Accuracy of soft tissue balancing in TKA: comparison between navigation-assisted gap balancing and conventional measured resection

Equalized rectangular extension and flexion gaps are considered desirable to ensure proper kinematics in total knee arthroplasty (TKA). We compared soft tissue balancing in TKAs performed using navigation-assisted gap-balancing (60 knees) and conventional measured resection (56 knees). The outlier of soft tissue balancing was defined as a gap difference >3 mm between the medial and lateral sides in 90° flexion and extension. Medial or lateral outliers in extension or flexion were observed in 12% (7 of 60) navigation TKAs and 25% (14 of 56) conventional TKAs (p = 0.028). There were more outliers in flexion–extension gap difference on the medial side in the conventional (23%) than in the navigation-assisted (5%) group (p = 0.025). However, the proportion of flexion gap difference, extension gap difference, and lateral gap difference outliers did not differ significantly between the two groups (n.s.). Additionally, clinicoradiologic outcomes were similar for the two groups except for the postoperative mechanical axis outlier (p = 0.012). Navigation-assisted soft tissue balancing in TKA reduced not only the postoperative alignment outlier, but also the medial gap difference and achieved a more rectangular flexion and extension gap compared with conventional TKA.