Measurement of rotational and coronal alignment in total knee arthroplasty using a navigation system is reproducible

Intraoperative kinematic analysis using a navigation system in total knee arthroplasty (TKA) has been increasing. The purpose of the present study was to assess the reproducibility of the intraoperative kinematics analysis in TKA using the image-free knee navigation system. Fifty-one knees in 45 patients who received TKA, performed by a single surgeon (the senior consultant) with the resident, were included in this retrospective study. There were 7 men and 38 women and the mean age was 74.3 years. Cruciate retaining (CR) type and posterior stabilized (PS) type implants were inserted into 38 and 13 knees. The senior consultant and the resident analyzed initial kinematics, the axial rotation of the tibia and the coronal alignment of the lower limb, three times in each knee on manual passive knee flexion intraoperatively using the navigation system. Intra-class correlation coefficients (ICC) with 95 % confidence intervals were calculated to determine the reproducibility of this analysis. In regard to intra-rater reproducibility with axial rotation of the tibia, the ICC of the senior consultant was 0.965 for CR knees and 0.972 for PS knees while the ICC of the resident were 0.966 and 0.956. Inter-rater reproducibility was excellent for both knee types (ICC, 0.885 for CR knees and 0.864 for PS knees). In regard to intra-rater reproducibility with coronal alignment of the lower limb, ICC of the senior consultant was 0.990 for CR knees and 0.996 for PS knees while those of the resident were 0.990 and 0.995. Inter-rater reproducibility was also excellent for both knee types (ICC, 0.978 for CR knees and 0.994 for PS knees). Manual intraoperative kinematic analysis using a navigation system in TKA showed excellent reproducibility. This result may encourage further studies about intraoperative kinematic analysis using a navigation system in TKA.