Abstract
Introduction
Patient-specific instrumentation (PSI) is a contemporary method to optimize accuracy of alignment in total knee arthroplasty (TKA). As the potential benefits come at the cost of increased economic and logistic expenses, there is great scientific and practical interest in the actual advantages and reliability of such systems. Therefore, the purpose of the present study was to compare clinical results, radiological limb alignment, and three-dimensional (3D)-component positioning between conventional instrumentation (CVI) and a computed tomographic (CT)-based PSI in primary TKA.
Methods
Two-hundred-ninety consecutive patients (300 knees) with severe, debilitating osteoarthritis scheduled for TKA were included in this study using either CVI (n=150) or PSI (n=150). Patients were clinically assessed according to the Knee Society Score (KSS), range of motion (ROM), and visual analog scale for pain (VAS) before and two years after surgery. Hip-knee-ankle angle (HKA) and 3D-component positioning were assessed on postoperative radiographs and CT to evaluate accuracy of CVI and PSI.
Results
Data of 222 knees (CVI: n=108, PSI: n=114) were available for analysis after a mean follow up of 28.6±5.2 months. Clinical (KSS knee and function, ROM, VAS) and radiological parameters (HKA) improved significantly from pre to postoperative in both groups. At the early follow up, clinical outcome was comparable between the two groups, whereas KSS function and VAS for pain were significantly better in the PSI group. Mean HKA deviation from the targeted neutral mechanical axis (CVI: 2.2°±1.7°; PSI: 1.5°±1.4°; p<0.001), rates of outliers (CVI: 22.2%; PSI: 9.6%; p=0.016), and 3D-component positioning outliers were significantly lower in the PSI group. Additionally, the accuracy of femoral and tibial component positioning was significantly higher in all planes. At early follow up, all clinical scores were significantly better in the subgroup of HKA non-outliers (HKA: 180°±3°) compared to HKA outliers.
Conclusions
CT-based PSI compared to CVI improves accuracy of mechanical alignment restoration and 3D-component positioning in primary TKA. While clinical outcome was comparable between the two instrumentation groups at early follow up, significantly inferior outcome was detected in the subgroup of HKA-outliers.
