Complex fusion with pedicle screws
LUMBAR FUSION WITH PEDICLE FIXATION AND INTERBODY FUSION
In certain situations such as spondylolisthesis, degenerative disc disease or instability following previous surgery lumbar fusion may be indicated.
If the bone is deficient it may be necessary to use substantial screws which pass from the back into the front of the vertebrae down the pedicles (hence pedicle screws) which are joined by rods and so markedly restrict motion.
Where the disc is still mobile I use a combination of bone graft and usually a metal spacer (made of Titanium mesh) within the disc as well as bone graft placed down each side of the spine on left and right between the transverse processes and/or sacrum as well as within the facet joints.
We then put the pedicle screws in and join them with rods. This combination of methods has several advantages, especially early rigidity and only few disadvantages.
By placing bone in the disc, with or without a spacer, one improves the fusion rate and help maintain the spine's normal backward curve (lordosis) - this reduces the incidence of late problems at the next level up and reduces the incidence of screw breakage or pullout.
The fusion process takes several months and is similar to the healing of a fracture. The cancellous bone graft (marrow bone) is taken via a trap-door from inside the back of the pelvic bone, usually via the same skin incision, and does not usually cause problems apart from the occasional swelling due to bleeding. This method is less painful but the bone donor area can be sore for several months.
Occasionally, despite our best intentions and with Xray control, the pedicle screws can irritate a nerve and require replacement. This occurs in about one per cent of my cases.
With this combination of methods the vast majority of "fusions" do indeed achieve fusion - providing the patient follows instructions, does not smoke and does not take anti-inflammatories after leaving hospital (eg Voltaren, Brufen, Oruvail, Nurofen, Tilcotil, Naprosyn &c can all impair bone healing).
This operation takes about three hours for one level and four to five hours for two levels - longer in revision cases and in patients who are overweight. Blood transfusion is rarely required (less than 1% of cases and mainly two level fusions).
Despite achieving a solid fusion most patients have some residual pain while in a few the pain is unchanged (rarely is it worse).
Any surgery under general anaesthesia entails risks. These may include pain, nausea and vomiting, drug reactions, problems with the mouth and larynx (voice-box), stomach and intestinal upset including diarrhoea or constipation. Rarely, chest infection, lung collapse, pneumonia, clot, stroke, ulcer or even death. Infection is an occasional risk and damage to nerves can occur (smalll tears of the lining of the nerve can usually be repaired but will require a period of complete bed rest for two or three days). All precautions are taken to minimize these and serious complications occur in less than 1% of cases.
From my own series of over 2400 cases there have been two pneumonias, three leg clots, three lung clots (one fatal), two serious deep infections, several drug related liver reactions, two temporary cauda compressions due to bleeding (resolved), two divided nerves but no permanent paralysis. Death can occur.
Irritation of nerves due to traction or damage to the nerve may leave residual pain or numbness.
Occasionally, after fusion has occurred, the screws may be removed to remove local tenderness.
As the screws, rods and cage/s are made of titanium they are relatively inert, shouldn't set off airport metal detectors and still allow MRI or CT scans to be taken.