History
An immature northern goshawk (Accipiter gentilis) used for falconry was evaluated following suspected trauma that occurred during a hunting expedition 3 days earlier. On physical examination, the bird would not bear weight on its right leg, and the leg appeared to be dangling loosely. The talons on the right foot were unable to grasp, and there were no signs of deep pain sensation during physical examination. There was extensive bruising over the right hip joint. No other signs of neurologic deficits were detected. General anesthesia was induced with 4% inhalant isoflurane in oxygen and maintained at 2% isoflurane, and radiographs were obtained (Figure 1).
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Ventrodorsal radiographic view of the pelvic girdle of an immature northern goshawk evaluated for inability to use its right leg following suspected trauma that occurred 3 days earlier.
Citation: Journal of the American Veterinary Medical Association 230, 8; 10.2460/javma.230.8.1147
Same ventrodorsal radiographic view as in Figure 1. Notice that the right hip joint space is increased, the articular margin of the hip joint is irregular (large arrow), and a fracture is evident in the last rib (small arrow). Notice also the gas radiolucencies in the soft tissue of the right femoral region.
Citation: Journal of the American Veterinary Medical Association 230, 8; 10.2460/javma.230.8.1147
Radiographic Findings and Interpretation
The joint space between the left femoral head and acetabulum appears normal and congruent; the margin of the left acetabulum is smooth (Figure 2). The right hip joint is widened, particularly along the cranial acetabular edge, and its margin is irregular, and the last right rib is fractured. The head of the right femur appears displaced medially, but a distinct fracture line is not visible. Severe subcutaneous emphysema is visible along the right femoral fascial planes.
Comments
Computed tomography (CT) was performed to define better the extent and severity of the findings detected on survey radiographs. Several comminuted fragments originating from the medial aspect of the right acetabulum and displaced medially are identified (Figure 3), with a complete fracture of the right ilium cranial to the acetabulum (Figure 4). The right femoral head and neck are intact. A large hypoattenuating soft tissue mass extends medial to the pelvis from the right acetabulum, likely representing a large hematoma. Given the location of the acetabular fragments, mass effect medial to the acetabulum, and physical examination findings, damage to the right ischiatic nerve was suspected.
Electromyography1 confirmed lack of ischiatic nerve function. Because the profound damage to the ischiatic nerve precluded any reasonable chance of return to normal function, the owner elected euthanasia. Necropsy revealed that most (75%) of the ischiatic nerve was severed and that there was severe damage to soft tissues around the hip joint. The right femoral head and neck were intact, but the acetabulum was fractured into several small fragments. There were also fractures of the right ilium, right fourth and eighth ribs, and left fifth rib; numerous other ribs had calluses indicating previous trauma. Extensive pulmonary, renal, thyroid, and air sac hemorrhage, consistent with acute trauma, was also detected.
When evaluating radiographic views of hip joints and the pelvic girdle for trauma, checking for symmetry is important in identifying abnormalities.2,3 Crawford et al4 found CT to be useful in dogs for evaluation of pelvic trauma for surgical planning, particularly when acetabular fractures were suspected. Computed tomography is more sensitive in the detection of small fracture fragments than radiography and, in this case, was superior to survey radiography for specific localization of numerous small acetabular fragments. Although visualization of the ischiatic nerve was not possible during CT because of its small size and similar density to the surrounding soft tissues, damage to the nerve was assumed on the basis of the proximity of the bony fragments to the location of the nerve. The fractured ilium was difficult to evaluate on survey radiographic views but was easily detected via CT.
Computed tomographic image of the same goshawk in Figure 1 at the level of the proximal portion of the right femur and hip joint. Notice that the right acetabulum is fractured into multiple fragments (arrow) and a large soft tissue attenuating mass (asterisk) is evident medial and ventral to the right acetabulum. Computed tomography was performed with 1.5-mm collimation and edge-enhancing (bone) algorithm. Window width = 1,250 Hounsfield Units (HU). Window level = 240 HU.
Citation: Journal of the American Veterinary Medical Association 230, 8; 10.2460/javma.230.8.1147
Computed tomographic image of the same goshawk as in Figure 1 at the level of the proximal portion of the right femur and hip joint, slightly cranial to the slice seen in Figure 3. The arrow indicates the fracture line in the right ilium. Notice the large soft tissue attenuating mass (asterisk) medial and ventral to the right acetabulum. Computed tomography was performed with 1.5-mm collimation and edge-enhancing (bone) algorithm. Window width = 1,250 HU. Window level = 240 HU.
Citation: Journal of the American Veterinary Medical Association 230, 8; 10.2460/javma.230.8.1147
The subcutaneous emphysema along the right femoral fascial planes may indicate air sac rupture, damage to pneumatic bones, or presence of an open wound. The latter possibility was ruled out because skin wounds were not present. In either of the 2 remaining scenarios, the trauma could have occurred during impact or indirectly by a bone fragment from the fractured acetabulum.
To the authors' knowledge, there are no reports describing ischiatic nerve damage caused by acetabular fracture in any avian species. In dogs, damage to the ischiatic nerve is generally caused by nerve entrapment and not nerve transection. Even in those cases in which the nerve is intact, outcome is generally poor and return to normal function is infrequent.5
- 1.↑
Sims MH. Clinical electrodiagnostic evaluation in exotic animal medicine. Semin Avian Exot Pet Med 1996;5:140–149.
- 2.
Smith SA, Smith BJ. Atlas of avian radiographic anatomy. Philadelphia: WB Saunders Co, 1992.
- 3.
Orosz SE, Ensley PK, Haynes CJ. Avian surgical anatomy. Philadelphia: WB Saunders Co, 1992.
- 4.↑
Crawford JT, Manley PA, Adams WM. Comparison of computed tomography, tangential view radiography, and conventional radiography in evaluation of canine pelvic trauma. Vet Radiol Ultrasound 2003;44:619–628.
- 5.↑
Chambers JN, Hardie EM. Localization and management of sciatic nerve injury due to ischial or acetabular fracture. J Am Anim Hosp Assoc 1986;22:539–544.
