Influence de la flexion et de la rotation latérale combinées de la hanche sur les mensurations morphométriques du fémur proximal sur des radiographies de bassin de face - 11/06/18
Effect of combined flexion and external rotation on measurements of the proximal femur from anteroposterior pelvic radiographs
Abstract |
Introduction |
Fixed flexion and external rotation contractures are common in patients with hip osteoarthritis and in particular before total hip replacement (THR). We aimed to answer the following question: how does combined flexion and external rotation of the femur influence the radiographic assessment of 1) femoral offset (FO) 2) neck-shaft angle (NSA) and 3) distance (parallel to the femoral axis) from greater trochanter to femoral head centre (GT-FHC)?
Hypothesis |
Combined flexion and external rotation impact the accuracy of two-dimensional (2D) proximal femur measurements.
Materials and methods |
Three-dimensional (3D) CT segmentations of the right femur from 30 male and 42 female subjects were acquired and used to build a statistical shape model. A cohort (n=100; M:F=50:50) of shapes was generated using the model. Each 3D femur was subjected to external rotation (0°–50°) followed by flexion (0°–50°) in 10° increments. Simulated radiographs of each femur in these orientations were produced. Measurements of FO, NSA and GT-FHC were automatically taken on the 2D images.
Results |
Combined rotations influenced the measurement of FO (p<0.05), NSA (p<0.001) and GT-FHC (p<0.001). Femoral offset was affected predominantly by external rotation (19.8±2.6mm [12.2 to 26.1mm] underestimated at 50°); added flexion in combined rotations only slightly impacted measurement error (20.7±3.1mm [13.2 to 28.8mm] underestimated at 50° combined). Neck-shaft angle was reduced with flexion when external rotation was low (9.5±2.1° [4.4 to 14.2°] underestimated at 0° external and 50° flexion) and increased with flexion when external rotation was high (24.4±3.9° [15.7 to 31.9°] overestimated at 50° external and 50° flexion). Femoral head centre was above GT by 17.0±3.4mm [3.9 to 22.1mm] at 50° external and 50°flexion. In contrast, in neutral rotation, FHC was 12.2±3.4mm [3.9 to 22.1mm] below GT.
Discussion |
This investigation adds to current understanding of the effect of femoral orientation on preoperative planning measurements through the study of combined rotations (as opposed to single-axis). Planning measurements are shown to be significantly affected by flexion, external rotation, and their interaction.
Level of evidence |
IV Biomechanical study.
Le texte complet de cet article est disponible en PDF.Keywords : Femoral orientation, Preoperative planning, Femoral offset, Neck-shaft angle
| ☆ | Presented to Closed Meeting International Hip Society, London September 2017. |
| ☆☆ | Cet article peut être consulté in extenso dans la version anglaise de la revue Orthopaedics & Traumatology: Surgery & Research sur Science Direct (sciencedirect.com) en utilisant le DOI ci-dessus. |
Vol 104 - N° 4
P. 312 - juin 2018 Retour au numéro
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