Our five-year old daughter just came out of a hip spica cast. She has cerebral palsy and had surgery for a hip dislocation. The follow-up X-ray shows she has osteopenia. What is that and what can we do about it?

Osteopenia is the loss of bone mineral density. Osteopenia can develop anytime bone is wrapped in a cast without normal weight bearing. Weight bearing is needed to stimulate bone growth. Bone loss is an expected consequence of immobilization after orthopedic surgery.

Recently, new information has come to light about this condition. Although bone loss is expected under these conditions, the amount of bone loss is surprising. One study at the University of New Mexico looked at before and after X-rays of children undergoing surgery of the lower extremity. At least four weeks of post-operative immobilization was required.

There was a range of bone loss in the operated leg from one to 34 per cent. The nonoperated leg increased bone density slightly if the child was putting weight on it. Weight bearing is a known factor in stimulating bone growth. Therefore, weight bearing activities is the first step.

Given your daughter’s diagnosis, most likely she has a physical therapist working with her. If she is not ambulatory (walking), the therapist will set her up on a standing program. If she is upright and ambulatory, then restoring weight bearing activities and normal movement is the next step.

Vitamin D and calcium supplementation may be prescribed. Restoration of bone mineral density can take months after surgery. Your surgeon will keep an eye on her progress with follow-up X-rays.