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Surgical Repair of a Cleft Palate in an American Bison (Bisonbison)Author(s): Larry J. Minter, D.V.M., M.S., William M. Karlin, D.V.M., Marisa J.Hickey, D.V.M., and Christopher R. Byron, D.V.M., Dipl., A.C.V.S.Source: Journal of Zoo and Wildlife Medicine, 41(3):562-566. 2010.Published By: American Association of Zoo VeterinariansDOI: http://dx.doi.org/10.1638/2010-0018.1URL: http://www.bioone.org/doi/full/10.1638/2010-0018.1

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SURGICAL REPAIR OF A CLEFT PALATE IN AN AMERICAN

BISON (BISON BISON)

Larry J. Minter, D.V.M., M.S., William M. Karlin, D.V.M., Marisa J. Hickey, D.V.M., and

Christopher R. Byron, D.V.M., Dipl., A.C.V.S.

Abstract: A 4-mo-old bison (Bison bison) was evaluated and treated at a university veterinary hospital for a

cleft defect in the hard and soft palate. Using a mandibular symphysiotomy approach, the palatal defect was

repaired with a Z-plasty pattern in the soft palate and mucoperiosteal flaps in the hard palate. A small area of

dehiscence in the rostral aspect of the hard palate, and aspiration pneumonia, were complications, but the bison

calf recovered with medical management. Even though this surgical procedure has a high potential for

complications, the described technique allowed return to normal feeding and resolution of the aspiration

pneumonia by 14 mo postsurgery.

Key words: Bison, cleft palate, congenital defect, palatoschisis, palatoplasty.

BRIEF COMMUNICATION

A 4-mo-old, 65 kg, male, intact bison (Bison

bison) was referred to the Large Animal Clinic at

the University of Illinois, College of Veterinary

Medicine, with a 1-day history of anorexia and

colic. At presentation, the calf was no longer

demonstrating signs of colic, but the rumen was

distended and the intestines appeared dilated

during ultrasound examination. A bilateral,

mucopurulent nasal discharge was noted, which

the owner stated had been present for a few

months. Oral examination revealed a midline

cleft involving the entire length of the hard and

soft palates.

The bison calf was anesthetized using carfen-

tanil citrate (Wildnil, Wildlife Pharmaceuticals

Inc., Fort Collins, Colorado 80524, USA;

0.005 mg/kg i.m.) and xylazine (X-ject E, IVX

Animal Health Inc, St. Joseph, Missouri 64503,

USA; 0.05 mg/kg i.m.) for endoscopic (Pentax

Endoscope model EG 2901, Pentax Medical

Company, Montvale, New Jersey 07645, USA)

examination, which revealed a 3-cm-wide cleft

extending from the rostral hard palate caudally

through the entire soft palate.3 Anesthesia was

reversed using naltrexone (Trexonel, Wildlife

Pharmaceuticals Inc.; 0.5 mg/kg i.v.) and tolaz-

oline (Tolazine, Akorn Inc., Decator, Illinois

62522, USA; 2 mg/kg i.v.). Thoracic radiographs

revealed a bronchointerstitial-to-alveolar infil-

trate in the caudal ventral lungs indicative of

aspiration pneumonia. The bison calf was treated

with ceftiofur sodium (Naxcel, Pfizer Animal

Health, Pfizer Inc., New York City, New York

10017, USA; 2 mg/kg, i.m., s.i.d for 7 days).

Three days after being admitted to the hospital,

the bison calf was anesthetized for surgical repair

of the cleft palate. The animal was sedated using

midazolam (Novaplus, Hospira Inc., Lake For-

est, Illinois 60045, USA; 0.75 mg/kg i.m.) and

medetomidine (Domitor, Pfizer Animal Health,

Pfizer Inc.; 0.04 mg/kg i.m.), and anesthesia was

induced using ketamine (Ketathesia, Butler An-

imal Health Supply, Dublin, Ohio 43017, USA;

2.3 mg/kg i.m.). The animal was placed in dorsal

recumbency and a tracheotomy was performed.

A 9.0-mm endotracheal tube was passed through

the tracheostomy site for maintenance of anes-

thesia with isoflurane (Isothesia, Butler Animal

Health Supply) in oxygen.

Using a mandibular symphysiotomy approach

that has been described in foals, the defect was

exposed.2,6,7,12 A skin incision was made from the

basihyoid bone to the mandibular symphysis and

through the ventral lip to allow for adequate

exposure. A plane of dissection approximately

1.5 cm axial to the right mandible was followed,

and the mylohyoideus, geniohyoideus, and genio-

glossus muscles were transected. The soft tissues

were separated and oral mucosa incised to expose

the mandibular symphysis. The tongue was

reflected laterally with a Ribbon retractor, and

Finochietto rib spreaders were used to separate the

mandible and improve surgical access to the palate.

