Is an ankle fracture a clinical sign of osteoporosis?

A few years ago I was given access to a medical claims database that included 250,000 women aged 50 years and older. I tracked claims for fracture over a three-year period and the traditional osteoporosis-related fractures — wrist, vertebra, hip — were reported with increasing frequency with increasing age. The wrist fracture increase was reported in the first 10 years post-menopause. Spine fractures began to increase some five to 10 years later while the hip fracture increase was not noted until after age 70 years.

Surprisingly, the most common fracture was “foot and ankle,” but equally surprisingly, the incidence did not track with age. Most authorities in the field of osteoporosis do not accept these fractures as being related to osteoporosis and there is a “confirming” publication from a large Australian study pointing out that ankle fractures were not predictive of future fragility fractures in women. Just to cloud the issue further, these fractures were important predictors of future fracture in men.

So how should I have handled the 70-year-old woman who limped into my clinic the other day having sustained her third ankle fracture following a simple twisting accident? “I have floppy ankle joints and so does my son but he hasn’t fractured yet,” she reported.

This woman deserves a DEXA study as do all women aged 65 years and older, according to the United States Preventive Services Task Force. While I am waiting for the result of the DEXA, I turned to FRAX, the new World Health Organization tool for calculating future fracture risk that I have written about before. That instrument asks about previous fracture as a Yes/No question without regard to the circumstance of the fracture or the site of fracture.

With a T-score of –1.0 and “no” fracture, this patient’s 10-year probability of a future major osteoporosis fracture was 14%. If I checked the box that said “yes” for fracture, the risk increased 23%. For a T-score of –2.5 the risk without previous fracture was 22%, rising to 34% if I checked the “yes” box for previous fracture.

Still confused about the ankle fracture being osteoporosis? Do not get hung up on the diagnostic label, focus instead on management. If the DEXA T-score does not suggest to you that the patient needs pharmacologic therapy, please turn to the FRAX website before making your final decision.