[Changes of the subchondral osteosclerosis in the femoral and tibial chondyles during long-term after high tibial osteotomy for medial compartmental osteoarthritis of the knee].

Osteosclerosis of the subchondral bone was measured by densitometry on plain roentgenograms in 55 medial compartmental osteoarthritic knees of 40 patients who underwent high tibial osteotomy for correction of varus deformity. The osteosclerosis value of the medial side of the knee to that of the lateral side (Medial/Lateral ratio) was calculated and used as a parameter. Medial/Lateral ratios of the osteosclerosis were increased from 0.90 +/- 0.15 preoperatively to 0.99 +/- 0.20 (p < 0.05) postoperatively in 2 mm proximal area from the joint surface of the femur, from 0.95 +/- 0.15 to 1.04 +/- 0.21 (p < 0.05) in 7 mm proximal area from the joint surface of the femur, and from 0.87 +/- 0.14 to 0.95 +/- 0.13 (p < 0.05) in 2 mm distal area from the joint surface of the tibia within 3 years. The increase of the ratio was noted more than 7 years after osteotomy in the cases with standing femoro-tibial angle (FTA) less than 165 degrees. This is interpreted to mean that osteosclerosis of the medial chondyle decreased as compared with that of the lateral condyle after correction of varus deformity. More than 7 years after high tibial osteotomy, minus straight line relationship was found between Medial/Lateral ratio and FTA in 2 mm proximal area from the joint surface of the femur of the case with FTA less than 175 degrees with coefficient of correlation -0.408 (p < 0.05) and in 2 mm distal area from the joint surface of the tibia with coefficient of correlation -0.437 (p < 0.01). From these results, the sufficient correction of varus deformity is considered to be one of the most important factor in the treatment of osteoarthritis of the knee.