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.
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.
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.
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.