methods: A retrospective review of a surgical database for patients with active seizure disorder and with recurrent shoulder instability managed with humeral head augmentation was performed. All patients underwent surgical intervention. Postoperative outcomes including Shoulder Pain and Disability Index, Simple Shoulder Test, American Shoulder and Elbow Surgeons questionnaire, and the Short Form Health Survey (SF-12) were recorded at a minimum of 2 years. We hypothesized that appropriate management of the bony defects in these bipolar injuries would result in low recurrence and satisfactory outcomes. Results: Ten patients including 8 males and 2 females (15 shoulders) with active seizure-related shoulder instability underwent surgical intervention including allograft bone grafting of the Hill-Sachs lesion for anterior shoulder instability. The average age was 27 years. All patients reported recurrent seizures postoperatively, but only one sustained a shoulder dislocation after surgery that was unrelated to seizure activity.Self-reported satisfaction was “much better” or “better” in 92% of shoulders. Average outcome scores were as follows: American Shoulder and Elbow Surgeons score = 67 (33-100), Shoulder Pain and Disability Index = 32.5 (0-83), Simple Shoulder Test = 9.4 (5-12), SF-12 PCS = 44.1 (21-65), and SF-12 MCS = 50.6 (21-61). The average follow-up was 4.8 years. Conclusion: Management of bipolar shoulder injuries with humeral head allograft augmentation and glenoid based surgery leads to low recurrence rates and good clinical outcomes in patients with uncontrolled, seizure-related shoulder instability.

The expansion of indications for reverse total shoulder arthroplasty (RTSA) has resulted in a rapid increase in the incidence of subsequent revision procedures. The purpose of this study was to identify the incidence and risk factors for re-revision shoulder arthroplasty after first revision RTSA.We retrospectively queried our institutional shoulder arthroplasty database of prospectively collected data from 2003 to 2019. To assess revision implant survival, patients were censored on the date of re-revision surgery or, if the revision arthroplasty was not revised, at most recent follow-up or their date of death. Patients with a prior infection, concern for infection at the time of revision, antibiotic spacer, or oncologic indication for primary arthroplasty were excluded. 186 revision RTSAs were included, with 32 undergoing re-revision shoulder arthroplasty. The Kaplan-Meier method and bivariate cox regression were used to assess the relationship of patient and surgical characteristics on implant survivorship. Multivariate cox regression was performed to identify independent predictors of re-revision.Re-revision shoulder arthroplasty was most commonly performed for instability (34%), infection (28%), and glenoid loosening (19%). Overall re-revision rates at 6 months (7%), 1 year (9%), 2 years (13%) were relatively low; however, the rate of re-revision increased at 5 years (35%). Men underwent re-revision more often than women within the first 6 months after revision RTSA (12% vs. 2%, p=0.025), but not thereafter. On multivariate analysis, increased estimated blood loss was associated with a greater risk of undergoing re-revision shoulder arthroplasty (HR 41.16 [3.34 - 506.50], p=0.004).The rate of re-revision after revision RTSA is low in the first 2 years postoperatively (13%) but increases to 35% at 5 years. Increased estimated blood loss, which may reflect greater operative complexity, was identified as a risk factor that may confer an increased chance of re-revision after revision RTSA. Knowledge of risk factors for re-revision after revision RTSA can aid surgeons and patients in preoperative counseling.

