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Key Ring Fixator: A Novel External Fixation Technique for Avian Long Bone Stabilization.

Abstract: A 12-year-old blue-fronted Amazon parrot (Amazona aestiva) of unknown sex (case 1) and a 14-year-old female hybrid Catalina macaw (Ara ararauna x Ara macao) (case 2) were evaluated and treated for an open tarsometatarsal fracture and a tibiotarsal fracture, respectively. In case 1, 1 month of external coaptation resulted in a delayed union, significant osteolysis, and presumptive osteomyelitis, which led to the decision to treat with a key ring fixator. In case 2, a key ring fixator was chosen for fracture repair because of presumed resistance to destruction by the bird. In both cases, fractures were stabilized with makeshift circular external fixators composed of key rings, K-wires, orthopedic wire, and acrylic resin. After key ring fixator removal, radiographs confirmed complete bone healing. Both patients had acceptable function of the affected limbs 5 years (case 1) and 2 years (case 2) after their procedures. The key ring fixator described in this report is a viable option for fracture repair in pelvic limbs of moderately sized birds (300-1500 g).

Key words: fracture, tarsometatarsus, tibiotarsus, avian, blue-fronted Amazon parrot, Amazona aestiva, macaw, Ara ararauna x Ara macao

Clinical Report

Case 1

A 12-year-old, 355-g blue-fronted Amazon parrot (Amazona aestiva) of unknown sex was presented to the Avian and Exotic Animal Service of Washington State University on an emergency basis with injuries to legs several hours after being attacked by 2 macaws. On physical exam, the parrot was alert and responsive but was unable to stand on either leg. The left leg had an open wound on the lateral aspect of the tarsometatarsal area and marked instability proximal to the foot, consistent with an open tarsometatarsal fracture. The left foot appeared normal, with positive sensation and some motor function--grip strength was not assessed. The right foot had a large wound centered over the tarsometatarsophalangeal joints, through which one could see the joint surfaces of a luxated second digit and subluxated third digit. The luxated second digit was attached to the foot by a relatively small band of soft tissue, was cold, and appeared dark and dry. The dark color was presumed to be a combination of local hypoxia and dried blood. The third digit was also cold and darker in color than the rest of the foot. Through the wound, the proximal end of PI of the third digit appeared dry. Neither clinicopathologic evaluation nor bacterial culture were performed because of financial constraints. Initial treatment included butorphanol (1.7 mg/kg IM), meloxicam (0.17 mg/kg PO), and enrofioxacin (12.8 mg/kg IM).

The next day, the bird was mask induced with 4% isoflurane and maintained on 2%--2.5% isoflurane delivered by face mask for whole-body radiographs and wound treatment. The radiographs confirmed a mildly comminuted short oblique mid-diaphyseal fracture of the left tarsometatarsal bone (Fig IA), as well as tarsometatarsophalangeal joint luxations in the right foot. The wound over the left tarsometatarsal bone was cleaned, debrided, and covered with a non-adherent sterile dressing (Telfa Ouchless Non-Adherent Pad, Covidien, Mansfield, MA, USA) with a thin layer of silver sulfadiazine cream. The tarsometatarsal fracture was stabilized with a splint constructed as a soft padded bandage with paper clip reinforcement. The wound over the right tarsometatarsophalangeal joints was cleaned and debrided. The second digit of the right foot was amputated. The right foot wound was bandaged in a similar manner as the left with a soft-padded bandage. Enrofloxacin (11.7 mg/kg PO) and meloxicam (0.15 mg/kg PO) were administered.

