Longitudinal changes in subchondral bone structure as assessed with MRI are associated with functional outcome after...

The primary objective of this study was to evaluate the effects of high tibial osteotomy (HTO) on subchondral bone structure assessed with magnetic resonance (MR)-based trabecular bone imaging and the correlations of these effects with functional outcome and clinical symptoms.

Patients with varus malalignment (6.2±2.2°) and without a history of knee surgery (n=22; 3 women; 48.7±10.3 years) were included into this prospective study. 1.5T MR imaging was performed before and on average 1.5 years after HTO (amount of correction 4.7±2.5°) and histomorphometric parameters of the trabecular bone were calculated for the medial/ lateral tibia and femur. Functional outcome was assessed with validated scores focusing on sports activity including the Lysholm Score, Tegner Activity Scale and the adapted Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Score.

Apparent trabecular number significantly decreased in all compartments of the tibiofemoral joint when comparing values before and on average 1.5 years after HTO (P<0.05 for all). Decrease in apparent trabecular number was significantly higher within the medial tibia compared to the lateral compartment (mean difference -0.24 mm^-1 (95% confidence interval (CI): -0.33, -0.14 mm^-1); P<0.001). Apparent trabecular bone thickness significantly increased within 1.5 years after HTO in the lateral femur (P=0.002) and tibia (P <0.001). The Lysholm Score and Tegner Scale demonstrated an improvement of functional outcome, and the adapted WOMAC demonstrated an improvement of pain, stiffness and physical function within 1.5 years after HTO (P<0.01), with the improvement of WOMAC correlating significantly with changes in trabecular bone thickness within the medial tibia (r= -0.48; P=0.01).

These findings indicate a reversal of the previous subchondral bone alterations in patients with varus malalignment after undergoing HTO, while pronounced subchondral changes were associated with a better functional outcome.

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