We report a femoral shaft fracture that reduced spastic muscle hypertonus of the affected lower limb of a child with cerebral palsy. The child was a five years old boy. He was borne with spastic quadriplegia (total body involvement). He could not sit, stand and walk by himself. The femoral shaft fracture occurred during physiotherapy. The injury itself was iatrogenic although the bones were accompanied by roentgenological bone atrophy. Such bone atrophy comes from disuse or low physical activity.

The fracture was treated by a hip spica cast. The femoral bone was shortened at the time of immobilization. After removing the cast, the spastic muscle hypertonus was apparently reduced. This instructive case suggests osteotomy as a new effective treatment for spastic hypertonus. Osteotomies would make few scars in the muscles and tendons comparing to lengthening of multiple tendons and muscles. In this case, osteotomies are believed to be a non-invasive treatment rather than other available operative procedures.