Abstract
Objective To evaluate 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° of external rotation of the femoral component is appropriate in these patients undergoing total knee arthroplasty (TKA).
Methods We measured the angle of external rotation in 167 magnetic resonance imaging (MRI) scans using 4 different methods for the PCA according to the posterior landmarks: measurement A – chondral prominences; measurement B – bony prominences; measurement C – lateral bony prominence and medial chondral prominence; and measurement D – lateral chondral prominence and medial bony prominence. We statistically compared these measurements with the traditional 3° of external rotation used in TKA.
Results The mean angles of external rotation in measurements A, B, C, and D were of 5.44° ± 2.39°, 4.94° ± 2.10°, 8.56° ± 2°, and 2.33° ± 2° respectively. All measurement methods resulted in significant differences regarding the universal value of 3° (p > 0.0001). All intergroup comparisons showed statistical differences among the measurement methods (p > 0.0001), except for the comparison between measurements A and B (p = 0.1614).
Conclusion Using a chondral or bony reference point for the PCA, the TEA in the Brazilian population studied presented approximately 5° of external rotation. The traditional rotation of the femoral component of 3° regarding the PCA may be insufficient in the Brazilian population, especially in valgus knees. Therefore, we emphasize the significance of an individualized approach to achieve the ideal rotational alignment of TKA components.
Keywords
arthroplasty, replacement, knee - knee joint - magnetic resonance imaging - rotation
Bibliographical Record
Enzo Mameri, Isabelle Kaptzky Ballarini, Maria Beatriz Pinheiro Leonel, Marcio de Castro Ferreira, Marcus Vinicius Malheiros Luzo, Marcelo Seiji Kubota. Morfologia do fêmur distal em uma população brasileira: Desafiando o uso universal de 3° de rotação externa. Rev Bras Ortop (Sao Paulo) 2025; 60: s00441800923.
DOI: 10.1055/s-0044-1800923
