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Oral anatomy

The mouth is the most rostral portion of the alimentarycanal. It is bounded laterally by the cheeks, dorsally by thehard and soft palates and ventrally by the mandible, tongueand mylohyoid muscles. It is a long cylindrical cavity andwhen closed is almost entirely filled by the tongue and teeth.The oral cavity communicates caudally with the oropharynxthrough the isthmus faucium.

The mucous membrane of the mouth is continuous at themargin of the lips with the skin and caudally with themucosa of the oropharynx. It is of squamous type with mul-tiple small papillae, which are the openings of the ducts ofthe labial glands. The lips are muscular folds surroundingthe orifice of the mouth. The angles of their union are calledthe commissures and are situated at the level of the firstpremolar cheek teeth.

The cheeks are muscular in nature and the gums arecomposed of dense fibrous tissue united intimately with theperiosteum of the mandible, maxilla and with the dentalstructures which it surrounds.1 Motor innervation of thecheeks and lips is provided by the seventh and oral sensationby the fifth cranial nerves.

The hard palate is bounded rostrally and laterally by thedental arcades. Although its mucous membrane is smooththere are 18 curved transverse ridges along its length.1 Theblood supply to the mouth is well developed and formed fromthe facial and buccinator arteries. There is a rich venousplexus beneath the mucosa of the hard palate supplied bythe palatine arteries and veins.

The tongue is a muscular structure situated in the floor ofthe oral cavity between the horizontal rami of the mandiblesand is supported by a muscular sling formed by the mylohyoidmuscles. Caudally it is attached to the hyoid apparatus. It iscovered with a squamous epithelium and the dorsal surfaceis covered with a variety of papillae. On either side of its rootsits a dense aggregate of lymphoid tissue, the lingual tonsils.The blood supplied to the tongue is by the lingual andsublingual branches of the external maxillary artery and itscorresponding veins. Motor supply to the tongue is by thetwelfth cranial nerves. Sensation to the rostral two-thirds ofthe tongue is provided by the fifth and seventh cranial nervesand to the caudal one-third, by the lingual branch of theninth cranial nerve.1

There are three pairs of salivary glands which have ductsentering the oral cavity. The parotid ducts enter the mouthvia papillae situated approximately at the level of the fourthupper premolar teeth (108 and 208). The mandibularducts open into the floor of the mouth at the level of thelower canine teeth (304 and 404) via flattened papillae,the sublingual caruncles. The sublingual glands enter theoral cavity by a series of approximately 30 ducts in the sub-lingual fold. Other smaller salivary glands are foundthroughout the mouth.1

Oral examination

Injuries to the oral cavity can be assessed by visual inspec-tion of the mouth. Obvious external injuries to the lips andcheeks are readily assessed; however, lesions within the oralcavity itself can be more difficult to evaluate. Examiningthe mouth can usually be performed by gently grasping thetongue and rotating it within the mouth at the level of theinterdental space.2 Great caution should be observed if thereis any possibility of a lingual injury. A pen torch may be usedto illuminate the oral cavity, but a good head lamp is muchbetter as it allows the clinician the freedom to use bothhands, enabling careful palpation of dental arcades, gums,tongue, cheeks and other oral structures. Great caution mustalways be observed when inserting a hand into a horse’smouth as serious injury to the examiner may result fromHaussmann’s equine teeth. A much better and safer optionis the use of an oral speculum such as a Haussmann’s gag, or avariety of similar types of specula which are readily available.Although such a speculum can be used in accommodatingpatients without need for sedation, it is preferable whenexamining oral injuries to sedate the patient to reduce the riskof operator injury and to facilitate the accurate assessment ofthe extent of the injury. In the presence of a severe oral injurythe pain associated may preclude use of a metal speculum,even in a heavily sedated patient, and necessitate an exami-nation under general anesthesia. A speculum permits a safemeans of examining even the most caudal part of the oralcavity, although accurate visualization may be more difficultbecause of the intrusion of soft-tissue structures in the area.

