Open Access
CC BY 4.0 · Rev Bras Ortop (Sao Paulo) 2025; 60(01): s00441800923
DOI: 10.1055/s-0044-1800923
Artigo Original

Distal Femur Morphology in a Brazilian Population: Challenging the Universal Use of 3° of External Rotation

Article in several languages: português | English
1   Departamento de Ortopedia e Traumatologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil
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1   Departamento de Ortopedia e Traumatologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil
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1   Departamento de Ortopedia e Traumatologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil
,
1   Departamento de Ortopedia e Traumatologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil
,
1   Departamento de Ortopedia e Traumatologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil
,
1   Departamento de Ortopedia e Traumatologia, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brasil
› Author Affiliations


Financial support The authors declare that they did not receive financial support from agencies in the public, private, or non-profit sectors to conduct the present study.
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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.

Work carried out at the Hospital São Paulo, outpatient clinic of the Knee Group, Department of Orthopedics and Traumatology, Escola Paulista de Medicina, Universidade Federal de São Paulo, São Paulo, SP, Brazil.




Publication History

Received: 28 April 2024

Accepted: 30 August 2024

Article published online:
12 March 2025

© 2025. The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution 4.0 International License, permitting copying and reproduction so long as the original work is given appropriate credit (https://creativecommons.org/licenses/by/4.0/)

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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