Review Question - QID 220027

The patient has rheumatoid arthritis (RA) and painful shoulder arthropathy best treated with a reverse total shoulder arthroplasty (RSA). Patients with RA who undergo RSA have an increased risk of acromial and scapular spine stress fractures.

Inflammatory arthropathies, such as RA, involve the eventual deterioration and tearing of the rotator cuff. As a result, the rate of rotator cuff tears in this patient population is higher than in those with primary osteoarthritis. Despite this fact, the most common pattern of shoulder arthritis seen in this patient population involves glenoid medialization with a central wear pattern, as opposed to the more posterior wear pattern seen in patients with primary osteoarthritis. The overall rate of acromial stress fracture reported in the literature is ~4%, with risk factors being female sex, osteoporosis, and a medialized pre-operative center of rotation. Patients with RA, thus, are at increased risk for these types of fractures due to both poor bone quality and their predominantly medialized pattern of arthritic wear.

Van der Zwaal et al. performed a prospective long-term follow-up study to determine the natural history of the rheumatoid shoulder. The authors followed 22 patients with RA over 8 years, finding that radiological evaluation showed progressive destruction of the peri-articular structures with time and that progression of joint and rotator cuff destruction was significantly associated with the Constant score. They concluded that a plain anteroposterior radiograph of the shoulder is sufficient to assess any progression of rheumatoid disease and to predict functional outcomes in the long term by using the Upward-Migration-Index (UMI) as an indicator of rotator cuff degeneration.

Miller et al. retrospectively evaluated all RTSAs performed over a nearly 7-year period to determine factors associated with early symptomatic acromial and scapular spine fractures. The authors included 335 RTSAs with a minimum of 3 months of follow-up and found that symptomatic acromial and scapular spine stress fractures were significantly more common in those with inflammatory arthritis than those without (18% vs. 5%, P = 0.016). They also found that the overall rate of fracture was highest in patients with rheumatoid arthritis (24% vs. 5.2%, P = 0.003). This led them to conclude that symptomatic acromial and scapular stress fractures were significantly more common in patients with rheumatoid arthritis and, thus, precautions should be taken in these patients.

Figure A is an AP radiograph of a shoulder demonstrating the stigmata of RA: an erosive arthropathy of the glenohumeral joint with osteophytic lipping of the glenohumeral joint margins and severe central pattern of erosion, in addition to some superior migration of the humeral head and erosive changes along the greater tuberosity suggestive of chronic rotator cuff degeneration. Figure B is a clinical photograph of the stereotypical ulnar deviation deformity of the hands associated with RA.

Incorrect Answers:
Answer 1: An increased risk of accelerated polyethylene wear has not been associated specifically with RA.
Answer 3: Dislocation represents the most common early cause of failure, but patients with RA are not specifically at increased risk in the early post-op period compared to the general population.
Answer 4: Glenoid component loosening is one of the most common overall mechanisms of failure, but is not specific to patients with RA.
Answer 5: Varus component positioning is more common with stemless implants but is not specific to patients with RA.