A segment of the spine is permanently immobilised. This is usually done by stabilising the spine with metal work (screws, rods or plates) and bone grafting to allow the spinal segment to fuse. It can be done over several levels. There are a variety of different techniques available depending on the underlying condition and surgeon’s preference. There is an important difference between fixation and fusion. The purpose of the implanted metal work is to hold the vertebral bodies in place (fixation) until these have fused. Therefore a good bone graft is important. If the bones do not fuse (non-union) there is a significant risk that the spine will remain painful. Eventually, the metal may break. There are several factors which can influence bony healing and fusion. These include medical conditions like malnutrition (rare in developed countries but also seen in alcohol dependency), diabetes and osteoporosis but also smoking, and use of non-steroidal anti-inflammatory drugs (NSAIDs) like Brufen, Iboprofen, Diclofenac). There are also other factors like infection, poor local blood supply, biomechanical instability and poor bone contact of the graft. It is very important for patients to stop smoking when having a spinal fusion (or in fact any bony fusion or fracture) because this is the single most common reason for a fusion failure.
Stabilisation of a spinal segment for slippage (spondylolisthesis), low back pain due to severe degeneration or instability.
Bleeding, Infection, CSF-leak, neurological deficit including paralysis, incontinence (no bowel or bladder control), no improvement of symptoms, failure of implanted metalwork, non-union (see above). In anterior approaches to the lower lumbar spine there is a risk of retrograde ejaculation in men causing inability to father a child. In the long term, there is a risk that the level next to the fused segment can wear out quicker (so-called ‘adjacent level disease’). Fusion of two vertebrae will eliminate any movement, which means that other segments have to move more. This can lead to increased degeneration years after surgery. There is, however, no clear evidence that this happens or to what degree other level wear out quicker. It is for this reason artificial discs (disc replacements) were designed. Overall, the risks, in particular the very serious risks are small in experienced hands.Hospital stay
Very variable and depending on the underlying condition and extend of procedure. Usually 3-5 days in uncomplicated cases.
General anaesthesia except in rare circumstances
PLF (postero-lateral fusion)
This technique can be done either with or without instrumentation (metal work). In fusion without metal work (non-instrumented fusion) only a bone graft is required, which is placed at the back and sides of the vertebra. Patients will usually need to wear a brace for a few months afterwards. With the technical advance of implants, only few spinal surgeons still perform this technique. In instrumented fusion (pedicle screw fixation) screws are inserted through the pedicle into the vertebral body (see ‘The Normal Structure of the Spine’). These are connected with rods.
PLIF (posterior lumbar interbody fusion)
Through a midline incision the disc between two vertebrae is removed and the nerves decompressed. A cage is inserted as a spacer into the disc space. Screws are place in the pedicles of the vertebra and connected with rods (as in pedicle screw fixation – above). A bone graft is placed into and around the cage and sides of the spine.
TLIF (transforaminal lumbar interbody fusion)
Similar to PLIF. One facet joint (a small joint connection to adjacent vertebra) is resected to allow access to the disc space. This procedure is usually less traumatic for the muscles.
ALIF (anterior lumbar interbody fusion)
The spine is fused through an incision in the abdomen which allows access to the front of the spine. A simple cage is not indicated and will require additional support from the front (plate) or through a additional procedure from the back (pedicle screw fixation). The main advantage of this technique is that the back muscles will not be affected. However, the large vessels in front of the spine and other pelvic organs are at risk.
XLIF (extreme lateral interbody fusion)
The spine is fused through an incision at the side of the abdomen (flank). As for ALIF a simple cage is not indicated and will require additional support from the side with a plate or more commonly through a additional procedure from the back (pedicle screw fixation) which can be done minimal-invasive.
Depending on the underlying condition. Up to 30% of patients undergoing a lumbar fusion for lower back pain in the absence of instability will have minimal or no improvement of the pain. This should be borne in mind when considering surgery for back pain.
Depending on the underlying condition. The back will feel sore for a few weeks. It is important to know that it will take at least 3-4 months for the bone to fuse and therefore pre-existing pain might take a while to improve.
Commonly asked questions
Are some techniques better than others?
All of these fusion techniques have advantages and disadvantages. Which technique is used for a specific case depends on the underlying problem and surgeon’s preference.