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EQUINE VETERINARY EDUCATION / AE / JANUARY 2020


TABLE 1: Grading and description of the most common ultrasonographic findings of the sacroiliac joint Grade Articular margins


Modelling = change of shape of the adjacent bones (sacral and iliac wings)


1 2 3 4


Mild irregular joint margins


Moderate irregular joint margins


Marked irregular joint margins


Severe irregular joint margins


Mild modelling Moderate modelling


• marked modelling • superficial bone echogenic spots


• severe modelling • deep bone echogenic spots


Ventral sacroiliac ligament No change


Heterogeneous sacroiliac ligament


Fibrosis and/or atrophy of the ventral sacroiliac ligament


Fibrosis and/or atrophy of the ventral sacroiliac ligament


Enthesophytes Mild enthesophytes Moderate enthesophytes Marked enthesophytes Severe enthesophytes


Left * 2 1 3 1 4 3


Fig 6: Parasagittal ultrasound scan of the sacroiliac joint (cranial is to the left) of a horse (male) with a fatigue fracture of the caudal margin of the iliac wing involving the sacroiliac joint (arrow heads = fracture plane). 1: sacral wing; 2: iliac wing; 3: ventral sacroiliac ligament; 4: cranial gluteal artery and vein; *sacroiliac joint space.


Technique A good knowledge of descriptive and topographical anatomy is essential to perform an adequate transrectal ultrasound examination of the sacroiliac joints. Inadequate positioning of the probe can lead to misinterpretation or over diagnosis because of the poor orientation of the ultrasound beam. Moreover, care must be taken when manipulating the probe in the rectum in order to preserve the rectal wall and mucosa. A quiet environment is required. Sedation of nervous horses may be necessary.


Comparative imaging Radiography is a valuable technique to identify pelvic and coxofemoral fractures but it has nevertheless major limitations to assess the lumbosacroiliac area. Although the transrectal ultrasound technique has some anatomical limitations since it does not enable visualisation of the interosseous sacroiliac ligament, the internal structures of the joint and the subchondral bone, it was found adequate in the evaluation of sacroiliac injuries because of their ventral and caudal localisation. Nuclear scintigraphy is a noninvasive and useful technique to identify sacroiliac injuries and to evaluate the clinical relevance of lesions (Tucker et al. 1998; Dyson et al.


© 2017 EVJ Ltd * 3 3 2


4


Fig 7: Parasagittal ultrasound scan of the sacroiliac joint of a steeple-chaser filly showing a rupture of the ventral sacroiliac ligament and dislocation of the sacroiliac joint (cranial is to the left). 1: sacral wing; 2: iliac wing; 3: ruptured ventral sacroiliac ligament with a haematoma filling the joint space; 4: cranial gluteal artery and vein (collapsed); *enlarged sacroiliac joint space; >bone fragment.


2003a,b; Haussler 2010). In the past, nuclear scintigraphy was considered as the gold standard (Erichsen et al. 2002; Dyson et al. 2003a). Dorsal and oblique views of the pelvis are usually performed and enable a good evaluation of the sacroiliac joints (Tucker et al. 1998; Erichsen et al. 2002). A complete and precise scintigraphic assessment


of


lumbosacroiliac area requires four views of the pelvis: a dorsal horizontal symmetric view extending from L3 to the tail, a dorsocaudal symmetric view, parallel to the sacrum, extending from the iliac crest to the tuber ischiae, and two left and right dorsolateral 45° oblique views (Denoix et al. 2006). Indeed, oblique views are more useful as the camera is placed parallel to the sacroiliac joint plane. An increased radiopharmaceutical uptake (IRU) indicates active bone remodelling. In a study made on 33 horses comparing nuclear scintigraphy and transrectal ultrasonography in the


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