Common emergencies involving the musculoskeletal system include fractures, luxations, lacerations, puncture wounds, infections, and exertional rhabdomyolysis. Although many of these conditions cannot be treated in the field, accurate identification and provision of appropriate emergency treatment are essential for a successful outcome.
Fractures and Luxations
A thorough physical examination is warranted, but completion can be complicated by the severity of the injury and other factors (eg, anxiety, exhaustion, dehydration, owner/trainer anxiety). The goals of initial coaptation of fractures are to relieve anxiety, prevent further injury, and allow safe transportation for additional evaluation. Emergency coaptation of unstable limbs should be performed before radiographic evaluation or transportation to a surgical facility.
Fractures or luxations should be suspected if a loud crack is heard, there is acute non-weightbearing lameness, or the limb is misaligned or visibly unstable. Physical examination should be completed in the best possible setting to avoid further injury to the horse or bystanders. If the horse is recumbent, examination should be completed before attempting to stand the horse. If the horse is standing, examination should be completed before attempting to move the horse. Sedation and a twitch can be used to aid restraint. For sedation, an α2 agonist such as xylazine, or xylazine and acepromazine, can be used. If sedation is needed immediately after maximal exercise, up to double the standard dosage regimen may be required to achieve effective sedation. Butorphanol or detomidine should be reserved for horses that are not controlled with xylazine. Because α2 agonists often cause the horse to lean forward, which may increase the weight on an injured forelimb and decrease the ability to manipulate the limb, the minimal effective dose should be used. If the horse is recumbent and a serious injury is suspected, general anesthesia can be safely induced following maximal exercise using sedation with a combination of xylazine and acepromazine, followed by induction of anesthesia with ketamine and diazepam or tiletamine-zolazepam. The combination of guaifenesin and thiopenthal results in more hypotension and is less desirable. Circulatory status should be briefly assessed by evaluating heart rate, mucous membrane color, capillary refill time, and pulse quality. A heart rate >80 bpm accompanied by a delayed capillary refill time and poor peripheral pulse quality indicates the need for IV fluid support.
Once the general status of the horse has been assessed, location and assessment of the injury follows. It is useful to divide the limbs into 4 levels, which help define the method of coaptation. Level 1 injuries involve the limbs from the fetlock down and include extensor and flexor tendon injuries located at the level of the metacarpus/metatarsus. Level 2 injuries involve the limbs from the fetlock to the carpus or hock. Level 3 injuries involve the forelimbs from the carpus to the elbow or the hindlimb from the hock to the stifle. Level 4 injuries involve the forelimb above the elbow or the hindlimb above the stifle.
The presence of a fracture can be determined by instability, crepitus, or abnormal motion. Luxations should be suspected when there is abnormal lateral to medial motion at the level of a joint. Radiographs are indicated to confirm the presence of a fracture or luxation. If radiographic equipment is unavailable on site, external coaptation should be applied as if a fracture or luxation exists and the horse transported to a referral facility for further examination. Incomplete (hairline) fractures of the radius, tibia, and other bones can be difficult to demonstrate radiographically, particularly in field conditions. Therefore, in the presence of severe lameness with pain localized to a long bone, external coaptation should be completed before transportation to avoid catastrophic displacement of a fracture. Laboratory determinations of biochemistry profile indices are becoming more commonly available, even in field situations. If available, parameters of hydration and electrolyte balance are useful to dictate fluid volume and type.
Therapeutic aims of the initial management of traumatic injuries are to relieve anxiety, immobilize the fracture or luxation for transportation, prevent further damage, and provide safe transportation. The principles of emergency coaptation of traumatic injuries in horses include appropriate wound care before application of external coaptation, provision of adequate padding to prevent skin abrasions, immobilization of the joint below and above the area of injury, prevention of lateromedial and craniocaudal motion, and never ending a splint in the middle of a long bone segment or at the end of a fracture line.
Wounds should be carefully cleaned and debrided. An antiseptic ointment can be applied and held in place with conforming gauze. Cotton padding is applied to the entire length of the segment to be immobilized and held in place with gauze, followed by nonstretch bandage material. The bandage should be snug, to avoid loosening with packing of the cotton material. Splints are then applied and held in place, ideally with fiberglass casting tape. This is particularly useful in stabilizing a luxation. If casting tape is unavailable, heavy tape can be used. The splints must be well padded to avoid the development of sores.
