title: Effect of centers of rotation on spinal loads and muscle forces in total disk replacement of lumbar spine.
abstract: The placement of artificial disks can alter the center of rotation and kinematic pattern; therefore, forces in the spine during the motion will be affected as a result. The relationship between the location of joint center of artificial disks and forces in the spinal components is not investigated. A musculoskeletal model of the spine was developed, and three location cases of center of rotation were investigated varying 5 mm anteriorly and posteriorly from the default center. Resultant joint forces, ligament forces, facet forces, and muscle forces for each case were predicted during sagittal motion. No considerable difference was observed for joint force (maximum 14%). Anterior shift of center of rotation induced the most ligament forces (200 N) and facet forces (130 N) among the three cases. Posterior and anterior shifts of centers of rotation from the default location caused considerable changes in muscle forces, respectively: 108% and 70% of increase in multifidi muscle and 157% and 187% of increase in short segmental muscle. This study showed that the centers of rotation due to the design and the surgical placement of artificial disk can affect the kinetic results in the spine.
authors: Department of Mechanical Engineering, College of Engineering, Kyung Hee University, Yongin-si, Republic of Korea.
authors: Kap-Soo
authors: KS
authors: Han
authors: Kyungsoo
authors: K
authors: Kim
authors: Won Man
authors: WM
authors: Park
authors: Dae Seop
authors: DS
authors: Lim
authors: Yoon Hyuk
authors: YH
authors: Kim
mesh_terms: D064131:Back Muscles / Q000503:physiopathology*; D003198:Computer Simulation; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000503:physiopathology* / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000503:physiopathology* / Q000601:surgery*; D008954:Models, Biological; D012399:Rotation; D013314:Stress, Mechanical; D059145:Total Disc Replacement / Q000295:instrumentation* / Q000379:methods; D016474:Weight-Bearing
keywords: Center of rotation; facet force; ligament force; muscle force; spine biomechanics; spine load