Surgical Outcomes of the Accelerometer-based Navigation System for Total Knee Arthroplasty

Overall the success rate of TKR is very high with high patient satisfaction and outcomes. Survivorship depends on patient selection and surgical techniques. Femoral and tibial component mal-alignment might lead to early failure.

Although recent studies have questioned the significance of overall postoperative mechanical alignment on survivorship, most studies still demonstrate alignment to be a crucial factor in the clinical success of TKA [1]. Ritter et al [2], in a review of 6070 TKAs, noted the risk of aseptic failure to significantly increase with a tibial component orientation less than 90° relatives to the tibial axis and a femoral component orientation greater than 8° of valgus relative to the femoral axis (failure rate, 8.7%).

Berend et al [3], in a review of 3152 TKAs, demonstrated that a tibial varus alignment of greater than 3° increased the odds of implant failure and medial bone collapse by roughly 17 times.

The most commonly used methods of component alignment in TKA are an extramedullary (EM) alignment guide for the tibial resection and an intramedullary (IM) alignment guide for the distal femoral resection. Unfortunately, these "conventional" methods have demonstrated a limited degree of accuracy for both overall mechanical alignment and individual component Method to create an even more accurate resection includes the use computer-assisted navigation technique. In a meta-analysis of 29 studies comparing computer assisted surgical (CAS) to conventional techniques in TKA (Mason et al). The authors found that only 68.2% of TKAs in the conventional group achieved an overall mechanical axis within 3° of neutral (vs 91.0% in the CAS group), 65.9% achieved a femoral varus/valgus alignment within 2° of perpendicular to the femoral mechanical axis (vs 90.4% in the CAS group) and 79.7% achieved a tibial varus/valgus alignment within 2° of perpendicular to the tibial mechanical axis (vs 95.2% in the CAS group).

However, despite these advantages, concerns regarding increased capital costs, operative times, extra pin sites, and the learning curve associated with the use of CAS techniques have continued to limit its widespread acceptance.