Fracture Management in Birds

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FRACTURE MANAGEMENT IN BIRDS

Author : Richard Jones

Categories : Vets

Date : July 15, 2013

RICHARD JONES looks at methods of repairing fractures, including practical considerations, such as cage rest, dressings and internal fixation

FRACTURES as a result of trauma, with or without underlying nutritional deficiencies, are a relatively common presentation in both companion birds (parrots, falconry birds and backyard poultry) and wildlife casualties.

Thankfully, with the development of modern anaesthesia and fixation techniques, we are well equipped and prepared to deal with such injuries as they arise. Basic principles apply, taking into consideration a number of anatomical and physiological differences encountered in the avian patient.

Anatomy

The avian skeleton is fundamentally and significantly different from its mammalian counterpart, with the majority of adaptations designed around weight reduction for flight.

• Thin, brittle cortices. Avian bones have a comparatively higher mineral content, resulting in an increased incidence of open, comminuted fractures with multiple “sharp” fragments that can be traumatic to surrounding soft tissues. In addition, their much thinner cortices have implications for the holding power of fixation devices as it is widely accepted that bone thickness should be at least twice the thread pitch of a threaded implant for adequate stability.

• Monocoque and crosslinked structure. Avian bones rely less on mass and more on their

1 / 54 specialised structure for their inherent strength. Despite thin cortices, these lightweight bones gain strength from their monocoque structure (a construct like an egg shell, ping pong ball or air craft fuselage that support loads through the object’s intact external skin). Such lightweight devices are extremely strong when forces are applied in the “right” direction, but are easily weakened once the “skin” is breached, which has implications for implant fixation. Criss-crossing struts or trusses are also apparent, which provide additional strength.

• Pneumatisation. In birds, most of the vertebral, pelvic, sternal and costal bones are invaded by diverticula of the air sac system, which replace the bone marrow. The limb bones vary greatly in their degree of pneumaticity, but, in most species, include the humerus and femur (in the domestic foul, it is the humerus only). This has implications for surgery; as well as the slightly disturbing sight of blowing blood bubbles from the end of a fractured humeral stump during ventilation, excessive lavage of the area may theoretically result in pathogens entering the respiratory system.

• Minimal soft tissue coverage. There is a paucity of soft tissue over the long bones, which limits protection and increases the chance of vascular damage and exteriorisation of fragments. This can be advantageous, however, easing access to the fracture site, making surgical manipulation and reduction technically less taxing.

• Feathers. Feathers can be annoying and messy when preparing a site for surgery. With care, a portable “dust buster” – type device is often useful to avoid feathers flying around the prep area and, so far at least, I have yet to vacuum a budgie off its ET tube. Plucking feathers from a bruised area has to be done with extreme care to avoid further damage to already traumatised, friable skin, which is at a premium on especially the distal limb. Feathers can be useful however, especially in fractures of the metacarpals and ulna. Being attached directly to the periosteum, they offer a degree of support, and resist the tendency of collapse and overriding of fragments in the short term.

• Bone grafting. Birds have no readily available source of cancellous bone, although techniques have been described where it is harvested from the sternum. Fortunately, birds are prolific callus makers and, in select cases, autogenous, excess callus can be harvested and used to encourage osteoconduction and synthesis where deficits exist.

Bone healing in birds

Clinically, avian bones seem to heal faster than mammalian bones. As in mammals, bone healing may occur as primary or secondary healing, although the vast majority of avian fractures will result in the latter, characterised by stages of inflammation, soft callus formation and remodelling. In chickens, it has been shown maximum callus formation in the radius was achieved in two to three weeks. This coincides with the author’s personal observations that, in most cases, implants could be removed in three to four weeks, although as long as they are not loosening or causing soft tissue trauma, staged implant disassembly and removal is usually spread over four to six weeks,

2 / 54 depending on the nature of the fracture.

to 1e illustrate healing of a humeral fracture in a European kestrel (Falco Figures 1a tinnunculusThe radiographs) in which in functional union, as denoted by symmetrical flight, was achieved in less than six weeks.

Our goals in avian fracture repair are identical to those in mammals:

• to achieve accurate anatomic reduction of the fracture ;

• to cause minimal trauma, thus preserving fracture site biology and vascularity;

• to apply rigid fixation, satisfying the mechanical needs of the fracture;

• to restore limb function as soon as possible to reduce incidence of fracture disease;

• to minimise pain; and

• to do it as quickly and cost effectively as possible.

Methods of repair

There have been many descriptions of fracture management in birds and this field, like many others in avian medicine and surgery, is constantly evolving. The following procedures are not the only methods that could be used for each fracture, but gave satisfactory results in the respective cases.

