Introduction
Lower back pain is a very common complaint encountered at a doctor’s office; every individual experiences lower back pain at some point or the other in life. Be it a desk job that requires long hours of seated posture or an athletic career involving extreme physical activity and rigorous training, lower back pain could be a byproduct of almost all professions. It is estimated that about 2.3 % of all visits to physicians are due to a lower back pain-centered complaint. Just as common as it is, it can result from a wide range of causes. About 10 % of the population in the United States suffers from chronic lower back pain. Sacroiliac joint dysfunction frequently presents with lower back pain but is commonly overlooked due to its complex nature.
What Is the Sacroiliac Joint (SIJ) and What Is Its Function?
The sacroiliac joint is a C-shaped synovial joint present bilaterally, situated at the junction between the sacrum and the pelvis on either side. It is surrounded by a fibrous capsule and stabilizes the sacrum against the ilia. It is the largest axial joint in the human body. It connects the spine and the pelvis (a basin shaped bone complex connecting the trunk of the body to the legs). Its primary function is to transfer load from the lumbar spine to the lower extremities. Many ligaments cross the joint. While these ligaments support the joint they also limit its movement. The fact that the sacrum is tightly wedged between the hip bones combined with the ligaments surrounding it, gives the joint resistance against shear loads. Though large and important muscles surround this joint, they do not contribute to the joint movement. The joint has a minimal range of motion, it can move about six degrees with respect to the ilium. Dimorphic variations (sex differences) in the joint exist due to the anatomy of the pelvis. Men have a longer and narrower pelvis as opposed to a more conical pelvic cavity in females. This gives women greater mobility, stresses, load and ligament strains in comparison to men.
Some important anatomic relations of the joint include nerves like the L5 ventral ramus and lumbosacral trunk passing anteriorly and S1 nerve ventral ramus passing inferiorly. Nerve supply to the joint is through nerve roots of dorsal rami of L4-S3 which transmit pain and temperature.
What Are the Causes of Sacroiliac Joint Dysfunction?
Injury to the SIJ can be described in terms of a disrupted joint capsule, strain in the ligaments involved, inflammation of muscles, infection, shearing fractures or arthritis. The causes of SIJ dysfunction could be intra-articular or extra-articular. Pain in SIJ dysfunction can be spontaneous or result from trauma and repetitive shearing loads. Some of the causes of SIJ dysfunction include:
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Injury: Injury from a fall on the buttocks, road traffic accidents, sports injuries, etc have a forceful impact. This can strain or even tear joint ligaments.
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Arthritis: A degenerative bone disorder, can affect the SIJ. All joints are lined by cartilage and have synovial fluid which decrease friction and help smooth joint movement. Arthritis is characterized by wearing down of the cartilage and fluid resulting in increased friction, inflammation and dysfunction of the joint.
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Hypermobility: Too much joint movement occurring due to the loosening of the ligaments connecting the sacrum and pelvis causes instability.
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Hypomobility: Inadequate movement can result in fixation and stiffness of the joint.
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Pregnancy: During pregnancy there is increased stretching of the ligaments in preparation for childbirth. This combined with the extra weight contributes to wear of cartilage in the joint causing inflammation and pain.
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Ankylosing Spondylitis: A chronic inflammatory disease involving fusion of the SIJ and leads to decreased flexibility and limitation of motion.
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Leg-length Discrepancies: Where one leg is either longer or weaker than the other causes unequal distribution of stresses in the pelvis.
Who Is at Risk?
Individuals with a history of lumbar fusion, pregnant women, athletes subjected to sustained physical activity, scoliosis, etc. are more susceptible to develop SIJ dysfunction. Sero-negative HLA-B27, leg length discrepancies since birth, gait abnormalities, etc. are also predisposing factors. About 15 to 30 % of patients reporting with lower back pain are estimated to have SIJ dysfunction.
What Are the Symptoms?
Pain is the most common symptom. It can vary from mild to severe and it can last a week or even three months. The pain may be continuous or intermittent in nature, aggravated by certain postures or movements. It may be localized to a small region inferior to the affected joint or can be referred to the groin, buttocks, posterior thighs or the lower legs with radicular symptoms.
How Is the Condition Diagnosed?
Diagnosing SIJ dysfunction can be challenging since back pain is multifactorial and it cannot be straight away attributed to SIJ dysfunction with absolute certainty. The evaluation criteria proposed by the International Association for the Study of Pain include:
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Pain should be present in the SIJ area.
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Pain is intensified in certain aggravating maneuvers.
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Pain is relieved on injection of a local anesthetic agent in the joint.
Further, pain due to SIJ dysfunction is never above the L5 nerve sensory distribution. Patients describe the pain to be recurrent and aggravated on bending and twisting motions. Pain can also be associated with changes in bladder function and dyspareunia (painful intercourse).
Tests that aid in the diagnosis include:
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Distraction and thigh thrust tests are maneuvers to identify SIJ dysfunction. If these two tests are positive, additionally a compression test and sacral thrust test could also mean SIJ dysfunction. Another test called the Gaenslen’s test may be optionally performed. All these tests involve eliciting responses from various postures and stress at different points and angles. If these provocation tests are negative, SIJ dysfunction can be ruled out.
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Imaging tests like X-rays, CT (computed tomography) and MRI (magnetic resonance imaging) scans help the physician rule out other possible causes for pain like osteoarthritis and identify inflammatory or degenerative changes within the joint. Further SPECT-CT (single photon emission computed tomography) is an advanced technique that can demonstrate the loss of characteristic dumb-bell shape due to a mechanical failure of load transfer.
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Fluoroscopy guided intra articular injection of Lidocaine (local anesthetic) or Triamcinolone (steroid) is both diagnostic and therapeutic. However, its diagnostic validity is questionable. Periarticular injections could be performed.
Pain due to conditions such as facet joints, back strain from lifting, disc herniation, sciatica, hip arthropathy, etc. are commonly confused with SIJ dysfunction.
What Are the Treatment Options?
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Conservative measures like cold or warm compress and rest.
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Anti-inflammatory medication (such as Ibuprofen or Naproxen) to reduce the swelling and painkillers like Acetaminophen to manage pain.
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Physical manipulation by a chiropractor, osteopathic doctor or other qualified health professionals can help in cases of a fixated or stuck joint. Posture manipulation, block technique and instrument-guided methods may be employed.
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Supports or braces for stabilization when the sacroiliac joint is hypermobile.
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Controlled physical therapy to strengthen the muscles around the SIJ and increase range of motion.
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Low-impact aerobic exercise increases the flow of blood to the area, thereby stimulating a healing response.
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Sacroiliac joint injections.
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Stem-cell regeneration is a non-invasive measure where stem cells are injected paraspinally and ligaments under CT guidance. The cells bring about repair and regeneration of the joint, stimulated by the inflammatory signals present. Shockwave and other supportive therapies can be performed as an adjunct.
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If these treatments prove unsuccessful, surgery can be performed. One or both of the SIJs are fused to eliminate abnormal motion.
Conclusion
Any abnormality or injury to the sacroiliac joint present at the base of the spine can result in lower back pain and reduced mobility. Diagnosis of this condition proves challenging since back pain is multifactorial. Physical examination and imaging tests aid in diagnosis.
