192
Clinical Communication
© 2007
Schattauer GmbH
Temporomandibular joint ankylosis in cats and dogs A report of 10 cases C. P. H. J. Maas, L. F. H. Theyse Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, University of Utrecht, The Netherlands
Summary
Temporomandibular joint (TMJ) ankylosis is characterized by difficulty or inability to open the mouth. The ankylosis may be articular (‘true’) or extra-articular (‘false’). Clinical signs, radiographic studies, treatment and follow-up are presented in a retrospective study involving five cats and five dogs. The findings were compared with TMJ ankylosis in humans. CT imaging with three-dimensional reconstruction proved to be of great value in determining the extent of the abnormalities and helped with preoperative planning. Articular TMJ ankylosis occurred in six animals and extra-articular TMJ ankylosis was found in the other four cases. In three cats and in three dogs, the TMJ ankylosis was trauma related; the remaining patients were diagnosed with a tumour. Resection of ankylosing tissue in false ankylosis or gap arthroplasty in true ankylosis was successful in all of the trauma induced cases. In the two cats, with tumour related ankylosis, the ankylosis was caused by an osteoma and resection had a good prognosis, whereas the two dogs had to be euthanatized.
Keywords
Temporomandibular joint ankylosis, diagnostic imaging, surgical treatment, cat, dog Vet Comp Orthop Traumatol 2007; 20: 192–197 Prepublished online July 26, 2007 doi:10.1160/VCOT-06–08–0062
Introduction In immature animals, ankylosis of the temporomandibular joint (TMJ) can lead to malocclusion and craniofacial malformation. The TMJ is a condylar joint that allows opening and closing of the mouth, and sliding movements in the dog (2). In the cat, the teeth can only be moved in one plane and grinding is not possible (3). The actual joint consists of the condylar process of the mandibular ramus, the mandibular fossa of the temporal bone, a thin articular disc, and a loose joint capsule, which is strengthened by a fibrous lateral ligament in the dog. In cats, the articular disc is just a thin fibrous lamella (4). In close proximity of the TMJ are the masseter, temporalis, digastric and lateral and medial pterygoid muscles (5). Bony structures that are located near the TMJ are the coronoid process of the mandible, the zygomatic arch, the retro-articular process, and the temporal, basisphenoid and pterygoid bones (6). In humans, TMJ ankylosis may result from trauma, haemarthrosis, infection or arise as a complication of surgical treatment of the condylar area (7–9). In cats and dogs, TMJ ankylosis has been attributed to trauma from car accidents and falling from heights, as well as developmental, inflammatory and neoplastic causes (1, 10–15). This study was aimed at the evaluation of the diagnosis and treatment of the condition in cats and dogs.
Materials and methods The case records of cats and dogs with TMJ ankylosis seen between 1994 and 2005 were Vet Comp Orthop Traumatol 3/2007
reviewed. The main criteria required for inclusion in this study were: difficulty or inability to open the mouth at first presentation, presence of abnormal tissue on radiographs or CT imaging, and being available for follow-up. Patients with masticatory muscle myositis, which resulted in false TMJ ankylosis, were excluded (16). The retrieved data included: species, breed, gender and age at presentation, which are provided in Table 1. After a complete physical and pre-anaesthetic examination, the maximum mouth opening was determined by measuring the inter-incisor gap under general anaesthesia. Diagnostic imaging of the skull, consisting either of radiographs in standard dorsoventral, lateral and oblique views, or CT imaging, or a combination of both, was performed. Surgical treatment was aimed at restoring free movement of the mandibula. Osteotomy of the zygomatic arch was performed whenever necessary. Histopathology was performed when there was not a clear trauma related cause. The results of treatment were determined during return visits in the clinic or by telephone interview with the owner. The cause, affected side, type of ankylosis, performed diagnostic imaging, surgical treatment, results of histopathology and the follow-up time in months with the clinical outcome are outlined in Table 2.