Over the course of the next month, treatment with enrofloxacin (12 mg/kg PO q24h) and meloxicam (0.15 mg/kg PO q24h) continued. The wounds of both legs were treated by regular splint/ bandage changes with wound cleaning and debridement (daily bandage changes initially, gradually decreasing to twice a week by 4 weeks after injury). Primary wound dressings consisted of nonadherent dressings with either silver sulfadiazine cream or hydrogel spray with hypochlorous acid (Vetericyn VF HydroGel spray, Innovacyn Inc, Rialto, CA, USA) depending on the appearance of the wounds and the clinician's preference. The right foot had signs of progressive necrosis of the third digit and of the skin surrounding the base of the first digit. By the second week, the first phalanx of the first digit became exposed as the surrounding skin and scant subcutaneous tissue around the phalanx devitalized and was debrided. Minimal signs of wound healing were observed by 3 weeks, and attempts to preserve vitality of the digits were finally abandoned. The first digit was amputated because of the lack of surrounding soft tissue to support the bone, and the necrotic third digit was also amputated, leaving one digit (digit 4) on the right foot. After digit amputation, the right foot wound healed readily. Healthy-appearing granulation tissue was seen in the wound during the next bandage change, and a few sutures were placed to bring the skin edges together. The remaining small open wound had a dry scab adhered by the end of week 4. The wound was allowed to heal under this scab during subsequent weeks, without further treatment or debridement. In the left foot, starting 3 weeks after the injury, caseous material (pus) was intermittently noted in the left tarsometatarsal wound. Financial constraints prevented bacterial culture.

One month after presentation, the bird was anesthetized with isoflurane as above for recheck radiographs of the left leg. The radiographs revealed osteolysis and osseous proliferation surrounding the previously described middiaphyseal fracture of the left tarsometatarsal bone, consistent with a delayed union (Fig IB). The osteolysis associated with the fracture ends was thought to be caused by osteomyelitis, bone atrophy, or both.

Four days later, surgical stabilization was planned. Before surgery, a variety of sizes of standard metal key rings were acquired from a hardware store and sterilized with an autoclave (Fig 2). Glycopyrrolate (0.01 mg/kg IM) and butorphanol (1.7 mg/kg IM) were administered 30 minutes before induction. Anesthesia was induced with 3% isoflurane in oxygen delivered by face mask. Once induced, the bird was intubated with a pediatric 3-mm Cole endotracheal tube, and an IV catheter was placed in the right superficial ulnar vein. An isotonic balanced electrolyte solution (Normosol-R, Hospira Inc, Lake Forest, IL, USA) was administered IV at 10-20 mL/kg per hour during surgery. A circulating warm water blanket was used to reduce hypothermia.

After isolating and preparing the left leg and foot for surgery, a lateral approach to the tarsometatarsus was performed, with the skin incision located just dorsal to the crust covering the recently healed wound. (1) The fracture ends were debrided with rongeurs. With the incision open to aid in visualization/palpation of the tiny fracture fragments, two 0.89-mm (0.035-in) Kirschner wires (K-wires) were driven through the proximal bone fragment and both skin surfaces with an electric driver at slow speed. After the first K-wire was placed, a key ring was selected that would encircle the leg with approximately 1 cm clearance from the skin surface. This key ring (30-mm internal diameter) was held up against the first K-wire while the second K-wire was driven between the turns of the key ring and through the bone, at an approximately 90-degree angle relative to the first K-wire. Two more K-wires and a second 30-mm (internal diameter) key ring were placed in a similar manner, engaging the distal bone fragment. The fracture gap was lavaged and packed with a slurry made with the patient's blood and synthetic bone graft particulate (Consil, Nutramax Laboratories, Lancaster, SC, USA), and the skin was closed with 4-0 poliglecaprone 25 (Monocryl, Ethicon, Somerville, NJ, USA) in an interrupted pattern.

The foot was held in alignment by an assistant while the K-wires were bent at right angles against the outer edges of the rings so that the parts of the K-wires that extended beyond the rings acted as connecting rods between the rings (Fig 3). Short lengths of 24-ga orthopedic wire were used to secure each wire-ring junction. The entire length of each connecting rod, especially the junctions, was covered with acrylic resin (Self-Cure Orthodontic Resin, Patterson Dental, St Paul, MN, USA) dispensed through a syringe in near-putty phase and allowed to harden around the metal to lock the fixator in place. Any wire tips that extended beyond the acrylic resin were clipped. In final form, the construct resembled a circular external ring fixator with 1 ring engaging each bone fragment. Postoperative radiographs were not taken on the day of surgery but were postponed until the first postoperative recheck. A soft padded bandage was placed around the left foot and fixator with a plan to remove the bandage after a few days. Meloxicam (0.15 mg/kg PO q24h) and enrofloxacin (12 mg/kg PO q24h) were administered the evening after surgery.

