High tibial osteotomy to neutral alignment improves medial knee articular cartilage composition

Purpose The purpose of this study was to: (1) test the hypothesis that HTO improves articular cartilage composition in the medial compartment without adversely affecting the lateral compartment and patella, and; (2) explore associations between knee alignment and cartilage composition after surgery. Methods 3T MRI and standing radiographs were obtained from 34 patients before and 1-year after HTO. Articular cartilage was segmented from T2 maps. Mechanical axis angle (MAA), posterior tibial slope, and patellar height were measured from radiographs. Changes in T2 and radiographic measures were assessed using paired t tests, and associations were assessed using Pearson correlation coefficients. Results The mean (SD) MAA before and after HTO was − 6.5° (2.4) and 0.6° (3.0), respectively. There was statistically significant shortening [mean (95%CI)] of T2 in the medial femur [− 2.8 ms (− 4.2; − 1.3), p < 0.001] and medial tibia [− 2.2 ms (− 3.3; − 1.0), p < 0.001], without changes in the lateral femur [− 0.5 ms (− 1.6; 0.6), p = 0.3], lateral tibia [0.2 ms (− 0.8; 1.1), p = NS], or patella [0.5 ms (− 1.0; 2.1), p = NS). Associations between radiographic measures and T2 were low. 23% of the increase in lateral femur T2 was explained by postoperative posterior tibial slope ( r = 0.48). Conclusion Performing medial opening wedge HTO without overcorrection improves articular cartilage composition in the medial compartment of the knee without compromising the lateral compartment or the patella. Although further research is required, these results suggest HTO is a disease structure-modifying treatment for knee OA.