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Background: Advancements in surgical planning, technique, and prosthesis design have improved adaptation to patient anatomy in reverse total shoulder arthroplasty (rTSA). Postoperative changes in deltoid and rotator cuff muscle length are important and may vary based on preoperative indications and prosthesis selection. The purpose of this study is to demonstrate the changes in deltoid and rotator cuff muscle length for planned rTSA using the spectrum of prosthesis configurations in both glenohumeral arthritis (GHOA) and rotator cuff tear arthropathy (RCA)., Methods: Ten shoulder arthroplasty surgeons used preoperative planning software to plan rTSA cases for 20 subjects (10 GHOA, 10 RCA) following surgical guidelines. Each surgeon planned each case using 3 prosthesis configurations: (1) 8-mm lateralized glenosphere and 135° neck-shaft angle (135 + 8), (2) 4-mm lateralized glenosphere and 145° neck-shaft angle (145 + 4), and (3) 0-mm lateralized glenosphere and 155° neck-shaft angle (155 + 0). Pre- and postoperative deltoid and rotator cuff muscle lengths and percentage-change were calculated and compared between prosthesis configurations within each indication. Different muscle lines of action were included representing the deltoid, subscapularis, infraspinatus, and teres minor., Results: Preoperatively, the RCA cohort had significantly shorter muscle lines of action in the posterior, lateral, and anterior deltoid (P < .001), a longer inferior subscapularis (P = .022), and a longer teres minor (P = .001) than the GHOA cohort. ANOVA and post-hoc analysis showed that postplanning lengths of each deltoid action line were greater in the 155 + 0 configuration compared to the 135 + 8 configuration in the RCA cohort (P < .001, P = .003, P = .032, respectively), and postplanning lengths of the anterior and middle deltoid action lines were also greater for the same comparison in the GHOA cohort (P = .004 and P = .017, respectively). There were no significant differences in postplanning deltoid lengths between the 135 + 8 and 145 + 4 configurations in either diagnosis cohort (P > .05). All postplanning rotator cuff muscle lengths (subscapularis, infraspinatus, and teres minor) differed significantly (P < .001) between all prosthesis configurations in both diagnosis cohorts, with the 135 + 8 configuration resulting in the longest lengths and the 155 + 0 configuration resulting in the shortest lengths., Conclusion: Automated preoperative planning software calculates the lengths of muscle action lines, which vary between GHOA and RCA diagnoses. Varying rTSA implant geometries result in predictable differences in deltoid lengthening and rotator cuff shortening. Shoulder prostheses with a more lateralized center of rotation show greater rotator cuff muscle length and similar deltoid muscle length when compared to medialized designs with similar deltoid lengthening. Surgeons can use this software to understand the impact of implant geometry on muscle length., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Postoperative dislocation is a known complication following reverse shoulder arthroplasty (RSA), but treatment patterns and outcomes remain unclear. The purpose of this study was to identify treatment patterns, rate of successful closed reductions, and factors associated with unsuccessful closed reductions for dislocations after RSA in a large multicenter patient cohort., Methods: A multicenter retrospective review was performed for patients receiving primary or revision RSA from June 2013 to May 2019 across 15 institutions in the United States. Patients who sustained a postoperative shoulder dislocation (defined as complete loss of articulation between the humeral component and glenosphere confirmed on imaging) with a minimum of 3-month follow-up were included. The time from surgery to dislocation, nature of the dislocation, complications associated with the dislocation, initial treatment, success of closed reduction, recurrent dislocations, and subsequent treatments including revision procedures, were recorded. Univariate analysis was performed to identify patient factors associated with failure of an initial closed reduction attempt., Results: A cumulative postoperative dislocation incidence of 2.1% (n = 138) was observed in the 6621 patients undergoing RSA. The median time to dislocation was 7 weeks (interquartile range = 33 weeks), with 61.6% (n = 85) occurring within the first 90 days after surgery. Initial treatment consisted of closed reduction (n = 87; 63.0%), open reduction (n = 1; 0.7%), revision arthroplasty (n = 43; 31.2%), or benign neglect (n = 7; 5.1%). Those treated without an initial closed reduction had higher incidence of associated complications (45.1% vs. 14.9%). Among patients initially treated with a closed reduction, 27 (31.0%) were successful (required no further interventions), 15 (17.2%) subsequently required a revision procedure, and 43 (49.4%) sustained an additional dislocation. The only patient or surgical factor associated with an unsuccessful closed reduction was increased body mass index (BMI; 31.8 ± 6 vs. 28.9 ± 5.2, P = .02). Of the 43 patients who sustained an additional dislocation, 10 received another closed reduction and 30 received revision surgery. Among the 10 patients who received a second closed reduction, 5 remained stable (50.0%). Overall, 92 patients (66.7%) required a revision arthroplasty procedure during the study period, whereas 22 (22.5%) required multiple revision procedures. Ultimately, 18 patients (13.0%) remained