Treatment of acute onset lameness in a juvenile male whooping crane.

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Treatment of acute onset lameness in a juvenile male whooping crane.

Donna Bear-Hull

Curator of Birds

Jacksonville Zoo and Gardens

370 Zoo Parkway

Jacksonville, FL 32218

Abstract

After an intense thundershower on 31 August 2007, a male Whooping Crane (

Grus americana)

held at the Jacksonville Zoo and Gardens (JZG) exhibited non-weight bearing lameness of the right leg. Physical examination did not identify any luxations or dislocations, but the stifle had reduced extension capability.

Radiographs revealed no obvious fractures, but anti-inflammatory treatment and cage rest failed to improve function in the leg. After consultation with a veterinary orthopedic surgeon, exploratory surgery was performed with the conclusion that a pre-existing healed fracture of the fibula had reduced the range of motion in the right stifle and was contributing to the current problems with limb extension. . Surgical excision of a portion of the fibula by the orthopedic surgeon restored normal extension of the stifle joint and the ability of this crane to bear weight on the right leg. However, the bird remained unable to extend the toes and was bearing weight on the dorsal surface of the foot, resulting in a deep abrasion on the top of that foot. It was hypothesized that soft tissue trauma during the initial storm and also possibly associated with the surgical procedure was interfering with the bird’s ability to extend the toes. Attempts to tape and splint the foot and toes in the correct position showed promise for improving the situation, but were difficult to maintain and too rigid to accommodate the normal biomechanical movements of the lower limb. A flexible, prosthetic boot was devised and applied leading to the bird bearing weight normally on the fully extended plantar aspect of the foot while still allowing some movement of the toes. The bird continued to gradually improve and after two months and sixteen days the prosthesis was removed. The crane continues to have essentially normal function of his right leg and foot.

Background

Two juvenile whooping cranes hatched in June 2006 and raised at the International Crane Foundation for the International Whooping Crane Recovery Program were slated to be a part of the Direct Autumn

Release (DAR) program. Both birds were costume-reared and had no human contact as per the requirements of the program. During the course of rearing these birds both were determined to have leg deformities that rendered them unfit for release. The Jacksonville Zoo and Gardens (JZG) submitted an application to acquire these whooping cranes from the program and after a thorough review process were granted the permit to house the birds. The JZG made required modifications to an existing enclosure that included enlargement of the yard, removal of heavy vegetation, the addition of electric fencing to keep predators out, as well as a barn for housing the cranes during times of need as per the requirements for participating in the Whooping Crane Captive Recovery Program.

The two birds arrived at JZG on 7 October 2006 and were immediately introduced to human contact. The staff had access to the costumes used for rearing, but determined that removing the birds safely from the crates would be too difficult while wearing the costumes. The birds did not react adversely to their first human contact. While in quarantine, the costumes were worn for approximately a week, but the birds seemed to show very little distress at the sight of humans and thus costume use was discontinued.

Quarantine exams were performed on both birds 3 January 2007. A set of thorax/abdomen (VD and lateral) as well as hock radiographs (VD and lateral) were taken on each bird to determine the extent of the abnormalities and to provide baseline data on the health of the animals in question for future reference. The radiographs of the male’s legs showed noticeable abnormalities. Visibly the right tibiotarsus is enlarged just distal to the tarsal joint. The radiographs of this area show “an unusual radiographic appearance, with well-defined edges to the mass but a moth-eaten, radiolucent appearance

to the mass itself. The appearance of this lesion just distal to the proximal growth plate suggests that the mass is composed of retained islands of cartilage matrix from the growth plate that have undergone only partial calcification and remodeling. The tarsal joint appears to be normal in shape and joint spacing.”

(per clinical medical record) No fibular fracture was mentioned in the medical records at this time, though upon later review, the fibular spur was visible though not clearly defined. This fracture appeared to have been a proximal segment of fibula that, after a transverse fracture at the proximal third of the fibula, healed at a perpendicular angle to the long axis of the tibia.

The juvenile whooping cranes were introduced to their new exhibit on 5 February 2007. The lengthy stay in the quarantine facility was due to the fine-tuning of the modifications being made to the exhibit. The birds adapted quickly to the new sights and sounds of the zoo. Due to the age of the birds and the novelty of human contact in all of its various forms, the decision was made to lock the birds in the barn overnight to eliminate any possibility of injury or attack while limited staff was available on grounds to monitor the birds. The crane barn was similar to the quarantine facility in size and the birds reacted positively by walking in and feeding in the barn overnight. This decision was extremely beneficial with regards to the treatment of the injured crane later in the year.