INTRODUCTION Rotator cuff repair (RCR) is commonly performed before reverse shoulder arthroplasty (RSA) with conflicting evidence on the effect on arthroplasty outcomes. The purpose of this investigation was to evaluate the effect of a prior RCR on the outcomes and complications of primary RSA. METHODS Between 2007 and 2017, 438 RSAs performed in patients with a prior RCR and 876 case-matched controls were identified from a multicenter database. Patients were grouped based on a preoperative diagnosis of glenohumeral osteoarthritis (GHOA) and rotator cuff tear arthropathy (CTA). Data collected included range of motion, strength, complications, and revisions. Additional clinical metrics included American Shoulder and Elbow Society score, Constant score, Shoulder Pain and Disability Index, Simple Shoulder Test, and the University of California Los Angeles shoulder score. RESULTS Compared with controls, both GHOA and CTA study groups demonstrated lower postoperative forward elevation (FE) (133° versus 147°, P < 0.001; 133° versus 139°, P = 0.048) and FE trength (6.5 versus 8.2, P = 0.004; 6.1 versus 7.3, P = 0.014). In addition, inferior improvements were observed in the GHOA and CTA study groups with respect to abduction (38° versus 52°, P = 0.001; 36° versus 49°, P = 0.001), FE (41° versus 60°, P < 0.001; 38° versus 52°, P = 0.001), ER (16° versus 25°, P < 0.001; 10° versus 17°, P = 0.001), and Constant score (28.4 versus 37.1, P < 0.001; 26.2 versus 30.9, P = 0.016). Compared with controls, no differences were observed in the GHOA and CTA study groups with respect to notching (11.2% versus 5.6%, P = 0.115; 5.8% versus 7.9%, P = 0.967), complications (4.3% versus 1.6%, P = 0.073; 2.5% versus 2.7%, P = 0.878), and revision surgery (3.1% versus 0.9%, P = 0.089; 1.1% versus 1.3%, P = 0.822). CONCLUSION RSA after a prior RCR improves both pain and function, without increasing scapular notching, complications, or revision surgery. However, compared with patients without a prior RCR, postoperative shoulder function may be slightly decreased. LEVEL OF EVIDENCE III; Retrospective Cohort Study.

Little information exists regarding the benefit of computer navigation in shoulder arthroplasty in the clinical setting. This study aimed to quantify how computer navigation affects the number and length of screws used during in vivo reverse total shoulder arthroplasty (RSA) placement.We performed a retrospective review of a research database to identify patients who underwent primary RSA before and after the use of computer navigation between January 1, 2015, and December 31, 2019. One hundred consecutive RSAs were selected from the computer navigation implantation date; then, 100 consecutive sex-matched RSAs were chosen prior to navigation implantation in reverse chronologic order. Baseplate augmentations were chosen based on surgeon discretion, with the goal of restoring version to within 10° of neutral and inclination to neutral or slightly inferior with removal of the smallest amount of subchondral bone possible. Screws were placed with the goal of ≥3 screws with good purchase and were added as needed, with up to 5 screws used. We compared demographic factors, comorbidities, preoperative diagnosis, number of screws, screw length, number of wasted screws, and number of cases with bone graft used behind the baseplate between the 2 groups. We used the χA total of 200 RSAs were included, with 100 primary RSAs (mean age, 69.3 years) performed prior to computer navigation compared with 100 primary RSAs (mean age, 69.7 years) performed using computer navigation. The total number of screws used in RSAs without computer navigation was 414; the total used in the computer navigation cases was 344. RSAs placed with computer navigation used significantly fewer screws per case (3.4 screws vs. 4.1 screws, P.001) and had a significantly greater average screw length (35.0 mm vs. 32.6 mm, P.001). Three screws were implanted in 61% of computer navigation cases vs. 1% of cases without computer navigation (P.001). Screws ≥ 30 mm in length were more commonly used in patients undergoing RSA using computer navigation (84.6% vs. 73.7%, P.001).This study shows that computer navigation in RSA leads to longer and fewer glenoid baseplate screws being implanted. Computer navigation appears to assist with better screw placement, which may have similar clinical benefits of better glenoid fixation. Additionally, using fewer screws can save glenoid bone stock, avoid added glenoid stress risers, and decrease operative time.

