Successful management of simple fractures of the femoral neck with femoral head and neck excision arthroplasty in two free-living avian species.
Abstract. A red-tailed hawk (Buteo jamaicensis) and a Canada goose (Branta canadensis) were evaluated for unilateral pelvic limb lameness. Physical examination findings and results of diagnostic imaging revealed femoral neck fractures in both birds. Both birds were treated with a femoral head and neck excision arthroplasty. The affected legs were not immobilized, and the birds were encouraged to use the legs immediately after surgery to encourage formation of a pseudoarthrosis. Within 2 weeks, both birds were using the affected limb well enough to be either successfully released or transferred to a wildlife rehabilitation facility. Femoral head and neck excision arthroplasty without immobilization of the limb is recommended for managing avian femoral neck fractures, especially in free-ranging species in which a rapid and complete or near complete return to function is vital for survival in the wild.
Key words: femoral head and neck excision arthroplasty, FHO, lameness, free-ranging, avian, red-tailed hawk, Buteo jamaicensis, Canada goose, Branta canadensis
A free-living, 1.12-kg juvenile red-tailed hawk (Buteo jamaicensis) was presented to the wildlife medical clinic at the University of Illinois after being observed hiding in a bush and not using its left leg. During the initial evaluation, the bird was bright, alert, and responsive; muscle mass was appropriate, and a body condition score of 3/5~ was recorded, Mild dehydration was noted, as indicated by mucous strands present in the oral cavity. The hawk was non-weight bearing on the left leg, and crepitus was palpable during manipulation of the left hip. Results of neurologic evaluation of the bird were considered normal. The hawk was anesthetized by face mask induction with 5% isoflurane in oxygen and was maintained with 2.5% isoflurane to obtain radiographs. No abnormalities were observed on whole-body survey radiographs in standard ventrodorsal and left lateral positions.
Initial therapy included the administration of lactated Ringer's solution (50 mL/kg SC q12h), assisted feeding of mice, and carprofen (2 mg/kg PO q24h; Rimadyl, Pfizer Animal Health, New York, NY, USA) for analgesic and anti-inflammatory effects. Over the next 3 days, limb use improved although intermittent lameness persisted. The hawk began to eat well on its own, and assisted feeding and subcutaneous fluid administration were discontinued after 3 days.
Four days after admission, crepitus during left hip manipulation persisted, which prompted further radiographic evaluation of the coxofemoral joint. The hawk was anesthetized as previously described and was positioned in dorsal recumbency. Routine ventrodorsal and lateral radiographic projections with the legs extended failed to reveal any abnormalities (Fig 1). The ventrodorsal projection, mildly obliqued to better display the left hip (left ventral--right dorsal oblique view), with the left limb positioned neutrally (no abduction, adduction, flexion, or extension), demonstrated a fracture of the femoral neck, with 3-mm cranial displacement of the femoral neck from the femoral head, and increased medullary opacity of the left femoral head and neck (Fig 2). A computed tomography (CT) of the coxofemoral joint showed a minimally displaced, simple closed fracture of the left femoral neck, with sclerosis of the fracture fragments. A distinct lesion, indicated by minimally contrast-enhancing soft tissue attenuation in the proximal to mid diaphysis of the left femur, was identified (Fig 3). This lesion was consistent with inflammation or hemorrhage, but a specific etiology could not be determined.
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A femoral head and neck excision arthroplasty (FHO) was elected to manage the femoral neck fracture. Perioperatively, butorphanol (2 mg/kg IM q12h; Torbugesic, Fort Dodge Animal Health, Fort Dodge, IA, USA) and trimethoprim-sulfamethoxazole (48 mg/kg PO q12h) were administered prophylactically for pain and postoperative infection. Carprofen was continued as previously described. Anesthesia was induced by the previously described protocol, and the hawk was intubated with a 3.0 mm noncuffed endotracheal tube. A 22-gauge hypodermic needle was placed as an intraosseous catheter in the right distal ulna through which lactated Ringer's solution (10 mL/kg per hour) was administered during the surgical procedure.
A standard lateral approach to the avian coxofemoral joint was used. (2-4) Fibrous tissue surrounded the joint capsule and was associated with the femoral neck fracture. The round ligament was sharply incised, and the femoral head with attached neck was removed. The remaining femoral neck was removed by using rongeurs before closure. The joint capsule was closed with 4-0 polydioxanone suture (PDS; Ethicon, Inc, Somerville, NJ, USA) in a simple interrupted pattern. The iliotibialis and iliofibularis muscles and fascia were apposed with 4-0 polydioxanone by using a locking loop pattern. The skin was closed with 4-0 polyglactin 910 (Vicryl, Ethicon) suture in a Ford interlocking pattern.
