Effect of high tibial osteotomy on joint loading in symptomatic patients with varus aligned knees: a study using SPECT/CT.

ABSTRACT

PURPOSE: The purpose was to prospectively evaluate the outcome, in particular the SPECT/CT bone tracer uptake (BTU) after high tibial osteotomy (HTO) due to symptomatic varus malalignment. It was the hypothesis that the BTU after HTO decreases in the medial compartment, clinical outcome and the degree of correction correlates with BTU and asymptomatic patients after HTO reveals a significantly decreased BTU in the medial subchondral areas. METHODS: Twenty-two consecutive patients with 23 knees undergoing medial opening-wedge HTO for medial compartment overloading were assessed pre- and postoperatively (12 and/or 24 months) using Tc-99m-HDP-SPECT/CT including our 4D-SPECT/CT protocol. BTU was quantified and localized to specific biomechanically relevant joint areas. Maximum absolute and relative values (mean ± standard deviation, median and range) for each area were recorded. Pre- and postoperative mechanical alignment was measured. At 24 months after HTO, the WOMAC score was used. RESULTS: A significant decrease of BTU in the medial subchondral zones after HTO was found (preoperatively to 12 and 24 months postoperatively, p < 0.01). BTU normalized in all asymptomatic patients within 24 months. This decrease was partly seen in the lateral compartments, but significantly higher in the medial compartments (p < 0.0001). A significant increase of the BTU was noted in zones directly adjacent to the plate or within the osteotomy zone (p < 0.01). Decreased BTU was observed in osteotomy zones at 24 months postoperatively following higher uptake values at 12 months postoperatively. The average valgus correction of the tibiofemoral angle was 5.9° ± 2.8°. Less stiffness correlated significantly with a higher decrease in BTU (p < 0.05). Higher postoperative BTU significantly correlated with more pain (p < 0.05). No statistical significant associations between BTU and alignment correction were found. CONCLUSION: In patients with medial compartment, overloading due to varus malalignment HTO led to a significant decrease in BTU in the medial joint compartments. SPECT/CT BTU patterns and intensity in these patients pre- to 12 and 24 months postoperatively were seen. These correlated significantly with pain and stiffness. Hence, SPECT/CT could be used for assessment of adequate correction and healing after HTO. SPECT/CT could be further used to identify the optimal individualized correction for each patient and clinical scenario. CLINICAL EVIDENCE Diagnostic prospective study, Level II.