Review Question - QID 219502

The pathological changes associated with adhesive capsulitis (frozen shoulder) are caused by the increased production of collagen and fibrosis from fibroblast proliferation (Answer 2).

Adhesive capsulitis represents a condition of the shoulder characterized by a functional loss of both passive and active range of motion. It is most frequently associated with autoimmune conditions such as diabetes and thyroid disease. The pathoanatomy involves a pro-inflammatory process caused by fibroblastic proliferation that eventually leads to joint capsular thickening, fibrosis, and adherence of the capsule to itself and the humerus that appears on imaging as a loss of the normal axillary pouch (Figure B). A clinical diagnosis can be made without an MRI in the setting of normal radiographs with painful and symmetric loss of both active and passive shoulder range of motion, with the most sensitive test being a passive external rotation deficit compared to the contralateral side. First-line treatment typically involves an intra-articular steroid injection and NSAIDs followed by a guided physical therapy program until the range of motion normalizes. However, it is important to note that the process itself is self-limited and may take up to a year or longer to fully resolve.

Cho et al. published on the biological aspect of the pathophysiology of frozen shoulder. The authors note that frozen shoulder involves several stages, which reflect the series of processes from capsular inflammation and fibrosis to spontaneous resolution of this fibrosis. This inflammatory milieu is dominated by a matrix of type I and type III collagen inhabited by fibroblasts and myofibroblasts, which is controlled by abnormal cytokine production. The authors conclude that further basic science studies that use standardized protocols are required to more narrowly identify the role of cytokines, growth factors, matrix metalloproteinases, and immune cells in the pathogenesis of frozen shoulder.

Hand et al. published on the pathology of frozen shoulder. The authors reviewed 22 patients with a diagnosis of primary frozen shoulder resistant to conservative treatment that was treated by manipulation under anesthetic and arthroscopic release of the rotator interval, at a mean time from onset of 15 months. Biopsies were taken from this site, and histological and immunocytochemical analysis was performed to identify the types of cells present. They concluded that the tissue was characterized by the presence of fibroblasts, proliferating fibroblasts, and chronic inflammatory cells.

Figure A is a normal radiograph of a left shoulder. Figure B is a fluid-sensitive, coronal MRI sequence of a left shoulder showing thicking of the rotator interval/capsular tissue and loss of the normal axillary pouch.

Incorrect Answers:
Answers 1 and 3-5: Fibroblasts are the predominant cell type involved in the pathogenesis of adhesive capsulitis.