unstable (benign neglect) at final follow-up., Conclusion: In this large multicenter series of postoperative dislocations following RSA, a closed reduction was initially attempted in the majority of patients, but only about one-third were successful and required no further intervention. Unsuccessful closed reductions were associated with higher patient BMI. Revision surgery for dislocations was complicated by a high rate of recurrent dislocations and rerevision surgery., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Augmented baseplates can be effective at addressing eccentric glenoid wear in reverse total shoulder arthroplasty. However, these implants often come in a limited number of predetermined shapes that require additional reaming to ensure adequate glenoid seating. This typically involves complex instrumentation and can have a negative impact on implant stability. Modular baseplate augmentation based on intraoperative measurements may allow for more precise defect filling while preserving glenoid bone. The purpose of this investigation was to assess the stability of a novel ringed baseplate with modular augmentation in comparison with nonaugmented standard and ringed baseplate designs., Methods: In this biomechanical study, baseplate micromotion was tested for 3 constructs according to the American Society for Testing and Materials guidelines. The constructs included a nonaugmented curved baseplate, a nonaugmented ringed baseplate, and a ringed baseplate with an 8-mm locking modular augmentation peg. The nonaugmented constructs were mounted flush onto polyurethane foam blocks, whereas the augmented baseplate was mounted on a polyurethane block with a simulated defect. Baseplate displacement was measured before and after 100,000 cycles of cyclic loading., Results: Before cyclic loading, the nonaugmented and augmented ringed baseplates both demonstrated significantly less micromotion than the nonaugmented curved baseplate design (81.1 μm vs. 97.2 μm vs. 152.7 μm; P = .009). After cyclic loading, both ringed constructs continued to have significantly less micromotion than the curved design (105.5 μm vs. 103.2 μm vs. 136.6 μm; P < .001). The micromotion for both ringed constructs remained below the minimum threshold required for bony ingrowth (150 μm) at all time points., Conclusions: In the setting of a simulated glenoid defect, locked modular augmentation of a ringed baseplate does not result in increased baseplate micromotion when compared with full contact nonaugmented baseplates. This design offers a simple method for tailored baseplate augmentation that can match specific variations in glenoid anatomy, limiting the need for excessive reaming and ultimately optimizing the environment for long-term implant stability., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Introduction: As reverse shoulder arthroplasty (RSA) continues to grow in popularity for the treatment of glenohumeral osteoarthritis (GHOA) with an intact rotator cuff, it becomes increasingly important to identify factors that influence postoperative outcome. Although recent studies have demonstrated excellent postoperative range of motion and patient-reported outcome scores following RSA for GHOA, there continues to be surgeon hesitation to adopt RSA as a viable treatment in the younger patient population due to greater functional demands. In this study, we sought to determine the effect of age on clinical outcomes following RSA for GHOA through a comparison of patients over and under the age of 70., Methods: A retrospective review of prospectively collected data from an institutional registry was performed. Propensity score matching was utilized to match patients under the age of 70 (U-70) to those over 70 (O-70) in a 1:1 ratio based on sex, body mass index (BMI), preoperative ASES score, preoperative active forward elevation (FE), Walch classification, and American Society of Anesthesiologists comorbidity score. Clinical outcomes obtained preoperatively and at a minimum of 2 years postoperatively consisted of Visual Analog Scale (VAS) for pain, Single Assessment Numeric Evaluation (SANE) score, and American Shoulder and Elbow Surgeons (ASES) score, as well as active (FE), internal rotation, and external rotation. Descriptive statistics and univariate analysis were performed to compare cohorts., Results: After matching, each cohort consisted of 66 patients with similar mean follow-up periods (U-70, 28.1 ± 7.5 months vs. O-70, 27.4 ± 7.5 months; P = .887). Mean age of the U-70 cohort was 66.2 ± 3.3 while the O-70 cohort had a mean age of 75.3 ± 3.8. Both groups demonstrated significant improvement in VAS, SANE, and ASES scores, as well as active range of motion in all planes. The only significant difference between cohorts was greater postoperative FE in younger patients (143 ± 16° vs. 136 ± 15°; P = .017), though the baseline-to-postoperative improvement in FE was similar between cohorts (50 ± 29° vs. 43 ± 29°, P = .174)., Conclusion: RSA is a successful surgical treatment for GHOA regardless of age. Aside from greater postoperative FE in younger patients, there were no other differences in clinical outcomes between younger and older patients in this retrospective analysis, which compared patients who were matched by sex, BMI, and Walch classification, among other factors. Based on our results, 70 years of age should not be used as a threshold in preoperative counseling when determining whether a patient with GHOA with an intact rotator cuff is indicated for reverse shoulder arthroplasty., (Copyright © 2024. Published by Elsevier Inc.)

