LEG LENGTHENING AND GLYCOSAMINOGLYCANS IN THE RABBIT KNEE

We investigated the effects of tibial lengthening by callotasis on gly cosaminoglycan (GAG) metabolism of the knee articular cartilage in 30 rabbits. The distraction rate was 1 mm per day. On the right side, the daily distraction was in 2 steps, while on the left it was in 120 ste ps. The animals were divided into 3 subgroups based on length gain; 10 , 20, and 30 percent, respectively. The knee joint fluid and medial ti bial cartilage were examined by quantitative analysis of the GAG conte nt and/or synthesis. The immunoreactivity for chondroitin sulfate in t he cartilage was also examined by immunohistochemistry. For all length gains, the GAG concentration in the synovial fluid was higher on both sides than in controls, with no difference between sides. The GAG con tent and synthesis in the cartilage on the 2-step side decreased gradu ally with increasing length. On the 120-step side, the content did not differ from control values in any length gain, and the level of synth esis at 20 and 30 percent lengthening was higher than the control leve l. Our findings indicate that the alterations in GAG metabolism are at tributable to increased mechanical stress on the articular cartilage, suggesting a moderate increase on the 120-step side compared to an exc essive one on the 2-step side.