Use of a minimally invasive fasciotomy technique for treatment of antebrachial compartment syndrome in two horses Brad B. Nelson, DVM, MS; Claude A. Ragle, DVM; Myra F. Barrett, DVM, MS; Dean A. Hendrickson, DVM, MS
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Case Description—An 18-year-old Paint stallion (horse 1) and a 17-year-old Morgan gelding (horse 2) were evaluated because of an acute onset of severe unilateral forelimb lameness. Clinical Findings—Both horses were unable to bear weight on the affected forelimb and had a dropped elbow appearance. Radial nerve paralysis, triceps myopathy, and fractures of the humerus and ulna were ruled out. The caudal aspect of the affected antebrachium of each horse was very firm to palpation and became firmer when weight was shifted onto the limb. Ultrasonographic examination revealed swelling and suspected intramuscular hemorrhage of the caudal antebrachial muscles. On the basis of clinical examination and diagnostic imaging findings, both horses had antebrachial compartment syndrome diagnosed. Lameness did not substantially improve with medical treatment in either horse. Treatment and Outcome—Caudal antebrachial fasciotomy was performed in each horse. Following sedation and local anesthetic administration, a bistoury knife was inserted through small incisions to perform fasciotomy. Horses remained standing throughout the procedure and were immediately able to bear weight on the affected limb without signs of discomfort. Horse 1 developed colitis and horse 2 developed a mild incisional infection, but both fully recovered and returned to their previous activities. Clinical Relevance—Antebrachial compartment syndrome is a rare cause of severe unilateral forelimb lameness and should be considered as a differential diagnosis in horses with a dropped elbow appearance. Both horses of this report had a successful outcome following antebrachial fasciotomy. (J Am Vet Med Assoc 2015;247:286–292)
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n 18-year-old 640-kg (1,408-lb) Paint stallion (horse 1) was evaluated at the Veterinary Teaching Hospital at Washington State University because of an acute onset of severe right forelimb lameness. The horse had been primarily used for breeding and was found in the owner’s pasture with severe lameness 2 hours prior to the examination. The horse’s heart rate was 52 beats/min, respiratory rate was 28 breaths/min, and temperature was 36.7°C (98.1°F). The horse had a right forelimb lameness that was graded 5/5 according to the American Association of Equine Practitioners scale.1 There was a moderate amount of swelling in the right shoulder, and the olecranon tuberosity was displaced distally (dropped elbow sign). The caudal aspect of the antebrachium was very firm to palpation and became even firmer as the horse attempted to bear weight on the limb. Moderate signs of pain were elicited during palpation, with the horse retracting the limb. The horse was able to advance the affected limb cranially From the Departments of Clinical Sciences (Nelson, Hendrickson) and Environmental and Radiological Health Sciences (Barrett), College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523; and the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164 (Ragle). The authors thank Drs. Chris McKay and Greg Roberts for expertise with the ultrasonographic examinations, Drs. L. Nicki Wise and Kathy Seino for case management (horse 1), and Dr. Mustafa Elarbi for illustrations. Address correspondence to Dr. Nelson ([email protected]). 286
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and place its hoof on the ground, suggesting complete radial nerve paralysis was not the cause of the dropped elbow sign. Moreover, the triceps musculature was not firm on palpation and this examination did not elicit signs of pain, suggesting triceps myopathy was not the cause of the dropped elbow sign. The amount of firm and painful soft tissue swelling palpable on the caudal aspect of the antebrachium was consistent with antebrachial compartment syndrome. Radiography of the right humerus (lateromedial view) and radius and ulna (craniocaudal and lateromedial views) was performed and did not reveal evidence of fracture. Ultrasonographic examination of the right antebrachium revealed ill-defined and diffuse areas of increased echogenicity, swelling, and disruption of normal architecture within the superficial and deep digital flexor muscles, compared with the left antebrachium. These findings were most consistent with intramuscular hemorrhage and generalized inflammation. On the basis of clinical examination and diagnostic imaging findings, a presumptive diagnosis of antebrachial compartment syndrome was made. Treatment of the right forelimb included dry cold and active compressiona for 15 minutes every 12 hours, and topical application of 1% diclofenac sodium creamb to the caudal aspect of the antebrachium. The horse also received flunixin meglumine (1.1 mg/kg [0.5 mg/lb], IV, once) and butorphanol tartrate (0.04 mg/kg [0.018 mg/lb], IM, once). Twelve hours later, JAVMA, Vol 247, No. 3, August 1, 2015
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the horse’s lameness had slightly improved (grade 4/5), but signs of pain were still elicited by palpation of the caudal antebrachial region. Caudal antebrachial fasciotomy was performed because of the lack of appreciable improvement with medical treatment. The horse was placed in standing stocks and sedated with xylazine hydrochloride (0.3 mg/kg [0.14 mg/lb], IV) and butorphanol tartrate (0.01 mg/kg [0.005 mg/lb], IV). The right antebrachium was clipped of hair and aseptically prepared for surgery. A line block was performed by administration of 2% mepivacaine hydrochloride solution at the approximate level of the midradius on the caudolateral aspect of the limb, over the ulnaris lateralis muscle. The local anesthetic was injected into the skin and subcutis, deposited over a length of 5 cm in the proximodistal direction at the planned incision site, followed by injection deeper into the caudal antebrachial fascia. Additionally, local anesthetic was deposited into the caudal antebrachial fascia (beneath the subcutis) at 5-cm increments proximal and distal to the planned in- Figure 1—Illustration of the cross-sectional anatomy of the equine antebrachium at the level of the The location of the cross-section is depicted as the transverse line in the image insert. cision, along the intended transection midradius. The extensor carpi radialis and common digital extensor muscles, cephalic vein, and medial cutasite. The site of the planned incision neous antebrachial nerve are the only soft tissue structures not encased within the antebrachial was at a location that avoided the ul- fascia. The radial head of the deep digital flexor muscle is encased within the antebrachial fascia is not shown; this structure becomes apparent distal to the midradius between the caudal nar nerve and antebrachial vascula- but aspect of the radius and cranial aspect of the humeral head (short component) of the deep digital ture (Figure 1). An incision 3 cm in flexor muscle. The ulnar head of the deep digital flexor muscle is present proximal to the level of length was made in the skin over the the cross section, but by midradius extends distally as a tendon. DDF = Deep digital flexor. local block with a No. 10 blade and extended through the subcutaneous tissues and caudal antebrachial fascia (Figure 2). The caudal antebrachial fascia was easily distinguished from the subcutaneous tissues and deeper musculature owing to its firmness on palpation and bright white appearance. A curved, blunt-tipped bistoury knifec (Figure 3) was inserted into the incision, deep to the caudal antebrachial fascia. The instrument was oriented proximodistally (with the tip of the blade most proximal), and the 5-cm blade and most of its thin handle were inserted and pulled caudally to transect the fascia, leaving the skin intact. This provided transection of the fascia approximately 10 cm proximal to the incision. Then, the instrument was oriented distoproximally, and the procedure was repeated to transect the tight caudal antebrachial fascia distal to the incision. At this point, the fascia was still palpably firm proximally, beyond the length of the bistoury knife. Laparoscopic scissorsd were used, with the tip inserted through the same incision, to transect the remaining fascia proximally until it was no longer Figure 2—Photograph of the right forelimb of an 18-year-old Paint stallion with antebrachial compartment syndrome (horse 1). Cranial is to tight on palpation. After transection, the restricted and the right. Notice the 3-cm-long incision made on the caudolateral aspect swollen musculature expanded beyond the antebrachial of the limb allowing insertion of a bistoury knife for transection of the compartment, spreading the edges of the incision apcaudal antebrachial fascia. The yellow lines represent the approximate locations of 2 caudolateral incisions made on the left antebrachium of a proximately 3 cm apart. A mild amount of hemorrhage 17-year-old Morgan gelding that underwent similar treatment for antedischarged from the incision, and the incision was left brachial compartment syndrome (horse 2). A third incision (location not open to facilitate drainage. A light bandage made with shown) was made on the caudomedial aspect of the affected forelimb roll gauze and elasticized bandage material was applied of horse 2 at the same level as the distal caudolateral incision.