Immobilization of Level 1 Injuries
Level 1 injuries include phalangeal fractures; fetlock, pastern, or coffin joint luxations; and severance of one or more flexor tendons. Although technically Level 1 injuries, extensor tendon lacerations require a different mode of splint application and are discussed separately. Forelimb and hindlimb immobilization differ slightly, because of the presence of the reciprocal apparatus in the hindlimb.
In forelimb injuries, immobilization is best accomplished by aligning the cannon bone with the phalanges to establish a straight column. The horse will bear weight on its toe. The forelimb is held above the carpus and bandaged, and the splint applied on the cranial aspect of the distal limb, extending from the toe to the carpus. If there is lateromedial instability, a lateral splint can also be applied.
In the hindlimb, the reciprocal apparatus prevents extension of the distal limb if the animal is non-weightbearing. Therefore, the limb is best immobilized by applying the splint on the caudal aspect of the limb, from the toe to the point of the hock. If there is lateromedial instability, a lateral splint should also be placed.
A commercially available splint may be used for Level 1 injuries other than fetlock or pastern luxations; however, it does not provide enough lateral-to-medial stability for luxations. The splint is readily available, easy to apply, and effective in achieving immobilization. Two configurations are available—one with a slightly forward-angled bar (for the forelimb) and one with a backward angle with a curve at the level of the fetlock (for the hindlimb). The forward angle configuration is more effective for either fore- or hindlimb injuries. The hindlimb splint has a heel piece to facilitate weightbearing. Alternatively, a heel piece can be welded onto the splint to increase the weightbearing surface area. Nonslip tape should be placed on the foot plate to make it less slippery, particularly on cement floors.
When both extensor tendons of the forelimb or hindlimb are completely severed, the horse will knuckle over, which can injure the dorsal aspect of the fetlock and further disrupt the wound. In this instance, external coaptation is needed to prevent knuckling over at the fetlock. A splint is applied to the cranial aspect of the fore- or hindlimb, with the hoof flat on the ground.
Immobilization of Level 2 Injuries
Examples of level 2 injuries include cannon bone fractures, wounds of the carpus or hock, olecranon fractures, and radial nerve paralysis. In level 2 injuries of the forelimb, 2 splints are needed, applied at a 90° angle, with one lateral and one caudal. The splints should extend from the hoof to the elbow. For olecranon fractures and radial nerve paralysis, the goal of immobilization is to prevent tendon contracture and injury to the dorsal aspect of the limb. Only a caudal splint is needed for these injuries. In hindlimb injuries, as in the forelimb, 2 splints are needed (applied laterally and caudally, from the hoof to the stifle). The angle of the hock makes it difficult to apply a caudal splint. Therefore, the caudal splint can end at the point of the hock, rather than at the stifle. Alternatively, a splint can be molded and applied to the hock.
Immobilization of Level 3 Injuries
Level 3 injuries include fractures of the radius or tibia. With fracture, the flexor muscles become abductors, resulting in displacement and comminution of the medial aspect of the limb. The medial aspect of both the radius and ulna does not include a muscle mass to help prevent penetration of the skin by fractured bone. The goal of external coaptation is to prevent abduction of the limb. On the forelimb, the splint is applied to the lateral aspect of the limb and must extend from the hoof to the withers. The tip of the splint can be taped around the chest for further stability. On the hindlimb, the splint is applied to the lateral aspect of the limb, extending from the hoof to the hip.
Immobilization of Level 4 Injuries
Level 4 injuries include fractures of the scapula, humerus, femur, and pelvis. External coaptation is not recommended for these injuries, as these areas are not amenable to bandaging. Hematomas and swelling around the injury may provide functional immobilization. A bandage should not be applied to the distal limb, as it will make it more awkward to move and may increase motion at the fracture site. If the pelvis is fractured, the need for transportation should be discussed, as moving of the fracture segments may lacerate major blood vessels. General anesthesia for pelvic fracture should be delayed for 3–4 wk to avoid fatal hemorrhage.