• Cage rest

Some fractures in birds heal adequately with no form of applied fixation at all. Fractures of the pelvic and shoulder (coracoids, clavicle and scapula) girdles can, in many cases, heal without external/internal support. In a retrospective study at the University of Minnesota Raptor Center, it was demonstrated that compared to surgery of coracoid fractures in wild injured raptors (where due to the pectoral muscle mass, surgical approach is challenging and traumatic) conservative management resulted in a much higher percentage of releasable birds.

Minimally displaced and greenstick fractures also heal well by restricting the bird’s activity using cage rest and appropriate analgesia.

• External coaptation

Many fractures in birds are amenable to repair using external coaptation. External coaptation is

3 / 54 most appropriate if the bone is too small for internal fixation. It is a cheap, simple and effective method of immobilising select fractures. Application is generally quick, requiring a short anaesthetic only, if at all, with many performed in the conscious patient following analgesia. There is less risk of infection with closed fractures, but limb function may be compromised in many cases. Due to the unstable and overriding nature of fractures of the humerus and femur, with resulting malalignment and limb shortening, external coaptation is deemed unsuitable for such fractures.

“Mouldable splints”, fashioned from padded aluminium finger splints, pipe cleaners or dressing materials and “wing wraps” or “figure of eight dressings”, can be used to manage a variety of fractures.

Appropriately applied figure of eight dressings are particularly useful for the first aid or ultimate management of ulna or metacarpal fractures. A cohesive dressing is applied as high up as possible in the “arm pit” by ensuring the material is passed between the tertiary feathers (attached to the caudal humerus) and the body, and a couple of loops are passed around the folded wing as shown (Figure 2). To avoid excessive tension, resulting in vascular and soft tissue compromise, it is useful to unwrap and lightly re-roll the dressing prior to application. To prevent the dressing slipping off below the elbow, the material is then brought up and “loosely” placed around the carpal joint avoiding excessive pressure on the patagial ligament that supports the delicate wing web responsible for creating the aerofoil essential for flight. This is repeated and secured with zinc oxide. Figure of eight dressings must be changed or at least checked every five days (ideally under sedation/anaesthesia) to monitor underlying soft tissue and ensure integrity of the patagium.

An easily applied body wrap (Figure 3) using “feather friendly” latex-free, surgical tape, although generally unsuitable as a sole means of fracture stabilisation, is extremely useful as a first aid measure. Following humeral fractures, the wing tends to drop and rotate about the fracture site and, with the action of the powerful pectoral musculature on the now razor-like proximal stump, this can cause significant soft tissue and vascular injury. Our clients are coached in this technique, among others, so if a fracture occurs in the field such dressings can be applied immediately, dramatically improving the chances of a successful outcome.

Due to the highly comminuted nature of an ulna fracture in a wild peregrine falcon (Falco peregrinus), but, importantly, with radius intact acting as a natural splint, this case was managed using a series of figure of eight dressings. Following a two-month period of rehabilitation in a large circular aviary or hack pen used for fitness training in captive bred falconry birds, this bird was successfully returned to the wild.

In the author’s opinion, if both radius and ulna are fractured, fixation of the radius is mandatory and easily achieved via retrograde placement of an intramedullary pin, while surgical repair of the ulna is optional, depending on the fracture. In a good proportion of cases, once the radius has been stabilised and antibrachial length restored, the ulna may be brought into alignment and dealt with conservatively as above.

4 / 54 A closed midshaft tibiotar sal fracture in a king parrot chick (Alisterus scapularis) was successfully managed using a series of mouldable splints, starting with a pipe cleaner and progressing to a finger splint as the bird developed. The splints were moulded and dressed to the cranial limb, incorporating stifle and hock joints and changed/modified every three to five days because of the rapid growth rate of the bird in question (Figures 4a and 4b).

“Sandwich splints” are particularly useful for fractures of very small bones such as passerine tibiotarsi/tarsometatarsi or digital fractures as illustrated in a goshawk (Accipiter gentilis; Figures 5a to 5c) where support is required, but a degree of controlled movement essential to avoid the entrapment of tendons within the developing callus. A sheet of dressing material is cut to size and used to create a “gutter splint”, which is pinched over the top of the digit for added rigidity. It is then covered with conforming bandage and zinc oxide tape to produce the desired rigidity.

Well aligned or “green stick” tarsometatarsal fractures can be managed using a padded aluminium finger splint moulded into a “stirrup” under the foot, which, as well as providing support to the healing bone, encourages limited weight bearing and early return to function.

• Internal fixation

In the majority of cases, the most satisfactory results in terms of restoration of limb anatomy and function are achieved using internal fixation.

