Low bone mineral density and fat-free mass in younger patients with a femoral neck fracture.

Abstract

Reduced bone mineral density (BMD) together with muscle wasting and dysfunction, that is sarcopenia, emerges as a risk factor for hip fracture. The aim of this study was to examine body composition and BMD and their relationship with trauma mechanisms in young and middle-aged patients with femoral neck fracture. Altogether, 185 patients with femoral neck fracture aged 20-69 were included. BMD, body composition and fat-free mass index (FFMI) were determined by dual-X-ray absorptiometry (DXA), and trauma mechanisms were registered. Ninety per cent of the whole study population had a femoral neck BMD below the mean for age. In the young patients (< 50 years), 27% had a Z-score of BMD ≤ -2 SD. More than half of the middle-aged patients (50-69 years) had osteopenia, that is T-score -1 to -2.5, and 35% had osteoporosis, that is T-score < -2.5, at the femoral neck. Patients with low-energy trauma, sport injury or high-energy trauma had a median standardised BMD of 0.702, 0.740 vs. 0.803 g/cm(2) (P = 0.03), and a median FFMI of 15.9, 17.7 vs. 17.5 kg/m(2) (P < 0.001), respectively. FFMI < 10th percentile of an age- and gender-matched reference population was observed in one-third. A majority had low BMD at the femoral neck, and one-third had reduced FFMI (i.e. sarcopenia). Patients with fracture following low-energy trauma had significantly lower femoral neck BMD and FFMI than patients with other trauma mechanisms. DXA examination of both BMD and body composition could be of value especially in those with low-energy trauma.