Preoperative Supine Radiographs Are More Accurate Than Standing Radiographs for Preoperative Planning in Medial Open-Wedge High Tibial Osteotomy

Abstract

To verify the accuracy of supine nonweight-bearing radiography versus standing radiography in preoperative planning and to determine the predictors of unintended limb alignment correction in medial open-wedge high tibial osteotomy (OWHTO). Consecutive patients who underwent medial OWHTO for medial osteoarthritis of the knee with varus alignment were retrospectively reviewed. The analyzed pre- and postoperative radiologic measurements included postoperative mechanical axis deviation (MAD) on standing whole-leg radiographs (WLRs), the predicted value of the postoperative MAD on the preoperative supine (predicted MADsupine) radiograph, and standing WLRs (predicted MADstand). Multiple linear regression analysis was used to identify variables predicting the postoperative MAD and unintended MADstand correction, defined as the difference between predicted MADstand and postoperative MAD. Predicted MADsupine showed statistically greater reliability in predicting postoperative MAD than predicted MADstand (intraclass correlation coefficient, 0.82 vs 0.45). Postoperative MAD was correlated with the predicted MADsupine and the difference in hip-knee-ankle angle between preoperative standing and supine WLRs (ΔHKA anglestand-supine) (R=763, R2= 0.582, adjusted R2= 0.569, P < .001) and did not differ significantly from the predicted MADsupine, with a mean difference of 0.28% ± 5.11% (P= .656). The mean unintended MADstand correction was 6.52% ± 8.66%. The difference in preoperative MAD between standing and supine WLRs was a significant predictor for unintended MADstand correction (β= -0.350, P= .004). Preoperative planning with supine WLRs can predict postoperative limbalignment in medial OWHTO more accurately than standing radiographs. The clinical significance of the ΔHKA anglestand-supine for the risk of overestimation of postoperative limb alignment might be low because of the low power in the prediction model and small value of the ΔHKA anglestand-supine. Preoperative soft-tissue laxity was significantly correlated with unintended correction of postoperative limb alignment resulting from preoperative planning with standing radiographs. Level IV, retrospective comparative study.