Obesity and spinal loads; a combined MR imaging and subject-specific modeling investigation.

Epidemiological studies have identified obesity asa possible risk factor for low back disorders. Biomechanical models can help test such hypothesis and shed light on the mechanism involved. A novel subject-specific musculoskeletal-modelling approach is introduced to estimate spinal loads during static activities in five healthy obese (BMI>30kg/m2) and five normal-weight (200.05). Heavier subjects did not necessarily have larger muscle moment arms (e.g., they were larger in 64kg (BMI=20.7kg/m2) subject than 78kg (BMI=24.6kg/m2) subject) or greater T1-L5 trunk weight (e.g., the 97kg (BMI=31kg/m2) subject had similar trunk weight as 109kg (BMI=33.3kg/m2) subject). Obese individuals had in average greater spinal loads than normal-weight ones but heavier subjects did not necessarily have greater spinal loads (117kg (BMI=40.0kg/m2) subject had rather similar L5-S1 compression as 105kg (BMI=34.7kg/m2) subject). Predicted L4-L5 intradiscal pressures for the normal-weight subjects ranged close to the measured values (R2=0.85-0.92). Obese individuals did not necessarily have greater IDPs than normal-weight ones.