ORTHOPAEDIC SURGERY
Standard orthopaedic principles and techniques are applicable to Australian mammals; however, unique anatomy (Table 10.1) and the specific constraints relating to surgery described above must always be carefully considered.
Thorough radiographic evaluation is recommended for assessment and evaluation of therapeutic options before any orthopaedic surgery (Vogelnest and Allan 2015).2.1 Limbs and pelvis
Free-ranging short-beaked echidnas (Tachyglossus acu- leatus) commonly sustain pelvic and limb fractures when struck by vehicles while crossing roads. Conservative treatment of uncomplicated fractures through restricted activity is often successful (Middleton 2008). Fractures with significant displacement are difficult to repair surgically because of the unique skeletal anatomy, often have poor outcomes and may warrant euthanasia. A closed, transverse midshaft radius and ulnar fracture was successfully repaired by plating the radius (Reynolds and Sommerland 1996).
Wombats commonly sustain fractures through vehicle impacts and PY are often simultaneously injured (Bryant and Reiss 2008). Bilateral distal femoral Salter-Harris type I fractures were successfully repaired in a 13-mo-old hand-reared southern hairy-nosed wombat (Lasiorhinus Iatifrons). The epiphyseal fragments of both fractures were caudally displaced ~13 mm relative to the femoral shafts. For each fracture, the stifle joint was accessed through a parapatelloid arthrotomy and the patelloid was subluxated medially to access the joint and secure the fragments with Kirschner wires (Anderson et al. 2015).
Pinnipeds commonly sustain traumatic fractures and if open may become contaminated from the marine environment (Sweeney 1990). Refractory phalangeal osteomyelitis may necessitate digit amputation. Suturing the flipper skin with a horizontal mattress pattern may decrease the likelihood of dehiscence; otherwise, healing may continue by second intention (Higgins and Hendrickson 2013).
Successful tibial fracture repair using a locking plate in a grey seal (Halichoerus grypus) pup (Hespel et al. 2013) and open reduction of a luxated elbow in a California sea-lion (Zalophus californianus) (Malabia et al. 2011) have been reported. These techniques are applicable to Australian pinnipeds.2.1.1 Special considerations for long and other bone repair in macropods
In macropods, long bone fractures are common and repair in adults is generally unsuccessful. It is difficult to achieve adequate fixation and stabilisation because of the biomechanical forces, the limited capacity to weight-bear on one hindlimb and postoperative confinement often being poorly tolerated (Vogelnest and Portas 2008). External fixators have been successfully used for tibial repair in hand-reared macropods (Vogelnest 2015). Metatarsi may be repaired with internal or external fixation. Antebrachial fracture repair using type 1a external skeletal fixation has been described in a small number of adult macropods; repair has a fair prognosis in adults and a
Table 10.1. Anatomical features of Australian mammals to consider in surgical decision-making
| Anatomical feature | Species | Surgical consideration |
| Pouch | Marsupials | Pouch (±PY) may make caudal abdominal access difficult1 |
| Pelage | Fur seals, platypus | Thick, insulating and waterproofing fur is difficult to clip; need to keep clipped |
| (Ornithorhynchus anatinus) | area small to minimise effect on insulation (particularly platypus and free- ranging fur seals), which may complicate surgical access | |
| Short-beaked echidna (Tachyglossus aculeatus) | Quills restrict surgical access | |
| Patagium | Bats, gliders | Injuries to patagial membranes may have poor healing and lead to stricture |
| Abdominal wall | Numbat (Myrmecobius fasciatus) | Skin is tough and difficult to incise; the linea alba is poorly defined2 |
| Koala (Phascolarctos cinereus) | The linea alba is wide (1-3 cm), ventrolateral abdominal muscles are thin (2-3 mm) and there is minimal SC tissue3 | |
| Pinnipeds | Blubber and peritoneum have poor suture-holding strength, healing is prolonged and the aquatic environment increases risk of dehiscence; in some pinnipeds abdominal musculature is thin,4 but is very well developed in Australian sea-lions (Neophoca cinerea)5 | |
