Introduction
Birds possess several anatomic and physiologic features that can present unique challenges to the practitioner when stabilizing an avian fracture patient. This discussion is a review of the features of birds affecting fracture management, and appropriate treatments and diagnostics for initial stabilization of the avian fracture patient.
Unique Avian Musculoskeletal Features
The pectoral girdle consists of the coracoid, clavicle, and humerus, which together form the triosseal canal. The tendon of the supracoracoideus muscle travels through the triosseal canal to work as a pulley for wing elevation.8
The humerus and femur (and in some species, ulna), are pneumatized.8
Other anatomic differences such as a sternal plate with a keel (in most species), notarium, synsacrum, etc. that are beyond the scope of this discussion.8
Avian cortical bone is very dense with high tensile strength, but is also very thin and brittle, resulting in a bone that shatters or splinters easily on impact.5
While mammalian bones heal primarily by formation of woven bone in the subperiosteal space, avian fractures heal primarily by woven bone formation at the endosteal surface (within the intramedullary cavity). This type of callus can be difficult to appreciate radiographically.5
Birds usually incorporate bone fragments into the healing fracture and sequestra are rare.5
Healing can be rapid, particularly in birds with high metabolic rates, such as neonates and juveniles and small passerines. An endosteal callus sufficient to stabilize the fracture may present as early as 3 weeks.10
During egg laying, dramatic mobilization of medullary calcium stores may occur, increasing physiologic demands for calcium.10
The propatagium creates the leading edge of the wing. This structure is often damaged during trauma or can contract secondary to fracture stabilization techniques. Propatagial structure and function must be maintained for the patient to retain flight capability.5
There is little soft tissue surrounding the appendicular bones of the avian skeleton, leading to a high risk of vascular compromise, loss of peripheral nerve function, and a poor tolerance for subcutaneous hardware. In addition, fractures are often open, increasing the risk of bacterial infection.5
Clinical Signs
Common avian fracture presentations include the inability to fly, drooping of the wing, lameness, and an inability to stand. However, it is important to note that birds with coracoid or pectoral girdle fractures may still be able to fly, although they may not generate lift due to an inability to lift the wing above a horizontal plane. These types of fractures are common with impact injuries (flying into a window or hit-by-car).5
Patient Stabilization
Therapies for initial stabilization of the avian fracture patient should include:
Fluid Support
Significant blood loss may have occurred. In small patients, blood loss may not need to be external to be significant, as a large hematoma at the fracture site can represent significant loss of circulating blood volume. If significant blood loss has occurred a blood transfusion may be necessary. Fortunately, avian erythrocytes have a short life span, therefore regenerative responses generally occur quickly.9 In initial triage, replacement of circulating volume and support of blood pressure may be aided by:
Intravenous or intraosseous fluids: An intraosseous catheter in the distal ulna or proximal tibiotarsus, or an IV catheter in the medial metatarsal vein may be placed and maintained.2 The author prefers to place catheters under isoflurane anesthesia, but in a very compromised patient, a local lidocaine block may be performed prior to IO catheter placement. The author prefers to administer a shock dose of 20 mL/kg of IV or IO fluids then reassess the patient to determine replacement and maintenance fluid needs.
Colloids: Hetastarch at 10–15 mL/kg IV or IO will help maintain intravascular oncotic pressure.3
Subcutaneous, IV, or IO fluids for volume replacement plus maintenance: Maintenance fluid rates for birds vary depending on the taxonomic order. The author administers 60 mL to 120 mL/kg/day, with the higher end of the range given to small birds with a high metabolic rate, such as passerines.3 Subcutaneous fluids may be administered in the prefemoral/inguinal fold (being careful not to penetrate into the coelom) or may be administered dorsally between the scapulae.2 Be careful not to administer subcutaneous fluids in the region of a fractured pneumatic bone (femur or humerus) to avoid fluid migration into the circulatory system.5
Antimicrobials
In an open fracture, immediate systemic antibacterial therapy is important for preventing infection at the fracture site. Birds that have injuries secondary to predation should be started on antibiotics since small puncture wounds may be difficult to appreciate due to plumage. The author frequently administers:
Azithromycin 20 mg/kg PO q48h3 for gram-positive and anaerobic coverage
Clindamycin 50 mg/kg PO BID3
Enrofloxacin 10–20 mg/kg PO QD3 for broad spectrum aerobic coverage. Avoid the injectable form which can cause significant tissue necrosis.
Prophylactic antifungal therapy is helpful to prevent opportunistic aspergillosis infections, particularly in Falconiformes (falcons), Accipitriformes (hawks, eagles, old world vultures, etc.), Cathartidae (new world vultures), Galliformes (chickens, pheasants), Anseriformes (swans, geese, etc.), Gruiformes (cranes), Ciconiiformes (storks), and Sphenisciformes (Penguins).