An endoscopic examination of the nasal passages andnasopharynx is of great value in assessing full thickness

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7The Management of Oral TraumaTRC Greet, BVMS, MVM, Cert EO, DESTS, Dip ECVS, FRCVS,Beaufort Cottage Equine Hospital, Cotton End Road, Exning,Newmarket, Suffolk CB8 7NN

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defects of the hard or soft palate and the identification ofmost pharyngeal foreign bodies which protrude through theintrapharyngeal ostium. An endoscopic examination of theoral cavity may be carried out in a sedated horse with aspeculum in place. However, the risk of instrument damagemeans that extensive intra-oral endoscopy should probablybe carried out under general anesthesia. The endoscopiclight allows not only inspection of an injury, but facilitatesthe lavage of blood and debris from the area, improving theview. In addition the illumination it affords may permit thesurgical repair of some otherwise inaccessible wounds.

Radiographic views of the head are important in assessingthe extent of oral injuries when damage to bones or teeth issuspected. Lateral or oblique radiographic views obtainedwith the horse in the standing position are helpful. Intra-oralviews of the mandibular or maxillary incisor arcade may beof particular value in demonstrating injuries to these areas.Such views require the horse to be sedated heavily and itmay be preferable with more fractious patients to carry thisout in the anesthetized horse (see Chapter 14).

The use of oral barium sulfate may permit the identifica-tion of an oronasal fistula and plain radiographic viewsshould demonstrate the presence of metallic foreign bodieswithin the tongue, cheeks, or gums.3,4 It should be remem-bered that artifactual shadows can be created by restrainingdevices such as head collars. A rope halter is probably themost satisfactory means of restraining a horse for radio-graphic examination of the head. Assessing functionaldisturbances of swallowing requires a dynamic study whichis best achieved by using image intensification or fluoro-scopy. Barium sulfate can be used as a contrast agent eithermixed together with food or water, or administered as asuspension on its own.

Oral trauma

A variety of injuries affecting the oral cavity are commonlyencountered in equine practice. Lacerations of the lips maybe associated with wire or bit injuries and occasionally arecaused by kicks or other forms of direct trauma (Fig. 7.1).Horses are prone to grasping fixed objects such as doors,mangers, or buckets and this may lead to fractures of therostral mandible or maxilla, usually associated with avulsionof incisor teeth. Occasionally the incisor teeth may be dam-aged without significant injury to the surrounding bone andthis is particularly likely when deciduous teeth are involvedin such injuries.

Injuries may occur to the interdental space where the bitsits. This may be the result of overzealous handling by a rideror by the use of strong restraining devices such as a chiffney.Such injuries are often accompanied by ulceration of thegum just rostral to the premolar teeth and in some casesdamage to the underlying bone may result in sequestration(Fig. 7.9). More severe fractures of the mandible or maxillamay occur at this level as a result of direct trauma.

Injuries to the tongue are less common but may also followoverzealous restraint using a chiffney. Severe laceration andeven transection of the tongue is not unknown under suchcircumstances. Perhaps more commonly an injury to thelingual frenulum may be the consequence of grasping thetongue during an oral examination, or if used as a methodof restraint for fractious patients. There was one famousaccount of a farrier`s assistant who literally pulled a horse`stongue out of its mouth while restraining the animal forshoeing! Less severe injuries can be caused by stable hooksor clips, twisted or loose deciduous premolar teeth, or byforeign bodies in the feed.

Injuries to the hard or soft palate are less common but mayfollow the incorrect or careless use of dental instruments,for example during wolf tooth extraction. Iatrogenic soft-palate damage may follow surgical treatment of horses forepiglottic entrapment or dorsal displacement of the softpalate.

Injuries to salivary structures are rare. However, traumato the face may result in damage to the parotid salivarygland or duct with consequent development of a salivaryfacial fistula. Such animals can produce a spectacular jet ofsaliva during eating!

