OSTEOPOROSIS IN MEN WITH A HISTORY OF TIBIAL FRACTURE

The long-term effects of bone fractures on bone mineral density (BMD) at various skeletal sites are poorly established, although a serious f racture, such as a tibia fracture, followed by long immobility and dis use may lead to permanently decreased BMD and, through this mechanism, maybe a risk factor for osteoporotic fractures in later life. To dete rmine whether such an injury leads to osteoporosis, we measured the ar eal BMD (g/cm(2)) from the lumbar spine (L2-4), right distal radius an d ulna, and the femoral neck, distal femur, patella, proximal tibia, d istal tibia, and calcaneus of both extremities in 14 men with a histor y of primarily nonunited (finally bone-grafted) shaft fracture of the tibia and 20 men with a history of primary union. For evaluation of th e patients' BMD in the spine and distal forearm, 22 age-, weight-, and height-matched normal men were also measured. The average time of imm obilization 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 abs orptiometric scanner. Compared with normal men (mean +/- SD = 1.116 +/ - 0.160), the spinal BMDs were significantly lower in men with a histo ry 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 signi ficant differences between the three groups. In the 14 patients with a primary nonunion, the mean BMD of the injured extremity (compared wit h the uninjured side) was significantly lower in the distal femur (-10 .0%), patella (-11.2%), proximal tibia (-9.2%), distal tibia(-7.9%), a nd calcaneus (-5.6%). In the 20 patients with a primary union, the sid e-to-side difference was significant in the femoral neck(-2.4%), dista l femur(-4.0%), patella(-3.7%), and proximal tibia (-5.1%). The relati ve BMD of the injured extremity did not correlate with the fracture ty pe, fracture location, or patients' age but did show significant (r = 0.41-0.79) positive correlation with short immobilization time, low pa in assessment, good muscle strength, and high functional scores of the injured extremity. In conclusion, the tibial shaft fracture may be as sociated with reduced bone density in the lumbar spine and injured ext remity. The observed decrease (10-12% in spine and 4-11% in the knee r egion 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. Add itional follow-up is needed to determine any increased risk of osteopo rotic fractures in spine and injured extremity.