Non-fusion instrumentation of the lumbar spine with a hinged pedicle screw rod system: an in vitro experiment
- 6 June 2009
- journal article
- research article
- Published by Springer Science and Business Media LLC in European Spine Journal
- Vol. 18 (10), 1478-1485
- https://doi.org/10.1007/s00586-009-1052-3
Abstract
In advanced stages of degenerative disease of the lumbar spine instrumented spondylodesis is still the golden standard treatment. However, in recent years dynamic stabilisation devices are being implanted to treat the segmental instability due to iatrogenic decompression or segmental degeneration. The purpose of the present study was to investigate the stabilising effect of a classical pedicle screw/rod combination, with a moveable hinge joint connection between the screw and rod allowing one degree of freedom (cosmicMIA). Six human lumbar spines (L2–5) were loaded in a spine tester with pure moments of ±7.5 Nm in lateral bending, flexion/extension and axial rotation. The range of motion (ROM) and the neutral zone were determined for the following states: (1) intact, (2) monosegmental dynamic instrumentation (L4-5), (3) bisegmental dynamic instrumentation (L3–5), (4) bisegmental decompression (L3–5), (5) bisegmental dynamic instrumentation (L3–5) and (6) bisegmental rigid instrumentation (L3–5). Compared to the intact, with monosegmental instrumentation (2) the ROM of the treated segment was reduced to 47, 40 and 77% in lateral bending, flexion/extension and axial rotation, respectively. Bisegmental dynamic instrumentation (3) further reduced the ROM in L4-5 compared to monosegmental instrumentation to 25% (lateral bending), 28% (flexion/extension) and 57% (axial rotation). Bisegmental surgical decompression (4) caused an increase in ROM in both segments (L3–4 and L4–5) to approximately 125% and approximately 135% and 187–234% in lateral bending, flexion/extension and axial rotation, respectively. Compared to the intact state, bisegmental dynamic instrumentation after surgical decompression reduced the ROM of the two-bridged segments to 29–35% in lateral bending and 33–38% in flexion/extension. In axial rotation, the ROM was in the range of the intact specimen (87–117%). A rigid instrumentation (6) further reduced the ROM of the two-bridged segments to 20–30, 23–27 and 50–68% in lateral bending, flexion/extension and axial rotation, respectively. The results of the present study showed that compared to the intact specimen the investigated hinged dynamic stabilisation device reduced the ROM after bisegmental decompression in lateral bending and flexion/extension. Following bisegmental decompression and the thereby caused large rotational instability the device is capable of restoring the motion in axial rotation back to values in the range of the intact motion segments.Keywords
This publication has 34 references indexed in Scilit:
- Higher Risk of Adjacent Segment Degeneration After Floating Fusions: Long-Term Outcome After Low Lumbar Spine FusionsJournal of Spinal Disorders & Techniques, 2008
- En bloc spondylectomy reconstructions in a biomechanical in-vitro studyEuropean Spine Journal, 2008
- Immediate Biomechanical Effects of Lumbar Posterior Dynamic Stabilization Above a Circumferential FusionSpine, 2007
- Dynesys fixation for lumbar spine degenerationNeurosurgical Review, 2007
- Test Protocols for Evaluation of Spinal ImplantsJournal of Bone and Joint Surgery, 2006
- The Use of an Interspinous Implant in Conjunction With a Graded Facetectomy ProcedureSpine, 2005
- ADJACENT SEGMENT DEGENERATION IN THE LUMBAR SPINEThe Journal of Bone and Joint Surgery-American Volume, 2004
- The Effect of Disc Degeneration and Facet Joint Osteoarthritis on the Segmental Flexibility of the Lumbar SpineSpine, 2000
- Load-Sharing Characteristics of Stabilized Lumbar Spine SegmentsSpine, 2000
- The Relevance of Torsion to the Mechanical Derangement of the Lumbar SpineSpine, 1981