EQUINE VETERINARY EDUCATION Equine vet. Educ. (2020) 32 (1) 33-38 doi: 10.1111/eve.12858
Original Article
Transrectal ultrasonographic examination of the sacroiliac joints of the horse: Abnormal findings and lesions
A. Tallaj* , V. Coudry and J.-M. Denoix INRA USC BPLC 957, ENVA-UPEC, CIRALE, Goustranville, France. *Corresponding author email:
amelie.tallaj@vet-alfort.fr
Keywords: horse; ultrasonography; pelvis; sacroiliac joint; osteoarthritis
Summary Transrectal ultrasonography is a useful technique for the assessment of sacroiliac osteoarthrosis because of the ventral localisation of lesions. Comparison between the right and left side is essential. Due to the deep localisation of the sacroiliac joints, other imaging modalities have limitations for diagnosing osteoarthrosis. A grading system from 1 to 4 is suggested in order to classify the severity of lesions based on the shape of the articular margins and architecture of the
ventral sacroiliac ligament. Abnormal ultrasonographic findings should be correlated with clinical manifestations.
Introduction and indications Sacroiliac pain in horses is a common cause of poor performance and lack of power in the hindlimbs (Jeffcott et al. 1985; Denoix 1998; Dyson and Murray 2003). Diagnostic analgesic techniques have been described (Haussler 2010) but their use is limited in routine practice because of a lack of specificity and sensitivity (Dyson and Murray 2003; Denoix 2016). Therefore, localisation of the source of pain remains challenging (Denoix 1998). In the last two decades, exploration of the pelvis has improved with imaging techniques and a better knowledge of sacroiliac injuries has been gained. Transrectal ultrasonography is a useful technique to
evaluate the sacroiliac joints considering the ventral localisation of osteoarthritic lesions (Jeffcott et al. 1985; Dalin and Jeffcott 1986a; Haussler 2004; Denoix 2016). A clear evaluation of soft tissues abnormalities and abnormalities of the bone surface can be achieved with this technique (Denoix 1999; Bergman et al. 2013). Moreover, it is widely available and affordable in field practice and reliable information can be obtained with a minimum of training and practice. Therefore, transrectal ultrasonographic examination of the lumbosacroiliac area can be included in the routine approach to diagnose the cause of low back or sacroiliac pain (Denoix et al. 2006, 2007). In our centre, it is performed systematically in the context of a locomotor check-up of sport and racehorses and/or when back pain is present (Denoix et al. 2006, 2007). It is also indicated whenever an injury is suspected in sacroiliac area because of: • Abnormal conformation of the pelvis: pelvic asymmetry and/or atrophy of the gluteus medius muscle; nevertheless, a lot of horses affected with sacroiliac injuries do not present any atrophy (Denoix et al. 2005; Denoix and Coudry 2005);
• Manifestations at physical examination: pain on palpation and pressure on the sacroiliac area; racing trotters are commonly more sensitive than other horses over the
lumbosacroiliac area (Denoix 2016), and can demonstrate marked sinking (flexion) of the hindlimbs when putting pressure over the tuber sacrale (Denoix and Coudry 2005);
• History of trauma to the pelvis, like a fall: an acute pelvic fracture or a luxation may be present;
• Clinical features affecting all disciplines including: lack of propulsion, poor action and back stiffness (Tucker et al. 1998; Erichsen et al. 2002; Dyson and Murray 2003; Haussler 2004; Denoix et al. 2005; Denoix and Coudry 2005; Engeli et al. 2006); mild chronic hindlimb lameness may be present;
• Negative responses to diagnostic analgesia such as nerve blocks or intrasynovial blocks of the hindlimb, ruling out a lesion on the limb;
• Scintigraphic findings in the pelvis: detection of increased radiopharmaceutical uptake indicating active bone remodelling over the sacroiliac area. In a study made on 33 horses comparing nuclear scintigraphy and transrectal ultrasonography in the detection of sacroiliac abnormalities, Coudry et al. showed a good correlation (77%–51/66) between the two techniques (Coudry et al. 2006). Radiation capture from the sacroiliac joint is also limited by the thick gluteus medius muscle which causes attenuation.
The technique and normal images of the sacroiliac joints
have already been described (Tallaj et al. 2019). Therefore, the aims of this paper are to present the abnormal findings and the types of lesions of the sacroiliac joint which can be detected with ultrasonography, as well as a grading system for characterising the severity of osteoarthritic lesions.
Abnormal findings and lesion types
Abnormal ultrasonographic findings encountered at the ventral aspect of the sacroiliac joint include mainly (Denoix 1998; Denoix and Coudry 2005; Denoix et al. 2006): • Marginal remodelling of the periarticular borders and/or periarticular osteophytes of the sacral and/or ilium wings (caudal border of the auricular surface of the sacrum and/or caudal auricular margin of the ilium);
• Periarticular bony proliferation with modelling of the sacral or iliac wing often associated with a reduction of the sacroiliac joint space;
• Ventral sacroiliac ligament desmopathy with thickening and reduction and/or alteration of echogenicity of the ventral sacroiliac ligament;
• Ventral sacroiliac ligament enthesopathy with bone remodelling at the attachment on the bone surface, especially at the iliac insertion;
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