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to the antebrachium. Immediately following transection of the caudal antebrachial fascia, the horse could fully weight bear on the right forelimb, and after bandaging it walked back to the stall without lameness. Eight hours later, the horse had signs of pain on palpation of the right forelimb. The right shoulder and triceps musculature were moderately swollen. Ultrasonographic examination of the affected region revealed gas within the muscle fascia planes, and although subcutaneous gas migration following surgery was considered, clostridial myositis could not be ruled out because of the sudden signs of pain. The horse was administered metronidazole (20 mg/kg [9.1 mg/ lb], PO, q 8 h) and penicillin G procaine (22,000 U/kg [10,000 U/lb], IM, q 12 h). The next morning, the horse appeared substantially more comfortable, fully weight bearing on the right forelimb, and swelling in the affected shoulder region had markedly decreased. The dry cold and compression treatments were continued every 12 hours, and the skin incision was cleaned daily. The horse was handwalked for 10 minutes every 12 hours. Three days after initial evaluation, the horse became lethargic and developed colitis evidenced by acute diarrhea and alterations of the CBC. Mild leukopenia (5.1 X 106 WBCs/µL; reference range, 5.5 to 10.5 X 106 WBCs/µL) and neutropenia with a left shift (3.6 X 106 neutrophils/µL; reference range, 4.0 to 7.0 X 106 neutrophils/µL) with 1% band neutrophils were detected, and mild toxic morphologic changes were observed on cytologic smear. At hospital admission, mild leukophilia and neutrophilia (10.9 X 106 WBCs/µL and 8.5 X 106 neutrophils/µL, respectively) had been detected. Penicillin and metronidazole treatments were discontinued, and the horse was given IV fluid therapy and di-tri-octahedral smectitee (0.45 kg [1 lb] in 5 L of water, by nasogastric intubation, q 12 h) for 3 days. Hematologic analysis repeated 4 days after the onset of diarrhea revealed improvement, with mild leukophilia and neutrophilia (10.7 X 106 WBCs/µL and 8.6 X 106 neutrophils/µL, respectively). Fecal samples were submitted for microbial culture and yielded negative results for Clostridium difficile and Clostridium perfringens and Salmonella spp. Additionally, results of C difficile toxin tests were negative. Nine days after initial hospitalization, the horse’s attitude improved, hydration was adequate despite continued diarrhea, and the owners elected to take the horse home. Discharge instructions to the owner at that time included daily cleaning of the incision and bandaging of the right antebrachium with gauze and elasticized bandage material, handwalking for 10 minutes every 12 hours, and monitoring the horse’s diarrhea and water intake. Upon recheck examination 5 days after hospital discharge, the horse was fully weight bearing on the right forelimb, and the diarrhea had resolved. The incision was almost healed with only a mild amount of serous discharge present. Four 288
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Figure 3—Photographs showing the curved, blunt-tipped bistoury knife used for transection of antebrachial fascia (A) and use of the bistoury knife for transection of the caudal antebrachial fascia in horse 1 (B). The blunt tip allowed passage of the instrument deep to the fascia, minimizing concern of inadvertent damage to the deeper musculature. After successful transection of the caudal antebrachial fascia, the knife was reliably palpated beneath the skin. Bar = 5 cm.
years later, the owner reported the horse had some permanent generalized atrophy of its right forelimb musculature, but it walked without signs of pain in the affected limb and was able to be used for breeding. A 17-year-old 466-kg (1,025-lb) Morgan gelding (horse 2) was evaluated at the Veterinary Teaching Hospital at Colorado State University because of an acute onset of severe left forelimb lameness. The horse was used for light pleasure riding. Approximately 2 hours prior to evaluation, the horse was found with the affected forelimb entrapped in a fence. After the horse was freed, severe lameness was observed. Treatment by the referring veterinarian included administration of flunixin meglumine (1.1 mg/kg, IV). Physical examination on admission at the veterinary teaching hospital revealed a heart rate of 52 beats/ min, respiratory rate of 30 breaths/min, and rectal temperature of 38.3°C (101.0°F). The horse was non– weight-bearing on the left forelimb, only the toe of the hoof would contact the ground (American Association of Equine Practitioners lameness grade 5/5), and the affected limb had a dropped elbow appearance. Palpation of the left forelimb revealed no evidence of fracture, but the caudal aspect of the antebrachium was very firm, even with the horse non–weight-bearing on the limb. There was also a moderate amount of soft tissue swelling in the left axilla. Similar to horse 1, clinical examination did not support a diagnosis of radial nerve paralysis, or triceps myopathy. Radiography of the left humerus (lateromedial view), and radius and ulna (craniocaudal and lateroJAVMA, Vol 247, No. 3, August 1, 2015
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medial views) were obtained. There was no evidence of fracture of any of these bones; however, subtle widening on the medial aspect of the humeroradial joint was detected on the craniocaudal view. With concern over possible injury to the medial collateral ligament of the humeroradial joint, radiographic distraction (stress) views were performed. Abducting the distal aspect of the forelimb and putting pressure on the humerus while obtaining the craniocaudal radiographic projection stressed the medial aspect of the joint. The distraction view did not reveal an increase in width on the medial aspect of the humeroradial joint, suggesting the finding indicated a normal variation or there was not a complete rupture of the medial collateral ligament. Ultrasonographic examination of the caudal aspect of the antebrachium revealed ill-defined and diffuse areas of increased echogenicity and marked thickening of the antebrachial flexor muscles (flexor carpi ulnaris and superficial and deep digital flexor muscles) with a coarse and disrupted fiber pattern, compared with findings for the right forelimb (Figure 4). There was no subcutaneous or deep intermuscular fluid accumulation or other observed abnormalities. However, because of local subcutaneous swelling in the axillary region, the proximal aspect of the limb and specifically the medial collateral ligament of the humeroradial joint could not be reliably evaluated. The ultrasonographic changes within the antebrachial flexor muscles of the left forelimb were most consistent with intramuscular hemorrhage and generalized inflammation. Repeated ultrasonographic examination was recommended after the local tissue swelling subsided to better evaluate the medial collateral ligament. On the basis of clinical and diagnostic imaging findings, antebrachial compartment syndrome was suspected. The horse was administered phenylbutazone (4.4 mg/kg [2.0 mg/lb], PO, once) and butorphanol tartrate (0.04 mg/kg, IM, once), and cold hydrotherapy was applied to the left antebrachium for 15 minutes every 6 hours. After hydrotherapy, the limb was dried and diclofenac creamb (7.3 g, topically, q 12 h) was applied to the caudal aspect of the antebrachium. Phenylbutazone was continued (4.4 mg/kg, PO, q 12 h) for the next 48 hours. The horse’s lameness improved shortly after starting medical treatment, and it would periodically bear full weight on the left forelimb; therefore, the medical treatment was continued. However, lameness of the left forelimb was evident when the horse was walked (American Association of Equine Practitioners lameness grade 4/5). After 48 hours, the horse’s lameness did not improve further and the caudal aspect of the antebrachium was subjectively firmer on palpation. For these reasons, a caudal antebrachial fasciotomy was performed. The horse was sedated with detomidine hydrochloride (0.01 mg/kg, IV) and butorphanol tartrate (0.01 mg/kg, IV) and placed in standing stocks. The affected region of the left antebrachium was prepared for surgery and local anesthetic was administered at the planned incision sites as described for horse 1. Two caudolateral incisions (1 distal and 1 proximal) were created in this limb. Approximate locations of these incisions are shown (Figure 2). A 3-cm-long, distal caudolateral incision was made first, approximately 15 cm proximal
Figure 4—Ultrasonographic images of the caudal aspect of the affected left antebrachium (A) and unaffected right antebrachium (B) in horse 2. The image in panel B was obtained at the same level as that in panel A. The ultrasound transducer was placed in transverse orientation relative to the long axis of the limb, 16 cm distal to the olecranon, and centered over the deep digital flexor muscle. Lateral is to the left and caudal to the top in both images. In panel A, notice the ill-defined and diffuse increased echogenicity, marked swelling, and the coarse and disrupted fiber pattern of the deep digital flexor muscle, consistent with intramuscular hemorrhage and generalized inflammation (myositis). Also notice the thickness of the caudal antebrachial fascia (arrow) of the affected limb.
