Ultrasonographic assessment of posterior cruciate ligament thickness following cruciate-retaining total knee arthroplasty: Relationship with functional scores.

Abstract

The long-term continuity and functionality of the posterior cruciate ligament following cruciate-retaining total knee arthroplasty remain inconclusive. This study compared posterior cruciate ligament thickness between prosthetic and contralateral non-operated knees using ultrasonography knees. In 179 patients with unilateral cruciate-retaining total knee arthroplasty, posterior cruciate ligament thickness in both prosthetic and contralateral non-operated knees was measured using ultrasonography. Ultrasonographic assessment was performed at the final follow up visit (mean follow up, 7.8 years; minimum, 4 years). The differences in thickness were calculated as the absolute thickness difference (ATD) and its relationship with factors such as insert thickness, implant manufacturer, tibial slope, tibial component to fibular head distance (TCFH), height, weight, body mass index (BMI), age, Knee Society Score (KSS) and follow up period was analysed. Posterior cruciate ligament thickness was significantly lower in prosthetic knees than in contralateral non-operated knees (4.2 ± 0.9 mm vs. 5.9 ± 1.3 mm; mean difference, 1.7 mm; Cohen's dz = 1.27; P < 0.001). Greater ATD was positively associated with tibial slope (r = 0.356, P < 0.01), weight (r = 0.267, P < 0.01), insert thickness (r = 0.226, P < 0.01), and BMI (r = 0.217, P < 0.001), whereas it was negatively associated with TCFH (r = -0.517, P < 0.01) and functional scores (r = -0.178, P < 0.01). In the long term after cruciate-retaining total knee arthroplasty, the posterior cruciate ligament appears thinner compared with the non-prosthetic knee. Correlation with lower functional score and ATD underscores the clinical significance of posterior cruciate ligament continuity and its impact on postoperative outcomes in cruciate-retaining total knee arthroplasty.