The term Keyhole Disc Replacement is in itself misleading because the procedure replaces the central portion of the disc (Nucleus Pulposus) rather than the whole disc including the Disc Wall (Annulus).
The author considers that the problems surrounding Total Disc Replacement centre on:
- The replication of an individual’s disc. The Replacements are available in a small number of sizes which fail to accurately match the disc. Patients may be tall / short, fat or thin. Patients may be asymmetrical, scoliotic and may have varieties of postures. All of these features make for a variation in the natural disc. Then the size (footprint), shape and height of all the discs (par example L3/4, L4/5 and L5/S1 discs) are all different. Manmade Replacements simply do not replicate the disc accurately.
- Their failure to replicate the complex movement patterns of a disc. Discs do not simply bend in one direction. The presence of the posterior facet joints dictates a complex ellipsoidal pattern of movements upon the disc. The orientation of these joints varies significantly from person to person. The Total Disc Replacement fails to replicate these movements.
- The use of metal as endplates which are difficult to seat accurately on the site of the original endplate. They often fail to reach the posterior vertebral body line and optimal positioning.
- The removal of the majority of the disc wall allows fibrosis to invade the implant during healing. This then impedes the movement of the device thus rendering it immobile and little better than a fusion.
The Author has sought means of restoring disc function by:
- Replacing the Nucleus Pulposus and restoring disc height
- Retaining the disc wall (annulus)
- Shrinking and reinforcing the disc wall as required
- Treating the foraminal pain sources by Endoscopic Lumbar Decompression and Foraminoplasty
I consider that restoring the Nucleus Pulposus without restoring disc height will not restore the internal metabolism of the disc and the function of the annulus. Failure to address the foraminal pain sources will result in clinical outcomes which are short lived and will equate with current modest outcomes with fusion and Total Disc Replacement. The replication of the original disc Nucleus Pulposus combined with annular reinforcement will result in a disc which is “customised” for each patient and apposite for the specific disc (size, shape and movement patterns), posture and shape of the patient.
For this reason the Spinal Foundation is working on the development of three Nucleus Pulposus Replacements.
Please contact the Spinal Foundation for more information on Keyhole Disc Replacement and to see if you are eligable for surgery.