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Abstract In designing femoral components, which restore native (i.e., healthy) knee kinematics, the flexion–extension (F-E) axis of the tibiofemoral joint should match that of the native knee. Because the F–E axis is governed by the curvature of the femoral condyles in the sagittal plane, the primary objective was to determine the variation in radii of curvature. Eleven high accuracy three-dimensional (3D) femur models were generated from ultrahigh resolution CT scans. The sagittal profile of each condyle was created. The radii of curvature at 15 deg increments of arc length were determined based on segment circles best-fit to ±15 deg of arc at each increment. Results were standardized to the radius of the best-fit overall circle to 15 deg–105 deg for the femoral condyle having a radius closest to the mean radius. Medial and lateral femoral condyles exhibited multiradius of curvature sagittal profiles where the radius decreased at 30 deg flexion by 10 mm and at 15 deg flexion by 8 mm, respectively. On either side of the decrease, radii of segment circles were relatively constant. Beyond the transition angles where the radii decreased, the anterior-posterior (A-P) positions of the centers of curvature varied 4.8 mm and 2.3 mm for the medial and lateral condyles, respectively. A two-radius of curvature profile approximates the radii of curvature of both native femoral condyles, but the transition angles differ with the transition angle of the medial femoral condyle occurring about 15 deg later in flexion. Owing to variation in A-P positions of centers of curvature, the F-E axis is not strictly fixed in the femur.
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This content will become publicly available on August 1, 2026
Improving Femoral Torsion Evaluation in Infants Through Analysis of Variability and Reliability in Two-Dimensional and Three-Dimensional Imaging Measurements of the Femoral Neck Axis
Abstract The femoral neck axis serves as a critical parameter in evaluating hip joint health, particularly in the pediatric population. Commonly used metrics for evaluating femoral torsion, such as the femoral neck-shaft and femoral anteversion angles, rely heavily on precise definitions of the position and orientation of the femoral neck axis. Current measurement methods employing radiographs and performing two-dimensional (2D) measurements on computed tomography (CT) scans are susceptible to errors due to their reliance on reader experience and the inherent limitations in 2D measurements. We hypothesized that utilizing volumetric data would mitigate these errors and enable more accurate and reproducible measurements of the femoral neck axis using the femoral anteversion and femoral neck-shaft angles. To test this hypothesis, we analyzed a historical collection of postmortem infant femoral and pelvic bones (28 hips) aged 0 to 6.5 months, with an average estimated age of 4.68 ± 1.80 months. Our findings revealed an average neck-shaft angle of 128.00 ± 4.92 deg and femoral anteversion angle of 35.56 ± 11.68 deg across all femurs, consistent with literature values. These measurements obtained from volumetric image data were found to be repeatable and reliable compared to conventional methods. Our study suggests that the proposed methodology offers a standardized approach for obtaining repeatable and reproducible measurements, thus potentially enhancing diagnostic accuracy and clinical decision-making in assessing hip developmental conditions in pediatric patients.
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- Award ID(s):
- 2238859
- PAR ID:
- 10609884
- Publisher / Repository:
- American Society of Mechanical Engineers Digital Collection
- Date Published:
- Journal Name:
- Journal of Engineering and Science in Medical Diagnostics and Therapy
- Volume:
- 8
- Issue:
- 3
- ISSN:
- 2572-7958
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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