Introduction The association between combat-related traumatic injury (CRTI) and bone health is uncertain. A disproportionate number of lower limb amputees from the Afghanistan conflict are diagnosed with osteopenia/osteoporosis, increasing lifetime risk of fragility fracture and challenging traditional osteoporosis treatment paradigms.

It was hypothesised that CRTI results in a reduction in Bone Mineral Density (BMD). Specifically, a localised BMD reduction in the amputated limb of lower limb amputees that is progressively greater with higher level amputations.

Method Cross-sectional analysis of the first phase of a cohort study comprising 579 male adult UK military personnel with CRTI (UK-Afghanistan War 2003–2014; including 153 lower limb amputees) who were frequency-matched to 565 uninjured men by age, service, rank, regiment, deployment period, and role-in-theatre. BMD was assessed using DEXA scanning of the hips and lumbar spine.

Results Femoral neck BMD was lower in the CRTI than the uninjured group (T-score -0.08 vs -0.42 p=0.000). Subgroup analysis revealed this reduction was significant only at the femoral neck of the amputated limb of amputees (p=0.000), where the reduction was greater for above knee amputees than below knee amputees (p=0.037). There were no differences in spine BMD.

Conclusion Changes in bone health in CRTI appear to be mechanically driven rather than systemic. This may arise from altered joint and muscle loading creating a reduced mechanical stimulus to the femur. These findings support a lexicon change to unloading osteopenia and should not be associated with a diagnosis of systemic osteoporosis nor systemic treatments.