11: Management of Wounds of the Head

CHAPTER 11
Management of Wounds of the Head


Spencer Barber, DVM, Diplomate ACVS and Ted S. Stashak, DVM, MS, Diplomate ACVS


Summary


Injuries to the head are common and can result in a significant loss of function if a vital structure is involved. The head is highly prominent, so cosmetic repair of a wound to the head is often important esthetically and may help retain the horse’s resale value. Injuries to the head generally heal well, but the repair of such injuries requires skilled treatment to obtain optimal results. Meticulous attention to repair is necessary when repairing a laceration of a lip, eyelid, or nostril because proper function of these highly mobile structures is important. Although injuries to ears are not common, restoring the cosmetic appearance and function of an injured ear is challenging. Facial and orbital fractures are usually depressed, creating a conspicuous deformity, but they generally can be reconstructed successfully. Nasocutaneous and sinocutaneous fistulas have significant functional and cosmetic implications and can be very challenging to repair, especially if large.


Introduction


The head is commonly wounded, and most often when the horse attempts to flee from a frightening situation while being restrained with a halter and lead rope. This chapter describes commonly encountered injuries to the head, and factors important to their successful management.


Lacerations


Lacerations, the most frequently encountered head injury, often are treated by primary or delayed closure, for the following reasons:



  1. Wounds of the face that are left to heal by second intention (i.e., by contraction and epithelialization) develop a larger epithelial scar than do wounds in other anatomic regions because the mobility of facial skin for healing by contraction is poor.
  2. Epithelial scars, which can be large, lack hair, sebaceous and sweat glands, and pigmentation.1,2 Because the head is highly visible, a wound that heals largely by epithelialization is esthetically unacceptable and decreases the horse’s value.
  3. Several body systems (e.g., respiratory, digestive, auditory, and ocular) can be injured so severely that the performance and even the life of the horse are in jeopardy.3–6 Consequently, surgical repair is preferred so that proper function of the traumatized body system can be maintained.

A wound of the head is usually minimally contaminated, at least when compared to a similar wound on the distal portion of the limb, because horses with a head wound often are presented promptly, and because wounds in this location are a remote distance from debris and feces found on the ground. A good understanding of principles of plastic and reconstructive surgery is beneficial when treating a horse for a severe or chronic injury to the head.7,8 Clinical experience suggests a wound to the head can be closed more successfully than can a similar wound on the limb or the body, possibly because the blood supply to the head is more abundant.3–6


Lip


A laceration to the lip is usually caused by a sharp, protruding object (e.g., a nail) (Figure 11.1). Partial‐thickness wounds to the lip can be treated by primary or delayed primary closure, or the wound can be left unsutured to heal by second intention, although the outcome may not be cosmetically appealing.3–5 Restoring good cosmesis and function to a lip with a full‐thickness wound is challenging,3–5,9 but leaving a full‐thickness wound unsutured to heal by second intention can result in drooling of feed and/or saliva. Dehiscence is common if the technique of repair is poor, because the intimate attachment of the muscles of the lip to the dermis and the oral submucosa subjects the lips to forceful movement (Figure 11.2). Sharply undermining the skin and mucous membrane from the muscle, along with the use of tension sutures to bolster repair, can largely prevent dehiscence.3–5 Because lips have a copious blood supply, lip lacerations rarely become infected following injury, unless blunt trauma has compromised blood supply to the wound.

Photo displaying acute, laceration of the rostral aspect of the upper lip of a horse.

Figure 11.1 Acute, sharp laceration of the rostral aspect of the upper lip.

Photo displaying a sutured lip laceration of a horse dehisced 6 days after reconstruction.

Figure 11.2 Sutured lip laceration that dehisced 6 days after reconstruction.


Treatment


Preoperative preparation usually includes verification that the horse has been vaccinated against tetanus, initiation of antimicrobial therapy, administration of a non‐steroidal anti‐inflammatory drug (NSAID), lavage of the oral cavity with a dilute antiseptic solution (e.g., 0.1–0.2% povidone–iodine), and routine surgical preparation of the lip.


The skin and oral mucosa are undermined 1–1.5 cm from the margin of the wound, using a #10 scalpel blade to separate them from underlying musculature (Figure 11.3a,b). Non‐absorbable, monofilament, size 0 or 1 suture material is preplaced in a vertical mattress pattern, with stents, through the isolated musculature centrally so the knots and supports, when later tied, remain on the outside of the lip (Figure 11.3c,d).

Photos displaying sharp dissection of muscle from skin and oral mucosa of a horse (a), dissection completed (b), external (c) and oral view of placement of vertical mattress tension sutures (d).
Photos of oral mucosa apposing with sutures in interrupted pattern and mucocutaneous junction sutured using vertical mattress pattern (e) and vertical mattress quill sutures tied over soft rubber tubing (f).

