Isolation of bone from muscles prevents the development of experimental callus-like heterotopic bone. A study of the interaction of bone and muscle in new bone formation.

Heterotopic bone (HB) has previously been provoked in the compartment of the profundus part of the vastus intermedius muscle (VIP) by manipulation of the rabbit knee immobilized in extension. The authors isolated the femoral bone of adult rabbits with a permeable or an impermeable polymer membrane to investigate the interactions of bone, periosteum, and muscle in callus-like HB formation, using the HB model. Heterotopic bone developed beside but not over the membrane if isolation was carried out before the immobilization-manipulation period, regardless of the type of membrane used. In cases where the femoral bone was isolated from the muscle by insertion of the tubular membrane one to two weeks after the immobilization-manipulation had begun, there was HB formation over and beside the membrane. No HB developed under the membrane in any of the cases of femoral bone isolation. Thus direct and extensive contact between bone and muscle appears to be essential at the onset of formation of experimental HB. An intertissue exchange of soluble substances derived from bone or muscle, however, does not seem to play an essential role here. After the onset of HB formation, its further development will not be prevented by subsequent isolation of muscle and bone. The study elucidates the interaction between bone and adjacent muscles and the results may be valuable in further investigations on HB and fracture healing.