| Cetaceans | Thick, inelastic abdominal wall limits access to abdominal cavity; difficult to ensure watertight incision repair because of poor suture-holding strength, pressure from internal organs; poorly vascular blubber heals slowly, dehiscence common6 | |
| Gastrointestinal tract | Herbivorous marsupials | Voluminous GIT, especially koala caecum, may interfere with access to other organs3,7 |
| Urogenital tract | Marsupials | Unique female reproductive tract complicates urogenital surgery1 |
| Limbs | Macropods | Hindlimbs subjected to extensive biomechanical forces; bipedal with limited capacity to weight-bear on a single limb7 |
| Monotremes, koala | Unusual long bone anatomy8 complicates effective internal fixation of fractures | |
| Bats | Fine bone structures8 and delicate webbing makes surgery technically challenging and may complicate healing | |
| Sacral plate | Wombats | Complicates access to pelvis and femurs for fracture repair; incisions cannot be made through the plate |
| Tail | Macropods, gliders, possums, | Management of tail injuries, especially amputation, requires consideration of |
| dasyurids, cetaceans | any specialised function such as locomotion (some macropods, cetaceans), balance (gliders, some macropods), prehension (some possums, potoroids), fat storage (platypus, dasyurids) | |
| Oral cavity | Macropods, koala, wombat | Narrow gape makes access to caudal oral cavity difficult, especially for dental surgery |
| Beak and bill | Monotremes | Monotremes have unique craniofacial anatomy with fine bones8 that make surgical repair challenging; access to the oral cavity is difficult |
1Vogelnest and Woods 2008; 2Vitali and Monaghan 2008; 3Blanshard and Bodley 2008; 4Sweeney 1990; 5Richardson and Gales 1987; 6Higgins and Hendrickson 2013; 7Vogelnest and Portas 2008; 8Vogelnest and Allan 2015
good prognosis in PY (Vogelnest and Portas 2008; Buscaglia and Black 2020). Dowling et al.
(2024) describe management of a tarsal luxation in a red kangaroo (Osphranter rufus) through surgical reduction and tarsal arthrodesis. Despite a relatively good outcome, this report highlights some of the challenges and post-operative complications often faced when attempting orthopaedic repair in macropods.2.1.2 Special considerations for bone repair in koalas
(Phascolarctos cinereus)
Closed fractures of long bones in koalas may heal with confinement alone. External coaptation with a cast or
Table 10.2. Suggested surgical approach and fixation techniques for koala (Phascolarctos cinereus) fractures (A Gillett pers. comm.)
| Bone | Surgical approach | Fixation options |
| Femur | Laterocaudal skin incision from proximal femur to stifle, along caudal outline of biceps femoris muscle, which is reflected cranially | • Plate • Interlocking nail • Avoid external fixator, particularly with a tie-in, as it can cause significant muscle trauma at the proximal femur |
| Tibia | Mediocranial incision over tibia extending from stifle to tarsus | • Plate or intramedullary pin; always apply supportive bandage with splint for 2-4 wk; or 6-wk minimum with concurrent fibular fracture • Tie-in external fixator • External fixator alone |
| Humerus | Lateral incision from point of shoulder to point of elbow. Avoid radial nerve across distal humerus. Note: humerus has spiral curvature and becomes flattened and wider distally1 | • Laterally placed external fixator preferred (Fig. 10.1) • IM pin with tie-in fixation is NOT recommended because of pressure necrosis at the shoulder and proximity to the animal's head • Plate for proximal fracture in young koalas (plate needs to be shaped). For larger koalas a plate may buckle, so added cast recommended. Casting combined with chest wrap in joey/sub-adults if the fracture is well aligned |
| 1Vogelnest and Allan (2015) | ||
supportive bandage and splint for 8-12 wk is often successful for mid-shaft, non-displaced tibial fractures and should be considered as an alternative to surgery. Suggested surgical approaches and fixation techniques for common koala fractures are listed in Table 10.2.
