Sacroiliac Joint Dysfunction & Fusion Surgery​

The sacroiliac joint is formed between the pelvic bones and the lower part of the spine known as the sacrum. The sacrum consists of five sacral vertebrae joined together to form a single bone. The two iliac bones of the pelvis form a joint with the sacrum, one on each side of the body. The Sacroiliac joint is responsible for connecting the lower extremities with the pelvis to the spine. The unique position of the sacroiliac joint cushions the impact of day to day activities.

Bilateral sacroiliac joints as seen on X-ray of the pelvis in anteroposterior view.

Sacroiliac joint dysfunction is a degenerative condition of the SI joint which may frequently result in lower back pain. The location of the pain is also the site of referral of pain from other spine pathologies. The pain from SI dysfunction however stays below the lower back. The pain may also radiate down the legs to the foot. Patients may often report alleviation of symptoms when wearing a tight belt.

Although minimal, the sacroiliac joint has movement in various planes such as gliding, rotation, tilting, translation, and nodding. These complex movements are aided with help of a large group of muscles and strong ligaments attached to the joint. However, the joint motion decreases progressively with age and the joint may be naturally fused in the elderly population.

The cause of SI dysfunction is generally a result of repetitive trauma to the joint. The repetitive motion may cause wear and tear of the structures in the joint causing pain. The joint is the primary pathology in inflammatory diseases such as ankylosing spondylitis and Reiter disease.

The joint is may also be involved due to systemic diseases such as gout, hyperparathyroidism, acromegaly, or renal failure. A prior lower back spinal fusion surgery or any trauma/injury to the SI joint may also lead to SI joint dysfunction. Rarely infections and tumors may cause SI joint dysfunction.

The diagnosis of sacroiliac joint dysfunction requires a thorough examination by an orthopedic spine surgeon. The physician will extract a thorough history of the symptoms and the events leading to them. Physical examination includes conducting special tests to localize the pain and exclude any other causes of pain.

Radiological investigations are followed along with blood investigations. An X-ray is usually performed with special views to visualize the SI joint. MRI of the pelvis may be obtained to visualize soft tissue structures and rule out any other pelvic pathology. Bone scans may be used when the physician suspects SI joint infection.

Management of SI joint dysfunction is usually conservative. Conservative management involves the use of NSAIDs to reduce inflammation and swelling. Physical therapy along with heat/cold therapy is aimed to strengthen the core muscles and improve flexibility. SI joint cortisone injections may be used for pain relief and also as a diagnosing tool.

Surgery is reserved for patients in whom, conservative management has failed to resolve symptoms. Sacroiliac joint fusion surgery involves the use of small triangular-shaped implants through the SI joint to stabilize and fuse the joint.

The surgery may be performed through minimally invasive techniques utilizing only small incisions to achieve the goal. The majority of patients achieve excellent stability following the surgery and experience relief from low back pain.

Bone tap

The bone is used for creating the path for the screw to engage in the bone. The bone tap has markings used to limit the depth of insertion during surgery.

Instruments used in posterior sacral fusion

Poly-axial sacral pedicle screws

The pedicle screws with the help of instruments shown above are used in sacral fusion and with the lumbar vertebra and the iliac bone to achieve stabilization at the sacroiliac and the L5-S1 joint.