Abstract
Background
For dorsal stabilization, rigid implant systems are be coming increasingly complemented by numerous dynamic systems based on pedicle screws. Numerous posterior non-fusion systems have been developed within the past decade to resolve the disadvantages of rigid instrumentations and preserve spinal motion. For dorsal stabilization, rigid implant systems are becoming increasingly complemented by numerous dynamic systems based on pedicle screws and varying direction. However, it is still unclear which direction is most suitable to accomplish a physiologically related dynamic stabilization, and which loadings conditions are induced to the implants.
Purpose
The aim of this study was to investigate the effect of a new telescopic dynamic stabilization device. Evaluation of the effects on the dynamic stabilization of the spine in terms of segmental range of motion (RoM), and implant loadings.
Methods
Six sheep lumbar spine motion segments (L3–4) were loaded in a spine tester with pure moments of 7.5 Nm in flexion/extension lateral bending right/left. Specimens were tested in groups of intact (1), facetectomy with rigid fixation (2), facetectomy with the new telescopic mobil stabilization device (3). The kinematic response was recorded using an opto electric tracking system and reported in terms of intervertebral range of motion (ROM) and spinal stability.
Results
Mobile rod's kinematical behavior is more closer to intact group than rigid fixation. Flexion: 3.6 mm, 3.93 mm and 1.81 mm; extension 3.79 mm, 3.84 mm and 2.27 mm; lateral bending right 3.64 mm, 4.39 mm and 2.47 mm; lateral bendig left 4.6 mm and 5.79 mm and 2.58 mm, respectively.
Conclusion
Those involved in the design and evaluation of telescopic mobil rod devices may benefit from evaluation of inter pedicular kinematics. Evaluating inter vertebral motion from the perspective of the pedicle screw allows for a direct and intuitive translation between in vitro test results and design parameters. Furthermore, telescopic mobile rod knematics were similar to intact spine.
