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EQUINE VETERINARY EDUCATION / AE / MARCH 2015


Case Report


Does temporomandibular joint pathology affect performance in an equine athlete?


E. Jørgensen*, M. T. Christophersen, M. Kristoffersen†, S. Puchalski†‡ and D. Verwilghen Department of Large Animal Sciences, University of Copenhagen, Tåstrup, Denmark; †Helsingborg Regional Animal Hospital – Evidensia, Helsingborg, Sweden; and ‡Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, USA. *Corresponding author email: elinj@sund.ku.dk


Keywords: horse; temporomandibular joint; performance; CT scanning


Summary Temporomandibular joint (TMJ) pathology is a rarely reported cause of decreased performance among equine athletes or at least seldom recognised. This case report describes the work-up of a high level dressage horse with decreased performance. Temporomandibular joint pathology was suspected based on computed tomography (CT) and the horse responded very well to joint treatment.


Introduction


Lameness and poor performance are common issues for which horse owners seek veterinary attention. Equine veterinarians are increasingly asked to investigate subtle riding issues and obscure lameness reported by the rider to affect the horse’s performance, but these may not be easy to detect in classical orthopaedic investigations. Clinical experience of the authors deem that with increasing frequency, owners present horses with the firm conviction that temporomandibular joint (TMJ) disease is related to performance issues in their sport horse.


Unfortunately, little is known about TMJ disease in horses


and it is often very difficult to detect and differentiate TMJ problems from other diseases as the symptomatology is not well described in the horse. Clinical signs are unspecific and have been reported to include headshaking, bitting problems, local swelling, decreased range of motion of the mandible, change in head carriage, quidding, masticatory problems and localised pain (Warmerdam et al. 1997; Weller et al. 1999a; May et al. 2001; Moll and May 2002; Carmalt andWilson 2005; Devine et al. 2005). In human patients the clinical manifestation of TMJ disorders include abnormal joint sounds, joint tenderness on palpation, myofacial pain associated with mouth opening, restricted range of motion, somatisation and depression symptoms (Celic et al. 2004; Schmitter et al. 2004; John et al. 2005; Manfredini et al. 2012). Dogs with clinical signs of TMJ osteoarthritis (OA) show pain on opening and closing the mouth and decreased range of motion in the joint. However, many canine patients diagnosed with TMJ OA by computed tomography (CT) do not exhibit any of these clinical signs (Arzi et al. 2013). This case report describes a performance horse with an


obscure riding problem which was shown to be related to a TMJ disease process.


Case history


An 11-year-old Danish Warmblood gelding was presented to the Large Animal Hospital, University of Copenhagen,


© 2014 EVJ Ltd


Denmark, for evaluation of decreased performance. The horse performedat a high level of dressage and during the last 3 months its professional rider had experienced difficulties in transitions, particularly in flying changes (at canter on the right rein) and had a general complaint about the horse being heavy and less willing to work on the right rein. Different bits were tried without any effect. Furthermore, it was observed that the horse often yawned when seeing the bridle. The horse received regular dental work. Temporomandibular joint disease had previously been mentioned to the owner by her advisors as a potential cause of decreased performance, but no clear indication of TMJ disease or work-up was reported in the history.


Clinical examination


A complete lameness work-up revealed that the horse’s conformation was relatively straight on both front limbs (left front limb more pronounced than right front), with a broken back toe axis. The horse was shod with bar shoes with small heel wedges. Flexion tests of both front limbs were negative. The horse was ridden in circles on soft and hard ground.


During warm-up exercise, a reduced cranial phase of the stride, noted as a grade 1/5 lameness, of the left front limb was seen. This low grade lameness reduced in intensity as the horse warmed-up. The left front limb lameness was not detectable on the circle on a hard surface, but was obvious on the circle on soft ground on the right rein. The horse showed tense head carriage on the right rein, working against the rider’s hand. Furthermore, the horse showed poor engagement relative to its educational level and it made mistakes in the flying changes. The horse was ridden by its usual rider and seen at different times during warm-up and full exercise. The horse resented saddling and palpation of the girth area. During static examination, head symmetry and carriage


were normal. The horse resented palpation of the TMJ area on both sides and was also reluctant for other sites on the head to be examined. A full dental examination was performed and a slightly decreased latero-lateral excursion of the mandible relative to the maxilla in right-to-left movement, compared with left-to-right, was noted. Intraoral inspection revealed small enemal points lingually on the 300/400 rows and small overgrowths caudally on 311/411. No further abnormal findings were noted. Although clinical examination revealed the horse to be


lame on the left front limb without clear clinical indication of TMJ disease, further investigation of the TMJ including a


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