During the next month, treatment with meloxicam and enrofloxacin continued. Bandages on both feet were periodically changed, and the wounds and surgery site were inspected. Although the right foot wounds were considered healed during this time, a soft bandage was maintained because of concern that the foot (which had only 1 digit) would develop sores if the bandage were left off. On the left foot (the side with the fixator) the surgical incision healed normally (sutures removed on day 10); however, the small wound beside the surgical incision opened and produced a discharge periodically. Therefore, the decision was made to maintain a bandage on this side as well. During this period the bird was bright and talkative and ambulated on both bandaged feet using the bill to assist.

One month after key ring fixator placement, the bird was anesthetized with isoflurane as above and recheck radiographs were taken (Fig 1C). The fracture region was difficult to visualize because of superimposition of hardware, and several oblique projections were taken to view the fracture gap adequately. Apposition of the fracture fragments was good, with bridging callus noted in association with the fragments. However, an incomplete fracture line was still evident on multiple projections. Wounds on both feet had healed and were no longer producing discharge; the bandages were left off of both sides. The digits of the left foot had reduced range of motion, and passive range of motion exercises were instituted (gentle flexion-extension of the left foot digits for 5-10 minutes, 1-2 times a day). During the subsequent month, the bird ambulated on the right foot and on the caudal edge of the left fixator, and used the bill to assist.

Two months after key ring fixator placement, the bird was anesthetized with isoflurane as above and radiographs were repeated. Progressive osseous bridging was apparent, and the fracture line was no longer visible. The key ring fixator was removed, and subsequent radiographs demonstrated osseous callus spanning the fracture. Compared with the initial radiographs, there was slight overall shortening of the tarsometatarsus (Fig ID).

Immediately after fixator removal, the bird was reluctant to bear weight on the left foot unless encouraged to do so. The bird was able to ambulate on both feet using the bill to assist, and the legs had normal function and tone. When standing and walking on the left foot, the bird bore weight on the tarsus and on the caudal/plantar surface of the foot, including the dorsal aspect of the first and fourth digits because the foot tended to remain in a "closed" position. The bird was able to open the foot voluntarily, but only partially, and had a present but weakened ability to grip. Superficial sensation (assessed with a placing response test and a leg withdrawal reflex test) seemed normal. Given the voluntary motor function, pain sensation was not tested. The bird was discharged with instructions to continue passive range of motion exercises on the left digits and to inspect both feet for sores daily.

Two months after fixator removal, the bird readily ambulated on flat surfaces on both feet and with the digits of the left foot held in a more normal position so that weight was born on the plantar or lateral surfaces of all 4 digits. The bird was able to flex and extend the digits with improved grip strength compared with the previous evaluation. Digit range of motion was markedly improved but still less than normal. At last follow up 5 years after surgery, the owner reported that the bird was still bearing weight properly on the left foot and was able to use the left foot for walking, perching, and gripping.

Case 2

A 14-year-old, 1.22-kg female Catalina macaw, a hybrid between the blue-and-gold macaw and the scarlet macaw (Ara ararauna x Ara macao), was presented to the Avian and Exotic Animal Service at Washington State University for a fracture of the left pelvic limb. It had occurred earlier that day after jumping out of a towel and landing on the floor during a veterinary visit. The patient had a history of increased egg laying and had been receiving nutritional supplementation with dairy foods. On initial evaluation, the bird was alert and responsive and would not bear weight on the left leg. No wounds were associated with the fracture. A complete blood count revealed leukocytosis. Plasma biochemical abnormalities consisted of hypoalbuminemia (1.1 g/dL; reference interval, 1.2-3.2 g/dL) and increased creatinine phosphokinase concentration (902 U/L; reference interval, 50-400 U/L) (in-house reference intervals, Antech Diagnostics, Fountain Valley, CA, USA).

The bird was initially treated with butorphanol (1 mg/kg IM q8-12h) and meloxicam (0.15 mg/kg PO) and was placed in an oxygen cage (40% oxygen) to keep it calm and to restrict movement. The next day, radiographs were taken while under isoflurane anesthesia. Results revealed a long oblique fracture of the proximal diaphysis of the left tibiotarsus with an associated small cortical fragment, subjectively normal long bone quality, and no eggs within the coelomic cavity (Fig 4A). After radiographs were obtained, a temporary soft padded bandage was placed around the left leg.

