Abstract
Introduction:
High tibial osteotomy (HTO) is a common treatment for medial compartment arthritis of the knee in younger, more active patients. The HTO shifts load away from the degenerative medial compartment and into the lateral compartment. This change can be accomplished with either a lateral closing or a medial opening wedge HTO. An HTO also potentially affects leg length. Mathematical models predict that the osteotomy type (opening versus closing) and the magnitude of the correction determine the change in leg length, but no in vivo studies have been published. The purpose of this study is to quantify and compare leg length change following opening and closing wedge HTO.
Study Design:
Retrospective cohort study – Level III evidence
Methods:
Thirty-two medial opening and 32 lateral closing HTO's were selected from patients treated at our institution between 2006 and 2009. Pre-operative and one-year post-operative full-length lower extremity radiographs were obtained along with operative reports. Pre- and post-operative coronal plane alignment and leg length were measured and surgical details were collected.
Results:
The 64 osteotomies were performed in 62 patients (43 male, 19 female) at an average age of 57 years. The mean opening wedge was 9.3 mm (range: 5 to 17 mm) and the mean closing wedge was 8.0 mm (range: 6 to 10 mm). Knee alignment changed from a mean of 174 degrees pre-operatively to a mean of 183 degrees post-operatively in both groups. In the medial opening wedge group, total leg length was found to increase from 836.3 ± 63.5 mm pre-operatively to 841.8 ± 64.1 post-operatively, a change of 5.5 ± 4.4 mm (p < 0.0001). A significant correlation was found between the amount of correction and the increase in overall leg length (r2 = 0.21, p = 0.009). In the lateral closing wedge group, total leg length was found to decrease from 840.6 ± 51.5 mm pre-operatively to 837.9 ± 52.0 post-operatively, a decrease of 2.7 ± 4.0 mm (p = 0.0008). No correlation was found between the amount of correction and the change in overall leg length. The difference in mean leg length change between opening and closing wedge osteotomies was 8.2 ± 5.9 mm (p < 0.0001).
Conclusions:
Medial opening wedge HTO can result in significant leg lengthening depending on the degree of opening. Leg length changes associated with lateral closing wedge HTO are generally smaller. Both techniques results in less leg length change than mathematical models predict. Pre-operative leg length discrepancy should be considered when choosing an osteotomy technique.