Figure 11.3 Same horse as in Figure 11.1. (a) Sharp dissection of the muscle from the skin and oral mucosa. (b) Dissection is complete except for the muscle at the mucocutaneous junction. (c) External view of the placement of vertical mattress tension (quill) sutures. Both suture passages should include the muscle. (d) Oral view of the placement of the vertical mattress tension (quill) sutures. (e) The oral mucosa is apposed with sutures in a simple interrupted pattern, and the mucocutaneous junction is sutured using a vertical mattress pattern. (f) Vertical mattress sutures appose the skin and vertical mattress quill sutures are tied over soft rubber tubing.


The mucosa is apposed with a simple interrupted or continuous suture pattern using size 2‐0 or 3‐0 synthetic absorbable suture material (Figure 11.3e), except at the mucocutaneous junction where one or more vertical mattress sutures are placed to minimize the likelihood of dehiscence. The preplaced sutures are then tied, over soft rubber tubing, and the skin apposed with an interrupted vertical mattress pattern of 2‐0 monofilament, non‐absorbable suture. Using a vertical mattress pattern to close the skin, rather than a simple interrupted pattern, prevents inversion of the skin edges.


A similar approach is used to revise a laceration that has healed by second intention, except that dissection of the skin and mucosa begins at the scarred mucocutaneous junction (Figure 11.4a,b) and is continued until the skin and mucosa have been undermined approximately 1.5–2 cm from the margin of the wound. The preplaced vertical mattress sutures should exit the skin at least 2 cm from the skin edges (Figure 11.4c). The rest of the closure is the same as for an acute laceration (Figure 11.4d).

Photos of chronic lower lip laceration sutured on 2 occasions and dehisced (a), incision at the mucocutaneous junction (b), placement of vertical mattress sutures (c), and repair completed (d).

Figure 11.4 (a) Chronic lower lip laceration that was sutured on two separate occasions and dehisced after repair. (b) Incision at the mucocutaneous junction. The skin and oral mucosa must be dissected from the scarred muscle. (c) Placement of the vertical mattress (quill) tension sutures at least 2 cm from the repair site. The oral mucosa and scarred muscle have been apposed with sutures. (d) Repair complete.


Tension on a sutured laceration at the commissure of the lips increases tremendously when the mouth is opened (Figure 11.5a,b). To counter this tension, at least two additional vertical mattress sutures, with stents, of size 1 or 2 monofilament non‐absorbable suture material should be placed rostral to the repair, through the uninjured lips (Figure 11.5c,d).

Photo displaying the head of a horse in right side view, with chronic laceration involving the right commissure of the lip and cheek.
Photo of the dissection of skin from the muscles of the cheek of a horse.
2 Illustrations of horse’s cheek, displaying dotted lines depicting the undermined areas (left) and sutured wound with two vertical mattress (right).
Photo displaying closure completed in a horse with lacerated right commisure of the lip and cheek.

Figure 11.5 (a) Chronic laceration involving the right commissure of the lip and cheek. (b) Dissection of skin from the muscles of the cheek. (c) Left bottom: dotted line and dotted area illustrate the extent of undermining of the lip and cheek; left top: two cross‐sections illustrating the undermining procedures; right bottom: the laceration is sutured, and two vertical mattress quill tension sutures are placed rostral to the repaired commissure to further stabilize the region; right top: cross‐section illustrating suture apposition of the various layers. (d) Closure complete.


The horse should receive antimicrobial therapy and a NSAID postoperatively for 3–4 days, and can be fed its normal ration. The patient can be cross‐tied, and even sedated or tranquilized, if it attempts to rub the repaired lip. The additional tension sutures with stents, placed rostral to the repair, can be removed in 7–10 days, and skin sutures are removed in 14 days. Dehiscence, if it occurs, usually starts at the mucocutaneous junction. When a lip laceration is sutured using proper surgical technique, healing is by primary intention, and cosmesis and function are good.


Parotid salivary gland and duct


The parotid salivary gland and its duct, being located superficially, are more prone to injury than the better protected sublingual and mandibular glands and ducts. Laceration, direct blunt trauma, and iatrogenic surgical injury are the most common causes of injury to a salivary duct or gland.10–12 The parotid duct is vulnerable to injury at the caudal border of the mandible (Figure 11.6) and is especially vulnerable at the ventral border of the mandible (i.e., at the vascular notch) where the duct and facial vessels course from medial to lateral. The duct then follows the rostral border of the masseter muscle for about 5 cm, turns rostrad beneath the facial artery and vein, and perforates the cheek obliquely to empty at a papilla located in the buccal vestibule opposite the third or fourth maxillary premolar,11,12 but its location is variable. Laceration of the gland or duct should be suspected if a large volume of serous fluid discharges from the wound, especially when the horse is fed (Figure 11.7). The salivary glands of a 500‐kg horse produce ~38 L of saliva in 24 hours, and because the parotid gland is the major producer, discharge of saliva is readily apparent when its duct is lacerated.13

Photo of extensive wound at the caudal border of the mandible of a horse involving the parotid salivary duct.

