Abstract
BackgroundMany surgeons have determined the surgical transepicondylar axis (sTEA) after distal femur resection in total knee arthroplasty (TKA). However, in most navigation systems, the registration of the sTEA precedes the distal femur resection. This sequential difference can influence the accuracy of intraoperative determination for sTEA when considering the proximal location of the anatomical references for sTEA and the arthritic environment. We compared the accuracy and precision in determinations of the sTEA between before and after distal femur resection during navigation-assisted TKA.MethodsNinety TKAs with Attune posterior-stabilized prostheses were performed under imageless navigation. The sTEA was registered before distal femur resection, then reassessed and adjusted after distal resection. The femoral component was implanted finally according to the sTEA determined after distal femur resection. Computed tomography (CT) was performed postoperatively to analyze the true sTEA (the line connecting the tip of the lateral femoral epicondyle to the lowest point of the medial femoral epicondylar sulcus on axial CT images) and femoral component rotation (FCR) axis. The FCR angle after distal femur resection (FCRA-aR) was defined as the angle between the FCR axis and true sTEA on CT images. The FCR angle before distal resection (FCRA-bR) could be presumed to be the value of FCRA-aR minus the difference between the intraoperatively determined sTEAs before and after distal resection as indicated by the navigation system. It was considered that the FCRA-bR or FCRA-aR represented the differences between the sTEA determined before or after distal femur resection and the true sTEA, respectively.ResultsThe FCRA-bR was −1.3 ± 2.4° and FCRA-aR was 0.3 ± 1.7° (p < 0.001). The range of FCRA-bR was from −6.6° to 4.1° and that of FCRA-aR was from −2.7° to 3.3°. The proportion of appropriate FCRA (≤ ±3°) was significantly higher after distal femur resection than that before resection (91.1% versus 70%; p < 0.001).ConclusionsThe FCR was more appropriate when the sTEA was determined after distal femur resection than before resection in navigation-assisted TKA. The reassessment and adjusted registration of sTEA after distal femur resection could improve the rotational alignment of the femoral component in navigation-assisted TKA.Level of evidenceIV.
Highlights
Appropriate rotation of the femoral component is critical for a successful outcome after total knee arthroplasty (TKA) [1, 2]
The accuracy of navigation-assisted TKA depends upon the appropriate registration of bony landmarks, and it is known that registration errors for surgical transepicondylar axis (sTEA) can occur frequently, especially in procedures guided by imageless navigation because of difficulty with identification [4]
The range of FCR angle before distal resection (FCRA-bR) was from −6.6° to 4.1°, and that of FCRA-aR was from −2.7° to 3.3° (Fig. 4)
Summary
Appropriate rotation of the femoral component is critical for a successful outcome after total knee arthroplasty (TKA) [1, 2]. Navigation is recognized as a useful tool by which to reproducibly position components with the desirable coronal and sagittal alignment in the TKA procedure [4, 5]. It remains under debate whether the rotational alignment can be further improved [6, 7]. Many surgeons have determined the surgical transepicondylar axis (sTEA) after distal femur resection in total knee arthroplasty (TKA). In most navigation systems, the registration of the sTEA precedes the distal femur resection This sequential difference can influence the accuracy of intraoperative determination for sTEA when considering the proximal location of the anatomical references for sTEA and the arthritic environment.
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