[FIGURE 3 OMITTED]
The bird recovered uneventfully from anesthesia. Butorphanol and trimethoprim-sulfamethoxazole were continued at the perioperative doses for 2 and 7 days, respectively. Twenty-four hours after surgery, the bird was bright, alert, and displaying normal behaviors. Slight hyperemia was observed in the center of the right foot, and a regimen of cleaning the foot with 0.05% chlorhexidine (Nolvasan; Fort Dodge), followed by the application of camphor spirits and 8-hydroxyquinoline sulfate 0.3% in a petroleum jelly and lanolin base (Bag Balm, Dairy Association Co, Lyndonville, VT, USA) was instituted to manage stage 1/3 pododermatitis. (5) The hawk continued to improve and appeared to be fully weight bearing, perching normally, and using both feet to eat within 2 days of surgery. During passive range of motion exercises, no crepitus in the coxofemoral joint was palpated, and the hawk had normal range of motion. Eight days after surgery, the hawk was using the limb normally and was successfully released in the area where it had been found.
A juvenile 2.8-kg Canada goose (Branta canadensis) was presented to the wildlife medical clinic at the University of Illinois in poor body condition (body condition score, 1.5/5) with nonweight-bearing lameness of the left leg. The left tarsometatarsal region was swollen but stable. Anesthesia was induced with 5% isoflurane in oxygen administered by mask (1 L oxygen/min) and maintained with 2% isoflurane for radiographic evaluation. Routine ventro-dorsal and lateral radiographic projections revealed a comminuted fracture of the left distal tarsometatarsus and a transverse fracture of the basal phalanx on the second and third digits of the right foot.
The next day, the tarsometatarsal fracture was surgically stabilized by using a type II external skeletal fixator. The digit fractures were considered stable on palpation and were allowed to continue healing without intervention. Five weeks later, the tarsometatarsal fracture was healed, based on radiographic and clinical assessment, and the external skeletal fixator was removed in preparation for rehabilitation and release. During the 5 weeks of convalescence, the goose developed stage 1/3 pododermatitis, which was treated by using 0.05% chlorhexidine solution, camphor spirits, and topical silver sulfadiazine. Eleven days after removing the external skeletal fixator, the goose became acutely lame in the right leg after swimming and was given carprofen (1 mg/kg PO q12h) for analgesia. The next day the goose was non-weight bearing on the right leg, with palpable crepitus in the right coxofemoral joint. Butorphanol (2 mg/kg IM) was administered, and the goose was anesthetized for radiographic evaluation as previously described. With the goose positioned in dorsal recumbency and the legs extended, radiographs revealed a 2-mm cranial step displacement with a 1-mm gap fracture of the right femoral neck (Fig 4). The goose was given butorphanol (2 mg/kg IM q12h) and carprofen (1 mg/kg PO q12h) until surgery was performed.
Previously described doses of butorphanol and carprofen were given perioperatively for analgesia. An FHO was performed as described in case 1. Unlike the hawk in case 1, fibrous tissue was not found around the joint during surgery, which was indicative of the acute nature of the fracture. The goose recovered uneventfully from anesthesia. Treatment was continued with butorphanol for 2 days and carprofen for 10 days to manage pain and inflammation during the convalescent period.
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The morning after surgery, the goose was touching the toe to the ground on the right leg, and, by afternoon, it was bearing weight on the leg. Ambulation improved over the next 3 days. Ten days after the surgery, the goose was ambulating well, but the pododermatitis in the left foot was worsening. The decision was made to send the goose to a wildlife rehabilitation facility, expecting that a change in substrate, with increased swimming time, might aid in the resolution of the pododermatitis. Two weeks after being sent to a wildlife rehabilitation facility, the pododermatitis improved, and the bird was only mildly lame on the right leg. The lameness resolved completely within 2 months, and the goose was successfully released after overwintering to allow plumage to regrow.
Femoral head and neck injuries in birds occur most often secondary to trauma and are diagnosed based on clinical signs and imaging techniques. Radiographic visualization of the avian coxofemoral joint is hampered by the short femoral neck and the superimposition of the femur over the pelvis, synsacrum, contralateral limb, kidneys, and digestive tract. Accurate diagnosis is necessary to implement appropriate therapy. This case series demonstrates the usefulness of strategic positioning to obtain diagnostic radiographs of birds with femoral head and neck fractures, and demonstrates the effective management of these injuries with an FHO.
The red-tailed hawk described had obvious crepitus and pain isolated to the coxofemoral joint, with the minimal displacement of the fracture, preventing diagnosis based on radiographic evaluation when using routine positioning. The nonstandard oblique view with neutral positioning of the limb in the ventrodorsal radiograph allowed changes to be visualized, but CT gave the clearest image of the fracture without a need for special positioning. CT was beneficial in the first case because it allowed detailed visualization of the fracture not provided with traditional radiography. In the second bird, the fracture displacement was radiographically apparent, which negated the need for additional imaging.
Simple transverse femoral neck fractures in mammals can often be stabilized with lag screws, divergent Kirschner wires, or total hip replacement. (6) These fractures are associated with high complication rates because of the location of the fracture. Avascular necrosis of the femoral head, implant failure, the need for long-term immobilization of the affected limb, the inability to achieve reduction or stabilization, degenerative joint disease, osteoporosis of the femoral neck, and sepsis are reported complications in both animals and humans. (7-9) Most avian species have pneumatic femurs with cortices that are thinner than those of mammals. (10) The pneumatic medullary canal and thin cortices make birds poor candidates for a total hip replacement or divergent Kirschner wire stabilization. In addition to potential complications related to surgery, primary repair and healing require 3 to 6 weeks of confinement and or non weight bearing on the affected limb for bones to heal. (11,12) Allowing the limb to heal without surgery would result in excess callus formation and lead to degenerative joint disease, permanent lameness, and decreased mobility.
