Reduced bone mineral density in men with a previous femur fracture

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Abstract
This study determined the areal bone mineral density (BMD) from the lumbar spine (L2–4), right distal radius and ulna, and the femoral neck, trochanter area of the femur, distal femur, patella, proximal tibia, and calcaneus of both extremities in 29 men who had a femur shaft fracture 10 years earlier. For evaluation of the patients' BMDs in the spine and distal forearm, 29 age‐, weight‐, and height‐matched normal men were also measured. Compared with normal men (mean ± SD = 1.123 ± 0.153), the spinal BMDs of the patients were significantly (p = 0.0054) lower (1.018 ± 0.119, −9.3%). Distal radius and distal ulna showed no significant group differences. In patients, the mean BMD of the injured extremity (compared with the uninjured side) was significantly lower in the distal femur (‐6.8%; p = 0.0000), patella (‐5.4%; p = 0.0000), proximal tibia (‐4.7%; p = 0.0000), and calcaneus (‐2.2%; p = 0.0259). In the proximal femur, this value was at the same level (femoral neck 1.3%, NS) or higher (trochanter area 6.3%, p = 0.0002) than that in the uninjured extremity. The relative BMDs of the injured extremity did not associate with the fracture type, fracture location, age, muscle strength, follow‐up time, or non‐weight‐bearing time but showed significant (r = 0.33–0.64) positive correlation with low pain assessment and high functional scores of the injured extremity. The relative BMDs were especially strongly associated with the four‐step functional classification of the International Knee Documentation Committee: the higher the functional class of the injured extremity, the less bone loss caused by the injury (p = 0.0001–0.0328). In conclusion, the femur shaft fracture results in permanently reduced bone density in the lumbar spine and lower parts of the injured extremity. The proximal femur is not affected. The observed decrease (9% in spine and 5–7% in the knee region of the injured limb) is clinically important with respect to age‐related bone loss of 1% per year after the age of peak bone mass. Additional follow‐up is needed to determine any increased risk of osteoporotic fractures in spine and injured extremity. Recovery of normal limb function seems to be crucial for good bony recovery.
Funding Information
  • Finnish Ministry of Education

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