Thigh Muscle Composition and Its Relationship to Functional Recovery Post Hip Fracture Over Time and Between Sexes

Abstract

Background: Computed tomography (CT)-scan measures of muscle composition may be associated with recovery post hip fracture.

Methods: In an ancillary study to Baltimore Hip Studies Seventh cohort, older adults were evaluated at 2 and 6 months post hip fracture. CT-scan measures of muscle were acquired at 2 months. Short Physical Performance Battery (SPPB) was measured at 2 and 6 months. Generalized estimating equations were used to model the association of muscle measures and physical function, adjusting for age, sex, body mass index, and time postfracture.

Results: Seventy-one older adults (52% males, age 79.6 ± 7.3 years) were included. At 2-months, males had greater thigh cross-sectional area (CSA, p < .0001) and less low-density muscle (p = .047), and intermuscular adipose tissue (p = .007) than females on the side of the fracture, while females performed better on the SPPB (p = .05). Muscle measures on the fractured side were associated with function at 2 months in both sexes. Participants with the lowest tertile of muscle CSA difference at 2-months, indicating greater symmetry in CSA between limbs, performed better than the other 2 tertiles at 6-months. Males performed worse in functional measures at baseline and did not recover as well as females (p = .02).

Conclusion: CT-scan measures of muscle CSA and fatty infiltration were associated with function at 2-months post hip fracture and with improvement in function by 6 months. Observed sex differences in these associations suggest that rehabilitation strategies may need to be adapted by sex after hip fracture.

Keywords: Computed tomography (CT scan); Physical function; Sex differences.

Figure 1.

GEE Model 2 of fractured side muscle cross-sectional area (CSA) at 2 months depicted in tertiles for the 3 functional measures (A) gait speed, p ≤ .005; (B) chair rise time, p ≤ .001; and (C) SPPB score, p = .008. p values are for GEE model run with continuous muscle CSA and functional measures data. GEE = generalized estimating equations; SPPB = Short Physical Performance Battery.

Figure 2.

GEE Model 2 between fractured side muscle attenuation (MA) at 2 months depicted in tertiles for the functional measures (A) gait speed, p ≤ .05. Post hoc testing; *p = .03 between tertile 1 (lower) and 2 (mid), **p = .03 between tertile 1 and 3 (upper), and +p = .03 between tertile 2 and 3 and (B) SPPB Score. GEE = generalized estimating equations; SPPB = Short Physical Performance Battery.

Figure 3.

Association of muscle CSA difference with time-dependent change from 2 to 6 months (Model 1) depicted by tertiles in (A) gait speed, p = .06 (B) and SPPB score, p ≤ .01. p values are for GEE models run with continuous muscle composition and functional measures data. CSA = cross-sectional area; GEE = generalized estimating equations; SPPB = Short Physical Performance Battery.

Figure 4.

GEE Model 2 including sex and (A) chair rise time, *p ≤ .01; (B) SPPB score, #p ≤ .05; and (C) association of sex with time-dependent change from 2 to 6 months in chair rise time, p = .02. GEE = generalized estimating equations; SPPB = Short Physical Performance Battery.