Background: Particle-induced osteolysis resulting from polyethylene wear remains a source of implant failure in anatomic total shoulder designs. Modern polyethylene components are irradiated in an oxygen-free environment to induce cross-linking, but reducing the resulting free radicals with melting or heat annealing can compromise the component's mechanical properties. Vitamin E has been introduced as an adjuvant to thermal treatments. Anatomic shoulder arthroplasty models with a ceramic head component have demonstrated that vitamin E-enhanced polyethylene show improved wear compared with highly cross-linked polyethylene (HXLPE). This study aimed to assess the biomechanical wear properties and particle size characteristics of a novel vitamin E-enhanced highly cross-linked polyethylene (VEXPE) glenoid compared to a conventional ultrahigh-molecular-weight polyethylene (UHMWPE) glenoid against a cobalt chromium molybdenum (CoCrMo) head component., Methods: Biomechanical wear testing was performed to compare the VEXPE glenoid to UHMWPE glenoid with regard to pristine polyethylene wear and abrasive endurance against a polished CoCrMo alloy humeral head in an anatomic shoulder wear-simulation model. Cumulative mass loss (milligrams) was recorded, and wear rate calculated (milligrams per megacycle [Mc]). Under pristine wear conditions, particle analysis was performed, and functional biologic activity (FBA) was calculated to estimate particle debris osteolytic potential. In addition, 95% confidence intervals for all testing conditions were calculated., Results: The average pristine wear rate was statistically significantly lower for the VEXPE glenoid compared with the HXLPE glenoid (0.81 ± 0.64 mg/Mc vs. 7.00 ± 0.45 mg/Mc) (P < .05). Under abrasive wear conditions, the VEXPE glenoid had a statistically significant lower average wear rate compared with the UHMWPE glenoid comparator device (18.93 ± 5.80 mg/Mc vs. 40.47 ± 2.63 mg/Mc) (P < .05). The VEXPE glenoid demonstrated a statistically significant improvement in FBA compared with the HXLPE glenoid (0.21 ± 0.21 vs. 1.54 ± 0.49 (P < .05)., Conclusions: A new anatomic glenoid component with VEXPE demonstrated significantly improved pristine and abrasive wear properties with lower osteolytic particle debris potential compared with a conventional UHMWPE glenoid component. Vitamin E-enhanced polyethylene shows early promise in shoulder arthroplasty components. Long-term clinical and radiographic investigation needs to be performed to verify if these biomechanical wear properties translate to diminished long-term wear, osteolysis, and loosening., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

Background: Clinically significant outcome (CSO) benchmarks have been previously established for shoulder arthroplasty by assimilating preoperative diagnoses and arthroplasty types. The purpose of this study was to establish unique CSO thresholds and compare the time-to-achievement of these for reverse shoulder arthroplasty (RSA) for osteoarthritis (GHOA), RSA for rotator cuff arthropathy (RCA), and total shoulder arthroplasty (TSA) for GHOA., Materials and Methods: Consecutive patients who underwent elective RSA for GHOA, TSA for GHOA, or RSA for RCA between February 2015 and May 2020, with 2-year minimum follow-up, were retrospectively identified from a prospectively maintained single surgeon registry. The American Shoulder and Elbow Surgeons (ASES) score was administered preoperatively and postoperatively at 2-week, 6-week, 3-month, 6-month, 1-year, and 2-year timepoints. Satisfaction and subjective overall improvement anchor questionnaires were administered at the time of final follow-up. Distribution-based methods were used to calculate the Minimal Clinically Important Difference (MCID), and anchor-based methods were used to calculate the Substantial Clinical Benefit (SCB) and the Patient Acceptable Symptom State (PASS) for each patient group. Median time to achievement, individual incidence of achievement at each time point, and cumulative incidence of achievement calculated using Kaplan-Meier survival curve analysis with interval censoring were compared