Epidemiology, genetics and biological factors of rotator cuff tears.

Rotator cuff disease is among the most common musculoskeletal disorders with high direct and indirect costs in industrialized countries. Not all rotator cuff tears are symptomatic. Genetics has recently been investigated as a factor involved in the pathogenesis of rotator cuff pathology. Genetic factors seem to be involved in symptom presentation and tear progression. As rotator cuff disease is multifactorial, no single gene is directly involved in the pathology. Phenotypic expression of genetic susceptibility manifests at the level of ultrastructure of the tendon. Predisposing genes may also operate through apoptosis and regenerative capacity. Studies on cellular and molecular biology are more numerous, but still incomplete, and recently have focussed on the role of apoptosis in tendinopathy, analyzing its key mediators and cellular changes. Oxidative stress is responsible for reduction of collagen synthesis. Biological investigations have identified recently new risk factors. Preliminary reports introduced the possible role of glucose as a risk factor for rotator cuff tear. Further studies are required to fully clarify the genetic and biological factors involved in rotator cuff tears.