Veterinary Ophthalmology (2014) 17, Supplement 1, 97–106
DOI:10.1111/vop.12162
Equine orbital fractures: a review of 18 cases (2006–2013) Joseph C. Gerding, Alison Clode, Brian C. Gilger and Keith W. Montgomery Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, 1052 William Moore Drive, Raleigh, NC, 27607, United States
Address communications to: Keith W. Montgomery Tel.: 919-513-6659 Fax: 919-513-6711 e-mail: [email protected]
Objective To review the clinical features, treatments, complications, and outcomes of horses with traumatic orbital fractures. Study design Retrospective study. Sample Population Eighteen horses with confirmed orbital fractures. Procedures Medical records of horses presenting with orbital fractures between 2006 and 2013 were reviewed. Signalment, etiology of fracture, clinical signs, fracture descriptions, diagnostic imaging, treatments, complications, and outcomes were evaluated. Results Eighteen horses presented with orbital fractures resulting from rearing in a confined space (n = 5), being kicked (4), colliding with a stationary object (3), and unknown trauma (6). Radiography and computed tomography were effective at classifying fractures and evaluating sinus/nasal involvement. Epistaxis/sinusitis were associated with fractures of the zygomatic process of the temporal bone (n = 3) and comminuted fractures of multiple bones (5). Seventeen fractures required treatment, with fifteen receiving a combination of medical and surgical therapy. Surgery included reduction of large bony fragments (n = 8), removal of small fragments (12), stabilization with a wire implant (1), and sinus trephination and lavage (5). Factors contributing to a favorable outcome included: globe retention (n = 16), vision (14), comfort (15), cosmesis (9), and return to previous function (13). Conclusions Horses sustaining orbital fractures treated promptly with medical and surgical therapy have a favorable prognosis for return to function and cosmesis. Fractures affecting the zygomatic process of the frontal bone are unlikely to involve the sinus/nasal cavities. Epistaxis and sinusitis warrant more aggressive therapy and decrease functional and cosmetic outcome. Key Words: Complication, equine, fracture, orbital, outcome, retrospective
INTRODUCTION
The equine eye is protected by a complete, bony orbital rim formed by the frontal bone (dorsally), lacrimal bone (medially), zygomatic bone (ventrally), and temporal bone (laterally).1 The frontal process of the zygomatic bone and zygomatic processes of the frontal and temporal bones comprise the dorso-temporal orbital rim.1 Trauma to the skull can result in fracture of orbital bones and subsequent ocular injury. Skull fractures in horses may result from trauma associated with direct kicks, collisions with stationary objects, and rearing in confined spaces.2,3 The dorsal orbital rim, especially the zygomatic process of the frontal bone and the zygomatic arch, are most prone to trauma due to their exposed location on the equine skull.1,4 Possi© 2014 American College of Veterinary Ophthalmologists
ble sequelae to frontal and zygomatic bone fractures include exposure of the frontal and caudal maxillary sinuses, respectively, and laceration of the vascular turbinate bones, resulting in epistaxis.4 Fractures to the lacrimal bone may traumatize the nasolacrimal duct resulting in impaired patency.5 Clinical signs associated with acute orbital fractures may include blepharospasm, epiphora, periorbital soft tissue swelling, bone instability, bone displacement/depression, crepitus, subcutaneous emphysema, epistaxis, globe rupture, enophthalmos, or exophthalmos.1,2,5–9 Horses with orbital fractures are at risk for both short and long term complications. In a small case series evaluating five horses with periorbital fractures, more than half involved ocular injury, ranging from corneal
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ulceration to exophthalmos.1 Potential complications of orbital fractures include facial/periorbital deformity, traumatic uveitis, corneal ulceration, corneal perforation/ globe rupture, hyphema, damage to intraocular structures, blindness, nasolacrimal duct occlusion, enophthalmos/exophthalmos, sequestrum formation, epistaxis, and sinusitis.1,4,10 Orbital fractures are diagnosed via digital palpation, skull radiographs, computed tomography (CT) or magnetic resonance imaging (MRI).10–12 Digital palpation has been reported more accurate than skull radiographs in diagnosing orbital fractures, however diagnostic imaging is indicated for complete evaluation of the bony orbit when a fracture is suspected.1,12 Due to the complexity of the equine skull and superimposition of large tissue masses, skull radiographs may be of limited assistance, and advanced imaging in the form of CT or MRI may be necessary to obtain a diagnosis.13–15 Advanced imaging techniques allow for three dimensional reconstruction, superior resolution, multi-planar views, and color enhancement of contrast material when administered.16–20 Treatment of orbital fractures includes medical management with or without surgical stabilization or reconstruction. Medical management, consisting of antiinflammatory therapy, is indicated for closed fractures where bony fragments are non-displaced and not impinging on ocular and adnexal structures, while antimicrobials are indicated in all horses with open fractures and fractures communicating with the sinuses. Chronic, closed fractures may not require medical therapy. Surgical reconstruction is indicated when orbital bones impinge on the globe, optic nerve, supraorbital nerve, or nasolacrimal duct, and to improve cosmesis.1,10 Surgical options include closed reduction, open exploration and reduction, and the use of internal fixation implants (bone plates, stainless steel wire, or polydioxanone suture).8,21–23 Open exploration and reduction are most appropriate in cases where fractures are severely comminuted, open, or more than 60 h old.1,8 Open reduction is indicated for fractures of the lacrimal bone, zygomatic process of the frontal bone or temporal bone, and zygomatic bone.8,10 In cases of sinus involvement, horses often require sinus trephination and lavage.1,8 Surgical management should be pursued prior to osseous callus formation, which may occur as early as 7–10 days post trauma.1,24 Systemic antimicrobial and anti-inflammatory therapy is warranted following surgical therapy, especially in cases of open exploration. However, despite published recommendations for the diagnosis and treatment of orbital fractures, to the authors’ knowledge, there are no studies evaluating factors that impact the prognosis in affected horses. The purpose of this study is to review the clinical features, treatments, complications, and long-term prognosis for horses presenting with orbital fractures.
MATERIALS AND METHODS
Criteria for selection of cases Medical records from the North Carolina State University Veterinary Health Complex were reviewed to identify horses with orbital fractures that were evaluated by the Equine Ophthalmology Service between May 2006 and August 2013. Inclusion criteria consisted of complete ophthalmic examination by a board-certified veterinary ophthalmologist, and orbital fractures confirmed by diagnostic imaging (skull radiographs or computed tomography) and reviewed by a board-certified veterinary radiologist. Procedures Information obtained from medical records included signalment, intended use for the horse, etiology of the traumatic injury, and previous, pertinent medical history. Lesion-specific information included the affected eye, time from injury to presentation, presenting clinical signs, ophthalmic examination findings, fracture location, imaging modality utilized, and diagnosis. The medical and surgical treatments performed and complications were also reviewed. The duration of time prior to referral was classified as acute (less than 48 h), sub-acute (between 48 and 168 h), or chronic (greater than 168 h). Horses were sedated with detomidine hydrochloride (0.01–0.015 mg/kg IV, Dormosedanâ; Pfizer Animal Health, Exton, PA, USA), and palpebral (1–2 mL, SQ, once) and frontal (1–2 mL, SQ, once) nerve blocks were performed with lidocaine (2%; Vedco Inc., St. Joseph, MO, USA) as previously described.20 Ophthalmic examination included digital palpation, slit-lamp biomicroscopy (Kowa SL-14; Kowa Company, Ltd., Tokyo, Japan) and indirect ophthalmoscopy (Heine EN 20-1; Heine Optotechnik, Herrsching, Germany or Keeler Vantage; Keeler Instruments Inc., Broomall, PA, USA) following pharmacologic mydriasis with tropicamide 1% solution USP (Bausch and Lomb Inc, Tampa, FL, USA). Topical application of fluorescein dye (Akorn Inc., Buffalo Grove, IL, USA) was performed and evaluated in all cases. Applanation tonometry (TonoPen XL; Mentor, Norwell, MA, USA) was performed in most horses. In cases where visualization of intraocular structures was not possible, transcorneal B-scan ultrasonography using a linear 12.5-mHz transducer (Universal Solutions, Inc., NY, USA) was performed to evaluate for posterior segment abnormalities. Complications associated with orbital fractures were divided into major and minor complications, and were further classified based on time until resolution of complication. Major complications were defined as any complication resulting in blindness, enucleation, or euthanasia. The remaining complications were defined as minor, and included: periorbital laceration, nasolacrimal duct occlusion, facial nerve paralysis, bone sequestrum formation, epistaxis, sinusitis, exophthalmos, enophthalmos, corneal
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ulceration, corneal degeneration, and anterior uveitis/ hyphema.
Imaging Diagnostic images were obtained by radiography or computed tomography. Fracture details included orbital bones involved, open versus closed, displaced versus nondisplaced, and nasal and sinus involvement. Skull radiographs were performed with an indirect capture digital radiography system. Radiographic projections consisted of erect right and left lateral views, right and left 30° lateral oblique views, and a dorsoventral view. Radiographs were obtained with the horse standing and sedated with detomidine hydrochloride (0.01–0.015 mg/kg IV, Dormosedanâ; Pfizer Animal Health). Computed tomography was performed under general anesthesia (see below) using a thirdgeneration helical CT scanner. Each equine head was scanned from the level of the nares to the most caudal aspect of the external occipital protuberance. A transverse multi-slice dataset was acquired and reconstructed into 1 and 3 mm transverse sequences, and dorsal and sagittal plane sequences were subsequently reconstructed. Iohexol (Omnipaque; GE Healthcare, Princeton, NJ, USA) was injected when indicated for contrast. Post-processing CT image reconstruction was performed using OSIRIX Imaging Software (version 3.6.1, http://www.osirixviewer.com). Images were reviewed on megapixel, monochrome, flat screen monitors by board-certified veterinary radiologists. Surgical procedures requiring general anesthesia were performed under the same anesthetic episode as the CT scan. Treatment Horses receiving medical therapy were routinely treated with topical neomycin/polymyxin B/gramicidin or neomycin/polymyxin B/bacitracin (q 6–8 h; Bausch & Lomb Pharmaceuticals, Inc., Tampa, FL, USA), and topical 1% atropine (q 12–24 h; Bausch & Lomb Pharmaceuticals, Inc.). Additionally, most patients received flunixin meglumine (1.0 mg/kg, PO, q12–24 h for 7–10 days, Banamineâ; Schering-Plough Animal Health, Union, NJ, USA) or phenylbutazone (1–2 g/454 kg, PO, q12–24 h for 7–10 days; Sparhawk Laboratories, Inc., Lanexa, KS, USA), as well as trimethoprim sulfadiazine (25 mg/kg, PO, q 12 h for 7–10 days; Qualitest Pharmaceuticals, Huntsville, AL, USA), enrofloxacin (7.5 mg/kg, PO q 24 h for 7–10 days; Baytrilâ; Bayer Corp, Shawnee Mission, KS, USA) and ranitidine (7 mg/kg, PO, q 8 h while on banamine; Anneal Pharmaceuticals, Glasgow, KY, USA) or omeprazole (0.55 mg/kg PO, q 24 h while on banamine, Gastrogardâ; Merial, Duluth, GA, USA), at the discretion of the attending veterinarian. Surgery was performed using standing sedation in stocks or in lateral recumbency under general anesthesia. When standing surgery was performed, sedation was achieved with detomidine hydrochloride (0.01–0.015 mg/ kg IV, Dormosedanâ; Pfizer Animal Health).