Acromial (ASF) and scapular spine (SSF) stress fractures are well-recognized complications of reverse shoulder arthroplasty (RSA), but much of the current data are derived from single-center or single-implant studies with limited generalizability. This study from the American Shoulder and Elbow Surgeons (ASES) Complications of Reverse Shoulder Arthroplasty Multicenter Research Group determined the incidence of ASF/SSF after RSA and identified preoperative patient characteristics associated with their occurrence.Fifteen institutions including 21 ASES members across the United States participated in this study. Patients undergoing either primary or revision RSA between January 2013 and June 2019 with a minimum 3-month follow-up were included. All definitions and inclusion criteria were determined using the Delphi method, an iterative survey process involving all primary investigators. Consensus was achieved when at least 75% of investigators agreed on each aspect of the study protocol. Only symptomatic ASF/SSF diagnosed by radiograph or computed tomography were considered. Multivariable logistic regression was performed to identify factors associated with ASF/SSF development.We identified 6755 RSAs with an average follow-up of 19.8 months (range, 3-94). The total stress fracture incidence rate was 3.9% (n = 264), of which 3.0% (n = 200) were ASF and 0.9% (n = 64) were SSF. Fractures occurred at an average 8.2 months (0-64) following RSA with 21.2% (n = 56) following a trauma. Patient-related factors independently predictive of ASF were chronic dislocation (odds ratio [OR] 3.67, P = .04), massive rotator cuff tear without arthritis (OR 2.51, P.01), rotator cuff arthropathy (OR 2.14, P.01), self-reported osteoporosis (OR 2.21, P.01), inflammatory arthritis (OR 2.18, P.01), female sex (OR 1.51, P = .02), and older age (OR 1.02 per 1-year increase, P = .02). Factors independently associated with the development of SSF included osteoporosis (OR 2.63, P.01), female sex (OR 2.34, P = .01), rotator cuff arthropathy (OR 2.12, P = .03), and inflammatory arthritis (OR 2.05, P = .03).About 1 in 26 patients undergoing RSA will develop a symptomatic ASF or SSF, more frequently within the first year of surgery. Our results indicate that severe rotator cuff disease may play an important role in the occurrence of stress fractures following RSA. This information can be used to counsel patients about potential setbacks in recovery, especially among older women with suboptimal bone health. Strategies for prevention of ASF and SSF in these at-risk patients warrant further study. A follow-up study evaluating the impact of prosthetic factors on the incidence rates of ASF and SSF may prove highly valuable in the decision-making process.

Background Reverse total shoulder arthroplasty (RTSA) is a successful procedure, often allowing patients to achieve better range of motion (ROM) compared with their preoperative baseline. However, there is a subset of patients who either fail to improve or lose ROM postoperatively. These patients are at increased risk of poor satisfaction and patient-reported outcomes. To date, characteristics of this subset of patients have not been well described. The purpose of this study is to determine risk factors associated with loss of ROM after primary RTSA. Methods A retrospective review using a commercial international RTSA database (Exactech Inc., Gainesville, FL, USA) of patients who underwent primary RTSA between 2007 and 2017 was performed. A total of 123 (7.7%) shoulders lost ≥10° of forward elevation (FE) (group 1, P1) and 183 (11.4%) lost ≥10° of external rotation (ER) (group 2, P2). Univariate and multivariate analyses were performed comparing these patients with control cohorts to evaluate risk factors for loss of motion. Results Better preoperative abduction, FE, ER, and internal rotation were each associated with greater loss of FE (P1 Conclusion Patients with greater preoperative shoulder ROM or higher patient-reported outcomes are at higher risk of losing ROM after primary RTSA. They are also at higher risk of reporting lower postoperative satisfaction, though the majority were still satisfied. Surgeons should strongly counsel patients with well-preserved preoperative function on the risk of loss of ROM.

