Is acromial morphology different in patients with eccentric glenohumeral osteoarthritis?

Acromial morphology has been implicated as a potential contributor to eccentric glenohumeral osteoarthritis (GHOA), leading to the development of novel procedures, including scapular spine corrective osteotomies. However, there remains a substantial gap in knowledge on the relationship between acromial morphology and eccentric GHOA. This study utilized a comprehensive three-dimensional semiautomated analysis of acromial morphology to assess its association with eccentric GHOA patterns.

A retrospective chart review was conducted to identify symptomatic patients with GHOA undergoing evaluation for total shoulder arthroplasty. Patients were classified as having eccentric vs. concentric GHOA based on the Walch criteria. A sample of healthy controls was also included from a previous investigation. Three-dimensional bone models of the scapula were reconstructed from computed tomography scans, and scapular morphology was calculated using custom software to measure sagittal acromial tilt, coronal acromial tilt, axial acromial tilt, lateral acromial ratio, glenoid inclination, glenoid version, and acromial coverage relative to the scapular body. These morphology variables were compared between groups using analysis of covariance, adjusting for sex.

Ninety-eight patients with GHOA (mean age: 64.7 years; 26.5% female; Walch A: 26, Walch B: 72) and 40 healthy controls (mean age: 55.2 years; 65% female) were included. Patients with Walch B glenoids were 15.0° ± 1.4° more retroverted than patients with Walch A glenoids (P < .01) and 14.9° ± 1.6° more retroverted than healthy controls (P < .01). Patients with Walch B (-8.5° ± 0.9°) had more inferiorly inclined glenoids than those with Walch A (-4.1° ± 1.5°), and both groups had more inferior inclination than healthy controls (1.3° ± 1.2°; P ≤ .03). Patients with GHOA exhibited less posterior and overall acromial coverage than healthy controls (P < .01). Patients with Walch B glenoids had a 6.9° ± 1.6° higher sagittal acromial tilt compared to healthy controls (P < .01), and no differences were found between groups in coronal tilt or axial tilt. Patients with Walch B glenoids had less lateralized acromions than those with Walch A glenoids and healthy controls (P < .01).

There is significant variability in acromial morphology among patients with GHOA compared to healthy controls. While the effect sizes are small, patients with Walch B glenoids had flatter acromion relative to healthy controls and less lateralized acromion relative to both healthy controls and Walch A glenoids. Further research is needed to understand the causative relationship between acromial morphology and the development of eccentric GHOA.