between groups for each CSO. Cox-regression analyses were also performed to determine which patient factors were significantly associated with early or delayed achievement of CSOs., Results: There were 471 patients eligible for study analysis: 276 RSA for GHOA, 107 TSA for GHOA, and 88 RSA for RCA. The calculated MCID, SCB, and PASS scores differed for each group. There were no significant differences in median time to achievement of any CSO between groups. Log-rank testing revealed that cumulative achievements significantly differed between groups for MCID (P = .014) but not for SCB (P = .053) or PASS (P = .620). On cox regression analysis, TSA patients had earlier achievement of SCB, whereas TSA and RSA for GHOA patients had earlier achievement of MCID. At 2-years, a significantly higher percentage of RSA for GHOA patients achieved MCID and SCB compared to RSA for RCA (MCID:100%, 95.5%, P = .003, SCB:94.6%, 86.4%, P = .036)., Conclusion: Calculated CSO thresholds differ according to preoperative diagnosis and shoulder arthroplasty type. Patients undergoing TSA and RSA for GHOA achieve CSOs earlier than RSA for RCA patients, and a significantly higher percentage of RSA for GHOA patients achieve CSOs by 2 years compared to RSA for RCA patients., (Copyright © 2024. Published by Elsevier Inc.)

Background: As the indications for reverse total shoulder arthroplasty (RSA) continue to evolve, it has been more commonly utilized for the treatment of glenohumeral osteoarthritis with an intact rotator cuff (GHOA). Given the increased use of RSA for GHOA, it is important to identify factors influential of clinical outcomes. In this study, we sought to identify variables predictive of clinical outcomes following RSA for GHOA., Methods: Patients undergoing primary RSA for GHOA between 2015 and 2020 were retrospectively identified through a prospectively maintained, single surgeon registry. Eligible patients had complete patient-reported outcome measures and range of motion measurements with a minimum 2-year follow-up. Univariate analysis was utilized to compare characteristics and outcome measures of patients with poor and excellent outcomes, which was defined as postoperative American Shoulder and Elbow Surgeons (ASES) scores in the bottom and top quartiles, respectively. Multivariate linear regression was performed to determine factors independently predictive of postoperative ASES score., Results: A total of 230 patients were included with a mean follow-up of 33.4 months (SD 13.2). The mean age of the study population was 71.9 (SD 6.1). Two hundred twenty-four patients (97.4%) surpassed the minimal clinically important difference and 209 patients (90.1%) achieved substantial clinical benefit for ASES score. Preoperative factors differing between the poor and excellent outcome groups were sex (male: poor 37.9%, excellent 58.6%; P = .041), opioid use (poor 24.1%, excellent 5.2%; P = .009), ASES score (poor 32.9, excellent 41.0; P = .011), and forward elevation (poor 92°, excellent 101°; P = .030). Linear regression demonstrated that Walch B3 glenoids (β 7.08; P = .010) and higher preoperative ASES scores (β 0.14; P = .025) were predictors of higher postoperative ASES score, while postoperative complications (β -18.66; P < .001) and preoperative opioid use (β -11.88; P < .001) were predictive of lower postoperative ASES scores., Conclusion: Over 90% of patients who underwent RSA for GHOA with an intact rotator cuff experienced substantial clinical benefit. An unsurprising handful of factors were associated with postoperative clinical outcomes; higher preoperative ASES scores were slightly associated with higher postoperative ASES, whereas preoperative opioid use and postoperative complications were associated with lower postoperative ASES. Additionally, Walch glenoid type B3 was associated with higher postoperative ASES, indicating that patients with posterior glenoid defects are not predisposed to poor clinical outcomes following RSA. These results serve as a resource to improve preoperative patient counseling and manage postoperative expectations., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)