Prior to general anesthesia, horses were treated with flunixin meglumine (1.0 mg/kg, IV, Banamineâ; ScheringPlough Animal Health Corp., Omaha, NE, USA), gentamicin (6.6 mg/kg, IV; Sparhawk Laboratories, Inc.), and penicillin G potassium (22,000 IU/kg, IV, Pfizerpenâ; Roerig, Division of Pfizer, Inc., New York, NY, USA). General anesthesia was induced with xylazine (1 mg/kg IV, Xylajectâ; Akorn Inc.), ketamine (0.1 mg/kg IV, Vetaketâ; Lloyd, Shevandoah, IA, USA), and midazolam (2.5 mg/kg IV; Abraxis, Schaumburg, IL, USA). A surgical plane of anesthesia was maintained, after orotracheal intubation, with either ketamine (1 g IV, Vetaketâ; Lloyd), 5% guaifenesin (1 L IV; Butler, Columbus, OH, USA), and xylazine (500 mg IV, Xylajectâ; Akorn Inc.), utilized together as a constant rate infusion at 2.75 mL/kg/h, or with isoflurane vaporized in 100% oxygen. Horses were monitored by a board-certified veterinary anesthesiologist and received routine administration of intravenous fluids. Regardless of standing versus general anesthesia, palpebral (1–2 mL, SQ, once), frontal (1–2 mL, SQ, once), and retrobulbar (10 mL, once) nerve blocks were performed with lidocaine (2%; Vedco Inc.) as previously described, and topical proparacaine (1 mL, once; Akorn Pharmaceuticals, Lake Forest, IL, USA) was administered to the corneal surface.20
Follow-up Owners’ assessments of vision (normal, decreased, or absent), return to function (normal, decreased, or no return), cosmesis (great, satisfactory, or marginal), comfort (very comfortable, occasionally uncomfortable, uncomfortable the majority of the time), and presence of discharge (severe, moderate, mild, absent), were determined by completion of a questionnaire by owners over the phone or via email. Veterinarians’ assessments of vision were determined by evaluation of menace response, dazzle reflex, and direct/indirect pupillary light reflexes (PLRs), as obtained by phone conversations relaying the final examination findings. Outcome was further classified based on fracture healing, as determined by palpation and appearance, and retention of the globe. Descriptive statistics were used to compare the results in this study. Inferential statistical analysis to determine correlations between type of trauma, affected bones, clinical signs, complications, and outcomes were not performed due to the small sample size for all comparisons. RESULTS
Eighteen eyes of 18 horses (12 geldings [66.7%] and six mares [33.3%]) were unilaterally affected and met the inclusion criteria. Seven additional horses presenting with suspected orbital fractures were excluded from this study as diagnostic imaging was not performed. Affected horses included seven (38.9%) Quarter Horses, four (22.2%) Thoroughbreds, two (11.1%) Paints, two (11.1%) Fox
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Trotters, and one each (5.6%) of Warmblood, Irish Hunter, and Saddlebred. Age at time of presentation ranged from 7 months to 17 years (median 11.5 years). Twelve horses (66.7%) presented acutely (less than 48 h post-trauma), two horses (11.1%) presented sub-acutely (48–168 h post-trauma), and four horses (22.2%) presented with chronic fractures (>168 h post-trauma); these four horses presented at 3, 3.5 weeks, 3 months, and 1 year post-trauma. The causative incident was observed in twelve horses: 5/12 (41.7%) reared in a confined space in their stall or trailer; 4/12 (33.3%) sustained a kick to the head, and 3/12 (25.0%) collided with a stationary object while on pasture (one after colliding with a van, one after colliding with a jump, and one while cast on the ground). Orbital rim fractures/defects were palpable in ten horses (55.6%), and were isolated to the dorsal orbital rim in
eight horses (80%) and to the ventral orbital rim in two horses (20%). Fractures were classified as open in thirteen (72.2%) cases, and closed in five (27.8%) cases based on clinical appearance and digital palpation.
Imaging Skull and sinus radiography was performed in fifteen horses (83.3%), computed tomography was performed in two horses (11.1%), and a combination of radiography and CT was performed in one horse (5.6%). Computed tomography was recommended for all horses except those at high risk for general anesthesia. Magnetic resonance imaging (MRI) was performed in one horse presenting with neurologic signs. Ocular ultrasonography was required to evaluate the posterior segment in four horses (22.2%); imaging was normal in three cases and revealed a retinal detachment in one case (Figs 1–3).
(a)
(b)
Figure 1. (a) Two-year-old Thoroughbred gelding sustained a fracture of the right orbit (black arrow) shortly after colliding with a jump. Clinical signs included: blepharedema, ventral displacement and strabismus of the globe, conjunctival hyperemia/chemosis, anterior uveitis (fibrin), and a palpable dorsal orbital rim fracture. (b) Lateral skull and sinus radiograph revealing a medially and ventrally displaced depression fracture of the zygomatic process of the right frontal bone (white arrow).
(a)
(b)
Figure 2. Four-year-old Paint gelding diagnosed with an orbital fracture after rearing in the stall. Computed tomography transverse view (a) and three dimensional left dorsal oblique reconstruction (b) revealed a comminuted depression fracture of the left orbit (white arrow and black arrow, respectively), involving the zygomatic process of the left frontal, lacrimal, and zygomatic bones with multiple osseous fragments within the frontal sinus. The largest of these fragments was in close association with the globe causing mild exophthalmos, however the globe was intact with no evidence of penetration. © 2014 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 17, 97–106
equine orbital fractures: a review 101
Figure 3. One year post surgical repair of horse in Figure 2. The previous orbital fracture (arrow) healed well with only minimal scarring of the skin. The eye was visual and comfortable, with no discharge.
Most horses were diagnosed with open displaced (61.1%) or closed displaced (22.2%) orbital fractures (Table 1). Only three horses (16.7%) sustained non-displaced orbital fractures, and all three were presented for evaluation >168 h post-trauma. Horses with orbital fractures resulting from a direct kick exhibited a higher incidence of comminuted fractures (50.0%) as compared to other observed causative injuries (25.0%). Ten horses (55.6%) had fractures of the zygomatic process of their frontal bone, five horses (27.8%) had comminuted fractures affecting their zygomatic, frontal, and lacrimal bones, and three horses (16.7%) had fractures of the zygomatic process of their temporal bone. Seven horses (38.9%) had evidence of fluid/hemorrhage within their sinuses/nasal cavity and were diagnosed with sinusitis.
Complications Major and minor complications were classified based on ophthalmic examination and outcome (Table 2). Major complications (resulting in blindness, enucleation, or euthanasia) included globe rupture (1/18, 5.6%) and retinal detachment (1/18, 5.6%). Both of these eyes were enucleated, 48 h and 2 weeks, respectively, following trauma. The orbital fracture in the horse with concurrent retinal detachment was healing at the time of enucleation. This eye was enucleated per owner request due to blindness and reluctance to continue medical therapy. Two horses were euthanized for complications not directly related to the orbital fracture (one horse developed seizure-like activity and one horse sustained a palmar carpal fracture of the right radiocarpal bone during the initial trauma). Minor complications (not resulting in blindness, enucleation, or euthanasia) included blepharedema (17/18, 94.4%), periocular lacerations (11/18, 61.1%), conjunctival hyperemia/chemosis (10/18, 55.6%), corneal ulceration (7/ 18, 38.9%), and blepharospasm (7/18, 38.9%). Epistaxis was noted clinically in seven horses (38.9%). Periocular lacerations healed in all affected horses (11) within
10–14 days post trauma when closed primarily. Lacerations allowed to heal via secondary intention were healed 14–21 days post-trauma. Corneal ulcers, all treated with medical therapy, healed without complication in all horses (7) within 14 days of initial diagnosis. Epistaxis clinically resolved in all cases (7) within two days post trauma, and the five horses undergoing sinus trephination healed without complication in 12–18 days post procedure. Anterior uveitis resolved in two horses within 9 days post-trauma, and was present in two eyes at the time of enucleation. Enophthalmos and exophthalmos resolved in all horses within one month post trauma and treatment except in two cases, in which enophthalmos persisted long term. Facial nerve paralysis completely resolved within 3 weeks in two horses, and only partially resolved in one horse at 6 months. Horses that developed a wound infection or bone sequestrum underwent surgical debridement and medical therapy and were healed within 10–14 days.
