Collateral Ligament Tension and Balance Alone Does Not Ensure Improved Outcome After Total Knee Arthroplasty

It is hypothesized that suboptimal soft tissue and collateral ligament balance is a cause of patient dissatisfaction following total knee arthroplasty (TKA). This analysis examined the association between compartment pressures during TKA and patient-reported outcome measurements (PROMs).

This single-institution, retrospective cohort study of prospectively collected compartment pressure data measured during TKA comprised 145 patients who underwent surgery between 2015 and 2021 and completed 1-year follow-up PROMs. The primary outcome included pressures, in pounds (lbs), of the medial and lateral compartments in extension (5°), mid-flexion (45°), and flexion (90°), and associated PROMs. The difference been the 1-year and preoperative PROMs was used to separate the top 25% from the bottom 75% performers. Pressures were compared using Student's T-tests and multivariate linear regressions, while controlling for preoperative deformity. A subgroup analysis of the most popular implant was performed.

Higher medial compartment pressures were seen in our total cohort (Knee Society Score (KSS) mid-flexion 24 versus 18 lbs, P = .03, flexion 24 versus 17 lbs P = .01) and within our subgroup analysis (Short form- Mental (SF-M) extension 32 versus 21 lbs P = .01, KSS mid-flexion 27 versus 16 lbs P = .005, extension 31 versus 20 lbs P = .003). This trend persisted in the subgroup analysis when controlling for preoperative deformity (KSS extension +16.22 lbs P ≤ .001, mid-flexion +17.6 lbs. P = .001, and flexion +9.2 lbs, P = .005).

Several groups demonstrated higher medial versus lateral pressures. However, this pattern was not consistent across PROMs, suggesting that compartment pressures at the time of TKA are an important factor but not the sole predictor of patient satisfaction.