Recognizing the Role of the Posterolateral Corner in Patients Undergoing Total Knee Arthroplasty for Fixed Varus Deformity.

Purpose: Varus deformity is the commonest presentation of the arthritic knee requiring surgical intervention. While correctable deformities lend themselves to realignment options like unicompartmental replacement, fixed deformities often need a total knee replacement. Current treatment options for patients with fixed coronal varus malalignment undergoing total knee arthroplasty include varying degrees of medial soft tissue releases, often leading to infringement of the medial collateral ligament complex and increased use of constrained options. We describe the role of the posterolateral (PL) tether in a select subgroup of patients needing release to achieve correction and minimising use of constrained options.

Patients and methods: A total of 384 patients with fixed varus deformity were retrospectively evaluated and categorised on the basis of weight bearing x-rays into four groups, namely, knees with angulation (F1), angulation with subluxation and torsion (F2), medial translation (F3) and deformity with major medial bone loss (F4). From this cohort, we identified patients with a tight PL tether that needed release to achieve good correction. These were predominantly in the F2 and F3 subgroups. Functional scores and outcomes were evaluated at a mean follow-up of 120.23 months.

Results: F1 cohort achieved good correction with medial soft tissue release, while F2 and F3 cohorts often needed a PL release. While functional outcomes and scores were comparable in both groups, survivorship was better in the group where release was done.

Conclusion: We recognise the role of the PL tether in a subgroup of patients with recalcitrant fixed varus deformities. Sequential release helped achieve good outcomes with minimal use of constrained options.

Level of evidence: Three.