Histological and biochemical evidence related to the collagen quality in torn rotator cuff tendons

This study investigates the histological background of torn rotator cuff tendons, evaluates the stability of newly synthesized collagen by measuring the hydro-xyproline content and attempts to correlate these findings with the clinical outcome after reconstruction of the rotator cuff. Sixty-one patients underwent reconstruction for a -rotator cuff tear. They were evaluated preoperatively with the Constant-Murley score, MRI and ultrasound. Biopsy samples were taken from chronic rotator cuff tears and histological analysis was performed. Hydroxyprolin presence was evaluated in various -tissues. Mean follow-up was 46 months. Histological analysis revealed collagen fragmentation and thinning (90.2% of patients), myxoid degeneration (88%), hyaline degeneration (50.8%), chondroid metaplasia (44.3%), calcification (24.7%), fatty infiltration (20.4%) and vascular proliferation (62.3%). Hydroxyproline was under-represented in newly synthesized collagen in 57% of patients. In the majority of the patients with a low hydroxyproline/collagen ratio the histological findings were abnormal. None of the findings was related to the clinical outcome with a statistical significance. Histological and biochemical findings reflected the poor quality of the tendon. The good clinical outcome did not depend on the histological or biochemical findings but rather on the meticulous surgical reconstruction and physical therapy.