Figure 11.6 The parotid salivary duct is vulnerable to injury where it travels over the tendon of the sternomandibularis muscle and proceeds ventrally and rostrally at the caudal border of the mandible. An extensive wound at the caudal border of the mandible, such as the one suffered by this horse, is very likely to involve the parotid salivary duct.


Courtesy of Dr. Reid Hanson.

Photo of a horse suffered a laceration to the parotid salivary duct at the ventral aspect of the mandible, with the duct and facial vessels course from medial to lateral.

Figure 11.7 This horse suffered a laceration to the parotid salivary duct at the ventral aspect of the mandible where the duct and facial vessels course from medial to lateral (i.e., at the vascular notch). Saliva is flowing from a fistula into the duct. Leakage of saliva from a lacerated duct was especially copious when the horse ate.


Courtesy of Dr. Reid Hanson.


The site of disruption of a parotid duct within a large wound (Figure 11.6) can be determined by passing a catheter retrograde, with the horse anesthetized, from the oral papilla and watching it exit the wound. Locating the papilla for catheterization occasionally requires a buccotomy slightly rostral to the maxillary premolar adjacent to where it lies.11 To place the catheter, a small cutaneous incision can be created a few centimeters rostral to the buccotomy, through which the catheter is tunneled subcutaneously to the buccotomy. The catheter is inserted in the exposed papilla and advanced into the duct. Contrast radiography can also be used to establish patency of the parotid duct and its radicles that enter the gland (Figure 11.8).

Contrast radiograph of parotid salivary duct and its radicles.

Figure 11.8 Contrast radiograph of parotid salivary duct and its radicles.


Courtesy of Dr. Reid Hanson.


Treatment


Surgical management of an injured salivary gland or duct is aimed at repairing the injured structure or eliminating the secretion of saliva. Many acute salivary fistulas heal by second intention within 1–3 weeks, and thus, deferring treatment can be a worthwhile option.12 A fresh wound involving glandular tissue can be repaired by primary closure following standard preparation, irrigation, and debridement of the wound. The wound is reconstructed using a multilayer closure starting with the capsule of the gland. Care is taken not to penetrate the glandular tissue with suture because the suture could act as a nidus for formation of a calculus.14 The wound should be allowed to heal by second intention if it is heavily contaminated or chronic, or if the owner imposes a financial constraint. If discharge from a wound over the parotid gland persists, laceration of one of the several large radicles that form the parotid duct should be suspected.12


A lacerated duct may be treated by primary closure, delayed primary closure, or second‐intention healing. Horses with a lacerated duct are often presented for treatment after the epithelium of the duct has healed to cutaneous epithelium, causing a salivary fistula. Primary closure of a freshly lacerated duct or a non‐healing salivary fistula can be facilitated by suturing the defect over an intraluminal catheter placed in the duct (authors’ recommendation). Cannulating the duct’s papilla can sometimes be difficult or impractical. In this situation, a size 2 nylon suture can be threaded normograde, through the laceration or fistula, into the distal portion of the duct and exited through the papilla into the mouth. A catheter is then passed through a 14‐gauge needle, used as a cannula, inserted through the cheek to enter the oral cavity just rostral to the papilla. The catheter is then guided over the nylon suture into the duct. When the tip of the catheter emerges from the laceration or fistula, it is directed retrograde into the proximal aspect of the duct to the level of the ventral aspect of the parotid gland. The lacerated duct is reconstructed using 5‐0 or 6‐0 absorbable suture material placed in a simple interrupted pattern.10,11


Alternatively, the duct can be reconstructed by placing three interrupted sutures of 5‐0 or 6‐0 monofilament absorbable suture material that appose the cut ends of the duct. The three sutures are placed an equal distance apart to form a triangle, and 5‐0 or 6‐0 sutures are placed between the apices of the triangle.11,14 The external end of the catheter is sutured to the side of the face to provide visible evidence of continued flow of saliva and to allow for easy removal of the catheter when the duct has healed. The catheter is left in place for 4–5 weeks. 10,11 Leaving the catheter in place this long helps prevent stricture of the duct, ensures continued flow of saliva, and the catheter acts as a support for healing. If the cut ends of the duct cannot be anastomosed because too much tissue has been lost, an interposing polytetrafluoroethylene tube graft (Gore.com/medical) may be sutured to each cut end to bridge the gap.15 The latter technique is recommended for salivary duct defects greater than 2.5 cm in length. Alternatively, a soft, smooth polyvinylchloride catheter (liberatormedical.com/catheters/8‐Fr.), acting as a temporary intraluminal stent to bridge the tissue gap for shorter defects (less than 2.5 cm in length), can be used to allow healing of the defect over the stent, restoring ductal continuity.10 Other options for maintaining salivary secretion are to create a fistula from the duct proximal to the injury into the oral cavity or to translocate the parotid duct to another site. Because of inconsistent results, these procedures are not recommended by the authors.12


