Trunk Muscle Composition 2 Months After Hip Fracture: Findings From the Baltimore Hip Studies.

ABSTRACT

OBJECTIVE: To determine if hip fracture patients would have smaller cross-sectional area (CSA) and lower radiological attenuation (suggesting greater fat infiltration) in all trunk muscles as compared to older adults without hip fractures. DESIGN: Cross-sectional analysis of computed tomography (CT) scans. SETTING: Clinical imaging facility. PARTICIPANTS: Forty-one white participants (19 men, 22 women) from the Baltimore Hip Studies seventh cohort at 2 months postfracture were compared to 693 white participants (424 men, 269 women) from the Health, Aging and Body Composition (Health ABC) study at the year 6 visit (N=734). INTERVENTION Not applicable. MAIN OUTCOME MEASURES: Trunk muscle CSA and attenuation values were obtained from a single 10-mm, axial CT scan completed at the L4-L5 disc space in each participant. RESULTS: The hip fracture cohort had significantly smaller CSA for all trunk muscles (range 12.1%-38% smaller) compared to the Health ABC cohort (P<.01), with the exception of the rectus abdominus muscle in men (P=.12). But, hip fracture patients, particularly female patients, had higher attenuation levels (lower intramuscular fat) in all trunk muscles (P<.0001). CONCLUSIONS: Findings are consistent with atrophy of the trunk muscles in the hip fracture population without a high level of intramuscular fat. Future work should evaluate the role of trunk muscle composition in the functional recovery of older adults after hip fracture.