Belly Fat Forces on the Spine: Finite Element Analysis of Belly Fat Forces by Waist Circumference.

OBJECT: It has been well-established that obesity, or the fat content of the belly, is associated with diabetes, heart conditions, metabolic syndrome and back pain. With regard to back pain, this study aimed to assess the forces that incremental amounts of belly fat exert on the spine. METHODS: A finite element analysis (FEA) was performed with a 3D CAD model of the spine using data for various populations from the Dallas Heart Study. RESULTS: There were significant differences in the forces exerted on the spine by belly fat among ethnic groups. CONCLUSIONS: These findings should help clarify the stress forces experienced by the spine in relation to waist circumference and could help to explain the association between obesity and back pain.

Backpack Forces on the Spine.

OBJECT: Backpacks are standard load carriers for people of all ages, especially school children and the military. Previous studies have described the impact of the forces exerted by backpacks on load distribution, back pain, and gait. The objective of this study was to use finite element analysis (FEA) to assess the effects of incremental weights in a backpack on the spine. METHODS: To assess the forces experienced by the spine under the incremental addition of weight to a backpack, we performed a finite element simulation using commercially available 'BodyParts3D/Anatomography' data, which were imported into FEA software. We studied two different scenarios: 1) a regular backpack with incrementally placed weights using both shoulder straps with the spine in a neutral position, and 2) a regular backpack with incrementally placed weights using both shoulder straps with the spine tilted forward 20 degrees. The spine model was physiologically accurate. RESULTS: For all of the added weights examined (1-100 pounds; 0.45-45.36 kg), the force experienced by the neutral spine was 7.2-fold the added weight. For the 20 degrees-forward posture, this value rose to 11.6-fold. CONCLUSIONS: These findings should help to clarify the forces experienced by the spine due to objects in a backpack. For example, this should help spinal surgeons to better understand the tremendous importance of sagittal plane alignment in planning their surgical reconstructions.