Background/Purpose:   Bariatric surgery is the most effective treatment for severe obesity.^1,2 Increased bone resorption has been demonstrated after bariatric surgery.³ However, there have been limited and conflicting reports as to the prevalence of osteoporosis and occurrence of fractures after surgery.^3,4 Existing clinical practice guidelines for the perioperative nutritional, metabolic and nonsurgical support of the bariatric surgery patient recommend checking pre- and post-operative vitamin D and post-operative PTH among other tests. Furthermore, bone density measurements is recommended at 2 years post-surgery. ⁵ This study aimed to describe the incidence of significant bone loss and fractures in the post-bariatric surgery population in an urban medical center. In addition, it also aimed to assess whether our physicians were following current practice guidelines for the monitoring of bone health in bariatric patients.

Methods:   This retrospective observational study included chart review (SD, LM, AI) from electronic medical records. Patients who had undergone bariatric surgery at MetroHealth Medical Center since January 1, 1999 to December 31, 2015 were identified by ICD-9 code gastric bypass 43664 and 43665, sleeve gastrectomy 43775 and gastric banding 43770, and were included in the study. Data were collected using Research Electronic Data Capture (REDCap). The following data were reviewed: demographics; date and type of bariatric procedure; pre- and post-surgery vitamin D, parathyroid hormone (PTH), C-terminal telopeptide (CTX), N-terminal telopeptide (NTX) and bone alkaline phosphatase; bone density survey [Dual-energy X-ray absorptiometry (DXA)] dates & results; and fractures if any, including type (fragility or traumatic) and location. Descriptive analyses were performed and included measures of central tendency (mean and median) and variability (standard deviation, minimum and maximum). Wilcoxon signed rank test was used to assess statistical significance between certain distributions such as race and body mass index (BMI) or vitamin D levels.

Results:   Five hundred twenty-three patients were included in the study. There were 437 females and 86 males, with a mean age of 45.39; 48.76% were identified as White and 39.77% were identified as African-American (Table 1). The most common surgical procedure was gastric bypass 80.31%, followed by sleeve gastrectomy 16.63%, and gastric banding 3.06%. Average days of patient follow-up after bariatric surgery were 1162 days. Pre-surgical mean BMI was 48.98 kg/m², with African-Americans having a significantly greater BMI than Whites and Hispanics (p = 0.0009). Post-surgical weight loss median percent difference was 22.60% loss 6 months after surgery, 29.96% 12 months after surgery, and 26.12% at 3 or more years after surgery. Vitamin D was checked in 83.4% of patients before surgery, but was only checked in 41.87% of patients within 1 year after surgery. Vitamin D levels were within normal range (30.0 – 100.0 ng/mL) up to 1 year after surgery for patients who have had their levels checked. There was no significant difference in post-surgical vitamin D levels among races (p = 0.1770). PTH was checked in only 6.70% of patients 6 months after surgery, and in only 5.16% at 1 year post-surgery. CTX, NTX and bone alkaline phosphatase were rarely measured. Only 19 patients (3.63%) had DXA prior to surgery. Eleven patients (2.10%) had DXA within 2 years after surgery, and 16 patients (3.06%) had DXA more than 2 years after surgery. Four of the 19 patients who had DXA pre-surgery had repeat scans post-surgery (1 within 2 years, and 3 after 2 years), all showed significant bone mineral density (BMD) decrease (Table 2). Only 10 fractures were observed in the study; 3 were fragility and 7 were traumatic. Mean time to fracture for those who had a fragility fracture was 4.93 years. The location of the 3 fragility fractures were the wrist (n=1) and fibula (n=2). All of the 3 patients underwent gastric bypass procedure.

Conclusion:   There is considerable discrepancy between current physician practice at our urban medical center and recommended clinical practice guidelines for bone health monitoring in the bariatric population. Vitamin D, PTH and DXA were infrequently checked in our bariatric surgery patients. In the few patients who had pre- and post-operative bone density measurements, significant bone loss was observed. Despite this large survey of bariatric patients, there is a low incidence of fractures post-bariatric surgery over a follow up time of 3 years.