Osteopenia after osteotomy of the tibia.

Previous studies have shown a persisting bone mineral loss of 25% at the distal femoral and proximal tibial metaphysis after fractures of the tibia. This is likely to increase the risk of later fracture. In the present study, the evolution of regional osteopenia after valgus osteotomy of the proximal tibia was investigated. In 20 patients, the bone mineral content (BMC) on both sides was determined by single-energy photon absorptiometry in the distal metaphysis; distal, mid, and proximal diaphysis of the tibia; and the distal metaphysis and diaphysis of the femur preoperatively and 6, 16, 34, 52, and 104 weeks postoperatively. A moderate fall in BMC was found at all measured levels of the extremity. In the tibia, the greatest fall in BMC (10%) was seen in the diaphysis near the osteotomy, but a considerable regeneration of bone mineral occurred later. A persisting loss was found in the distal tibial (8%) and femoral (11%) diaphysis. At these levels a fall in BMC on the contralateral side led to similar values on the two sides after 2 years.