Abstract

BackgroundThe purpose of this study was to compare restoration of mechanical limb alignment and three-dimensional component-positioning between conventional and patient-specific instrumentation in total knee arthroplasty.MethodsRadiographic data of patients undergoing mobile-bearing total knee arthroplasty (n = 1257), using either conventional (n = 442) or patient-specific instrumentation (n = 812), were analyzed. To evaluate accuracy of axis restoration and 3D-component-positioning between conventional and patient-specific instrumentation, absolute deviations from the targeted neutral mechanical limb alignment and planned implant positions were determined. Measurements were performed on standardized coronal long-leg and sagittal knee radiographs. CT-scans were evaluated for accuracy of axial femoral implant rotation. Outliers were defined as deviations from the targeted neutral mechanical axis of > ± 3° or from the intraoperative component-positioning goals of > ± 2°. Deviations greater than ± 5° from set targets were considered to be severe outliers.ResultsDeviations from a neutral mechanical axis (conventional instrumentation: 2.3°± 1.7° vs. patient-specific instrumentation: 1.7°± 1.2°; p < 0.001) and numbers of outliers (conventional instrumentation: 25.8% vs. patient-specific instrumentation: 10.1%; p < 0.001) were significantly lower in the patient-specific instrumentation group. Significantly lower mean deviations and less outliers were detected regarding 3D-component-positioning in the patient-specific instrumentation compared to the conventional instrumentation group (all p < 0.05).ConclusionsPatient-specific instrumentation prevented from severe limb malalignment and component-positioning outliers (> ± 5° deviation). Use of patient-specific instrumentation proved to be superior to conventional instrumentation in achieving more accurate limb alignment and 3D-component positioning, particularly regarding femoral component rotation. Furthermore, the use of patient-specific instrumentation successfully prevented severe (> 5° deviation) outliers.

Highlights

  • The purpose of this study was to compare restoration of mechanical limb alignment and threedimensional component-positioning between conventional and patient-specific instrumentation in total knee arthroplasty

  • Outliers were defined as deviations from the targeted neutral mechanical axis of more than ± 3° (HKA) or from the intra-operative component positioning goals of more than ± 2° (FFC, Frontal tibial component (FTC), Lateral femoral component (LFC), Lateral femoral (LFC) and tibial (LTC), and femoral component rotation (FCR))

  • There were significantly more severe outliers detected in the conventional instrumentation (CVI) compared to the patient-specific instrumentation (PSI) group regarding hip-knee-ankle angle (HKA) (0% vs. 6.3%, p < 0.001), FTC (0% vs. 1.4%, p = 0.002), LFC (0% vs. 2.7%, p < 0.001), and LTC (0% vs. 1.1%, p = 0.005)

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Summary

Introduction

The purpose of this study was to compare restoration of mechanical limb alignment and threedimensional component-positioning between conventional and patient-specific instrumentation in total knee arthroplasty. Restoration of neutral mechanical limb alignment and exact component positioning have been reported to be essential for satisfactory long-term outcome after total knee arthroplasty (TKA) [1, 2]. The clinical importance of a neutral mechanical alignment on implant longevity has recently become a matter of discussion, there is currently no better parameter to aim for when performing TKA [1, 5, 6]. Computer-assisted surgery could improve surgical accuracy, it came with the disadvantages of complex instrumentation and longer surgery times

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