Abstract
Objective The purpose of this study was to evaluate the durability and biological response of a new Posterior Dynamic Stabilization system using polyethylene with vitamin E on the sliding surface. Summary of Background Data The use of polyethylene with vitamin E on the sliding surface in Posterior Dynamic Stabilization has not been reported previously. Methods A developed pedicle screw-based Posterior Dynamic system consists of four parts: a set screw, a rod, a ball, and a pedicle screw. The rod is inserted into the through hole of the ball, and the ball is sandwiched by the set screw. (1) Fatigue Wear Test. Testing was conducted under a dynamic compressive load of 50N at a speed of 1 Hz for 1 million cycles. We examined the loss of polyethylene due to abrasion in 3 units. (2) Biological Response in Pigs. In two pigs, a new pedicle screw and a conventional pedicle screw were inserted in L2 and L3/4, and L4 and L2/3, respectively. After breeding for 6 months, autopsies were performed. CT imaging was used to evaluate bone union of the facet joint. Abrasive specimens were prepared, and abrasion powder and inflammatory cell infiltration were evaluated microscopically. Results The average loss of polyethylene due to abrasion was -0.01 mg. In all units, polyethylene showed a decrease of 0.1 mm or less at the contact point with the set screw. The facet joints between the conventional screws exhibited bone fusion, but the facet joint between the conventional and the new screw retained mobility with no bony fusion. No abrasion powder was found and inflammatory cell infiltration was only minimally observed. Conclusion The new Posterior Dynamic Stabilization system exhibited a high level of durability and biological safety.
Highlights
At present, spinal fusion is widely performed
New Posterior Dynamic Stabilization system: a major feature of this new pedicle screw system is that the relationship between the vertebral body and the rod is not completely fixed but semi-fixed
No obvious damage was observed on the sliding surface of the pedicle screw, the rod, and the set screw
Summary
The purpose of this study was to evaluate the durability and biological response of a new Posterior Dynamic Stabilization system using polyethylene with vitamin E on the sliding surface. The use of polyethylene with vitamin E on the sliding surface in Posterior Dynamic Stabilization has not been reported previously. A developed pedicle screwbased Posterior Dynamic system consists of four parts: a set screw, a rod, a ball, and a pedicle screw. We examined the loss of polyethylene due to abrasion in 3 units. A new pedicle screw and a conventional pedicle screw were inserted in L2 and L3/4, and L4 and L2/3, respectively. No abrasion powder was found and inflammatory cell infiltration was only minimally observed. The new Posterior Dynamic Stabilization system exhibited a high level of durability and biological safety
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