Comparison of results of medial opening-wedge high tibial osteotomy with and without subchondral drilling.

PURPOSE: The purposes of this study were to compare the results of medial opening-wedge high tibial osteotomy (MOWHTO) with and without subchondral drilling and to assess the formation of fibrocartilage at 2 years postoperatively.
METHODS: Patients were divided into 2 groups. Thirty knees were treated with osteotomy and subchondral drilling (group 1), and 31 knees were treated with osteotomy alone (group 2). Clinical evaluations were performed by use of Knee Society scores preoperatively and at 2 years postoperatively. For evaluation of cartilage degeneration, the International Cartilage Repair Society grading system was used for arthroscopic grading on initial arthroscopy during high tibial osteotomy. The patients underwent a second-look arthroscopic evaluation of the articular cartilage at the time of removal of the plate, an average of 2 years after the initial osteotomy. For evaluation of formation of fibrocartilage on second-look arthroscopy, the articular cartilage was classified as having either no change from initial surgery (grade I) or white scattering with fibrocartilage, partial coverage with fibrocartilage, or even coverage with fibrocartilage (grade II). In addition, maturation of the appearance of the cartilage was defined. The appearance was considered mature if the chondral defects were evenly covered with fibrocartilage. It was considered immature if there was white scattering or only partial coverage with fibrocartilage.
RESULTS: In group 1 the mean Knee Society knee score and function score were 67.3 ± 8.2 points and 66.5 ± 14.3 points, respectively, preoperatively. At 2 years postoperatively, they improved to 91.2 ± 6.4 and 92.8 ± 10.0, respectively (P = .001 and P = .001, respectively). In group 2 the mean Knee Society knee score and function score were 63.7 ± 13.9 points and 66.8 ± 9.1 points, respectively, preoperatively. At 2 years postoperatively, they improved to 92.5 ± 5.3 points and 92.2 ± 8.0 points, respectively (P = .001 and P = .001, respectively). There were no significant differences in the postoperative Knee Society knee score and function score at 2 years' follow-up between the groups (P = .389 and P = .806, respectively). Grade II regeneration was achieved in the medial femoral condyle articular cartilage in 100% of knees in group 1 and 94% of knees in group 2 (P = .492). Maturation of the cartilage was found in the medial femoral condyle articular cartilage in 10% of knees in group 1 and 3% of knees in group 2 (P = .354). There was no significant difference in the formation of fibrocartilage between the groups.
CONCLUSIONS: Subchondral drilling had no effect on the outcome at 2 years after MOWHTO. In addition, there was no significant difference in the formation of fibrocartilage with or without subchondral drilling. Therefore subchondral drilling is not necessary after MOWHTO. LEVEL OF EVIDENCE: Level III, retrospective comparative study.