ENDO 2009: Bariatric Surgery Linked to Increased Fracture Risk

People who have undergone bariatric surgery have a 2-fold chance of experiencing broken bones, especially in their hands and feet, compared with the general population. These findings were presented here at ENDO 2009: The Endocrine Society Annual Meeting.

Researchers were interested in determining the impact of bariatric surgery on bone health, and used bone resorption markers (such as pyridinoline crosslinks, deoxypyridinoline crosslinks, and urinary N-telopeptide crosslinks) and bone formation markers (osteocalcin) to assess whether there is an increase in fracture risk after bariatric surgery. The study examined the fracture incidence in subjects who had undergone bariatric surgery, and compared it with expected rates in the general population.

Elizabeth Chittilapilly Haglind, MBBS, MD, presented the preliminary results on behalf of a research team from the Departments of Endocrinology, Health Sciences Research, and Rheumatology at the Mayo Clinic in Rochester, Minnesota.

Challenging the Standard of Care

"There are 15 million Americans with class 3 obesity," Dr. Haglind noted during her presentation, "and bariatric surgery [for this patient population] has become the standard of care, despite the fact that long-term complications are not completely understood."

"We knew there was a dramatic and extensive bone turnover and loss of bone density after bariatric surgery," Jackie Clowes, MD, PhD, senior author of the study, said in a news release. "But we didn't know what that meant in terms of fractures."

Using records from the Rochester Epidemiology Project, Dr. Haglind and colleagues reviewed data from 142 subjects selected randomly from the 292 subjects who underwent bariatric surgery from 1985 to 2004 at the Mayo Clinic. To determine the fracture incidence for these subjects, the researchers looked at the type of bariatric surgery, anthropomorphic indices over time, lifestyle, and nutritional status. They also obtained radiologic evidence for fractures and details such as date of fracture, site, and mechanism of injury.

The 142 subjects (mean age, 45 ± 10 years) had a mean body mass index of 48.6 ± 7.7 kg/m² and were followed up to 6 years. Gastric bypass surgery was performed in 90% of subjects; the rest had either vertical banded gastroplasty or biliopancreatic diversion. After bariatric surgery, 36 subjects experienced 53 fractures. "However, 55 subjects (39%) had prior history of fracture," noted Dr. Haglind.

Fractures were reported in the hip, spine, and humerus, but the majority of fractures were in the hands and feet.

The researchers used standardized incidence ratios to compare observed site-specific fractures to the number expected in this cohort during their follow-up. For all sites, the standardized incidence ratio for the first fracture was 2.0 and for fracture of the hand and foot, respectively, was 3.2 and 3.0.

Long-Term Effects on Bone Health

"By 6 years, there was a 2-fold increase in the incidence of fractures in the bariatric-surgery population [compared with the general population]," said Dr. Haglind.

However, "the increase in the fracture incidence is not an early phenomenon, but rather a late one," noted Dr. Haglind; the differences were not significant in the early months of follow-up.

"Could increased levels of activity for these patients be responsible for the unusually high numbers of postbariatric surgery fractures?" wondered John P. Bilezikian, MD, professor of medicine and pharmacology; chief, Division of Endocrinology; and director, Metabolic Bone Disease Program, Department of Medicine at Columbia University in New York City, who attended the talk.

This retrospective study has its limitations; it neither evaluated the risk factors nor explained possible mechanisms to account for the difference in the incidence of fractures after bariatric surgery, acknowledged Dr. Haglind. Her team is currently working to identify potential risk factors and to compare the fracture incidence in bariatric-surgery subjects with age-, sex-, and weight-matched controls. "More research is needed to confirm our findings and understand the specific risk factors and mechanisms involved," she said.

"This is a notable first-of-its-kind study with potential to influence current medical practice," Elizabeth A. Streeten, MD, associate professor of medicine, Division of Endocrinology, Diabetes and Nutrition at the University of Maryland School of Medicine in Baltimore, who chaired the session, told Medscape Diabetes & Endocrinology in an interview.

However, "we need to wait and see the results of the final study, with a larger number of patients and including vitamin D levels and their correlation with the incidence of fractures," she cautioned.