In comparison to mammalian patients, bone plating has received scant attention for a variety of reasons, including small patient and bone size, cost, morbidity associated with placement and in the case of wild birds the need for follow-up surgeries to remove implants. In the author’s opinion, with the exception of articular fractures, bone plating appears to offer no significant advantages over the more traditional (and cheaper) techniques described below.

Intramedullary (IM) pins and external skeletal fixators (ESF) alone continue to be used with success as shown in a metacarpal fracture in a golden eagle (Aquila chrysaetos; Figure 6) and ). tarsometatarsal fracture in a Harris hawk (Parabuteo unicinctus; Figure 7

The introduction of the ESF – IM pin “tie in” or “hybrid” fixator, however, has revolutionised the management of avian long bone fractures.

When properly applied, the hybrid fixator is able to oppose axial, shear, bending, torsional and compressive forces acting on fractured avian bones while allowing early return to function, increasing the predictability of a satisfactory outcome. In the case of falconry birds or wildlife casualties this necessitates complete restoration of anatomy and functionality.

This minimally invasive approach to osteosynthesis results in the restoration of bone length and angulation while at the same time preserving the fracture envelope. Staged disassembly of the

5 / 54 apparatus over a period of four to six weeks ensures the functional load is very gradually transferred back on to the healing bone.

Traditional techniques of manipulating and wiring every single fragment back in place admittedly make beautiful postop x-rays, but can result in vascular injury and sequestra. Experience has shown that, provided bone length and joint anugulation are restored, with the constant remodelling processes governed by controlled stresses applied to the healing bone, even the most ugly, comminuted fracture site will knit together, remodel and provide a functional union. A quote that has always stuck with me from one of my mentors, Pat Redig at the University of Minnesota, is “avian orthopaedics is as much about gardening as it is carpentry”, emphasising the importance of the gentle handling, nurturing and support of injured tissue.

Hybrid fixators have proved especially useful for fractures of the tibiotarsus, humerus and femur.

In most cases, all that is required in addition to standard surgical equipment, is a small hand chuck, a series of positive profile ESF pins ranging from 0.035in to 0.078in, a selection of Steinmann pins, mini ESF clamps, soft plastic tubing and methyl methacrylate or similar quicksetting product.

Tibiotarsal fractures are one of the most common fractures encountered in practice and the images document the repair of a closed tibiotarsal fracture in an umbrella cockatoo (Cacatua alba). in Figure 8 Using the hand chuck, an appropriately sized Steinmann pin is introduced via the cranio/ medial aspect of the proximal tibiotarsus (Figure 8b). The fracture is reduced with gentle manipulation and IM pin seated distally (Figure 8c). Again, using the hand chuck, threaded half pins are introduced laterally via “safe corridors” into the proximal and distal fragment.

Traditionally it has been recommended that fixator pins should be placed at 70° to the long axis of the bone to lessen the likelihood of frame “pull out”. This is still in some textbooks – a carry-over from the days of “smooth pin” fixators. Angling the pins decreases the number you can fit in a bone segment, thus when using positive profile pins it is recommended the pins are placed perpendicularly to the long axis of the bone.

The IM pin is bent over and “tied in” to the construct using bar and clamps (Figures 8d and 8e). In many cases, with the fracture stabilised but joints above and below still freely mobile and with the benefit of perioperative analgesia (see later), the bird will weight bear and be ambulatory on recovery, minimising the incidence of fracture disease.

The following patient Alan, a 160g Hahn’s macaw (Diopsittaca nobilis) presented with an open fracture of the humerus when the roof of his aviary collapsed during high winds. Following stabilisation, the fracture was repaired using a hybrid fixator, placing an IM pin retrograde tied into ) a proximal and distal threaded pin via a dorsal approach (as in Figure 1

6 / 54 Despite the apparent bulk of the fixator/clamps in such small species, with the apparatus up against the body as occurs with humeral and femoral fractures, the patients tolerate these extremely well for the month or so they are in situ. (In fact to the owners’ delight, but to my horror, they reported Alan could indeed fly with his fixator in place).

Useful alternatives in the smaller species are methyl methacrylate-filled plastic/rubber tubing (which even the smaller parrots seem to be able to destroy with that “can opener” they have on their face), or the FESSA (Fixateur Externe du Service de Sante des Armes) system developed for use in complex fractures of the hands and feet in humans, in which bar and clamps are replaced by a “multi-faceted” stainless steel tube and grub screws that anchor the fixator pins.

A femoral fracture in a khaki Campbell duck posed an interesting challenge, as due to its egg- laying activity the normally IM pin-friendly avian femur had become packed with concretelike medullary bone, which is used as a readily accessible mineral store for egg production. Due to the fragile nature of avian bones, drills are not generally required and actually contraindicated in most cases, however this was one case when it would have been extremely useful.