Coxofemoral luxations in koalas have been repaired with mixed success. Primary repair of the joint capsule in acute cases with good apposition and anatomical repair has a better prognosis. Chronic cases in which anatomical reconstruction and repair are not possible have a poor prognosis (P Moses pers. comm.). Repair is through reduction and capsular repair as described in dogs. The deep gluteal muscle may need to be partially transected to access the dorsocranial aspect of the capsule. For caudal capsule tears, access may require osteotomy of the greater trochanter, making this procedure more difficult. The shallow acetabulum of the koala and unusual anatomy makes for a very unstable hip joint. The toggle technique for repair has not been particularly successful (P Moses pers. comm.). Postoperatively, koalas should be cage rested (no climbing) for 7-14 d and are typically walking in a few days. Prognosis for repair reduces significantly if the capsule tears again (A Gillettpers. comm.).
2.1.3 Bat wings
In bats, long bone fractures can be repaired with intramedullary pins, K-wires, modified hypodermic or spinal needles or type 2 external fixation devices (Heard 2003). Juvenile flying-foxes may cope with splinting if they remain wrapped and prevented from flapping their wings (S Frith pers. comm.). Fractured distal phalanges can be amputated without reducing flight ability (Olsson and Woods 2008). The site is aseptically prepared and lignocaine injected around the bone proximal to the amputation site.
The phalanx is exposed by making an incision along the leading edge of the bone and transected at the desired location before closing with simple interrupted sutures, ensuring at least 5 mm of soft tissue is covering the end of the bone. Surplus wing membrane can be trimmed conservatively and left to heal unsutured. The end of the wing can be lightly bandaged with padding and light dressing such as Tegaderm™ Film (3M Australia, North Ryde, NSW, Australia), Fixomull® Stretch (BSN Medical, Mount Waverley, Vic., Australia) or Medipore™ H (3M Australia). More adhesive dressings that are difficult to remove from fragile wing membranes should be avoided (S Frith pers. comm.) (see section 4.1). Free-ranging bats with amputations of the first digit should be assessed for suitability for release (see Chapter 42).2.2 Vertebrae
2.2.1 Cervical
Fractures of the second cervical vertebra (C2) are common in macropods after collisions. These may be associated with the poorly developed cervical muscles, weakness of the atlanto-occipital articulation, late (6-7 yr) physeal closure (C2 has a distinct physis between the cranial and caudal buttress) and incomplete ventral arch of the first cervical vertebra (Emerson 1983; Vogelnest and Portas 2008; Vogelnest and Allan 2015; Hulst et al. 2015). Attempts
Fig. 10.1. (a) Radiograph of external fixation placement in a koala (Phascolarctos cinereus) humerus and (b) postoperative image depicting external fixator placement. Photos: Amber Gillett
at repairing C2 have not been described and euthanasia is usually indicated (L Vogelnest pers. comm.). Surgical fixation using screws and polymethylmethacrylate to distract and stabilise cervical vertebrae was successful in a rednecked wallaby (Notamacropus rufogriseus) with a fourth cervical vertebral fracture (Kragness et al. 2016).
2.2.2 Tail
Macropods in permanent care will adapt to tail amputation, including high amputation (using standard surgical techniques), despite reliance on the tail for pentapedal gait. Occasional difficulty standing from lateral recumbency may ensue (Suedmeyer 1998; Vogelnest and Portas 2008). Distal tail trauma is common in eastern ring-tailed possums (Pseudocheirus peregrinus) (see Chapter 38). Amputation of the tail tip should be limited to ~2-3 cm of the white furred region, allowing the tail to remain functionally prehensile.
3.