Analysis of three different reverse shoulder arthroplasty designs for cuff tear arthropathy - the combination of lateralization and distalization provides best mobility.

BACKGROUND: The two major reverse shoulder arthroplasty (RSA) designs are the Grammont design and the lateralized design. Even if the lateralized design is biomechanically favored, the classic Grammont prosthesis continues to be used. Functional and subjective patient scores as well as implant survival described in the literature so far are comparable to the lateralized design. A pure comparison of how the RSA design influences outcome in patients has not yet been determined. The aim of this study was a comparison focused on patients with cuff tear arthropathy (CTA). METHODS: We analyzed registry data from 696 CTA patients prospectively collected between 2012 and 2020 in two specialized orthopedic centers up to 2 years post-RSA with the same follow-up time points (6,12 24 months). Complete teres minor tears were excluded. Three groups were defined: group 1 (inlay, 155° humeral inclination, 36 + 2 mm eccentric glenosphere (n = 50)), group 2 (inlay, 135° humeral inclination, 36 + 4 mm lateralized glenosphere (n = 141)) and group 3 (onlay, 145° humeral inclination, + 3 mm lateralized base plate, 36 + 2 mm eccentric glenosphere (n = 35)) We compared group differences in clinical outcomes (e.g., active and passive range of motion (ROM), abduction strength, Constant-Murley score (CS)), radiographic evaluations of prosthetic position, scapular anatomy and complications using mixed models adjusted for age and sex. RESULTS: The final analysis included 226 patients. The overall adjusted p-value of the CS for all time-points showed no significant difference (p = 0.466). Flexion of group 3 (mean, 155° (SD 13)) was higher than flexion of group 1 (mean, 142° (SD 18) and 2 (mean, 132° (SD 18) (p < 0.001). Values for abduction of group 3 (mean, 145° (SD 23)) were bigger than those of group 1 (mean, 130° (SD 22)) and group 2 (mean, 118° (SD 25)) (p < 0.001). Mean external rotation for group 3 (mean, 41° (SD 23)) and group 2 (mean, 38° (SD 17)) was larger than external rotation of group 1 (mean, 24° (SD 16)) (p < 0.001); a greater proportion of group 2 (78%) and 3 (69%) patients reached L3 level on internal rotation compared to group 1 (44%) (p = 0.003). Prosthesis position measurements were similar, but group 3 had significantly less scapular notching (14%) versus 24% (group 2) and 50% (group 1) (p = 0.001). CONCLUSIONS: Outcome scores of different RSA designs for CTA revealed comparable results. However, CTA patients with a lateralized and distalized RSA configuration were associated with achieving better flexion and abduction with less scapular notching. A better rotation was associated with either of the lateralized RSA designs in comparison with the classic Grammont prosthesis. LEVEL OF EVIDENCE: Therapeutic study, Level III.

Scapulothoracic orientation has a significant influence on the clinical outcome after reverse total shoulder arthroplasty.

BACKGROUND: Computer simulation has indicated a significant effect of scapulothoracic orientation and posture on range of motion (ROM) after reverse total shoulder arthroplasty (RTSA). We analyzed this putative effect on the clinical and radiological outcome post-RTSA. METHODS: We retrospectively assessed 2-year follow-up data of RTSA patients treated at our clinic between 2008 and 2019. Patients were categorized into posture types A, B, and C based on an established method using scapular internal rotation on preoperative cross-sectional imaging. We compared differences in clinical ROM, pain, Subjective Shoulder Value, Constant Score, Shoulder Pain and Disability Index (SPADI), quality of life (EQ5D5L utility index) and radiological outcomes between posture types using linear regression analyses. RESULTS: Of 681 included patients, 225 had type A posture, 326 type B and 130 type C. Baseline group characteristics were comparable, although the type C group had a higher proportion of females (60% [A]; 64% [B]; 80% [C]) with lower abduction strength (0.7 kg [A]; 0.6 kg [B]; 0.3 kg [C]) and a slightly higher proportion with a Grammont design RTSA (41% [A]; 48% [B]; 54% [C]). There were significant adjusted differences in mean (±standard deviation) active flexion (A: 137±21°; B: 136±20°; C: 131±19°) and passive flexion (A: 140±19°; B: 138±19°; C: 134±18°), active (A: 127±26°; B: 125±26°; C: 117±27°) and passive abduction (A: 129±24°; B: 128±25°; C: 121±25°), SPADI (A: 81±18; B: 79±20; C: 73±23) and pain (A: 1.2±1.7; B: 1.6±2.2; C: 1.8±2.4) between posture types at 2 years (p≤0.035). A higher distalization shoulder angle was associated with better abduction in type C patients (p=0.016). Type C patients showed a trend towards a higher complication rate (3.9% vs 1.1% [A]; 3.2% [B]) (p=0.067). CONCLUSIONS: Type C posture influences the 2-year clinical outcome of RTSA patients in terms of worse flexion, abduction, SPADI and pain. Scapulothoracic orientation and posture should be considered during the patient selection process, preoperative planning and implantation of a RTSA.