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Fig. 1 | Journal of Experimental Orthopaedics

Fig. 1

From: Flexion First Balancer: description of new technique in TKA to reproduce joint line and pre-disease mechanical alignment

Fig. 1

Mid-flexion instability after joint line elevation. Situation a represents a non-elevated joint line TKA, the center of rotation (red/blue dot) is restored by complete restoration of the posterior condylar offset and joint line height. The medial collateral ligament (marked yellow) will keep its isometry throughout the entire range of motion. Situation b represents an elevated joint line TKA with ticker insert to compensate. The axis of flexion (blue dot) no longer coincides with the MCL insertion (red dot). Therefore, the knee is stable in extension and 90° of flexion but laxity occurs in the mid-flexion range. The medial collateral ligament loses its isometric function in mid-flexion.

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