2017 Volume 36 Issue 1 Pages 33-40
Objective: Currently, there is no consensus on the value of patient-matched instrumentation (PMI) during total knee arthroplasty (TKA). However, most have been evaluations of the magnetic resonance imaging-based PMI. There is still controversy about computed tomography (CT)-based PMI. The purpose of this study was to analyze the accuracy of CT-based PMI with two-dimentional (2D) and three-dimentional (3D) evaluation.
Methods: Fifty seven consecutive patients with severe osteoarthritis underwent a primary TKA using either conventional instruments (CI) or CT-based PMI. We used 2D evaluation, which consisted of long-standing radiographs to measure the hip-knee-ankle angle (HKA), the frontal femoral component angle (FFC), and the frontal tibial component angle (FTC). The femoral and tibial component positions were analyzed more precisely with a 3D matching bone model made via pre- and postoperative CT images. For a 3D matching bone model made from these models, a 2D projection of the pre- and postoperative component positioning planes was made, and the projection angle was measured as angle error compared to the preoperative planned position. The blood loss and D-dimer level on postoperative day 7 were also recorded.
Results: Twenty knees in the CI group and 37 knees in the PMI group were available for analysis. There were few differences in postoperative average HKA angle, FFC and FTC. On the other hand, the percentage of HKA outliers was significantly higher in the CI group than the PMI group (CI: 35%; PMI: 10.8%, P=0.027) with 2D evaluation. In the component position, the PMI group showed a significantly decreased outliers rate of tibial component positioning for varus/valgus (CI: 29.4%; PMI: 5.6%, P=0.017) and posterior slope (CI: 41.2%; PMI: 11.1%, P=0.011) with 3D evaluation. The average D-dimer level on postoperative day 7 was significantly decreased in the PMI group.
Conclusion: CT-based PMI significantly reduced the number of outliers in the mechanical axis and component positioning compared to conventional instrumentation. CT-based PMI is expected to improve the mechanical axis and component alignment in total knee arthroplasty.
