ABSTRACT
PURPOSE: To examine the correlation between the Navigation and radiographic measurements for the postoperative mechanical axis and component position in total knee arthroplasty. MATERIALS AND METHODS: From December 2005 to May 2006, Navigation assisted MIS TKA was performed on 46 knees of 34 patients. After fixing the components, the mechanical axis (MA) of the lower extremity, femoral component position to the mechanical axis in the coronal plane (theta), tibial component position in the coronal (beta) and sagittal (sigma) planes was measured using the Navigation. Two observers measured the same angles using the postoperative follow-up radiographs. The measurements were compared and the correlation between the Navigation and radiographic measurement was analyzed. RESULTS: The average Navigation measurements were valgus 0.02+/-1.09 degrees for MA, varus 0.05+/-0.96 degrees for theta, valgus 0.02+/-0.86 degrees for beta and 4.03+/-1.25 degrees for sigma. The mean radiographic measurements of observer 1 were valgus 0.71+/-3.73 degrees for MA, valgus 1.14+/-1.72 degrees for theta, valgus 0.90+/-1.47 degrees for beta and 4.51+/-2.03 degrees for sigma. Those of observer 2 were valgus 0.12+/-3.39 degrees, valgus 0.16+/-1.96 degrees, valgus 0.30+/-1.65 degrees and 3.85+/-1.60 degrees, respectively. CONCLUSION: The average of measurement for the component position showed a statistically significant difference in the MA (p=0.001), theta (p=0.000) and beta (p=0.000) among three groups. There were a relatively high correlation between observer 1 and 2 for the radiographic measurements (r=0.67-0.96). However there was a very low correlation between the Navigation and radiographic measurements (r=0.10-0.39). Therefore, the possibility of a difference between the Navigation and radiographic measurement need to be considered when evaluating the component position.