Guidelines for Safe Transportation
Before loading an injured horse, proper functioning of the vehicle should be assured, the horse stabilized, and the injury immobilized as much as possible. A low ramp facilitates loading and unloading of an injured horse. While in the trailer, the horse may lean on the wall and partitions to help reduce the load on the injured leg. It will be easier for the horse to travel with partitions in place rather than loose in a makeshift stall. A sling can be placed under the abdomen to help the horse take weight off the injured limb. Many trailers have standing stalls at 45° angles (slant load trailers), which help horses balance during transport. If a regular straight-load trailer is used, the horse should face backward for a forelimb injury, and forward for a hindlimb injury, to help cushion sudden stops. Providing hay helps relieve anxiety, and frequent stops should be made to check on the status of the horse and provide drinking water. If significant cardiovascular compromise exists, IV fluids can be administered while in transit.
If the horse is severely injured and needs to remain recumbent, it can be pulled onto the trailer using a large tarp or blanket. The horse should be kept sedated during transport, to avoid injuries. A head protector or bandage can be used to protect the eyes and head from self-induced trauma. Bandages should be applied to the lower limbs to avoid trauma caused by paddling.
Wounds and Lacerations
Wounds and lacerations are common in horses. The steps involved in the management of these injuries include identification of all involved structures, control of hemorrhage, and evaluation of the need for referral. Referral to a surgical facility is recommended if there are tendon injuries, penetration of a synovial structure, extensive degloving injury, or severe blood loss. In addition to wound management, tetanus prophylaxis, analgesia, and appropriate antibiotic therapy are indicated. If severe blood loss has occurred, cardiovascular support should be provided before or during transportation, or both.
A brief physical examination should be completed before addressing the primary problem. If the wound is located on a limb, the presence and degree of lameness should be noted as indicators of a potentially more serious injury. The following characteristics are then evaluated: location, hemorrhage, configuration, penetration of a body cavity, and involvement of synovial structures or tendons. Wounds over joints, tendon sheaths, or tendons (particularly flexor tendons) and those that expose or penetrate to bone should be explored thoroughly for injury to important underlying structures. Severe hemorrhage may need to be controlled before further wound assessment is possible. A pressure bandage is applied directly over the bleeding area. Attempts to find the bleeding vessels are usually not successful. Certain wound configurations may significantly damage the blood supply to the skin and subcutaneous tissues and result in sloughing (eg, an inverted “V” configuration or significant bruising or trauma to adjacent tissue). Wounds over the chest or abdomen may penetrate important organs. In the case of thoracic wounds, development of an open or closed pneumothorax can lead to severe respiratory distress. Any horse with chest trauma and respiratory distress should be evaluated for the presence of pneumothorax.
The potential involvement of a synovial structure should be immediately determined. The horse should be restrained and sedated as needed for this procedure. A site of entry of the joint or tendon sheath remote from the wound is chosen, clipped, and prepared aseptically. Using sterile technique, saline or a balanced electrolyte solution is injected into the synovial structure. The amount needed to achieve distention can vary from a few mL in the case of a distal tarsal joint injury to ≥100 mL for the femoropatellar joint. All possible joint compartments should be assessed. The wound is observed for leakage of the injected solution.
Extensor tendon injury of the distal limbs results in inability to appropriately place the hoof on the ground, resulting in the horse knuckling over. This suggests involvement of both tendons in proximal metacarpal or metatarsal injuries. Flexor tendon injuries result in hyperextension of the fetlock (superficial digital flexor), lifting up of the toe (deep digital flexor), or complete dropping of the fetlock to the ground (severance of the suspensory ligament). For this to be observed, the horse must bear weight on the limb at least transiently. In the case of complete suspensory breakdown, severe stretching of digital vessels can lead to thrombosis and avascular injury to the hoof. In complete breakdown injury, it is critical to support the fetlock and not allow weightbearing until further stabilization is performed. The goals of initial wound care are to decontaminate the wound as much as possible and prevent further contamination during transportation. This is done by lavage with saline and sharp debridement of gross contaminants. Local antiseptics or antibiotics can then be packed in the wound for further decontamination. Immobilization of the limb (see Equine Emergency Medicine: Immobilization of Level 1 Injuries) is needed if there is injury to a supporting structure (bone, tendon) or significant instability (luxation).
