The Muscle-bone Relationship in Cystic Fibrosis Patients

Overview

Objectives:
The multisystem involvement in cystic fibrosis (CF) patients may alter body composition and influence bone metabolism, leading to low bone mineral density and lean body mass depletion. Peripheral quantitative computed tomography (pQCT) allows assessment of volumetric bone mineral density and assessment of the relationship between bones and muscles.

Methods:
This study was conducted in 80 CF patients (aged 4.5–44.9 years, 36 female, 73% <18 years). Using pQCT, trabecular bone mineral density (TBD) in distal radius, cortical bone mineral density in proximal radius (CBD) and cross-section areas (CSA) of bone components and muscles in proximal forearm of the nondominant side were measured.

Results:
Weight, height and BMI of the patients were lower than in the normal population (mean SDS -1.13, -0.99 and -0.89, respectively, p<0.0001). TBD was not lower than normal (mean SDS 0.43, p = 0.064), CBD was higher than normal (mean value of SDS 0.38, p = 0.005). Cortical bone CSA and cortical thickness were small for age (mean value of SDS -0.95 and -0.93, p = <0.0001), but cortical bone CSA was appropriate for proximal forearm muscle CSA. Proximal forearm muscle CSA was smaller than both height-matched and age-matched references (mean value of SDS -1.84 and -1.41, p <0.0001 and <0.001, respectively).

Conclusions:
The thinner cortical bone found in CF patients may be due to their lower muscle mass. Changes in bone mineral density in CF have to be evaluated with caution.

Key words:
cystic fibrosis, bone mineral density, osteoporosis, pQCT