Statistical shape modeling of femur shape variability in female patients with hip dysplasia

Abstract

Although increasing evidence suggests that abnormal femur geometry in developmental dysplasia of the hip (DDH) may contribute to intra-articular damage and the development of hip osteoarthritis, a comprehensive 3D description of femoral abnormalities in DDH remains incomplete. Statistical shape modeling (SSM) was used to quantify three-dimensional (3D) geometric variation among femurs in female patients with DDH and control subjects. SSM correspondence points (n = 8,192) were placed on each femur using a gradient descent energy function to derive mean DDH and control femoral shapes and principal component analysis (PCA) was then used to describe shape variation. PCA results were associated with common 2D radiographic measures of femur shape using general linear models. For patients with DDH, the first eight principal components (modes) captured 90.9% of the cumulative variance accounted for (VAF). Notably, mode 2 captured 23.6% VAF and described variation in femoral version, the neck-shaft angle, and femoral neck length, while mode 3 captured 16.4% VAF and described variation in femoral version, femoral head size, and femoral offset. SSM captured complex geometric deformities in DDH, which may not be fully described by 2D measures of the acetabulum and proximal femur alone. By determining the primary shape variations among femurs in cases of DDH, SSM may further understanding of pathologies on the femoral side of dysplastic hips, in context with more commonly recognized acetabular deformities. This article is protected by copyright. All rights reserved

Unpicking observational relationships between hip shape and osteoarthritis: hype or hope?

“…although computed tomography and magnetic resonance imaging have both been used for three dimensional (3D) shape modelling (14,15), they have yet to feature in large scale epidemiological studies described here.…”

Subregional statistical shape modelling identifies lesser trochanter size as a possible risk factor for radiographic hip osteoarthritis, a cross-sectional analysis from the Osteoporotic Fractures in Men Study

“…3D hip shape measured by SSM is increasingly viable as computational power improves but is restricted to small cohorts due to the increased cost and radiation exposure involved in acquiring the CT scans. Recently, 3D SSM was used to show the difference in femoral shape between DDH and controls 17 and, previously, 3D SSM combined with density measures (statistical shape and density modelling) was used to show associations between hip shape and density and the risk of hip fracture 18 . Cohorts with both 2D and 3D hip shape data provide an opportunity to explore whether 2D hip shape models accurately reflect the underlying shape of the hip or whether they are affected by inadequate positioning during image acquisition.…”

The effect of pelvic tilt on three‐dimensional coverage of the femoral head: A computational simulation study using patient‐specific anatomy

“…However, it is important to note that the analysis herein was based on asymptomatic, morphologically normal subjects. Results could change if patients with FAIS, DDH, and acetabular retroversion were included as these patients often present with hips that are irregular in shape (Gaffney, Hillen, Nepple, Clohisy, & Harris, 2019; Harris, Reese, Peters, Weiss, & Anderson, 2013; Nepple et al, 2017). Future research should clarify the relationship between regional coverage and the PSI.…”