Treatment Seventeen horses (94.4%) received treatment for their fractures. Two horses (11.1%) received medical therapy alone, and fifteen horses (83.3%) received a combination of surgery and medical therapy. One horse not requiring treatment presented to NCSU one-year post-orbital fracture with the complaint of periodic exophthalmos. Normal globe position was noted on ophthalmic examination, and skull and sinus radiographs revealed a healed closed, nondisplaced orbital fracture with sclerosis/periosteal reaction. Fifteen horses (83.3%) underwent surgical therapy with standing sedation (11/15, 73.3%), or general anesthesia (4/ 15, 26.7%). In all cases, surgery consisted of removal or repositioning of bone fragments utilizing digital retraction and bone hooks. Larger bone fragments were repositioned in 8/15 (53.3%) surgical cases, and smaller bony fragments were removed in 12/15 (80.0%) surgical cases. One horse required stabilization using 20-gauge stainless steel surgical wire following manual reduction of larger fragments. Five horses (33.3%) underwent concurrent sinus trephination, lavage, and drain placement. Two horses with evidence of sinusitis on imaging underwent surgical fracture repair without concurrent sinus trephination. Sinus trephination was recommended but declined in these horses. Of the seventeen horses receiving medical therapy, topical medications were not used as sole therapy in any case. Systemic medications were used as sole therapy in 5/17 horses (29.4%), and a combination of topical and systemic medications were administered in 12/17 horses (70.6%). Topical medical therapy consisted of an ophthalmic antibiotic (neomycin/polymyxin/gramicidin, neomycin/polymyxin/bacitracin) in 11/17 horses (64.7%), atropine in 9/ 17 horses (52.9%), and an ophthalmic lubricant in 2/17 horses (11.8%). Systemic medications consisted of an oral antibiotic (trimethoprim sulfadiazine or enrofloxacin) in 16 horses (94.1%; 14 received TMS and 2 received enrofloxacin), intravenous antibiotic (gentamicin and potassium
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Table 1. Orbital fractures and outcome categorized by inciting cause Signalment Rearing 4 y/o Paint gelding
Bones involved
Comminuted (zygomatic, frontal, lacrimal) Zygomatic process of frontal bone
17 y/o Irish Hunter gelding 11 y/o QH Zygomatic process mare of frontal bone 12 y/o Zygomatic process Saddlebred of temporal bone gelding* 12 y/o QH Zygomatic process mare†,‡ of frontal bone Collision with stationary object 13 y/o WB Zygomatic process gelding† of frontal bone 2 y/o TB Zygomatic process gelding of frontal bone 6 y/o QH Comminuted gelding (zygomatic, frontal, lacrimal) Direct kick 10 y/o QH Zygomatic process gelding of frontal bone 15 y/o TB Zygomatic process gelding of temporal bone 15 y/o Paint Comminuted gelding§ (zygomatic, frontal, lacrimal) 8 y/o TB Comminuted gelding (zygomatic, frontal, lacrimal) Unknown trauma 9 y/o TB Zygomatic process mare† of frontal bone 7 m/o QH Zygomatic process mare of frontal bone 15 y/o QH Zygomatic process gelding of frontal bone 15 y/o Fox Zygomatic process Trotter mare of frontal bone 17 y/o QH Comminuted gelding (zygomatic, frontal, lacrimal) 8 y/o Fox Zygomatic process Trotter mare of temporal bone *Refers †Refers ‡Refers §Refers
to to to to
Open or closed
Displacement
Time
Sinus involvement
Epistaxis
Vision
Return to function
Cosmesis
Open
Displaced
Acute
Yes
Yes
Normal
Yes
Satisfactory
Open
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
Yes
Yes
N/A
Euthanized
N/A
Open
Non-displaced
Chronic
No
No
N/A
Euthanized
N/A
Closed
Displaced
Chronic
No
No
Normal
Yes
Great
Closed
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
Yes
Yes
Normal
Yes
Satisfactory
Closed
Displaced
Sub-acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
Yes
Yes
Normal
Yes
Satisfactory
Open
Displaced
Acute
Yes
Yes
N/A
No
Enucleated
Closed
Displaced
Acute
Yes
Yes
Decreased
No
Marginal
Closed
Non-displaced
Chronic
No
No
Normal
Yes
Great
Open
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Sub-acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
Yes
Yes
N/A
Lost to follow-up
Enucleated
Open
Non-displaced
Chronic
No
No
Normal
Yes
Satisfactory
case euthanized due to palmar carpal fracture at time of initial trauma. cases not undergoing surgical therapy. case euthanized due to seizures. case euthanized due to lameness at a later date.
g penicillin) in 9 horses (52.9%; 7 received both gentamicin and potassium g, 1 each received gentamicin or potassium g), a non-steroidal anti-inflammatory (flunixin meglumine or phenylbutazone) in 17/17 horses (100%; 9 received flunixin meglumine and 8 received phenylbutazone), and a gastroprotectant (omeprazole or ranitidine) in 7/17 horses (41.2%; 6 received omeprazole and 1 received
ranitidine). A subpalpebral lavage system was placed in 3/17 horses (17.6%) to aid in administration of topical medications.
Follow-up/outcome Long-term follow-up included outcome, assessment of vision, return to function, and cosmesis, as outlined in
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equine orbital fractures: a review 103 Table 2. Ophthalmic examination findings and orbital fracture complications
Complication Blepharedema Periocular laceration Blepharospasm Orbital instability Absent menace response Absent dazzle reflex Facial nerve paralysis Strabismus Exophthalmos Globe rupture Conjunctival hyperemia/chemosis Corneal ulceration Uveitis (aqueous flare, fibrin, hyphema) Retinal detachment
Acute (n = 12)
Sub-acute (n = 2)
Chronic (n = 4)
Total (n = 18) (%)
12 9 6 6 2 2 2 2 0 1 8
2 1 1 2 0 0 1 0 0 0 2
3 1 0 2 1 1 0 0 1 0 0
17 11 7 10 3 3 3 2 1 1 10
4 2
2 1
1 1
7 (38.9) 4 (22.2)
1
0
0
1 (5.6)
(94.4) (78.6) (38.9) (55.6) (16.7) (16.7) (16.7) (11.1) (5.6) (5.6) (55.6)
Table 2. Orbital fractures completely healed in 15/18 cases (83.3%); 2/18 horses (11.1%) were euthanized for unrelated reasons; and 1/18 (5.6%) was lost to follow-up. The globe was intact in both horses that were euthanized; one was visual and one was non-visual at the time of euthanasia. The globe was retained in 16/18 cases (88.9%), while enucleation was performed in 2/18 cases (11.1%). Enucleation was performed secondary to globe rupture in one case, and secondary to blindness (retinal detachment) and owner’s request in the second case. The affected eye was deemed visual by a veterinarian at last follow-up in 14/18 horses (77.8%); follow-up ranged from 1 to 25 months, with a mean follow-up time of 4.2 months. The remaining cases included 2/18 (11.1%) blind at the time of enucleation, 1/18 (5.6%) visual at time of euthanasia, and 1/18 (5.6%) blind at time of euthanasia. The owner questionnaire was answered by fifteen owners; owners of the two euthanized horses were not questioned, and one horse was lost to follow-up following enucleation. Post-diagnosis follow-up time ranged from 3 months to 7.5 years (median 3.4 years). The questionnaire revealed that of the horses (88.9%) discharged from the hospital, 13/15 (86.7%) returned to previous function. One horse not returning to function developed ‘bucking’ behaviors following discharge, could no longer be ridden, and eventually was given away due to this new behavior. This same horse had decreased vision in the affected eye, to which the owner attributed this new behavior. The other horse not returning to function was one of the enucleated horses; this horse developed chronic lameness and was subsequently euthanized as a result. Owners’ perception of cosmesis was scored as ‘great’ in 9 horses (60%), ‘satisfactory’ in 4 horses (26.7%), and ‘marginal’ in 1 horse (6.7%). Enucleated horses were excluded from the cosmesis grading. All horses
diagnosed with fractures of the zygomatic process of the frontal bone were graded as having ‘great’ cosmesis, while fractures of the zygomatic process of the temporal bone or comminuted fractures affecting the zygomatic, frontal, and lacrimal bones, were graded as having ‘satisfactory’ or ‘marginal’ cosmesis, respectively. ‘Satisfactory’ and ‘marginal’ cosmesis was attributed to scarring in most cases, and mild enophthalmos in one case. Eyes were deemed ‘very comfortable’ in 14 horses. Ocular discharge on the affected side was reported in only one horse, and was graded as moderate. This horse obtained a comminuted fracture, affecting the zygomatic, frontal, and lacrimal bones, and nasolacrimal duct involvement/ occlusion was suspected based on the proximity to the fracture. DISCUSSION
In the present study, clinical abnormalities, treatments, complications, and long-term prognosis were evaluated for horses sustaining orbital fractures. The results suggest that the majority of horses treated for orbital fractures have a favorable outcome with appropriate healing, retained vision, and acceptable cosmesis. Radiography and computed tomography were effective in diagnosing orbital fractures and assessing sinus and nasal cavity involvement. Epistaxis and sinusitis were complications of comminuted fractures and warranted more aggressive therapy. The overall prognosis for equine orbital fractures may be associated with the type of injury as well as the type of orbital fracture sustained. Significant complications were encountered in a subset of horses sustaining orbital fractures, with major complications resulting in enucleation or euthanasia in four horses (22.2%). The incidence of major complications is higher than previously reported where enucleation and/or euthanasia were not performed in five horses with orbital fractures.1 In the present study, horses with orbital fractures resulting from a direct kick appeared to be at increased risk for ocular trauma, vision loss, and enucleation. Horses injured by a kick to the head had increased morbidity, as 50% sustained comminuted orbital fractures compared to 21.4% of all other horses in the study. A direct kick can transfer a force of more than 10,000 Newtons, of impact to any location of the equine skull and affect a large surface area.25–27 Horses with comminuted fractures from direct kicks also sustained ocular injury ranging from decreased vision with marginal cosmesis to loss of the globe. The incidence of corneal ulceration and sinus involvement was also higher, indicating more severe trauma from this type of high velocity/impact injury. Horses rearing in confined spaces typically sustained open, displaced fractures to the zygomatic process of the frontal bone. This type of fracture is consistent with previous reports and is attributed to the exposed, lateral location of the zygomatic process on the equine skull.1,4 All
