Importance of the gender and preoperative knee sagittal alignment to avoid unnecessary tibial resection in TKR.

BACKGROUND: Standard resections according to the TKR manufacturers can lead to unnecessary bone resections in some patients. The objective of this study was to determine in which patients is recommended to perform a minimal tibial resection (MTR) that could restore the joint line height (JLH). METHODS: Navigation records of 108 consecutive posterior cruciate-substituting TKR performed by one surgeon were analyzed. Optimal tibial resection depth to restore the JLH (0 mm) was calculated by an algorithm. Postoperatively, the knees were distributed in two groups: those in which a MTR (depth ≤ 8 mm) would have been enough to restore the JLH and those in which a standard resection depth would have been necessary. ROC curves and Youden index were used to determine the cutoff point of the coronal and sagittal mechanical axis that predicted a MTR restoring the JLH. Multivariate analysis was used to identify independent factors associated with requiring an MTR. RESULTS: A MTR could be required in 20 (18.5%) knees. In the ROC curve analyses, the cutoff points that best discriminated between minimal and standard tibial resection was ≤ 3° of varus and < 2° of flexion preoperative deformity. Multivariate analysis showed that female gender and preoperative flexion < 2° were significant predictors of requiring a MTR to restore JLH. CONCLUSION: A MTR with the JLH restoration could be possible in female patients with a preoperative sagittal deformity less than 2° of flexion. Preoperative coronal alignment had no influence to discriminate when a MTR is required.