The horse should receive antimicrobial therapy and a NSAID postoperatively for 4–5 days and can be fed its normal ration. The horse can be made to reduce production of saliva to enhance healing, especially if the ends of the duct cannot be completely apposed with sutures. To do this, the horse should be isolated, in a box stall, from other horses being fed, and fed small amounts of soaked hay pellets several times daily. The head is often bandaged to prevent the horse from dislodging an externally sutured catheter (see Chapter 7 for more information about bandaging techniques). The bandage is maintained until the catheter is removed.


The alternative method of resolving a fistula of the parotid duct is to eliminate the source of saliva. Horses readily tolerate the loss of one parotid gland.12 The source of saliva can be eliminated by ligating the parotid duct or by chemically ablating the gland. Excising the gland is difficult to impossible because of the intimately associated large vessels and nerves located adjacent to and embedded within the glandular tissue.12 Chemical ablation and ductal ligation are easier procedures to perform and more economical than reconstructing the duct.


To bring about physiologic destruction of the parotid gland, the duct is ligated between the gland and the fistula. A catheter is advanced into the proximal portion of the duct through the fistula, and an incision is made over the catheter, which can be palpated beneath the skin. Several sutures are placed around the catheterized duct and tied after the catheter is withdrawn. The duct should be ligated with heavy suture material (i.e., 0 or 1) because, if fine suture material is used for ligation, the suture may cut through the duct causing its lumen to be re‐established. If the wound is fresh, hampering locating the severed end of the duct, the duct can be located and ligated where it crosses the tendon of insertion of the sternomandibularis muscle. To locate and ligate the duct where it crosses the tendon, an incision is made caudal to the vertical ramus of the mandible over the longitudinal axis of the tendon. The duct can be located by palpation through this incision. Because one or two radicles often exit the gland distal to the duct at this location, the duct should also be ligated further distally. To locate the duct further distally, the lumen of the duct is catheterized through a small incision in the duct, a second incision is made over the catheter 3–4 cm distal to the first incision, and several sutures are placed around the portion of the catheterized duct exposed in the second incision and tied after the catheter is withdrawn. The cutaneous incisions are sutured.


The parotid gland may be chemically ablated by infusing the gland, via a catheter placed into the duct, using 10% formalin, 2% chlorhexidine, or 2 or 3% silver nitrate.12,14,16 Of these chemicals, 10% formalin produces the least amount of inflammation and necrosis and is, therefore, the solution of choice.16 Water‐soluble, iodinated contrast solution is also capable of eliminating glandular tissue.12,16 This should be taken into consideration when performing retrograde contrast radiography. To avoid destroying the gland when examining the duct and gland using contrast radiography, the contrast material should be allowed to drain from the gland and duct, and the duct and gland should then be irrigated with sterile isotonic saline solution. When using 10% formalin to destroy the gland, 35–40 mL are infused into the gland by inserting a catheter into the proximal extent of the duct at the fistula. The solution is maintained within the gland for about 90 seconds before it is allowed to drain. Secretion of saliva is eliminated usually within 3 weeks.16


Facial nerve


Lacerations that transect the facial nerve cause permanent sagging of the lower lip and a wry upper lip (Figure 11.9a,b), collapse of the ipsilateral nostril during exercise and result in unsightly drooling and slobbering of feed and water due to the loss of a buccal seal.

Photos displaying lateral view of horse with transection of facial nerve with lips drooped and tongue protudes (a), frontal view of the same horse (b), and wedge resection of lower lip completed (c).
Photos displaying sutured lip in a horse (d), lateral view of a horse 1 year later with good apposition of the lips (e) and frontal view of a horse 1 year later (f).

Figure 11.9 (a) Lateral view of a horse with transection of the facial nerve. The lips on the right side droop, and the tongue protrudes slightly. (b) Frontal view of the same horse. Note the wry appearance to the right lips and nostril. (c) Wedge resection of the lower lip completed. (d) Sutured lip. (e) Lateral view 1 year later. Note the good apposition of the lips. (f) Frontal view 1 year later.


Treatment


Although motor function to the lips cannot be restored, a wedge resection of the lower lip aligns the lips sufficiently to restore a buccal seal, which prevents slobbering and drooling and often improves the cosmetic appearance of the lip.3–5 The amount of lower lip to excise is estimated by comparing the lower lip to the upper lip when the two are pressed together so that they become aligned in a normal position. Because both the upper and lower lips droop when the horse is anesthetized, the preferred technique is to push them both back from their sagged position by applying pressure on the muzzle, thus causing the lower lip to bulge laterally, allowing an estimate of the amount of tissue to be removed.


