Abstract
The goals of total knee arthroplasty are to restore the mechanical axis of the knee and create equal and symmetric tension on the ligaments throughout an arc of motion. What surgical technique best achieves this goal remains controversial.
In gap balancing, the extension space is created (distal femur and proximal tibia) and balanced. The flexion space and femoral component rotation are then set by placing tension on the collateral ligaments. This allows the femoral component to be rotated to create an equal and symmetric flexion gap based on the tension of collateral ligaments rather than arbitrary bony landmarks. In the measured resection technique, fixed bony landmarks are utilised to set femoral component rotation. Bony landmarks are subject to variations in patient's anatomy and inconsistency of the surgeon to reliably and reproducibly locate them during surgery. Fehring et al demonstrated that 49% of knees using bony landmarks had rotational errors of greater than 3 degrees. A recent study determined that the amount of femoral component rotation necessary to create a balanced flexion gap varied based on the amount of ligament release required, calling into question the validity of using this technique to set femoral component rotation. Additionally, a study by Dennis et al, showed that setting femoral component rotation based solely on bony landmarks leads to asymmetry in the flexion gap and excessive condylar lift off in flexion in over 60% of knees performed with a measured resection technique.
