Abstract
BackgroundPost-traumatic anterior shoulder instability patients may present histopathologic lesions within the subscapularis muscle compatible with a scarring process associated with disuse atrophy. We hypothesized that such lesions identified on intraoperative biopsy at the time of primary anterior shoulder stabilization would predict a higher risk of postoperative instability recurrence.MethodsOf 52 eligible patients (52 shoulders) who had undergone subscapularis muscle biopsy during primary anterior open labral repair and capsulorrhaphy, 35 (mean age at surgery, 27.2 years; male sex, 71.4%) were retrospectively evaluated (mean follow-up, 12.9 years; range, 10.9-14.5 years). Primary outcome was shoulder instability recurrence. Secondary outcomes included shoulder range of motion, functional scores, and radiological analysis of glenohumeral joint degenerative changes.ResultsOverall five patients (14.3%) presented shoulder instability recurrence. Twelve patients with histopathologic lesions had significantly more instability recurrence than 23 without histopathologic changes (33.3% vs. 4.3%; risk difference, 29% [95% CI 1; 57]; p = 0.038). Patients without histopathologic changes had significantly reduced external rotation with arm at side (ER1; -11.9°; p = 0.001) and with shoulder abducted to 90° (ER2; -14.9°; p = 0.001) on the operated side when compared to the contralateral side. Patients with histopathologic lesions had only ER2 significantly reduced (-8.9°; p = 0.031). There was no substantial difference regarding functional and quantitative radiological scores between both patients’ groups.ConclusionsHistopathologic changes within the subscapularis muscle at the time of primary open labral repair and capsulorrhaphy were associated with an increased risk of shoulder instability recurrence. Further investigations are needed to assess the impact of dedicated postoperative rehabilitation programs for patients presenting these lesions. Their recognition on preoperative magnetic resonance imaging should also be investigated; non-anatomical repairs could be an option in these cases.
Highlights
Post-traumatic anterior shoulder instability patients may present histopathologic lesions within the subscapularis muscle compatible with a scarring process associated with disuse atrophy
Abnormal histology is defined as histopathologic changes within the substance of the subscapularis muscle compatible with a scarring process associated with disuse atrophy
This study reports that 12.9 years after primary open labral repair and capsulorrhaphy for post-traumatic anterior shoulder instability, patients presenting with specific histopathologic changes within the subscapularis muscle at the time of surgery had a significantly increased incidence of recurrence compared to patients with normal histology (33.3% vs. 4.3%, respectively)
Summary
Post-traumatic anterior shoulder instability patients may present histopathologic lesions within the subscapularis muscle compatible with a scarring process associated with disuse atrophy. A histomorphometric study demonstrated that approximately 40% of patients with post-traumatic anterior shoulder instability presented with histopathologic lesions in the substance of the subscapularis muscle at the time of surgery [11]. These lesions were characterized by type 1 fiber predominance, interstitial fibrosis, and focal atrophy compatible with a scarring process associated with disuse atrophy. As the subscapularis muscle biomechanically acts as one of the major anterior stabilizers of the shoulder joint, there may be a subset of patients more prone to instability recurrence after surgical stabilization [11,12,13,14]
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