Does the change between the native and the prosthetic posterior tibial slope influence the clinical outcomes after posterior stabilized TKA? A review of 793 knees at a minimum of 5 years follow-up.

INTRODUCTION

The understanding of the influence of posterior tibial slope (PTS) on knee kinematics has increased. However, the PTS influence on clinical outcomes remains unclear. The study aimed to evaluate whether a significant change between the native and the prosthetic tibial plateau PTS influences functional results and the risk of complications following total knee arthroplasty (TKA).

METHODS

This was a retrospective, monocentric comparative study. Clinical and radiological data from 793 knees were collected from a prospective surgical database. Inclusion criteria were patients operated with a posterior-stabilized TKA (PS-TKA) for primary tibiofemoral osteoarthritis, with or without associated patellofemoral osteoarthritis, or osteonecrosis of the femoral condyle or tibial plateau, with a minimum follow-up of 5 years. Range of motion and International Knee Society (IKS) score as well as radiological measurements were collected preoperatively and postoperatively at each follow-up visit. Two groups were composed according to the change in PTS between pre- and post-op (Group 1: ≤10°, n = 703; Group 2: >10°, n = 90).

RESULTS

The mean follow-up was 75.5 months ± 9.1. The mean change in PTS from preoperative was 4.96° ± 3.24 in group 1 and 12.7° ± 1.87 in group 2. There was no significant difference in the mean IKS Knee subscore (89.5 ± 10.7 and 89.7 ± 10.2, p = 0.89) and mean IKS Function subscore (88.2 ± 15.7 and 86.3 ± 16.6, p = 0.33) in groups 1 and 2, respectively. Postoperative maximum flexion was very satisfactory in both groups with no clinically relevant difference (120.0 ± 11.9 and 123.0 ± 8.3, p = 0.026). The complication rate was 5.0% (n = 40) (5.5% in group 1; 1.1% in group 2; p = 0.07) while the most common complication requiring further procedure was deep infection (n = 9, 1.1%) and the second most common was stiffness (n = 6, 0.8%).

DISCUSSION

PTS did not influence postoperative maximum flexion or clinical scores and was not associated with a higher complication rate at a minimum 5-year follow-up after PS-TKA.