Case reports Case #1 A five-month-old, male, Maine Coon cat was admitted because of its inability to open its mouth. Three weeks previously there had Received August 10, 2006 Accepted November 20, 2006
193 Temporomandibular joint ankylosis
Table 1 Clinical data.
Case No.
Species
Breed
Gender
Age at presentation
01
Cat
Maine Coon
Male
05 months
02
Cat
Domestic Shorthair
Castrated male
01.5 years
03
Cat
Domestic Shorthair
Spayed female
03 years
04
Cat
Domestic Shorthair
Castrated male
10 years
05
Cat
Domestic Shorthair
Castrated male
11 years
06
Dog
German Shepherd
Male
04 months
07
Dog
Flatcoated Retriever
Male
06 months
08
Dog
German Shepherd Dog
Female
08 months
09
Dog
Fox Terrier
Male
03.5 years
10
Dog
Boxer
Castrated male
05 years
been evident head trauma, but the precise cause was unknown. Physical examination revealed an asymmetrical mandible, malocclusion and maximum mouth opening of 8 mm. CT examination was performed with three-dimensional reconstruction of the skull and showed extensive ‘new bone’ formation fusing the left coronoid process and the zygomatic arch (Fig. 1). Both TMJ were intact without any abnormalities. The bony callus causing the fusion between the coronoid process and the zygoma was removed through a surgical approach dorsal from the zygomatic arch and the range of motion (ROM) was completely restored. ImTable 2
mediately following surgery a mild facial nerve paralysis was noticed resulting in the inability to close the left eye. Ocular ointment was used to protect the cornea from damage and the facial nerve paralysis had completely resolved after eight weeks. Twelve months postoperatively the ROM was good with normal function of the TMJ.
Case #2 A one-and-a-half year-old, castrated male, Domestic Shorthair cat was referred because of TMJ ankylosis, which had been
present for two weeks. Eight weeks before it had been hit by a car and had consequently suffered a mandibular separation and dislocation of the left TMJ, which was treated conservatively. Its mouth could only be opened by one centimeter. Radiographs revealed lateral dislocation of the left mandibular condyle contacting the lateral part of the zygomatic process of the temporal bone. A lateral surgical approach of the region of the left TMJ was performed and revealed a nearthrosis and ankylosis at the base of the zygomatic arch. In order to permit exposure of the condylar process, an osteotomy of the zygomatic arch was necessary; the process and the fibrous attachments surrounding the nearthrosis were removed. The zygomatic osteotomy was repaired with 0.6 mm cerclage wire. The ROM was completely restored but six weeks later it had decreased and the referring veterinarian stretched the jaw under sedation.
Case #3 A three-year-old, spayed, female, Domestic Shorthair cat was referred because of TMJ ankylosis. Eight weeks before it had been hit by a car and had suffered a mandibular separation, which was treated with interdental
Diagnosis and treatment.
Case No.
Cause
Affected side
Type of ankylosis
Diagnostic imaging
Treatment
Histopathology
Follow-up in months
Outcome
01
Unknown trauma
Left
False
CT
A
-
012
Good
02
Hit by car
Left
True
R
A, Bc, o
-
001.5
Poor
03
Hit by car
Left
True
R, CT
A
-
034
Good
04
Tumour
Right
False
CT
A, Bc, Dp
Osteoma
040
Good
05
Tumour
Left
True
R
A, Bp
Osteoma
067
Good
06
Bite trauma
Right
True
CT
A, Bc, Cc, Dp, Ep
Reactive periostal new bone formation
076
Good
07
Unknown
Left
False
R, CT
1. A 2. Cp, Dp 3. Dp 4. Dp
1– 4. Benign bone, cartilage and connective tissue, no evidence of malignancy
1. 6 2. 1.5 3. 3.5 4. 47
1– 3. Poor 4. Good
08
Unknown trauma
Right
False
CT, R
Cp, o
Chronic fibrosis
116
Good
09
Tumour
Right
True
R
F
Osteosarcoma
000
Poor
10
Unknown
Left
True
CT
1. A 2. A, Bc
1. Degenerative arthropathy 2. Cartilaginous exostosis
1. 1.5 2. 2
1. Poor 2. Poor
CT=computed tomography; R=radiographs skull; A=resection of ankylosing tissue; B=condylectomy; C=coronoidectomy; D=mandibulectomy; E=removal mandibular fossa temporal bone; p=partial; c=complete; o=osteotomy zygomatic arch; F medication (analgaesics).