Itraconazole 5–10 mg/kg PO QD administer with food3
Terbinafine 15 mg/kg PO QD3
Analgesics
Some bird species have a predominance of kappa opioid receptors.6 Please note that avian analgesic recommendations frequently change due to active research and new publications in this area of interest.
Butorphanol 0.5–2 mg/kg IM q1–4h3
Carprofen 2 mg/kg IM BID3
Meloxicam 0.2–1 mg/kg IM or PO BID3
Local blocks using lidocaine may also be helpful in controlling initial pain. If the patient is anesthetized or easily compliant with manual restraint, the author administers a local block of lidocaine at a maximum dosage of 5 mg/kg.
Warmth
Birds with fractures often have a compromised feather layer due to matting of feathers from blood or feather removal. Supplemental heat in an incubator helps reduce the metabolic demand for maintaining body heat. The author maintains incubators at 85 to 88°F for most avian species.3 Ensure that there is humidification in the incubator to prevent excessive drying of respiratory airways.
Supplemental Oxygen
Due to blood loss and the high baseline metabolism of birds, an increased demand for oxygen may be present when a fracture occurs. Supplemental oxygen in an incubator aids in patient stabilization.
Bandaging of the Fracture Site
It is not necessary to cut feathers to apply bandaging. In wildlife patients, cutting feathers may delay release of the bird until the next molt.
Open fractures: Clean and prevent dessication of the tissues by moistening with sterile saline. When cleaning open fractures of pneumatic bones (humerus, femur) take care not to allow fluids to run into the medullary cavity of the bone or surrounding tissues. This could result in fluid migration into the respiratory system of the bird.5 After wound cleaning, a small piece of moist saline overlaid with Telfa can be placed over the wound as part of the initial bandage to prevent wound desiccation.
Body wrap: Appropriate for thoracic limb fractures proximal to the elbow.5
Figure-8 wrap: Appropriate for elbow injuries or thoracic limb fractures distal to the elbow.5 This may be paired with a body wrap for maximum immobility. Thermoplastic splint or SAM splint material may be placed under the bandage to help stabilize a carpometacarpal fracture.
Modified Schroeder-Thomas splint: Effective for fractures proximal to the tarsometatarsal-phalangeal joint (proximal to the foot). Be sure to immobilize the tarsometatarsal-phalangeal joint in the case of a tarsometatarsal fracture.4
Single digit wrap with a ball bandage: Effective for digit fractures.
Patient Assessment
Once the patient is stable, in addition to completing a thorough physical examination, radiographs are useful to assess the fracture site. Radiographs are best performed under anesthesia to ensure proper patient positioning and to reduce patient stress, and radiographic views should be orthogonal. It is important to note that a bird in dorsal recumbency and a bird in lateral recumbency with the wings pulled dorsally generate the same radiographic views of the wing. When radiographing a wing fracture, it is the author's preference to take one radiographic view with the bird in dorsal recumbency. The patient is intubated for the orthogonal view to reduce the risk of regurgitation and aspiration. The bird is held with the feet and tail in one hand elevated at 60 degrees from horizontal and the head lying on the radiographic table or plate. The feet and tail are angled away from the affected wing so that the shoulder of the affected wing is not overlapped by the body in the radiographic image. The distal primary feathers of the affected wing are then grasped and used to gently extend the wing. This should result in the primary feathers being 60 to 90 degrees from horizontal with the affected wing overlying the radiographic film. This will result in a caudal-to-cranial view of the wing. It is paramount that the individual restraining the patient in this position wear appropriate personal protection including lead gloves.
Full assessment of the fracture is important for determining the most appropriate therapy. For return to full function (as needed in a wild bird of prey), the following appendicular fractures usually need surgical repair:2,4,5
Severely displaced coracoid fractures
Humerus
Radius (the rare exception may be when anatomic displacement has not occurred or in small birds such as passerines)
Displaced major carpometacarpus
Femur
Tibiotarsus
Tarsometatarsus
Surgical repair is best performed in 24–48 hours if not immediately to reduce muscle contracture and callus formation prior to surgery, which can worsen the prognosis. The advantage to surgical repair is that the patient may heal with minimum bandaging and a faster return to normal function during the healing process. This will minimize the risk of lost soft tissue function that could prevent a full recovery.