Using a hand chuck, a pin was finally introduced retrograde via a lateral approach and tied into a proximal and distal ESF. The fracture healed uneventfully with staged removal of implants over a period of five weeks and, interestingly, as in a similar case in a laying hen, she stopped laying the day of the fracture and almost immediately started up again once functional healing was complete and she once again had some calcium to spare.

Beak fractures

Bird’s beaks are essentially modified skin supported by the maxilliary and mandibular bones and, as with skin injuries, to the beak can heal by first or second intention. In this case, a blue and gold macaw sustained a severe depression fracture of its maxilla when a door it was hanging off at the time slammed shut. The underlying bone and soft tissue was elevated back into position and pins placed to support and anchor a pad of surgical dressing, which is used following oral trauma surgery in humans to cover implants and open wounds. This product, which sets to the consistency of dried chewing gum, supports and protects the healing tissue and encourages granulation and epithelialisation. This dressing does not adhere to the beak or wound and was changed weekly to 9e). under anaesthesia until epithelialisation was complete – in this case, 10 weeks (Figures 9a

Postoperative care and physiotherapy should include a number of action points.

• Antibiosis – culture-based antibiotics are used for any contaminated wounds and the author favours marbofloxacin 10mg/kg perioperatively.

• Analgesia – butorphanol 1.0mg/kg to 2mg/kg IM and meloxicam 0.5mg/kg per os are used

7 / 54 perioperatively with meloxicam continued as long as deemed necessary. Early return to function is encouraged to minimise the incidence of fracture disease and, as well as appropriate choice of fixation, effective analgesia is extremely important in this regard.

• Foot and feather protection – tail sheaths fashioned from x-ray film or similar are used to protect tail feathers of raptors in the immediate postoperative period. Falconry clients can be pretty obsessive regarding feather maintenance, so a top tip to deal with accidentally bent feathers is to steam them in the spout of a boiling kettle – be sure to put your hand between the feathers in the bird, so your hand feels the heat first. In fact, next time you come across a feather, bend it in half and try it – trust me, you’ll be impressed.

• Broken flight or tail feathers can be repaired or imped using an identical feather from a previous moult or donor bird.

• In the case of hindlimb fractures, it is extremely important to look after the contralateral foot, which, following surgery, will be at risk of developing pressure sores or bumblefoot due to increased weight bearing. This can be achieved using artificial turf on perches in the case of raptors, padding perches or providing platforms for the parrots or vet bed/deep bedding for poultry/waterfowl. It is not unusual for foot function to be compromised immediately following hindlimb surgery. To avoid trauma to the dorsal aspect of digits and encourage weight bearing, “shoes” fashioned from a disc of pipe lagging can be dressed to the foot to keep it open. It is critical to match the colours of such shoes to the owner’s footballing tendencies (Leicester City in this case), which, as a Nottingham Forest fan, was extremely painful to do.

• Cage/pen rest offers controlled and limited limb function, but avoids flight and, hopefully, prevents further injury while fixation is in place and for seven to 10 days following implant removal.

• Aviary rest. Once a functional union is achieved, a month or so in an aviary will allow gradual restoration of flight and promote muscle development and fitness.

• The use of appropriate physical therapy is integral to the success of all orthopaedic procedures to avoid fracture disease (such as muscle wasting, joint stiffness, degeneration of intra-articular cartilage and osteoporosis). Cold therapy using ice packs is used in the acute phase of the injury and perioperatively to control swelling and pain. Heat therapy using microwaved moist towels or hot packs can be beneficial in the more chronic phase of healing to promote circulation (especially useful in distal fractures, for example metacarpals). Passive physiotherapy is performed under anaesthesia and involves the controlled stretching of muscles, tendons and ligaments. Active physiotherapy begins with the choice of appropriate fixation, allowing early return to function of the limb and essentially involves controlling activity initially by confinement, with progression to flight as discussed.

• As in any athlete, return to function of the limb is only the beginning of the rehabilitation process.

8 / 54 A period of careful conditioning is required for a performance bird to regain full fitness. Techniques performed by falconers and rehabilitators include lure training, in which the hawk chases and retrieves a food reward from a lure swung by the falconer or suspended from a kite that can be raised to heights of several hundred feet as dictated by the bird’s performance.

Conclusion

Avian orthopaedics presents a unique challenge to the veterinary practitioner, but with a good knowledge of bone repair techniques in mammals and an understanding of the anatomical and physiological differences in avian patients, repairs can be enjoyable, rewarding and ultimately successful.