Effect of soft tissue tension on measurements of coronal laxity in mobile-bearing total knee arthroplasty

Background. The purpose of this study was to determine the effect of intraoperative coronal laxity in total knee arthroplasty on the postoperative condition. Methods. We conducted stress arthrometric studies using a Telos arthrometer on 40 knees in 36 patients. Both posterior cruciate ligament-retaining (PCLR) prostheses and posterior cruciate-sacrificing (PCLS) prostheses were placed in 20 knees respectively. All of the TKA procedures were judged clinically successful (Hospital for Special Surgery scores: PCLR 92 3 points, PCLS 91 4 points). Laxities were measured under spinal anesthesia (immediately postoperatively) and 6 months postoperatively. Results. PCLR prostheses had an average of 2.9 degrees +/- 1.8 degrees and 3.0 degrees +/- 1.2 degrees in abduction and 4.4 degrees +/- 2.8 degrees and 3.6 degrees +/- 1.5 degrees in adduction under anesthesia and the postoperative condition. PCLS prostheses had average laxities of 3.8 degrees +/- 1.4 degrees and 3.5 degrees +/- 0.9 degrees in abduction and 4.6 degrees +/- 3.8 degrees and 4.0 degrees +/- 1.7 degrees in adduction. There were no significant differences between them. Conclusions. The findings suggest that surgeons should emphasize the achievement of suitable laxity under anesthesia to ensure the success of total knee arthroplasty.