The day after initial presentation, the bird was anesthetized for surgical stabilization. It was pretreated with butorphanol (1 mg/kg IM), doxapram (2 mg/kg IM), and cefazolin (40 mg/kg IV) and then induced and maintained under anesthesia with isoflurane as above. Lactated Ringer's solution (10-20 mL/kg per hour IV) was administered through a catheter in the left superficial ulnar vein during surgery. While under anesthesia, leuprolide acetate (400 mg/kg IM) was also administered. A circulating warm water blanket was used to reduce hypothermia.

A key ring fixator was placed in closed fashion. After isolating and preparing the left leg for surgery, the leg was held in traction and alignment, and the fixator was placed in a similar manner as in case 1. Tiny stab incisions into the skin with a #11 blade facilitated K-wire penetration through the skin. K-wires (0.89 mm; 0.035 in) and short segments of 24-gauge orthopedic wire were used. Key rings were selected to allow about 1 cm of space between the ring and the skin. Two 38-mm (internal diameter) rings were used in the proximal fragment, and two 34-mm (internal diameter) rings were used in the distal fragment to create a key ring fixator with 4 rings (Fig 3). Special attention was made to holding the limb in normal alignment while the K-wires were bent into connecting rods and while the acrylic resin was hardening. A bandage was not replaced over the limb or fixator.

Two days after surgery, the bird was anesthetized with isoflurane for postoperative radiographs. Again, the fracture region was difficult to visualize because of superimposition of hardware, so several oblique projections were taken. There was poor apposition of the fracture ends and mild misalignment with the distal fragment displaced caudally and proximally. Because of the stability of the construct and good soft tissue coverage of the fracture, the decision was made not to revise the fixator but to allow the bone to heal in mild misalignment.

During the healing period the bird received daily meloxicam (0.15 mg/kg PO q24h) and enrofloxacin (15 mg/kg PO q24h). Gentle passive range of motion was performed on the digits of the left foot for 5 minutes q24h. While the key ring fixator was in place, the bird was forced to hold the left leg in abduction and tended to place weight on the inner edge of the fixator while the foot touched the ground in an abnormal position (with the fourth digit pointing forward).

Fracture healing was monitored with recheck radiographs 3, 7, 10, and 12 weeks after surgery (Fig 4). During the 3- and 7-week rechecks, no bony callus was observed, and mild diffuse osteopenia was noted. During the 7-week recheck, the lowest ring of the fixator was removed to reduce construct stiffness and to allow the bird to bear weight more normally on its left foot. After the 7-week recheck, progressive healing was noted at the facture site, and the fixator was completely removed 12 weeks after surgery. Radiographs taken without the construct 12 weeks after surgery revealed a healed fracture with slight shortening and caudal bowing of the left tibiotarsus. After fixator removal, the bird ambulated on both legs with the left foot held in a normal weight-bearing position. At last follow-up 2 years after surgery, the owner reported that the bird had normal function of the leg and foot.

Discussion

The key ring fixator described in this report is a modification of the circular external fixator (CEF) technique used in small animal and human fracture repair. Our experience in these two cases led to several observations about the benefits and limitations of using the key ring fixator in birds.

In case 1, we developed the key ring fixator technique to engage the very short fragments of bone that remained of the fractured tarsometatarsus. The short fragments were a result of osteolysis that occurred during a month of external coaptation (splinting). Splinting is an acceptable method of stabilizing tarsometatarsal fractures in birds, although the complete or partial digit immobilization that results from splinting can lead to fracture callus incorporating flexor and extensor tendons. (2, 4) In case 1, frequent bandage and splint changes were necessary for wound care; this caused instability, which probably contributed to the delayed/non-union. Given the caseous material seen at 3 weeks after injury, we suspect that bacterial infection also played a role in the bone's failure to heal. When there is sufficient bone, a type II linear external fixator (full pin fixation) is the preferred method for tarsometatarsal fractures. (3,5,6) Other reported fixation methods used in the tarsometatarsus include cross-pins, type I linear external fixator with a specialized tube device, and a conventional CEF in an African sacred ibis (Threskiornis aethiopicus). (4,7-9) These methods would not have been possible in case 1 because of lack of bone (without incorporating adjacent bones and immobilizing adjacent joints). We found that the key ring fixator was easy to apply and provided the needed stability despite very small bone fragments.

