Primary frozen shoulder: global capsular stiffness versus localized contracture.

Stiffness in primary (idiopathic) frozen shoulders has been attributed to a global fibroplasia of the capsule despite the fact surgical release of the capsule at the rotator interval and of the coracohumeral ligament restores motion in almost all patients. Occurrence of vimentin, a cytocontractile protein known to be present in Dupuytren's contracture and in club-feet, has been reported in resection specimens of anterior capsular structures. We hypothesized vimentin would occur only in the anterior structures but fibroplasia would occur throughout the capsule. Tissues removed from four patients were stained with antibodies against vimentin, allowing us to confirm its presence in only in anterior capsular structures, supporting our first hypothesis contracture is due to a selective involvement of the anterior capsule. Staining the sections against types I and III collagen permitted the detection of both collagens in the anterior and the posterior capsular structures and thus confirmed our second hypothesis that fibroplasia involves the entire joint capsule. Therefore it seems, in patients with primary frozen shoulder, fibroplasia and contracture are two distinct processes.