A full‐thickness, triangular wedge of lip, the apex of which is directed ventrad, is excised to the reflection of the mucosa on to the gum, (Figure 11.9c). The mucosa and skin are sharply separated from the underlying atrophied muscle for 1–1.5 cm from the right and left aspects of the margins of the wound. Sutures are preplaced in the musculature using a vertical mattress pattern, with stents, as described earlier. The mucosa is sutured from within the oral cavity, using 2‐0 synthetic absorbable suture material placed in a simple interrupted or simple continuous pattern, so that the knots are located orally. The skin is apposed with 2‐0, non‐absorbable monofilament suture material placed in a vertical mattress pattern, and the preplaced tension sutures are tied (Figure 11.9d).


Antimicrobial therapy and a NSAID are administered before surgery, and administration is continued for a few days postoperatively. The horse should be observed closely for signs of rubbing at the surgical site; if observed, administering a tranquilizer and continuing the administration of the NSAID usually prevent rubbing. If they do not, the horse should be cross‐tied for a week to prevent rubbing of the surgical site. Dehiscence, if it occurs, usually begins at the mucocutaneous junction. Tension sutures can usually be removed at 7–10 days, and skin and mucosal sutures at 14 days. A cosmetic and functional outcome is usually achieved (Figures 11.9e,f).


Tongue


The tongue can be lacerated by the teeth during recovery from anesthesia, by the bit when a horse pulls back when tied fast by the reins, or when a sharp object enters the mouth.3–5 The laceration commonly extends transversely across the dorsal surface of the tongue into the musculature. Healing by second intention produces a defect on the dorsum of the tongue, the extent of which depends on the depth and width of the laceration.


This defect can cause three problems: (1) the bit may periodically lodge in the defect, causing problems with control of the horse’s head and, hence, performance; (2) the tongue may be re‐injured at the defect causing bleeding; and (3) if the defect is deep, the tongue may not remain between the dental arcades (i.e., a flail tongue) causing it to be injured by the teeth. The depth and location of the wound and the intended use of the horse are considered to determine if the wound should be sutured. Lacerations involving less than 30% of the tongue’s thickness can be left to heal by second intention, but deeper lacerations should be sutured (Figure 11.10).4

Photo displaying deep laceration of the tongue resulting in a flail tongue.

Figure 11.10 Deep laceration of the tongue, which would likely result in a flail tongue if not sutured.


Because the tongue’s vascular and nervous supply is located in the ventral half of the tongue, even deep lacerations can be sutured successfully because the blood vessels and nerves are rarely damaged by the injury. Assessment of the vascular supply is usually based on color, temperature, and bleeding from the edges of the wound during debridement, or less commonly by fluorescence after fluorescein dye (1.2 mg/kg) is administered intravenously. If avascular, that portion of the tongue rostral to the laceration must be amputated.


Treatment


Preoperative preparation includes administration of an antimicrobial drug and a NSAID. The oral cavity is lavaged to remove feed, and the tongue and wound are gently scrubbed with a mild antiseptic solution using a gauze swab.


Small lacerations at the tip of the tongue can sometimes be repaired with the horse standing, but the horse should be anesthetized if the injury is extensive or located more caudally than at the tip. The tongue of the anesthetized horse is exteriorized by exerting traction on a towel clamp placed through the tongue, or on a gauze loop, placed around the tongue, caudal to the laceration. The exposed wound can be isolated by draping (Figure 11.11a).

Photos of laceration involving 2/3 of the tongue (a), vertical mattress sutures placed and muscles apposed with simple interrupted suture pattern (b), and suture completed in a horse (c).;Illustrations of lacerated tongue and combination of vertical mattress and simple interrupted suture patterns.

Figure 11.11 (a) Laceration involving two‐thirds of the tongue. (b) Vertical mattress sutures are placed, and the muscles are apposed with a simple interrupted suture pattern. (c) Repair complete. (d) Combination of vertical mattress and simple interrupted suture patterns. (e) Top view of healed tongue laceration.


(a) Courtesy of Dr. G.W. Trotter.


The margin of the wound is excised with a scalpel. Excising anything more than a narrow margin causes the sutured tongue to deviate dorsally or laterally. Accurate closure of dead space and approximation of tissue edges are imperative to prevent dehiscence, because constant movement of the tongue and the presence of saliva, bacteria, and feed hinder healing. The lacerated sides of the tongue must be apposed accurately.


The mucosa of the dorsal surface of the tongue is thick and dense and has great strength and, therefore, holds tension sutures well. The tongue should be sutured using absorbable suture material to eliminate the necessity for removing sutures. A vertical mattress tension pattern using 0 or 1 monofilament, absorbable suture should penetrate the laceration into the musculature centrally so the knots, when later tied, reside on the dorsal aspect of the tongue (Figure 11.11b). This layer provides great strength to the repair. Before tying the vertical mattress sutures, synthetic absorbable monofilament sutures (0 or 2‐0), are used to appose the lacerated muscles and eliminate dead space. The mucosa of the tongue is also apposed with a vertical mattress suture pattern (Figures 11.11c,d) or a combination of vertical mattress and simple interrupted suture patterns.


