Robert Lee, Consultant Spinal Surgeon at the Royal National Orthopaedic Hospital, talks about problems with the joint that connects the pelvis to the spine
Lower back pain affects up to 90 percent of adults at some point in their life. Most of the time, this is simply a muscle strain that improves with rest and painkillers. Sometimes the symptoms are bad enough to warrant treatment by a physiotherapist, chiropractor or osteopath. When back pain persists for a long period of time despite all these alternative treatments, then advice is sought from a specialist such as a spine surgeon. This is because there is often a structural problem with the spine which may be giving rise to these symptoms.
One of the first investigations performed is an MRI scan—basically a big magnet that produces a three-dimensional picture of the spine which allows the surgeon to visualise the bones (vertebral bodies) and soft tissues (intervertebral discs, ligaments and nerves). This can show problems with degeneration of the discs (beyond what you would expect with old age) as well as wear and tear in the joints and nerve compression (which can give pain down the leg known as sciatica). One of the common misconceptions is that an abnormal MRI scan must mean you should suffer with back pain. In actual fact there are many people walking around with very abnormal scans with lots of degenerative changes who have very little back pain. The reverse is also true and there are people with minimal abnormalities who suffer badly with back pain. This is because we compensate for problems in our back by activating our back muscles—this is why core-strengthening exercises are important; some people with back pain simply have weak back muscles.
Moreover, there are about 30 percent of people who think they have back pain coming from their spine when in fact it is coming from lower down.
The lumbar spine connects to the pelvis via a structure called the sacroiliac joint (SI joint). The brim of the pelvis is the structure your belt rests on and if you run your hands backwards towards your buttocks, the point on either side of your spine that meets the pelvis is the SI joint. This joint has hardly any movement. It’s not like your hip or knee joint that has a large range of movement, the SI joint only moves a few millimetres, if at all. The problem is when it moves too much or becomes inflamed. This can lead to quite severe back pain. Typically, people with SI joint problems have pain that emanates from a point either side of the spine around the buttock area. Some people can even put a finger on the spot that is painful. The pain can worsen on twisting and with activity. Sitting for a long time can also lead to severe pain. There is also a nerve very close to the SI joint that becomes irritated and causes pain down the leg, which can imitate sciatica. Some patients who have had previous lower lumbar fusions get SI joint pain too.
Diagnosing back pain as SI joint pain is based on checks of a patient’s clinical history and the examination findings. Where the diagnosis is suspected, an injection of local anaesthetic and steroids can be tried to see if this eliminates the pain. Even if it takes away the pain for a short period of time, then at least a definitive diagnosis can be made.
The treatment of SI joint pain begins with rehabilitation involving physiotherapy, chiropractor or osteopathy. If this fails and an injection has proven the diagnosis, then pain management specialists can attempt to numb the nerves to the joint via a process called radiofrequency denervation. If all else fails and the patient’s back pain is bad enough, then fusion of the SI joint can be considered. In the right patient this is an extremely successful operation but the key here is getting the right diagnosis. The operation is performed via a minimally invasive technique where screws or titanium cages are driven across the joint. Usually two to three cages are inserted and over time, bone grows onto or through the cages to stop movement. Recovery usually takes two to three months and involves using crutches to prevent putting the whole body weight through the fused joint. This surgery is approved by NICE (National Institute For Health and Clinical Excellence).
At the Royal National Orthopaedic Hospital (RNOH) in Stanmore this surgery is offered to patients who fulfil the diagnostic criteria. Computer navigation technology is used to prevent cage malposition – the SI joint has a small cross-sectional area and missing the joint can lead to permanent nerve damage if the operation is not done correctly. Given the expertise of the surgeons with this technology at the RNOH, patients who need this type of surgery are often referred there for surgical management.