The oral environment and healingof oral injuries

The oral cavity is exposed to the external environment andis bathed in saliva. Saliva is composed of mucus and serousfluids containing electrolytes and proteinaceous enzymes,for example amylase. It facilitates mastication and degluti-tion. Saliva also contains glycosaminoglycans and glyco-proteins, which are responsible for its lubricant characteristics.Saliva is secreted in large volumes (50 ml/hour from a singleparotid gland) as a result of mastication and its production iscontrolled by the autonomic nervous system.5 The mouth isfrequently in contact with food material and subjected to themovements of mastication. In the wild, horses graze almostcontinuously except when they are asleep. There are largenumbers of bacteria within the oral cavity, many of whichare anerobic. All these factors have a considerable bearingon the effects of injury to the mouth and to the managementof oral trauma.

Many minor lacerations to the lips, cheek and tongue willheal by second intention without the need for surgicalreconstruction, because of the excellent oral blood supply.However, in certain situations surgical reconstruction of oralstructures is indicated.6–8 Typically, injuries involving com-plete laceration of the lips, cheeks or tongue are suitablecandidates for repair, as second intention healing oftenproduces cosmetically and functionally unacceptableresults.9 Management of such injuries should involve carefulwound preparation with particular attention given to theremoval of foreign material. In most cases oral lacerationsquickly become filled with food as well as clotted blood.

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This material should be first flushed away to allow a moreaccurate assessment of the extent of the injury. Localizedinfections may subsequently produce necrosis at the site andin some cases bone fragments may become sequestrated.Careful debridement of the wound must be performed. If thewound is extensive or inaccessible in the standing horse, ageneral anesthetic should be administered to ensure thatappropriate wound assessment and management can becarried out. Removal of all necrotic material and debris isessential, producing healthy tissue margins which bleedfreely. The use of pulsating lavage (i.e. Water Pik system)has been recommended as it is very effective in removingdebris without creating further trauma.10 When significantinjury to the lips or cheeks occurs, the wound should beclosed in layers.7,8 At the very least, separate skin andmucosal closure is required. In most cases, a third layerwhich incorporates the muscular tissue and fascia shouldalso be repaired using absorbable suture material. Tissuesshould be reconstructed with accurate anatomical apposi-tion of the layers and it is preferable to use non-absorbablesuture material or stainless steel staples in the skin.

Following repair, care must be observed in preventingself-mutilation by the horse. While most horses seemunbothered by sutured facial wounds, others seem to findsuch wounds irritating. In these circumstances cross-tying,the use of a muzzle or even long-term sedation can be helpfulin preventing failure of the repair or worsening of theoriginal damage.

The management of horseswith facial trauma

A horse with major facial trauma should be assessed imme-diately for life-threatening respiratory obstruction, nasalhemorrhage and any other indication of major dysfunctionsuch as neurological or ocular disturbance. Obviously main-tenance of a clear airway must be a priority and insertionof an emergency tracheotomy tube should be carried outwithout delay if required. Most nasal hemorrhage associatedwith facial injury will cease without need for particular action.Secondary infection of the paranasal sinuses is commonfollowing facial fracture and appropriate antibiotics shouldbe administered, and sinus lavage may also be of benefit aspart of any treatment regime.

Multiple radiographic projections should be obtained inhorses with major facial wounds to assess the extent ofosseous or dental injury, the presence of radiodense foreignbodies,3,4 and before any attempt is made to repair theoverlying soft tissues.

Consideration of tetanus prophylaxis, insurance status anddiscussions with the owner or agent regarding the likely prog-nosis for restoration of function, are clearly priorities that mustbe addressed before undertaking any major surgical treatment,or the administration of a general anesthetic to a patient.However, sometimes it may not be possible to make an accurate

assessment of the full extent and implications of the injuryuntil the horse has been anesthetized and inspection of moreinaccessible structures carried out. This should be explained inclear terms to owners, agents and insurers, whenever they areinvolved, to minimize the risks of misunderstanding or evenlitigation at some later date. Consultation with appropriatespecialists such as an ophthalmologist or neurologist may beappropriate before any treatment is undertaken.

While the treatment of facial and oral trauma follows thegeneral principles of wound and injury management inother anatomical areas, injuries to mouth, nose, and eyes inparticular seem to be associated with greater client concernand feelings of anthropomorphism, than with injuries else-where. The clinician must therefore be prepared to respondto questions about cosmetic as well as functional outcome insuch patients.