to the level of the accessory carpal bone over the ulnaris lateralis muscle so that it was superficial to the location of firm swelling, but also avoided the ulnar nerve and vasculature (Figure 1). The procedure was performed as described for horse 1, but the fascia remained palpably firm proximal to the extent that could be reached with the bistoury knife. A second (proximal) cauScientific Reports
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dolateral incision was made over the ulnaris lateralis muscle approximately 15 cm distal to the humeroradial joint in the same plane as the first incision. Through the proximal incision, the fascia was transected distally with the bistoury knife until transection of the caudal antebrachial fascia was complete between the 2 skin incisions. After transection, the soft tissues expanded beyond the antebrachial compartment, spreading the edges of the incision approximately 3 cm apart. A mild to moderate amount of hemorrhage discharged from the distal caudolateral incision. After transection of the fascia was complete, there was still palpably firm swelling medially over the flexor carpi ulnaris muscle and the horse still did not bear weight fully on the limb. One additional incision (3 cm in length) was created on the caudomedial aspect of the antebrachium at the same level as the distal caudolateral incision, and this allowed for additional decompression of the swollen muscle. The bleeding stopped within 5 minutes after this incision was created, and all skin incisions were closed with 2-0 polypropylenef in a simple interrupted pattern (no deeper layer sutures were placed). A cotton bandage was applied to the full length of the limb. Immediately following the procedure, the horse was able to fully bear weight on the limb and was not lame at a walk. Horse 2 received trimethoprim-sulfamethoxazole (20 mg/kg, PO, q 12 h) for 10 days, and phenylbutazone (2.2 mg/kg [1.0 mg/lb], PO, q 12 h) was continued for another 5 days. The horse was discharged from the hospital 5 days after initial evaluation with instructions for the owner to change the bandage every 3 days until suture removal at 12 to 14 days after surgery. Short periods of handwalking were encouraged (5 minutes, q 12 h), but the owner was instructed to monitor the horse’s comfort and, if the lameness recurred, to confine the horse to its stall and have it reevaluated. This recommendation was made because the authors were unable to fully examine the medial collateral ligament of the humeroradial joint with ultrasonography and could not rule out injury to this structure. Another ultrasonographic examination was recommended when the horse was returned for suture removal and the axillary swelling had resolved, to better evaluate the medial collateral ligament prior to increasing the horse’s athletic activity. Fourteen days after surgery, the horse underwent suture removal and ultrasonographic examination of the affected antebrachium and axillary region. All incisions were healed. The distal caudolateral incision was mildly swollen, but there was no drainage or signs of pain on palpation, and swelling in the axillary region had resolved. On ultrasonographic examination, the medial collateral ligament of the humeroradial joint was determined to be normal in appearance. Ultrasonographic examination also revealed a marked improvement in swelling of the antebrachial musculature, compared with findings of the prior examination. The horse was fully weight bearing on its left forelimb, but, on occasion, had a stilted gait when walked. The horse was discharged from the hospital with instructions to reinstitute the application of diclofenac for 7 days with light handwalking (5 to 10 minutes twice daily) for 2 weeks. Trimethoprim-sulfamethoxazole administration 290
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was reinstituted at the described dose for another 5 days because of concern that the mild incisional swelling could be an early indication of infection. Two days later, the horse was reevaluated because swelling over the distal caudolateral incision had persisted, and a mild amount of serosanguineous discharge had developed. At this time, the horse was not lame at a walk. Ultrasonographic examination of the region surrounding the incision revealed subcutaneous fluid accumulation extending 2 cm deep to the incision. The incision site was aseptically prepared and a culturette swab was inserted into the draining incision to collect a sample of the subcutaneous fluid. The sample was submitted for aerobic and anaerobic microbial culture and antimicrobial susceptibility testing. The results of the culture revealed a mixed bacterial infection with Pasteurella and nonhemolytic Streptococcus spp. Antimicrobial susceptibility testing results indicated organisms resistant to trimethoprim-sulfamethoxazole, and on the basis of test results, antimicrobial treatment was changed to a prolonged-release antimicrobial: ceftiofur crystalline free acidg (6.6 mg/kg [3 mg/lb], IM, q 4 d) for 2 doses. Four days after the first dose of ceftiofur, the drainage resolved, and normal granulation tissue was present in the incision. No lameness was observed at a walk, and the incision subsequently healed. Eighteen months after the horse was discharged from the hospital, the owner reported that it was walking normally, had no permanent problems with the limb, and was able to return to previous (light pleasure riding) use. Discussion Compartment syndrome results from an increase in volume of anatomic components surrounded within a confined fascial space, leading to increased interstitial pressure and ischemia.2 Increased pressure within the fascial compartment supersedes the minimal elastic capability of the fascia to expand, leading to compression of the encased components.3 If the pressure is not relieved, neuromuscular impairment and necrosis can result.2,3 In horses, antebrachial compartment syndrome typically occurs following trauma, leading to soft tissue swelling, hemorrhage, or fluid accumulation in the fascial compartment,3–5 and has been reported as a complication of anesthetic positioning in 1 horse.6 Conversely, a decrease in size of the fascial compartment secondary to tight bandages, casts, or thermal injury can lead to the syndrome.3 In humans, causes of compartment syndrome include fractures, penetrating trauma, crush injuries, intravenous infiltration injuries, tourniquet application, and snake envenomation.2 Additionally, intramuscular soft tissue neoplasia has led to this syndrome in dogs.7 The caudal fascia of the equine antebrachium is attached caudolaterally to the radius by an intermuscular septum between the common digital extensor and lateral digital extensor muscles and is attached medially to the periosteum of the radius, caudal to the cephalic vein.4 The lateral digital extensor, ulnaris lateralis, deep digital flexor (humeral, ulnar, and radial heads), superficial digital flexor, flexor carpi ulnaris, and flexor carpi radialis muscles are encircled by the antebrachial JAVMA, Vol 247, No. 3, August 1, 2015
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medications and cold hydrotherapy. The decision for surgical intervention is commonly made on the basis of persistent or worsening clinical signs. One report4 described progressively declining detectability of digital pulses as an indication for surgery. However, research in humans has shown that capillary compression is reached before pressure changes exceed mean arterial blood pressure, and alteration in arterial flow distal to the compression might be a poor and late indicator of compartment syndrome.10,13 Although there is a paucity of reports of compartment syndrome in horses, concerns related to postponement of surgical intervention in humans are well documented.2,14,15 In 1 study,15 people with intracompartmental forearm pressures > 55 mm Hg were permanently affected by neuromuscular dysfunction. However, given that tissue damage is related to the duration of compromise, a single pressure measurement may not definitively support the decision to perform fasciotomy or to continue medical treatment.11 In a study14 of human patients who underwent fasciotomy for treatment of compartment syndrome of the forearm, complications developed in 29 of 90 (32%) patients, and there was a significant association between delaying time to fasciotomy and development of complications. An open approach for caudal antebrachial fasciotomy in horses has been described.4,5 An approximately 20- to 30-cm incision is made through the skin, subcutaneous tissues, and caudal antebrachial fascia until pressure is relieved from the compartment.4,5 Caudal antebrachial fasciotomy incisions should be made along the caudolateral aspect of the antebrachium over the ulnaris lateralis muscle, taking care to avoid the ulnar nerve, which courses proximodistally on the caudal aspect of the antebrachium. Considering that there is 1 caudal antebrachial fascial compartment, the caudolateral transection will likely result in successful decompression. The authors were unable to identify other reports specifically documenting the necessity for a caudomedial incision in horses with antebrachial compartment syndrome. The caudomedial incision was made in horse 2 because of our perception of inadequate decompression at the medial aspect of the compartment after the caudolateral incision was created and fasciotomy was performed. The authors believe the swelling in the flexor carpi ulnaris muscle created a need for the caudomedial fasciotomy incision in horse 2. Contact with the ulnar nerve and vessels was avoided by creating the incision at the caudomedial aspect of the limb over the flexor carpi ulnaris muscle. The minimally invasive approach to caudal antebrachial fasciotomy described in this report allowed for a rapid return to weight bearing similar to that described with the open approach.4,5 Our modification of this technique provided for a similar release of the confined swollen musculature4 with a bistoury knife through smaller skin incisions, but other blunt-tipped instruments, including long Metzenbaum scissors, may be considered to accomplish the procedure.16 In humans, an open forearm fasciotomy is considered the gold standard treatment because minimally invasive techniques have been reported to increase the risk of damage to the adjacent ulnar nerve.17 Conversely, some Scientific Reports