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194 Maas, Theyse
and the TMJ thus restoring the ROM completely. The follow-up examination 34 months later showed good function and a normal ROM.
Case #4
Fig. 1 Three-dimensional CT reconstruction of the skull in a five-month-old Maine Coon in a cranial view (Case #1). The patient was admitted with temporomandibular joint ankylosis after head trauma. An extensive bone proliferation fusing the left coronoid process and the zygomatic arch is shown. The ankylosis had caused an asymmetrical mandible with malocclusion.
A)
A ten-year-old, castrated, male, Domestic Shorthair cat was admitted with right sided exophthalmus. The ROM of the TMJ was markedly decreased. CT investigation showed a 3 cm wide dense bony mass on the medial side of the right mandibular ramus, with extension towards the neuro-cranium, directly passing the unaffected TMJ (Fig. 2). Excision of the mass including the mandibular ramus and condyle was performed through a ventral and lateral approach, leading to direct resolution of the exophthalmus. Histopathologic examination of the excised bone revealed a benign bone proliferation consistent with an osteoma. The follow-up after 40 months showed a normal ROM, with residual open bite on the left side.
Case #5
Fig. 2 Three-dimensional CT reconstruction of the skull of a ten-year-old Domestic Shorthair cat in a cranial view (Case #4). The patient was admitted with TMJ ankylosis and right sided exophthalmus. A bony mass is shown on the medial side of the right mandibular ramus, with extension towards the neurocranium. Histopathology diagnosed an osteoma after resection.
wire fixation by the referring veterinarian. The maximum mouth opening was 7 mm. Radiographs showed an irregular TMJ on the left side. CT investigation showed an abnormal left TMJ, probably caused by a fracture of the condyle, surrounded by periostal new bone formation. Through a lateral approach the extensive ‘new bone’ formation was removed between the zygomatic arch Vet Comp Orthop Traumatol 3/2007
B) Fig. 3 A) Transversal CT image of the skull of a sixmonth-old Flatcoated Retriever in a cranial view (Case #7). The patient was admitted with temporomandibular joint ankylosis. A bone proliferation is visible at the level of the last molar teeth fusing the mandibula and the pterygoid bone. B) Three-dimensional CT reconstruction of the left half of the skull in a caudal view shows the bone proliferation between the mandibular ramus and pterygoid bone.
An eleven-year-old, castrated, male, Domestic Shorthair cat was presented because of decreased ROM of the mouth and a palpable hard swelling at the level of the TMJ. Radiographs revealed a round irregular bony mass, with a radiolucent centre, lateral to the TMJ and directly ventral of the zygomatic arch. During surgery the mass was found to be attached to the lateral part of the condylar process; it was completely removed, necessitating a partial condylectomy. Histopathology showed a benign bone proliferation consistent with an osteoma. Follow-up eight weeks later showed full ROM of the TMJ and radiographic evaluation of the surgical site did not show any regrowth. A follow-up examination after 67 months showed good ROM without any regrowth of the osteoma.