Treatment of specific soft tissueinjuries

The lips and cheeksInjuries to the lips and cheeks are readily treated by suturingafter preparation of the wound. If the wound is extensiveand involves all the layers of the lips, the horse should eitherbe sedated heavily or given a general anesthetic. The wound

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Figure 7.1. A severe laceration to the upper lip that extends into theoral cavity. This a full thickness laceration which should be repairedin layers.

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should be repaired as accurately as possible in layers(Figs 7.1–7.5).

It is preferable to repair the oral mucosa first and thisshould be done with simple interrupted or a continuousappositional suture of absorbable material such aspolyglactin 910 or polydioxanone (Fig. 7.2). Knots can betied within the oral cavity. In most cases a second layer

which should incorporate the muscular and fascial tissueshould be carried out using the same material (Fig. 7.5A).Lavage of the incision with polyionic fluid containing solublepenicillin at this stage will assist in minimizing the risk ofwound sepsis. The skin of the lips can then be repaired usingnon-absorbable suture material such as monofilamentnylon, sheathed polyamide or stainless steel skin staples.In small lesions the use of a simple interrupted pattern ispreferred. However, with more extensive defects simple inter-rupted sutures should be alternated with vertical mattresssutures to assist in relieving the tension on the wound andtherefore reducing the risk of subsequent dehiscence. Ifextensive cheek laceration has occurred, great care must betaken in determining whether the parotid salivary duct isinvolved. If this structure has been damaged its wall may berepaired to prevent the development of a facial salivaryfistula. Similarly, extensive facial wounds may have involvedinjury to branches of the facial nerve. Major facial nerveinjuries carry a poor prognosis and may result in permanentdisability.

When the edge of the lip is involved, care should be takento restore complete function by accurate repair of the orbic-ularis oris muscle. The close proximity of the skin, mucosaand musculature at this site potentially creates excessivemovement at the suture line, particularly during prehen-sion. To minimize this the skin and mucosa should be sepa-rated from the adjacent musculature at the edges of thewound7,8 (Fig. 7.4).

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Figure 7.2. Repair of the oral cavity using a continuous suture of4 metric polyoxanone, same case as in Fig. 7.1.

Figure 7.3. An extensive laceration of the lower lip which also has afull thickness defect through the left cheek into the mouth. Figure 7.4. Separating the skin from the underlying musculature.

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This facilitates closure in layers and reduces the incidenceof dehiscence. The wound edges should be aligned accuratelyto ensure healing is satisfactory and to minimize the risk ofsubsequent dehiscence and consequent disfigurement,which might affect function.

Should the repair of a lip or cheek laceration subsequentlydehisce, the wound may be left to heal by second intention.However, if extensive defects develop (Fig. 7.5B) an attemptshould be made to carry out secondary repair of the wound.It may be necessary to use tension-relieving devices such asa quill of polythene tubing from a giving set for fluid admin-istration. These are incorporated into vertical mattresssutures to protect the wound from dehiscence. When carrying

out a secondary repair, it is of paramount importance to per-form radical debridement of necrotic material down tohealthy bleeding tissue. Creation of tissue planes prior torepair may also facilitate healing. In general the prognosisfor healing of lacerations to the lips and cheeks is very good.However, in those cases where secondary or tertiary repairis undertaken there may be a cosmetic blemish at thelip margin. Occasionally an orofacial fistula may remain(Fig. 7.5B).