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horses in this population sustained periorbital lacerations that healed without complication. Both horses that were euthanized in this study sustained trauma as a result of rearing in a confined space, indicating the potential for increased mortality associated with this type of injury. Horses in this group were not ultimately euthanized as a result of orbital fractures but due to concurrent injuries sustained during the initial trauma. Horses rearing in confined spaces may be prone to concurrent trauma to the poll, as well as fractures to the appendicular skeleton. Traumatic brain injury associated with rearing incidents, especially with trauma to the poll, can result in altered neurologic status.28 The optic nerve(s) of one or both eyes can also be stretched and damaged after impact to the head. In this optic nerve syndrome, vision and pupillary light responses are impaired or absent, and pupils are dilated immediately after the traumatic incident.28,29 The secondary phase of nerve injury continues for many hours after the initial trauma leading to progressively deteriorating vision with time; as a result, serial ophthalmic examinations are indicated following this type of trauma.29 Optic nerve atrophy has been associated with skull fractures.24 The pathogenesis for this form of optic nerve atrophy is poorly understood. Proposed mechanisms for vision loss include: shearing forces on the optic nerve at the optic foramen, displacement of the brain, direct contusion to the optic nerve, cerebral edema, interference with the vascular supply due to infarction, and subarachnoid hemorrhage.24,30–32 None of the horses in the present study were diagnosed with delayed onset vision loss or optic nerve atrophy. Regardless of trauma type, all horses sustaining comminuted orbital fractures and most horses with fractures to the zygomatic process of the temporal bone presented with epistaxis and sinusitis. Given the proximity of the frontal and lacrimal bones to the frontal and caudal maxillary sinuses, fractures to these bones are associated with an increased risk for sinus involvement. The presence of sinus hemorrhage often warrants surgical intervention to aid in hemostasis, maintain a patent airway, flush the sinuses, and decrease the risk of infection. During surgery, small bone fragments should be removed and a drain/catheter placed into the sinus to lavage blood clots and debris post-operatively.33 Given that epistaxis and sinusitis were seen most commonly in comminuted fractures or fractures to the zygomatic process of the temporal bone, epistaxis may be an indication of more severe trauma and a worse prognosis. None of the horses in the present study with fractures to the zygomatic process of the frontal bone developed epistaxis; these horses had a favorable functional and cosmetic outcome. Digital palpation can accurately diagnose orbital fractures, especially those isolated to the zygomatic process of the frontal bone.1 In the present study, seven of the ten horses (70%) diagnosed with orbital fractures based on palpation were localized to the zygomatic process of the
frontal bone. Localization of the fracture via palpation was then confirmed by diagnostic imaging in all horses. Three fractures to the zygomatic process of the frontal bone that went undiagnosed with digital palpation were a result of severe periorbital swelling. Although digital palpation can be useful during initial examination, diagnostic imaging is required to accurately identify and assess the extent of orbital fractures. Skull and sinus radiographs were performed as the sole imaging modality, in spite of potential limitations, in the majority of horses (15) in this study to diagnose orbital fractures and institute effective treatment. The utility of skull radiographs is limited by superimposition of bony structures that can prevent localization of bony fragments and impede diagnostic interpretation.11,34 However, skull radiographs can be performed with sedation and are particularly suited for horses at high risk for general anesthesia. Computed tomography was performed in three horses with comminuted orbital fractures affecting the zygomatic, frontal, and lacrimal bones. By eliminating superimposition artifact, CT provides better lesion localization and a more accurate determination of the extent of disease, which may not be readily apparent with other modalities.19,35 Computed tomography and MRI also allow for more accurate surgical planning for orbital fractures.34,35 The equine orbit contains a large amount of low density fat, which provides good contrast, allowing for differentiation of soft tissue orbital structures on CT. Computed tomography is advantageous over MRI in that it has a greater ability to detect osseous changes in the tissues of interest. However, MRI has better overall resolution of the retrobulbar tissues but may fail to detect defects in cortical bone or soft-tissue mineralization.36 One major disadvantage of both of these imaging modalities is that both require general anesthesia. In this study, CT provided invaluable surgical planning prior to orbital surgery. All horses diagnosed with displaced orbital fractures in the present study underwent surgical intervention. The three horses in this study that did not undergo a surgical procedure all sustained fractures to the zygomatic process of the frontal bone; all presented with chronic injury (3 weeks, 3 months, and 1 year post trauma). At the time of presentation, imaging confirmed non-displaced fractures in two cases, and a minimally displaced fracture in the third case; all fractures were healing or healed with callus formation, and warranted no surgical intervention. One of these cases was euthanized due to development of neurologic disease, and the two other cases reported only mild asymmetry compared to the unaffected side on the owner questionnaire. The delayed presentation of horses with non-displaced or minimally displaced fracture may be associated with less severe clinical signs observed by the owner immediately following traumatic injury. Though conservative (non-surgical) management of orbital and facial fractures can provide a functional outcome,
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reported complications include: chronic sinusitis, osseous sequestration, non-healing wounds, sinus or nasal fistulae, and facial deformity.37 The goals of orbital reconstruction are to restore the facial contour and symmetry, maximize airflow through the nasal passages, remove bone fragments that have minimal soft tissue attachment or are devoid of blood supply, and to minimize the risk of osseous sequestration and sinusitis.5 Many reports of orbital fractures healing without surgical intervention exist.1,3,6,9,38 However, surgery was recommended for the majority of horses in the present study due to the severity of depression and comminution of fractures, as well as the likelihood of poor functional and cosmetic outcomes without surgical intervention. Most skull fractures respond well to elevation of the depressed fragments, with or without stabilization with wires, and removal of small bony fragments.2,5,39,40 Internal fixation using bone plates may be necessary in severely comminuted fractures; however reports describing this approach are rare. The present study confirms that surgical therapy is effective in providing a favorable functional and cosmetic outcome in the majority of horses. Only one horse in the present study was reported to have decreased vision and marginal cosmesis following orbital surgery; this horse had sustained an extensive comminuted fracture of the zygomatic, frontal, and lacrimal bones. Limitations of the present study include those inherent to retrospective studies, such as incomplete medical records, lack of follow-up examinations, and reliance upon owner perception of outcome. Further limitations include variations in the imaging modalities utilized to assess fractures and non-standardized treatment protocols. Results of the present study suggest that the majority of horses diagnosed with orbital fractures have a favorable prognosis for vision, return to function, and overall cosmesis. Horses presenting with fractures due to direct kicks or with concurrent epistaxis may have a worse prognosis. Horses sustaining orbital fractures from rearing in confined spaces should be evaluated for concurrent injuries, such as neurologic abnormalities. Future studies evaluating orbital fractures, with sufficient numbers of horses to perform inferential statistics, are warranted. REFERENCES 1. Caron JP, Barber SM, Bailey JV et al. Periorbital skull fractures in five horses. Journal of the American Veterinary Medical Association 1986; 188: 280–284. 2. Beard W. The skull, maxilla and mandible. In: Equine Surgery, 2nd edn. (eds Auer JA, Stick JA) Saunders, Philadelphia, 1998; 887–899. 3. Turner AS. Surgical management of depression fractures of the equine skull. Veterinary Surgery 1979; 8: 29–33. 4. Gilger BC. Diseases and surgery of the globe and orbit. In: Equine Ophthalmology, 2nd edn. (ed. Gilger BC) Elsevier Science, St. Louis 2010; 93–132.
5. Ragle CA. Head trauma. Veterinary Clinics of North America: Equine Practice 1993; 9: 171–183. 6. Fessler JF, Adams SB. Repair of facial fractures. In: Atlas of Equine Surgery. (ed. Adams SB) Saunders, Philadelphia, 2000; 61–63. 7. Turner AS. Fractures of specific bones. In: Equine Medicine and Surgery, 3rd edn. (eds Mansmann RA, McAllister ES) American Veterinary Publications, Santa Barbara, 1982; 997–1001. 8. DeBowes RM. Fractures of the cranium. In: Equine Fracture Repair. (ed. Nixon AJ) Saunders, Philadelphia, 1996; 313–322. 9. Mudge MC, Bramlage LR. Field fracture management. Veterinary Clinics of North America: Equine Practice 2007; 23: 117–133. 10. Schaer BD. Ophthalmic emergencies in horses. Veterinary Clinics of North America: Equine Practice 2007; 23: 49–65. 11. Ramirez S, Tucker RL. Ophthalmic imaging. Veterinary Clinics of North America: Equine Practice 2004; 20: 441–457. 12. Butler J, Colles C, Dyson S et al. Clinical radiology of the horse. The Veterinary Journal 2009; 182: 362–363. 13. Johnston GR, Feeney DA. Radiology in ophthalmic diagnosis. Veterinary Clinics of North America: Small Animal Practice 1980; 10: 317–327. 14. Penninck D, Daniel GB, Brawer R et al. Veterinary ophthalmology. Clinical Techniques in Small Animal Practice 2001; 16: 22–39. 15. Kraft SL, Gavin PR. Physical principles and technical considerations for equine computed tomography and magnetic resonance imaging. Veterinary Clinics of North America: Equine Practice 2001; 17: 115–130. 16. Nykamp SG, Scrivani PV, Pease AP. Computed tomography dacryocystography evaluation of the nasolacrimal apparatus. Veterinary Radiology & Ultrasound 2004; 45: 23–28. 17. Dutton J, White J. Imaging and clinical evaluation of the lacrimal drainage system. In: The Lacrimal System. (ed. Cohen A, Mercandetti M, Brazzo B) Springer, New York, 2006; 87–95. 18. Puchalski S. Advances in equine computed tomography and use of contrast media. Veterinary Clinics of North America: Equine Practice 2012; 28: 563–581. 19. Lacombe VA, Sogaro-Robinson C, Reed SM. Diagnostic utility of computed tomography imaging in equine intracranial conditions. Equine Veterinary Journal 2010; 42: 393–399. 20. Gilger BC, Stoppini R. Equine ocular examination: routine and advanced diagnostic techniques. In: Equine Ophthalmology, 2nd edn. (ed. Gilger BC) Elsevier Science, St. Louis, 2010; 1–51. 21. Dowling BA, Dart AJ, Trope G. Surgical repair of skull fractures in four horses using cuttable bone plates. Australian Veterinary Journal 2001; 79: 324–327. 22. Schaaf KL, Kannegieter NJ, Lovell DK. Management of equine skull fractures using fixation with polydioxanone sutures. Australian Veterinary Journal 2008; 86: 481–485. 23. Tremaine H. Management of skull fractures in the horse. Equine Practice 2004; 26: 214–222. 24. Blogg JR, Stanley RG, Phillip CJ. Skull and orbital blow-out fractures in a horse. Equine Veterinary Journal 1990; 22: 5–7. 25. Exadaktylas AK, Eggli S, Inden P et al. Hoof kick injuries in unmounted equestrians: improving accident analysis and prevention by introducing an accident and emergency based relational database. Emergency Medicine Journal 2002; 19: 573– 575. 26. Leach DH. Biomechanics and the physiological costs of equine locomotion: a need for more research. Equine Veterinary Journal 1990; 9: 6–7. 27. Leach DH. A review of research on equine locomotion and biomechanics. Equine Veterinary Journal 1983; 15: 93–102.
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28. MacKay R. Brain injury after head trauma: pathophysiology, diagnosis, and treatment. Veterinary Clinics of North America: Equine Practice 2004; 20: 199–216. 29. Martin L, Kaswan R, Chapman W. Four cases of traumatic optic nerve blindness in the horse. Equine Veterinary Journal 1986; 18: 133–137. 30. Brooks DE, Wolf ED. Ocular trauma in the horse. Equine Veterinary Journal 1983; 2: 141–146. 31. Martin CL, Kaswan R, Chapman W. Traumatic nerve blindness in the horse. Annual Science Proceedings: American College of Veterinary Ophthalmologists. San Francisco, 1985; 238– 247. 32. Krohne SG, Janovitz E, Sojka J et al. Acute traumatic bilateral blindness in a horse. Annual Science Proceedings: American College of Veterinary Ophthalmologists. Las Vegas, 1988; 109–111. 33. Barakzai SZ. Epistaxis in the horse. Equine Veterinary Education 2004; 16: 207–217. 34. Plummer C. Exophthalmos in the horse. Equine Veterinary Education 2007; 19: 584–589.
