Bone mineral density, biochemical markers and skeletal fractures in haemodialysis patients

End-stage renal disease is often associated with altered bone metabolism.

In order to investigate the determinant factors of bone mineral density (BMD) and the risk factors of fractures, we studied 70 patients; 26 women (23 post-menopausal) and 44 men, (mean+/-SD) aged 60.5+/-14.3 years, treated by standard haemodialysis (HD) for 6.4+/-6.8 years. Main circulating bone biochemical markers were assessed and BMD was measured with a Lunar DPX densitometer at five sites. BMD results are expressed as a function of age and gender (Z-score).

Mean Z-score was markedly decreased at the mid-radius (-2.75+/-1.23) whereas it was normal at the femoral neck (-0.42+/-1.13) and lumbar spine (0.02+/-2.13), and total body (-0.62+/-1.53). Time on HD was negatively correlated to the Z-score at the mid-radius and total body but not at the other sites. Serum intact parathyroid hormone (iPTH), whole PTH or cyclase activating PTH (CAP) and bone-specific alkaline phosphatase concentrations were negatively correlated with Z-scores at all sites. Twenty-one out of 70 patients had sustained a total of 27 fractures since the beginning of dialysis therapy (seven ribs, seven ankles, six vertebrae, three humerus, two wrists and two hips). They had a total body Z-score significantly lower than that of patients without fractures, -1.34+/-1.54 vs -0.37+/-1.46, respectively (P<0.031); however, their Z-scores at the other sites were not different. They were on HD for longer time, 10.4+/-9.5 vs 5.0+/-5.1, respectively (P<0.003), and the relative risk of skeletal fractures was 6.4 times greater after 10 years of HD. The seven patients with rib fractures had a decreased Z-score at most of the sites but not at the mid-radius. Rib fractures but no other fractures were associated with markedly decreased body weight, fat mass and serum leptin levels.

In conclusion, the Z-score at the mid-radius was decreased in HD patients and correlated with high serum PTH but not with fractures. Bone fractures were associated with the time passed on HD and with a low total body Z-score. Rib fractures were frequent and associated with a poor nutritional state.