Related Experiment Video
Updated: Jul 4, 2026
09:07
An Anesthesia, Surgery, and Harvest Method for the Evaluation of Transpedicular Screws Using an In Vivo Porcine Lumbar Spine Model
Published on: May 31, 2017
Intradiscal pressure changes with dynamic pedicle screw systems.
Roshan Dath1, Daniel M Sirkett, Sabina Gheduzzi
1Department of Mechanical Engineering, Centre for Orthopaedic Biomechanics, University of Bath, UK. roshandath@hotmail.com
Journal of Spinal Disorders & Techniques
|June 6, 2008
Summary
Dynamic pedicle screw systems may reduce intradiscal pressure (IDP) during spinal fusion. This study found mobile screws resulted in lower IDP increases compared to rigid screws, potentially preventing secondary disc degeneration.
Area of Science:
- Spinal surgery
- Biomechanics
- Orthopedics
Background:
- Intervertebral discs are susceptible to injury from altered intradiscal pressure (IDP).
- The impact of dynamic pedicle screw systems on IDP requires further clarification.
Purpose of the Study:
- To evaluate changes in intradiscal pressure (IDP) using dynamic versus rigid pedicle screw systems in a simulated spinal fusion model.
Main Methods:
- An in vitro study utilized porcine spinal segments (n=16) with posterior instrumentation.
- Dynamic and rigid pedicle screw constructs were compared to uninstrumented controls (n=6).
- Spinal segments underwent 24,000 cycles of flexion-compression loading, with IDP measured at intervals.
Main Results:
- Both screw types increased IDP, with greater increases at the L2-L3 level.
- Mobile screws showed a 6.8x IDP increase at L2-L3 versus 9.1x for rigid screws after 24,000 cycles.
- Mobile screws led to statistically significant lower IDP in adjacent uninstrumented levels (L1-L2 and L4-L5).
Conclusions:
- Mobile pedicle screws generated the least increase in intradiscal pressure compared to rigid screws.
- This reduction in IDP may support spinal fusion and mitigate secondary issues like disc degeneration.
Related Concept Videos
01:27Degenerative Disc Disease I: Introduction
Degenerative disc disease is a chronic condition in which intervertebral discs gradually lose structure and function. It is not infectious or autoimmune; rather, it results from age-related biochemical and mechanical changes, influenced by genetic, metabolic, and environmental factors.Structure and Function of DiscsThe spine contains 23 intervertebral discs that absorb load, distribute forces, maintain spacing, and allow flexibility. Each disc consists of a nucleus pulposus, a gel-like core...
01:23Degenerative Disc Disease ll: Pathophysiology
The symptoms of degenerative disc disease arise from a combination of mechanical compression, vascular compromise, and biochemical inflammation, which together disrupt nerve function and produce pain.Mechanical CompressionDisc degeneration reduces height and elasticity, predisposing to herniation of the nucleus pulposus, a major cause of radicular pain. Herniations may be protrusion (bulging with intact annulus), extrusion (nucleus extends beyond disc but remains connected), or sequestration...
01:29Herniated Intervertebral Disc l: Introduction
Intervertebral disc herniation refers to the displacement of the nucleus pulposus (the gel-like inner core of the disc) through a tear or weakened area in the annulus fibrosus (the outer fibrous ring). The displaced disc material extends beyond the normal boundaries of the disc space and may compress or irritate nearby spinal nerve roots or, less commonly, the spinal cord.Etiology and Risk FactorsHerniation commonly results from degeneration, in which aging reduces disc hydration and...
01:29Increased Intracranial Pressure ll: Pathophysiology
Increased intracranial pressure (ICP) refers to a potentially life-threatening rise in pressure inside the skull. This usually happens when there is a major change in the volume of brain tissue, blood, or cerebrospinal fluid (CSF) — the three components inside the skull. According to the Monro-Kellie doctrine, if the volume of one component increases, the volumes of the other components must decrease to maintain normal pressure. If this does not happen, ICP rises.The process often begins with...
01:24Pressure Relationships in Thoracic Cavity
Breathing, otherwise known as pulmonary ventilation, is the process of air movement into and out of the lungs. The main mechanisms propelling pulmonary ventilation are atmospheric pressure (Patm), intra-pulmonary (Ppul ) or intra-alveolar pressure (Palv) within the alveoli, and intrapleural pressure (Pip) within the pleural cavity.
Breathing Mechanisms
Both intra-alveolar and intrapleural pressures rely on specific lung properties. The ability to breathe—allowing air to enter the lungs during...
Breathing Mechanisms
Both intra-alveolar and intrapleural pressures rely on specific lung properties. The ability to breathe—allowing air to enter the lungs during...
01:14Increased Intracranial Pressure l: Introduction
Intracranial hypertension is a sustained elevation of intracranial pressure (ICP) above 22 mm Hg. In supine adults, normal ICP is ~7–15 mm Hg.The rigid, nonexpandable cranium contains three components—brain tissue, blood, and cerebrospinal fluid (CSF)—that total ~1,700 mL in a typical adult: 1,400 mL brain (~80%), 150 mL blood (~10%), and 150 mL CSF (~10%). According to the Monro–Kellie doctrine, total intracranial volume is effectively fixed. When one component expands, CSF and venous blood...