A synthetic bone graft particulate (Consil) was used in case 1 for its bone stimulatory and antimicrobial properties. Consil is a commercially available bioactive glass that has been shown to stimulate bone generation in small animals and is typically used in periodontal surgery. (10) Bioactive glass and ceramics are inorganic, non-species-specific materials that contain calcium, phosphorus, sodium, and silica. (11,12) When placed in an aqueous environment, the material's surface develops a hydroxycarbonate apatite layer that bonds to living bone and is biologically active. Traditionally, bioactive glass materials were thought to be solely osteoconductive (providing a scaffold for cellular migration), but recent research has established osteoinductive properties (with the capacity to induce new bone formation) and antimicrobial properties. (11-13) To our knowledge, the use of bioactive glass in a bone defect has not been previously reported in birds. However, a similar material, hydroxyapatite, has led to successful bone healing in a critical defect model in pigeons (Columba livid) (14) Other bone stimulatory materials reported for use in bone defects in birds are an autogenous bone graft taken from the carina, an allogenic demineralized bone matrix, a ratite cancellous bone xenograft, and bone morphogenetic protein-2. (15-19)

In case 2, we chose the key ring fixator for its toughness. Our experience from case 1 had left us with the impression that the finished key ring fixator is extremely resistant to damage, and the patient in case 2 had a history of escaping its Elizabethan collar and being destructive when unsupervised. The key ring fixator, once complete, has a 3-dimensional shape that resembles the reinforcement bar cage (rebar cage) within concrete columns used in construction. Windows through the cylinder-shaped external frame are small enough that a psittacine beak has trouble getting inside to access the wires. There is, however, no evidence to support our impression that the key ring fixator is more resistant to damage than a linear external fixator. Several case series report successful use of linear external fixators in similar situations, with no report of bird-induced damage. (7,20-23)

Avian tibiotarsal fractures have also been stabilized with linear external fixators of various configurations (with or without intramedullary pin tie-in), including a linear external fixator with a specialized tube device, a locking plate, a dynamic compression plate with intramedullary pin (IM pin) and cerclage, titanium microplates, interlocking nails, and a hybrid fixator (CEF in distal fragment, linear external fixator in proximal fragment). (7, 20-27) A type II linear external fixator would have been a good option in case 2 and would have had the advantage of better fracture visibility on postoperative radiographs (craniocaudal projection). An IM pin (in combination with another device) would have led to better fracture reduction and alignment in case 2, although IM pins are sometimes associated with problems when used in the tibiotarsus. Unless tied into an external fixator, IM pins are prone to migration and removal by the patient. They can also cause stifle osteoarthritis associated with placement, migration, or both. (22) Additionally, there is a theoretical concern that IM pins can damage the endosteal blood supply, which is of particular importance in avian fracture healing. (28)

In general, CEFs have several advantages over other fracture fixation methods, including versatility, the ability to engage very small bone fragments securely, minimally invasive placement that minimizes soft tissue damage, and, when placed correctly, excellent biomechanical properties for bone healing. (29) Although not demonstrated in this study, effective CEF placement should be possible with even smaller wires than those used in linear external fixators in birds, because CEF construct stiffness depends more on ring diameter than on wire diameter. (30) This property would be of particular benefit in some situations for birds that have thin, relatively brittle bones and narrow safe corridors. Unfortunately, even the smallest commercially available CEF systems come with rings that are too large for most birds. When they are combined with conventional connecting bars and clamps, they become undesirably bulky and heavy relative to patient size. We found that standard hardware store key rings served as strong and lightweight replacements for conventional CEF rings. Additionally, by fashioning connecting rods out of K-wires and acrylic resin, we were able to create lightweight fixators around the fractures.

