Bone outcomes following sleeve gastrectomy in adolescents and young adults with obesity versus non-surgical controls

Background: Sleeve gastrectomy is the most commonly performed weight loss surgery in adolescents with moderate-to-severe obesity. While studies in adults have reported on the deleterious effects of gastric bypass surgery on bone structure and strength estimates, data are lacking for the impact of sleeve gastrectomy on these measures in adolescents. Objective: To evaluate the impact of sleeve gastrectomy on bone outcomes in adolescents and young adults over 12 months using dual energy X-ray absorptiometry (DXA) and high resolution peripheral quantitative computed tomography (HRpQCT). Participants and methods: We enrolled 44 youth 14-22 years old with moderate to severe obesity; 22 underwent sleeve gastrectomy and 22 were followed without surgery (16 females and 6 males in each group). At baseline and 12 months, DXA was used to assess areal bone mineral density (aBMD), HRpQCT of the distal radius and tibia was performed to assess bone geometry, microarchitecture and volumetric BMD (vBMD), and finite element analysis to assess strength estimates (stiffness and failure load). These analyses were adjusted for age, sex, race and the bone measure at baseline. Fasting blood samples were assessed for calcium, phosphorus, and 25(OH) vitamin D (250HD) levels. Results: Over 12-months, the surgical group lost 27.2% of body weight compared to 0.1% in the non-surgical (control) group. Groups did not differ for changes in 250HD levels (p = 0.186). Compared to controls, the surgical group had reductions in femoral neck and total hip aBMD Z-scores (p <= 0.0006). At the distal tibia, compared to controls, the surgical group had reductions in cortical area and thickness and trabecular number, and increases in trabecular area and separation (p <= 0.026). At the distal radius, the surgical group had greater reductions in trabecular vBMD, than controls (p = 0.010). The surgical group had an increase in cortical vBMD at both sites (p <= 0.040), possibly from a decrease in cortical porosity (p <= 0.024). Most, but not all, differences were attenuated after adjusting for 12-month change in BMI. Groups did not differ for changes in strength estimates over time, except that increases in tibial stiffness were lower in the surgical group (p = 0.044) after adjusting for 12-month change in BMI. Conclusions: Over 12 months, weight loss associated with sleeve gastrectomy in adolescents had negative effects on areal BMD and certain HRpQCT parameters. However, bone strength estimates remained stable, possibly because of a simultaneous decrease in cortical porosity and increase in cortical volumetric BMD. Additional research is necessary to determine the relative contribution(s) of weight loss and the metabolic effects of surgery on bone outcomes, and whether the observed effects on bone stabilize or progress over time.