Radiographic parameters associated with excellent versus poor range of motion outcomes following reverse shoulder arthroplasty.

BACKGROUND

The purpose was to evaluate the relationship of component size and position to postoperative range of motion following reverse shoulder arthroplasty. The hypothesis was that increased lateralization, larger glenospheres, and a decreased acromiohumeral distance would be associated with excellent postoperative range of motion.

METHODS

A retrospective multicenter study was performed at a minimum of one year postoperatively on 160 patients who underwent primary reverse shoulder arthroplasty with a 135° humeral component. Outcomes were stratified based on postoperative forward flexion and external rotation into excellent ( = 42), defined as forward flexion >140° and external rotation > 30°, or poor ( = 36), defined as forward flexion <100° and external rotation < 15°. Radiographic measurements and component features were compared between the two groups.

RESULTS

A larger glenosphere size was associated with an excellent outcome ( = 0.009). A 2-mm posterior offset humeral cup ( = 0.012) and an increased inferior glenosphere overhang (3.1 mm vs 1.4 mm;  = 0.002) were also associated with excellent outcomes. Humeral lateralization and distalization were not associated with an excellent outcome.arger glenosphere size and inferior positioning as well as posterior humeral offset are associated with improved postoperative range of motion following reverse shoulder arthroplasty.

LEVEL OF EVIDENCE

Level 3, retrospective comparative study.