The sacroiliac joint, located in the pelvis, links the iliac bone (pelvis) to the sacrum (lowest part of the spine above the tailbone). This joint transfers weight between your upper body and legs. It is also a vital component of shock absorption and helps to prevent the force of impact during walking from reaching the spine.
A network of ligaments and muscles stabilize the sacroiliac (SI) joint. In normal SI joints, there is relatively little motion and this is true in any direction. There are normally less than four degrees of rotation and two millimeters of translation at these joints. Most of the motion in the pelvis area occurs either at the hips or the lumbar spine. These joints support the entire weight of the upper body when we are standing, which places a large amount of stress across them. This can lead to wearing of the cartilage of the SI joints, which will eventually develop into arthritis. The sacroiliac ligaments in women are less stiff than in men, allowing the mobility necessary for childbirth.
Studies have revealed that up to 25% of all lower back pain is caused by the sacroiliac joint. Other studies have shown that people who have pain following lumbar spine surgery frequently have pain from the SI joint.
The most common symptom of SI joint dysfunction is pain. Patients often experience pain in the lower back or the back of the hips. Pain may also be present in the groin and thighs. Other common symptoms include:
The first step in diagnosis is typically a thorough history and physical examination by a physician.
The next step is often standard X-rays. X-rays may be prescribed of the pelvis, hips, or lumbar spine depending on what the physician finds during the history and physical examination. Computed tomography (CAT or CT) scan, or magnetic resonance imaging (MRI) may also help in the diagnosis. However, the ‘gold standard’ of diagnosis for this condition is image-guided injection of anesthesia into the SI joint. The injection is delivered with either X-ray or CT guidance to ensure accurate placement of the needle in the SI joint. If symptoms are decreased by at least 75%, it can be determined that the SI joint is either the source of low back pain or a major contributor to that pain. If the pain level does not change after the SI joint injection, it is less likely that this joint is the cause of low back pain.
Before surgery is considered, all non-invasive treatments are exhausted as pain relieving methods. Those measures may include physical therapy, oral medications or injection therapy (injections described above are used as both diagnostic and treatment).
Surgery for SI dysfunction is considered only if other less invasive treatments have been unsuccessful. This surgery involves a fusion of the SI joints, in which the cartilage covering the surfaces of the SI joints is removed and the bones are held together with plates and screws until they grow together (fuse). This eliminates all motion at the SI joints and typically relieves the pain.
The minimally invasive procedure is done through a small incision (two or three centimeters long) along the side of the buttock and takes about an hour. Typically, three small titanium implants are inserted across the SI joint. These implants are designed to create a durable construction which will stabilize the SI joint.
In a study of open versus minimally invasive sacroiliac joint fusion, patients who underwent either Open Surgery (OS) or Minimally Invasive Surgery (MIS) for SI joint fusion showed postoperative improvements in pain score. Compared to OS patients, patients who underwent MIS SI joint fusion had significantly greater pain relief and more favorable perioperative surgical measures.