Friday, December 12, 2008

Cervical spine injury: Tiger attack

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Cervical Spine Injury: Tiger Attack

By Meredith Anderson, MD; Philip Utter, MD; Jan Szatkowski, MD; Todd Patrick, MD; William Duncan, MD; Norman Turner, MD; Mark Dekutoski, MD
ORTHOPEDICS 2008; 31:1

December 2008

Severe soft tissue damage related to open cervical spine fractures caused by animal attacks can impair the vascularization of bone and surrounding tissues. In addition to the primary stabilization, open wound treatment with local or free muscle flaps becomes an essential part of therapy as well as the use of autogenous cancellous bone. Furthermore, animal bites from large animals are associated with and are prone to infection in 10% to 20% of cases.1 Most infections are polymicrobial, with Pasteurella multicida being the most common isolate.2,3 Other aerobic bacteria include Staphyloccocus and Streptococcus viridans.4 Animal bites also mandate consideration of tetanus and rabies prophylaxis. The decision to administer postexposure rabies prophylaxis is dependent on the type of animal that is involved, whether the exposure was provoked, the local epidemiology of rabies, and the availability of the animal for observation or testing.

Assessment of patients with cervical spine injury from animal attacks requires knowledge of possible associated injuries. Evaluation of these patients involves assessment of plain radiographs and computed tomography (CT) for evaluation of the cervical spine for bony injury. Furthermore, computed angiography is advantageous to noninvasively evaluate carotid or vertebral artery injury at the same setting in patients with deep cervical puncture wounds.

Magnetic resonance imaging (MRI) is logistically difficult in trauma but provides the best assessment of soft tissue abnormalities such as the disk, ligament, and spinal cord to compliment the bony pathology provided by CT. Magnetic response angiography also provides an excellent assessment of dissection and mural hematomas. Many safety consideration arise when attempting to use MRI in trauma due to the extensive monitoring and intensive support required in these situations.5

Surgical treatment of unstable cervical spine fractures with lateral mass screw and rod fixation has been reported in the literature to have superior biomechanical properties compared to anterior and posterior instrumentation and fusion.3,6 In recent clinical studies, the use of lateral mass screws for traumatic injury of the cervical spine has been associated with excellent maintenance of alignment and minimal complications.7

Although reports of tiger attacks in the United States are rare, this article presents a case of a young woman who was violently attacked by a Siberian tiger and sustained penetrating trauma to the neck, cervical spine, and bilateral lower extremities. It also presents both diagnostic and therapeutic management of patients who may present with similar injuries.

Case Report
A 36-year-old woman presented following an attack by 2 large tigers while cleaning their cage at an exotic animal farm. The initial attack began after the tiger grabbed the woman’s legs between its jaws. A second tiger, in an attempt to rescue the attendant, grabbed the woman by the neck and carried her to the edge of the cage and left her body at the front gate.

Figure 1: Anterior neck (A), posterior neck (B), and left leg (C) wounds demonstrating significant soft tissue defect of the lateral compartment.

The patient’s neck was immobilized in a rigid cervical collar on presentation. Primary survey was conducted. She remained conscious and was able to answer question appropriately with a clear airway. On examination, she reported tenderness to cervical spine palpation. She remained immobilized in a rigid cervical collar. Three transverse lacerations located on the left anterior neck, posterior neck, and thorax were present with active bleeding (Figures 1A, B). Extensive bone and soft tissue loss was present on both lower extremities (Figure 1C). Concern of the patient’s airway led to bronchoscopic intubation.

On neurological examination, the patient had no evidence of spinal cord injury. Strength and sensation in the upper extremities were normal. The left lower extremity had decreased sensation in the superficial peroneal nerve distribution. The patient had mild ptosis of the right eye, presumably from interruption of the cervical sympathetic chain. Due to soft tissue injury, she had weakness with dorsiflexion and foot eversion in both lower extremities. The lower extremities had a palpable pulse in the posterior tibial and dorsalis pedis arteries.


Figure 2: Lateral c-spine radiograph: single portable lateral view of the upper 6 cervical vertebrae shows considerable prevertebral soft tissue swelling. There is bony deformity at the C2 and C3 levels, particularly in the posterior elements and within the body of C3 (A). Cervical spine axial CT scan: comminuted fracture of the C3 vertebral body which extends into the left posterior elements. A major fragment of the left C3 posterior elements is displaced posteriorly such that the left C2/C3 facet is locked, but the alignment of the cervical spine is essentially normal. The spinal canal is widely patent with air within the extradural portion of the spinal canal (B). Cervical spine coronal CT scan: comminuted fracture of the C2 and C3 vertebral body (C). Axial CT angiography: occlusion of the left vertebral artery (arrow; D). No evidence of extravasation.

