title: Intra-operative spinal load and displacement monitoring: towards a better understanding of scoliosis correction mechanics.
abstract: Surgical correction of scoliosis reduces deformation and improves overall function and esthetics. Understanding and monitoring of mechanics during scoliosis surgery is an invaluable tool to optimize correction without compromising patient safety. Our objective was to use intra-operative monitoring tools to study how spinal load and displacement relates to obtained correction and chosen instrumentation. Instrumented pedicle screws, a "gripper" and active markers were developed. Instrumented pedicle screws provided three-dimensional forces at the screw-vertebra interface while the instrumented "gripper" measured the force and the rotation applied by the surgeon to the rod rotator. Vertebral displacement was monitored with light-emitting diodes and motion capture technology. These instruments were used successfully with 16 scoliosis subjects. Analysis of applied force, displacement, and curve flexibility influence on correction percentage is the long term goal. Raw results for instrumented screws and gripper showed that recorded force decreased with respect to percentage of correction obtained. Measured force increased with respect to the pre-surgical Cobb angle while percentage of correction obtained decreased as pre-surgical Cobb angle increased. Active marker results showed three-dimensional vertebral rotation and translation during correction, with axial rotation and caudal-cranial translation having the greatest magnitudes. Using greater correction forces does not necessarily result in an increased correction; flexibility and Cobb angle also play a role in the mechanics of correction. Further data collection will provide better understanding of the interconnected role between these factors helping complete the description of surgery mechanics.
authors.affiliation: Capital Health - Glenrose Rehabilitation Hospital Site, 10230 111 Ave., Edmonton, AB, Canada, T5G 0B7.
authors.forename: J
authors.initials: J
authors.lastname: Mondoux
authors.forename: E
authors.initials: E
authors.lastname: Lou
authors.forename: V J
authors.initials: VJ
authors.lastname: Raso
authors.forename: D
authors.initials: D
authors.lastname: Hill
authors.forename: J
authors.initials: J
authors.lastname: Mahood
authors.forename: M
authors.initials: M
authors.lastname: Moreau
mesh_terms: D001696:Biomechanical Phenomena; D006801:Humans; D007430:Intraoperative Care / Q000295:instrumentation*; D012600:Scoliosis / Q000601:surgery*; D016474:Weight-Bearing