CT, MRI Show Weaker Bones in Teens Post-Weight Loss Surgery

November 24, 2020
Whitney J. Palmer

Images reveal that adolescents experienced a loss in volumetric bone mineral density after sleeve gastrectomy and extreme weight loss.

A common weight-loss surgery in adolescents – sleeve gastrectomy – might induce weight loss, but, according to CT and MRI scans, it also weakens the patient’s bones.

In a sleeve gastrectomy procedure, 75 percent of the patient’s stomach is removed to control food intake, promoting weight loss. As a result, the stomach becomes tube- or sleeve-shaped, and from 2005 to 2014, the number of these procedures performed on adolescents has increased 100-fold, said a team from Harvard Medical School.

“Childhood obesity is a major public health issue that has increased over the last 10 years,” said lead investigator Miriam A. Bredella, M.D., radiology professor at Harvard and vice chair of the Massachusetts General Hospital radiology department. “Sleeve gastrectomy is the most common bariatric surgery procedure performed in children and adults.”

Bredella’s team will present their findings next week during the Radiological Society of North America (RSNA) annual meeting.

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It is known that bariatric surgery has long-term bone effects in adults that can lead to a higher risk of fracture. The team set out to determine if the same thing happens to teen-agers who have the surgery during their critical years of growth and development when they are accruing bone mass.

For their study, the team enrolled 52 adolescents who had moderate-to-severe obesity with an average body mass index (BMI) of 45. A BMI over 30 is considered obese. The average age was 17.5 years, and 38 of the participants were girls. Bredella’s team split the group in half – 26 participants underwent sleeve gastrectomy, and 26 did not.

To detect any changes, all participants had a quantitative CT to detect volumetric bone mineral density changes in the lumbar spine performed both before any surgery and 12 months later. The test is particularly accurate for this measurement, the team said. In addition, the team also performed proton MR spectroscopy on all participants to quantify the amount of bone marrow fat in the lumbar spine. Recent studies have shown that bone marrow fat can be a bone quality biomarker because it responds to nutritional changes.

Based on the results of these scans, the team determined that adolescents who had the surgery lost 34 kilograms/75 pounds, and the participants who did not have the procedure saw no significant weight loss. But, the teens who had the surgery also saw a significant increase in bone marrow fat with a corresponding decrease in bone density in the lumbar spine.

“Adolescents who underwent sleeve gastrectomy had bone loss and an increase in bone marrow fat, despite marked loss of body fat,” Bredella said. “While weight-loss surgery is successful for weight loss and improving metabolic disorders, it has negative effects on bone.”

This post-surgery change was not surprising, though, she said, because greater bone density comes with greater weight-bearing. And, alongside, those drops in bone density, the surgery also disrupted hormones and nutrients that are integral to bone health.

Knowing how this surgery affects young patients can be important to potentially safeguarding their bone quality as they age, Bredella said.

“We need to identify mechanisms that will help prevent bone loss in these patients and to make adolescents with obesity more aware of bone health,” she said. “Adolescence is the critical time for bone mass accrual, and any process that interferes with bone accrual during this time can have dire consequences later in life.”

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