Longitudinal 5-Year Evaluation of Bone Density and Microarchitecture After Roux-en-Y Gastric Bypass Surgery

Abstract

Context: Bone health declines in the initial years after Roux-en-Y gastric bypass (RYGB), but long-term skeletal effects are unclear.

Objective: To document longitudinal changes in bone mineral density (BMD) and microarchitecture 5 years after RYGB.

Design, setting, and participants: Prospective 5-year observational study of 21 adults with severe obesity receiving RYGB at an academic medical center.

Main outcome measures: Spine and hip areal BMD were measured by dual-energy X-ray absorptiometry, and trabecular volumetric BMD (vBMD) of the spine was assessed by quantitative CT (QCT). We measured vBMD and microarchitecture of the distal radius and tibia by high-resolution peripheral QCT in a subset of subjects. Serum type I collagen C-terminal telopeptide (CTX) and procollagen type I N-terminal propeptide (P1NP) were also measured.

Results: Areal BMD declined by -7.8% ± 7.6% at the spine and -15.3% ± 6.3% at the total hip by 5 years after RYGB (P ≤ 0.001), although the rate of bone loss slowed in later years. Trabecular spine vBMD decreased by -12.1% ± 12.3% by 5 years (P ≤ 0.001). At peripheral sites, vBMD continued to decrease steadily throughout 5 years, with parallel declines in cortical and trabecular microarchitecture, leading to decreases in estimated failure load of -20% and -13% at the radius and tibia, respectively (P < 0.001). Five years after RYGB, CTX and P1NP were 150% and 34% above baseline (P < 0.001 and P = 0.017, respectively).

Conclusions: Sustained high-turnover bone loss and bone microarchitectural deterioration occur in the 5 years after RYGB. Adults receiving RYGB warrant assessment of bone health.

Figure 1.

Longitudinal changes in spine and hip BMD by DXA and QCT after RYGB. Mean ± SEM percentage change vs baseline over 5 y is shown for (A) PA spine aBMD, (B) trabecular spine vBMD, (C) total hip aBMD, and (D) femoral neck aBMD. *Dunnett-adjusted P < 0.05 for comparison vs baseline visit. ^#P < 0.05 for comparison vs 2-y visit.

Figure 2.

Cortical porosity at the distal radius and tibia at preoperative baseline and 5 y after RYGB. Cortical pores are denoted by gray shading.

Figure 3.

Longitudinal changes in serum CTX and P1NP after RYGB. Mean ± SEM percentage change over 5 y is shown for serum (A) CTX and (B) serum P1NP. *Dunnett-adjusted P < 0.05 for comparison vs baseline visit.

Figure 4.

Scatterplot of 5-y percentage changes in spine aBMD vs insulin after RYGB.