Osteoporosis in men with a history of tibial fracture

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Abstract
The long‐term effects of bone fractures on bone mineral density (BMD) at various skeletal sites are poorly established, although a serious fracture, such as a tibia fracture, followed by long immobility and disuse may lead to permanently decreased BMD and, through this mechanism, may be a risk factor for osteoporotic fractures in later life. To determine whether such an injury leads to osteoporosis, we measured the areal BMD (g/cm2) from the lumbar spine (L2–4), right distal radius and ulna, and the femoral neck, distal femur, patella, proximal tibia, distal tibia, and calcaneus of both extremities in 14 men with a history of primarily nonunited (finally bone‐grafted) shaft fracture of the tibia and 20 men with a history of primary union. For evaluation of the patients' BMD in the spine and distal forearm, 22 age‐, weight‐, and height‐matched normal men were also measured. The average time of immobilization in a long plaster cast was 27 weeks in the former group of patients and 16 weeks in the latter. The measurements were performed an average of 9 years after the fracture using a dual‐energy x‐ray absorptiometric scanner. Compared with normal men (mean ± SD = 1.116 ± 0.160), the spinal BMDs were significantly lower in men with a history of a primary nonunion (0.979 ± 0.100, −12.3%) and union (1.010 ± 0.124, −9.5%). In distal radius and distal ulna, there were no significant differences between the three groups. In the 14 patients with a primary nonunion, the mean BMD of the injured extremity (compared with the uninjured side) was significantly lower in the distal femur (‐10.0%), patella (‐11.2%), proximal tibia (‐9.2%), distal tibia (‐7.9%), and calcaneus (‐5.6%). In the 20 patients with a primary union, the side‐to‐side difference was significant in the femoral neck (‐2.4%), distal femur (‐4.0%), patella (‐3.7%), and proximal tibia (‐5.1%). The relative BMD of the injured extremity did not correlate with the fracture type, fracture location, or patients' age but did show significant (r = 0.41–0.79) positive correlation with short immobilization time, low pain assessment, good muscle strength, and high functional scores of the injured extremity. In conclusion, the tibial shaft fracture may be associated with reduced bone density in the lumbar spine and injured extremity. The observed decrease (10–12% in spine and 4–11% 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.

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