An open chest wound can result in the development of pneumothorax and lead to respiratory distress manifested by a restrictive pattern of breathing. On auscultation, there is no sound in the dorsal lung fields. Because of the incomplete mediastinum in horses, a unilateral chest wound can lead to bilateral pneumothorax. An open pneumothorax is managed by providing a temporary seal over the chest wound. The wound is bandaged and an airtight layer of material (eg, conforming plastic sheets) is applied. The chest is then evacuated by inserting a 14-gauge catheter, using aseptic technique, in the dorsal aspect of the 12th intercostal space and aspirating the air out of the chest. Use of a 3-way stopcock facilitates this procedure.
Penetrating Abdominal Wounds
Penetrating abdominal wounds are serious and potentially fatal injuries that can lead to penetration of a viscus or development of peritonitis. If a penetrating wound is suspected, it should be cleaned, explored for the presence of a foreign body, and debrided. Abdominocentesis can be performed to detect fecal contamination, indicating a ruptured viscus. However, abdominocentesis may not be diagnostic in the early stages of peritoneal contamination, as indicators of peritonitis take several hours to develop. The wound can be bandaged, and broad-spectrum systemic antibiotics initiated. In the presence of a large wound, or if abdominal musculature is involved, the abdomen can be supported.
Head injuries can result in severe CNS damage. Injury can be primary (ie, contusion, lacerations, or hemorrhage causing acute damage) or secondary (ie, subsequent edema, reperfusion injury, and necrosis). Head injury therapy is designed to minimize secondary CNS damage. Causes of head injury in athletic horses include direct trauma from a fall, blows to the head, and falling over backward onto the poll region. The associated injuries include basisphenoid fractures and avulsion of ventral straight muscles of the head. Basisphenoid fractures can result in acute optic nerve damage and cerebral signs. Temporary or permanent blindness may result. The diagnosis is made by radiography; treatment is supportive care and is focused on minimizing secondary brain damage. Rectus and longus capitis muscle rupture occurs most commonly from falling over backward. The muscles attach to the base of the cranium; with injury, hematoma and even avulsion fractures of the muscular insertion may result. Because of the location of these muscles within the guttural pouch septum, hematomas may rupture into one of the guttural pouches, resulting in epistaxis that may require blood transfusion. When epistaxis of guttural pouch origin, in conjunction with a large hematoma in the guttural pouch septum, is identified, diagnosis is made by endoscopy. Radiographs are useful to demonstrate an avulsion fracture accompanied by a soft-tissue opacity overlying the guttural pouches.
Horses with head injuries can be severely ataxic and should be handled and moved with extreme caution. If the horse is down, short-term general anesthesia is best used while moving the horse to a referral facility for further evaluation. If hypoventilation develops, the horse should be intubated and ventilation assisted to prevent hypercapnia. NSAID are used to minimize inflammation. Although controversial, corticosteroids may be indicated if used in the immediate phase of injury. DMSO is often used to minimize secondary edema. Magnesium has recently been proposed as another therapeutic agent for acute head injury.
Ocular injuries are usually traumatic in origin, and include periocular lacerations, corneal lacerations or foreign body penetrating injuries, and direct blows to the eye causing retinal detachment. (Also see Ophthalmic Emergencies.) Evaluation of acute ocular injury includes evaluation of the different structures of the eye, as well as cranial nerve function. Eyelids, conjunctiva, cornea, lens, and fundic examinations can be performed to assess the degree of damage. Vision can be assessed by the menace response, supplemented with obstacle course testing. Oculomotor, trochlear, and abducent nerve function are assessed by the position of the eye and pupillary light responses. Facial nerve and sympathetic innervation to the eye are assessed by eyelid tone and position of the eyelashes.
Treatment of acute ocular injuries includes minimizing pain and inflammation, preventing infection, and preventing further injuries. If penetration by a foreign body is suspected, rapid surgical intervention is indicated to prevent further injury. Anti-inflammatory drugs that are used to minimize pain and inflammation associated with ocular injuries include NSAID, DMSO, and topical osmotic agents. Pain from pupillary spasm can be minimized by dilating the pupil with atropine. Direct sunlight should be minimized by protecting the eye. Acute injuries can be associated with ulceration and secondary bacterial invasion. Use of a broad-spectrum topical antibiotic may prevent secondary infection of an ulcer. Horses that are acutely blind cannot move around their environment well. Further injury should be prevented by protecting the blind eye and by carefully handling the horse.
Last full review/revision March 2012 by Pamela Anne Wilkins, DVM, MS, PhD, DACVIM-LA, DACVECC