The tongue and oropharynxInjuries to the tongue mostly involve lacerations caused bydamage from bits or restraining devices such as a chiffney.Minor splits to the tongue will heal readily without need forrepair. Occasionally a horse is examined which has previ-ously sustained a severe laceration of the tongue which hashealed without complication, leaving a large defect in itsdorsum or lateral border. Lacerations of the lingual frenu-lum, which usually occurs when excessive traction is appliedto the tongue, need not be repaired and usually heal withoutcomplication. However, most severe lacerations involvingthe body of the tongue are best managed surgically.8

The horse should be given a general anesthetic and thewound assessed carefully to ensure tongue viability. A gauzebandage may be used as an effective tourniquet when appliedcaudal to the wound. Gentle traction to it also allows goodexposure of the more caudal parts of the tongue.Glossectomy may be necessary if the tongue tip is consideredunviable and removal of tissue up to the level of attachmentof the frenulum is unlikely to affect function.8 Intravenousadministration of sodium fluoroscein has been recommendedas an aid to assessing lingual viability. The tongue can beexamined under a Woods lamp 5 minutes after injection of 4or 5 g of the compound.8 Oversewing the lingual body withsimple interrupted or a continuous suture of polyglactin 910or polydioxanone should be attempted after removal of thenecrotic tip. Severe lacerations are repaired using simpleinterrupted and vertical mattress sutures applied alternately(Fig. 7.6). The latter should incorporate a significant bulk oflingual musculature to take up some of the tension and toensure more satisfactory healing. All dead space should beobliterated if possible. Multiple layer closure may be required.It should be remembered that the tongue is very mobile andthe risk of wound dehiscence is significant unless care istaken to align the tongue correctly and to repair the injuryaccurately. If the injury is not dealt with in the acute situa-tion, a degree of necrosis and wound contamination mayoccur. In such circumstances all devitalized tissue must bedebrided carefully to minimize the risk of wound dehiscence.When placing vertical mattress tension sutures care must betaken to avoid damage to the lingual blood supply. Althoughthis is good, vascular compromise may result in necrosis ofthe tongue, particularly when the tip is involved. The dorsumof the tongue has a much stronger mucosa than its ventralaspect and suture retention is better in this site. Tensionsutures should therefore be placed in this area.6

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Figure 7.5. (A) Repair of facial musculature using a continuous sutureof 4 metric polydioxanone. (B) Although the lesion was repaired inlayers, partial wound dehiscence resulted in an orofacial fistula. Thiswas successfully repaired by a second operation.

A

B

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Lesions to the base of the tongue and the oropharynx aremuch more difficult to evaluate and certainly more difficultto repair due to their inaccessibility. However in mostcircumstances inaccessible wounds will heal well withoutthe need for repair. Daily lavage of the oral cavity with asaline solution may be of value in reducing wound contam-ination with food material.

Rarely, horses may be encountered which have developedsubepiglottal infections or granulomatous abscesses. Theseare presumably the result of earlier mucosal penetration oran injury which has been undetected. Surgical removal ofgranulomatous swellings at this site is difficult but may beachieved via an oral approach or through a ventral midlinepharyngotomy. This site is also prone to damage by ingestedforeign bodies, which are usually twigs or pieces of wood.In most circumstances affected horses show oral discomfort,dysphagia, inappetance, hyperptyalism and occasionallyepistaxis. Foreign bodies within the oropharynx can often bedetected by nasopharyngeal endoscopy as they frequentlyprotrude through the intrapharyngeal ostium. Foreign bodiesare usually retrieved manually with the horse under heavysedation or general anesthesia. No repair of the mucosalinjury is usually necessary. Parenteral antibiotics and non-steroidal anti-inflammatory medication should be adminis-tered for several days following removal of foreign bodiesfrom this region.

The hard and soft palatesInjuries to the hard palate are rare but may accompanysevere head trauma (Fig. 7.7). In some circumstances theremay be an underlying fracture of the palate which involvesthe palatine processes of the premaxilla and/or the maxilla.Mostly these can be left as open wounds to heal by secondintention. However, an oronasal fistula should be repairedsurgically. A suspected oronasal fistula may be confirmed bya combination of a thorough clinical and endoscopic exam-ination and by radiography after oral administration of

barium sulfate. While such a fistula may resolve by secondintention healing, surgical repair should be attempted if thesite is accessible. It may be possible to repair the defect bysimply suturing the palatal mucosa with interrupted suturesof polydioxanone (Fig. 7.8). If the injury can not be repairedadequately in this manner, it may be possible to close thedefect by creating a mucoperiosteal flap, or by makingtension-relieving incisions in adjacent portions of the palate.Care should be taken to avoid damage to the palatine bloodsupply.6

Post-repair feeding should be carried out by nasogastricintubation for the first 4 or 5 days to reduce the risk of suturedehiscence.

