Abstract
BackgroundIn megaprosthetic knee replacement, surgeons use cutting guides that depend on anatomLevel of evidenceical references to determine the ideal cutting plane alignment. In this work, we investigated the accuracy of using femoral cortical surfaces and tibial canal portions as the references. The study aims to improve the design and use of the cutting guides.Materials and methodsSixty-one knee scanograms of 33 patients (mean age around 20 years) diagnosed with osteogenic sarcoma and undergoing distal femur megaprosthetic surgery were acquired. Angles between the selected anatomical references and axis perpendicular to the ideal cutting plane (anatomical axis for femur and mechanical axis for tibia) were measured for both femur and tibia, in coronal view. The smaller the magnitude of the angles, the better the anatomical reference is.ResultsAt the central femoral region, on average, both lateral and medial cortical surfaces give accurate alignment of the ideal cutting plane (0.6° and 0.8°, respectively), with no significant difference (p > 0.01). At the distal region, the lateral cortical surface gives significantly better alignment compared to the medial cortical surface (p < 0.01), but not as accurate (1.4°) as in the central region. For tibia, the central tibial canal gives significantly accurate alignment of the ideal cutting plane (−0.3°) on average, compared to the proximal tibial canal (p < 0.01).ConclusionsFor a femoral cut, both lateral and medial cortical surfaces are the best anatomical references, but only at the central region. For a tibial cut, the central anatomical axis is the best reference.Level of evidenceIV.
Highlights
In megaprosthetic knee replacement, a femoral component placed over the cut surface of the femoral shaft articulates with a tibial component placed over the cut surface of the tibial plateau [12]
The ideal femoral cutting plane is perpendicular to its anatomical axis and the ideal tibial cutting plane is perpendicular to its mechanical axis (MA) [3, 4, 7]
A positive value of the angle between medial or lateral femoral cortical lines (FCLs) and femoral anatomical axis (FAA) suggests that the FCL is moving toward medial or lateral side, respectively, as it starts from the proximal to distal region of the femur
Summary
A femoral component placed over the cut surface of the femoral shaft articulates with a tibial component placed over the cut surface of the tibial plateau [12]. The alignment of the femoral and tibial components in the coronal plane is one of the most important factors for the success of the surgery [3, 6]. Designed cutting guides use anatomical references to determine the ideal cutting plane alignment [11, 15]. A cutting guide as shown in Fig. 1a uses the outer cortical surface (medial or lateral) as a reference to determine the alignment of femoral anatomical axis (FAA), and the ideal cutting plane. Surgeons use cutting guides that depend on anatomLevel of evidence ical references to determine the ideal cutting plane alignment. The smaller the magnitude of the angles, the better the anatomical reference is
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