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EQUINE VETERINARY EDUCATION / AE / JANUARY 2020


• Ventral sacroiliac ligament rupture with dislocation of the sacroiliac joint and increased distance between sacrum and ilium;


• Traumatic or fatigue fracture of the sacral or iliac wing imaged as an interruption of the hyperechogenic bone surface of the wing and echogenic spot deep to the bone surface.


Lesion grades


Osteoarthritic lesions are most commonly found in race, sport and pleasure horses. Their severity can present huge variations between cases. In order to compare the left and right sides of the same horse, to get an idea of the severity of the findings to be correlated with the clinical or athletic manifestations, and to correlate with other imaging modalities as well as to follow the disease process, a scale of the sacroiliac joints lesions has been established, from 0 (absence of lesion) to 4 (severe bone remodelling of the sacroiliac joint margins) (Denoix 2016) (Figs 1-5; Table 1). Osteoarthritis of the sacroiliac joints is a chronic condition.


Therefore, identification of changes in the severity of lesions needs a careful and accurate ultrasonographic follow-up of the horse. Changes in the bone surface and joint margins alter the ventral sacroiliac ligament because of its anatomic location between the sacrum and ilium. Very severe bone alteration of echogenicity and shape can be seen when an iliac wing stress fracture involves the sacroiliac joint margins (Fig 6). Dislocation of the sacroiliac joint has been diagnosed after a fall resulting in a complete rupture of the ventral sacroiliac ligament (Fig 7).


4 1 * 3 2


Fig 2: Parasagittal ultrasound scan of the sacroiliac joint of a horse (female) with a grade 1 osteoarthrosis (cranial is to the left). Joint margins are mildly irregular (arrow head). 1: sacral wing; 2: iliac wing; 3: ventral sacroiliac ligament; 4: cranial gluteal artery and vein; *sacroiliac joint space.


Discussion


Indications Sacroiliac joint osteoarthritis is a common condition that should be considered in the differential diagnosis of clinical disorders attributed to the lumbosacroiliac or upper hindlimb area. Observations at physical and dynamic examination are rarely specific but asymmetry of the pelvis and muscle atrophy are indications to perform a complete ultrasound


2 1 Grade 1 4 3 Grade 2


Grade 3


Grade 4


Fig 1: Schematic drawings of the pathological appearance of the ventral aspect of the sacroiliac joint (cranial is to the left) showing the grading system from 1 to 4 according to the severity of bone modelling and remodelling of sacral and iliac wings. 1: sacral wing; 2: iliac wing; 3: ventral sacroiliac ligament; 4: cranial gluteal vein.


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