An analysis of intra-operative variation in femorotibial alignment in the coronal plane during computer navigated total knee replacement.

A prospective study was performed to assess the intra-operative variation in femoral and tibial axis alignment during navigated total knee replacement. The intra-operative initial, trial and final mechanical axis alignments were recorded from the navigation system. The mean variation and correlation coefficient were calculated and analysed. There were 40 patients (24 females, 16 males), with ages ranging from 37 to 89 years. The average initial alignment was 0.03 degrees valgus, trial 0.64 degrees varus and final 0.25 degrees varus. Average deviation from initial to trial angle was 0.97 degrees, from trial to final angle 0.74 degrees and from initial to final angle 1.08 degrees. The correlation coefficient between the initial and trial alignment was 0.25, between trial and final alignment 0.43 and between initial and final alignment 0.09. This study highlights a significant variation in femorotibial alignment in the coronal plane between the different stages of navigated total knee replacement. Constant vigilance is necessary to monitor the parameters during surgery to achieve a desired final alignment.