June 08, 2018
By Marilynn Larkin
NEW YORK (Reuters Health) - Various image analysis techniques show sex-specific patterns of bone deterioration at the hip, suggesting that men and women should be assessed differently for hip fracture risk, researchers say.
"One major contribution of this work is the integration of data-driven computational anatomy approaches, which showed that proximal femur fragility linked to fracture seems to be localized rather than uniform in both men and women," Dr. Elisa Marques told Reuters Health by email.
"In that regard, the incorporation of CT and computational anatomy techniques might be quite useful for research and clinical efforts, as well as for designing targeted interventions and properly assessing their success," said Dr. Marques, who was a postdoctoral fellow at the U.S. National Institute on Aging during the study and now is at the University of Maia in Portugal.
Dr. Marques and colleagues analyzed imaging data from 334 people (60% women) who had a hip fracture and 1,047 controls (54% women), all with a mean age of 77 and all participants in the AGES-Reykjavic study of Icelandic men and women.
Baseline (before hip fracture) computed tomography scans of the hip were analyzed using voxel-based morphometry, tensor-based morphometry, and surface-based statistical parametric mapping to assess the spatial distribution of volumetric bone mineral density (vBMD), internal structure, and cortical bone properties of the proximal femur: thickness, vBMD and trabecular vBMD adjacent to the endosteal surface.
As reported online May 17 in Bone, in both men and women, the superior aspect of the femoral neck and the trochanteric region - except for cortical bone thickness - were consistently associated with incident hip fracture.
Differences in bone properties between noncases and incident hip fracture cases followed similar trends in both men and women, were located at compatible regions, and showed heterogeneity in the spatial distribution of their magnitude, with focal regions showing greater differences.
Most of the regions with a significant interaction between fracture group and sex showed differences of greater magnitude in men than in women between noncases and hip fracture cases, with different spatial distributions for all bone properties, with the exception of cortical bone thickness.
While most of these regions showed better bone quality in male than in female cases, female cases showed higher vBMD in the principal compressive group and higher endotrabecular vBMD at several regions, including the anterior, posterior, and lateral aspects of the proximal femur.
"These findings indicate the value of these image analysis techniques by providing unique information about the specific patterns of bone deterioration associated with incident hip fracture and their sex differences, highlighting the importance of looking to men and women separately in the assessment of hip fracture risk," the authors conclude.
Dr. Michael B. Gerhard, an orthopedic surgeon at Cedars-Sinai Kerlan-Jobe Institute in Los Angeles, commented by email, "Previous bone density tests were performed using a DEXA scan, which can generically show if someone's hip has diminished bone density."
"However," he told Reuters Health, "this study uses a specialized CT scan mapping system that can not only identify a hip with diminished bone density but can accurately map which parts of the hip bone are affected. This technology may allow us to more accurately identify patients who are at risk for hip fracture and therefore more aggressively engage that patient in hip fracture prevention strategies."
"The biggest downside is that CT scans expose patients to ionizing radiation," said Dr. Gerhard, who was not involved in the study. "Although the exposure is fairly low, there is a theoretical risk of the radiation putting the patient at higher risk of developing a tumor in the future. While the risk is low, in an elderly patient it is not negligible."
"The findings could have 'real-world' implications in two major ways," he noted. "The first is in changing the paradigm of how we currently screen for bone density deficits. Based on the results of this study it would seem reasonable to change (from bone densitometry) to a CT-based technology."
"The CT scan-based screening could not only tell us who has bone density deficits in the hip, but can specifically map the bone density and tell us which parts of the hip are specifically lacking in density," he said.
"For example, if the bone weakness occurs in the trochenteric region, then certain abductor strengthening exercises may be more important for hip fracture prevention than what we previously recommended, which was simple weight bearing exercise such as walking," he explained. "We could target our prevention strategies specifically on the part of the hip that is most afflicted."
"Hopefully, this will lead to fewer hip fractures in our elderly population," Dr. Gerhard concluded.
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