Advanced cuff tear arthropathy: classic indication for a Grammont-style reverse shoulder arthroplasty implant or does bipolar lateralization perform better?

Abstract

BackgroundAdvanced cuff tear arthropathy (CTA) is associated with proximal humeral migration and medialization of the joint line. Our aim was to compare a nonlateralized prosthesis with an eccentric glenosphere with a lateralized prosthesis in a comparable cohort of advanced CTA. MethodsPatients with a type 4 and 5 CTA according to Hamada underwent reverse shoulder arthroplasty (RSA) between March 2014 and June 2018 and were documented prospectively up to 2 years postsurgery. Comparative RSA groups were “lateralized” (LAT) with 135° humeral inclination and 36 + 4 mm lateralized glenosphere and “nonlateralized” (NONLAT) with 155° humeral inclination and 36 + 2 mm eccentric glenosphere. Range of motion, Constant-Murley score and Shoulder Pain and Disability Index were assessed. Anteroposterior and axial radiographs were evaluated at 2 years, and additional measurements of scapular anatomy, implant position, center of rotation, humeral offset as well as lateralization, and distalization shoulder angles were performed. We used linear regression and mixed models adjusted for age, sex, and preoperative values. ResultsTwenty LAT and 11 NONLAT met the inclusion criteria. Baseline parameters were comparable, including cuff tear morphology (100% Type C in Group LAT; 80% C/D in Group NONLAT). At 2-year follow-up, Constant-Murley score (difference 5 points; 95% confidence interval −14 to 3; P = .727) and Shoulder Pain and Disability Index (difference 4 points; 95% confidence interval −12 to 21; P = .456) were not significantly different between groups. External rotation for Group LAT (mean 36°) was higher than for Group NONLAT (mean 20°) (16°; 3-29; P = .026); a greater proportion of Group LAT patients could reach the lumbar vertebra 3 (L3) (75% vs. 36% in Group NONLAT) but there was no statistical significance (P = .119). Group NONLAT had a higher inferior glenosphere overhang (2.3 mm; 0.4-4.1; P = .025), center of rotation medialization (7.5 mm; 3.9-11.2; P < .001), lowering of center of glenohumeral rotation (7.9 mm; 3.3-12.3; P = .002), and distalization shoulder angle (16.3°; 8.3-24.3; P = .001), whereas Group LAT had higher humeral offset (11.9 mm; 7.9-15.8; P < .001) and lateralization shoulder angle (15.8°; 8.0-23.7; P = .001). In the NONLAT group, 60% showed scapular notching and in the LAT group 35% (P = .306). ConclusionPatients with an RSA with 135° humeral inclination and a lateralized glenosphere show better rotation and less scapular notching compared to patients with a nonlateralized design and eccentric glenosphere in advanced CTA Hamada 4 and 5.