Serial Quantitative Assessment of Load Redistribution After Medial Open-Wedge High Tibial Osteotomy

BACKGROUND: The maximum standardized uptake value (SUV(max)), as determined on combined single-photon emission computed tomography and conventional computed tomography (SPECT/CT), can be an indicator of biomechanical changes due to the load redistribution effect after medial open-wedge high tibial osteotomy (MOW-HTO). PURPOSE/HYPOTHESIS: The purposes of this study were to (1) analyze serial changes in the SUV(max) in the medial, lateral, and patellofemoral compartments after MOW-HTO and (2) identify the contributing factors that affect changes in the SUV(max). The hypotheses were that (1) an elevated SUV(max) in the medial compartment would be transferred to the lateral compartment because of the load redistribution effect and (2) there would be contributing factors that cause SUV(max) changes. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Included were 67 knees that were treated with biplanar MOW-HTO between March 2019 and December 2020. SPECT/CT was performed immediately after surgery and at 3 months and 1 year postoperatively to determine the serial load redistribution effect of MOW-HTO. The Pearson correlation coefficient was used to evaluate the relationship between SUV(max) and radiological parameters, and subgroup analyses were conducted to compare the SUV(max) according to associated cartilage procedures and the weightbearing line ratio (WBLR). RESULTS: The SUV(max) in the medial and lateral compartments increased at 3 months but decreased at 1 year postoperatively. The load redistribution effect was most prominent in the anterior zones of the femur (medial: P = .041; lateral: P = .012). In the patella, the SUV(max) decreased in both the medial and the lateral zones at all follow-up times (P < .001 for all). The SUV(max) in the anterolateral and posterolateral articular zones of the femur increased with a greater preoperative WBLR (r = 0.256, P = .039; and r = 0.261, P = .036, respectively). Patients who underwent an associated cartilage procedure had a significantly higher SUV(max) in the anteromedial and posteromedial articular zones of both the femur and the tibia at 1 year postoperatively (P ≤ .002 for all). CONCLUSION: After MOW-HTO, the unloading effect in the anteromedial articular zone of the femur was the most significant. A greater SUV(max) in the lateral zones of the femur was observed in cases of overcorrection. The SUV(max) in the medial zones was higher postoperatively in patients with associated cartilage procedures.