Sacroiliitis

                                     Dr. KS Dhillon

Introduction

Sacroiliitis is an inflammation of the sacroiliac joint (SI). It usually produces pain in the buttock and low back. Often sacroiliitis is a diagnosis of exclusion. The sacroiliac joint (SI) is one of the largest joints in the body. It connects the ilium to the sacrum. Sacroiliitis is difficult to diagnose because its symptoms are similar to many other common sources of low back pain. Sacroiliitis is often overlooked as a source of back or buttock pain. Pain in sacroiliitis is often due to chronic degenerative causes. Sacroiliitis can also be secondary to rheumatic, infectious, drug-related, or oncologic sources. Some of the non-degenerative conditions that can lead to sacroiliitis are psoriatic arthropathy, Bechet disease, ankylosing spondylitis, hyperparathyroidism, and various pyogenic sources [1-3]. 

Etiology

There are several conditions that can cause inflammation of the SI joint.  Degeneration of the joint can produce osteoarthritis of the SI joints. Spondyloarthropathies such as psoriatic arthropathy, Bechet disease, and ankylosing spondylitis, can cause significant inflammation of the joint. Pregnancy is another cause of inflammation due to the hormone relaxin leading to the relaxation, stretching, and possible widening of the SI joints. The increased body weight during pregnancy also causes extra mechanical stress on the joint, leading to further wear and tear. Trauma can also cause direct or indirect stress and damage to the SI joints. The most frequent cause of acute sacroiliitis is infection of the joints. Pain can originate from the synovial SI joint but can also come from the posterior sacral ligaments [4,5].

Epidemiology

Reports on the prevalence of sacroiliac pain differ widely. Some studies have reported that the prevalence is between 10% to 25% in patients with low back pain. In patients with a confirmed diagnosis, the presentation of pain is in the ipsilateral buttock in 94% of the cases and in the lower lumbar area in 74% of the cases. In about 50% of cases, the pain radiates to the lower extremity, in 6% to the upper lumbar area, in 4% percent to the groin, and in 2% percent to the lower abdomen [6,7].

Pathophysiology

The sacrum articulates with the ilium at the SI joint (fig 1). The joint helps to distribute body weight to the pelvis. The capsule of the SI joint is relatively thin and it often develops defects that enable fluid, such as joint effusion or pus, to leak out onto the surrounding tissues. 

The common distribution of pain is along the L4-L5 dermatomes, but the distribution can be from as high as L2 to as low as S3. The differential diagnosis includes leg-length discrepancies, weakness of one limb, weakness of the gluteal muscles, tight surrounding muscle structures, or hip osteoarthritis [8].

Fig 1

History and Physical Examination

Patients with sacroiliitis usually present with low back pain. The pain can be in one or both buttocks, hip region, thigh region, or even more distally. Sometimes patients report that their pain is worse after sitting for prolonged periods or with rotational movements. The characterization of pain varies widely. It is commonly described as sharp and stabbing in nature but can also be described as dull and achy in nature. The patient has to be asked about a history of inflammatory disorders. History of systemic symptoms such as fevers, chills, night sweats, and weight loss should be obtained. These systemic symptoms are indicative of a systemic illness.

Inspection may reveal pelvic asymmetry. Limb length measurement can rule out a leg-length inequality. The spine should be inspected for rotational abnormalities or abnormal curvatures. Usually the range of motion, neurologic, and strength testing are unremarkable. The patient may experience pain during some of these tests.

There are special provocative tests that can be very helpful in reproducing the patient’s pain:

• “Fortin finger test”- Have the patient use one finger to localize their pain. A positive test is when the patient twice identifies the painful region as within 1 cm of inferomedial to the posterior superior iliac spine.

• FABER test- reproduction of pain after hip flexion, abduction, and external rotation.

• Sacral distraction test- Pain reproduction on applying pressure to the anterior superior iliac spine.

• Iliac compression test- pain reproduction on applying pressure downward on the superior aspect of the iliac crest.

• Gaenslen test- reproduction of pain on hyperextension of the hip on the affected side. The patient flexes the hip on the unaffected side and then dangles the affected leg off the examining table. Pressure is then directed downward on the leg to extend the hip further.

• Thigh thrust test- reproduction of pain on flexing the hip and applying a posterior shearing force on the SI joint.

• Sacral thrust test- reproduction of pain with the patient prone and applying an anterior pressure through the sacrum.

The likelihood of SI joint pain increases as the number of positive provocative tests increases.

Evaluation

If an inflammatory condition is suspected to be the cause of SI joint pain the following tests should be ordered: complete blood cell count (FBC), erythrocyte sedimentation rate (ESR), C-reactive protein, antinuclear antibody, human leukocyte antigen (HLA-B27), and rheumatoid factor. 

Common laboratory findings in patients with aseptic sacroiliitis include:

• WBC count - usually normal 

• ESR - elevated

• CRP - elevated

• HLA-B27 - About 50% to 92%% of patients with ankylosing spondylitis will be HLA-B27 positive

• Rheumatoid Factor (RF) - Negative in patients with true ankylosing spondylitis

If trauma or inflammatory causes are not suspected, then x rays are not needed. If x-rays are done an anteroposterior view of the pelvis/lumbar spine should be ordered. The x-rays can show sclerosis or other degenerative changes in the SI joint. Specific sacroiliac views can be taken at a 25 to 30-degree angle to help identify joint widening or sclerotic changes at joint margins. A CT scan can also show sclerotic changes and reveal reactive spurring or subluxation. An MRI may show subchondral edema, which is the earliest sign of sacroiliitis. A PET scan can be ordered if bony metastatic disease is suspected.

