[Orthopedic aspects of Crohn disease. Examples of extra-intestinal organ manifestations].

Articular changes in Chron's disease represent extraintestinal organic manifestations which generally take the form of so-called enteropathic synovitis. Articular alterations - diagnosed as non-specific arthritis in the great majority of cases--may precede the intestinal disease. In very rare cases it can be shown that the joints display histological changes typical of Morbus Crohn. The etiology and pathophysiological mechanisms of the articular changes are not clear. Probable factors are: autoimmune disease, stimulation of the immunological system by exogenous antigens, induction of a self-sustaining inflammatory process, and demonstrable circulation of antigen-antibody complexes. Genetic factors seem to play a role (familial disposition). A pure "colonic Crohn" (= colitis granulomatosa) leads to a higher degree of articular alteration than a pure "small-intestine Crohn" (= ileitis terminalis). The joints preferentially affected are in the region of the lower extremities (knee and ankle joints). Concomitant Bekhterev's disease (spondylitiis ankylopoietica) is found in 7-10% of cases. Osteomyelitis represents a rare and serious complication: it can appear in the course of chronic Chron's disease (mainly with intestinal fistulas), especially in the region of the pelvic bones. Further aspects of interest from an orthopedic viewpoint are hypertrophic osteoarthropathy with periossal neoformation, granulomatous changes in the bone itself, and aseptic osteonecrosis.