Bariatric surgery associated with increased fracture risk

Bariatric surgery patients are more likely to have increased fracture risks both before and after the surgical procedure, compared to obese and non-obese people who don’t need surgery, according to a large study published by The BMJ. Obesity may not be as protective for fracture as originally thought, claim the authors, and they suggest that fracture risk assessment and management should be part of weight loss care.

The study, ‘Change in fracture risk and fracture pattern after bariatric surgery: nested case-control study’, carried out by researchers in Canada, examined the incidence and sites of fracture in severely obese patients who had undergone bariatric surgery, and compared them to obese and non-obese controls matched for sex and age.

Data was analysed from the Quebec Integrated Chronic Diseases Surveillance System (QICDSS) on 12,676 patients, and 38,028 obese and 126,760 non-obese people in the control groups between 2001-2014.

Outcomes

Prior to surgery, patients undergoing bariatric surgery (9,169; 72.3% women; mean age 42 (SD 11) years) were more likely to fracture (1,326; 10.5%) than were obese (3,065; 8.1%) or non-obese (8,329; 6.6%) controls.

In addition, a mean of 4.4 years after surgery, bariatric patients were more susceptible to fracture (514; 4.1%) than were obese (1,013; 2.7%) and non-obese (3,008; 2.4%) controls. Post-operative adjusted fracture risk was higher in the bariatric group than in the obese (relative risk 1.38, 95% confidence interval 1.23 to 1.55) and non-obese (1.44, 1.29 to 1.59) groups.

Before surgery, the risk of distal lower limb fracture was higher, upper limb fracture risk was lower, and risk of clinical spine, hip, femur, or pelvic fractures was similar in the bariatric and obese groups, compared with the non-obese group. After surgery, risk of distal lower limb fracture decreased (relative risk 0.66, 0.56 to 0.78), whereas risk of upper limb (1.64, 1.40 to 1.93), clinical spine (1.78, 1.08 to 2.93), pelvic, hip, or femur (2.52, 1.78 to 3.59) fractures increased.

The researchers looked at the fracture risk for the following procedures; adjustable gastric banding (n=3,887), sleeve gastrectomy (n=2,554), roux-en-Y gastric bypass (n=873) and biliopancreatic diversion (n=1,986). They found a significant increased risk of fracture only for biliopancreatic diversion, as the fracture risk associated with sleeve gastrectomy and roux-en-y gastric bypass was inconclusive owing to the small number of cases for Roux-en-Y gastric bypass (n=873) and the short follow-up for sleeve gastrectomy (median follow-up of 1.3 years).

Figure 1: Non-adjusted fracture-free survival rate (all fractures) by group and by type of bariatric procedure (for period between 2006 and 2014). Although fracture-free survival rate appears similar in adjustable gastric banding group to non-obese and obese groups, it is decreasing more rapidly in biliopancreatic diversion and Roux-en-Y gastric bypass groups. Follow-up time for sleeve gastrectomy is too short to draw conclusions (Credit: BMJ 2016;354:i3794)

These increased fracture risks remained high even after adjusting for fracture history, number of comorbidities, material and social deprivation, and area of residence.

The authors emphasised that guidelines should be followed on patient adherence to dietary supplements and physical activity, and patients should be referred to bone specialists if fracture risk is considered high. They added that the benefits and risks of surgery should be considered on an individual basis to propose the type of surgical procedure best suited to the patient as the efficacy of bariatric surgeries differs in terms of resolution of chronic conditions.

They also speculated that the increased fracture risks are due to falls and obesity related conditions, such as type 2 diabetes, as well as anatomical changes, and nutritional deficiencies induced by bariatric surgery.

“In conclusion, severely obese patients undergoing bariatric surgery are more susceptible to fracture than are obese and non-obese people, and this risk remains higher after surgery, they note. “Moreover, fracture risk is site specific in this group before and after surgery…it is important to weigh the benefits and risks of surgery for a given patient in order to propose the type of surgery that is best suited to the patient, as the efficacy of bariatric surgeries differs in terms of resolution of comorbidities associated with obesity. More studies that aim at understanding the mechanisms underlying the increased risk of fracture and at evaluating the efficacy of preventive and therapeutic strategies to reduce the effect of bariatric surgery on bone are needed given the paucity of evidence based guidelines in this area.”

In a linked editorial, ‘Bariatric surgery and fractures’, from Marco Bueter, a bariatric surgeon at the University of Zurich, Switzerland, writes “The study by Rousseau and colleagues explores valid questions and represents an important contribution to the evidence supporting the long term management of patients after bariatric surgery…On the basis of the data presented by Rousseau and colleagues, as a bariatric surgeon I will certainly consider including assessment of fracture risk in the interdisciplinary algorithm of post-bariatric care for all my patients in the future.