Preoperative diagnosis and rotator cuff status impact functional internal rotation following reverse shoulder arthroplasty.

PURPOSE: This study aimed to evaluate whether functional internal rotation (fIR) following reverse shoulder arthroplasty (RSA) differs based on diagnosis of either: primary osteoarthritis (OA) with intact rotator cuff, massive irreparable rotator cuff tear (MICT) or cuff tear arthropathy (CTA).

METHODS: A retrospective review was carried out on RSAs performed by a single surgeon with the same implant over a 5-year period. Minimum 2-year follow-up was available in 235 patients; 139 (59.1%) were female, and the mean patient age was 72 ± 8 years. Additional clinical evaluation included the Subjective Shoulder Value and Constant score. Postoperative internal rotation was categorized as type I: hand to the buttock or hip; type II: hand to the lower lumbar region; or type III: smooth motion to at least the upper lumbar region. Type I was considered "nonfunctional" internal rotation, and type II and III were fIR.

RESULTS: Preoperatively, internal rotation was classified as type I in 60 patients (25.5%), type II in 114 (48.5%), and type III in 62 (26%). Postoperatively, internal rotation was classified as type I in 70 patients (30%), type II in 86 (36%), and type III in 79 (34%). Compared with preoperative status, fIR improved significantly in OA patients (P < .001), with 49 (52.6%) classified as type II or III postoperatively. In CTA patients, there was no significant change (P = .352). In patients with MICTs, there was a significant loss in fIR postoperatively (P = .003), with 25 patients (30.8%) deteriorating to type I after having either type II or III preoperatively, and only 5 patients (6.1%) improving to either type II or III.

CONCLUSIONS: Patients who undergo RSA for primary OA have a better chance of postoperative fIR improvement. A decrease in fIR is common after RSA for MICTs.