The defect in the hard palate was repaired by

creating mucoperiosteal flaps based at the pala-

From the University of Illinois, College of Veterinary

Medicine, Department of Farm Animal Reproduction,

Medicine and Surgery, 1008 West Hazelwood Drive,

Urbana, Illinois 61802, USA (Minter, Hickey); and

University of Illinois, College of Veterinary Medicine,

Department of Equine Medicine and Surgery, 1008

West Hazelwood Drive, Urbana, Illinois 61802, USA

(Karlin, Byron). Correspondence should be directed to

Dr. Minter (Ljminter@yahoo.com).

Journal of Zoo and Wildlife Medicine 41(3): 562–566, 2010

Copyright 2010 by American Association of Zoo Veterinarians

562

tine artery on the right and left sides. The flaps

were elevated, transposed axially to cover the

hard palate defect (Fig. 1), and were sutured

together with 2-0 polyglactin (Vicryl, Ethicon

Inc., Somerville, New Jersey 08876, USA) in a

continuous pattern. Lateral tension was relieved

with interrupted vertical mattress sutures using 1

polydiaxone (PDS, Ethicon Inc.). Axial tissue on

both sides of the soft palate portion of the cleft

was incised and elevated to create a free

oropharyngeal flap. The soft palate was closed

in two layers, with the Z-plasty pattern used in

the oral-side closure.10 The first layer apposed the

mucosa of the nasopharyngeal side of the

elevated tissue with a simple continuous suture

pattern using 2-0 polyglactin. The oropharyngeal

flap was incised, and the right and left halves

were transposed to create the Z-plasty.10 The

oropharyngeal tissue was closed in a simple

continuous pattern using 2-0 polyglactin. Poly-

methylmethacrylate was used to cover the hard

palate to protect the suture site during healing

(Fig. 2).

The mandibular osteotomy was secured using

one 6.5 mm, 24-mm-long cancellous screw that

was placed using a hole predrilled with a 4.5-mm

drill bit. A piece of 20-gauge cerclage wire was

placed around the incisors to help appose the

mandibular symphisis. Closure of the soft tissue

was achieved in five layers and, lastly, the skin

Figure 1. Mucoperiosteal flaps were elevated and transposed to cover the hard palate defect.

MINTER ET AL.—CLEFT PALATE REPAIR IN AN AMERICAN BISON 563

was stapled (Precise, 3M, St. Paul, Minnesota

55144, USA). To reinforce the lip incision,

tension-relieving sutures were placed using 1

polydiaxone in a vertical mattress pattern.

Postextubation, a nasogastric tube was placed

to assist with feeding during the recovery period.

Recovery from anesthesia was uneventful, and

the calf received morphine (Morphine, Baxter

Healthcare Corporation, Deerfield, Illinois

60015, USA; 0.24 mg/kg, i.m., t.i.d. for 24 hr),

flunixin meglumine (Banamine, Schering-Plough

Animal Health Corp, Union, New Jersey 07083,

USA; 1.1 mg/kg i.v., s.i.d. for 96 hr) and ceftiofur

sodium (2 mg/kg, i.v.) prior to becoming sternal.

The calf received lactated Ringer’s fluids (35 ml

per kg per hr) during and postsurgery for 24 hr.

On the following day, the calf was changed to

buprenorphine (Buprenex, Reckitt Benckiser

Pharmaceuticals, Richmond, Virginia 23235,

USA; 0.003 mg/kg i.v., b.i.d. for 96 hr).

Eighteen days postsurgery, the bison calf was

anesthetized as before for endoscopic examina-

tion of the surgery site. The polymethylmethac-

rylate plate covering the hard palate was removed

Figure 2. Polymethylmethacrylate was used to cover the cranial hard palate for protection of the suture site

during postsurgical healing.

564 JOURNAL OF ZOO AND WILDLIFE MEDICINE

at this time. There was dehiscence of the rostral

3 cm of the hard palate. The necrotic tissue was

cleaned and debrided with a diluted betadine

scrub. The nasogastric tube and skin staples were

removed. Anesthesia was reversed using naltrex-

one (0.5 mg/kg i.v.) and tolazoline (2 mg/kg i.v.).

After removal of the nasogastric tube, the calf

had access to grass hay and a calf creep feed.

After ensuring that it was eating, the calf was

discharged 19 days after surgery. The owners

were instructed to give tulathromycin (Draxxin,

Pfizer Animal Health, Pfizer Inc.; 2.5 mg/kg i.m.

once every 7 days for 6 wk).