Injury

At nearly 17:00 hours Eastern Standard Time on 31 August 2007 the male whooping crane was found completely non-weight bearing with the right leg held flexed slightly back from the normal position. The bird was immediately immobilized for examination and radiographs were taken. No lesions were present in the films and a perpendicular spur of an old fibular fracture is noted as present at the stifle. The fibular fracture is also discernable in the quarantine radiographs though not specifically noted in the records.

The earlier partial calcification of the tibiotarsus appeared more solid at this examination. The crane was placed on Meloxicam, a non-steroidal anti-inflammatory drug and given a vitamin E injection.

Two days of anti-inflammatory treatment failed to improve function in the leg. After consultation with veterinary orthopedic surgeon Dr. Tom McNicholas, DVM as to causes for the lack of stifle extension an exploratory surgery was performed on 6 September 2007. The proximal segment of the fibula was thought to hinder normal extension possibly due to the tip of the fracture segment contacting or being incarcerated by muscle and tendon. This fibular fracture segment was surgically excised. Full extension of the leg at the stifle was restored. The bird was placed on antibiotics and NSAIDS given orally by the keeper staff. Cage rest was prescribed so the male was kept locked in the barn. The female crane was extremely distressed by being on exhibit alone so the decision was made to hold her in with the male.

This calmed both birds considerably.

Although the surgery corrected the function of the stifle joint, the bird was only able to stand by knuckling the right foot and the hock seemed hyper-extended. The lack of foot control suggested possible nerve or other soft tissue damage to the lower limb.

Treatment

Treatment involved daily antibiotics as well as NSAIDs given orally by the keeper staff. Adjustments had to be made in the presentation of medications as the crane grew quickly wary of medicated items and in some instances would not take medication orally. The most common vehicle for getting the oral medications into the crane were mice, however; once the bird got particular, changing almost daily between grapes, crickets, and mice proved most successful. The bird was restrained manually and injected intramuscularly if oral medications were refused.

Post-operatively, the bird was holding the right leg in normal conformation under the body, with some weight bearing shown on the leg. The foot was held flexed and the weight was borne on the dorsum of the foot.

As the knuckling of the foot could lead to trauma a “splinting” or more accurately supporting was performed to partially extend the toes in order to facilitate return to more normal function of the foot. Tape was attached to the distal portion of each of the three toes holding them in a mostly extended position.

After twenty-four days of cage rest inside the barn, both cranes were allowed supervised yard time. The yard time was to help strengthen the weakened tendons of the stifle and hopefully help to restore function of the hock and lower foot. The bandages were being changed very frequently and by the 31 st

day it was decided to tape the foot in the knuckled position for one week to try to help the damaged tissues in the hock and possibly the foot align properly. The bird was already exhibiting lesions on the dorsal surface of the right foot so extra padding with bandaging material was put in place to protect this area. One week later, the crane was re-bandaged and splinted in the extended position. At this time it was observed that the bird was growing more and more capable of flexing and extending the 2 nd

and 4 th

digits. The 3 rd

digit was still unresponsive and as taping and splinting progressed, appeared to be the main cause for the knuckling behavior. After many different types of taping and splinting were tried, including the use of tongue depressors as well as thermoplastic splint material, the need for a flexible but semi rigid splint was determined. Several ideas were discussed based on the required normal biomechanical function and movement of a long-legged bird, though the actual production of such a splint or support was not conceived. The bird continued undergoing cage rest with monitored time outside. Treatment continued for the pressure lesions that had developed on the plantar aspect of left foot secondary to increased weight-bearing and the dorsal aspect of the right foot due to the knuckling over and weight-bearing trauma.

Prosthesis

In efforts to explore development of a prosthesis or support for the affected foot, a local artist and contract fabricator for the JZG, Mike Lincoln, was contacted by the Curator of Birds to discuss development of a prosthesis. Mr. Lincoln was informed of the need and asked about possible solutions to the problem. He was also taken to the crane exhibit to observe the normal function of a cranes foot to help explain the situation. The Curator of Birds explained that a flexible prosthesis was needed that would keep the long third digit extended when the foot is placed on the ground, but soft enough that the bird could flex the toe if needed, as during hock flexion and if return of function did occur. Mr. Lincoln requested to make a mold of the foot in order to proceed with an idea that he had. It was agreed upon, since regular bandage changes and examination was necessary to make certain positive progress was being made with the bird’s health.