If the rostral portion of the skull is grossly unstablefollowing a maxillary or premaxillary injury, the fracturesmay require surgical repair (see Chapter 21). However, it issurprising how frequently horses with this sort of majorinjury respond successfully to conservative management.

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Figure 7.7. This horse sustained severe trauma to the maxilla whichresulted in a fracture of the premaxillary bone and laceration of thehard palate. There was direct continuity between the oral and nasalcavities.

Figure 7.8. This is the surgical repair of the injury illustrated in Fig. 7.7.The fracture has been reduced with cerclage wire after radicaldebridement of the site. The palate has been repaired partially usingsimple interrupted and vertical mattress sutures of 4 metric polydiox-anone. The horse made an uneventful recovery and the cerclage wirewas subsequently removed.

Figure 7.6. This severely lacerated tongue has been severed almostcompletely. The injury was repaired using simple interrupted suturesof 4 metric polydioxanone alternated with vertical mattress sutures ofthe same material. The wound healed by primary intention and thehorse regained normal use of its tongue.

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Congenital defects of the hard palate are uncommon andin the author’s opinion surgical repair is not indicated.Injuries to the hard palate and more specifically the palatineartery may follow removal of a wolf tooth or repulsion ofcheek teeth. In such circumstances moderately severehemorrhage may occur. Control of hemorrhage by pressureis usually effective. If there is a large enough defect it may bepossible to insert some gauze bandage packing.

It may become apparent that an oral wound is not healingas rapidly as might be expected. In some cases healing maybe accompanied by an exuberant granulation response.In such circumstances, bone or even dental sequestrationshould be suspected (Fig. 7.9). Obtaining the relevantradiographic projection may confirm this suspicion. Carefulexploration of the wound may produce the sequestrum andafter debridement and gentle curettage of the involucrumthe wound will usually heal rapidly.

Injuries to the soft palate are uncommon but may followattempted surgical treatment of the soft palate or adjacentstructures, such as in cases of epiglottal entrapment. In anattempt to divide axially the displaced mucosa using acurved bistoury, the soft palate may become inadvertentlydamaged. Full-thickness injuries to the soft palate inevitablyresult in the development of an oronasal fistula because ofcontamination of food and saliva. Surgical repair of suchinjuries should be attempted as soon as possible after theinjury has been identified. Access for surgical repair is very

limited. A general anesthetic should be administered and themouth opened maximally using an oral speculum. Goodlighting should be provided and the area may be examinedby a fiberoptic or videoendoscope to assess the extent of theinjury. Long-handled retractors should be used to depressthe base of the tongue and retract the cheeks in order to helpin evaluating the injury and in its subsequent repair. Long-handled needle holders, forceps and scissors are also of greathelp when attempting repair of such an injury. Separatingthe oropharyngeal mucosa from its overlying musculaturewill facilitate closure in two layers, enhancing the likelihoodof achieving first intention healing. Wherever possible at leasttwo layer closure should be attempted. The musculature andnasopharyngeal mucosa are closed as one, and the oropha-ryngeal mucosa as the other. The author prefers polydiox-anone as a simple, continuous suture for each layer.

Even though such defects may be closed effectively, dehis-cence is common. This is because of the highly mobilenature of the palate during mastication and deglutition, andthe presence of food and saliva within the oral cavity andoropharynx. It is not unusual for second and even thirdattempts at repair of full-thickness palatal defects to fail.However, small fistulae may heal spontaneously. As describedabove, feeding such cases by nasogastric intubation is impor-tant to reduce the risk of dehiscence of the suture line.Similarly, this method of feeding helps in the conservativemanagement of such a fistula and should be combined withmuzzling of the patient, in an attempt to reduce contamina-tion of the airway by food material.

Clefts and other defects of the soft palate are morecommon than those affecting the hard palate but in theauthor’s opinion are not suitable candidates for surgical repair.The affected animal should be destroyed if the degree of dis-ability (dysphagia or exercise intolerance) is more than slight.

