Sacroiliac Joint Dysfunction



Sacroiliac Joint Dysfunction


Roberto Feliz



Despite the controversies, the sacroiliac joint (SIJ) has been identified as a potential cause of lower back pain since the early reports of Goldwaith and Osgood first reported it in 1905.1 More recently, Bernard and Kirkaldy-Willis concluded that SIJ may be a primary source of pain in 22.5% of patients with lower back pain.2 Other studies have reported that the true incidence of SIJ pain ranges between 15% and 23%.3

Many experts, however, believe that the pain generators in SIJ dysfunction rather include the surrounding soft tissues and stabilizing ligaments.4


ANATOMY AND PHYSIOLOGY

The sacrum is a wedge-shaped structure formed by five fused sacral vertebrae. The sacrum articulates superiorly with the fifth lumbar vertebra and inferiorly with the triangular-shaped coccygeal bone and laterally with the ileum. The sacrum supports the lumbar spine and helps transmit the forces from the lower extremities to the pelvis and vertebral column.5

The sacrum and the ileum articulate via the C-shaped synovial SIJ. This joint, surrounded by a fibrous capsule with an inner synovial lining, allows a 2 to 3 millimeter of glide and 2 to 3 degrees of rotation. Despite the limited motion across, the major function of the SIJ is to support the axial skeleton and stabilize the pelvic ring.6

It has been postulated that the SIJ acts as an important stress reliever in the force-motion relationships between the trunk and the lower limbs. These joints ensure that the pelvic girdle is not a solid ring of bone that could easily fracture under the great forces to which it might be subject, either from trauma or its many bipedal functions.7

In the adult, the SIJ has a short cranial and a longer caudal limb. The lower portion of the cranial limb and the caudal limb are synovial joints, whereas, the upper part of the cranial limb is more fibrous. The SIJ lies obliquely at an angle to the sagittal plane. In the standing position, the cranial, also known as the S1 part of the joint, lies mainly vertical, and its surface runs obliquely and sagittally from cranio-lateral to slightly cauda-medial. The surface of the SIJ is divided into three parts (cranial (S1), middle (S2) and caudal (S3)) or sacral elements. Of these, the S1 is the largest and the S3 part the smallest. The mean angle of the C-shape SIJ is 40 degrees at S1, 25 degrees at S2, and minus 10 degrees at S3.7

The SIJ articular surface has interdigitating symmetrical grooves and ridges. These grooves and ridges contribute to the highest coefficient of friction of any arthrodial joint. The sacrum
with its smooth keystone like bony anatomy further contributes to stability within the pelvic ring. The sacrum is wider superiorly than inferiorly; it is also wider anteriorly than posteriorly, permitting the sacrum to become “wedge” cranially and dorsally into the ilia within the pelvic ring. This anatomic structure of the sacrum in humans is adapted to resist shearing from vertical compression and anteriorly directed forces of the spine.7

The stability of the SIJ is partially provided by surrounding muscles and thick ligaments projecting from the spine, sacrum, and iliac bones. These include the iliolumbar, sacrospinous, interosseous, anterior and superior sacroiliac, and sacrotuberous ligament.

Anteriorly, the SIJ surface is covered by a thin anterior capsule made of a thin layer of hyaline cartilage on the sacral side and fibrocartilage on the iliac side. Posteriorly, the joint lacks a capsule coverage; however, the interosseous ligament forms the dorsal border of the joint space.


INNERVATION

Posteriorly, the SIJ is innervated by lateral branches of the posterior primary rami from L4 to S3. Anteriorly, the SIJ is innervated by lateral branches of the posterior primary rami from L2 to S2.8 This complex sensory innervation to the SIJ combined with anatomic variations may explain the variable referred patterns and the difficulty often encountered in diagnosis SIJ pain.4


CLINICAL PRESENTATION

The clinical presentation of SIJ dysfunction is pain in the lower back, buttock, and around the SIJ. One should carefully rule out disorders of the adjacent structures (i.e., lumbar intervertebral disks, facet joints, hip joints, muscles, and tendons/ligaments) as they can present with similar symptoms. Furthermore, due to the variable innervation patterns, patient may present with pain in the upper lumbar spine, the thigh region, the hip joints, and in some distal pain around the leg and feet.9

Disorder of the SIJ may occur after acute traumatic injury or repetitive shear and torsional forces on the SIJ. In patients with prior lumbar fusion to the sacrum, degeneration of the SIJ may occur as an adjacent segment disease.

A thorough history and complete physical examination are very important to help differentiate SIJ pathology from the mimicking differential diagnosis.

The SIJ pain tends to be worse in the morning and may be aggravated by Valsalva maneuver, truck flexion, prolong seating, or weight bearing on the affected limb. The pain improves with flexion of the affected leg and transferring weight bearing onto the non-painful leg.6


Oct 7, 2018 | Posted by in RHEUMATOLOGY | Comments Off on Sacroiliac Joint Dysfunction
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