Regression and correlation analysis of preoperative versus intraoperative assessment of axes during navigated total knee arthroplasty

Abstract

Objective: Modern computer assisted surgery (CAS) systems allow accurate positioning of the implants in navigated Total Knee Arthroplasty (TKA). However, when an operation is performed with a navigation system, it is important to know if the anatomical situation of the knee is reflected equally in both the preoperative image (e.g., CT) and the intraoperative navigation setup. In this study, we compared the preoperative anatomical situation to the virtual intraoperative situation of the navigation setup. Material and Methods: We analyzed 24 navigated operations. Intraoperatively, the condylar twist angle (CTA) was documented with the navigation system by measuring the angle between the transepicondylar axis (TEA) and posterior condyle axis (PCA). This data was compared with the preoperative data from the CT scan. Results: Statistical analysis revealed that there was no correlation between the pre- and intraoperative data (r = 0.095).Conclusions: Statistically, there is no possibility of collecting the same angles and axes when using the two different methods (CT and navigation) on the same knee. It is not possible to copy the preoperative anatomical situation exactly with the virtual intraoperative data. Reasons for this include systematic errors, as well as inter- and intraobserver errors in both methods. ©2006 Taylor & Francis.