Bone strength is preserved following bariatric surgery

There is an increasing concern that bariatric surgery results in excessive bone loss as demonstrated by studies that use areal bone mineral density (aBMD) outcomes by dual energy X-ray absorptiometry (DXA). Thus, we explored the effect of bariatric surgery on bone mechanical strength.

Bone strength and body composition outcomes were measured in 21 adults (age 45.3 years; BMI 45.7 kg/m(2)) at baseline (pre-surgery) and 3, 6, and 12 months post-surgery. Bone geometry, density and strength were assessed by peripheral quantitative computed tomography (pQCT) at the distal (4 %) sites of the radius and tibia and at the midshaft sites of the tibia (66 %) and radius (50 %). Participants were divided into tertiles (high, medium, and low) of percentage weight loss at 6 months post-surgery.

Participants in all three tertiles lost significant body weight by 6 months post-surgery (mean loss -5 to -30 %, all p < 0.05). At 6 months, all tertiles lost significant fat mass (-9 to -51 %, all p < 0.05), but only the high tertile lost significant fat-free mass (-8 %, p < 0.05). Despite a slight increase in tibia bone strength (SSIp) at 3 months (+1.1 %, p < 0.05), estimates of bone strength at the radius and tibia sites did not change at later post-surgical time points regardless of weight loss.

Contrary to DXA-based aBMD outcomes in the current literature, these results suggest that bone strength was preserved up to 12 months following bariatric surgery. Future longer-term studies exploring bone strength and geometry are needed to confirm these findings.