The most useful test for the diagnosis of sacroiliitis is SI joint injection with local anesthetics and steroids. If the injection relieves the pain, it is highly likely that the inflammation at this site was the cause of the pain. 

Treatment 

Since hypermobility can cause pain physical therapy can be very useful. Physical therapy can help to strengthen lumbopelvic musculature and stabilize the joint. If the pain is due to lack of mobility, then physical therapy can help increase mobility of the SI joint.  In the acute phase, NSAIDs are useful but they become less effective in the chronic phase. Intra-articular anesthetic/steroid injections can be performed under image guidance. 

If NSAIDs and injections do not work radiofrequency ablation can be tried. Surgery is usually reserved as a last resort for patients with chronic pain. SI joint fusion can be carried with SI screws [9-11].

If there is infection intravenous antibiotics can be given. If there is an abscess surgery would be required.

Differential Diagnosis

The differential diagnosis would include:

• Ankylosing spondylitis

• Hip tendonitis/fracture

• Piriformis syndrome

• Sacroiliac joint infection

• Trochanteric bursitis

Outcomes

The outcome in majority of patients with sacroiliitis is excellent. However, the recovery can take about 2 to 4 weeks. Some publications report a recurrence rate of over 30% [12,13].

References

1. Slobodin G, Hussein H, Rosner I, Eshed I. Sacroiliitis - early diagnosis is key. J Inflamm Res. 2018;11:339-344. 

2. Chahal BS, Kwan ALC, Dhillon SS, Olubaniyi BO, Jhiangri GS, Neilson MM, Lambert RGW. Radiation Exposure to the Sacroiliac Joint From Low-Dose CT Compared With Radiography. AJR Am J Roentgenol. 2018 Nov;211(5):1058-1062. [PubMed]

3. Gutierrez M, Rodriguez S, Soto-Fajardo C, Santos-Moreno P, Sandoval H, Bertolazzi C, Pineda C. Ultrasound of sacroiliac joints in spondyloarthritis: a systematic review. Rheumatol Int. 2018 Oct;38(10):1791-1805.

4. Kocak O, Kocak AY, Sanal B, Kulan G. Bilateral Sacroiliitis Confirmed with Magnetic Resonance Imaging during Isotretinoin Treatment: Assessment of 11 Patients and a Review of the Literature. Acta Dermatovenerol Croat. 2017 Oct;25(3):228-233.

5. Pandita A, Madhuripan N, Hurtado RM, Dhamoon A. Back pain and oedematous Schmorl node: a diagnostic dilemma. BMJ Case Rep. 2017 May 22;2017.

6. Protopopov M, Poddubnyy D. Radiographic progression in non-radiographic axial spondyloarthritis. Expert Rev Clin Immunol. 2018 Jun;14(6):525-533.

7. Ziade NR. HLA B27 antigen in Middle Eastern and Arab countries: systematic review of the strength of association with axial spondyloarthritis and methodological gaps. BMC Musculoskelet Disord. 2017 Jun 29;18(1):280.

8. Poddubnyy D, Listing J, Haibel H, Knüppel S, Rudwaleit M, Sieper J. Functional relevance of radiographic spinal progression in axial spondyloarthritis: results from the German spondyloarthritis Inception Cohort. Rheumatology (Oxford). 2018 Apr 01;57(4):703-711.

9. Expert Panel on Musculoskeletal Imaging: Bernard SA, Kransdorf MJ, Beaman FD, Adler RS, Amini B, Appel M, Arnold E, Cassidy RC, Greenspan BS, Lee KS, Tuite MJ, Walker EA, Ward RJ, Wessell DE, Weissman BN. ACR Appropriateness Criteria® Chronic Back Pain Suspected Sacroiliitis-Spondyloarthropathy. J Am Coll Radiol. 2017 May;14(5S): S62-S70.

10. Nash P, Lubrano E, Cauli A, Taylor WJ, Olivieri I, Gladman DD. Updated guidelines for the management of axial disease in psoriatic arthritis. J Rheumatol. 2014 Nov;41(11):2286-9.

11. van der Heijde D, Ramiro S, Landewé R, Baraliakos X, Van den Bosch F, Sepriano A, Regel A, Ciurea A, Dagfinrud H, Dougados M, van Gaalen F, Géher P, van der Horst-Bruinsma I, Inman RD, Jongkees M, Kiltz U, Kvien TK, Machado PM, Marzo-Ortega H, Molto A, Navarro-Compàn V, Ozgocmen S, Pimentel-Santos FM, Reveille J, Rudwaleit M, Sieper J, Sampaio-Barros P, Wiek D, Braun J. 2016 update of the ASAS-EULAR management recommendations for axial spondyloarthritis. Ann Rheum Dis. 2017 Jun;76(6):978-991.

12. Darr E, Meyer SC, Whang PG, Kovalsky D, Frank C, Lockstadt H, Limoni R, Redmond A, Ploska P, Oh MY, Cher D, Chowdhary A. Long-term prospective outcomes after minimally invasive trans-iliac sacroiliac joint fusion using triangular titanium implants. Med Devices (Auckl). 2018;11:113-121. 

13. van Lunteren M, Ez-Zaitouni Z, de Koning A, Dagfinrud H, Ramonda R, Jacobsson L, Landewé R, van der Heijde D, van Gaalen FA. In Early Axial Spondyloarthritis, Increasing Disease Activity Is Associated with Worsening of Health-related Quality of Life over Time. J Rheumatol. 2018 Jun;45(6):779-784.