Case #6 A four-month-old, male, German Shepherd Dog was referred for TMJ ankylosis and
195 Temporomandibular joint ankylosis
mandibular brachygnathism with near normal occlusion of the canine teeth. It had been bitten by the bitch shortly after being born. Maximum mouth opening was 3 cm and there was a distinct deformity of the skull. CT imaging revealed an abnormally developed right TMJ and callus formation between the TMJ, coronoid process and the zygomatic arch. A partial mandibulectomy, including the coronoid process, mandibular ramus and condylar process, which restored the ROM to near normal, was performed. Histopathology demonstrated reactive periostal bone proliferation. Ten weeks later, the follow-up examination, showed a normal ROM of the right TMJ. In the meantime, the dog had developed an otitis media on the left side, which was successfully treated with systemic antibiotics. It was not clear whether the otitis was related to the former TMJ problem. An examination after 76 months showed a good ROM. Although the mandible tended to deviate to the right, the minor malocclusion did not pose a clinical problem.
Case # 7 A six-month-old, male, Flatcoated Retriever was referred because of TMJ ankylosis in combination with a very narrow skull and a mandibular brachygnathism. The maximum possible mouth opening was 2 cm. Radiographs and CT imaging showed a bone proliferation at the level of the last molar teeth between the mandibula and the pterygoid bone on the left side (Fig. 3A, B). The appearance of both TMJ was normal.A ventral surgical approach was used medial from the mandibular corpus to excise the bone proliferation, thus restoring full ROM. During the next five weeks the ROM decreased to a maximum mouth opening of 4 cm. At this time, CT imaging showed recurrence of bone proliferation between the mandible and the pterygoid bone. In view of the early recurrence of the ankylosis and the fact that the dog was able to eat and drink unassisted, surgery was postponed until the skull was fully developed. In the following months maximum mouth opening decreased progressively to 1 cm. At this time, CT images showed recurrence of the mineralization be-
Case #8
Fig. 4 Three-dimensional CT reconstruction of the skull of an eight-month-old German Shepherd Dog in an oblique cranial view (Case #8). The patient was admitted with swelling on the right side of the head and progressive temporomandibular joint ankylosis. A bone proliferation and malformation of the coronoid process is shown on the right side.
tween the medial side of the mandible and the pterygoid bone. A partial resection of the left mandible, just caudal of the third molar tooth (311) and including part of the coronoid process, was performed to eliminate the ankylosis. Using rongeurs, the bone proliferation was removed, as radically as possible, until the ROM was restored. After one month ankylosis recurred and radiographs showed extensive callus formation at the surgical site. In a third attempt to overcome the ankylosis, a critical-sized mandibular bone defect was created by performing a partial full-height mandibulectomy including the first to third molar teeth (309 to 311). After two months healing of the mandibular defect took place, resulting in recurrence of the ankylosis.At an age of one-anda-half years, a ventral approach was used to perform a caudal partial mandibulectomy, including the fourth premolar tooth (308) to the condylar process. Histopathology was performed after each surgery and demonstrated normal bone, cartilage and connective tissue without any evidence of malignancy. The follow-up examination, 47 months after the last surgery, showed a good ROM and good function, despite the amputated left TMJ.
An eight-month-old, female, German Shepherd Dog was referred because of TMJ ankylosis. Although an occurrence of trauma was not known, a swelling was noted at the right side of the head in the region of zygomatic arch. From this time the ROM decreased gradually. The maximum mouth opening was 2 cm and the dog demonstrated a 1 cm mandibular brachygnathism with near normal occlusion of the canine teeth. The CT images showed a deformity of the coronoid process of the right mandible (Fig. 4). The coronoid process made contact with the zygomatic arch without a clear bony fusion. Both TMJ were intact. The zygomatic arch was sectioned to reach the deformity of the coronoid process and partial coronoidectomy was performed. The zygomatic arch was reattached with 0.8 mm cerclage wire. Histopathology of the excised material showed normal bone tissue and locally some cartilaginous tissue which was considered to be chronic fibrosis due to trauma. Six weeks later the ROM was good. Radiographic examinations showed some reactivity at the plane of resection, but there was not any evidence of complications. Follow-up after 116 months showed good ROM, the mandibular brachygnathism was not resolved but did not cause any clinical problems.