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fascia.4,8 The fascia also encases the collateral ulnar vessels, ulnar nerve, and median artery and nerve. The cephalic vein, medial cutaneous antebrachial nerve (branch of musculocutaneous nerve), and common digital extensor and extensor carpi radialis muscles are located superficial to the fascia.4,8 Non–weight-bearing lameness is the predominant clinical sign in cases of antebrachial compartment syndrome in horses4–6 Clinical signs may develop over hours to days, but most horses have abnormalities evident within hours following injury.3–5 Given that extension or flexion of the carpus leads to increased pressure within the antebrachial compartment, horses typically place the affected limb in partial flexion with only the toe touching the ground and may have a dropped elbow appearance.5 Palpation of a firm or tense caudal antebrachial region strongly suggests the diagnosis; however, other causes of severe forelimb lameness, including other causes of the dropped elbow sign (humerus and olecranon fractures, radial nerve paralysis, and triceps myopathy), should be ruled out. Increased intraosseous pressure of the radius has also been reported as a cause of severe non–weight-bearing lameness in 1 horse.9 In that case, no antebrachial soft tissue swelling was observed and the lameness progressed to a non–weightbearing lameness 5 days after the trauma occurred.9 The diagnosis of increased intraosseous pressure in that horse was made by direct intramedullary pressure measurement, detection of increased radiopharmaceutical uptake by the radius on nuclear scintigraphy, and improvement of the lameness following intramedullary decompression.9 The presence of firm antebrachial swelling and the duration before non–weight-bearing lameness could potentially be distinguishing clinical features of antebrachial compartment syndrome and increased intraosseous pressure of the radius. The soft tissue abnormalities detected on ultrasonography in the present report also supported the diagnosis of antebrachial compartment syndrome. Intracompartmental pressures are commonly measured in humans suspected to have forearm compartment syndrome,10,11 but to the authors’ knowledge, this evaluation has only been performed in 1 horse.5 In humans, normal intracompartmental pressures range from 0 to 8 mm Hg, and a difference between diastolic arterial blood pressure and the affected compartment > 30 mm Hg for > 2 hours is strongly suggestive of compartment syndrome.11 Pressure in the affected antebrachial compartment of a horse with antebrachial compartment syndrome was measured at 70 mm Hg prior to surgery and decreased to 35 mm Hg after an open antebrachial fasciotomy.5 In the 2 horses of the present report, ill-defined and diffuse areas of increased echogenicity and swelling within the affected muscles disrupting the normal muscle architecture were observed with ultrasonography. These changes were most consistent with intramuscular hemorrhage and generalized inflammation (myositis). Other causes of increased echogenicity within muscle include fibrosis, fat infiltration, and atrophy, but those changes in echotexture are typically focal and well-defined.12 Medical treatments for compartment syndrome in horses include systemic and topical anti-inflammatory
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authors have reported the safe use of a minimally invasive procedure, with shorter incisions that allowed for a rapid return to full use and improved cosmesis of the affected arm, compared with open fasciotomy.18 Although we are unaware of any direct association between antebrachial compartment syndrome and development of laminitis in horses, it is reasonable to consider that prolonged periods of excessive unilateral weight bearing can predispose horses to laminitis in the supporting limb. One horse described in a clinical report4 died while being managed for laminitis, which was attributed to colitis and endotoxemia that developed 2 days after antebrachial fasciotomy. Another horse that developed antebrachial compartment syndrome as a postanesthetic complication also developed colitis and laminitis after 7 days of medical treatment, and that horse was euthanized.6 We advocate that caudal antebrachial fasciotomy should be considered in horses with severe lameness that does not quickly improve with medical treatment and other clinical findings indicative of compartment syndrome. Although both horses described in this report rapidly returned to full weight bearing after caudal antebrachial fasciotomy, there were some mild signs of discomfort in the affected forelimbs, which appeared to be related to the degree of muscle injury and swelling and resolved over time. After open antebrachial fasciotomy in horses, the incisions are typically closed primarily, leaving the distal portion open to facilitate drainage, with or without the use of a passive drain.4,5 The distal portion of the incision is left to heal by second intention.4,5 Indications for primary skin closure include no tension on the incision and a situation where minimal additional swelling is anticipated.5 Many human patients have delayed primary closure or skin grafting performed.2,10 This appears to be related to the typical necessity for repeated irrigations and debridement of necrotic muscle in affected people.2,14 Although infection developed in 1 incision in horse 2, it quickly resolved with local wound care and adequate antimicrobial treatment. Primary closure of the incisions in horse 2 was not subjectively found to place undue pressure on the released swollen antebrachial musculature and did not seem to affect long-term outcome as compared with that of horse 1 or with 2 horses that underwent open fasciotomy described in other reports.4,5 However, incisional infection may have been related to premature wound closure, and thus delayed primary or second-intention healing of the (distal) incision should be considered for horses undergoing fasciotomy with this minimally invasive approach. a. b.
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Game Ready, Concord, Calif. Surpass, IDEXX Pharmaceuticals Inc, Greensboro, NC.
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c. d. e. f. g.
Curved bistoury knife, Sontec, Centennial, Colo. Laparoscopic scissors, Covidien Surgical, Mansfield, Mass. Bio-sponge, Platinum Performance, Buellton, Calif. Surgipro, Covidien Surgical, Mansfield, Mass. Excede, Zoetis, Madison, NJ.
References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
12. 13. 14. 15. 16.
17. 18.
American Association of Equine Practitioners. Guide for veterinary service and judging of equestrian events. Lexington, Ky: American Association of Equine Practitioners, 1991. Kalyani BS, Fischer BE, Roberts CS, et al. Compartment syndrome of the forearm: a systematic review. J Hand Surg Am 2011;36:535–543. Dahlgren LA. Crush injuries and compartment syndrome. In: Sprayberry KA, Robinson NE, eds. Robinson’s current therapy in equine medicine. 7th ed. St Louis: Elsevier Saunders, 2015;28–30. Sullins KE, Heath RB, Turner AS, et al. Possible antebrachial flexor compartment syndrome as a cause of lameness in two horses. Equine Vet J 1987;19:147–150. Wallace MA, Pleasant RS, Sysel A. Compartment syndrome in a mare. Equine Pract 1996;18:11–14. Norman WM, Williams R, Dodman NH, et al. Postanesthetic compartmental syndrome in a horse. J Am Vet Med Assoc 1989;195:502–504. Maki LC, Kim SE, Winter MD, et al. Compartment syndrome associated with expansile antebrachial tumors in two dogs. J Am Vet Med Assoc 2014;244:346–351. Ashdown RR, Done SH. Color atlas of veterinary anatomy. Philadelphia: Mosby-Wolfe, 2002. Rubio-Martínez LM, Carstens A. Medullary decompression of the radius as a treatment for lameness in a horse. Vet Comp Orthop Traumatol 2013;26:311–317. Mabvuure NT, Malahias M, Hindocha S, et al. Acute compartment syndrome of the limbs: current concepts and management. Open Orthop J 2012;6:535–543. McQueen MM, Duckworth AD, Aitken SA, et al. The estimated sensitivity and specificity of compartment pressure monitoring for acute compartment syndrome. J Bone Joint Surg Am 2013;95:673–677. Peetrons P. Ultrasound of muscles. Eur Radiol 2002;12:35–43. Woodhouse JB, McNally EG. Ultrasound of skeletal muscle injury: an update. Semin Ultrasound CT MR 2011;32:91–100. Duckworth AD, Mitchell SE, Molyneux SG, et al. Acute compartment syndrome of the forearm. J Bone Joint Surg Am 2012;94:e63. Matsen FA, Winquist RA, Krugmire RB. Diagnosis and management of compartmental syndromes. J Bone Joint Surg Am 1980;62:286–291. Hanson RR, Gaughan EM, Grenager NS, et al. Burns, acute soft tissue swellings, pigeon fever, and fasciotomy In: Orsini JA, Divers TJ, eds. Equine emergencies: treatments and procedures. St Louis: Elsevier Saunders, 2014;608–625. Croutzet P, Chassat R, Masmejean EH. Mini-invasive surgery for chronic exertional compartment syndrome of the forearm: a new technique. Tech Hand Up Extrem Surg 2009;13:137–140. Harrison JWK, Thomas P, Aster A, et al. Chronic exertional compartment syndrome of the forearm in elite rowers: a technique for mini-open fasciotomy and a report of six cases. Hand (N Y) 2013;8:450–453.
