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Medial, lateral soft tissue releases impact amount of femoral rotation needed to balance flexion gap in TKA
Researchers found releasing medial soft tissue structures decreased the amount of external rotation necessary to balance the flexion gap, while releasing lateral soft tissue structures increased the amount of external rotation, according to results of this study.
“The amount of femoral component rotation necessary to create a rectangular flexion gap was significantly less for knees with more extensive releases of medial structures, whereas the opposite was true for knees requiring lateral-sided releases,” Christian P. Christensen, MD, and colleagues wrote in the study. “The native femur rotates following ligament releases, so the relationship between the femoral component and the distal femur must vary accordingly in order to maintain the rectangular shape of the flexion gap. Gap-balancing techniques may allow the surgeon to account for patient-specific bony morphology and soft tissue tension to properly balance the flexion gap.”
In the study of 1,500 consecutive total knee arthroplasty cases, Christensen and colleagues found the external rotation decreased by 4.7° for one medial structure, 4.1° for two medial structures, 2.8° for three structures and 1.1° for four or more structures, according to the abstract. However, greater external rotation was necessary for lateral soft tissue releases: one structure increased the external rotation by 5.3°, two structures increased external rotation by 5.5° and three structures or more increased the external rotation by 8.6°.
Disclosure: Christensen is on the speaker’s bureau for Biomet and receives research support from ConforMIS and Biomet. One of the authors (Jacobs) is a paid consultant for ERMI and receives research support from Voyant Health.