35. Michau TM. Equine ocular examination: basic and advanced diagnostic techniques. In: Equine Ophthalmology, 1st edn. (ed. Gilger BC) Elsevier Science, St. Louis, 2005; 1–62. 36. Cutler TJ. Diseases and surgery of the globe and orbit. In: Equine Ophthalmology, 1st edn. (ed. Gilger BC) Elsevier Science, St. Louis, 2005; 63–106. 37. Miller SH, Lung RJ, Davis TS et al. Management of fractures of the supraorbital rim. Journal of Trauma: Injury, Infection, and Critical Care 1978; 18: 507–508. 38. McIlwraith CW, Robertson JT. Surgical repair of depression fractures of the skull. In: Mcllwraith & Turner’s Equine Surgery: Advanced Techniques, 2nd edn. Wiley, New York, 1998; 276–280. 39. Blackford JT, Blackford LW. Surgical treatment of selected musculoskeletal disorders of the head. In: Equine Surgery, 1st edn. (ed. Auer JA) Saunders, Philadelphia, 1992; 1075–1092. 40. Turner AS. Large animal orthopedics. In: The Practice of Large Animal Surgery (ed. Jenning PB) Saunders, Philadelphia, 1984; 893–894.
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DOI:10.1111/vop.12162
Equine orbital fractures: a review of 18 cases (2006–2013) Joseph C. Gerding, Alison Clode, Brian C. Gilger and Keith W. Montgomery Department of Clinical Sciences, North Carolina State University College of Veterinary Medicine, 1052 William Moore Drive, Raleigh, NC, 27607, United States
Address communications to: Keith W. Montgomery Tel.: 919-513-6659 Fax: 919-513-6711 e-mail: [email protected]
Objective To review the clinical features, treatments, complications, and outcomes of horses with traumatic orbital fractures. Study design Retrospective study. Sample Population Eighteen horses with confirmed orbital fractures. Procedures Medical records of horses presenting with orbital fractures between 2006 and 2013 were reviewed. Signalment, etiology of fracture, clinical signs, fracture descriptions, diagnostic imaging, treatments, complications, and outcomes were evaluated. Results Eighteen horses presented with orbital fractures resulting from rearing in a confined space (n = 5), being kicked (4), colliding with a stationary object (3), and unknown trauma (6). Radiography and computed tomography were effective at classifying fractures and evaluating sinus/nasal involvement. Epistaxis/sinusitis were associated with fractures of the zygomatic process of the temporal bone (n = 3) and comminuted fractures of multiple bones (5). Seventeen fractures required treatment, with fifteen receiving a combination of medical and surgical therapy. Surgery included reduction of large bony fragments (n = 8), removal of small fragments (12), stabilization with a wire implant (1), and sinus trephination and lavage (5). Factors contributing to a favorable outcome included: globe retention (n = 16), vision (14), comfort (15), cosmesis (9), and return to previous function (13). Conclusions Horses sustaining orbital fractures treated promptly with medical and surgical therapy have a favorable prognosis for return to function and cosmesis. Fractures affecting the zygomatic process of the frontal bone are unlikely to involve the sinus/nasal cavities. Epistaxis and sinusitis warrant more aggressive therapy and decrease functional and cosmetic outcome. Key Words: Complication, equine, fracture, orbital, outcome, retrospective
INTRODUCTION
The equine eye is protected by a complete, bony orbital rim formed by the frontal bone (dorsally), lacrimal bone (medially), zygomatic bone (ventrally), and temporal bone (laterally).1 The frontal process of the zygomatic bone and zygomatic processes of the frontal and temporal bones comprise the dorso-temporal orbital rim.1 Trauma to the skull can result in fracture of orbital bones and subsequent ocular injury. Skull fractures in horses may result from trauma associated with direct kicks, collisions with stationary objects, and rearing in confined spaces.2,3 The dorsal orbital rim, especially the zygomatic process of the frontal bone and the zygomatic arch, are most prone to trauma due to their exposed location on the equine skull.1,4 Possi© 2014 American College of Veterinary Ophthalmologists
ble sequelae to frontal and zygomatic bone fractures include exposure of the frontal and caudal maxillary sinuses, respectively, and laceration of the vascular turbinate bones, resulting in epistaxis.4 Fractures to the lacrimal bone may traumatize the nasolacrimal duct resulting in impaired patency.5 Clinical signs associated with acute orbital fractures may include blepharospasm, epiphora, periorbital soft tissue swelling, bone instability, bone displacement/depression, crepitus, subcutaneous emphysema, epistaxis, globe rupture, enophthalmos, or exophthalmos.1,2,5–9 Horses with orbital fractures are at risk for both short and long term complications. In a small case series evaluating five horses with periorbital fractures, more than half involved ocular injury, ranging from corneal
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ulceration to exophthalmos.1 Potential complications of orbital fractures include facial/periorbital deformity, traumatic uveitis, corneal ulceration, corneal perforation/ globe rupture, hyphema, damage to intraocular structures, blindness, nasolacrimal duct occlusion, enophthalmos/exophthalmos, sequestrum formation, epistaxis, and sinusitis.1,4,10 Orbital fractures are diagnosed via digital palpation, skull radiographs, computed tomography (CT) or magnetic resonance imaging (MRI).10–12 Digital palpation has been reported more accurate than skull radiographs in diagnosing orbital fractures, however diagnostic imaging is indicated for complete evaluation of the bony orbit when a fracture is suspected.1,12 Due to the complexity of the equine skull and superimposition of large tissue masses, skull radiographs may be of limited assistance, and advanced imaging in the form of CT or MRI may be necessary to obtain a diagnosis.13–15 Advanced imaging techniques allow for three dimensional reconstruction, superior resolution, multi-planar views, and color enhancement of contrast material when administered.16–20 Treatment of orbital fractures includes medical management with or without surgical stabilization or reconstruction. Medical management, consisting of antiinflammatory therapy, is indicated for closed fractures where bony fragments are non-displaced and not impinging on ocular and adnexal structures, while antimicrobials are indicated in all horses with open fractures and fractures communicating with the sinuses. Chronic, closed fractures may not require medical therapy. Surgical reconstruction is indicated when orbital bones impinge on the globe, optic nerve, supraorbital nerve, or nasolacrimal duct, and to improve cosmesis.1,10 Surgical options include closed reduction, open exploration and reduction, and the use of internal fixation implants (bone plates, stainless steel wire, or polydioxanone suture).8,21–23 Open exploration and reduction are most appropriate in cases where fractures are severely comminuted, open, or more than 60 h old.1,8 Open reduction is indicated for fractures of the lacrimal bone, zygomatic process of the frontal bone or temporal bone, and zygomatic bone.8,10 In cases of sinus involvement, horses often require sinus trephination and lavage.1,8 Surgical management should be pursued prior to osseous callus formation, which may occur as early as 7–10 days post trauma.1,24 Systemic antimicrobial and anti-inflammatory therapy is warranted following surgical therapy, especially in cases of open exploration. However, despite published recommendations for the diagnosis and treatment of orbital fractures, to the authors’ knowledge, there are no studies evaluating factors that impact the prognosis in affected horses. The purpose of this study is to review the clinical features, treatments, complications, and long-term prognosis for horses presenting with orbital fractures.
MATERIALS AND METHODS
Criteria for selection of cases Medical records from the North Carolina State University Veterinary Health Complex were reviewed to identify horses with orbital fractures that were evaluated by the Equine Ophthalmology Service between May 2006 and August 2013. Inclusion criteria consisted of complete ophthalmic examination by a board-certified veterinary ophthalmologist, and orbital fractures confirmed by diagnostic imaging (skull radiographs or computed tomography) and reviewed by a board-certified veterinary radiologist. Procedures Information obtained from medical records included signalment, intended use for the horse, etiology of the traumatic injury, and previous, pertinent medical history. Lesion-specific information included the affected eye, time from injury to presentation, presenting clinical signs, ophthalmic examination findings, fracture location, imaging modality utilized, and diagnosis. The medical and surgical treatments performed and complications were also reviewed. The duration of time prior to referral was classified as acute (less than 48 h), sub-acute (between 48 and 168 h), or chronic (greater than 168 h). Horses were sedated with detomidine hydrochloride (0.01–0.015 mg/kg IV, Dormosedanâ; Pfizer Animal Health, Exton, PA, USA), and palpebral (1–2 mL, SQ, once) and frontal (1–2 mL, SQ, once) nerve blocks were performed with lidocaine (2%; Vedco Inc., St. Joseph, MO, USA) as previously described.20 Ophthalmic examination included digital palpation, slit-lamp biomicroscopy (Kowa SL-14; Kowa Company, Ltd., Tokyo, Japan) and indirect ophthalmoscopy (Heine EN 20-1; Heine Optotechnik, Herrsching, Germany or Keeler Vantage; Keeler Instruments Inc., Broomall, PA, USA) following pharmacologic mydriasis with tropicamide 1% solution USP (Bausch and Lomb Inc, Tampa, FL, USA). Topical application of fluorescein dye (Akorn Inc., Buffalo Grove, IL, USA) was performed and evaluated in all cases. Applanation tonometry (TonoPen XL; Mentor, Norwell, MA, USA) was performed in most horses. In cases where visualization of intraocular structures was not possible, transcorneal B-scan ultrasonography using a linear 12.5-mHz transducer (Universal Solutions, Inc., NY, USA) was performed to evaluate for posterior segment abnormalities. Complications associated with orbital fractures were divided into major and minor complications, and were further classified based on time until resolution of complication. Major complications were defined as any complication resulting in blindness, enucleation, or euthanasia. The remaining complications were defined as minor, and included: periorbital laceration, nasolacrimal duct occlusion, facial nerve paralysis, bone sequestrum formation, epistaxis, sinusitis, exophthalmos, enophthalmos, corneal
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ulceration, corneal degeneration, and anterior uveitis/ hyphema.
