History and Physical Examination Findings
A 9-year-old 590-kg (1,298-lb) Thoroughbred gelding was evaluated because of difficulty eating for approximately 1 hour's duration. Physical examination revealed heart rate, respiratory rate, and body temperature within the respective reference ranges, with no abnormalities on cranial nerve evaluation. Findings on visual and physical examination of the head and neck were unremarkable, except that palpation of the left temporomandibular joint (TMJ) and left masseter muscle elicited signs of pain. The patient was able to prehend a small amount of offered hay but appeared hesitant to masticate and swallow. Sedation (xylazine, 0.25 mg/kg [0.1 mg/lb], IV) was provided, and the oral cavity was rinsed and examined; no speculum was used because of concerns over a possible mandibular fracture. No additional abnormalities were observed. Radiographic examination was advised; the owner declined further diagnostic testing that evening. The horse was treated with flunixin meglumine (1.1 mg/kg [0.5 mg/lb], IV), and the owner was instructed to administer phenylbutazone (2.2 mg/kg [1.0 mg/lb], PO, q 12 h) and feed only pelleted grain soaked in water until the patient was reexamined. The next day, the horse was able to eat a small amount of hay with minimal difficulty. The decision was made to allow grazing, provide soaked pelleted grain, and continue phenylbutazone treatment for 5 days.
On recheck examination 2 weeks later, no chewing abnormalities were observed, and signs of pain on TMJ palpation were minimal. A slight clicking sound was detected that seemed to originate from the left TMJ. Six weeks after the initial incident, abnormal behavior was observed when the horse consumed pelleted grain; a video recording showed repeated lateral excursions of the mandibles to the right, neck stretching, head turning, and tongue rolling. The owner resumed wetting the feed, administered flunixin meglumine orally at the previous dosage, and reported that the horse appeared normal the following morning. The behavior recurred several times over the next few weeks, and further diagnostic evaluation was requested.
Reexamination revealed no signs of pain on palpation of the TMJ region. The horse was sedated with detomidine (0.01 mg/kg [0.0045 mg/lb], IV); oral examination with a full-mouth speculum, mirror, and headlamp revealed no apparent abnormalities. Dorsoventral, laterolateral, and right 15° caudal 70° dorsal–left ventral oblique1 radiographs were obtained. Selected radiographic views are provided (Figure 1).
Tangential right 15° caudal 70° dorsal–left ventral oblique (A) and laterolateral (B) radiographic views of the left temporomandibular joint (TMJ) of a 9-year-old Thoroughbred gelding with intermittent signs of dysmastication. In panel A, the bottom of the image is the rostral direction.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Tangential right 15° caudal 70° dorsal–left ventral oblique (A) and laterolateral (B) radiographic views of the left temporomandibular joint (TMJ) of a 9-year-old Thoroughbred gelding with intermittent signs of dysmastication. In panel A, the bottom of the image is the rostral direction.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Tangential right 15° caudal 70° dorsal–left ventral oblique (A) and laterolateral (B) radiographic views of the left temporomandibular joint (TMJ) of a 9-year-old Thoroughbred gelding with intermittent signs of dysmastication. In panel A, the bottom of the image is the rostral direction.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Determine whether additional studies are required, or make your diagnosis, then turn the page→
Diagnostic Imaging Findings and Interpretation
The right 15° caudal 70° dorsal–left ventral oblique projection proved to be the best radiographic view for identification of an articular fracture of the lateral aspect of the condylar process of the left mandible (Figure 2). There were multiple oblique lucent lines extending from the articular margin to the ventral and ventrolateral aspects of the condylar process of the mandible, consistent with a nondisplaced, comminuted fracture. This fracture configuration resulted in a triangular fragment along the articular margin. A smaller, rounded articular fracture fragment was present medial to the larger fragment, with mild irregular bone production along the lateral aspect of the condylar process at the margins of the lucent lines. This finding was most consistent with callus formation or a periosteal reaction. The periarticular margins were slightly flared, consistent with a small osteophyte.