Fractures that may be treated with external coaptation include:2,4,5
Clavicle/furcula
Scapula
Non-displaced or minimally displaced coracoid fracture
Non-displaced ulna
Non-displaced major carpometacarpus
Minor carpometacarpus
Foot
Nestlings
Birds < 50 g
Birds in which a full return to function is not necessary (pocket parrots)
Often birds with fractured wings and a non-repairable patagial damage, in which return to flight, and therefore, full function, is not possible
If the bird will have surgery at a later time, it may be advantageous to gently pluck the feathers at the surgical site when the bird is anesthetized for radiographs. This will reduce surgical time for the patient. These feathers will include the downy feathers or coverlets overlying an open fracture site, but do not include primary or secondary flight feathers. Closed fractures may not require an open reduction, so plucking at the surgical site may not be necessary.
Additional Case Management
Once the fracture site has been stabilized, then the practitioner can anticipate additional diagnostics and therapies. Appropriate diagnostics and therapies may include:
Complete blood count, chemistry panel, and Aspergillus panel (antibody, antigen, galactomannan, and protein electrophoresis) at the first post-operative recheck examination. The bird has usually recovered from any blood loss at this point and blood samples for clinical pathology can safely be collected.
Continued antibiotic therapy as long as there is transcutaneous hardware or healing cutaneous wounds. The author recommends radiographs every 10 days to monitor for osteomyelitis of open or surgically stabilized fractures.
Continued antifungal therapy. Wildlife and patients not accustomed to hospitalization and handling will be at risk for opportunistic Aspergillus infections.
Continued analgesic therapy to maintain patient comfort and encourage normal behaviors.
Pentoxyfylline. This medication improves red blood cell flexibility, thereby improving circulation through damaged vasculature and to the distal extremities. The author uses a dosage of 10 mg/kg PO QD.7
Calcium supplementation. Some females may have a calcium deficiency due to poor nutrition and ongoing egg-laying. In addition, healthy females that have a fracture during egg-laying season may have an increased demand for calcium. The author administers calcium glubionate at 25 mg/kg PO QD during the healing period.3
Nutritional support. Particularly if the bird went through a period of inappetance, then nutritional support will be necessary. Gavage feed 2% BW twice daily at first when the bird is being handled for administration of other treatments. Administer formula as the last procedure before returning the patient to the enclosure to reduce the risk of regurgitation. Weigh birds daily and increase nutritional support as indicated by weight trends.
Sun exposure has been found to be important in some species for proper calcium metabolism.1
Physical therapy starting 3 days postoperative in surgically stabilized patients or 5 days in bandaged patients. Perform under anesthesia. Limit to very gentle stretches and massage and manual stretching of the patagium until the fracture site is stable. This will help prevent patagial contracture. In cases of radial and ulna fractures, it will help to reduce the risk of synostosis.5
References
1. de Matos, R. 2008. Calcium metabolism in birds. Vet. Clin. Exot. Anim. 11: 59–82.
2. Harrison, G. J., T. L. Lightfoot, and G. B. Flinchum. 2006. Emergency and critical care. In: Harrison, G. J., and T. L. Lightfoot (eds.). Clinical Avian Medicine. Spix Publishing, Inc., Palm Beach, Florida. Pp. 213–232.
3. Hawkins, M. G., H. W. Barron, B. L. Speer, C. Pollock, and J. W. Carpenter. 2013. Birds. In: Carpenter, J. W., and C. J. Marion (eds.). Exotic Animal Formulary. 4th ed. Elsevier Saunders, St. Louis, Missouri. Pp. 183–437.
4. Martin, H., and B. W. Ritchie. 1997. Orthopedic surgical techniques. In: Ritchie, B. W., G. J. Harrison, and L. R. Harrison (eds.). Avian Medicine: Principles and Application (abridged). Wingers Publishing, Inc., Lake Worth, Florida. Pp. 638–651.
5. Orosz, S. E. 2002. Clinical considerations of the thoracic limb. Vet. Clin. Exot. Anim. 5: 31–48.
6. Paul-Murphy, J. 2006. Pain Management. In: Harrison, G. J., and T. L. Lightfoot (eds.). Clinical Avian Medicine. Spix Publishing, Inc. Palm Beach, Florida. Pp. 233–240.
7. Plumb, D.C. 1999. Veterinary Drug Handbook. 3rd ed. Pharma Vet Publishing, White Bear Lake, Minnesota. Pp. 499–500.
8. Proctor, N. S., and P. J. Lynch. 1993. Manual of Ornithology: Avian Structure and Function. Yale University Press, New Haven, Connecticut. Pp. 117–174.
9. Shaw, S., T. N. Tully, Jr., and J. Nevarez. 2009. Avian transfusion medicine. Compend. Contin. Educ. Vet. 31:E1–E7.
10. Tully, T. N., Jr. 2002. Basic avian bone growth and healing. Vet. Clin. Exot. Anim. 5: 23–30.