If the tongue must be amputated, a transverse wedge‐shaped piece of tissue is removed from the remaining stump, creating dorsal and ventral flaps that are closed with a horizontal or vertical mattress suture pattern.3–5 Horses can be expected to eat and handle a bit normally after amputation of the tongue to the level of the frenulum.17


Administration of antimicrobial therapy and a NSAID is continued postoperatively for 3–5 days. Feeding a soft food may ease the comfort of the horse. A good functional result can be expected in most cases (Figure 11.11e), even if a portion of the tongue requires amputation.


Nostril


Lacerations of the nostril, more common in head‐shy horses, are usually caused by a protruding object, such as an angled bolt protruding from a gate or a horse trailer.3–5 The soft tissues collapse during inspiration and flutter during expiration if the laceration is extensive and full‐thickness, because the horse is unable to properly dilate the nostril and because negative inspiratory pressure collapses the nostril. A good blood supply to the region usually facilitates healing, even if the laceration is chronic.


Laceration to the lateral margin (i.e., base) of the nostril can be problematic because of tension/shearing forces resulting from muscle contractions associated with movement of the upper lip when the horse eats and movement of the ipsilateral alar cartilage when the nostril dilates. Repair of a full‐thickness laceration to the arch of the nostril is fairly straightforward and rarely problematic. The horse can be discouraged from rubbing the repaired nostril by administering a NSAID, by cross‐tying it, or by applying a half‐muzzle.


Occasionally, a horse develops a stenotic nostril when the laceration is left to heal by second intention (Figure 11.12a) or when the normal arch to the nostril is not restored with suturing. If only the most rostral aspect (external orifice) of the nostril is stenotic, two Z plasties can be used to increase the diameter of the opening (Figure 11.12b).18 If, however, the stenosis extends caudally to involve the false nostril, the stenotic nostril must be incised along the healed scar and re‐apposed so that the normal arch of the nostril is restored.4

Photo of reduced opening of the left nostril of a horse after suture repair 3 months earlier (left) and illustrations of constricted nostril of a horse due to scarring and Z plasties complete and sutured (right)

Figure 11.12 (a) Reduced opening of the left nostril after suture repair 3 months earlier. This racehorse was presented because of inadequate and noisy airflow through the left nostril. (b) Left: constricted nostril due to scarring (dotted lines illustrate incisions for Z plasties); right: Z plasties complete and sutured. The diameter of the nostril is enlarged.


Treatment


Acute lacerations of the dorsal arch of the nostril (Figure 11.13a) should be sutured with 2‐0 monofilament nylon in an interrupted, modified figure‐of‐eight pattern to appose the skin on the outside of the nostril and skin within the false nostril (Figure 11.13b‐d).3–5 The advantages of this approach to suturing are speed of application, good apposition of all tissue layers, and the ability to remove the sutures by cutting a single loop. Alternatively, simple interrupted sutures can be used, but gaping of the wound between the sutures is common.

Photo of sharp laceration of dorsal arch of the left nostril of a horse (a), and schematic of modified figure-of-eight interrupted suture pattern apposing both epithelial surfaces (b).
Photos displaying passage of the suture through half the thickness of tissue (c), and suturing completed in a horse (d).

Figure 11.13 (a) Sharp laceration of the dorsal arch of the left nostril. (b) Placement of the modified figure‐of‐eight interrupted suture pattern that apposes both epithelial surfaces. (c) Passage of the suture through half the thickness of tissue. The suture then enters the tissue on the opposite side and exits through the skin within the false nostril. (d) Suturing is complete.


Acute lacerations of the base of the nostril are usually best handled by primary closure (Figure 11.14a).3–5 After the site is prepared for surgery, the nostril is packed with sterile gauze, and drapes applied to the area (Figure 11.14b). The wound should be debrided, but care must be taken to not further compromise the blood supply to the flap (Figure 11.14c). Because this area is subjected to high motion from movement of the upper lip and alar cartilage, a three‐layer suture closure is recommended (Figure 11.14d) to provide security and good approximation of tissue. The skin inside the false nostril is sutured from within using a continuous‐horizontal mattress suture pattern of 2‐0 synthetic absorbable suture material (Figure 11.14d). The deep tissue is apposed in a simple interrupted fashion, and the skin is sutured with 2‐0 monofilament non‐absorbable suture using an interrupted vertical mattress pattern (Figure 11.14d,e).

Photos of laceration at the base of nostril (a), nostril packed with sterile gauze (b), debridement completed (c). Drawing of laceration, suture in nostril, and suture patterns (d) and photo of suture completed (d).

