Do obese and extremely obese patients lose weight after lumbar spine fusions? Analysis of a cohort of 7303 patients from the kaiser national spine registry

Study Design. A retrospective cohort study from the Kaiser Permanente Spine Registry. 

Objective. The aim of this study was to determine whether obese and extremely obese patients with lumbar spine fusions lost a clinically significant amount of weight (5%) 1 year after their surgery. 

Summary of Background Data. Obesity in the United States has a prevalence of 35% and is a global health issue. Obesity is associated with lumbar spine disease. There is limited evidence regarding postsurgical weight loss after spine surgery. 

Methods. Adult patients in the Kaiser Permanente Spine Registry with lumbar fusions performed between 2009 and 2013 were included in the study sample (n ¼ 7303). The outcome of interest was 5% weight change 1 year postoperative from baseline. Three body mass index (BMI) groups were analyzed (BMI < 30; 30–39 obese; 40 extremely obese). Covariate analysis, multivariable logistic regression, odds ratios (ORs), and 95% confidence intervals (95% CIs) are provided. 

Results. At the time of spine surgery, 4456 (61%) had a BMI< 30, 2519 (34.5%) had a BMI between 30 and 39, 232 (3.2%) had a BMI 40, and 96 (1.3%) were missing their intraoperative BMI. We observed the following weight loss pattern: BMI< 30, 11.1%; BMI 30 to 39, 16.6%; BMI 40, 21.1%. We observed the following weight gain pattern: BMI< 30, 15.6%; BMI 30 to 39, 12.7%; BMI 40, 9.5%. After risk-adjustment, obese and extremely obese patients were more likely to lose a clinically significant amount of weight 1 year after surgery (BMI 30–39: OR¼ 1.42, 95% CI 1.22– 1.65; BMI 40: OR¼ 1.73, 95% CI 1.21–2.47) compared with nonobese patients. 

Conclusion. In this large cohort of patients with lumbar spinal fusions, we observed more significant weight loss in obese and extremely obese patients than nonobese patients. Additional research is needed to determine whether this weight loss is due to improvements in back pain and increased physical activity. Key words: bariatric, BMI, body mass index, degenerative lumbar disease, extreme obesity, lumbar fusion, lumbar spinal stenosis, metabolic syndrome, morbid obesity, obesity, weight loss. 

Level of Evidence: 3