Abstract
Introduction
Well-balanced soft tissue is essential for achieving a good result when performing total knee arthroplasty. The preoperative planning is critical for ensuring a good operation. 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
Of the 120 cases for which medial release was performed, 30 (25.0%), 41 (34.2%), 20 (16.7%), and 29 (24.2%) cases were in group 1, 2, 3, and 4, respectively. After medial release, the difference between the medial and lateral gaps in flexion and extension was 0.1 mm (range, 0 to 1 mm) and 0.1 mm (range, 0 to 1 mm), respectively. The difference between the flexion and extension gaps was 0.6 mm (range, 0 to 1.5 mm). The mean femorotibial angle on the preoperative distractive stress radiograph was valgus 2.4° (group 1), valgus 0.8° (group 2), varus 2.1° (group 3) and varus 2.7° (group 4). The extent of medial release increased with increasing degree of varus deformity seen on the preoperative distractive stress radiograph.(Figure 1)
Conclusions
The preoperative distractive stress radiograph was useful for predicting the extent of medial release when performing primary total knee arthroplaty.
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