The Effect of Medial Opening and Lateral Closing High Tibial Osteotomy on Leg Length

Background: High tibial osteotomy (HTO) is a common treatment for medial compartment arthritis of the knee in younger, more active patients. An HTO also potentially affects leg length. Mathematical models predict that the osteotomy type (medial opening-wedge vs lateral closing-wedge) and the magnitude of the correction determine the change in leg length, but no in vivo studies have been published. Purpose: This study was undertaken to quantify and compare leg-length change after opening-wedge and closing-wedge HTO. Study Design: Cohort study; Level of evidence, 3. Methods: Thirty-two medial opening-wedge and 32 lateral closing-wedge HTOs were selected from patients treated at the authors' institution. Preoperative and postoperative coronal plane alignment and leg length were measured and surgical details were collected. Results: The 64 osteotomies were performed at an average age of 57 years. The mean opening wedge was 9.3 mm and the mean closing wedge was 8.0 mm. Mean knee alignment changed from 174A preoperatively to 183A postoperatively in both groups. In the medial opening-wedge group, entire leg length changed from 836.3 +/- 63.5 mm to 841.8 +/- 64.1 mm, an increase of 5.5 +/- 4.4 mm (P < .0001). Tibia length changed from 368 +/- 30.9 mm to 372.3 +/- 31.2 mm, an increase of 4.3 +/- 2.3 mm (P < .0001). In the lateral closing-wedge group, entire leg length changed from 840.6 +/- 51.5 mm preoperatively to 837.9 +/- 52.0 mm postoperatively, a decrease of 2.7 +/- 4.0 mm (P = .0008). Tibia length changed from 365.1 +/- 23.2 mm to 361 +/- 22.9 mm, a decrease of 4.1 +/- 2.9 mm (P < .0001). The difference in mean leg-length change between opening-wedge and closing-wedge osteotomies was 8.2 +/- 5.9 mm (P < .0001). Conclusion: Both medial opening-wedge and lateral closing-wedge HTO can result in significant leg-length change, but changes are generally less than mathematical models predict.