Objective: To compare the deviation of three femoral rotational axes in computer assisted surgery [CAS] total knee arthroplasty
[TKA] using the gap technique.

Materials and Methods: A retrospective cross-sectional study was conducted between 2004 and 20l3 at the Department of Orthopaedics, Ramathibodi Hospital of patients who had undergone
computer-assisted total knee arthroplasty. All patients were included with the exception of those who had had post-traumatic knee osteoarthritis, valgus knee, or trapezoidal medial-lateral gap.
Baseline characteristics and femoral rotational axes (Whiteside, posterior condyle, and transepicondyle) were recorded. Comparison among the three axes was performed using analysis of variance.

Results: The study included l40 patients (ll4 women and 26 men) with an average age of 7l.6+8.4 years, representing l40 total knee arthroplasties. The deviation of femoral component rotation axes
were: Whiteside's line 0.42+4.49 degrees, posterior condylar line -l.43+4.82 degrees and transepicondylar line -3.93+5.00 (p<0.00l).

Conclusion: Whiteside's line showed the smallest deviation in femoral component rotation compared to the gap technique in CAS TKA.

Keywords: Femoral component rotation, Computer-assisted, Total knee arthroplasty, Gap technique, Anatomical landmark