Imaging Diagnostic images were obtained by radiography or computed tomography. Fracture details included orbital bones involved, open versus closed, displaced versus nondisplaced, and nasal and sinus involvement. Skull radiographs were performed with an indirect capture digital radiography system. Radiographic projections consisted of erect right and left lateral views, right and left 30° lateral oblique views, and a dorsoventral view. Radiographs were obtained with the horse standing and sedated with detomidine hydrochloride (0.01–0.015 mg/kg IV, Dormosedanâ; Pfizer Animal Health). Computed tomography was performed under general anesthesia (see below) using a thirdgeneration helical CT scanner. Each equine head was scanned from the level of the nares to the most caudal aspect of the external occipital protuberance. A transverse multi-slice dataset was acquired and reconstructed into 1 and 3 mm transverse sequences, and dorsal and sagittal plane sequences were subsequently reconstructed. Iohexol (Omnipaque; GE Healthcare, Princeton, NJ, USA) was injected when indicated for contrast. Post-processing CT image reconstruction was performed using OSIRIX Imaging Software (version 3.6.1, http://www.osirixviewer.com). Images were reviewed on megapixel, monochrome, flat screen monitors by board-certified veterinary radiologists. Surgical procedures requiring general anesthesia were performed under the same anesthetic episode as the CT scan. Treatment Horses receiving medical therapy were routinely treated with topical neomycin/polymyxin B/gramicidin or neomycin/polymyxin B/bacitracin (q 6–8 h; Bausch & Lomb Pharmaceuticals, Inc., Tampa, FL, USA), and topical 1% atropine (q 12–24 h; Bausch & Lomb Pharmaceuticals, Inc.). Additionally, most patients received flunixin meglumine (1.0 mg/kg, PO, q12–24 h for 7–10 days, Banamineâ; Schering-Plough Animal Health, Union, NJ, USA) or phenylbutazone (1–2 g/454 kg, PO, q12–24 h for 7–10 days; Sparhawk Laboratories, Inc., Lanexa, KS, USA), as well as trimethoprim sulfadiazine (25 mg/kg, PO, q 12 h for 7–10 days; Qualitest Pharmaceuticals, Huntsville, AL, USA), enrofloxacin (7.5 mg/kg, PO q 24 h for 7–10 days; Baytrilâ; Bayer Corp, Shawnee Mission, KS, USA) and ranitidine (7 mg/kg, PO, q 8 h while on banamine; Anneal Pharmaceuticals, Glasgow, KY, USA) or omeprazole (0.55 mg/kg PO, q 24 h while on banamine, Gastrogardâ; Merial, Duluth, GA, USA), at the discretion of the attending veterinarian. Surgery was performed using standing sedation in stocks or in lateral recumbency under general anesthesia. When standing surgery was performed, sedation was achieved with detomidine hydrochloride (0.01–0.015 mg/ kg IV, Dormosedanâ; Pfizer Animal Health).
Prior to general anesthesia, horses were treated with flunixin meglumine (1.0 mg/kg, IV, Banamineâ; ScheringPlough Animal Health Corp., Omaha, NE, USA), gentamicin (6.6 mg/kg, IV; Sparhawk Laboratories, Inc.), and penicillin G potassium (22,000 IU/kg, IV, Pfizerpenâ; Roerig, Division of Pfizer, Inc., New York, NY, USA). General anesthesia was induced with xylazine (1 mg/kg IV, Xylajectâ; Akorn Inc.), ketamine (0.1 mg/kg IV, Vetaketâ; Lloyd, Shevandoah, IA, USA), and midazolam (2.5 mg/kg IV; Abraxis, Schaumburg, IL, USA). A surgical plane of anesthesia was maintained, after orotracheal intubation, with either ketamine (1 g IV, Vetaketâ; Lloyd), 5% guaifenesin (1 L IV; Butler, Columbus, OH, USA), and xylazine (500 mg IV, Xylajectâ; Akorn Inc.), utilized together as a constant rate infusion at 2.75 mL/kg/h, or with isoflurane vaporized in 100% oxygen. Horses were monitored by a board-certified veterinary anesthesiologist and received routine administration of intravenous fluids. Regardless of standing versus general anesthesia, palpebral (1–2 mL, SQ, once), frontal (1–2 mL, SQ, once), and retrobulbar (10 mL, once) nerve blocks were performed with lidocaine (2%; Vedco Inc.) as previously described, and topical proparacaine (1 mL, once; Akorn Pharmaceuticals, Lake Forest, IL, USA) was administered to the corneal surface.20
Follow-up Owners’ assessments of vision (normal, decreased, or absent), return to function (normal, decreased, or no return), cosmesis (great, satisfactory, or marginal), comfort (very comfortable, occasionally uncomfortable, uncomfortable the majority of the time), and presence of discharge (severe, moderate, mild, absent), were determined by completion of a questionnaire by owners over the phone or via email. Veterinarians’ assessments of vision were determined by evaluation of menace response, dazzle reflex, and direct/indirect pupillary light reflexes (PLRs), as obtained by phone conversations relaying the final examination findings. Outcome was further classified based on fracture healing, as determined by palpation and appearance, and retention of the globe. Descriptive statistics were used to compare the results in this study. Inferential statistical analysis to determine correlations between type of trauma, affected bones, clinical signs, complications, and outcomes were not performed due to the small sample size for all comparisons. RESULTS
Eighteen eyes of 18 horses (12 geldings [66.7%] and six mares [33.3%]) were unilaterally affected and met the inclusion criteria. Seven additional horses presenting with suspected orbital fractures were excluded from this study as diagnostic imaging was not performed. Affected horses included seven (38.9%) Quarter Horses, four (22.2%) Thoroughbreds, two (11.1%) Paints, two (11.1%) Fox
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Trotters, and one each (5.6%) of Warmblood, Irish Hunter, and Saddlebred. Age at time of presentation ranged from 7 months to 17 years (median 11.5 years). Twelve horses (66.7%) presented acutely (less than 48 h post-trauma), two horses (11.1%) presented sub-acutely (48–168 h post-trauma), and four horses (22.2%) presented with chronic fractures (>168 h post-trauma); these four horses presented at 3, 3.5 weeks, 3 months, and 1 year post-trauma. The causative incident was observed in twelve horses: 5/12 (41.7%) reared in a confined space in their stall or trailer; 4/12 (33.3%) sustained a kick to the head, and 3/12 (25.0%) collided with a stationary object while on pasture (one after colliding with a van, one after colliding with a jump, and one while cast on the ground). Orbital rim fractures/defects were palpable in ten horses (55.6%), and were isolated to the dorsal orbital rim in
eight horses (80%) and to the ventral orbital rim in two horses (20%). Fractures were classified as open in thirteen (72.2%) cases, and closed in five (27.8%) cases based on clinical appearance and digital palpation.
Imaging Skull and sinus radiography was performed in fifteen horses (83.3%), computed tomography was performed in two horses (11.1%), and a combination of radiography and CT was performed in one horse (5.6%). Computed tomography was recommended for all horses except those at high risk for general anesthesia. Magnetic resonance imaging (MRI) was performed in one horse presenting with neurologic signs. Ocular ultrasonography was required to evaluate the posterior segment in four horses (22.2%); imaging was normal in three cases and revealed a retinal detachment in one case (Figs 1–3).
(a)
(b)
Figure 1. (a) Two-year-old Thoroughbred gelding sustained a fracture of the right orbit (black arrow) shortly after colliding with a jump. Clinical signs included: blepharedema, ventral displacement and strabismus of the globe, conjunctival hyperemia/chemosis, anterior uveitis (fibrin), and a palpable dorsal orbital rim fracture. (b) Lateral skull and sinus radiograph revealing a medially and ventrally displaced depression fracture of the zygomatic process of the right frontal bone (white arrow).
(a)
(b)
Figure 2. Four-year-old Paint gelding diagnosed with an orbital fracture after rearing in the stall. Computed tomography transverse view (a) and three dimensional left dorsal oblique reconstruction (b) revealed a comminuted depression fracture of the left orbit (white arrow and black arrow, respectively), involving the zygomatic process of the left frontal, lacrimal, and zygomatic bones with multiple osseous fragments within the frontal sinus. The largest of these fragments was in close association with the globe causing mild exophthalmos, however the globe was intact with no evidence of penetration. © 2014 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 17, 97–106
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Figure 3. One year post surgical repair of horse in Figure 2. The previous orbital fracture (arrow) healed well with only minimal scarring of the skin. The eye was visual and comfortable, with no discharge.
Most horses were diagnosed with open displaced (61.1%) or closed displaced (22.2%) orbital fractures (Table 1). Only three horses (16.7%) sustained non-displaced orbital fractures, and all three were presented for evaluation >168 h post-trauma. Horses with orbital fractures resulting from a direct kick exhibited a higher incidence of comminuted fractures (50.0%) as compared to other observed causative injuries (25.0%). Ten horses (55.6%) had fractures of the zygomatic process of their frontal bone, five horses (27.8%) had comminuted fractures affecting their zygomatic, frontal, and lacrimal bones, and three horses (16.7%) had fractures of the zygomatic process of their temporal bone. Seven horses (38.9%) had evidence of fluid/hemorrhage within their sinuses/nasal cavity and were diagnosed with sinusitis.
Complications Major and minor complications were classified based on ophthalmic examination and outcome (Table 2). Major complications (resulting in blindness, enucleation, or euthanasia) included globe rupture (1/18, 5.6%) and retinal detachment (1/18, 5.6%). Both of these eyes were enucleated, 48 h and 2 weeks, respectively, following trauma. The orbital fracture in the horse with concurrent retinal detachment was healing at the time of enucleation. This eye was enucleated per owner request due to blindness and reluctance to continue medical therapy. Two horses were euthanized for complications not directly related to the orbital fracture (one horse developed seizure-like activity and one horse sustained a palmar carpal fracture of the right radiocarpal bone during the initial trauma). Minor complications (not resulting in blindness, enucleation, or euthanasia) included blepharedema (17/18, 94.4%), periocular lacerations (11/18, 61.1%), conjunctival hyperemia/chemosis (10/18, 55.6%), corneal ulceration (7/ 18, 38.9%), and blepharospasm (7/18, 38.9%). Epistaxis was noted clinically in seven horses (38.9%). Periocular lacerations healed in all affected horses (11) within
10–14 days post trauma when closed primarily. Lacerations allowed to heal via secondary intention were healed 14–21 days post-trauma. Corneal ulcers, all treated with medical therapy, healed without complication in all horses (7) within 14 days of initial diagnosis. Epistaxis clinically resolved in all cases (7) within two days post trauma, and the five horses undergoing sinus trephination healed without complication in 12–18 days post procedure. Anterior uveitis resolved in two horses within 9 days post-trauma, and was present in two eyes at the time of enucleation. Enophthalmos and exophthalmos resolved in all horses within one month post trauma and treatment except in two cases, in which enophthalmos persisted long term. Facial nerve paralysis completely resolved within 3 weeks in two horses, and only partially resolved in one horse at 6 months. Horses that developed a wound infection or bone sequestrum underwent surgical debridement and medical therapy and were healed within 10–14 days.
