Bone Metabolism in Adolescents Undergoing Bariatric Surgery

Abstract

Purpose: The prevalence of childhood obesity has increased over past decades with a concomitant increase in metabolic and bariatric surgery (MBS). While MBS in adults is associated with bone loss, only a few studies have examined the effect of MBS on the growing skeleton in adolescents.

Methods: This mini-review summarizes available data on the effects of the most commonly performed MBS (sleeve gastrectomy and gastric bypass) on bone in adolescents. A literature review was performed using PubMed for English-language articles.

Results: Dual-energy x-ray absorptiometry (DXA) measures of areal bone mineral density (aBMD) and BMD Z scores decreased following all MBS. Volumetric BMD (vBMD) by quantitative computed tomography (QCT) decreased at the lumbar spine while cortical vBMD of the distal radius and tibia increased over a year following sleeve gastrectomy (total vBMD did not change). Reductions in narrow neck and intertrochanteric cross-sectional area and cortical thickness were observed over this duration, and hip strength estimates were deleteriously impacted. Marrow adipose tissue (MAT) of the lumbar spine increased while MAT of the peripheral skeleton decreased a year following sleeve gastrectomy. The amount of weight loss and reductions in lean and fat mass correlated with bone loss at all sites, and with changes in bone microarchitecture at peripheral sites.

Conclusion: MBS in adolescents is associated with aBMD reductions, and increases in MAT of the axial skeleton, while sleeve gastrectomy is associated with an increase in cortical vBMD and decrease in MAT of the peripheral skeleton. No reductions have been reported in peripheral strength estimates.

Keywords: bone density; bone markers; bone strength; gastric bypass; sleeve gastrectomy; weight loss surgery.

Figure 1.

BMD QCT pre–post: QCT of L2 in a 17-year-old female prior to (A) and 12 months after sleeve gastrectomy (B). Volumetric BMD (vBMD) decreased following sleeve gastrectomy (vBMD presurgery 183 mg/cm³, vBMD postsurgery 146 mg/cm³). CT images are presented using the same window and level.

Figure 2.

Percent change in HRpQCT measures at the distal tibia (top) and distal radius (bottom) in the nonsurgical and sleeve gastrectomy groups (after controlling for age, sex, and race). *P < .05, **P < .10. Ct., cortical; Tb., trabecular; vBMD, volumetric bone mineral density. Reproduced with permission from Misra et al. Bone 2020.

Figure 3.

Percent change in hip structural analysis (HSA) measures at the narrow neck and intertrochanteric region in the surgical versus nonsurgical groups over 12 months. CSMI: cross-sectional moment of inertia; Ct, cortical; *P < .05; **P < .10 (both after controlling for age, sex, and race). Reproduced with permission from Misra et al. Surg Obes Rel Dis 2020.

Figure 4.

Marrow adipose tissue (MAT) of the lumbar spine pre- and postsleeve gastrectomy. ¹H-MRS of the lumbar spine in an 18-year-old female prior to (A) and 12 months after sleeve gastrectomy (B). Marrow adipose tissue (MAT) content in lipid to water ratio (LWR) of L1 increased following sleeve gastrectomy (MAT presurgery, 0.20 LWR; MAT postsurgery, 0.41 LWR). For purposes of visual comparison, the amplitudes of unsuppressed water are scaled identically.