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Case Description—An 18-year-old Paint stallion (horse 1) and a 17-year-old Morgan gelding (horse 2) were evaluated because of an acute onset of severe unilateral forelimb lameness. Clinical Findings—Both horses were unable to bear weight on the affected forelimb and had a dropped elbow appearance. Radial nerve paralysis, triceps myopathy, and fractures of the humerus and ulna were ruled out. The caudal aspect of the affected antebrachium of each horse was very firm to palpation and became firmer when weight was shifted onto the limb. Ultrasonographic examination revealed swelling and suspected intramuscular hemorrhage of the caudal antebrachial muscles. On the basis of clinical examination and diagnostic imaging findings, both horses had antebrachial compartment syndrome diagnosed. Lameness did not substantially improve with medical treatment in either horse. Treatment and Outcome—Caudal antebrachial fasciotomy was performed in each horse. Following sedation and local anesthetic administration, a bistoury knife was inserted through small incisions to perform fasciotomy. Horses remained standing throughout the procedure and were immediately able to bear weight on the affected limb without signs of discomfort. Horse 1 developed colitis and horse 2 developed a mild incisional infection, but both fully recovered and returned to their previous activities. Clinical Relevance—Antebrachial compartment syndrome is a rare cause of severe unilateral forelimb lameness and should be considered as a differential diagnosis in horses with a dropped elbow appearance. Both horses of this report had a successful outcome following antebrachial fasciotomy. (J Am Vet Med Assoc 2015;247:286–292)
A
n 18-year-old 640-kg (1,408-lb) Paint stallion (horse 1) was evaluated at the Veterinary Teaching Hospital at Washington State University because of an acute onset of severe right forelimb lameness. The horse had been primarily used for breeding and was found in the owner’s pasture with severe lameness 2 hours prior to the examination. The horse’s heart rate was 52 beats/min, respiratory rate was 28 breaths/min, and temperature was 36.7°C (98.1°F). The horse had a right forelimb lameness that was graded 5/5 according to the American Association of Equine Practitioners scale.1 There was a moderate amount of swelling in the right shoulder, and the olecranon tuberosity was displaced distally (dropped elbow sign). The caudal aspect of the antebrachium was very firm to palpation and became even firmer as the horse attempted to bear weight on the limb. Moderate signs of pain were elicited during palpation, with the horse retracting the limb. The horse was able to advance the affected limb cranially From the Departments of Clinical Sciences (Nelson, Hendrickson) and Environmental and Radiological Health Sciences (Barrett), College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523; and the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164 (Ragle). The authors thank Drs. Chris McKay and Greg Roberts for expertise with the ultrasonographic examinations, Drs. L. Nicki Wise and Kathy Seino for case management (horse 1), and Dr. Mustafa Elarbi for illustrations. Address correspondence to Dr. Nelson ([email protected]). 286
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and place its hoof on the ground, suggesting complete radial nerve paralysis was not the cause of the dropped elbow sign. Moreover, the triceps musculature was not firm on palpation and this examination did not elicit signs of pain, suggesting triceps myopathy was not the cause of the dropped elbow sign. The amount of firm and painful soft tissue swelling palpable on the caudal aspect of the antebrachium was consistent with antebrachial compartment syndrome. Radiography of the right humerus (lateromedial view) and radius and ulna (craniocaudal and lateromedial views) was performed and did not reveal evidence of fracture. Ultrasonographic examination of the right antebrachium revealed ill-defined and diffuse areas of increased echogenicity, swelling, and disruption of normal architecture within the superficial and deep digital flexor muscles, compared with the left antebrachium. These findings were most consistent with intramuscular hemorrhage and generalized inflammation. On the basis of clinical examination and diagnostic imaging findings, a presumptive diagnosis of antebrachial compartment syndrome was made. Treatment of the right forelimb included dry cold and active compressiona for 15 minutes every 12 hours, and topical application of 1% diclofenac sodium creamb to the caudal aspect of the antebrachium. The horse also received flunixin meglumine (1.1 mg/kg [0.5 mg/lb], IV, once) and butorphanol tartrate (0.04 mg/kg [0.018 mg/lb], IM, once). Twelve hours later, JAVMA, Vol 247, No. 3, August 1, 2015
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the horse’s lameness had slightly improved (grade 4/5), but signs of pain were still elicited by palpation of the caudal antebrachial region. Caudal antebrachial fasciotomy was performed because of the lack of appreciable improvement with medical treatment. The horse was placed in standing stocks and sedated with xylazine hydrochloride (0.3 mg/kg [0.14 mg/lb], IV) and butorphanol tartrate (0.01 mg/kg [0.005 mg/lb], IV). The right antebrachium was clipped of hair and aseptically prepared for surgery. A line block was performed by administration of 2% mepivacaine hydrochloride solution at the approximate level of the midradius on the caudolateral aspect of the limb, over the ulnaris lateralis muscle. The local anesthetic was injected into the skin and subcutis, deposited over a length of 5 cm in the proximodistal direction at the planned incision site, followed by injection deeper into the caudal antebrachial fascia. Additionally, local anesthetic was deposited into the caudal antebrachial fascia (beneath the subcutis) at 5-cm increments proximal and distal to the planned in- Figure 1—Illustration of the cross-sectional anatomy of the equine antebrachium at the level of the The location of the cross-section is depicted as the transverse line in the image insert. cision, along the intended transection midradius. The extensor carpi radialis and common digital extensor muscles, cephalic vein, and medial cutasite. The site of the planned incision neous antebrachial nerve are the only soft tissue structures not encased within the antebrachial was at a location that avoided the ul- fascia. The radial head of the deep digital flexor muscle is encased within the antebrachial fascia is not shown; this structure becomes apparent distal to the midradius between the caudal nar nerve and antebrachial vascula- but aspect of the radius and cranial aspect of the humeral head (short component) of the deep digital ture (Figure 1). An incision 3 cm in flexor muscle. The ulnar head of the deep digital flexor muscle is present proximal to the level of length was made in the skin over the the cross section, but by midradius extends distally as a tendon. DDF = Deep digital flexor. local block with a No. 10 blade and extended through the subcutaneous tissues and caudal antebrachial fascia (Figure 2). The caudal antebrachial fascia was easily distinguished from the subcutaneous tissues and deeper musculature owing to its firmness on palpation and bright white appearance. A curved, blunt-tipped bistoury knifec (Figure 3) was inserted into the incision, deep to the caudal antebrachial fascia. The instrument was oriented proximodistally (with the tip of the blade most proximal), and the 5-cm blade and most of its thin handle were inserted and pulled caudally to transect the fascia, leaving the skin intact. This provided transection of the fascia approximately 10 cm proximal to the incision. Then, the instrument was oriented distoproximally, and the procedure was repeated to transect the tight caudal antebrachial fascia distal to the incision. At this point, the fascia was still palpably firm proximally, beyond the length of the bistoury knife. Laparoscopic scissorsd were used, with the tip inserted through the same incision, to transect the remaining fascia proximally until it was no longer Figure 2—Photograph of the right forelimb of an 18-year-old Paint stallion with antebrachial compartment syndrome (horse 1). Cranial is to tight on palpation. After transection, the restricted and the right. Notice the 3-cm-long incision made on the caudolateral aspect swollen musculature expanded beyond the antebrachial of the limb allowing insertion of a bistoury knife for transection of the compartment, spreading the edges of the incision apcaudal antebrachial fascia. The yellow lines represent the approximate locations of 2 caudolateral incisions made on the left antebrachium of a proximately 3 cm apart. A mild amount of hemorrhage 17-year-old Morgan gelding that underwent similar treatment for antedischarged from the incision, and the incision was left brachial compartment syndrome (horse 2). A third incision (location not open to facilitate drainage. A light bandage made with shown) was made on the caudomedial aspect of the affected forelimb roll gauze and elasticized bandage material was applied of horse 2 at the same level as the distal caudolateral incision.