Treatment Seventeen horses (94.4%) received treatment for their fractures. Two horses (11.1%) received medical therapy alone, and fifteen horses (83.3%) received a combination of surgery and medical therapy. One horse not requiring treatment presented to NCSU one-year post-orbital fracture with the complaint of periodic exophthalmos. Normal globe position was noted on ophthalmic examination, and skull and sinus radiographs revealed a healed closed, nondisplaced orbital fracture with sclerosis/periosteal reaction. Fifteen horses (83.3%) underwent surgical therapy with standing sedation (11/15, 73.3%), or general anesthesia (4/ 15, 26.7%). In all cases, surgery consisted of removal or repositioning of bone fragments utilizing digital retraction and bone hooks. Larger bone fragments were repositioned in 8/15 (53.3%) surgical cases, and smaller bony fragments were removed in 12/15 (80.0%) surgical cases. One horse required stabilization using 20-gauge stainless steel surgical wire following manual reduction of larger fragments. Five horses (33.3%) underwent concurrent sinus trephination, lavage, and drain placement. Two horses with evidence of sinusitis on imaging underwent surgical fracture repair without concurrent sinus trephination. Sinus trephination was recommended but declined in these horses. Of the seventeen horses receiving medical therapy, topical medications were not used as sole therapy in any case. Systemic medications were used as sole therapy in 5/17 horses (29.4%), and a combination of topical and systemic medications were administered in 12/17 horses (70.6%). Topical medical therapy consisted of an ophthalmic antibiotic (neomycin/polymyxin/gramicidin, neomycin/polymyxin/bacitracin) in 11/17 horses (64.7%), atropine in 9/ 17 horses (52.9%), and an ophthalmic lubricant in 2/17 horses (11.8%). Systemic medications consisted of an oral antibiotic (trimethoprim sulfadiazine or enrofloxacin) in 16 horses (94.1%; 14 received TMS and 2 received enrofloxacin), intravenous antibiotic (gentamicin and potassium
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Table 1. Orbital fractures and outcome categorized by inciting cause Signalment Rearing 4 y/o Paint gelding
Bones involved
Comminuted (zygomatic, frontal, lacrimal) Zygomatic process of frontal bone
17 y/o Irish Hunter gelding 11 y/o QH Zygomatic process mare of frontal bone 12 y/o Zygomatic process Saddlebred of temporal bone gelding* 12 y/o QH Zygomatic process mare†,‡ of frontal bone Collision with stationary object 13 y/o WB Zygomatic process gelding† of frontal bone 2 y/o TB Zygomatic process gelding of frontal bone 6 y/o QH Comminuted gelding (zygomatic, frontal, lacrimal) Direct kick 10 y/o QH Zygomatic process gelding of frontal bone 15 y/o TB Zygomatic process gelding of temporal bone 15 y/o Paint Comminuted gelding§ (zygomatic, frontal, lacrimal) 8 y/o TB Comminuted gelding (zygomatic, frontal, lacrimal) Unknown trauma 9 y/o TB Zygomatic process mare† of frontal bone 7 m/o QH Zygomatic process mare of frontal bone 15 y/o QH Zygomatic process gelding of frontal bone 15 y/o Fox Zygomatic process Trotter mare of frontal bone 17 y/o QH Comminuted gelding (zygomatic, frontal, lacrimal) 8 y/o Fox Zygomatic process Trotter mare of temporal bone *Refers †Refers ‡Refers §Refers
to to to to
Open or closed
Displacement
Time
Sinus involvement
Epistaxis
Vision
Return to function
Cosmesis
Open
Displaced
Acute
Yes
Yes
Normal
Yes
Satisfactory
Open
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
Yes
Yes
N/A
Euthanized
N/A
Open
Non-displaced
Chronic
No
No
N/A
Euthanized
N/A
Closed
Displaced
Chronic
No
No
Normal
Yes
Great
Closed
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
Yes
Yes
Normal
Yes
Satisfactory
Closed
Displaced
Sub-acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
Yes
Yes
Normal
Yes
Satisfactory
Open
Displaced
Acute
Yes
Yes
N/A
No
Enucleated
Closed
Displaced
Acute
Yes
Yes
Decreased
No
Marginal
Closed
Non-displaced
Chronic
No
No
Normal
Yes
Great
Open
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
No
No
Normal
Yes
Great
Open
Displaced
Sub-acute
No
No
Normal
Yes
Great
Open
Displaced
Acute
Yes
Yes
N/A
Lost to follow-up
Enucleated
Open
Non-displaced
Chronic
No
No
Normal
Yes
Satisfactory
case euthanized due to palmar carpal fracture at time of initial trauma. cases not undergoing surgical therapy. case euthanized due to seizures. case euthanized due to lameness at a later date.
g penicillin) in 9 horses (52.9%; 7 received both gentamicin and potassium g, 1 each received gentamicin or potassium g), a non-steroidal anti-inflammatory (flunixin meglumine or phenylbutazone) in 17/17 horses (100%; 9 received flunixin meglumine and 8 received phenylbutazone), and a gastroprotectant (omeprazole or ranitidine) in 7/17 horses (41.2%; 6 received omeprazole and 1 received
ranitidine). A subpalpebral lavage system was placed in 3/17 horses (17.6%) to aid in administration of topical medications.
Follow-up/outcome Long-term follow-up included outcome, assessment of vision, return to function, and cosmesis, as outlined in
© 2014 American College of Veterinary Ophthalmologists, Veterinary Ophthalmology, 17, 97–106
equine orbital fractures: a review 103 Table 2. Ophthalmic examination findings and orbital fracture complications
Complication Blepharedema Periocular laceration Blepharospasm Orbital instability Absent menace response Absent dazzle reflex Facial nerve paralysis Strabismus Exophthalmos Globe rupture Conjunctival hyperemia/chemosis Corneal ulceration Uveitis (aqueous flare, fibrin, hyphema) Retinal detachment
Acute (n = 12)
Sub-acute (n = 2)
Chronic (n = 4)
Total (n = 18) (%)
12 9 6 6 2 2 2 2 0 1 8
2 1 1 2 0 0 1 0 0 0 2
3 1 0 2 1 1 0 0 1 0 0
17 11 7 10 3 3 3 2 1 1 10
4 2
2 1
1 1
7 (38.9) 4 (22.2)
1
0
0
1 (5.6)
(94.4) (78.6) (38.9) (55.6) (16.7) (16.7) (16.7) (11.1) (5.6) (5.6) (55.6)
Table 2. Orbital fractures completely healed in 15/18 cases (83.3%); 2/18 horses (11.1%) were euthanized for unrelated reasons; and 1/18 (5.6%) was lost to follow-up. The globe was intact in both horses that were euthanized; one was visual and one was non-visual at the time of euthanasia. The globe was retained in 16/18 cases (88.9%), while enucleation was performed in 2/18 cases (11.1%). Enucleation was performed secondary to globe rupture in one case, and secondary to blindness (retinal detachment) and owner’s request in the second case. The affected eye was deemed visual by a veterinarian at last follow-up in 14/18 horses (77.8%); follow-up ranged from 1 to 25 months, with a mean follow-up time of 4.2 months. The remaining cases included 2/18 (11.1%) blind at the time of enucleation, 1/18 (5.6%) visual at time of euthanasia, and 1/18 (5.6%) blind at time of euthanasia. The owner questionnaire was answered by fifteen owners; owners of the two euthanized horses were not questioned, and one horse was lost to follow-up following enucleation. Post-diagnosis follow-up time ranged from 3 months to 7.5 years (median 3.4 years). The questionnaire revealed that of the horses (88.9%) discharged from the hospital, 13/15 (86.7%) returned to previous function. One horse not returning to function developed ‘bucking’ behaviors following discharge, could no longer be ridden, and eventually was given away due to this new behavior. This same horse had decreased vision in the affected eye, to which the owner attributed this new behavior. The other horse not returning to function was one of the enucleated horses; this horse developed chronic lameness and was subsequently euthanized as a result. Owners’ perception of cosmesis was scored as ‘great’ in 9 horses (60%), ‘satisfactory’ in 4 horses (26.7%), and ‘marginal’ in 1 horse (6.7%). Enucleated horses were excluded from the cosmesis grading. All horses
diagnosed with fractures of the zygomatic process of the frontal bone were graded as having ‘great’ cosmesis, while fractures of the zygomatic process of the temporal bone or comminuted fractures affecting the zygomatic, frontal, and lacrimal bones, were graded as having ‘satisfactory’ or ‘marginal’ cosmesis, respectively. ‘Satisfactory’ and ‘marginal’ cosmesis was attributed to scarring in most cases, and mild enophthalmos in one case. Eyes were deemed ‘very comfortable’ in 14 horses. Ocular discharge on the affected side was reported in only one horse, and was graded as moderate. This horse obtained a comminuted fracture, affecting the zygomatic, frontal, and lacrimal bones, and nasolacrimal duct involvement/ occlusion was suspected based on the proximity to the fracture. DISCUSSION
In the present study, clinical abnormalities, treatments, complications, and long-term prognosis were evaluated for horses sustaining orbital fractures. The results suggest that the majority of horses treated for orbital fractures have a favorable outcome with appropriate healing, retained vision, and acceptable cosmesis. Radiography and computed tomography were effective in diagnosing orbital fractures and assessing sinus and nasal cavity involvement. Epistaxis and sinusitis were complications of comminuted fractures and warranted more aggressive therapy. The overall prognosis for equine orbital fractures may be associated with the type of injury as well as the type of orbital fracture sustained. Significant complications were encountered in a subset of horses sustaining orbital fractures, with major complications resulting in enucleation or euthanasia in four horses (22.2%). The incidence of major complications is higher than previously reported where enucleation and/or euthanasia were not performed in five horses with orbital fractures.1 In the present study, horses with orbital fractures resulting from a direct kick appeared to be at increased risk for ocular trauma, vision loss, and enucleation. Horses injured by a kick to the head had increased morbidity, as 50% sustained comminuted orbital fractures compared to 21.4% of all other horses in the study. A direct kick can transfer a force of more than 10,000 Newtons, of impact to any location of the equine skull and affect a large surface area.25–27 Horses with comminuted fractures from direct kicks also sustained ocular injury ranging from decreased vision with marginal cosmesis to loss of the globe. The incidence of corneal ulceration and sinus involvement was also higher, indicating more severe trauma from this type of high velocity/impact injury. Horses rearing in confined spaces typically sustained open, displaced fractures to the zygomatic process of the frontal bone. This type of fracture is consistent with previous reports and is attributed to the exposed, lateral location of the zygomatic process on the equine skull.1,4 All
