Objectives
To present a clinical case of traumatic zygomatico-ramal ankylosis in a dog, highlighting diagnostic pitfalls, the role of advanced imaging, surgical treatment, and functional recovery.

Case History
“Leo,” a 3-year-old male Caucasian Shepherd Dog rescued as a stray in Turkey, had suffered from chronic trismus for over two years. He required hours to eat small amounts of food and was only able to drink by immersing his muzzle in water and sucking. Previous treatments-including corticosteroids for a presumed diagnosis of masticatory myositis, antibiotics, and NSAIDs-were unsuccessful. A primary left-sided entropion was diagnosed and surgically corrected in Turkey during the same period, but recurred and remained present at referral.

Methods
Clinical examination confirmed inability to open the mouth, making intraoral evaluation impossible. Multi-detector CT (MDCT) revealed an osseous bridge between the zygomatic arch and the mandibular ramus. A lateral surgical approach was undertaken, and the ankylotic mass was removed using piezosurgery. Postoperative management included tracheostomy-based anaesthesia, multimodal analgesia, professional physiotherapy, and structured home care.

Results
Immediate restoration of mandibular mobility was achieved, with the dog regaining normal eating and drinking behaviour. No recurrence of ankylosis was noted on follow-up.

Conclusions
Zygomatico-ramal ankylosis is a rare but surgically treatable cause of canine trismus. CT is superior to radiography for accurate diagnosis and preoperative planning. Combined surgical and physiotherapeutic management can restore full function and dramatically improve quality of life.

Introduction
Trismus, or the inability to open the mouth, is an uncommon but functionally devastating condition in dogs. It compromises essential functions such as eating, drinking, thermoregulation, and oral grooming, and it can significantly reduce quality of life. A wide range of underlying conditions may lead to trismus, including inflammatory, neoplastic, infectious, neuromuscular, and traumatic causes. Distinguishing among these requires careful clinical assessment, appropriate imaging, and a high index of suspicion for rarer entities such as extra-articular ankylosis. The present report describes a case of traumatic zygomatico-ramal ankylosis in a young Caucasian Shepherd Dog. To our knowledge, this presentation is exceptionally rare. The case emphasises the importance of advanced imaging, surgical precision, and structured postoperative rehabilitation.

Differential Diagnoses for Trismus in Dogs
• Masticatory myositis
• emporomandibular joint (TMJ) ankylosis
• TMJ osteoarthritis
• Craniomandibular osteopathy
• Zygomatic arch and/or coronoid process fracture
• Tetanus
• Abscess or cyst
• Neoplasia
• Ear disease
• Ocular disease (retrobulbar lesion)
• Retropharyngeal abscess

 In Leo’s case, initial misdiagnosis as masticatory myositis delayed appropriate treatment. Corticosteroid therapy failed, underlining the importance of ruling out extra-articular ankylosis.

Case History
Leo, a 3-year-old intact male Caucasian Shepherd Dog, had been rescued as a stray in Turkey. His condition had been progressive since the presumed traumatic event two years earlier. The owners reported that he could only ingest food by pushing individual kibbles between his teeth, taking hours to finish a meal. Drinking was achieved by immersing his muzzle and sucking water, rather than lapping. Veterinary care abroad included radiography, corticosteroid therapy, antibiotics, and NSAIDs. None resulted in clinical improvement. At the same time, a primary entropion of the left eye was diagnosed and surgically corrected in Turkey, but the condition recurred and remained present at the time of referral. The dog was subsequently referred to our service after relocation to Belgium.

Diagnostic Work-up
Clinical Examination
On admission, Leo exhibited complete inability to open his mouth. This prevented direct intraoral examination or assessment of occlusion. Palpation revealed no overt pain, but functional evaluation was impossible. The severity of the restriction underscored the need for advanced imaging. Routine haematology and serology were within normal limits, and no cardiac abnormalities were detected. Ophthalmological evaluation confirmed a persistent left-sided primary entropion, which had already been surgically corrected in Turkey at the time of the presumed diagnosis of masticatory myositis, but without lasting success.

Imaging
Conventional radiographs obtained in Turkey had been inconclusive. The limitations of radiography are well recognised: superimposition of complex craniofacial structures reduces sensitivity for detecting ankylotic lesions. Computed tomography (CT) was therefore performed using a multi-detector CT (MDCT) scanner. The advantages of CT over radiography include:
• Elimination of superimposition, enabling 3D reconstruction.
• Precise evaluation of fracture or fragment orientation.
• Clear delineation of ankylotic masses and adjacent structures.
In comparative studies, CT detects approximately 1.6 times more traumatic injuries in dogs and twice as many in cats than radiography. This reinforces its role as the diagnostic modality of choice for maxillofacial ankylosis. In Leo’s case, MDCT revealed a dense osseous bridge between the right zygomatic arch and the ascending ramus of the mandible, confirming the diagnosis of extra-articular zygomatico-ramal ankylosis.

Preoperative Planning and 3D Printing
CT data can be converted into three-dimensional (3D) printed models to aid preoperative planning. Such models provide tactile and visual reference for surgeons, allow simulation of surgical access, and are a powerful communication tool with owners. In this case, the MDCT scan was primarily used digitally, but 3D printing remains a valuable adjunct in complex craniofacial surgery.

Owner Discussion
Prior to surgery, the findings, prognosis, and potential complications-including recurrence, intraoperative haemorrhage, and nerve injury-were discussed extensively with the owners. The importance of intensive postoperative physiotherapy was emphasised.

