Gap-balancing technique combined with patient-specific instrumentation in TKA

Combining patient-specific instrumentation (PSI) with a balancer device in total knee arthroplasty (TKA) to achieve functional femoral rotational alignment is a novel technique. The primary goal of this study was to introduce a new method to combine PSI with a gap-balancing technique and to determine the impact of the technique on rotation of the femoral component. Twenty-five primary TKAs (15 women, 10 men) were prospectively studied. All TKAs involved PSI with an associated gap-balancing device. Front plane alignment was performed intraoperatively with the PSI, followed by rectangular, symmetrical extension and creation of a flexion gap using the balancer device to set the femoral rotation. Femoral component rotation was between 3A degrees internal and 6A degrees external rotation versus the transepicondylar axis. There were no postoperative signs of patellofemoral dysfunction. In no cases was the resulting joint line displacement > 3 mm. The mean elevation was 1.2 +/- A 0.9 mm (range 0-3). The leg axis was straight in all cases (+/- 3A degrees), at a mean of 1.6A degrees A A +/- A 1.0A degrees varus (range 0A degrees-3A degrees varus). PSI was with the gap-balancing technique was successfully used without affecting anatomical alignment. With the balancer device, PSI can be used more widely than techniques based solely on landmarks, as the soft-tissue tension can be taken into account, thus virtually eliminating flexion instabilities.