Case #9 A three-and-a-half year-old, male, Fox Terrier was referred because of painful opening of the mouth with a decreased ROM and a swelling over the right TMJ.An aspirate from the swelling revealed blood and muscle fibres. An irregular structure of the condyle of the right TMJ was visible on the radiographs and some minor calcifications in the surrounding soft tissue, suggestive of degenerative changes due to old trauma or infection.The dog was treated with analgaesics, which had a good clinical effect and reevaluation was planned two months later. At this time the ROM had decreased and radiographs demonstrated extensive osteolysis and bony proliferations.Another aspirate from the swelling revealed a very malignant anaplastic tumour.The dog was euthanatized and histopathology showed an osteosarcoma. Vet Comp Orthop Traumatol 3/2007
196 Maas, Theyse
Case #10 A five-year-old, castrated, male, Boxer was admitted with painful opening of the mouth without a known history of trauma. Its mandible deviated to the right. CT examination with three-dimensional reconstruction showed extensive, well marginated, bony proliferations surrounding the left TMJ (Fig. 5A, B). Through a lateral approach the abnormal tissue was removed with rongeurs for histopathology. Evidence of a tumour was not found and the initial diagnosis was degenerative arthropathy. The signs of TMJ ankylosis were progressive and seven weeks later a second surgery was performed. The TMJ sack was considerably enlarged and contained many free cartilage-covered bone fragments which were removed. There was extensive erosion of the cartilage of the condylar process and a condylectomy was performed. The definitive diagnosis was ‘cartilaginous exostosis’. Despite debulking of the TMJ, signs of pain and ankylosis recurred and were aggravated by a head tilt and ataxia. There was a growing mass over the left TMJ and the owner decided on euthanasia three months after surgery.
Discussion Ankylosis of the TMJ is rarely seen in veterinary practice and reports mainly concern cats. TMJ problems in cats are related to traffic accidents, falls from heights (1, 12, 13, 15) or osteoma (11). The findings in this study are consistent with earlier reports. In the dogs, the main cause of TMJ ankylosis was also trauma associated. Although not always observed by the owner, traffic accidents or other impact trauma were highly suspected in most cases. Trauma can either be direct to the TMJ or indirect, by means of impact to another part of the skull (17). After trauma, the condylar movements can be impaired by damage of the articular disc and the condylar surface (18–20). In addition, intra-articular haemorrhage can result in cartilage degeneration and osteoarthritis (21). Trauma to the TMJ region can lead to extensive muscle damage and subsequent fibrosis (17). Vet Comp Orthop Traumatol 3/2007
A)
B) Fig. 5 A) Transversal CT image of the skull of a fiveyear-old Boxer in a caudal view at the level of the temporomandibular joints (Case #10). The patient was admitted with painful opening of the mouth without known trauma. Extensive, well marginated, bone proliferations are shown surrounding the left temporomandibular joint. B) Threedimensional CT reconstruction shows multiple well marginated bone proliferations surrounding the left temporomandibular joint.