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to the antebrachium. Immediately following transection of the caudal antebrachial fascia, the horse could fully weight bear on the right forelimb, and after bandaging it walked back to the stall without lameness. Eight hours later, the horse had signs of pain on palpation of the right forelimb. The right shoulder and triceps musculature were moderately swollen. Ultrasonographic examination of the affected region revealed gas within the muscle fascia planes, and although subcutaneous gas migration following surgery was considered, clostridial myositis could not be ruled out because of the sudden signs of pain. The horse was administered metronidazole (20 mg/kg [9.1 mg/ lb], PO, q 8 h) and penicillin G procaine (22,000 U/kg [10,000 U/lb], IM, q 12 h). The next morning, the horse appeared substantially more comfortable, fully weight bearing on the right forelimb, and swelling in the affected shoulder region had markedly decreased. The dry cold and compression treatments were continued every 12 hours, and the skin incision was cleaned daily. The horse was handwalked for 10 minutes every 12 hours. Three days after initial evaluation, the horse became lethargic and developed colitis evidenced by acute diarrhea and alterations of the CBC. Mild leukopenia (5.1 X 106 WBCs/µL; reference range, 5.5 to 10.5 X 106 WBCs/µL) and neutropenia with a left shift (3.6 X 106 neutrophils/µL; reference range, 4.0 to 7.0 X 106 neutrophils/µL) with 1% band neutrophils were detected, and mild toxic morphologic changes were observed on cytologic smear. At hospital admission, mild leukophilia and neutrophilia (10.9 X 106 WBCs/µL and 8.5 X 106 neutrophils/µL, respectively) had been detected. Penicillin and metronidazole treatments were discontinued, and the horse was given IV fluid therapy and di-tri-octahedral smectitee (0.45 kg [1 lb] in 5 L of water, by nasogastric intubation, q 12 h) for 3 days. Hematologic analysis repeated 4 days after the onset of diarrhea revealed improvement, with mild leukophilia and neutrophilia (10.7 X 106 WBCs/µL and 8.6 X 106 neutrophils/µL, respectively). Fecal samples were submitted for microbial culture and yielded negative results for Clostridium difficile and Clostridium perfringens and Salmonella spp. Additionally, results of C difficile toxin tests were negative. Nine days after initial hospitalization, the horse’s attitude improved, hydration was adequate despite continued diarrhea, and the owners elected to take the horse home. Discharge instructions to the owner at that time included daily cleaning of the incision and bandaging of the right antebrachium with gauze and elasticized bandage material, handwalking for 10 minutes every 12 hours, and monitoring the horse’s diarrhea and water intake. Upon recheck examination 5 days after hospital discharge, the horse was fully weight bearing on the right forelimb, and the diarrhea had resolved. The incision was almost healed with only a mild amount of serous discharge present. Four 288
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Figure 3—Photographs showing the curved, blunt-tipped bistoury knife used for transection of antebrachial fascia (A) and use of the bistoury knife for transection of the caudal antebrachial fascia in horse 1 (B). The blunt tip allowed passage of the instrument deep to the fascia, minimizing concern of inadvertent damage to the deeper musculature. After successful transection of the caudal antebrachial fascia, the knife was reliably palpated beneath the skin. Bar = 5 cm.
years later, the owner reported the horse had some permanent generalized atrophy of its right forelimb musculature, but it walked without signs of pain in the affected limb and was able to be used for breeding. A 17-year-old 466-kg (1,025-lb) Morgan gelding (horse 2) was evaluated at the Veterinary Teaching Hospital at Colorado State University because of an acute onset of severe left forelimb lameness. The horse was used for light pleasure riding. Approximately 2 hours prior to evaluation, the horse was found with the affected forelimb entrapped in a fence. After the horse was freed, severe lameness was observed. Treatment by the referring veterinarian included administration of flunixin meglumine (1.1 mg/kg, IV). Physical examination on admission at the veterinary teaching hospital revealed a heart rate of 52 beats/ min, respiratory rate of 30 breaths/min, and rectal temperature of 38.3°C (101.0°F). The horse was non– weight-bearing on the left forelimb, only the toe of the hoof would contact the ground (American Association of Equine Practitioners lameness grade 5/5), and the affected limb had a dropped elbow appearance. Palpation of the left forelimb revealed no evidence of fracture, but the caudal aspect of the antebrachium was very firm, even with the horse non–weight-bearing on the limb. There was also a moderate amount of soft tissue swelling in the left axilla. Similar to horse 1, clinical examination did not support a diagnosis of radial nerve paralysis, or triceps myopathy. Radiography of the left humerus (lateromedial view), and radius and ulna (craniocaudal and lateroJAVMA, Vol 247, No. 3, August 1, 2015
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medial views) were obtained. There was no evidence of fracture of any of these bones; however, subtle widening on the medial aspect of the humeroradial joint was detected on the craniocaudal view. With concern over possible injury to the medial collateral ligament of the humeroradial joint, radiographic distraction (stress) views were performed. Abducting the distal aspect of the forelimb and putting pressure on the humerus while obtaining the craniocaudal radiographic projection stressed the medial aspect of the joint. The distraction view did not reveal an increase in width on the medial aspect of the humeroradial joint, suggesting the finding indicated a normal variation or there was not a complete rupture of the medial collateral ligament. Ultrasonographic examination of the caudal aspect of the antebrachium revealed ill-defined and diffuse areas of increased echogenicity and marked thickening of the antebrachial flexor muscles (flexor carpi ulnaris and superficial and deep digital flexor muscles) with a coarse and disrupted fiber pattern, compared with findings for the right forelimb (Figure 4). There was no subcutaneous or deep intermuscular fluid accumulation or other observed abnormalities. However, because of local subcutaneous swelling in the axillary region, the proximal aspect of the limb and specifically the medial collateral ligament of the humeroradial joint could not be reliably evaluated. The ultrasonographic changes within the antebrachial flexor muscles of the left forelimb were most consistent with intramuscular hemorrhage and generalized inflammation. Repeated ultrasonographic examination was recommended after the local tissue swelling subsided to better evaluate the medial collateral ligament. On the basis of clinical and diagnostic imaging findings, antebrachial compartment syndrome was suspected. The horse was administered phenylbutazone (4.4 mg/kg [2.0 mg/lb], PO, once) and butorphanol tartrate (0.04 mg/kg, IM, once), and cold hydrotherapy was applied to the left antebrachium for 15 minutes every 6 hours. After hydrotherapy, the limb was dried and diclofenac creamb (7.3 g, topically, q 12 h) was applied to the caudal aspect of the antebrachium. Phenylbutazone was continued (4.4 mg/kg, PO, q 12 h) for the next 48 hours. The horse’s lameness improved shortly after starting medical treatment, and it would periodically bear full weight on the left forelimb; therefore, the medical treatment was continued. However, lameness of the left forelimb was evident when the horse was walked (American Association of Equine Practitioners lameness grade 4/5). After 48 hours, the horse’s lameness did not improve further and the caudal aspect of the antebrachium was subjectively firmer on palpation. For these reasons, a caudal antebrachial fasciotomy was performed. The horse was sedated with detomidine hydrochloride (0.01 mg/kg, IV) and butorphanol tartrate (0.01 mg/kg, IV) and placed in standing stocks. The affected region of the left antebrachium was prepared for surgery and local anesthetic was administered at the planned incision sites as described for horse 1. Two caudolateral incisions (1 distal and 1 proximal) were created in this limb. Approximate locations of these incisions are shown (Figure 2). A 3-cm-long, distal caudolateral incision was made first, approximately 15 cm proximal
Figure 4—Ultrasonographic images of the caudal aspect of the affected left antebrachium (A) and unaffected right antebrachium (B) in horse 2. The image in panel B was obtained at the same level as that in panel A. The ultrasound transducer was placed in transverse orientation relative to the long axis of the limb, 16 cm distal to the olecranon, and centered over the deep digital flexor muscle. Lateral is to the left and caudal to the top in both images. In panel A, notice the ill-defined and diffuse increased echogenicity, marked swelling, and the coarse and disrupted fiber pattern of the deep digital flexor muscle, consistent with intramuscular hemorrhage and generalized inflammation (myositis). Also notice the thickness of the caudal antebrachial fascia (arrow) of the affected limb.
