One year follow-up of a case series using the iBalance medial opening wedge HTO system and an accelerated rehabilitation program

OBJECTIVES: To investigate the clinical outcome and postoperative alignment changes changes to following computer navigated medial opening wedge HTO using the iBalance HTO system METHODS: We performed a prospective observational series at a single centre of 20 consecutive patients undergoing computer navigated high tibial osteotomy by a single surgeon. The surgical device used to maintain the osteotomy was the Arthrex iBalance® HTO system. We compared preoperative and postoperative ROM, WOMAC, Lysholm, IKDC, alignment and the inferred tibial slope. We also measured the tibiofemoral angle on long leg weight bearing plain radiographs at 2 weeks, 6 weeks, 3 months and 1 year and calculated any change from the initial correction measured at 2 weeks to asses any loss of correction over 1-year time frame. We also correlated clinical outcome with loss of correction. RESULTS: Regarding intraoperative results, the mean navigated correction to HKA was 5.4°±1.3°. No significant change was found to the knee sagittal angle posteroperatively (pre op mean 0.1°±4.4°, post op mean 0.81°±5.1°; p> 0.05). No significant change was found to the post operative ROM (pre op mean 125.4°±41.5°, post op mean 123.9°±34.4°; p> 0.05). The IKDC, Lysholm and WOMAC scores showed a significant difference, between 6 week to 3 months and 3 months to 6 months follow-up. After this time point scores did not show and statistical significant difference. The IKDC, Lysholm and WOMAC scores all demonstrate a general improvement over 12 months. One patient had to be removed from the study, as he had a lateral cortex breach at three months, and was converted to a TKR. There was a significant loss of correction between 2 weeks and 6 weeks, and again a significant loss of correction between 6 weeks and 3 months. However, the average loss of correction was measured radiographically to be 1.6°±1.7°, between 2 week and 12 month postoperative follow-up. Though this may be statistically significant, it is not clinically significant when compared to PROMs. We divided the loss of correction into greater than 1.5° and less than 1.5° and compared them to measured PROMs at all time points. We found no significant correlation between increased loss of correction and poorer PROM scores. CONCLUSION: Computer assisted iBalance medial opening wedge HTO with accelerated rehabilitation program does radiographically show loss of correction over 12 months. However it is not clinically significant when compared to PROMs. ROM and inferred tibial slope is preserved.