Offloading effect in the unoperated contralateral knee after unilateral medial open wedge high tibial osteotomy: A SPECT/CT analysis.

ABSTRACT

BACKGROUND: An open wedge high tibial osteotomy (OWHTO) may lead to gait alteration, which change the contact loading in the contralateral knee, while clear evidence about the impact on contralateral knee still lacks. The purpose of the current study was to evaluate the change in scintigraphic uptake using SPECT-CT in the medial compartment of the contralateral knee following OWHTO. METHODS: Contralateral radiographic measurements were performed for patients with medial osteoarthritis and varus malalignment of >5° treated with OWHTO in this retrospective analysis. The medial compartmental changes according to SPECT/CT analysis before and 1-year after OWHTO were evaluated on the contralateral side. RESULTS: The study comprised 72 patients. The mean preoperative mechanical femorotibial angle was a mean varus of 7.6° (range, 5.1° - 13.0°), corrected to a mean valgus of 2.5° (range, 1.9° - -8.5°) postoperatively. The average grading of the scintigraphic uptakes in the medial compartment of the contralateral knee was significantly decreased 1 year postoperatively than after the surgery (from 2.8 ± 0.4 to 2.1 ± 0.6, p < 0.001). Measurable differences in varus alignment on radiographs of the contralateral limb were identified. The preoperative mechanical axis value decreased from 8.0° ± 2.4° to 6.7° ± 2.6° at the 3-month postoperative visit (p = 0.011). The overall decrease in varus alignment remained at the 2-year final postoperative follow-up. CONCLUSION: Alignment correction by OWHTO results in reducing scintigraphy uptakes in medial compartment and improvement in mechanical alignment of the contralateral knee. LEVEL OF EVIDENCE Therapeutic Level IV.