to the level of the accessory carpal bone over the ulnaris lateralis muscle so that it was superficial to the location of firm swelling, but also avoided the ulnar nerve and vasculature (Figure 1). The procedure was performed as described for horse 1, but the fascia remained palpably firm proximal to the extent that could be reached with the bistoury knife. A second (proximal) cauScientific Reports
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dolateral incision was made over the ulnaris lateralis muscle approximately 15 cm distal to the humeroradial joint in the same plane as the first incision. Through the proximal incision, the fascia was transected distally with the bistoury knife until transection of the caudal antebrachial fascia was complete between the 2 skin incisions. After transection, the soft tissues expanded beyond the antebrachial compartment, spreading the edges of the incision approximately 3 cm apart. A mild to moderate amount of hemorrhage discharged from the distal caudolateral incision. After transection of the fascia was complete, there was still palpably firm swelling medially over the flexor carpi ulnaris muscle and the horse still did not bear weight fully on the limb. One additional incision (3 cm in length) was created on the caudomedial aspect of the antebrachium at the same level as the distal caudolateral incision, and this allowed for additional decompression of the swollen muscle. The bleeding stopped within 5 minutes after this incision was created, and all skin incisions were closed with 2-0 polypropylenef in a simple interrupted pattern (no deeper layer sutures were placed). A cotton bandage was applied to the full length of the limb. Immediately following the procedure, the horse was able to fully bear weight on the limb and was not lame at a walk. Horse 2 received trimethoprim-sulfamethoxazole (20 mg/kg, PO, q 12 h) for 10 days, and phenylbutazone (2.2 mg/kg [1.0 mg/lb], PO, q 12 h) was continued for another 5 days. The horse was discharged from the hospital 5 days after initial evaluation with instructions for the owner to change the bandage every 3 days until suture removal at 12 to 14 days after surgery. Short periods of handwalking were encouraged (5 minutes, q 12 h), but the owner was instructed to monitor the horse’s comfort and, if the lameness recurred, to confine the horse to its stall and have it reevaluated. This recommendation was made because the authors were unable to fully examine the medial collateral ligament of the humeroradial joint with ultrasonography and could not rule out injury to this structure. Another ultrasonographic examination was recommended when the horse was returned for suture removal and the axillary swelling had resolved, to better evaluate the medial collateral ligament prior to increasing the horse’s athletic activity. Fourteen days after surgery, the horse underwent suture removal and ultrasonographic examination of the affected antebrachium and axillary region. All incisions were healed. The distal caudolateral incision was mildly swollen, but there was no drainage or signs of pain on palpation, and swelling in the axillary region had resolved. On ultrasonographic examination, the medial collateral ligament of the humeroradial joint was determined to be normal in appearance. Ultrasonographic examination also revealed a marked improvement in swelling of the antebrachial musculature, compared with findings of the prior examination. The horse was fully weight bearing on its left forelimb, but, on occasion, had a stilted gait when walked. The horse was discharged from the hospital with instructions to reinstitute the application of diclofenac for 7 days with light handwalking (5 to 10 minutes twice daily) for 2 weeks. Trimethoprim-sulfamethoxazole administration 290
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was reinstituted at the described dose for another 5 days because of concern that the mild incisional swelling could be an early indication of infection. Two days later, the horse was reevaluated because swelling over the distal caudolateral incision had persisted, and a mild amount of serosanguineous discharge had developed. At this time, the horse was not lame at a walk. Ultrasonographic examination of the region surrounding the incision revealed subcutaneous fluid accumulation extending 2 cm deep to the incision. The incision site was aseptically prepared and a culturette swab was inserted into the draining incision to collect a sample of the subcutaneous fluid. The sample was submitted for aerobic and anaerobic microbial culture and antimicrobial susceptibility testing. The results of the culture revealed a mixed bacterial infection with Pasteurella and nonhemolytic Streptococcus spp. Antimicrobial susceptibility testing results indicated organisms resistant to trimethoprim-sulfamethoxazole, and on the basis of test results, antimicrobial treatment was changed to a prolonged-release antimicrobial: ceftiofur crystalline free acidg (6.6 mg/kg [3 mg/lb], IM, q 4 d) for 2 doses. Four days after the first dose of ceftiofur, the drainage resolved, and normal granulation tissue was present in the incision. No lameness was observed at a walk, and the incision subsequently healed. Eighteen months after the horse was discharged from the hospital, the owner reported that it was walking normally, had no permanent problems with the limb, and was able to return to previous (light pleasure riding) use. Discussion Compartment syndrome results from an increase in volume of anatomic components surrounded within a confined fascial space, leading to increased interstitial pressure and ischemia.2 Increased pressure within the fascial compartment supersedes the minimal elastic capability of the fascia to expand, leading to compression of the encased components.3 If the pressure is not relieved, neuromuscular impairment and necrosis can result.2,3 In horses, antebrachial compartment syndrome typically occurs following trauma, leading to soft tissue swelling, hemorrhage, or fluid accumulation in the fascial compartment,3–5 and has been reported as a complication of anesthetic positioning in 1 horse.6 Conversely, a decrease in size of the fascial compartment secondary to tight bandages, casts, or thermal injury can lead to the syndrome.3 In humans, causes of compartment syndrome include fractures, penetrating trauma, crush injuries, intravenous infiltration injuries, tourniquet application, and snake envenomation.2 Additionally, intramuscular soft tissue neoplasia has led to this syndrome in dogs.7 The caudal fascia of the equine antebrachium is attached caudolaterally to the radius by an intermuscular septum between the common digital extensor and lateral digital extensor muscles and is attached medially to the periosteum of the radius, caudal to the cephalic vein.4 The lateral digital extensor, ulnaris lateralis, deep digital flexor (humeral, ulnar, and radial heads), superficial digital flexor, flexor carpi ulnaris, and flexor carpi radialis muscles are encircled by the antebrachial JAVMA, Vol 247, No. 3, August 1, 2015
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medications and cold hydrotherapy. The decision for surgical intervention is commonly made on the basis of persistent or worsening clinical signs. One report4 described progressively declining detectability of digital pulses as an indication for surgery. However, research in humans has shown that capillary compression is reached before pressure changes exceed mean arterial blood pressure, and alteration in arterial flow distal to the compression might be a poor and late indicator of compartment syndrome.10,13 Although there is a paucity of reports of compartment syndrome in horses, concerns related to postponement of surgical intervention in humans are well documented.2,14,15 In 1 study,15 people with intracompartmental forearm pressures > 55 mm Hg were permanently affected by neuromuscular dysfunction. However, given that tissue damage is related to the duration of compromise, a single pressure measurement may not definitively support the decision to perform fasciotomy or to continue medical treatment.11 In a study14 of human patients who underwent fasciotomy for treatment of compartment syndrome of the forearm, complications developed in 29 of 90 (32%) patients, and there was a significant association between delaying time to fasciotomy and development of complications. An open approach for caudal antebrachial fasciotomy in horses has been described.4,5 An approximately 20- to 30-cm incision is made through the skin, subcutaneous tissues, and caudal antebrachial fascia until pressure is relieved from the compartment.4,5 Caudal antebrachial fasciotomy incisions should be made along the caudolateral aspect of the antebrachium over the ulnaris lateralis muscle, taking care to avoid the ulnar nerve, which courses proximodistally on the caudal aspect of the antebrachium. Considering that there is 1 caudal antebrachial fascial compartment, the caudolateral transection will likely result in successful decompression. The authors were unable to identify other reports specifically documenting the necessity for a caudomedial incision in horses with antebrachial compartment syndrome. The caudomedial incision was made in horse 2 because of our perception of inadequate decompression at the medial aspect of the compartment after the caudolateral incision was created and fasciotomy was performed. The authors believe the swelling in the flexor carpi ulnaris muscle created a need for the caudomedial fasciotomy incision in horse 2. Contact with the ulnar nerve and vessels was avoided by creating the incision at the caudomedial aspect of the limb over the flexor carpi ulnaris muscle. The minimally invasive approach to caudal antebrachial fasciotomy described in this report allowed for a rapid return to weight bearing similar to that described with the open approach.4,5 Our modification of this technique provided for a similar release of the confined swollen musculature4 with a bistoury knife through smaller skin incisions, but other blunt-tipped instruments, including long Metzenbaum scissors, may be considered to accomplish the procedure.16 In humans, an open forearm fasciotomy is considered the gold standard treatment because minimally invasive techniques have been reported to increase the risk of damage to the adjacent ulnar nerve.17 Conversely, some Scientific Reports
