Synthetic Lumbar Intervertebral Disk for Medical Education

[+] Author and Article Information
Nicolas V. Jaumard, Robert C. Richards

Department of Mechanical Engineering, University of Kansas, Lawrence, KS 66045

Susan M. Stagg-Williams

Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS 66045

Elizabeth A. Friis1

Department of Mechanical Engineering, University of Kansas, Lawrence, KS 66045lfriis@ku.edu


Corresponding author.

J. Med. Devices 1(3), 212-216 (Aug 07, 2007) (5 pages) doi:10.1115/1.2778701 History: Received July 28, 2006; Revised August 07, 2007

Surgical treatment interventions for low-back pain are increasing. Surgical risk associated with new techniques can be reduced by practice on synthetic spine replicas. However, current models for surgical training on intervertebral disk procedures do not represent average patients because they exhibit variable degrees of degeneration. A low-cost synthetic intervertebral disk device with lifelike sensory and visual feedback to enhance surgeon training was developed. Design criteria for the synthetic analog intervertebral disks (IVDs) were based on observations of fresh frozen human cadaveric disks, surgeon input, and literature descriptions; prototypes were designed to mimic a Grade I-II lumbar IVD. Qualitative evaluation was done by interviewing orthopedic surgeons during mock surgeries on the model. The surgical feel was quantitatively evaluated by a mock nucleotomy on prototypes and cadaveric specimens using instrumented surgical tools. In qualitative analysis, two orthopedic surgeons commented that the visual and tactile qualities of the model were similar to disks of adult spine surgery patients. Quantitative test results showed similarities between human and analog disks. The inexpensive synthetic IVD design successfully replicated the main features of a human cadaveric disk.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

The upbiting pituitary with strain gages mounted on both sides of the moving handle used to apply force when grabbing NP material. Strain gage locations are indicated by arrows.

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Figure 2

First generation model of the synthetic silicone-matrix disk sandwiched between two foam vertebrae (Sawbones®) to form a FSU for testing. The model in the picture is soaking in water to hydrate prior to testing.

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Figure 3

Removal of some NP material with the pituitary from a silicone-matrix prototype disk in the FSU model. The pituitary is grasping a portion of the synthetic NP and pulling through the space where the square AF chunk was removed.

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Figure 4

Average pituitary strains during AF chunk removal and NP removal in synthetic and human disks. Human disks (Levels L3-L4 and L4-L5) were Grade III or IV in five 74–78year old specimens compared to the designed Grade I to II synthetic disks (n=10, 6, and 8, respectively). : Second, third, and fourth NP removal pituitary strains are global averages.

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Figure 5

Transverse cross section of a synthetic disk after testing from both the medial and lateral sides with the upbiting pituitary. Multiple hydrated layers can be seen in the AF and the NP appears slimy and slightly fibrous. Note that much of the NP has been removed during testing.




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