Artificial intervertebral disc

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1 The University of Toledo The University of Toledo Digital Repository Master s and Doctoral Projects Artificial intervertebral disc Vikas Ghai Medical University of Ohio Follow this and additional works at: This Scholarly Project is brought to you for free and open access by The University of Toledo Digital Repository. It has been accepted for inclusion in Master s and Doctoral Projects by an authorized administrator of The University of Toledo Digital Repository. For more information, please see the repository's About page.

2 FINAL APPROVAL OF SCHOLARLY PROJECT Master of Science in Biomedical Sciences Concentration in Orthopaedic Sciences Artificial Intervertebral Disc Submitted by Vikas Ghai In partial fulfillment of the requirements for the degree of Master of Science in Biomedical Sciences Date of Presentation: April 18, 2006 Academic Advisory Committee Major Advisor Nabil Ebraheim, M.D. Dean, College of Graduate Studies Keith K. Schlender, Ph.D.

3 Artificial Intervertebral disc Vikas Ghai MSBS (Orthopaedics) Student

4 The intervertebral disc is the cornerstone of the joint complex that comprises the spinal motion segment. The functions of disc to permit limited motion and flexibility maintaining segmental stability absorbing and distributing external loads.

6 Intervertebral Disc Structure The structure of the normal intervertebral disc includes: Nucleus Pulposus: Composed primarily of proteoglycans and Type II collagen with a capacity to absorb and distribute load Annular Fibrosus: An outer annulus with well- organized layer of Type I collagen that serve to stabilize the motion segment.

8 The structure and function of the disc may be altered by processes normal physiological aging mechanical factors including trauma and repetitive stress segmental instability of the spine inflammatory and biochemical factors.

10 From a clinical standpoint general indications for disk replacement surgery include: patients with back and leg pain not responsive to appropriate non surgical treatment symptomatic 1 or 2 level disk changes associated with collapse symptomatic early stage disk changes identified by MRI and/or diskogram in the absence of facet arthritis patients without prior history of back surgery at the affected level

11 Patients with degenerative lumbar disc disease or hernia can be treated by implanting an artificial intervertebral disc (AID). Only a few AIDs have been applied clinically. The Fernstrom AID is composed of a stainless steel ball. The Charite AID is composed of two cobalt- chromium endplates, sliding on a polyethylene core.

12 Charité artificial disc

13 Both AIDs had problems with the fixation of the AID to the adjacent vertebrae. Ray replaces only the function of the nucleus pulposus of the IVD, by implanting two hydrogel capsules into the intervertebral disc. The annulus fibrosus is damaged during the implantation.

14 Endplate size is a weak point in existing AIDs. These should be large and fit vertebral bodies to prevent migration. Disc height and wedge angle should be restored, unless this would overstretch ligaments. Finally, stiffness and range of motion in all directions should equal those of the healthy disc, except for the axial rotation to relieve the facet joints. (Int( J Artif Organs 2001; 24: )

15 Migration of the AID into the vertebrae is one of the risks of an AID, especially when only the center of cancellous bone of the vertebrae supports it. The designers of the Charite disc encountered this problem in their first design and therefore developed larger endplates for their AID, but these are still not as large as the endplate of the vertebra and not supported by the cortical shell

16 Aim : To evaluate the size of the intervertebral disc and the nucleus pulposus in the lumbosacral region. Background: The size of the AID endplate should be close to the size of the adjacent vertebra. When the endplates of the AID are larger it can damage to vital structures like spinal cord and aorta. When the endplates are smaller it may subsidence into the vertebral body.

17 Method We dissected 4 cadaveric lumbosacral spines with different ages at different level, starting from the L2-3 3 to L5-S1. The size and shape of the intervertebral disc and nucleolus pulposus was measured with the help of the caliper. We also measured 4 lumbosacral IVD thickness with the help of CT scan

20 Length in millimeter N.P AP N.P. Lat. Disc AP Disc Lat. L L L L5-S

21 Length in millimeter N.P. AP N.P. Lat. Disc AP Disc Lat. L L L L5-S

25 Length in millimeter L5S1 L45 L SD Mean

26 Results Our study showed that there is no exact correlation between the level of intervertebral disc and size of the disc. The disc size and shape can be different at different levels and the size of nucleus pulposus is also unrelated to the size of disc.

27 Clinical Importance The size and shape of the Artificial Intervertebral Disc (AID) should be determine before the surgery by MRI as shape and size of intervertebral disc is different at different levels spine. Different size endplates are available to the surgeon, so the largest size possible can be used to minimize the chance of subsidence into the bone.

28 Thanks Dr Nabil Ebraheim (Orthopedics Department at Medical University of Ohio )

A Patient s Guide to Artificial Cervical Disc Replacement

A Patient s Guide to Artificial Cervical Disc Replacement Each year, hundreds of thousands of adults are diagnosed with Cervical Disc Degeneration, an upper spine condition that can cause pain and numbness