Article
Is an effective functional replacement of a lumbar Segment possible? Biokinemetrie as a surgical projection
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Published: | June 9, 2017 |
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Objective: Spine’s extent of movement is larger than the linear sum of the individual movements of the facet joints. Such small movements of the facet joints, which guide the whole segmental movement, are progressively added together via lever arms. Describing the segmental motion pattern we could show that each segment has the same motion characteristic but is provided at another point of this characteristic depending on the progress of the movement. In stabilizing operations whether rigid, dynamic or prosthetic, a fracture-like release of the segment is done. In case of fracture, unnatural movement patterns are possible, so bone is attached. Therefore, in order to create an effective functional lumbar replacement, the movement of the segment must be measured, then it must be simulated by adjusting it to the adjacent levels to finally restrict it to avoid fast ossification.
Methods: After the segmental movement was cinematographically characterized by fluoroscopy examination of healthy volunteers, the movement characteristics of every lumbar segment were simulated. The software targeted the worst segment of the considered spine region analyzing the movement recordings in inclination, neutral position and reclination from the plain X-rays. The software repeated the range of motion analysis by using the best segment simulated in the worst to define optimal height for segmental replacement regarding current degeneration. The segment was first improved regarding its optimized segmental height and then the extrapolated characteristics were transferred to this segment to define placement and bearing surface reflecting the movement pattern of an interspinous device that supports the facet joints.
Results: Construction of an artificial bearing area which is able to support the progressive movement of the facet joints. A device “lock-move” which results from this consideration is able to be implanted into the interspinous space using cortical bone trajectories. Such device was implanted in a 38-year-old male patient with a follow up time of four years, who had been operated 10 times on a prolapse in L5/S1, thereby damaging the facet joints. He refused stabilization. He was supplied with monoblock prosthesis and a poly-axial head based facet joint support, which allowed a restricted translation.
Conclusion: Measuring and consecutive simulation of movement patterns to provide mathematical - algorithmic theorems for the development of a surface reflecting the movement pattern of a lumbar segment to construct an interspinous device that supports the facet is possible. Pedicle screw based dynamic support (topping-offs), which does not allow the segmental height to increase and to decrease progressively during the movement can’t work according the results of this examination.