Cross-table lateral cervical radiographs revealed a comminuted fracture of the body of C2 and C3 (Figure 2A). Computed axial tomography of the chest, cervical spine, abdomen, and pelvis revealed comminuted fractures of the body of C2/C3 with no compromise to the spinal canal (Figures 2B, 2C). Computed tomography angiography revealed a 4-cm occlusion of the left vertebral artery without evidence of active extravasation (Figure 2D). No flow was visualized within the left jugular vein below the skull base secondary to thrombosis.

The patient underwent immediate exploration of the anterior neck wound, and the lower extremity wounds were thoroughly irrigated and debrided. Cultures of soft tissue specimens grew only coagulase negative Staphylococcus from the anterior neck wound. Orthopedic infectious disease consultation recommended broad spectrum antibiotic coverage.

After review of the radiographs, consideration of the wound colonization, and discussion with infectious disease service, the decision was made by the orthopedic spine service to stabilize the patient’s cervical spine. A posterior instrumented fusion from C2 to C4 with 5 lateral mass screws was used (Figure 3A). Only decortication and local bone graft was used due to the contamination of the woundIntraoperatively, a cerebrospinal fluid leak was detected from the initial bite wound. In addition, because of the possibility of rabies infestation from the tiger bite, a rabies immunoglobin was locally applied to the open wounds and the surgical wound.

Postoperatively, the patient was placed in a cervical collar and continued on intravenous antibiotics consisting of zosyn and fluconazole for 2 months. She was deemed a poor candidate for anticoagulation treatment of the left vertebral artery occlusion. An inferior vena cava filter was placed due to her immobilization needs from the lower extremity wounds, which required multiple debridements and a subsequent free latissimus flap by plastic surgery.


Figure 3: Postoperative cervical spine radiograph: posterior fusion C2, C3, and C4 with pedicle screw and rod fixation (A). Cervical CT spine (axial) demonstrating a pseudomeningocele anterior to C3 (B). Cervical CT scan (coronal) 1-year postoperatively: bony fusion of the posterior elements of C2 to C4 (C).

Three months postoperatively she presented with difficulty swallowing, fever, and headache. A lumbar tap ruled out meningitis. A cervical angiography performed secondary to a bloody lumbar tap revealed retrograde flow down the left vertebral artery secondary to the vertebral artery occlusion at the C4 level with collateral reconstitution distally from the deep cervical artery. A cervical CT scan revealed an anterior pseudomeningocele that was aspirated with ultrasound guidance (Figure 3B). This was treated conservatively with a course of intravenous antibiotics and found to remain stable with time with gradual improvement in symptoms. The pseudomeningocele was believed to come from the previous cerebrospinal fluid leak at the time of initial injury.

Computed tomography scans of the cervical spine at 3-month follow-up demonstrated evidence of fusion and the patient was allowed to remove her cervical collar. She was allowed to return to work on a part-time basis at 6 months with a lifting restriction of 10 lbs. At 1-year follow-up, her cervical CT scan demonstrated bony fusion from C2-C4 (Figure 3C).

Discussion
Penetrating neck trauma due to tiger or animal bites poses a significant diagnostic and therapeutic challenge. These severe injuries to the neck region require diagnostic imaging to exclude injury to the carotid and vertebral artery injury.8 Conventional angiography has traditionally been considered the gold standard for evaluation of vascular injuries. The use of angiography for stable patients with penetrating neck trauma has been questioned because of its invasive nature. In recent years, there has been a renewed interest in the use of CT. This is a low-risk, noninvasive technique that is less expensive than conventional angiography. Computed tomography also has the benefit of providing information regarding the cervical spine and the aerodigestive tract.8 Prospective studies comparing CT with the gold standard of conventional arteriography have been performed. Reported sensitivity and specificity for CT was 90% and 100%; positive predictive value was 100%, and negative predictive value was 98%.8-10

Regarding surgical management for cervical trauma for injuries localized to C2 and C3, many surgeons have advocated the use of pedicle screw in C2 and C7 and lateral mass screw in the C3-C6 vertebra to reduce risk of neurovascular injury.7 Given the small size of the lateral masses in this location, there is concern regarding bony purchase. In a study by Jones et al,11 a lower load-to-failure was found for lateral mass screws compared to pedicle screws. In our patient, a posterior approach with lateral mass screw fixation was used from C2-C4. Posterior screws on the side of the uninjured artery were used despite the risk of iatrogenic injury to the vertebral artery on the uninjured side was performed because it was felt to be necessary to provide cervical stability. At 1-year follow-up, she maintained excellent alignment and bony fusion without any associated neurological complications. The patient will continue to receive close follow-up due a report published by Papadoupoulos et al12 in 1999 that describes late neurological complications due to a cord syrinx and cord tethering in a man that had bitten by a Bengal tiger in a safari park.