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horses in this population sustained periorbital lacerations that healed without complication. Both horses that were euthanized in this study sustained trauma as a result of rearing in a confined space, indicating the potential for increased mortality associated with this type of injury. Horses in this group were not ultimately euthanized as a result of orbital fractures but due to concurrent injuries sustained during the initial trauma. Horses rearing in confined spaces may be prone to concurrent trauma to the poll, as well as fractures to the appendicular skeleton. Traumatic brain injury associated with rearing incidents, especially with trauma to the poll, can result in altered neurologic status.28 The optic nerve(s) of one or both eyes can also be stretched and damaged after impact to the head. In this optic nerve syndrome, vision and pupillary light responses are impaired or absent, and pupils are dilated immediately after the traumatic incident.28,29 The secondary phase of nerve injury continues for many hours after the initial trauma leading to progressively deteriorating vision with time; as a result, serial ophthalmic examinations are indicated following this type of trauma.29 Optic nerve atrophy has been associated with skull fractures.24 The pathogenesis for this form of optic nerve atrophy is poorly understood. Proposed mechanisms for vision loss include: shearing forces on the optic nerve at the optic foramen, displacement of the brain, direct contusion to the optic nerve, cerebral edema, interference with the vascular supply due to infarction, and subarachnoid hemorrhage.24,30–32 None of the horses in the present study were diagnosed with delayed onset vision loss or optic nerve atrophy. Regardless of trauma type, all horses sustaining comminuted orbital fractures and most horses with fractures to the zygomatic process of the temporal bone presented with epistaxis and sinusitis. Given the proximity of the frontal and lacrimal bones to the frontal and caudal maxillary sinuses, fractures to these bones are associated with an increased risk for sinus involvement. The presence of sinus hemorrhage often warrants surgical intervention to aid in hemostasis, maintain a patent airway, flush the sinuses, and decrease the risk of infection. During surgery, small bone fragments should be removed and a drain/catheter placed into the sinus to lavage blood clots and debris post-operatively.33 Given that epistaxis and sinusitis were seen most commonly in comminuted fractures or fractures to the zygomatic process of the temporal bone, epistaxis may be an indication of more severe trauma and a worse prognosis. None of the horses in the present study with fractures to the zygomatic process of the frontal bone developed epistaxis; these horses had a favorable functional and cosmetic outcome. Digital palpation can accurately diagnose orbital fractures, especially those isolated to the zygomatic process of the frontal bone.1 In the present study, seven of the ten horses (70%) diagnosed with orbital fractures based on palpation were localized to the zygomatic process of the
frontal bone. Localization of the fracture via palpation was then confirmed by diagnostic imaging in all horses. Three fractures to the zygomatic process of the frontal bone that went undiagnosed with digital palpation were a result of severe periorbital swelling. Although digital palpation can be useful during initial examination, diagnostic imaging is required to accurately identify and assess the extent of orbital fractures. Skull and sinus radiographs were performed as the sole imaging modality, in spite of potential limitations, in the majority of horses (15) in this study to diagnose orbital fractures and institute effective treatment. The utility of skull radiographs is limited by superimposition of bony structures that can prevent localization of bony fragments and impede diagnostic interpretation.11,34 However, skull radiographs can be performed with sedation and are particularly suited for horses at high risk for general anesthesia. Computed tomography was performed in three horses with comminuted orbital fractures affecting the zygomatic, frontal, and lacrimal bones. By eliminating superimposition artifact, CT provides better lesion localization and a more accurate determination of the extent of disease, which may not be readily apparent with other modalities.19,35 Computed tomography and MRI also allow for more accurate surgical planning for orbital fractures.34,35 The equine orbit contains a large amount of low density fat, which provides good contrast, allowing for differentiation of soft tissue orbital structures on CT. Computed tomography is advantageous over MRI in that it has a greater ability to detect osseous changes in the tissues of interest. However, MRI has better overall resolution of the retrobulbar tissues but may fail to detect defects in cortical bone or soft-tissue mineralization.36 One major disadvantage of both of these imaging modalities is that both require general anesthesia. In this study, CT provided invaluable surgical planning prior to orbital surgery. All horses diagnosed with displaced orbital fractures in the present study underwent surgical intervention. The three horses in this study that did not undergo a surgical procedure all sustained fractures to the zygomatic process of the frontal bone; all presented with chronic injury (3 weeks, 3 months, and 1 year post trauma). At the time of presentation, imaging confirmed non-displaced fractures in two cases, and a minimally displaced fracture in the third case; all fractures were healing or healed with callus formation, and warranted no surgical intervention. One of these cases was euthanized due to development of neurologic disease, and the two other cases reported only mild asymmetry compared to the unaffected side on the owner questionnaire. The delayed presentation of horses with non-displaced or minimally displaced fracture may be associated with less severe clinical signs observed by the owner immediately following traumatic injury. Though conservative (non-surgical) management of orbital and facial fractures can provide a functional outcome,
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equine orbital fractures: a review 105
reported complications include: chronic sinusitis, osseous sequestration, non-healing wounds, sinus or nasal fistulae, and facial deformity.37 The goals of orbital reconstruction are to restore the facial contour and symmetry, maximize airflow through the nasal passages, remove bone fragments that have minimal soft tissue attachment or are devoid of blood supply, and to minimize the risk of osseous sequestration and sinusitis.5 Many reports of orbital fractures healing without surgical intervention exist.1,3,6,9,38 However, surgery was recommended for the majority of horses in the present study due to the severity of depression and comminution of fractures, as well as the likelihood of poor functional and cosmetic outcomes without surgical intervention. Most skull fractures respond well to elevation of the depressed fragments, with or without stabilization with wires, and removal of small bony fragments.2,5,39,40 Internal fixation using bone plates may be necessary in severely comminuted fractures; however reports describing this approach are rare. The present study confirms that surgical therapy is effective in providing a favorable functional and cosmetic outcome in the majority of horses. Only one horse in the present study was reported to have decreased vision and marginal cosmesis following orbital surgery; this horse had sustained an extensive comminuted fracture of the zygomatic, frontal, and lacrimal bones. Limitations of the present study include those inherent to retrospective studies, such as incomplete medical records, lack of follow-up examinations, and reliance upon owner perception of outcome. Further limitations include variations in the imaging modalities utilized to assess fractures and non-standardized treatment protocols. Results of the present study suggest that the majority of horses diagnosed with orbital fractures have a favorable prognosis for vision, return to function, and overall cosmesis. Horses presenting with fractures due to direct kicks or with concurrent epistaxis may have a worse prognosis. Horses sustaining orbital fractures from rearing in confined spaces should be evaluated for concurrent injuries, such as neurologic abnormalities. Future studies evaluating orbital fractures, with sufficient numbers of horses to perform inferential statistics, are warranted. REFERENCES 1. Caron JP, Barber SM, Bailey JV et al. Periorbital skull fractures in five horses. Journal of the American Veterinary Medical Association 1986; 188: 280–284. 2. Beard W. The skull, maxilla and mandible. In: Equine Surgery, 2nd edn. (eds Auer JA, Stick JA) Saunders, Philadelphia, 1998; 887–899. 3. Turner AS. Surgical management of depression fractures of the equine skull. Veterinary Surgery 1979; 8: 29–33. 4. Gilger BC. Diseases and surgery of the globe and orbit. In: Equine Ophthalmology, 2nd edn. (ed. Gilger BC) Elsevier Science, St. Louis 2010; 93–132.
5. Ragle CA. Head trauma. Veterinary Clinics of North America: Equine Practice 1993; 9: 171–183. 6. Fessler JF, Adams SB. Repair of facial fractures. In: Atlas of Equine Surgery. (ed. Adams SB) Saunders, Philadelphia, 2000; 61–63. 7. Turner AS. Fractures of specific bones. In: Equine Medicine and Surgery, 3rd edn. (eds Mansmann RA, McAllister ES) American Veterinary Publications, Santa Barbara, 1982; 997–1001. 8. DeBowes RM. Fractures of the cranium. In: Equine Fracture Repair. (ed. Nixon AJ) Saunders, Philadelphia, 1996; 313–322. 9. Mudge MC, Bramlage LR. Field fracture management. Veterinary Clinics of North America: Equine Practice 2007; 23: 117–133. 10. Schaer BD. Ophthalmic emergencies in horses. Veterinary Clinics of North America: Equine Practice 2007; 23: 49–65. 11. Ramirez S, Tucker RL. Ophthalmic imaging. Veterinary Clinics of North America: Equine Practice 2004; 20: 441–457. 12. Butler J, Colles C, Dyson S et al. Clinical radiology of the horse. The Veterinary Journal 2009; 182: 362–363. 13. Johnston GR, Feeney DA. Radiology in ophthalmic diagnosis. Veterinary Clinics of North America: Small Animal Practice 1980; 10: 317–327. 14. Penninck D, Daniel GB, Brawer R et al. Veterinary ophthalmology. Clinical Techniques in Small Animal Practice 2001; 16: 22–39. 15. Kraft SL, Gavin PR. Physical principles and technical considerations for equine computed tomography and magnetic resonance imaging. Veterinary Clinics of North America: Equine Practice 2001; 17: 115–130. 16. Nykamp SG, Scrivani PV, Pease AP. Computed tomography dacryocystography evaluation of the nasolacrimal apparatus. Veterinary Radiology & Ultrasound 2004; 45: 23–28. 17. Dutton J, White J. Imaging and clinical evaluation of the lacrimal drainage system. In: The Lacrimal System. (ed. Cohen A, Mercandetti M, Brazzo B) Springer, New York, 2006; 87–95. 18. Puchalski S. Advances in equine computed tomography and use of contrast media. Veterinary Clinics of North America: Equine Practice 2012; 28: 563–581. 19. Lacombe VA, Sogaro-Robinson C, Reed SM. Diagnostic utility of computed tomography imaging in equine intracranial conditions. Equine Veterinary Journal 2010; 42: 393–399. 20. Gilger BC, Stoppini R. Equine ocular examination: routine and advanced diagnostic techniques. In: Equine Ophthalmology, 2nd edn. (ed. Gilger BC) Elsevier Science, St. Louis, 2010; 1–51. 21. Dowling BA, Dart AJ, Trope G. Surgical repair of skull fractures in four horses using cuttable bone plates. Australian Veterinary Journal 2001; 79: 324–327. 22. Schaaf KL, Kannegieter NJ, Lovell DK. Management of equine skull fractures using fixation with polydioxanone sutures. Australian Veterinary Journal 2008; 86: 481–485. 23. Tremaine H. Management of skull fractures in the horse. Equine Practice 2004; 26: 214–222. 24. Blogg JR, Stanley RG, Phillip CJ. Skull and orbital blow-out fractures in a horse. Equine Veterinary Journal 1990; 22: 5–7. 25. Exadaktylas AK, Eggli S, Inden P et al. Hoof kick injuries in unmounted equestrians: improving accident analysis and prevention by introducing an accident and emergency based relational database. Emergency Medicine Journal 2002; 19: 573– 575. 26. Leach DH. Biomechanics and the physiological costs of equine locomotion: a need for more research. Equine Veterinary Journal 1990; 9: 6–7. 27. Leach DH. A review of research on equine locomotion and biomechanics. Equine Veterinary Journal 1983; 15: 93–102.
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