Figure 11.14 (a) Laceration at the base of the nostril. (b) The nostril is packed with sterile gauze after clipping hair, scrubbing with surgical soap, and irrigating with an isotonic saline solution. (c) Debridement is complete. Note the limited attachment of the caudal extent of the skin flap. (d) Left: laceration; middle: sutures placed in the nostril; right: suture patterns used for the three‐layer closure. (e) Suturing complete.


A chronic laceration of the base of the nostril presents a special problem because the flap of tissue may be smaller than its original size due to contraction (Figure 11.15a,b).3–5 The flap must be incised to create fresh edges that are then undermined to reform the inner and outer epithelial layers at the base of the nostril. When creating these fresh edges, only a minimal amount of tissue should be excised (Figure 11.15c).

Photos of side (a) and cranial (b) views of chronic laceration at the base of right nostril. Drawings of laceration at the base of nostril and suture completed (c) and lateral view of sutured nostril (d).; Photos displaying cranial view of reconstructed nostril (e) and a half-muzzle covering nares to protect sutured part from trauma (f).

Figure 11.15 (a) Side view of a chronic laceration at the base of the right nostril. (b) Cranial view of this chronic laceration. Note the reduction in diameter of the external naris. (c) Top: dissection planes and layers of closure; bottom left: laceration at the base of the nostril; bottom right: nostril reconstruction is complete. (d) Lateral view of the reconstructed nostril. (e) Cranial view of the reconstructed nostril. Note that the nostril’s diameter is almost equivalent to that of the opposite, normal side. (f) A half‐muzzle covering the nares to protect the repair site from trauma; it was attached to the halter, and because it covered only the nostrils, the horse could still eat and drink.


The first step is to make an incision in the base of the nostril that extends rostrally along the line of injury from the base of the flap to the site where the most rostral tip of the flap should reside, without reducing the luminal diameter of the nostril. The skin on the dorsum and on the ventrum of the base of the wound is undermined to produce two edges of tissue for internal and external closure (Figure 11.15c). Inner and outer edges are created in the tissue flap in a similar manner (Figure 11.15c). The fresh edges produced by these incisions are sutured as described previously for acute lacerations. The freshened edges are apposed by suturing from the base of the flap toward the tip of the flap (Figure 11.15d,e). Alternatively, closure can be started by suturing the tip of the flap to the appropriate site on the base of the nostril. Pulling the flap too rostrad may result in stenosis of the nostril and increases tension on the sutured wound.


Postoperative care is similar to that for repair of other lacerations of the nostril. A muzzle that covers the nostril, while allowing the horse to eat and drink, can be applied to prevent the horse from rubbing the surgical site (Figure 11.15f). Lacerations of the nostril generally heal well, and a good functional and cosmetic result can be obtained if the principles in this section are followed; otherwise, results can be very disappointing.


Eyelid


Lacerations of the upper and lower eyelids are relatively common and usually occur when the eyelid contacts a sharp object.3–5 If the wound is caused by a blunt object, however, the eye should be examined, and the bony orbit evaluated (see Management of fractures of the medial aspect of the orbital rim and zygomatic [supraorbital] process, later in this chapter). Because eyelids have a generous blood supply that is conducive to healing, repair is always attempted (Figure 11.16) to preserve the mucocutaneous junction of the margin of the eyelid, an appropriate palpebral fissure, and a functional blink response.19,20 Even flaps with a very small base often survive.

Photos of acute, full-thickness, oblique laceration of upper eyelid (a), lacerated margin elevated exposing laceration of conjunctiva (b), and #11 Bard Parker blade (c) and scissors used for debridement (d).

Figure 11.16 (a) Acute, full‐thickness, oblique laceration of the upper eyelid. (b) Lacerated margin is elevated to expose the laceration of the conjunctiva. (c) A #11 Bard Parker blade is used to debride the laceration. (d) Scissors are used to complete the debridement.


Courtesy of Dr. G. Severin.


Eyelid lacerations less than 3 hours old can usually be sutured immediately, as can lacerations 3–12 hours old, provided edema is not excessive and the wound is not severely contaminated. Lacerations more than 12 hours old are treated by delayed primary closure the next day, as described under Treatment. The eye should be examined carefully. A tractable horse with a minor injury may be treated while standing, but anesthetizing the horse is best if the laceration is full thickness or involves the margin of the lid.


Treatment


The hair is clipped, but not shaved, because shaving might create enough irritation to cause swelling. The eyelashes are trimmed with scissors. The skin is prepared using a mild antiseptic solution (0.1–0.2% povidone–iodine is recommended), and the eye is rinsed with a sterile eye wash for surgery.19,21 The edges of the wound are debrided minimally, removing only tags of obviously dead tissue. Although ophthalmologic instruments are ideal, the eyelid can be repaired with straight and curved mosquito hemostats, Brown Adson thumb tissue forceps, and a #10, #11, or #15 Bard Parker scalpel blade.


