Opportunistic Quantitative Computed Tomography Assessing Bone Mineral Density in Patients With Laparoscopic Roux-En-Y-Gastric Bypass Metabolic Surgery Throughout a 5-Year Observation Window

Abstract

Background: Bariatric surgery is associated with decreasing bone mineral density (BMD).

Objective: To assess the long-term vertebral BMD, measured by opportunistic quantitative CT (QCT), and body mass index (BMI) in patients undergoing proximal laparoscopic Roux-en-Y surgery (LRYGB).

Methods: In 62 patients undergoing LRYGB, opportunistic QCT measurements were performed extracting BMD and BMI on day 1 and years 1, 3, and 5 postoperatively.Primarily, one-way analyses of variance were performed on dependent variables BMI and BMD, with imaging interval defined as an independent factor. Student-Newman-Keuls tests performed pairwise comparisons of imaging interval permutations for BMI/BMD.Secondarily, analyses of covariance were used on dependent variables BMI and BMD, with imaging interval as an independent factor and gender/age as well as BMD/BMI, respectively, as covariates.

Results: A total of 227 opportunistic QCT measurements in 62 patients were performed without the need of a phantom or extra software.The BMD decreased substantially and continuously during 1-, 3-, and 5-year follow-up observations, reaching statistical significance in pairwise comparisons for 3- and 5-year follow-up visits compared to initial BMD values as well as the 5-year follow-up visit compared to the 1-year BMD values, P < 0.001. Age and BMI were significant covariates, P < 0.001.The BMI decreased within 1 year and stayed constant until a slight increase at 5 years was observed. Statistical significance in pairwise comparisons for first-year and 3- and 5-year follow-up visits was reached compared to initial BMI values, P < 0.001. For the BMI assessment, none of the covariates reached statistical significance.

Conclusion: Opportunistic QCT is suited for the calculation and follow-up of BMD. There was a continuous decrease of BMD after LRYGB over 5 years post-surgery, whereas BMI decreased in the first year and stayed constant thereafter. Older patients with lower BMI seem particularly prone to an accelerated BMD loss.

Keywords: BMI; LRYGB; bone mineral density; opportunistic QCT.