BACKGROUND: Severe @entity1635 deformities are usually treated by surgical instrumentation. Systems utilizing monoaxial pedicle screws with a tulip top design require rods to be fully seated and locked into the slot of each implant. The result is a limitation to the vertebra-positioning capability and the correction force control. Direct @entity1347 (DIST) was developed as a refinement of translational correction philosophies to provide better force control and vertebra-positioning capability. The objective of this study is to develop a biomechanical model for the spine instrumentation with the DIST system in order to simulate, analyze and compare different deformity correction strategies. METHODS: The @entity1 -specific spine geometry was reconstructed using calibrated coronal and sagittal radiographs. The spine biomechanical properties were adapted from experimental data and further adjusted using the @entity1 's side-bending radiographs. Instrumentation constructs were modeled as rigid bodies connected by kinematic joints. The instrumentation maneuvers of 6 cases were simulated for which the simulation parameters were extracted from the surgery documentation and video. The correction maneuvers and resulting effects were analyzed. FINDINGS: The simulations agreed well with the real surgery (differences on Cobb angles <5  ). The vertebral position relative to the rod was determined by 5 independent variables (position and orientation) vs. 2 for a monoaxial screw, thus increasing the possible correction of the connected vertebrae. The DIST system allows the @entity85 to be reduced by either gradually pulling the spine towards the rod through helical connections or translating it by pivoting the posts. Load at the vertebra-implant connection did not exceed 338N, and was well distributed (standard deviation<110N). INTERPRETATION: The study shows that the DIST system allows good control of the scoliotic vertebrae with good load sharing among implants.

Biomechanical modeling and analysis of a direct @entity1347 for the instrumentation of XXXX .

@entity1 :: ('9606', 'Species') :: ['patient'] @entity1347 :: ('MESH:C537775', 'Disease') :: ['incremental segmental translation'] @entity85 :: ('MESH:D009140', 'Disease') :: ['spine deformity'] @entity1635 :: ('MESH:D012600', 'Disease') :: ['scoliosis']
@entity85 :: (MESH:D009140,Disease) :: ['scoliotic deformities']
