Ultrasound Diagnosis of Pelvic Fractures

"The equine practitioner is likely to be faced with a horse that he/she suspects to have a pelvic fracture at some point in his or her career," began Agustin Almanza, MV, of the University of California, Davis, in his presentation on ultrasound examination for pelvic fractures at the 2003 American Association of Equine Practitioners convention. "The definitive diagnosis of a pelvic fracture in these cases can be a challenge, especially in the ambulatory setting.

"The incidence of pelvic fractures has historically been low, but recent research suggests a higher incidence," he said. "Most reports have focused on ilial wing stress fractures in Thoroughbreds.

"Clinical exam findings of crepitus (grating sound associated with fracture), pelvic asymmetry, muscle atrophy, soft tissue swelling, and abnormal rectal exam findings are useful indicators of pelvic fracture; however, these clinical findings are often absent in many horses with pelvic fractures," he cautioned.

He explained that radiographic examination can be done in the standing horse, but its availability is limited; ventrodorsal projections (shot from the belly) on a horse under general anesthesia can be done, but that is expensive and carries the risk of displacement of pelvic fragments and the risk, albeit low, of injury during recovery from anesthesia. He added that nuclear scintigraphy can be quite helpful, but it can be expensive. Both imaging modalities for this area require transport to a referral facility.

Ultrasound, however, is inexpensive and available to many practitioners.

Findings in 28 Horses

Between August 1999 and December 2002, 53 horses received ultrasonographic exams of the pelvis at UC Davis (a total of 70 hemipelves, or pelvis halves). Almanza said that superficial pelvic structures, including the tuber sacrale, tuber coxae, and tuber ischii, were examined with a 10-MHz linear transducer. The ilial wing, ilial shaft, and coxofemoral joints were evaluated with a 2.5 or 3.5-MHz sector transducer or 3.5-MHz curvilinear transducer. The ischium was evaluated transrectally using a 5-MHz rectal transducer.

The examinations found 32 fractures in 28 horses (four horses had two fractures each), located as follows:

  • Coxofemoral joint/acetabulum (12 fractures);
  • Tuber coxae (nine fractures);
  • Tuber ischii (four fractures);
  • Ilial wing (four fractures; three in Thoroughbreds in training);
  • Ischium (two fractures); and
  • Ilial shaft (one fracture).

Additionally, coxofemoral joint effusion was seen in six horses with acetabular fractures and muscle tearing/hematoma in 15 horses (54%). Transrectal ultrasound performed on 10 of the 28 horses with fractures offered information about previously undiagnosed fractures in two of them.

The affected horses were varied as to sex, age, breed, and use, and all but six were examined within 30 days of the onset of clinical signs. Those signs included:

  • Grade 3-5 on a five-point scale of lameness (average of 4);
  • Acute onset of signs (25 horses, 89%);
  • History of trauma or fall (11 horses, 39%);
  • Crepitus (11 horses, 39%);
  • Pelvic asymmetry (eight horses, 28%);
  • Muscle atrophy (eight horses, 28%);
  • Both pelvic asymmetry and atrophy (five horses, 18%); 
  • Positive rectal findings of fracture (eight horses of 19 rectally examined); and
  • Mild to intense uptake on nuclear scintigraphy (12 of 14 examined).

"Nine horses were euthanized because of a poor prognosis, persistent lameness, or severe pain," Almanza said. These included five horses with acetabular fractures, three with tuber ischii fractures, and one with an ilial body fracture. Necropsy examination of five of the horses confirmed the fracture location pinpointed via ultrasound examination.

The prognosis? Based on clinic and verbal follow-up, three horses with acetabular fractures were unchanged, six were improved but were not able to resume regular work (various fracture types), five were sound (tuber coxae and/or ilial wing fractures), Almanza reported. Five horses were lost to follow-up.

These numbers led him to conclude that acetabular fractures, the most common type in this study, carried a poor prognosis for return to athletic performance. Fractures of the tuber coxae and ilial wing hold a better prognosis.


"Ultrasound was the sole means of diagnosis (of pelvic fracture) in 13 horses and was corroborated by nuclear scintigraphy or radiography in the remaining 15 cases," Almanza said. "Ultrasound was able to provide excellent detail of the bony contours of the fracture sites and was useful in identifying associated muscle tearing and hematoma formation."

Also, he noted that standing lateral radiographs helped them diagnose fractures in three horses, although previous studies have not shown this imaging method to be useful for pelvic fractures.

He noted that a complete evaluation requires a low-frequency (2.5-3.5 MHz) transducer. Also, "The examiner needs to be aware of edge artifacts produced by vessels and fascial planes that can replicate an irregular bony contour and mimic the appearance of a fracture," he said. He added that fractures with little to no displacement might not be visible on ultrasound, so a negative ultrasound exam doesn't rule out the presence of a fracture.

Transrectal ultrasonography proved valuable in several horses, but wasn't used in all horses until later in the study, he said. This is because if they were negative on palpation, the clinicians generally didn't ask them to do a transrectal ultrasound. They later found horses that were normal on palpation, but abnormal on transrectal ultrasound. Now they perform both transrectal and transcutaneous ultrasound on all horses, regardless of transrectal findings, he said. Almanza suggested that earlier examinations might have missed fractures that might have only been detectable via transrectal ultrasound, so this type of examination is important in these cases.

"In summary, pelvic fractures should be suspected in horses with acute onset of severe hind limb lameness localized to the upper limb in performance or pasture horses of many breeds and uses," Almanza concluded.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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