Background We propose a new clinical assessment tool constructed using machine learning, called the Shoulder Arthroplasty Smart (SAS) score to quantify outcomes following total shoulder arthroplasty (TSA). Methods Clinical data from 3667 TSA patients with 8104 postoperative follow-up reports were used to quantify the psychometric properties of validity, responsiveness, and clinical interpretability for the proposed SAS score and each of the Simple Shoulder Test (SST), Constant, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), University of California Los Angeles (UCLA), and Shoulder Pain and Disability Index (SPADI) scores. Results Convergent construct validity was demonstrated, with all 6 outcome measures being moderately to highly correlated preoperatively and highly correlated postoperatively when quantifying TSA outcomes. The SAS score was most correlated with the UCLA score and least correlated with the SST. No clinical outcome score exhibited significant floor effects preoperatively or postoperatively or significant ceiling effects preoperatively; however, significant ceiling effects occurred postoperatively for each of the SST (44.3%), UCLA (13.9%), ASES (18.7%), and SPADI (19.3%) measures. Ceiling effects were more pronounced for anatomic than reverse TSA, and generally, men, younger patients, and whites who received TSA were more likely to experience a ceiling effect than TSA patients who were female, older, and of non-white race or ethnicity. The SAS score had the least number of patients with floor and ceiling effects and also exhibited no response bias in any patient characteristic analyzed in this study. Regarding clinical interpretability, patient satisfaction anchor-based thresholds for minimal clinically importance difference and substantial clinical benefit were quantified for all 6 outcome measures; the SAS score thresholds were most similar in magnitude to the Constant score. Regarding responsiveness, all 6 outcome measures detected a large effect, with the UCLA exhibiting the most responsiveness and the SST exhibiting the least. Finally, each of the SAS, ASES, Constant, and SPADI scores had similarly large standardized response mean and effect size responsiveness. Discussion The 6-question SAS score is an efficient TSA-specific outcome measure with equivalent or better validity, responsiveness, and clinical interpretability as 5 other historical assessment tools. The SAS score has an appropriate response range without floor or ceiling effects and without bias in any target patient characteristic, unlike the age, gender, or race/ethnicity bias observed in the ceiling scores with the other outcome measures. Because of these substantial benefits, we recommend the use of the new SAS score for quantifying TSA outcomes.

Background Few studies have evaluated the outcomes of glenoid baseplate migration after reverse shoulder arthroplasty (RSA). The question is whether an ingrowth central cage implant that has undergone early migration can restabilize due to cage ingrowth. The primary purpose of this study is to evaluate the radiographic factors associated with glenoid baseplate migration after RSA using a through-growth cage implant and secondarily evaluate their clinical outcomes with nonoperative management. Methods A retrospective review of a single institution database was performed from January 1,2008 to June 30, 2017 for all shoulders using a single implant system (Equinoxe, Exactech, Inc., Gainesville, FL, USA). All RSAs with a documented complication of glenoid loosening were evaluated. Chart and radiograph review was performed to identify shoulders with confirmed glenoid loosening undergoing revision (revision group, n = 10) and those with migration that stabilized over time and avoided revision surgery (stable migration group, n = 10). The stable migration group was matched to an age-, sex-, and follow-up matched control group (1:3) (control group, n = 30). Demographic factors, preoperative and immediate postoperative radiographic factors, active range of motion (ROM), and patient-reported outcomes (PROMs) were compared. Radiographic factors evaluated included preoperative alpha/beta angles, humeral lengthening, glenosphere overhang, prosthesis-scapular neck angle, glenosphere inclination, and postoperative alpha/beta angles. Results A total of 50 RSA patients were evaluated at a mean follow-up of 38 months. Immediate postoperative inferior glenoid overhang was significantly less in the stable migration group compared to the control group (6.2 vs. 8.6 mm, P = .03). Preoperative ROM and PROMs were similar amongst all 3 groups. The stable migration group demonstrated improved ROM and PROMs compared preoperatively with all ROM and PROM values exceeding the minimally clinically important difference (MCID). The control group demonstrated greater improvements in ROM and PROMs compared to the stable migration group, with a majority exceeding the MCID. When compared to the revision group, the stable migration group had significantly greater improvements in forward flexion, ASES score, and Constant score as well as improvements above the MCID in abduction, external rotation, and SST score. Conclusion RSA patients with glenoid migration and secondary stabilization still achieve improved ROM above the MCID, but the results are inferior to those RSA patients without glenoid migration. Approximately half of the shoulders with baseplate loosening using a through-growth cage implant will restabilize and have better ROM and function compared to those that are ultimately revised. Level of Evidence Level III; Treatment Study