Two theoretical concepts. I: The theoretical basis for heterotopic bone formation in paralyzed limbs due to brain or cord problems, and the sparing effects on arthritis in paralyzed limbs.

It is suggested that intrinsic magnetic or electrical forces in normal extremities, in extremities paralyzed as a result of brain or spinal cord or nerve damage, and in paralytic extremities of patients with arthritis be measured, if possible. The findings may lead to a therapeutic or preventative approach to problems related to heterotopic ossification and to arthritis.