Trauma related TMJ ankylosis was typically found in the young cats and dogs in this series, whereas tumour related ankylosis occurred in the older age group. Although the number of cases was limited, osteoma seemed to have a good prognosis in the cats. In contrast, tumour related ankylosis in dogs had a poor prognosis. When a tumour is suspected a biopsy is essential to differentiate between fibrosis and new bone formation or malignancy. In human medicine, facial asymmetry is considered the classic feature of unilateral TMJ ankylosis. Brachygnathism is often associated with bilateral TMJ involvement. In facial asymmetry the chin deviates to the affected side because of fixation on this side
and continuation of growth on the contralateral side in young individuals. Difference in length of the mandibular ramus can lead to tilting of the mandibula in the long axis of the skull and leads to an open bite on the contralateral side (8). In this study, malocclusion, facial asymmetry and mandibular brachygnathism were common findings. Radiography has limited diagnostic value in evaluating complex problems of the TMJ and skull bones. Oblique views are helpful for visualization the TMJ, but superimposition remains a problem (22). The true incidence of trauma related TMJ damage may be higher than previous reports have shown because of these limitations (1). In the authors’ opinion, CT imaging is essential in evaluating TMJ ankylosis. In human medicine, CT and MR imaging are routinely used for TMJ problems (23, 24). MR imaging is indicated for diagnosis of articular disc problems and inflammatory conditions (23). CT is preferred for the imaging of the bony components of the TMJ. Helical scanning enables three-dimensional reconstructions, which are of great value for visualizing TMJ ankylosis. Contrast studies can be useful to differentiate between neoplasia, masticatory muscle myositis, middle ear disease or cerebral involvement (22). When investigating TMJ problems it is important to realize that both TMJ act functionally as a single unit, which means that any pathology on one side can result in abnormal contralateral function. This can lead to secondary degenerative changes on the contralateral side that should not be misinterpreted as primary disease (20). In general, the ankylosis will not respond to forceful opening of the mouth and stretching will result in additional trauma with a high risk of recurrence (12, 13). During the stretching procedure excessive forces can induce mandibular fractures (1). Forceful opening of the mouth can also lead to additional trauma of the contralateral non-affected side (25). As maximum mouth opening is severely compromised in most patients, visualization of the larynx and intubation can be difficult. A fibre optic scope can be useful in these cases. If laryngeal intubation is not possible a tracheotomy can be performed. In human medicine three basic techniques for surgical correction of TMJ anky-
197 Temporomandibular joint ankylosis
losis are available: interpositional arthroplasty (resection of the bony mass combined with filling of the gap with biological or non-biological material); joint reconstruction (resection of the bony mass with reconstruction by bone grafts or joint prosthesis), or gap arthroplasty (resection of the bony mass without placing other material in the gap) (26). In veterinary medicine, gap arthroplasty is recommended in the case of true ankylosis (11, 13). Four cases with false ankylosis in this study were successfully treated with resection of the ankylosing tissue without arthroplasty. Gap arthroplasty was performed in the remaining patients. Human surgery techniques employ various materials for an interpositional graft, for example biological materials: full thickness skin graft (27, 28), temporalis muscle (27, 29), costal cartilage (27, 30) and fascia lata (27), and non-biological materials: acrylic spacers (8) and silastic tubing (26, 31). The costochondral graft is mostly used as a biological graft and for joint reconstruction in young individuals. This technique is employed because of the potential for additional growth after implantation (26). The success rates of these procedures vary greatly between various reports, and disadvantages such as morbidity at the donor site, unpredictable resorption and foreign body reactions have been described (8, 25–27, 31). In order to minimize the severity of facial deformity caused by restriction of facial growth in young individuals, surgical intervention in human patients is recommended as early as possible (29). Early intervention is also essential in growing cats and dogs because these young animals demonstrate a great healing tendency and the potential for extensive callus formation, the risk of re-ankylosis, and the consequent necessity for repeated surgery, has to be taken into account. Facial nerve paralysis is observed in up to 20% of the cases in humans after surgical treatment. Excessive intra-operative retraction of surrounding tissues to reach the TMJ is held responsible for this complication (25). In this study one case (10%) with temporary mild facial paralysis was observed. A considerable degree of failure, resulting in re-ankylosis, is apparently related to insufficient postoperative physiotherapy in
human patients (25). In dogs and cats, early rehabilitation of the TMJ by feeding small amounts of food, in several meals, and encouraging opening and closing of the jaw manually or with toys is recommended.
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Correspondence to: L. F. H. Theyse Universiteit Utrecht Dept. of Clinical Sciences of Companion Animals Yalelaan 8 PO BOX 80154 3508 TD Utrecht The Netherlands Phone: +31 3025 31696, Fax: +31 3025 18126 E-mail: L.F.H.Theyse@vet.uu.nl
Vet Comp Orthop Traumatol 3/2007