Prospective Study on the Consequences of Weight Loss After Bariatric Surgery on Obese Patients' Spine.

Obesity and back pain are massive public health problems, and the relationship between the two has not been described and studied. However, the investigators have also observed that many ex-obese patients still suffer from back and leg pain after an important weight loss.

The aim of this study is to measure the effect of weight loss on back pain, and to find out what parameters can explain such modifications (increasing or decreasing back pain).

The investigators will study clinical parameters, as well as radiological (to measure the effect of weight loss on spine sagittal alignment) and MRI (to measure lipomatosis, which is a fat epidural accumulation, responsible for nerve compression and therefore back and leg pain).

Inclusion criteria

• Age > 18 years old
• BMI > 40 or BMI > 35 with comorbidities due to obesity ( criteria for bariatric surgery)
• Follow up in Pompidou's Hospital Nutrition service
• Bariatric surgery intervention ( Sleeve gastrectomy or By pass)
• Follow up possible for one year or more
• Being covered by French social insurance
• Consent to participate in the study

Exclusion criteria

• History of spine surgery
• Bariatric surgery postoperative complication
• Non mastering of french language
• MRI contraindication
• Patient under legal protection ( e.g. guardianship)