Atypical Unilateral Sacroiliitis Secondary to Mechanical Stress Injury

Abstract

We report for the first time a case of atypical unilateral sacroiliitis secondary to mechanical stress injury. Unilateral sacroiliitis can be caused by a variety of etiologies. The first diagnosis to rule out is infection since it requires urgent treatment to avoid its serious consequences. Spondyloarthritis can be manifested by unilateral sacroiliitis in its early stage. Sacral fractures should always be looked for on the imaging modalities performed. In our case, no signs of infection or systemic disease were found. No fracture was seen on the imaging examinations and we had negative cultures on the computed tomography-guided biopsy realized. A history of mechanical stress was the only clue found suggesting the diagnosis of a probable stress related sacroiliitis. A thorough review of the literature will be provided stating the different causes of sacroiliitis described till now, with discussion of this new reported entity.

Keywords: Sacroiliitis; buttock pain; mechanical injury; sacroiliac joint; stress injury.

Figure 1

26-year-old male with right sacroiliitis secondary to mechanical stress injury a: Technique: coronal Proton Density Fat Sat weighted MR images. (3Tesla Magnet) Findings: articular synovitis (white arrow) with small subchondral bone erosions at the anterior aspect of the right sacral surface associated with a slight bone edema (curved arrow). b: Technique: coronal T1 weighted MR images. (3Tesla Magnet) Findings: small subchondral bone erosions at the anterior aspect of the right sacral surface associated with a slight bone edema (curved arrow).

Figure 2

26-year-old male with right sacroiliitis secondary to mechanical stress injury Technique: axial CT scan image performed one week after the first MRI. (single-row detector scanner). 3mm slice thickness Findings: CT-guided fine needle puncture of the right sacroiliac joint

Figure 3

26-year-old male with right sacroiliitis secondary to mechanical stress injury a–b: Technique: axial CT scan performed one month after the first MRI. (64 detectors CT Scan). 0.6 mm slice thickness. Findings: several bone erosions at the anterior aspect of the right iliac surface and small sequestra in the joint (white arrow) c: Technique: axial T1 weighted MR image performed one month after the first MRI. (3 Tesla Magnet) Findings: increased bone edema and erosions at the articular surfaces especially at the iliac side (open arrow). d: Technique: axial Proton Density Fat Sat weighted MR image performed one month after the first MRI. (3Tesla Magnet) Findings: increased bone edema and erosions at the articular surfaces especially at the iliac side (open arrow). e–f: Technique: axial T1 Fat Sat + contrast weighted MR image performed one month after the first MRI. (3 Tesla Magnet) Findings: enhanced bone edema of the articular surfaces especially at the iliac side (open arrow).

Figure 4

26-year-old male with right sacroiliitis secondary to mechanical stress injury Technique: axial CT scan image performed one month after the first MRI. (64 detectors CT scan). 3mm slice thickness Findings: CT-guided biopsy of the right sacroiliac joint.

Figure 5

26-year-old male with right sacroiliitis secondary to mechanical stress injury a–b: Technique: coronal Proton Density Fat Sat weighted MR images performed four months after the previous MRI. (3 Tesla Magnet) Findings: complete regression of bone edema at both articular surfaces of the right sacroiliac joint, and resolution of the synovitis. c: Technique: coronal T1 weighted MR image performed four months after the previous MRI Findings: complete regression of bone edema and erosions at both articular surfaces of the right sacroiliac joint, with fatty replacement of bone marrow edema (open arrow) d: Technique: Coronal Proton Density Fat Sat weighted MR image performed 4 years later. (3 Tesla magnet). Findings: same findings as Fig. 4.a–b. e–f: Technique: Coronal T1 weighted MR images performed 4 years later Findings: same findings as Fig. 4.c with fatty replacement of bone marrow edema of both articular surfaces, in addition to mild osteosclerosis of the right iliac articular surface (open arrow) with a normal left sacroiliac joint (white arrow).