Anaesthetic Management
Airway management posed a major challenge in this case due to the complete inability to open the mouth. Standard orotracheal intubation was not possible. Fibre-optic guided intubation, occasionally described in veterinary anaesthesia, was considered; however, the severity of the trismus precluded its use in this patient. General anaesthesia was therefore induced with propofol. A temporary tracheostomy was then performed, and a 9.5 mm endotracheal tube was inserted directly through the stoma to secure the airway (“tracheostomal intubation”). Anaesthesia was maintained with inhalant agents delivered via the tracheostomy tube. Analgesia was provided intraoperatively by means of a continuous intravenous fentanyl–lidocaine–ketamine (FLK) infusion, ensuring stable and balanced pain management. Cardiovascular and respiratory parameters were continuously monitored throughout the procedure. The tracheostomy was closed at the end of surgery without complications.

Surgical Procedure
A skin incision was made over the left zygomatic arch. The overlying fascia and fibrotic tissue were bluntly dissected, and the surgical field was maintained under optimal exposure with a Lone Star Retractor. To improve access, the caudal segment of the zygomatic arch was resected. The fibrotic callus tissue, secondary to an old fracture, was carefully separated and excised. This provided full exposure of the ankylotic mass adjoining the mandibular ramus. The bony bridge, together with the surrounding fibrotic tissue, was removed using a piezotome, which allowed precise and selective resection of mineralised structures while sparing adjacent soft tissues. The operative site was copiously irrigated. Closure was carried out in layers: the fascia was sutured with PDS 3-0, the subcutaneous tissue with Monocryl Plus 4-0, and the skin with Ethilon 3-0. The tracheostomy was closed at the end of the procedure by placing simple interrupted sutures in the tracheal rings (PDS 3-0), continuous closure of the sternohyoideus (PDS 3-0), followed by continuous subcutaneous closure and intradermal skin sutures with Monocryl 4-0. A pressure bandage was applied.

Postoperative Management and Physiotherapy
Postoperative care included multimodal analgesia, anti-inflammatory medication, and prophylactic antibiotics. At the end of surgery, the continuous FLK infusion was discontinued and the patient was transitioned to methadone for systemic analgesia. The FLK infusion remained available for re-initiation if pain control proved insufficient. Upon recovery from anaesthesia, Leo was already able to open his mouth to approximately 6 cm. Once fully awake, he immediately demonstrated vigorous mandibular function by chewing through his intravenous line - a somewhat inconvenient but reassuring sign that his ability to bite had not been lost. The dog was discharged with the following home-care regimen:
• Meloxicam oral suspension (Meloxoral), administered once daily at the weight-adjusted dose (40 kg), for ten days, starting the morning after discharge. Owners were instructed never to administer the drug on an empty stomach and to discontinue immediately if vomiting, diarrhoea, or melena occurred.
• Amoxicillin–clavulanic acid (Clavaseptin 500 mg), one tablet twice daily for ten days.
• Wound care: daily inspection for discharge, erythema, or swelling. A protective collar was to be worn at all times to prevent licking or scratching. Special attention was drawn to the cervical tracheostomy site. The external bandage could be removed after three days or sooner if it detached spontaneously.
• Dietary management: unrestricted access to food, with soft pâté recommended in small, frequent portions to encourage licking and mandibular movement.
• Follow-up examination scheduled one week postoperatively.
• Ocular care: the left eye remained visual but was irritated by inward rolling of the lower eyelid. The entropion was confirmed as primary but was thought to be exacerbated by deeper positioning of the globe following surgery. Potential complications included ulcerative keratitis and reduced vision. The owner was advised to plan a blepharoplasty of the left lower eyelid once postoperative swelling had fully resolved, ideally after several weeks. In the interim, the eye was to be protected with frequent application of lubricating gel. Should ulcerative keratitis or excessive irritation occur, earlier surgical correction was recommended.
• Physiotherapy: professional physiotherapy sessions were initiated and supervised by a certified veterinary physiotherapist. The programme included both passive and active mouth-opening exercises, gradually increasing in intensity, and owner involvement was encouraged to maintain continuity at home.

Results
Leo regained the ability to open his mouth to a normal functional range. Immediately postoperatively, mandibular excursion measured 6 cm. He was able to eat dry food without assistance and resumed normal drinking behaviour. At follow-up seven weeks later, coinciding with surgical correction of the left-sided entropion (blepharoplasty), Leo’s maximum mouth opening had further improved to 9 cm. No recurrence of ankylosis was observed, and overall quality of life was considered excellent.

Discussion
This case demonstrates the diagnostic pitfalls of chronic trismus in dogs. Initial treatment for presumed masticatory myositis delayed correct intervention, a reminder that absence of clinical improvement with corticosteroids should prompt reconsideration of the diagnosis. CT proved indispensable, revealing an osseous bridge hidden by superimposition in radiographs. Literature supports CT’s superiority, detecting up to 1.6× more injuries in dogs and 2× more in cats compared to radiography. 3D printing, while not utilised here, represents a powerful adjunct for planning and client communication. Surgical management using piezosurgery allowed precise removal of the ankylotic mass with minimal collateral trauma. The Lone Star Retractor facilitated atraumatic soft tissue handling and excellent exposure of the surgical site. Postoperative recovery underscored the crucial role of professional physiotherapy in maintaining function and preventing recurrence. While owner-led exercises are important, the structured involvement of a veterinary physiotherapist provided tailored therapy, progressive adaptation, and improved compliance, likely enhancing long-term outcome. Extra-articular ankylosis between the zygomatic arch and mandibular ramus is exceedingly rare, but recognition and surgical intervention can restore normal function and quality of life.

Conclusion
Zygomatico-ramal ankylosis should be included in the differential diagnosis of chronic trismus in dogs, especially those with a history of trauma. CT is the diagnostic modality of choice, offering superior lesion characterisation. Surgical removal with piezosurgery, combined with professional physiotherapy and structured home care, can result in complete functional recovery.

References
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