Lumbar Spinal Fusion

Segments of the spine move. Each spinal motion segment moves because of the elastic nature of the disc at the front of the spine, coupled with the gliding joints at the back of the spine (facet joints), which help take a proportion of the spinal load and control movement of a particular spinal motion segment. Pain can arise from a motion segment for several reasons.

• The disc itself can degenerate and become painful. This is known as "discogenic pain".
• The small knuckle joints at the back of the spine can become dysfunctional , arthritic or inflamed and cause pain (facet joint syndrome).
• These can combine to cause abnormal movement or reduced space for the spinal nerves as they pass between the disc and joints (spinal instability/spinal stenosis)

Fusion of a spinal motion segment can be offered to patients with back pain with or without nerve compression symptoms pain when other treatment methods have failed. There are other reasons for which a spinal fusion is performed which are rare e.g. trauma, tumours, deformity. Spinal fusion is a surgical procedure resulting in bone growing across the spinal motion segment so as to stop its (abnormal) movement.
There are several techniques that can be used to fuse the spine, each of which have their advantages and disadvantages, their proponents and opponents.
Surgical approaches can either be posterior or anterior, or combined.
Posterior spinal fusions involve an incision over the base of the spine muscles can either be split or retracted to reach the spine.
Anterior approaches involve an incision either at the front or side of the abdomen where direct access to the disc at the front of the spine can be achieved.
Despite techniques for establishing the cause of spinal pain and appropriate treatment being carried out, approximately 25% of patients undergoing spinal surgery end up with continuing symptoms that trouble them. These 25% of patients, if assessed carefully for disability or measured as to how limited they are by symptoms, tend to be slightly better than before surgery Thankfully, the number who come out of surgery with worse symptoms is extremely low.

Minimally Invasive Spinal Surgery:

Minimally Invasive Spinal Surgery involves performing spinal surgical procedures, such as fusion, using techniques and technology to minimise the insult to tissue whilst gang access to perform the procedure. Traditional spinal surgical techniques would involve long incisions in the back and stripping of muscles from the spine. This would cause both significant pain in the early post-operative period and also dysfunction and scarring of the muscles of the spine. Minimally invasive techniques to insert, for example, pedicle screws involves small incisions(15mm) and passing the screws through working tubes using X-ray control. Lateral fusion techniques allow removal of disc and insertion of implants through incisions of approximately 3 cm, again using specially designed retractor systems to allow direct vision of the spine through small working channels.

Mr McKenna has extensive experience in Minimally Invasive Lateral Spinal Surgery and is validated as a proctor surgeon for XLIF. Circle Hospital is one of two national visitation sites to train visiting surgeons to perform XLIF surgery. Lateral interbody fusions (XLIF) can be carried out through small incisions in the side/flank. The intervertebral disc can be removed through the small incision and deformity in the spine reduced through insertion of the XLIF implant developed by Nuvasive (
Link). The stability of the fusion is enhanced by percutaneous placed pedicle screws placed through small incisions in the back. The pedicle screw system used is Precept by Nuvasive. During the procedure, small needle electrodes are placed in the muscles of the lower limbs and lumbar nerves are continuously monitored throughout the procedure to ensure that the risk of nerve damage is kept to a minimum. This system allows for reduction of spinal deformity, for example in degenerative scoliosis or spondlyolisthesis, with a minimally invasive technique. Reducing the traumatic insult to the tissues using these techniques results in a speedier recovery than that expected from open surgical techniques. Mr McKenna is a

Less Invasive Spinal Systems:

The surgical management of the adult degenerative spine has developed significantly over the last decade. The Techtonix fusion system is a system used for spinal fusion. It enables a major spinal fusion addressing both the front and back of the spine to be performed through a small incision at the back of the lumbar spine. In a slim patient, the incision is as little as 4 cm in length. The advantages of such a system is to enable rapid recovery from the surgery as a result of minimal tissue disruption. It utilizes a technique whereby the nutrient artery to the large spinal muscles is not sacrificed, as it is in the traditional spinal fusion. There are several other similar techniques, such as MAS-PLIF from Nuvasive, that Mr McKenna is also trained to perform. The implant and technique for fusion surgery is decided on after several factors have been taken into account. Mr McKenna will discuss the options with you in the clinic before a decision on technique is made.

Anterior Spinal Fusion:

People are often surprised to be offered surgery for low back pain where the surgical access is through a small incision in the front of the abdomen. The disc that can be the cause of low back pain is at the front of the spine - if you relax enough and press deep into your abdomen you can feel the spine and occasionally the disc as well. The most efficient route to the disc is via this anterior approach. The spine can be accessed without cutting through any muscle and without having to manipulate the spinal nerves. Again, the approach to the spine can be performed through a minimally invasive technique utilizing a skin incision that is between 4 and 5 cm long. The implant used is TM400 by Zimmer. This particular implant is made of trabecular metal which is a tantalum mesh that provides excellent primary stability and fusion without the need for bone grafting. The implant stability is enhance by the use of an anterior plate and screws to prevent movement in extension and rotation.

