34th Annual Scientific Meeting proceedings

Acute trauma to the pelvis may include fractures, muscle trauma and luxation/subluxation of the coxofemoral and sacroiliac joint. The clinical presentation of pelvic fractures varies. Horses with fractures following a fall can have any degree of lameness from subtle to non-weight bearing lameness or recumbent horse. Stress fractures may only show lameness in the acute phase and only stiffness or subtle lameness later. A thorough clinical examination will guide the clinician to the region of interest, but diagnostic imaging will often be needed to confirm or establish the final diagnosis.

Ultrasonography
Ultrasonography of the pelvis is in most cases readily available but dependent on the operator's experience. With a percutaneous approach muscle, soft tissues, bone contours and joint margins (the shaft and wing of the ileum, tuber coxae and the tuber ischii, the dorsolateral margin of the coxofemoral joint, dorsal aspects of the lumbar and sacral vertebrae) can be imaged and fractures and joint luxations identified. Depending on the size of the horse, a transrectal approach can be used to image the pubis, the ileal shaft, the ventral aspect of the sacrum and caudal lumbar spine. (1-5)

Radiography
Radiography of the pelvis is challenging in large adult horses and requires long exposure times and causes significant soft tissue scatter. Care should be taken to protect staff and handlers from radiation.

Ventrodorsal projections can be obtained in the anesthetized horse. To avoid the risk of anesthesia and recovery, standing techniques have been developed (5,7). Feasibility and quality of the images depend on the conformation, the size and the temperament of the horse. True lateral-lateral projections are not possible, but tangential views (dorsomedial-ventrolateral or dorsolateral-ventrolateral) of the ileal shaft and coxofemoral joint and tuber coxae may be obtained (8-9).

Radiography may detect displaced and comminuted fractures, fragments and marked callus formation related to the ileal shaft, pubis, and coxofemoral joint. Ultrasonography is superior to radiography in diagnosing ileal wing fractures.

Scintigraphy
Bone phase gamma scintigraphy has excellent sensitivity and specificity for detecting pelvic fractures. Scintigraphy is most useful in fractures where no displacement of the fracture has occurred, particularly in ileal stress fractures in racehorses. Scintigraphy does not give an anatomical image, so other imaging techniques should be used to describe the involvement of exact structures, fracture configuration, and displacement. (2,10,11)

Computed Tomography (CT)
CT is superior to other imaging techniques to detect bone lesions; CT offers cross-sectional images with anatomical detail in all three planes.

CT with a standard bore aperture of 70cm has been used to detect and diagnose pelvic lesions and fractures in foals (12) and yearlings (13,14). CT of the pelvis in large adult horses is possible using a large bore scanner with an aperture of 85cm or greater (15,16,17).

The CT examination is performed in dorsal recumbency under general anaesthesia. At the author’s hospital intravenous anaesthesia is used (17). With an experienced team the examination of the pelvis is easily done even in large horses. In most cases the procedure time from of induction of anaesthesia to placement in recovery will be done in less than 20 minutes, usually with legs extended for less than 10 minutes (17).

With increasing size and weight of the horse image quality is reduced and with increasing artefacts (15,17), but the technique will give diagnostic images even in large horses and detect major pathological changes like fractures, fragments and luxation (15,16,17).

General anaesthesia of cases with suspected pelvic fractures does expose the patient for a risk of exacerbating the lesion in recovery. This is often a concern of colleagues, referral veterinarians and clients. A thorough discussion with owner and involved veterinarians about risks and the advantages of the examination should be undertaken before the procedure. In case of suspicion of severe pathology with poor prognosis, the owner should ideally have come to terms with possible euthanasia during the procedure under general anaesthesia, so the horse does not need to go through a painful recovery unnecessarily.

With careful case selection the risks of general anaesthesia may not be as great as initially perceived. In one study of 57 horses with pelvic fractures that underwent radiography under general anaesthesia and was recovered afterwards, only one horse had serious exacerbation of the signs (6).

References

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