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)
Summary
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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