Same radiographic images as in Figure 1. A—The left condylar process (single arrow) and the articular tubercle of the temporal bone (double arrows) comprising the TMJ can be easily seen, and a fracture of the condylar process is evident in this view. The coronoid process of the mandible (pound sign) and the base of the pinna (asterisk) are also indicated. B—The condylar process (thin arrow) and articular tubercle of the temporal bone (thick arrow) are seen in this view; however, there is superimposition of the rest of the skull. The caret indicates the external meatus of the ear.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Same radiographic images as in Figure 1. A—The left condylar process (single arrow) and the articular tubercle of the temporal bone (double arrows) comprising the TMJ can be easily seen, and a fracture of the condylar process is evident in this view. The coronoid process of the mandible (pound sign) and the base of the pinna (asterisk) are also indicated. B—The condylar process (thin arrow) and articular tubercle of the temporal bone (thick arrow) are seen in this view; however, there is superimposition of the rest of the skull. The caret indicates the external meatus of the ear.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Same radiographic images as in Figure 1. A—The left condylar process (single arrow) and the articular tubercle of the temporal bone (double arrows) comprising the TMJ can be easily seen, and a fracture of the condylar process is evident in this view. The coronoid process of the mandible (pound sign) and the base of the pinna (asterisk) are also indicated. B—The condylar process (thin arrow) and articular tubercle of the temporal bone (thick arrow) are seen in this view; however, there is superimposition of the rest of the skull. The caret indicates the external meatus of the ear.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Treatment and Outcome
Dietary management was initiated prior to obtaining a definitive diagnosis and consisted of feeding a slurry of pelleted feed while continuing to allow access to grass pasture. After discussion of the radiographic findings, additional diagnostic imaging (ultrasonography and CT) and exploratory arthroscopy with possible removal of the fractured portion of the condylar process were discussed with the owner. However, because the horse had continued to improve, with fewer incidents of the observed abnormal jaw and head movements over time while eating, the owner elected conservative treatment. After the previously described approximate 6-week period of intermittent signs of dysmastication, no further episodes were observed and the horse's normal diet of hay and pelleted feed was reinstituted.
Follow-up radiographs of the left TMJ were performed 1 and 5 months after the initial radiographs were obtained; comparison with the contralateral TMJ (left 15° caudal 70° dorsal–right ventral oblique view) is shown (Figure 3). These images revealed no progression of the periosteal bone production along the lateral fracture lines. Mild progressive rounding of the fracture margins was evident at the 5-month time point; otherwise, the comminuted fracture appeared unchanged. The small osteophyte at the lateral periarticular margin also remained static.
Side-by-side comparison of the left and right TMJs of the same horse as in Figure 1 (right 15° caudal 70° dorsal–left ventral oblique and left 15° caudal 70° dorsal–right ventral oblique projections, respectively). A—The left TMJ 5 months after the original injury. B—The normal right TMJ. There is minimal change in the appearance of the fracture at the 5-month recheck.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Side-by-side comparison of the left and right TMJs of the same horse as in Figure 1 (right 15° caudal 70° dorsal–left ventral oblique and left 15° caudal 70° dorsal–right ventral oblique projections, respectively). A—The left TMJ 5 months after the original injury. B—The normal right TMJ. There is minimal change in the appearance of the fracture at the 5-month recheck.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Side-by-side comparison of the left and right TMJs of the same horse as in Figure 1 (right 15° caudal 70° dorsal–left ventral oblique and left 15° caudal 70° dorsal–right ventral oblique projections, respectively). A—The left TMJ 5 months after the original injury. B—The normal right TMJ. There is minimal change in the appearance of the fracture at the 5-month recheck.
Citation: Journal of the American Veterinary Medical Association 252, 7; 10.2460/javma.252.7.805
Comments
To the authors' knowledge, the present report is the first to document an articular fracture of the lateral aspect of the condylar process of the mandible in a horse. In 1 other report,2 a fracture at the TMJ in a horse was associated with chronic sepsis of the joint. The right 15° caudal 70° dorsal–left ventral oblique radiographic projection of the TMJ, as previously described,1 proved invaluable for imaging the lateral aspect of the left condylar process in our patient and permitted a concrete diagnosis.
Routine radiographic imaging series of the TMJ in horses have been described as comprising laterolateral and left and right lateral oblique projections.3 Although these views may aid in diagnosis of TMJ luxation, osteoarthritis, or fractures, viewing the joint surfaces is difficult owing to superimposition and distortion. The view most helpful in the patient of this report may prove beneficial when TMJ diseases such as fracture of the lateral condylar process or osteoarthritis are suspected and CT is not an option because of financial constraints or lack of availability. This projection can be easily obtained in the field by use of a portable generator; however, for radiographic safety reasons, the use of a mobile generator stand or an in-house unit may be preferable.
References
1. Townsend NB, Cotton JC, Barakzai SZ. A tangential radiographic projection for investigation of the equine temporomandibular joint. Vet Surg 2009;38:601–606.
2. Devine DV, Moll HD, Bahr RJ. Fracture, luxation, and chronic septic arthritis of the temporomandibular joint in a juvenile horse. J Vet Dent 2002;22:96–99.
3. Farrow CS. Mandibular and temporomandibular joint fractures, infections, tumors, and tumorlike lesions. In: Farrow CS, ed. Veterinary diagnostic imaging: the horse. St Louis: Mosby Inc, 2006;339–352.
