Abstract
Introduction
While TKA procedures have demonstrated clinical success, medial/lateral overhang of the femoral component in total knee arthroplasty (TKA) of ≥3mm may be associated with an increased risk of knee pain, and distal femoral size may vary across ethnic populations. The aim of this study was to determine and compare the prevalence of femoral component overhang among an inclusive (non-segmented) and Asian-identified (Asian-segmented) population, using a flexible intramedullary-rod, posterior referencing method.
Methods
CT Scans from bilateral lower limbs of skeletally mature subjects (981 inclusive, 267 Asian-identified), without bone pathology were prospectively acquired. Bones were segmented and landmarks were modeled using a flexible intramedullary-rod, posterior referencing method. Femoral components were virtually positioned by aligning the lateral implant edge with the lateral bone edge, where the anterior flange meets the anterior chamfer. Medial and lateral component overhang was measured at three zones: (1) intersection of the anterior flange and anterior chamfer (medial only), (2) anterior chamfer mid-line, and (3) distal face mid-line. The central tendency of the samples was determined using the observed mean and median and the 95% confidence interval.
Results
In this study, the percentages of the inclusive population that had predicted fit with overhang <3mm were 98.9% at Zone 1 (medial), 99.7% and >99.9% at Zone 2, and 99.2% and 98.4% at Zone 3, for medial and lateral measurements, respectively. The percentages of the Asian-identified population with predicted overhang <3mm were 98.4% at Zone 1 (medial), 99.6% and >99.9% at Zone 2, and 99.1% and 98.3% at Zone 3, for medial and lateral measurements, respectively.
Discussion and conclusion
This virtual study demonstrates the femoral components of this knee system are predicted to fit over 98.3% of the inclusive and Asian-identified population with overhang less than 3mm, using a flexible intramedullary-rod, posterior referencing method. When evaluating the fit of an implant, it is important to match the implant placement per the design intent of the system.
