In our previous studies temporary manipulation of immobilized rabbit hindlimbs resulted in heterotopic cartilage and bone formation (HCB) in muscles (myositis ossificans). HCB developed mainly in the deep, profundus portion of the vastus intermedius muscle (VIP), and to a lesser extent in the more superficial muscles, vastus intermedius superficialis (VIS) and in the vastus lateralis (VL). Immobilization alone led to morphological changes, and also to marked changes in muscle element levels, but never to HCB. In this study, the levels of eight elements in these three muscles (Ca, Cu, Fe, K, Mg, Na, Zn, and P) were studied to elucidate the pathogenesis of our experimental model of HCB. The right hindlimb of 15 rabbits was immobilized with the knee in extension and manipulated once daily for a few minutes. Element levels in the VIP, VIS and VL were analyzed after three and seven days of treatment employing a novel ICP technique. The results revealed marked changes in all levels of the muscle elements, except for Fe in the three muscles, but the largest changes occurred in the VIP. Zn levels increased markedly in the VIS and VL, but decreased significantly in the VIP. After treatment, both K/P and Mg/P ratios decreased significantly and the Mg/K ratio increased in the VIP, but not in the other muscles.Changes in muscle element concentrations may play an essential role in the development of myositis ossificans, and the determinations of these elements may offer good parameters in future investigation of the pathogenesis of HCB, immobilization-induced necrosis and in developing preventive and curative methods for these often harmful conditions.
