Fracture Management in Birds

Vet Times The website for the veterinary profession https://www.vettimes.co.uk 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

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