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

Abstract

Purpose: 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). Methods: 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 MAD(supine)) radiograph, and standing WLRs (predicted MAD(stand)). Multiple linear regression analysis was used to identify variables predicting the postoperative MAD and unintended MAD(stand) correction, defined as the difference between predicted MAD(stand) and postoperative MAD. Results: Predicted MAD(supine) showed statistically greater reliability in predicting postoperative MAD than predicted MAD(stand) (intraclass correlation coefficient, 0.82 vs 0.45). Postoperative MAD was correlated with the predicted MAD(supine) and the difference in hip-knee-ankle angle between preoperative standing and supine WLRs (Delta HKA angle(stand-supine)) (R = 763, R-2 = 0.582, adjusted R-2 = 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 MAD(stand) correction was 6.52% +/- 8.66%. The difference in preoperative MAD between standing and supine WLRs was a significant predictor for unintended MAD(stand) correction (beta = -0.350, P = .004). Conclusions: Preoperative planning with supine WLRs can predict postoperative limb alignment in medial OWHTO more accurately than standing radiographs. The clinical significance of the Delta HKA angle(stand-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 Delta HKA angle(stand-supine). Preoperative soft-tissue laxity was significantly correlated with unintended correction of postoperative limb alignment resulting from preoperative planning with standing radiographs.