Comparison of shoulder replacement to treat osteoarthritis secondary to instability surgery and primary osteoarthritis: a retrospective controlled study of patient outcomes.

ABSTRACT

PURPOSE: We hypothesized that osteoarthritis developing after instability surgery is radiographically similar to primary arthritis and that arthroplasty provides comparable outcomes in patients with these two types of osteoarthritis. METHODS: Patients with osteoarthritis due to instability surgery (group I) and with primary osteoarthritis (group II) were included. Mean follow-up was 52.6 and 41.6 months, respectively. Hemiarthroplasties (HA) were 32% in group I and 27% in group II; total shoulder arthroplasties (TSA) were 68 and 73% respectively. Outcome measures included active shoulder mobility (anterior elevation [AAE], lateral elevation [ALE], external rotation [ER], and internal rotation [IR]), pain, Constant-Murley score, and Simple Shoulder Test. Pre-operative and post-operative radiographs were taken. Glenoid arthritis was assessed by computed tomography. RESULTS: Participants were 19 in the group I (mean age 44.5 years, 12 males, 7 females) and 30 in the group II (mean age 48.2 years, 28 males, 12 females). Both patient groups had pre-operative concentric arthritis. Group II had higher rates of A2 and B1 glenoids (p = 0.003). A longer interval from stabilization to replacement was associated with lower post-operative IR (p = 0.017) and ALE (p = 0.035). Post-operative ER and IR were higher in group I (p < 0.001 and p = 0.001, respectively). In group I, AFE and ALE were higher in HA than TSA patients (both p = 0.009). The CS and SST score increased significantly in both groups (both p < 0.001). Group II showed significantly greater humeral radiolucency (p = 0.025) and a higher rate of TSA revision to reverse prostheses compared with group I. CONCLUSIONS: Shoulder replacement provides similar clinical and radiographic outcomes in arthritis secondary to instability surgery and in primary osteoarthritis. Posterior glenoid wear is more common in primary osteoarthritis.