Abstract
In humans, there is clear evidence of an association between hip fracture risk and femoral neck bone mineral density, and some evidence of an association between fracture risk and the shape of the proximal femur. Here, we investigate whether the femoral cortex plays a role in these associations: do particular morphologies predispose to weaker cortices? To answer this question, we used cortical bone mapping to measure the distribution of cortical mass surface density (CMSD, mg/cm2) in a cohort of 125 females. Principal component analysis of the femoral surfaces identified three modes of shape variation accounting for 65% of the population variance. We then used statistical parametric mapping (SPM) to locate regions of the cortex where CMSD depends on shape, allowing for age. Our principal findings were increased CMSD with increased gracility over much of the proximal femur; and decreased CMSD at the superior femoral neck, coupled with increased CMSD at the calcar femorale, with increasing neck-shaft angle. In obtaining these results, we studied the role of spatial normalization in SPM, identifying systematic misregistration as a major impediment to the joint analysis of CMSD and shape. Through a series of experiments on synthetic data, we evaluated a number of registration methods for spatial normalization, concluding that only those predicated on an explicit set of homologous landmarks are suitable for this kind of analysis. The emergent methodology amounts to an extension of Geometric Morphometric Image Analysis to the domain of textured surfaces, alongside a protocol for labelling homologous landmarks in clinical CT scans of the human proximal femur.
Highlights
Hip fractures are the most common cause of acute orthopaedic hospital admission in older people (Parker and Johansen, 2006), with their annual incidence projected to rise worldwide from 1.7 million in 1990 to 6.3 million in 2050 (Sambrook and Cooper, 2006)
Statistical parametric mapping (SPM) (Friston et al, 1994) can be used to analyse large cohorts of the textured surfaces (Tucholka et al, 2012; Worsley et al, 2009), in order to deduce, for example, how the cortical property depends on age, sex or group
How could we possibly address questions such as “How does the surface’s texture depend on its shape?” And yet such questions are theoretically intriguing and practically enticing, since femoral shape appears to affect fracture risk (Gregory and Aspden, 2008) and bone mineral density (Machado et al, 2014)
Summary
Hip fractures are the most common cause of acute orthopaedic hospital admission in older people (Parker and Johansen, 2006), with their annual incidence projected to rise worldwide from 1.7 million in 1990 to 6.3 million in 2050 (Sambrook and Cooper, 2006). Statistical parametric mapping (SPM) (Friston et al, 1994) can be used to analyse large cohorts of the textured surfaces (Tucholka et al, 2012; Worsley et al, 2009), in order to deduce, for example, how the cortical property depends on age, sex or group Analyses of this nature have shed light on focal defects that appear to play a role in fracture risk (Treece et al, 2015; Poole et al, 2017; 2012), and the efficacy of exercise (Allison et al, 2015) and pharmaceuticals (Whitmarsh et al, 2016; Poole et al, 2015; Whitmarsh et al, 2015; Poole et al, 2011) in targeting these defects.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
