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Lumbar Disc Replacement

Why do it?

If a lumbar disc (low back) is felt to be a pain source then it is a relatively logical step to consider getting rid of it. The information for this conclusion comes from the history, examination, MRI scan and/or discogram.

What operations are possible?

The operations available for this are either excising the disc and fusing the resultant space, or excising and replacing it with a disc replacement.

What do these operations hope to do, and how are they done?

The fusion will stop all movement at that level but the disc replacement will hopefully maintain movement. The fusion can be performed through the belly alone, from the back alone, or both. The disc replacement is performed through the belly.

What are the risks of disc replacement?

The risks of disc replacement are the risks of the anterior approach and implantation of a foreign body (the implant). This is an approach that has been used for many years. It involves an incision in the belly; either a Pfannenstiel incision (the one that is used for caesarean sections in women) or a paramedian incision (a straight up/down incision just slightly off the midline of the belly).

The risks are (from superficial to deep):

  • Wound problems: infection; late opening of the wound; hernia
  • Bowel problems: puncture of bowel (rare) which can lead to peritonitis; ileus (slowing down of the bowel for a few days after operation)
  • Injury to great vessels (aorta and vena cava): bleeding, death, aneurysm
  • Injury to the autonomic nerve plexus on the front of the spine: retrograde ejaculation in men, not certain of effects in women. Also can give a warm leg postoperatively for an unspecified time.
  • Spine: infection (osteomyelitis); implant movement/dislodgement/collapse into the vertebral body above or below. The spinal cord does not extend to the lower lumbar spinal canal, so it cannot be injured with this approach. The roots however can be injured but this is a very rare event in this type of operation.
  • Implant: loosening; wear; revision.

What types of disc replacement are there?

Several manufacturers are currently researching, developing and testing total disc replacements (ProDisc (Spine Solutions/ Synthes), Charité (DePuy Spine/Johnson & Johnson), and Active L (BBraun Aesculap)). The one I use is Active L.

This has two cobalt/chrome endplates with plasmapore titanium covering which allows bone to grow into them, separated by an ultra high molecular weight polyethylene (plastic) spacer (UHMWPE). The plastic is captive within the lower endplate so that it cannot come out but it is able to move 2 mm front and back.

Which ones have I used?

I used to use the ProDisc. This was shown to give a significant reduction in patient-reported back pain and leg pain. 92.7% of these patients in one series were "satisfied" or "extremely satisfied” with the procedure. Two-thirds of these patients had single level implants while one-third had two level ProDiscs. There was no outcome difference between the 1 and 2 level ProDisc implantations.

I now use the Active L which is very similar to the ProDisc other than it has a mobile bearing surface (to closer mimic the changing centre of rotation of the natural disc during movement), and it has different methods of initial fixation to bone.

When should a disc replacement not be put in?

Exclusion criteria for not putting a disc replacement in, include active systemic infection or infection localized to the site of implantation, osteoporosis, osteopenia, bony lumbar stenosis, allergy or sensitivity to implant materials, isolated nerve root compression syndromes (sciatica), or a pars defect (spondylolysis, instability).

What do other people think about disc replacement?

The FDA (Federal Drug Administration in the USA) have approved Charite for use as a disc replacement in the US and are expected to approve the Prodisc. In the UK, NICE (National Institute for Clinical Excellence) have now stated that disc replacement in general is a valid procedure that can be performed in the UK with proper auditing of results. I have been implanting Active L since May 2005 and will be auditing my results on a yearly basis.