A brief review of CEF principles is warranted to highlight the adjustments made for the key ring fixator. Although frame designs vary, a standard CEF frame for long bone fracture fixation is composed of 4 rings (2 on each bone fragment), each fixed to the bones with 2 tensioned small-diameter wires. The rings are connected to each other with threaded connecting rods. During weight bearing, the wires resist 4-point bending (rather than cantilever bending in linear external fixators), and the axial stiffness of the construct depends more on ring diameter than on wire diameter or wire tension. (30) Thus, rings should be chosen that are as small as possible while still allowing room for soft tissue swelling and pin care. Key rings come in a variety of sizes, making it easy for surgeons to accommodate these criteria. Regarding wire diameter, 1.0-mm (0.039-in) wires have been recommended for CEF in cats and dogs <10 kg. (29) Given that pin sizes of 0.71-1.14 mm (0.028-0.045 in) are commonly used in birds for linear external fixators, it follows that even smaller wires could be used in birds receiving a key ring fixator. (31) In our cases, we used 0.89-mm (0.035-in) K-wires. Although not demonstrated in this report, we believe that the use of smaller wires (eg, 0.71 mm or smaller) would have been equally successful at providing the necessary rigidity in these cases. It may also have improved the biomechanical properties of the key ring fixators by allowing for axial micromotion. Finally, standard-sized CEF constructs require pin tensioning to counteract the initial wire displacement that occurs with axial load. Wire tensioning is probably not necessary, however, for rings smaller than 50 mm (internal diameter). We did not tension the wires when constructing our key ring fixators. (30)

In this report, the key ring fixators provided rigid fixation for weight-bearing bones of the pelvic limb in psittacine birds weighing 355-1220 g. Standard key rings are available in many other sizes (Fig 2), and we envision that the fixator could be helpful for birds outside this range, especially larger birds. As bird size increases, however, a conventional external fixator system becomes feasible and has the important advantage of adjustability. A conventional CEF has been used to stabilize the tarsometatarsus of a 1.5-kg African sacred ibis, although the relatively large size and shape of the ibis tarsometatarsus gives more room for the somewhat bulky CEF rings. (9) A hybrid fixator consisting of a distal conventional CEF ring and proximal linear external fixator has been used in the tibiotarsus of a 5-kg bald eagle (Haliaeetus leucocephalus). (27)

Notably, the key ring fixator frame in case 1 did not comply with general principles of CEF because there was only 1 ring (2 wires) per fragment. Generally, when placing a CEF, at least 3 wires should be used per fragment to counteract bending. (29) When a bone fragment is too short for 2 rings, a third wire can be placed and secured to posts or rods that extend from the initial ring. This was not performed in case 1 because the surgeon judged the small bone fragments unable to accept a third wire without fracturing. Although the fixator led to successful healing in case 1, the frame design was not ideal.

While load bearing should be restored as quickly as possible in all species, this is particularly true for bipedal animals such as birds. (32) External fixators should always be placed in such a way that they allow for early weight bearing. The fixators used in our cases inhibited normal weight bearing. Although this was unavoidable in case 1 because of the distal nature of the fracture, a better design could have avoided this problem in case 2. In conventional CEF, when ring bulk near the body or near a joint would inhibit motion, half-rings or a hybrid fixator (distal rings, proximal linear fixator) should be chosen. In case 2, the use of something shaped like a half ring instead of the most proximal key ring would have avoided the abduction that caused weight bearing on the fixator rather than the foot.

The limitations of the key ring fixator in case 2 requires a critical evaluation of the technique. First, unlike conventional CEF, the key ring fixator was not adjustable once the acrylic resin had hardened. Postoperative radiographs in case 2 revealed poor fracture end apposition and imperfect alignment. A conventional CEF would have allowed for easy adjustment of the frame to correct alignment. However, to adjust the key ring fixator would have required near complete dismantling and rebuilding of the frame.

We believe that the construct built in case 2 was too stiff and that this contributed to a prolonged healing time. A unique benefit of conventional CEF is that when placed correctly, it allows for axial micromotion during weight bearing, which can stimulate bone healing. (29) In case 2, we were disappointed in the lack of bony callus visible on the 3- and 7-week radiographs and suspected that 1) the frame was too stiff, and 2) the frame did not allow the patient to place weight on the foot correctly. Removing the most distal ring at week 7 decreased stiffness and allowed better weight bearing, which led to more normal healing. In future cases, key ring fixator stiffness can be reduced with the use of smaller wires (0.71 mm or smaller) or fewer wires (3 wires per fragment rather than 4) or by incorporating the key ring into a linear-circular hybrid external skeletal fixator.

One benefit of external fixation is the ability to perform staged disassembly. (33) Staged disassembly can speed bone healing by transferring load from the fixator to the healing bone. (34) Several reports involving fracture fixation in birds used staged disassembly, which is easy to perform in constructs involving IM pins, linear external fixators, or both. (8,20,22,27) If a conventional CEF had been used in case 2, construct stiffness could have been decreased at 7 weeks after surgery by removing wires associated with 2 of the rings (1 from the proximal and 1 from the distal fragment) or by removing single wires from various rings.

