The role of biochemical factors in the onset and natural history of rotator cuff disease is not fully understood, but it is generally recognised that they could induce tendon damage in association with mechanical and vascular factors. In this study, 5 biochemical parameters were analysed (total protein concentration, matrix metalloproteinase (MMP)-2 or gelatinase A, MMP-9 or gelatinase B, type I collagen telopeptides, hyaluronic acid) in the synovial fluid (SF) aspirated from the gleno-humeral joint of 29 patients undergoing surgical therapy for rotator cuff lesions. Four different groups of patients were identified according to the severity of the lesion: partial tear of the rotator cuff, full thickness tear involving <or-1 tendon, full thickness tear involving >1 tendon and cuff tear arthropathy (CTA). The total SF protein concentration progressively increased with loss of integrity of the rotator cuff, reaching the highest levels in CTA. The absolute enzymatic activity of gelatinases was greater in full thickness tears than in partial tears, while it decreased in CTA. Conversely, the ratio between gelatinases and total protein content reached the highest level in partial tears and then progressively decreased. Collagen I telopeptides were significantly increased in full thickness tears and CTA, whereas the levels of hyaluronic acid decreased with worsening of rotator cuff disease. These findings support the hypothesis that gelatinases, which are involved in physiological tendon remodelling, intervene in the evolution of rotator cuff disease, too. Increased levels of type I collagen telopeptides give evidence that tendon tears are associated with an anatomic loss of tendon tissue and not with simple tendon retraction.
