Bone mineral density around the knee after open wedge high tibial osteotomy measured up to 24months in 51 patients.

Abstract

To evaluate bone mineral density (BMD) and radiographic and clinical outcomes of patients with varus knee osteoarthritis treated with open wedge high tibial osteotomy (OWHTO). We hypothesised that medial condyle BMD would decrease and lateral condyle BMD would increase after OWHTO. Overall, 51 patients (mean age: 65.3years; female: 40, male: 11) treated with OWHTO were prospectively enrolled. Several angles using whole single-leg radiographs were measured preoperatively and up to 24months postoperatively. Five square tibial regions of interest (ROI) located below the proximal tibia as T1-T5 from medial to lateral regions and two square femoral ROI as F1 and F2 from medial and lateral regions, respectively, were defined. M/L BMD ratio was used to define the medial-to-lateral condyle BMD ratio. Femoral condyle BMD (F1 and F2) around the knee, as well as lumbar spine, and ipsilateral and contralateral femoral neck BMD, were measured before OWHTO and 3, 6, 12 and 24months after OWHTO using dual-energy X-ray absorptiometry. Furthermore, tibial condyle BMD (T1-T5) around the knee was measured before and 24months after OWHTO. Clinical outcomes were evaluated using the Knee Society knee and function scores, the Knee Injury and Osteoarthritis Outcome Score, and the Lysholm score preoperatively and 24months postoperatively. A power analysis was performed. F1 BMD decreased by 19.2% from before to 3months postoperatively. F2 BMD did not change up to 24months after OWHTO. Femoral M/L BMD ratio decreased by 22.2% 3months after OWHTO. T1 BMD and tibial M/L BMD ratio decreased, whilst T3, T4 and T5 BMD increased 24months after OWHTO. Mean hip-knee-ankle angle (HKA) and weight-bearing line ratio were corrected from - 6.8° to 4.5° and 14.7 to 60.7%, respectively, postoperatively. Lumbar spine BMD did not change up to 12months postoperatively. Ipsilateral femoral neck BMD decreased up to 6months after OWHTO. Medial femoral condyle BMD decreased rapidly within 3months and continued to decrease up to 12months, but lateral femoral condyle BMD did not change after OWHTO. BMD measurements around the knee condyle enabled the evaluation of the changes in stress distribution before and after OWHTO with accelerated rehabilitation. II.