[Connective tissue in non-union and pseudarthrosis of long bones. Part II: cavity of false joints in dogs (author's transl)].

Pseudarthrotic cavity is surrounded by joint capsule-like connective tissue as well as by the locked-up bone ends. Macroscopic and microscopic examinations indicate instability as a traumatic factor to the surrounding tissues, leading to tears and clefts covered by fibrin and erythrocyte deposits. Below, cell-layers consisting of fibroblasts and histiocytes are formed, which become comparable to stratum synoviale of normal joint especially in areas with constant mechanical stimulus like sliding and little pressure without considerable traumatic effect. Where bone ends reach like lever-arms far into the peripseudarthrotic tissue and mechanical stress of abnormal mobility is of adequate permanent traumatic effect, vascularisation is not visible and regressive, necrobiotic alterations are predominant. In areas with presumable more pressure, with little or no vascularisation, woven cartilage-like partially calcified tissues are formed. Where osteotomized bones are pressed upon each other with instability an intensive remodeling with resorption and rebuilding of bone trabeculae is visible. Muscle interposits degenerate within the continuously injured and scarcely vasculated osteotomized area, and are replaced by tight connective tissues as well as walled-in by bone trabeculae. By reforming abundant collagenous fibres the pseudarthrosis becomes more and more tight. In this way there is a reduction of the functional stimulus abnormal mobility, which induces the local connective tissue to differentiate into joint-like structures, comparable to a mechanism of "self-limitation". One animal was observed up to 48 months after osteotomy. Without therapeutic immobilisation bony consolidation and corticalisation was present in the former pseudarthrotic region, joint capsule-like tissues were no more demonstrable.