In both human and veterinary patients, FHO has been performed for disorders of the coxofemoral joint and femoral neck. Humans undergoing unilateral FHO procedures experienced both cessation of pain and return to function, although abnormal gait and limb-length differences were common. (13,14) Total hip prosthetics have replaced FHO procedures as the preferred method to treat hip disease in humans; however, FHO remains a viable salvage procedure for small mammals with coxofemoral joint disease, including degenerative joint disease, hip dysplasia, Legg-Calve-Perthes disease, recurrent luxations, and irreparable fractures. (15) Femoral head and neck excision arthroplasty has previously been reported in avian patients for treatment of chronic coxofemoral luxation, open comminuted femoral neck fracture, and osteoarthritis. (4,16-18) The avian coxofemoral joint differs from that of domestic mammals in that, birds, like humans, bear all of their weight on the pelvic limbs, whereas quadruped mammals bear less than half of their weight on the pelvic limbs (approximately 40%). (19) This biomechanism is possible because of a shorter and thicker femoral neck that articulates with the dorsal rim of the acetabulum, the antitrochanter. The antitrochanter serves as a brace to prevent abduction of the hind limb and to decrease stress placed on the femoral head during bipedal locomotion. (20) In addition, the femoral head and neck of birds have a more acute angle of inclination, reported in 1 source as approximately 90[degrees], compared with the 130[degrees]-150[degrees] angle found in domestic mammals? Despite these differences, previous reports of birds undergoing unilateral FHO indicate acceptable results, including cessation of pain and return to function. (17-18) These results were duplicated in the 2 cases presented in this report.
An FHO entails removing the entire femoral head and neck. Without the articulation between the femur and the acetabulum, the hind limb musculature is essential in supporting the pelvic limb. Early limb use after surgery is important in the formation of a pseudoarthrosis as well as in maintaining muscle mass and range of motion. (21) Therefore, use of the limb and physical therapy are recommended as soon as possible after surgery. (21) In previous reports of FHO to treat disorders of the coxofemoral joint in avian species, the affected limb was immobilized for 10 or more days after surgery, either through placement of an Ehmer sling or restricting activity. (4,13,17,18) An Ehmer sling holds the leg in flexion with the hip in abduction and internal rotation, which is helpful after reducing hip luxations. In our opinion, the use of an Ehmer sling is generally contraindicated after FHO. Immobilization can lead to muscle atrophy and fibrosis, and results in decreased range of motion and a poor functional outcome. In the 2 birds in this report, the affected limbs were not immobilized and early use of the limb was promoted.
Early return to near-perfect function, including full weight bearing, good range of motion, and use of the foot, is optimal for successful release of free-ranging species that present with leg and hip injuries. Often these patients lose condition during convalescence while in captivity. Pododermatitis is common in raptors and waterfowl housed in captivity, especially when weight bearing is affected. (22,23) Severe pododermatitis warrants treatment and can lead to prolonged hospitalization, with the possibility of euthanasia if the lesions cannot be resolved. For this reason, minimizing the bird's time in captive care facilities is imperative. The goose described in the second case developed significant pododermatitis that threatened its releasability. The pododermatitis was likely due to the heavy-bodied nature of the bird, the orthopedic dysfunction in the contralateral limb, and the extended time in captivity to allow for original fracture healing. In both cases, FHO to manage a femoral neck fracture was selected to provide a rapid return to function when compared with other fracture repair options, which required up to 3-6 weeks of confinement during postoperative convalescence.
A diagnosis of femoral neck fractures can be challenging when using standard radiographic techniques. However, radiographs taken with the affected limb in neutral positioning and CT were advantageous in diagnosing the minimally displaced femoral neck fracture in the first case. The use of CT should be considered if a femoral neck fracture is suspected but not identified radiographically. In avian patients, FHO is well tolerated and allows for a pain-free status for the bird as indicated by a rapid return to function, especially important in successful release of free-living birds to their natural habitat. The birds described in this report did not have restriction of their affected limb and did not require prolonged confinement. Both were allowed rapid return to function and demonstrated resolution of pain. Femoral head ostectomy is a good option for treatment of birds with femoral neck fractures and should be considered the treatment of choice for free-living birds.
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Anne Burgdorf-Moisuk, DVM, Julia K. Whittington, DVM, R. Avery Bennett, DVM, MS, Dipl ACVS, Mike McFadden, MS, DVM, Mark Mitchell, DVM, MS, PhD, and Robert O'Brien, DVM, MS, Dipl ACVR
From the Department of Veterinary Clinical Medicine, Veterinary Teaching Hospital, University of Illinois at Urbana-Champaign, 1008 W Hazelwood Dr, Urbana, IL 61802, USA. Present address (Burgdorf-Moisuk): Veterinary Medical Teaching Hospital, University of California Davis, One Shields Ave, Davis, CA 95616, USA.