Background: This study evaluated the preoperative distractive stress radiographs in order to quantify and predict the extent of medial release according to the degree of varus deformity in primary total knee arthroplasty.
Methods: We evaluated 120 varus, osteoarthritic knee joints (75 patients). The association of the angle on the distractive stress radiograph with extent of medial release was analyzed. The extent of medial release was classified into the following 4 groups according to the stage: release of the deep medial collateral ligament (group 1), release of the posterior oblique ligament and/or semimembranous tendon (group 2), release of the posterior capsule (group 3) and release of the superficial medial collateral ligament (group 4).
Results: The mean femorotibial angle on the preoperative distractive stress radiograph was valgus 2.4 degrees (group 1), valgus 0.8 degrees (group 2), varus 2.1 degrees (group 3) and varus 2.7 degrees (group 4). The extent of medial release increased with increasing degree of varus deformity seen on the preoperative distractive stress radiograph.
Conclusions: The preoperative distractive stress radiograph was useful for predicting the extent of medial release when performing primary total knee arthroplasty.
Keywords: Distractive stress radiograph; Femoro-tibial angle; Medial release; Total knee arthroplasty.