Highlights
- •Fracture site was not significantly associated with distal anterior or distal lateral bowing in the present study.
- •DOC of the medullary canal was affected by the variable of proximal lateral and anterior bowing.
- •Geometric change of the proximal femur plays an important role in the fracture site and morphologic features of diaphyseal bowing.
- •New nail design for Asian atypical femur that could increase the radius of curve (ROC) but decrease the mediolateral angle needs to be introduced.
Abstract
Purpose
(1) To analyze three-dimensional (3D) morphologic features of atypical femur fracture
at actual size without projection error; and (2) to provide clinical implications
of cephalomedullary nail (CMN) fixation by separating the medullary canal and the
cortex.
Materials and methods
Fifty-nine atypical femurs (opposite non-fractured femurs) were reconstructed as 3D
models with medullary canal by importing CT data into Mimics® software. A reference
line was drawn from the tip of the greater trochanter to the center of the intercondylar
notch and used for classifying bowing grade according to the centerline of medulla.
Proximal and distal straight lines (length of 60 mm, diameter of 1 mm) were placed
in the centerline of medulla. Acute angles between the two straight lines were measured
as lateral and anterior bowing. The acute angle by straight line and reference line
was measured as proximal and distal bowing in both AP and lateral view. The diameter
of curve (DOC) of medulla along the posterior border was measured.
Results
The anterior bowing of all femur on lateral view was an average of 13.82° (range,
6.2°–31.1°, SD 3.91), and the values of proximal and distal anterior bowing were an
average of 7.82° (range, 2.7°-14.3°, SD 2.23) and 6.0° (range, 2.2°-16.8°, SD 2.31),
respectively. The lateral bowing of all femur on AP view was an average of 5.49° (range,
0.1°–17.3°, SD 4.48), and the values of proximal and distal anterior bowing were an
average of 3.64° (range, 0.1°-11.3°, SD 2.70) and 2.48° (range, 0-7.4°, SD 1.98),
respectively. The medullary canal was changed to be straightened and more bowed anteriorly.
Concerning the lateral bowing grade of entire diaphysis, it was grade -I for 15 femurs,
grade 0 for 21 femurs, grade I for nine femurs, grade II for five femurs, and grade
III for nine femurs. Regarding anterior bowing grade, it was grade II for 14 femurs
and grade III for 45 femurs. The average diameter of medullary canal was 1276.3 ±
232.25 mm.
Conclusion
Asian atypical femur had three morphologic features: (1) straightened medullary canal,
(2) positive values of lateral bowing, and (3) significantly increased ante-curvature
of medullary canal. Considering that conventional CMN had about 4° of mediolateral
angle, the disparity between implant and medullary canal might be clear. Thus, new
nail design for Asian atypical femur that could increase the radius of curve (ROC)
but decrease the mediolateral angle needs to be introduced.
Keywords
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Article info
Publication history
Published online: September 24, 2022
Accepted:
September 23,
2022
Identification
Copyright
© 2022 Elsevier Ltd. All rights reserved.
