Purpose: The accelerometer-based system is a portable surgical navigation system for TKA that does not require the use of a large computer console for registration and alignment feedback as required in computer-assisted surgery (CAS). The purpose of this prospective study was to determine the accuracy of the accelerometer-based system in the tibial component positioning and also to evaluate clinical outcomes.
Methods: Between December 2011 and July 2012, a total of 53 consecutive patients with primary gonarthrosis were prospectively enrolled for unilateral TKA using a handheld surgical navigation system to perform the tibial resection. Pre-operatively and postoperatively, patients were asked to fill out a visual analogue scale for pain (VAS) and a knee injury and osteoarthritis outcome score (KOOS). Standing antero-posterior (AP) hip-knee-ankle (HKA) and lateral knee-to-ankle radiographs were performed to determine the varus/valgus alignment and the posterior slope of the tibial components relative to the mechanical axis.
Results: The mean duration of follow-up was 23 months. Average preoperative VAS was 8.3 ± 0.67, which significantly improved to a mean 1.2 ± 0.57 at final follow up (P < 0.001). All scores significantly increased compared with pre-operative scores, except for the KOOS sport component (P = 0.075) and quality of life (P = 0.19). Intra-operatively, the average reading provided by the system with regard to varus/valgus alignment before performing the tibial resection was 0.55° ± 0.43. The average postoperative radiographic alignment of the tibial component in the coronal plane was 0.65° ± 0.59 of deviation by the ideal alignment (P > 0.05).
Conclusion: This study demonstrates that the OrthAlign navigation system combines the accuracy of the computer-assisted surgery systems with the ease of use and familiarity of the traditional instruments while avoiding the drawbacks of the CAS technique and disadvantages of conventional IM femoral alignment systems. The system could demonstrate an improvement in the incidence of outliers in final coronal alignment, as compared with a patient-specific cutting guide.