Ten weeks after surgery, endoscopic examina-

tion, under general anesthesia as before, revealed

healing of the palate defect. The wire around the

incisors was removed, but the cancellous screw

was left in situ. The area of dehiscence at the

rostral aspect of the hard palate was present, but

smaller than previously noted. The calf exhibited

no clinically relevant problems, and surgical

correction of the defect was not pursued.

Fourteen months postsurgery, the calf was

gaining weight and was within normal limits.

Cleft palate or palatoschisis in large animals is

an uncommon congenital defect that results in

clinical signs ranging from dysphagia, rhinitis,

bilateral nasal discharge, and aspiration pneu-

monia.5,8,9,13 The condition is typically apparent

shortly after birth because the animal is observed

dripping milk from its nares while nursing. The

defect is derived from the failure of embryological

closure of the palatal folds along the midline and

can involve both the hard and soft palate.9

Although the cause of cleft palate formation in

large animals is unknown, in small animals and

humans it appears to be a multifactorial interac-

tion involving heritable and environmental fac-

tors.9

Surgical correction of the cleft defect, and

euthanasia, are currently the only options for

animals with cleft palates when the palatal defect

is large or aspiration of milk is significant.4

Surgical closure requires adequate exposure to

the site, while avoiding excessive trauma to the

surrounding tissues and minimizing tension on

the repair, which can be difficult to achieve.2 If

the defect is small and aspiration of food material

is minimal, it is advised to delay surgery while

monitoring the animal closely so that aspiration

pneumonia does not go undetected.4 The major

advantage of delaying surgery is that the oro-

pharynx will be larger, allowing for better

surgical manipulation and more precise surgical

repair.4 Delaying surgery was not necessary for

this case because the calf was not diagnosed until

4 mo of age, and its oropharynx was of a

sufficient size to provide adequate exposure.

Critical evaluation of the patient is required to

select the best method of repair for a cleft palate.

Numerous techniques for the surgical approach

to palatal defect closure have been described

including laryngotomy, mandibular symphysiot-

omy, pharyngotomy, and intraoral repair, with

or without bilateral buccotomy, or a combination

of techniques.2,6,7,12–14 Mandibular symphysioto-

my provides the best exposure to the hard and

soft palate, allowing more precise suturing and,

thus, was selected for this case.12 If the defect is

large, involves the hard palate, or if inadequate

palatal tissue is present at closure, as it was in this

case, buccal mucosal and mucoperiosteal sliding

flaps improve the chances of successful repair.1,4,11

The surgical repair of a cleft palate is

considered a salvage procedure and has a high

rate of complications.4 Complications associated

with palatoplasty include dehiscence of the

repaired palate or lower lip, aspiration pneumo-

nia, osteomyelitis, nonunion of the mandible, and

soft tissue infection.1,2,4 Prognosis of surgery is

affected by the size of the defect, the amount of

the soft palate involved, involvement of the hard

palate, and presence of aspiration pneumonia.2,4

Postoperative complications, and the persistence

of clinical signs, are common and have been

reported with all the surgical techniques.1,2,4

Multiple surgeries are often required to achieve

complete healing.4

The surgical repair of the cleft palate in the

bison calf was successful on the first attempt,

with only a small area of dehiscence in the rostral

aspect of the hard palate, despite the reported

poor success rates and the coupled complications.

The dehiscence in this bison calf may have

resulted from application of methylmethacrylate

on the hard palate, leading to local contact

trauma or allowing trapping of feed material at

the site of palatal closure. However, it is also

possible that, without the plate, more-extensive

dehiscence would have occurred. Alternatively,

the use of a free mucosal graft to augment the

repaired palate may have helped protect the

suture line; however, insufficient mucosa was

available for this technique. The mandibular

symphysiotomy provided adequate surgical ex-

posure and permitted more-precise suturing of

the hard and soft palate. In addition, the use of

an indwelling nasogastric tube for postoperative

feeding helped minimize soft tissue trauma to the

surgical site. Even though this surgical procedure

MINTER ET AL.—CLEFT PALATE REPAIR IN AN AMERICAN BISON 565

is fraught with complications, the described

technique was useful in this bison calf to allow

return to normal feeding and to reverse the

clinical signs of aspiration pneumonia by 14 mo

postsurgery.

Acknowledgments: The authors would like to

thank the University of Illinois, College of

Veterinary Medicine veterinary students for their

dedication and commitment to this case.

LITERATURE CITED

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Philadelphia, Pennsylvania. Pp. 277–280.

2. Bowman, K. F., L. P. Tate, L. H. Evans, and W.

J. Donawick. 1982. Complications of cleft palate repair

in large animals. J. Am. Vet. Med. Assoc. 180: 652–657.

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Received for publication 23 January 2010

566 JOURNAL OF ZOO AND WILDLIFE MEDICINE