Injuries to salivary tissueInjuries to the salivary glands may occur as a result of directtrauma. The parotid gland is the most vulnerable because ofits size and location behind the angle of the jaw. Suchinjuries can be repaired by wound debridement, cleansingand closure of the skin. Salivary cutaneous fistulae are rareafter this sort of injury.5

Injuries to the parotid duct are more common and areusually associated with direct trauma to the ventral borderof the mandible, at which point the duct crosses beforeentering the oral cavity. In some cases there may be littleevidence of an injury to the duct and there may be little needfor specific treatment as the wound may heal readily.

However, in a proportion of casest there is direct continu-ity between the duct and a skin wound. This often results inthe development of a salivary facial fistula. Such injuriesoften have the dramatic consequence of creating a profusedischarge of saliva during eating and mastication. Althoughsaliva tends to have an inhibitory effect on healing, most ofthese wounds will eventually close in time, without need forspecific treatment. It is the author’s practice to manage all

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Figure 7.9. This is an oral ulcer in the interdental space of the rightmandible of a horse which suffered an injury following restraint with achiffney. A large sequestrum can be seen which was removed. Thehorse made a complete recovery.

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parotid duct fistulae conservatively in the certain knowledgethat in the vast majority of cases the fistula will healuneventfully.

In those unusual cases in which the fistula does not close,surgical repair may be effective. The duct should be dissectedfrom the edge of the fistula and closed with simple inter-rupted sutures of 2 metric polyglactin 910. Insertion ofa catheter into the parotid duct may facilitate suturing,making accurate repair less problematic.

Injury to the parotid duct may occur inadvertently duringfacial or dental surgery. However, an understanding of thelocal anatomy should preclude such an occurrence.Transection of the parotid duct may be performed electivelywhen carrying out a buccotomy technique for removal ofmandibular or maxillary cheek teeth. In such cases, an end-to-end anastomosis can be carried out using simple inter-rupted sutures of 2 metric polyglactin 910. A parotid ductfistula may follow surgical removal of sialoliths which areoccasionally encountered in older horses. Secondary closureof such wounds may be effective or alternatively they may beleft to heal by second intention.

Injuries to the mandibular or sublingual salivary glandsor ducts are very rare. The author has encountered one horsewith a ranula associated with the sublingual salivary duct.This was managed successfully by oral marsupialization.

REFERENCES

1. Anon (1975) Equine Digestive System, ed. R Getty, WB Saunders,Philadelphia.

2. Baker GJ (1985) Oral examination and diagnosis: management oforal diseases. In: Veterinary Dentistry, ed. CE Harvey, WB Saunders,Philadelphia, pp. 217–234.

3. Engelbert TA and Tate LP (1993) Penetrating lingual foreignbodies in three horses. Cornell Vet, 83(1), 31–38.

4. Kiper ML, Wrigley R, Traub-Dargatz J and Bennett D (1992)Metallic foreign bodies in the mouth or pharynx of horses: sevencases (1983–1989). Journal of the American Veterinary MedicalAssociation, 200(1), 91–93.

5. Auer JA (ed.) (1992) Equine Surgery. WB Saunders, Philadelphia,pp. 306–308.

6. Scott EA (1982) Surgery of the oral cavity. Veterinary Clinics ofNorth America Large Animal Practice, 4, 3–31.

7. Howard RD and Stashak TS (1993) Reconstructive surgery ofselected injuries of the head. Veterinary Clinics of North AmericaLarge Animal Practice, 9, 185–198.

8. Robinson NE (ed.) (1997) Current Therapy in Equine Medicine,Vol.4. WB Saunders, Philadelphia, pp. 148–149.

9. Hague BA and Honnas CM (1998) Traumatic dental disease andsoft tissue injuries of the oral cavity. Veterinary Clinics of NorthAmerica Large Animal Practice, 14, 333–347.

10. Modransky P, Welker B and Pickett JP (1989) Management offacial injuries. Veterinary Clinics of North America Large AnimalPractice, 5, 665–682.

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