Sacroiliitis

1
Sacroiliitis

• Can be direct cause of pain in 20 of LBP
  patients (Maigne, et al Spine 1996)
• confirmed by fluoro-guidedintraarticular
  injections

2
Anatomy

• SIJ is classified as a synovial joint
• only 1/4 of superior aspect with synovium, but
  nearly all of inferior aspect is covered
• sacral cartilage is 2-3 x thicker than iliac
• anterior capsule is primarily articular but
  posterior portion is ligamentous

3
Anatomy (cont.)

• Accessory articulations can form posteriorly
  between rudimentary S2 transverse processes
• usually do not see prior to 4th decade
• incidence 8-36 (Bernard, et al Adult Spine
  1991)
• causal relationship to pain is unknown
• may be due to fibrocartilage development from
  weight-bearing stresses

4
Anatomy (cont.)

• Bony ridges begin developing after age 30 which
  continue to increase with age
• unclear if this is to increase stability of the
  joint vs. degenerative changes
• rare to develop into pure bony ossification
  rather partial intraarticular ankylosis and
  paraarticular synostosis is seen morecommonly in
  elderly

5
Anatomy (cont.)

• Ligaments
• interosseous
• forms posterior border
• strongest ligament of support
• anterior SI
• weakest ligament--thickening of joint capsule
• in close proximity to LS trunk and obturator
  nerve
• accessory ligaments
• iliolumbar 3 distinct parts that may prevent
  translation/rotation of L-5
• sacrotuberous
• sacrospinous

6
Anatomy (cont.)

• Nerve supply Not always symmetric
• unmyelinated nerve endings located in capsule and
  ligaments providing pain and thermal sensation
• capsule also contains encapsulated and
  unencapsulated nerve endings for position and
  vibration
• posterior structures innervated by lateral
  branches of posterior rami L3-S3--primarily L5-S2
• anterior structures innervated by lateral
  branches of posterior rami L2-S2--primarily L4-S1

7
Biomechanics

• Movement of the SIJ is involuntary,usually from
  muscle imbalances
• Can occur at multiple levels LE, hip,LS spine
• Motion is complex and notsingle-axis based
• estimated that up to 4 degrees of rotation can
  occur and up to 1.6 mm of translation
  (Sturesson, et al Conference on LBP San Diego
  1992)

8
Clinical

• History
• trauma very common
• also repetitive LS motion lumbar rotation or
  axial loading
• no specific correlation with exacerbating
  activities
• Exam
• may see false-positive supine SLR due to movement
  of the SIJ beyond 60 degrees
• neurological exam should be normal
• antalgic gait
• tenderness to palpation at SIJ, PSIS, or sacral
  sulcus
• may commonly see leg length discrepancy
• positive Patricks maneuver

9
Differential Diagnosis

• Fracture
• traumatic
• insufficiency stress fractures
• elderly patient with osteoporosis
• no history of trauma
• fatigue stress fractures
• usually athletes/soldiers
• caused by abnormal muscular stress on bone
• Infection
• hematogenous spread
• usually unilateral
• predisposing history

10
Differential Diagnosis (cont.)

• Seronegative spondyloarthropathies
• Ankylosing spondylitis
• Psoriatic arthritis
• RA usually not until late in course of disease
• Reiters disease
• Degenerative joint disease
• Metabolic disease
• CPPD
• gout
• ochronosis
• acromegaly

11
Differential Diagnosis (cont.)

• Primary SI tumor
• rare and usually synovial villoadenomas
• Iatrogenic instability
• via pelvic tumor resection or bone graft site
• Osteitis condensans ilii
• prevalence of 2.2
• usually self-limiting and bilateral
• primarily in multiparous women
• increased bone density on inferior iliac side
• Referred pain
• Reactive disease as sequellae of PID

12
Imaging

• X-rays
• can see erosions, bridging, joint space
  narrowing, sclerosis
• up to 25 of asymptomatic adults over 50 years
  can have abnormalities
• MRI
• can diagnose early inflammatory changes or tumors
• CT
• Bone scan
• good for fractures but less favorable for
  inflammation
• can demonstrate bilateral disease with unilateral
  symptoms

13
Treatment

• Medications NSAIDS
• Physical therapy
• modalities
• electrical stimulation/TENS
• sacral stabilization
• HEP/stretching
• Correct limb discrepancy
• Injection
• fluoro-guided vs. local
• Surgical fusion
• few figures for efficacy