Correction of axial and rotational alignment after medial and lateral releases during balanced gap TKA. A clinical study of 54 patients

Abstract

Background and purpose: Restoration of mechanical alignment after total knee arthroplasty can be achieved with ligament releases. Several previously described sequences and results achieved with cadaver knees, with measured resection implantation techniques, may not be applied to the balanced gap technique. We investigated the peroperative effect of stepwise soft tissue releases following the "tightest structure first" on leg axis in extension and femur rotation in flexion.

Methods: During PCL-retaining total knee arthroplasty (TKA), using a balanced gap technique in 54 patients we determined the effect of each ligament release using a navigation system while the knee was distracted with a tensor in extension and flexion. The effect on alignment in extension and on femoral rotation in flexion was measured for each release separately.

Results: In more than half of the patients, one or more ligament releases were necessary. Release of the posteromedial condyle led to a minor effect on leg axis in extension and femoral rotation in flexion, release of the superficial medial collateral ligament to a few degrees, mainly in extension. Release of the iliotibial tract led to a small correction of leg alignment in extension. There was no statistically significant difference in the alignment-correcting effect of a release dependent upon the sequence in which the structure was released.

Interpretation: In PCL-retaining TKA, a stepwise "tightest structure first" protocol for ligament releases in extension with the balanced gap technique results in effective, gradual, alignment correction in extension, and limited femoral rotating effects in flexion.

Figure 1.

A. After a medial release (already released in the drawing to the left), when a tensor is inserted in the knee the femur would theoretically exorotate as a result of the loosened medial ligament structure. B. After a lateral release (already released in the drawing to the left), when a tensor is inserted in the knee the femur would theoretically endorotate as a result of the loosened lateral ligament structure.

Figure 2.

Double-bladed calibrated tensor (balanSys; Mathys AG, Bettlach, Switzerland). A quantified amount of vertically-oriented force can be applied independently to the medial and lateral compartments.

Figure 3.

Box plot of change in leg axis after PMC release (n = 15) and subsequent SMCL release (n = 9) (green boxes, on the left), and after SMCL release (n = 4) and subsequent PMC release (n = 1) (pink boxes, on the right). The median is shown as a horizontal line across each box. The vertical lines represent the minimum and maximum values.

Figure 4.

Box plot of change in femoral rotation after PMC release (n = 15) and subsequent SMCL release (n = 9) (green boxes, on the left), and after SMCL release (n = 4) and subsequent PMC release (n = 1) (pink boxes, on the right). The median is shown as a horizontal line across each box. The vertical lines represent the minimum and maximum values.

Figure 5.

Box plot of change in leg axis after IT release (n = 7) and subsequent PLC (n = 2) or POP release (n = 1) The median is shown as a horizontal line across each box. The vertical lines represent the minimum and maximum values.

Figure 6.

Box plot of change in femoral rotation after IT release (n = 7) and subsequent PLC (n = 2) or POP release (n = 1). The median is shown as a horizontal line across each box. The vertical lines represent the minimum and maximum values.