Distal forearm fracture as risk factor for vertebral osteoporosisBMJ 1994; 308 doi: https://doi.org/10.1136/bmj.308.6943.1543 (Published 11 June 1994) Cite this as: BMJ 1994;308:1543
- N F A Peel,
- N A Barrington,
- T W D Smith,
- R Eastell
- Department of Human Metabolism and Clinical Biochemistry, University of Sheffield, Sheffield
- Department of Diagnostic Imagine and Orthopaedics, Northern General Hospital, Sheffield S5 7AU
- Correspondence to: Dr R Eastell, Clinical Sciences Centre, Northern General Hospital, Sheffield S5 7AU
- Accepted 3 March 1994
Fractures of the vertebral body and of the distal forearm are typical manifestations of type I or postmenopausal osteoporosis,1 but the association between the two fractures in individual women is not clear. In type I osteoporosis vertebral fractures are associated with low bone mineral density of the lumbar spine, and the risk of vertebral fracture increases two to three times with each standard deviation decrease in bone mineral density.2 We aimed to determine whether a fracture of the distal forearm in postmenopausal women indicated an increased risk of vertebral osteoporosis.
Patients, methods,and results
We identified 127 women aged 50 to 82 (mean 64.7 years) from records in the radiology department and fracture clinic who had a fracture of the distal forearm within the previous three years (62% uptake); 375 women aged 50 to 85 years (mean 64.6 years) were randomly selected from three general practice populations in Sheffield (55% uptake). Twelve women with previous fractures of their distal forearm were excluded from the population based group. Bone mineral density of the lumbar spine was measured using dual energy x ray absorptiometry (Lunar DPX, Lunar Corporation, Madison, WI). Each subject gave informed consent and the study was approved by the ethics committee of this hospital. Differences in the bone mineral density of the lumbar spine were examined by comparing Z scores (normalised for age and weight and expressed as units of standard deviation from the expected value) using analysis of variance with Bonferroni correction. The slopes and intercepts of regression lines were compared using dummy variables according to the method of Kleinbaum and Kupper.3
We found no difference between the women with distal forearm fracture and the population based group with respect to age (mean 64.7 v 64.6 years), time since the menopause (17.0 v 17.9 years), height (mean 1.580 v 1.585 m), or weight (mean 65.3 v 66.0 kg). Bone mineral density in the women with distal forearm fractures was lower after correction for age and weight than that in the population based controls (mean Z score -0.46 (95% confidence interval of the difference -0.63 to -0.29)). Bone mineral density in younger women with distal forearm fractures was lower than that in older women (ages 50 to 59, mean Z score -0.72 (-1.0 to -0.45); ages 60 to 69, -0.48 (-0.78 to -0.19); ages >=70, -0.11 (-0.41 to 0.9)). The figure shows the relation between bone mineral density and age in women with distal forearm fractures and the population based group. The intercepts (P=0.001) and slopes (P=0.006) of the regression lines were different.
We found decreased bone mineral density of the lumbar spine in a group of women with fracture of the distal forearm, indicating an increased risk of vertebral fracture. This decrease was significant only in the younger women with distal forearm fracture. It was notable that in the women with distal forearm fractures bone mineral density of the lumbar spine did not decrease with aging. This cross sectional design does not allow us to determine whether these subjects had low peak bone mass or had undergone accelerated bone loss.
The type I-type II classification of osteoporosis proposes that distal forearm fracture is a type I fracture. This may be an oversimplification. We found that in women under 60 distal forearm fracture in women strongly associated with low bone mineral density of the lunbar spine, and in this case it may be appropriate to consider it a type I fracture. Owen et al found no association between distal forearm fracture in women under 60 and subsequent hip fracture, a classic type II fracture.4 We found that in older women, however, distal forearm fracture did not predict low bone mineral density of the lumbar spine, and Owen et al showed that the risk of hip fracture is doubled in women who sustain a distal forearm fracture after the age of 70. In older women distal forearm fracture may therefore be considered a type II fracture.
We concluded that it may be worth while to measure bone density in women with distal forearm fracture in the sixth decade since they seem to be at high risk of vertebral fracture.
This study was supported by a project grant from the Arthritis and Rheumatism Council (R44); NFAP is supported by the council as a clinical research fellow. We thank Miss M Cooke and Ms D Greenfield for recruiting patients, and Mrs A Johnson, Mrs S Bowles, and Mr A Milne for measuring bone mineral densities.