Total Disc Replacement:

Both the cervical and lumbar disc replacements have NICE approval.

Lumbar disc replacement:
Over the last 10 years, there has been a movement away from spinal fusion in younger patients with one or two level disc degeneration who have failed conservative management of low back pain. To preserve movement at a spinal level whilst removing the pain generator (disc), has potential advantages in preserving the health of the adjacent discs whilst reducing the symptoms of discogenic pain. The patients must fit the strict criteria and relatively few patients with low back pain can be considered for the procedure and all patients are being followed up as a prospective cohort at this time with appropriate outcome measurements being collected in clinic. The disc used is the M6 or the Prodisc-L.

Cervical total disc replacement

The indications for cervical disc replacement include discogenic neck pain and radiculopathy refractory to conservative measures– the same as for anterior cervical discectomy and fusion (ACDF). Adjacent level disease after conventional fusion is a real problem; one in five fusion patients require surgery at the adjacent level within 10 years of a fusion. Preserving movement with a disc replacement whilst decompressing the nerve and removing the degenerate disc achieves the same result and theoretically should save the adjacent level disease. Again, there are strict criteria for suitable patients and all patients are followed up meticulously. The disc replacement used is the
Prodisc-C Vivo by Depuy-Synthes. It is becoming clear as research into the long term results of total disc replacement surgery becomes available, that the need for further surgery at the adjacent levels appears to be reduced when compared to fusion.

Spinal Injections:

A large proportion of patients with a disc herniation causing cervical or lumbar radiculopathy resulting in arm or leg pain will settle without treatment. Spinal injections are useful in resolving those symptoms or reducing them until the natural history results in resolution of the pain. These injections are perfomed under X-ray guidance.  Mr McKenna also performs facet joint injections and denervation of facet joint using radiofrequency ablation (facet joint rhizolysis).

Interspinous Devices:

There are several interspinous devices available for implantation. They are considered to be of questionable benefit by many surgeons but have become very popular over the last few years with excellent results being published. The most commonly used implants would be Coflex, Diam, Wallis and X-stop. They fulfil slightly different roles. Mr McKenna performs surgery that is enhanced by interspinous devices only in very select patients in whom he feels the longer term outcome would be better with a form of posterior stabilisation, but in who fusion would be to invasive.

Wallis ligament:
The Wallis stabilization system is an implant placed between the spinous processes of the spine.
It functions in several ways. It distracts the spinous processes and unloads the posterior elements of the spine (facet joints and posterior part of the disc). It changes the centre of rotation of the disc. It restricts flexion and extension of that segment of spine. It increases the surface area of the spinal canal (the space available for nerves) and it increases the exiting neural foramina (the “keyhole” where the nerves pass out of the bony spinal canal. It is not possible to insert a Wallis into the lowest motion segment (L5/S1) - spinal anatomy does not usually allow it.

The indications for use are quite wide and include discogenic low back pain, spinal stenosis, neuroforaminal stenosis, disc herniation and recurrent disc herniation.
Surgery involves admission to hospital and a stay of 1 -2 days. The procedure requires a general anaesthetic. An incision approximately 5 cm long is made vertically in the middle of the lumbar spine. The supraspinous ligament is preserved and retracted and the muscles gently detatched from the spinous processes to allow access. A space is made for the implant by excising the interspinous ligament which runs between the spinous processes. The implant size is decided and the implant inserted. The nylon braided “ligaments” are passed through the interspinous spaces above and below the stabilized motion segment. The construction is tensioned. The wound is closed in layers and infiltrated with local anaesthetic for post-operative pain control.
Post-operatively patients can mobilise immediately (on the day of surgery). The physiotherapist will visit the patient on the first post-operative day and teach a range of movement and strengthening exercises. Restrictions in the first 6 weeks are limited to avoidance of heavy lifting only. Gentle exercise is encouraged from an early stage which can include swimming from the second week as long as the wound has healed.
Complications of this procedure are extremely low as the spinal canal is not entered and therefore there is no risk to the spinal nerves. Infection is the only significant risk and there is less than a 1% chance of that occurring.

One of the advantages of the Wallis is that the procedure is reversible; the implant can be removed easily if symptoms do not resolve and further (usually more invasive) procedures can be performed if necessary.
The implant is a useful tool for a spinal surgeon and an alternative to disc replacement in some cases.