Basic principles for surgery of the eyelid include the following:3–5,19,20 (1) remove as little tissue as possible (Figure 11.16c,d); (2) accurately align and carefully appose the tissues; (3) suture lacerated conjunctiva so that the knots are buried within the tissue and do not rub on the cornea (Figure 11.17a,b).

Illustrations of suture tied at the tarsal plate (g), interrupted sutures apposing skin (h), figure-of-eight suture pattern apposing lid margin and tarsal plate (i), and simple interrupted suture closure (j).

Figure 11.17 Repair of an eyelid laceration. (a) Full‐thickness lower eyelid laceration. (b) Close‐up of (a). Dark lines at the eyelid margin illustrate the tarsal plate. (c) Continuous sutures are used to appose the conjunctiva. Note that the knots are placed so they are buried in tissue, preventing them from rubbing on the cornea. (d,e,f) Suture is placed along the lid margin through the Meibomian glands and tied so the knot does not contact the cornea. (g) The second skin suture is placed through the tarsal plate and tied to take up the tension. (h) Simple interrupted sutures appose the skin. (i) Illustrates a figure‐of‐eight suture pattern to appose the lid margin and the tarsal plate. (j) Simple interrupted suture closure.


Courtesy of Dr. G. Severin.


A support skin suture must sometimes be placed first to align the tissues and reduce tension. To assure correct apposition and restoration of eyelid function, the first skin suture is placed along the sharp edge of the lid through the Meibomian gland and tied so that the knot does not contact the cornea (we recommend 4‐0 to 6‐0 non‐absorbable suture material) (Figure 11.17c,d, Figure 11.18a). The next suture should be placed deeply, 2 mm from the edge of the eyelid, to penetrate the tarsal plate (Figure 11.17g); this suture absorbs most of the tension. Alternatively, tissues at the margin of the eyelid may be apposed using suture inserted in a figure‐of‐eight pattern (Figure 11.17i). The rest of the closure is routine, using either an interrupted or continuous suture pattern (Figure 11.17j, 11.18b).

2 Photos displaying the upper eyelid of the same horse, with laceration (left) and sutured wound (right).

Figure 11.18 Same horse as in Figure 11.16. (a) The apex of the laceration was sutured into its normal position to assure good alignment. (b) The eyelid 14 days postoperatively.


Courtesy of Dr. G. Severin.


To perform delayed primary closure, the laceration and skin are cleaned with dilute povidone–iodine solution (0.1–0.2% is recommended). Silver sulfadiazine cream 1% is applied to the laceration liberally, and the laceration and eye are covered by a bandage that encircles the head.21 Antimicrobial therapy and a NSAID are administered systemically to the horse. This treatment is very effective in reducing edema, and in most cases, the wound can be sutured after 24 hours of treatment, as previously described.


The horse should receive antimicrobial and analgesic therapy, systemically, for 24 hours postoperatively if the wound was fresh when sutured. Antimicrobial therapy should be continued for 5–7 days if the wound was contaminated or infected. A NSAID can be administered for 3–5 days, and administration should be continued longer if the horse displays signs of uveitis. Excessive manipulation of the eyelid should be avoided to reduce the risk of malalignment of the mucocutaneous junction, which could contribute to corneal disease.


Entropion or ectropion may result from a failed or inappropriate repair of a lacerated eyelid. Either condition can result in irritation of the ocular surface and corneal ulceration, and, in an aged horse, chronic irritation can lead to formation of a squamous cell carcinoma or a cataract.22,23 In one report, entropion and ectropion developed in the same horse. Entropion developed after a repaired lower eyelid laceration dehisced, and an attempt to correct the entropion by removing tissue from the lower eyelid resulted in a cicatrix that, in turn, resulted in ectropion. Because the ectropion was too severe to repair by using a lateral eyelid wedge excision or the V–Y plasty, a modified Kuhnt–Szymanowski procedure was used to correct the ectropion and repair the margin of the eyelid.22,24


Applying an antibiotic solution or ointment to the eye is not necessary unless the cornea was injured and/or the wound was infected. If the upper eyelid was sutured, the antibiotic can be instilled beneath the lower eyelid by displacing the lower lid rostrad, or a subpalpebral lavage system can be installed beneath the lower eyelid. If the lower eyelid was sutured, topical medication can be administered by using a subpalpebral lavage system placed beneath the upper eyelid. Bandaging, a fly mask, protective goggles, or cup (“Eye Saver”, http://www.naghorseranch.com), and cross‐tying may be necessary to protect the wound from trauma produced by rubbing.4,5,19,20 Skin sutures are removed 14 days after closure. Eyelid lacerations heal well, and success is good if surgical closure is meticulous.

Sep 15, 2017 | Posted by in GENERAL | Comments Off on 11: Management of Wounds of the Head

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