title: Low bone mineral density and fat-free mass in younger patients with a femoral neck fracture.
abstract: BACKGROUND
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Division of Orthopaedics, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Karolinska University Hospital, Huddinge, Stockholm, Sweden.
authors.forename: Amer N
authors.initials: AN
authors.lastname: Al-Ani
authors.affiliation: Department of Public Health and Caring Sciences, Clinical Nutrition and Metabolism, Uppsala University, Uppsala, Sweden.|Department of Geriatric Medicine, Uppsala University Hospital, Uppsala, Sweden.
authors.forename: Tommy
authors.initials: T
authors.lastname: Cederholm
authors.affiliation: Department of Molecular Medicine and Surgery, Endocrine and Diabetes Unit, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Maria
authors.initials: M
authors.lastname: Sääf
authors.affiliation: Division of Orthopaedics, Department of Clinical Sciences, Karolinska Institutet, Danderyd Hospital, Stockholm, Sweden.
authors.forename: Gustaf
authors.initials: G
authors.lastname: Neander
authors.affiliation: Karolinska Instistutet, Department of Clinical Science and Education, Orthopaedic Unit, Söder hospital, Stockholm, Sweden.
authors.forename: Richard
authors.initials: R
authors.lastname: Blomfeldt
authors.affiliation: Department of Molecular Medicine and Surgery, Section of Orthopaedics and Sports Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Wilhelmina
authors.initials: W
authors.lastname: Ekström
authors.affiliation: Division of Orthopaedics, Department of Clinical Science Intervention and Technology, Karolinska Institutet, Karolinska University Hospital, Huddinge, Stockholm, Sweden.
authors.forename: Margareta
authors.initials: M
authors.lastname: Hedström
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D017677:Age Distribution; D000368:Aged; D001823:Body Composition; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000000981:diagnostic imaging / Q000453:epidemiology; D005260:Female; D005265:Femoral Neck Fractures / Q000453:epidemiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000453:epidemiology*; D012307:Risk Factors; D055948:Sarcopenia / Q000000981:diagnostic imaging / Q000453:epidemiology*; D055815:Young Adult
keywords: Body composition; bone mineral density; fat-free mass index; femoral neck fracture; trauma mechanism and young age