Bone mineral density in the distal radius and increased risk of fractures in haemodialysis

Sir,

We read with great interest the recent article by Urena et al. [1], which correlated the markedly decreased Z-score in the mid-radius with subsequent development of fractures. As opposed to the prevalent use of BMD, T-scores of <-2.5 to define osteoporosis [2], the Z-score is commonly used to identify the number of standard deviations for the mean of a healthy, age and gender-matched normal population and may be a better indicator for identification of osteoporosis in patients receiving steroids, post-transplant and those with chronic diseases.

Quite controversial is the preferred site for measurement of bone density. It is commonly felt that the risk of fracture at a particular site is dependent on the BMD at that site [3]. Most authorities recommend the measurement of BMD at the spine and hip as fractures in these areas have the most adverse effects on the individual's health. However, recent studies have revealed that forearm fractures are more important indicators of subsequent osteoporotic fractures at the hip (x2.7-fold in men, x1.6-fold in woman) [4]. Following a forearm fracture, the cumulative incidence of any fracture was 55% at 10 years and 80% by 20 years [4]. However, strangely enough, this fact is under-recognized and only 17% receive any form of pharmacological osteoporosis intervention within a year of sustaining a distal forearm fracture and visiting their physicians for a non-orthopaedic reason [5]. The current study illustrates that the forearm Z-score is markedly decreased in haemodialysis patients. Though not clearly demonstrated in this study, extrapolation of information from population studies of osteoporotic fractures, BMD density in the distal radius in the first quartile could increase their risks for future hip fractures to ~8/1000 patient years [6].

The role of biochemical markers of bone turnover is often indicated when the BMD is in the middle tertile, and any value above the upper limits of normal in pre-menopausal women is often an indicator to consider pharmacological treatment [7].

The current study highlights an often ignored site of bone mineral loss, i.e. the distal radius, and the increased propensity for fracture despite a normal BMD score at the hip and spine.

Conflict of interest statement. None declared.

Amit Kumar Ghosh

Division of Internal Medicine Mayo Clinic College of Medicine Rochester USA Email: ghosh.amit{at}mayo.edu

References

  1. Urena P, Bernard-Poenaru O, Ostertag A et al. Bone mineral density, biochemical markers and skeletal fractures in hemodialysis patients. Nephrol Dial Transplant 2003; 18: 2325–2331[Abstract/Free Full Text]
  2. Kanis J, Melton L III, Christiansen C. The diagnosis of osteoporosis. J Bone Miner Res 1994; 9: 1137–1141[ISI][Medline]
  3. Eastell R, Wahner HW, O’Fallon WM et al. Unequal decrease in bone density of lumbar spine and ultra distal radius in Colles’ and vertebral fracture syndromes. J Clin Invest 1989; 83: 168–174[ISI][Medline]
  4. Cuddihy MT, Gabriel SE, Crowson CS et al. Forearm fractures as predictors of subsequent osteoporotic fractures. Ostoporos Int 1999; 9: 469–475
  5. Cuddihy MT, Gabriel SE, Crowson et al. Osteoporosis intervention following distal forearm fractures. A missed opportunity? Arch Intern Med 2002; 162: 421–426[Abstract/Free Full Text]
  6. Cummings SR, Black DM, Nevitt MC et al. Study of Osteoporotic Fractures Research Group. Bone density at various sites for prediction of hip fracture. Lancet 1993; 341: 72[ISI][Medline]
  7. Christiansen C, Riis BJ, Rodbro P. Prediction of rapid bone loss in postmenopausal women. Lancet 1987; 1: 1106