Bariatric Surgery in Teenagers May Lead to Weaker Bones

A new study claims that Roux-en-Y gastric bypass surgery in adolescents leads to loss of bone minerals, which could compromise future bone health.

Researchers at the Cincinnati Children's Hospital Medical Center (OH, USA) conducted a retrospective case review of 61 adolescents following bariatric surgery. Whole-body bone mineral content (BMC) and density (BMD) were measured by dual-energy radiograph absorptiometry, and age- and gender-specific BMD z scores were calculated; the measurements were obtained when possible before surgery, and then every three months after surgery for up to two years. Data were analyzed by using a mixed-models approach, and regression models were adjusted for age, gender, and height.

The results showed that whole-body BMC, BMD z score, and weight decreased significantly over time after surgery. In the first two years after surgery, predicted values based on regression modeling for BMC decreased by 7.4%, and BMD z score decreased from 1.5 to 0.1. During the first 12 months after surgery, change in weight was correlated with change in BMC; weight loss accounted for 14% of the decrease in BMC in the first year after surgery. The study was published in the April 2011 issue of Pediatrics.

"Although bone mineral values declined significantly after surgery, at two years post surgery they were not below the expected values for sex and age. But if the bone loss continues, even at a slow rate, these patients may have an increased risk of fractures later in life,” concluded lead author Anne-Marie Kaulfers, MD, and colleagues of the division of endocrinology. "And with a three-fold increase in patients under age 20 who had bariatric surgery between 2000 and 2003, bone loss has the potential to have long-term implications for many patients.”

BMD is used in clinical medicine as an indirect indicator of osteoporosis and fracture risk. It represents not a true physical density--which would be measured in mass per cubic volume--but rather a measurement value of a procedure called densitometry, which involves minimal radiation exposure; measurements are most commonly made over the lumbar spine and over the upper part of the hip. The average density of human bone is around 1,500 kg/m³; the Z-score is the number of standard deviations a patient's BMD differs from the average BMD of their age, sex, and ethnicity. The value is used in premenopausal women, men under the age of 50, and in children.

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Cincinnati Children's Hospital Medical Center