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Tuesday, March 16, 2000

Bone mineral density returns after hip fracture

Studies have shown that elderly patients with osteoportic fractures of the hip have decreased bone mineral density (BMD) in the femoral neck in the first year following the fracture. However, a new prospective study of 21 patients found that between one and six years following the hip fractures there was a dramatic increase in BMD at both the femoral neck and lumbar spine measurement sites.

In many cases, the loss of BMD that occurred in the first year after a fracture was completely recouped, according to the study presented Wednesday in scientific paper 29.

The researchers observe that although the investigation is small, the results of the study suggest that pharmacological intervention with agents such as bisphosphonates to prevent accelerated loss of BMD after a hip fracture may not need to be continued indefinitely, if return to baseline BMD is the objective.

Although some studies have demonstrated a direct relationship between the level of activity and increased BMD, there was a general decrease in the functional activity level of patients in the six years following fracture. Therefore, there were no statistically significant relationships between changes in BMD and the functional mobility of patients, the researchers said.

BMD six years following fracture was greater than at the time of the injury in the lumbar spine for 10 of 21 patients (48 percent) and in the femoral neck for nine of 15 patients (60 percent). If weight-bearing demands were progressively shifted over time into the non-fractured hip due to declining function in the fracture hip, the researchers could hypothesize that mechanical factors might have contributed to the observed increases in femoral neck BMD. However, the findings could not explain the observed increase in lumbar spine BMD, the researchers said since the patients' overall level of functional ambulation decreased in the six years following fracture.

The mean dietary calcium intake increased from 640 mg(! 40 mg per day) at the time of fracture to 1,560 mg (180 mg per day) six years following the injury, but the researchers said there was no statistically significant connection between daily calcium intake and changes in BMD.

The researchers, all of the department of orthopaedics, University of North Carolina School of Medicine, Chapel Hill, N.C., are Douglas R. Dirschl, MD, associate professor of orthopaedics; Richard C. Henderson, MD, PhD, professor of orthopaedics; and Luis Piedrahita, MD, resident.

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Last modified 23/February/2000 by IS