Multiple sclerosis is associated with increased shoulder dislocations and aseptic loosening following reverse shoulder arthroplasty: a propensity matched analysis.

Introduction: Multiple sclerosis (MS) is a chronic neurological condition characterized by muscle spasticity, which may influence the outcomes of reverse shoulder arthroplasty (RSA) for glenohumeral osteoarthritis or proximal humerus fractures. It is unclear whether implant complications and revision rates are increased in patients with MS. The aim was to compare 2-year implant complications and 90- day costs in MS patients undergoing RSA.

Methods: A retrospective analysis was performed using the PearlDiver database (2010-2022). MS patients (N = 764) who underwent RSA either for glenohumeral osteoarthritis or proximal humerus fractures were identified and matched to patients without MS (N = 3,682) in a 1:5 ratio by age, sex, and comorbidities. Two-year implant complications, including shoulder dislocations, aseptic loosenings, periprosthetic joint infections (PJIs), periprosthetic fractures, and all-cause shoulder arthroplasty revisions, were compared between the two groups using multivariable logistic regressions. Costs were evaluated over a 90 day episode of care interval. P values < 0.05 were significant.

Results: The proportion of patients who underwent RSA for proximal humerus fracture was not different between patients with and without MS (12.4% vs. 15.1%; P = 0.063). Patients had no difference in overall comorbidity burden (ECI: 8.1 vs. 8.0; P = 0.39). At 2 years, MS patients were associated with significantly higher rates and odds of shoulder dislocations (OR: 1.94, P = 0.006) and aseptic loosenings (OR: 1.93, P = 0.044). There was no significant difference in all-cause revisions (OR: 1.39, P = 0.183), PJIs (OR: 0.72, P = 0.326), or periprosthetic fractures (OR: 1.20, P = 0.773) compared to controls. Patients with MS incurred significantly higher 90 day episode of care costs: $11,437 vs. $10,321; P = 0.0002.

Conclusions: MS patients undergoing RSA were associated with significantly higher rates of shoulder dislocations and aseptic loosening compared to controls. Additionally, MS patients incurred significantly higher 90-day episode of care costs. These findings underscore the need for careful perioperative planning and long-term monitoring in MS patients undergoing RSA.

Level of evidence: III.