Abstract
Objectives:
To assess the external rotation angle between the transepicondylar axis (TEA) and the posterior condylar axis (PCA) in a Brazilian population, to determine whether the universal use of 3-degrees external rotation of the femoral component is appropriate during total knee arthroplasty (TKA) in this population.
Methods:
The TEA rotation relative to the PCA was measured in 167 magnetic resonance imaging (MRI) exams using four different methods for the PCA, based on posterior reference points: (A) cartilage references; (B) bony references; (C) lateral posterior reference and medial cartilage reference; and (D) lateral cartilage reference and medial bony reference. The measurements were statistically compared to the traditional 3-degrees external rotation used in TKA instrumentation. An analysis of variance was conducted to assess differences between the measurement methods.
Results:
Mean TEA external rotation for methods A, B, C, and D was 5.44º ± 2.39º, 4.94º ± 2.10º, 8.56º ± 2º, and 2.33º ± 2º, respectively. All measurement methods showed significant differences compared to the traditional 3-degrees external rotation (p<.0001). Significant differences were also found between all measurement methods (p<.0001), except between methods A and B (p=0.1614).
Conclusion:
Using cartilage or bony reference points for the PCA, the TEA in the Brazilian population is approximately 5-degrees externally rotated. The traditional 3-degrees femoral component rotation may be insufficient for this population, particularly in valgus knees. This highlights the importance of an individualized approach to achieve optimal component rotational alignment during TKA.