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fascia.4,8 The fascia also encases the collateral ulnar vessels, ulnar nerve, and median artery and nerve. The cephalic vein, medial cutaneous antebrachial nerve (branch of musculocutaneous nerve), and common digital extensor and extensor carpi radialis muscles are located superficial to the fascia.4,8 Non–weight-bearing lameness is the predominant clinical sign in cases of antebrachial compartment syndrome in horses4–6 Clinical signs may develop over hours to days, but most horses have abnormalities evident within hours following injury.3–5 Given that extension or flexion of the carpus leads to increased pressure within the antebrachial compartment, horses typically place the affected limb in partial flexion with only the toe touching the ground and may have a dropped elbow appearance.5 Palpation of a firm or tense caudal antebrachial region strongly suggests the diagnosis; however, other causes of severe forelimb lameness, including other causes of the dropped elbow sign (humerus and olecranon fractures, radial nerve paralysis, and triceps myopathy), should be ruled out. Increased intraosseous pressure of the radius has also been reported as a cause of severe non–weight-bearing lameness in 1 horse.9 In that case, no antebrachial soft tissue swelling was observed and the lameness progressed to a non–weightbearing lameness 5 days after the trauma occurred.9 The diagnosis of increased intraosseous pressure in that horse was made by direct intramedullary pressure measurement, detection of increased radiopharmaceutical uptake by the radius on nuclear scintigraphy, and improvement of the lameness following intramedullary decompression.9 The presence of firm antebrachial swelling and the duration before non–weight-bearing lameness could potentially be distinguishing clinical features of antebrachial compartment syndrome and increased intraosseous pressure of the radius. The soft tissue abnormalities detected on ultrasonography in the present report also supported the diagnosis of antebrachial compartment syndrome. Intracompartmental pressures are commonly measured in humans suspected to have forearm compartment syndrome,10,11 but to the authors’ knowledge, this evaluation has only been performed in 1 horse.5 In humans, normal intracompartmental pressures range from 0 to 8 mm Hg, and a difference between diastolic arterial blood pressure and the affected compartment > 30 mm Hg for > 2 hours is strongly suggestive of compartment syndrome.11 Pressure in the affected antebrachial compartment of a horse with antebrachial compartment syndrome was measured at 70 mm Hg prior to surgery and decreased to 35 mm Hg after an open antebrachial fasciotomy.5 In the 2 horses of the present report, ill-defined and diffuse areas of increased echogenicity and swelling within the affected muscles disrupting the normal muscle architecture were observed with ultrasonography. These changes were most consistent with intramuscular hemorrhage and generalized inflammation (myositis). Other causes of increased echogenicity within muscle include fibrosis, fat infiltration, and atrophy, but those changes in echotexture are typically focal and well-defined.12 Medical treatments for compartment syndrome in horses include systemic and topical anti-inflammatory
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authors have reported the safe use of a minimally invasive procedure, with shorter incisions that allowed for a rapid return to full use and improved cosmesis of the affected arm, compared with open fasciotomy.18 Although we are unaware of any direct association between antebrachial compartment syndrome and development of laminitis in horses, it is reasonable to consider that prolonged periods of excessive unilateral weight bearing can predispose horses to laminitis in the supporting limb. One horse described in a clinical report4 died while being managed for laminitis, which was attributed to colitis and endotoxemia that developed 2 days after antebrachial fasciotomy. Another horse that developed antebrachial compartment syndrome as a postanesthetic complication also developed colitis and laminitis after 7 days of medical treatment, and that horse was euthanized.6 We advocate that caudal antebrachial fasciotomy should be considered in horses with severe lameness that does not quickly improve with medical treatment and other clinical findings indicative of compartment syndrome. Although both horses described in this report rapidly returned to full weight bearing after caudal antebrachial fasciotomy, there were some mild signs of discomfort in the affected forelimbs, which appeared to be related to the degree of muscle injury and swelling and resolved over time. After open antebrachial fasciotomy in horses, the incisions are typically closed primarily, leaving the distal portion open to facilitate drainage, with or without the use of a passive drain.4,5 The distal portion of the incision is left to heal by second intention.4,5 Indications for primary skin closure include no tension on the incision and a situation where minimal additional swelling is anticipated.5 Many human patients have delayed primary closure or skin grafting performed.2,10 This appears to be related to the typical necessity for repeated irrigations and debridement of necrotic muscle in affected people.2,14 Although infection developed in 1 incision in horse 2, it quickly resolved with local wound care and adequate antimicrobial treatment. Primary closure of the incisions in horse 2 was not subjectively found to place undue pressure on the released swollen antebrachial musculature and did not seem to affect long-term outcome as compared with that of horse 1 or with 2 horses that underwent open fasciotomy described in other reports.4,5 However, incisional infection may have been related to premature wound closure, and thus delayed primary or second-intention healing of the (distal) incision should be considered for horses undergoing fasciotomy with this minimally invasive approach. a. b.
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Game Ready, Concord, Calif. Surpass, IDEXX Pharmaceuticals Inc, Greensboro, NC.
Scientific Reports
c. d. e. f. g.
Curved bistoury knife, Sontec, Centennial, Colo. Laparoscopic scissors, Covidien Surgical, Mansfield, Mass. Bio-sponge, Platinum Performance, Buellton, Calif. Surgipro, Covidien Surgical, Mansfield, Mass. Excede, Zoetis, Madison, NJ.
References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
12. 13. 14. 15. 16.
17. 18.
American Association of Equine Practitioners. Guide for veterinary service and judging of equestrian events. Lexington, Ky: American Association of Equine Practitioners, 1991. Kalyani BS, Fischer BE, Roberts CS, et al. Compartment syndrome of the forearm: a systematic review. J Hand Surg Am 2011;36:535–543. Dahlgren LA. Crush injuries and compartment syndrome. In: Sprayberry KA, Robinson NE, eds. Robinson’s current therapy in equine medicine. 7th ed. St Louis: Elsevier Saunders, 2015;28–30. Sullins KE, Heath RB, Turner AS, et al. Possible antebrachial flexor compartment syndrome as a cause of lameness in two horses. Equine Vet J 1987;19:147–150. Wallace MA, Pleasant RS, Sysel A. Compartment syndrome in a mare. Equine Pract 1996;18:11–14. Norman WM, Williams R, Dodman NH, et al. Postanesthetic compartmental syndrome in a horse. J Am Vet Med Assoc 1989;195:502–504. Maki LC, Kim SE, Winter MD, et al. Compartment syndrome associated with expansile antebrachial tumors in two dogs. J Am Vet Med Assoc 2014;244:346–351. Ashdown RR, Done SH. Color atlas of veterinary anatomy. Philadelphia: Mosby-Wolfe, 2002. Rubio-Martínez LM, Carstens A. Medullary decompression of the radius as a treatment for lameness in a horse. Vet Comp Orthop Traumatol 2013;26:311–317. Mabvuure NT, Malahias M, Hindocha S, et al. Acute compartment syndrome of the limbs: current concepts and management. Open Orthop J 2012;6:535–543. McQueen MM, Duckworth AD, Aitken SA, et al. The estimated sensitivity and specificity of compartment pressure monitoring for acute compartment syndrome. J Bone Joint Surg Am 2013;95:673–677. Peetrons P. Ultrasound of muscles. Eur Radiol 2002;12:35–43. Woodhouse JB, McNally EG. Ultrasound of skeletal muscle injury: an update. Semin Ultrasound CT MR 2011;32:91–100. Duckworth AD, Mitchell SE, Molyneux SG, et al. Acute compartment syndrome of the forearm. J Bone Joint Surg Am 2012;94:e63. Matsen FA, Winquist RA, Krugmire RB. Diagnosis and management of compartmental syndromes. J Bone Joint Surg Am 1980;62:286–291. Hanson RR, Gaughan EM, Grenager NS, et al. Burns, acute soft tissue swellings, pigeon fever, and fasciotomy In: Orsini JA, Divers TJ, eds. Equine emergencies: treatments and procedures. St Louis: Elsevier Saunders, 2014;608–625. Croutzet P, Chassat R, Masmejean EH. Mini-invasive surgery for chronic exertional compartment syndrome of the forearm: a new technique. Tech Hand Up Extrem Surg 2009;13:137–140. Harrison JWK, Thomas P, Aster A, et al. Chronic exertional compartment syndrome of the forearm in elite rowers: a technique for mini-open fasciotomy and a report of six cases. Hand (N Y) 2013;8:450–453.
JAVMA, Vol 247, No. 3, August 1, 2015
