Reliability of stemless shoulder arthroplasty in rheumatoid arthritis: observation of early lysis around the humeral component.

Purpose: To evaluate whether stemless shoulder implants in rheumatoid arthritis (RA) patients provide comparable functional outcomes to patients with osteoarthritis or post-traumatic arthritis. In addition, the study assessed for differences in incidence of radiolucent lines or proximal humeral bone loss during radiographic follow-up.

Methods: Consecutive stemless shoulder arthroplasties performed in RA patients and a matched control group were retrospectively identified between February 2012 and 2018. Thirty-five patients were included in each group: 24 total shoulder arthroplasty (TSA) and 11 hemiarthroplasty (HA). Patients were evaluated annually using the Oxford Shoulder Score (OSS) and radiographically.

Results: The mean OSS significantly improved in all groups until 24 months. The mean improvement for RA TSA and HA patients at 24 months was 19.86 (95% CI 10.66-29.05, p = 0.0004) and 19.71 (95% CI 7.33-32.31, p = 0.0084), respectively. The mean improvement in the control TSA and HA patients at 24 months was 20.86 (95% CI 17-24.71, p = 0.0001) and 17.86 (95% CI 1.36-34.35, p = 0.0381), respectively. During the study period, two patients in the RA TSA group (8%), one patient in the control TSA group (4%) and one patient in the control HA group (9%) required revision. The proportion of progressive proximal humeral bone loss after TSA was 33% in the RA group and 13% in the control group.

Conclusion: Stemless shoulder implants can provide significant improvement in functional scores in RA patients in the short term. However, early bone loss around the humeral implant is a concern and the authors recommend long-term clinical and radiological follow-up.