Abstract
INTRODUCTION
Although the most commonly used method of femoral component alignment in total knee arthroplasty (TKA) is an intramedullary (IM) guides, this method demonstrated a limited degree of accuracy. The purpose of this study was to assess whether a portable, accelerometer-based surgical navigation system (Knee Align 2 system; Orth Align, Inc, Aliso Viejo, Calif) improve accuracy of the post-operative radiographic femoral component alignment compared to conventional IM alignment guide.
MATERIALS & METHODS
Since February 2014, 44 consecutive patients (39 female, 5 male) with primary arthritis of the knee were enrolled in this prospective, randomized controlled study. 24 patients underwent TKA (Vanguard RP or PS, Biomet Japan) using the navigation device for the distal femoral resection (Navigated Group), and 20 patients with conventional femoral IM alignment guide. The proximal tibial resection was performed using an extramedullary guide. All the operation was performed by a single senior surgeon (YK) with the same gap balancing technique except for the use of the navigation system for the femur. Accuracy of femoral implant positioning was evaluated on 2 weeks postoperative standing anteroposterior (AP) hip to ankle radiographs.
RESUTS
In the navigated group, 100% of patients had an alignment within 90 ± 3° to the femoral mechanical axis in the coronal plane, versus 90.0% in the IM guides cohort (Fig). The mean absolute difference between the intraoperative goal and the postoperative alignment was 0.79 ± 1.0° in the Knee Align 2 cohort, and 1.72 ± 1.6° in the IM guides cohort (P < 0.05). There was a difference in the standard deviations observed for the navigated cases and the conventional cases when femoral component position was considered. There were no technique specific complications associated with the navigation system.
DISCUSSION & CONCLUSION
The distal femoral resection has been the main source of error as for the neutral mechanical axis because of the difficulty in visualization and detection of the center of the femoral head. The results in the current study have shown that a portable, accelerometer-based navigation device (Knee Align 2 system) significantly decreases outliers in femoral component alignment compared to conventional IM alignment guides in TKA.
