[The articular capsule in idiopathic hypertrophic osteoarthropathy (author's transl)]

The results of clinical roentgenological, cytological examinations as well as the histological examination of biopsy material with electron microscopy are reported for two cases of primary idiopathic hypertrophic osteoarthropathy. In both cases, a watchglass nail was present in the hands and feet; clubbed, distended knee, ankle and wrist joints; appositional enlargement of the shaft of the long bones; the hands and the phalanges of the foot as well as arthralgia and an hyperhidrosis. The morphological examination of biopsy material confirmed the already established increased periosteal bone enlargement. In addition, a fibrosis of the synovial membrane with thickening of the fibrous tissue matrix and increased vascularization of the synovial membrane could be established. Inflammatory processes could be excluded. The reported findings could be attributed to a generalized defect in hormonal or enzymatic regulation of the mesenchym. The vascularization can be explained as a reaction to the lengthening of the transit route between vessels and joint lumen. The thickening of the connective tissue together with the lengthening of the transit route is considered to be an essential causal factor in the arthralgic complaints of strain in hypertrophic osteoarthropathy.