Cartilage regeneration after proximal tibial osteotomy for medial gonarthrosis. An arthroscopic, roentgenographic, and histologic study.

High tibial osteotomy for medial gonarthrosis was performed in 28 patients (28 knees). At the time of surgery, arthroscopy was also performed and a cartilage-bone biopsy was obtained. Postoperatively, 15 patients were randomized to a cylinder plaster cast, whereas 13 patients had a hinged cast brace for early knee mobilization. At follow-up examination, two years after surgery, 16 patients accepted an arthroscopic examination with a cartilage-bone biopsy. In overcorrected knees, cartilage regeneration was found in eight of 14 patients on the medial tibial condyle and in nine of 14 on the medial femoral condyle. The main repair feature was proliferation of fibrocartilage, which covered bone and areas of fibrillated cartilage and filled vertical clefts in hyaline cartilage. The hyaline cartilage showed an increased cellularity with numerous nests of proliferating chondrocytes. No correlation was found between clinical outcome and the degree of cartilage regeneration as observed by arthroscopy, biopsy, or roentgenography. Knees with a brace postoperatively had better knee flexion two years after surgery. No difference in cartilage regeneration was recorded between knees with a plaster cast or a cast brace postoperatively.