Staged disassembly is a limitation of the key ring fixator compared with conventional CEF. We found that staged disassembly of the key ring fixator was difficult to perform. Destabilizing our key ring fixator construct was limited to removing the distalmost ring by cutting the K-wires and acrylic resin that connected the fixator to that ring. It was not possible to cut the proximal key ring for removal without the risk of loosening the delicate wire-bone interfaces of the construct. Also, it was exceedingly difficult to cut and remove individual wires from proximal rings, because the wire cutters would not fit into the spaces between the frame components.

Both conventional CEF and the key ring fixator obstruct radiographic visualization of the healing fracture. The use of plastic or carbon fiber rings would rectify this issue and might also facilitate staged disassembly of the external fixator.

Despite their limitations, we believe the key ring fixators resulted in positive outcomes for the 2 cases described in this report. These cases demonstrate that this technique provides sufficient stabilization of a fracture without disrupting the surrounding soft tissue or bone callus. The technique is especially useful for fractures with small bone fragments. Additionally, the anesthesia time was short, and the technique was straightforward and inexpensive. The use of key rings as external fixators is a viable option for successful fracture repair in the avian pelvic limb.

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Anna Katogiritis, DVM, Sabrina L. Barry, DVM, Dipl ACVS-SA, and Nickol Finch, DVM

From the Department of Small Animal Clinical Sciences, Virginia Maryland College of Veterinary Medicine, 215 Duck Pond Drive, Blacksburg, VA 24061, USA (Katogiritis, Barry); and the Department of Veterinary Clinical Sciences, Washington State University, 100 Grimes Way, Pullman. WA 99164. USA (Finch).

Caption: Figure 1. Craniocaudal (top row) and mediolateral (bottom row) radiographs of a left tarsometatarsal fracture (arrow) in a 12-year-old Amazon parrot. (A) The day after trauma. (B) After 4 weeks of splinting, there is osteolysis and osseous proliferation at the fracture site, consistent with a delayed union. (C) Four weeks after key ring fixator placement, the fracture is difficult to visualize because of hardware superimposition. (D) Immediately after key ring fixator removal (8 weeks after key ring fixator placement), the fracture is bridged by bone.

Caption: Figure 2. Key rings of various sizes acquired before surgery for key ring fixator construction used for fracture repair in 2 parrots. Two 30-mm (internal diameter) rings were chosen for case 1, and 34- to 38mm (internal diameter) rings were chosen for case 2.

Caption: Figure 3. Illustrations of key ring fixator placement to stabilize a tibiotarsal fracture in the Catalina macaw from Figure 1 (case 2). (A) K-wires (asterisk) are placed through the skin to engage the bone fragments. Key rings (arrow) are placed such that the K-wires are either adjacent to a key ring or passing through the turns of a key ring. (B) With the leg held in alignment by an assistant, the length of each K-wire that extends beyond a key ring (asterisk) is bent against the outer edge of the key ring to serve as a connecting rod for the fixator. Short segments of fine orthopedic wire (arrowhead) are twisted around each K-wire-key ring junction. (C) Acrylic resin (shaded area) is placed around the connecting rods and junctions and allowed to harden. (D) Photograph of the completed key ring fixator in case 2.

Caption: Figure 4. Craniocaudal (top row) and mediolateral (bottom row) radiographs of a left tibiotarsal fracture (arrow) in a 14-year-old female Catalina macaw. (A) The day after trauma. (B) Seven weeks after key ring fixator placement, the fracture is difficult to visualize because of hardware superimposition, but tibiotarsal misalignment can be appreciated. (C) Ten weeks after key ring fixator placement. The distal ring has been removed from the fixator. (D) Immediately after key ring fixator removal (12 weeks after key ring fixator placement; 5 weeks after the distal ring was removed), the fracture is bridged by bone.
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Title Annotation:Clinical Report
Author:Katogiritis, Anna; Barry, Sabrina L.; Finch, Nickol
Publication:Journal of Avian Medicine and Surgery
Date:Jun 1, 2019
Words:6457
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