In addition to the primary stabilization, open wound treatment from animal bites is a potential risk for postoperative complications. Furthermore, animal bites from large animals are associated with and are prone to infection in 10% to 20% of cases.1 Most infections are polymicrobial; however, as with bite wounds from domestic cats, Pasteurella multicida is the most common isolate.2,13,14 In anticipation of a polymicrobial infection with unusual organisms, antibiotic coverage with ampicillin-sulbactam is recommended for empiric therapy.13 First generation cephalosporins, especially oral agents, are not recommended for bite wounds infected by Pasteurella multicida.15 In a previous case report published in 2002, where a 7-year-old girl was bitten by a white Siberian tiger, intraoperative cultures of the wound grew Pasteurella multicida, which fortunately was susceptible to the empiric antibiotics the patient was receiving.3 In our case, Pasteurella multicida was not isolated in the infected wound, but only coagulase negative Staphylococcus.

Animal bites also mandate consideration of tetanus and rabies prophylaxis. According to the Center for Disease Control and Prevention (CDC), the decision to administer postexposure rabies prophylaxis is dependent on the type of animal that is involved, whether the exposure was provoked, the local epidemiology of rabies, and the availability of the animal for observation or testing.16 In the previous case report published in 2002, the tiger involved in the incident was recovered and euthanized in accordance with public health recommendations and state law within 3 days of the injury and was found to be negative for rabies.13 In our case, rabies virus was considered and the immunization of the tiger was unknown to the treating physicians and the rightful owners. The owners were unwilling to provide the animal for testing purposes; therefore, the surgical team felt necessary to administer the appropriate precautions. Both active and passive vaccination was given, which consisted of rabies immunoglobins and rabies inactive vaccine.

Tigers are capable of producing serious vascular, soft tissue, and bony injuries. Polymicrobial infections with unusual organisms, especially Pasteurella multicida and rabies virus, should be anticipated and appropriate antibiotics and consultation with the guideline set by the CDC should be followed. We recommend a multidisciplinary approach to organize the proper diagnostic imaging and treatment for these patients. Furthermore, lateral mass screw fixation for cervical spine trauma is an excellent choice of fixation and is capable of sustaining adequate alignment and obtaining a bony fusion.

References
Woolfrey BF, Quall CO, Lally RT. Pasteurella multocida in an infected tiger bite. Arch Pathol Lab Med. 1985; 109(8):744-746.
Burdge DR, Scheifele D, Speert DP. Serious Pasteurella multocida infections from lion and tiger bites. JAMA. 1985; (253):3296-3297.
Do Koh Y, Lim TH, Won You J, et al. A biomechanical comparison of modern anterior and posterior plate fixation of the cervical spine. Spine. 2001; (26):15-21.
Kizer KW. Pasteurella multocida infection from a cougar bite. A review of cougar attacks. West J Med. 1989; 150(1):87-90.
Bagley LJ. Imaging of spinal trauma. Radiol Clin North Am. 2006; 44(1):1-12, vii.
Papagelopoulos PJ, Currier BL, Neale PG, et al. Biomechanical evaluation of posterior screw fixation in cadaveric cervical spines. Clin Orthop Relat Res. 2003; (411):13-24.
Pateder DB, Carbone JJ. Lateral mass screw fixation for cervical spine trauma: associated complications and efficacy in maintaining alignment. Spine J. 2006; 6(1):40-43.
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Munera F, Soto JA, Palacio D, et al. Diagnosis of arterial injuries caused by penetrating trauma to the neck: comparison of helical CT angiography and conventional angiography. Radiology. 2000; 216(2):356-362.
Jones EL, Heller JG, Silcox DH, Hutton WC. Cervical pedicle screws versus lateral mass screws. Anatomic feasibility and biomechanical comparison. Spine. 1997; 22(9):977-982.
Papadopoulos MC, Tubridy N, Wren D, et al. Neurological symptoms 27 years after tiger bite. J J R Soc Med. 1999; 92(6):303-304.
Capitini CM, Herrero IA, Patel R, et al. Wound infection with Neisseria weaveri and a novel subspecies of pasteurella multocida in a child who sustained a tiger bite. Clin Infect Dis. 2002; 34(12):E74-E76.
Talan DA, Citron DM, Abrahamian FM, et al. Bacteriologic analysis of infected dog and cat bites. Emergency Medicine Animal Bite Infection Study Group. N Engl J Med. 1999; 340(2):85-92.
Isotalo PA, Edgar D, Toye B. Polymicrobial tenosynovitis with Pasteurella multocida and other gram negative bacilli after a Siberian tiger bite. J Clin Pathol. 2000; 53(11):87-872.
Rose VL: CDC issues revised guidelines for the prevention of human rabies. Am Fam Physician. 1999; 59(7):2007-2008, 2013-2014.

Authors
Drs Anderson, Utter, Szatkowski, Patrick, Duncan, Turner, and Dekutoski are from the Mayo Clinic, Rochester, Minnesota.

Drs Anderson, Utter, Szatkowski, Patrick, Duncan, Turner, and Dekutoski have no relevant financial relationships to disclose.

Correspondence should be addressed to: Mark Dekutoski, MD, Mayo Clinic, 200 1st St SW, Rochester, MN 55905.

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