AAOS: Hip Fracture Risk High After Shoulder Fracture

By Crystal Phend
SAN FRANCISCO, March 10 -- Older women who've broken a shoulder are at a six-fold increased risk of hip fracture in the following year, a prospective cohort suggests.
After the first year, though, subsequent hip fracture risk fell substantially, reported Jeremiah Clinton, M.D., of the University of Washington in Seattle, and colleagues at the American Academy of Orthopaedic Surgeons meeting here.
"We have a definite period of time to intervene if we want to prevent the more serious hip fractures," Dr. Clinton said.
Hip fractures are an important target for prevention because they have the highest mortality rate (13% to 36%) of all the fragility fractures and cause loss of independence in about half of patients, he said.
Previous studies had suggested an increased risk of hip fracture after a shoulder fracture but had limited follow-up, failed to control for risk factors, or covered only individual geographic areas whereas fracture incidence is known to vary geographically.
So the researchers analyzed data from the Study of Osteoporotic Fractures, a prospective observational cohort study of 9,704 women older than 65 living in Baltimore, Pittsburgh, Minneapolis, and Portland.
Participants were examined seven times over 10 years of follow-up with phone interviews or postcards every four months.
During this period, 321 women sustained a radiographically-confirmed fracture of the proximal humerus and 783 had a confirmed hip fracture (3.7 and 9.0 per 1,000 patient-years, respectively).
Among them, 44 patients had both a proximal humerus fracture and a hip fracture.
Prior proximal humerus fracture was second only to total hip bone mineral density as a predictor of hip fracture (HR 1.83 and 2.11, respectively, both P<0.001).
Shoulder fracture remained a significant independent risk factor for hip fracture on multivariate analysis (HR 1.57, 95% CI 1.12 to 2.19, P=0.009).
Timing appeared to be key: risk decreased with longer follow-up after the initial shoulder fracture.
Compared with the likelihood of hip fracture before the shoulder fracture, the age- and bone mineral density-adjusted hazard ratios were:
6.16 in the first year after the proximal humerus fracture (95% CI 4.01 to 9.44).
1.16 from two to four years after the shoulder fracture (95% CI 0.67 to 2.02).
0.64 beyond four years after the proximal humerus fracture (95% CI 0.24 to 1.71).
The reason for the elevated risk after shoulder fracture is unknown, Dr. Clinton said. However, "these fractures typically occur from the same fall pattern," he noted.
Other explanations could be related to medication use or to the initial fracture itself, such as if it impairs patients' balance, he said.
The researchers noted that the study was limited by the examination of few variables, a fairly homogeneous sample of older Caucasian women, and the small number of women who had both shoulder and hip fractures.
Nevertheless, Dr. Clinton said, physicians should be vigilant about counseling patients on fall prevention after a first fracture and consider bisphosphonate therapy, which has been shown in other studies to reduce risk of a second fracture.
The study was supported by the National Institutes of Health, the National Institute of Arthritis and Musculoskeletal and Skin Diseases, and the National Institute on Aging.
Dr. Clinton reported no conflicts of interest.
Primary source: American Academy of Orthopaedic Surgeons meetingSource reference:Clinton J, et al "Humerus fractures as predictors of future hip fracture: Timing is everything" AAOS meeting 2008; Abstract 332.