A mold was made using modeling clay while the bird was under anesthesia for bandage change and health check. It was determined that a complete mold of the 3 rd

digit and the upper portion of the foot was all that was needed to accomplish the desired prosthesis. The other toes were only included partially to denote location. The mold formation took very little time and was quickly completed. The impaired foot was re-splinted with thermoplastic material and the bird was returned to his enclosure.

Mr. Lincoln created a cast from the mold using a two-part epoxy material. He then used Vaseline as a mold release agent on the cast and began work on the prosthesis. The prosthesis was made of 2 inch fiberglass tape that was completely covered in 100% silicone. The tape was then wrapped around the

cast to form a relatively thick, soft, but flexible boot. Mr. Lincoln did add coloring to the silicon at a request from the Curator of Birds to make the prosthesis match the nor mal coloration of the bird’s leg.

The silicone prosthesis was cut from the cast and then fitted to the bird’s foot. Additional cuts were necessary to make sure that the fit was correct and that the pad of the foot was exposed and yet the toe was encased properly. Once fitted, silicone had to be applied to the cut portions to be certain that the fiberglass underneath would not rub or cut the bird and to maintain the waterproof seal the silicon gave the boot as well as decrease the potential for the fiberglass layers to delaminate. The added silicone cured for 24 hours and the boot was placed on the crane’s foot and affixed to the tibiotarsus with black cable ties. The bird was released in to the yard and was immediately able to bear weight and walk in a semi-normal fashion.

The bird was allowed to wear the prosthesis for two days before a recheck to confirm the fit. Upon rechecking the prosthesis, it was observed that there was very minor abrasion on the 2 nd

phalange of the 4 th toe and rubbing where the proximal aspect of the boot met the tibiotarsus. Measurements of the tibiotarsus with calipers were made so that Mr. Lincoln could adjust the cast and make a closer fitting prosthesis. The boot was replaced on the bird until the replacement prosthesis could be produced. The rubbing was minor and the original boot was maintained for a month before replacement. The second closer fitting boot was placed on the crane 17 November 2008. The bird was allowed full access to the yard during the day from this point forward except during thunderstorms and overnight.

On 4 January 2008

,

the Curator of Birds noticed a peculiar gait to the male whooping crane, but only when running. After monitoring for several days, the curator felt that the boot was actually beginning to impede the crane’s ability to walk and was starting to cause a slightly different gait. The veterinary staff was asked to consider the idea of taking the boot off to see how the bird had progressed. The decision was made to remove the boot on 12 January 2008 on a day when the crane could be monitored full-time by staff. After the boot’s removal, the crane was able to plant his foot firmly and walk in an almost normal manner. The only visual evidence that the gait was not normal was a slight swing of the right leg wide to the right when walking, as well as the bird’s inability to scratch his head with the right foot.

Results

The whooping crane’s injury was multi-faceted and extreme. Eliminating each part of the underlying issue piece by piece was the major factor in returning the function of this bird’s leg. The removal of the fibular fracture “spur” at the stifle joint was the start that allowed the full flexion of the leg and the other soft tissue injuries to become apparent. Each section of the leg was addressed individually until the only problem remaining was the soft tissue damage to the foot. The development of the soft prosthesis was the key to returning function to the foot. The boot gave the birds toe semi-rigid support, but allowed the bird to move more and more as the strength in the foot increased. When the boot was finally removed there was a tear at the flexion point of the toe that appeared because of the bird’s increasing ability to flex the toe. The prosthesis was able to provide rigidity when needed and flexibility once the tendons and muscles had returned function. The soft style of the boot produced no lesions and allowed the bird to more fully displace his weight taking some of the pressure off of the overworked left leg. This type of prosthetic boot can be easily duplicated and quickly reproduced based on each specific bird and injury. .

The key to the resolution of the bird’s limb problem was the flexible nature of this type of prosthesis. It allowed the normal biomechanical movements during flexion and extension of all components of this bird’s long leg. This prosthesis would enhance the ability of dealing with soft tissue and foot injuries in many species of birds and manage the resultant problems temporarily or, if needed, permanently.

Acknowledgements

I would like to thank Dr. Nikolay Kapustin, Dr. J. Andrew Teare, and Dr. Tom McNicholas for their expertise and veterinary care. I would also like to thank Mike Lincoln for the development of the prosthesis as well as the Jacksonville Zoo and Gardens Bird Staff. Robin Lentz, Sheri Robb, Shannon

Irmscher, Samantha Kerns, Mike Toloczko, Aimee Kephart, Danielle Buck, and Jennifer McClosky for their ability to maintain both these birds throughout this trying experience.

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