J Bone Metab.  2019 May;26(2):123-131. 10.11005/jbm.2019.26.2.123.

Localization of Atypical Femoral Fracture on Straight and Bowed Femurs

Affiliations
  • 1Department of Orthopaedic Surgery, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, Korea.
  • 2Department of Orthopaedic Surgery, Gangnam Severance Hospital, Yonsei University College of Medicine, Seoul, Korea. kyang@yuhs.ac

Abstract

BACKGROUND
To elucidate the effect of anterolateral bowing on the fracture height of atypical femoral fractures (AFFs), we separated the AFFs into 2 groups according to the presence of anterolateral femoral bowing (straight group and bowing group) and analyzed the fracture height. The aims of this study were to evaluate the clinical and radiological features of AFFs in the straight group and bowing group, and to determine which factors were associated with the fracture height of AFFs in the total cohort and each subgroup.
METHODS
Ninety-nine patients with AFFs were included in this study (43 patients in the bowing group and 56 patients in the straight group). Clinical and radiological characteristics were compared between the groups. Multivariable linear regression analysis was performed to determine the effect of factors on fracture height.
RESULTS
Patients in the straight group were younger, heavier, and taller, and had a higher bone mineral density, smaller anterior and lateral bowing angles, and more proximal fracture height than those in the bowing group. Multivariable analysis showed that the presence of anterolateral bowing itself and height were associated with fracture height in the total cohort. In the subgroup analysis, the lateral bowing angle in the straight group and the estimated apex height in the bowing group were associated with fracture height. The lateral bowing angle was not significantly associated with fracture height in the total cohort and the bowing group.
CONCLUSIONS
The presence of anterolateral bowing and the level of the apex of the bowed femur were important factors for the fracture height of AFFs.

Keyword

Femoral fractures; Osteoporosis; Stress, mechanical

MeSH Terms

Bone Density
Cohort Studies
Femoral Fractures*
Femur*
Humans
Linear Models
Osteoporosis
Stress, Mechanical

Figure

  • Fig. 1 Grading system for anterolateral femoral bowing: grade 0 (straight) (A), grade I (mild) (B), grade II (moderate) (C), and grade III (severe) (D). [Modified from “Intramedullary nailing for atypical femoral fracture with excessive anterolateral bow-ing”, by Park YC, Song HK, Zheng XL, Yang KH, et al., 2017, J Bone Joint Surg Am, 99, p. 728. Copyright 2017 by the Journal of Bone and Joint Surgery. Reprinted with permission.]

  • Fig. 2 Measurement of the fracture height (F) and estimated apex height (A). Incomplete atypical femoral fracture with anterolateral bowing grade II (A). F ratio (%)=F/the entire femoral length (L) and fracture site (arrow) (B). The reference line (dashed line) is moved medially to find the tangent point in the medial side of the medial femoral cortex (C). The arrowhead indicates the A, which is at the same level of the tangent point of the medial side. A ratio (%)=A/L (D).

  • Fig. 3 Distribution of atypical femoral fractures in the straight group and bowing group.


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