TMJ Ankylosis Secondary to Gun Shot Injury: A Rare Case Report

INTRODUCTION

The head and midface areas are very common site of gunshot injury. These gunshot wound generally leads to major distortion and functional impairment, particularly when the temporomandibular joint (TMJ) is affected or when major anatomical structure such as the facial nerve is damaged, with the possible development of traumatic facial palsy.² Lesions of the temporal and marginal branches produce remarkable functional loss and those must be repaired. Temporomandibular joint ankylosis is generally classified into two main types – intra-articular (true) and extra-articular (false) ankylosis.The failure to move the mandiblehas significant functional consequences, such as the inability to eat a normal diet alterations of speech, difficulty for some individuals to communicate and express themselves to others.

This case report seeks to present an atypical case of surgical management of unilateral TMJ ankylosis and restricted mouth opening secondary to gunshot injury.

Case Report:

A 45 year old male Patient reported to the Department of Oral and Maxillofacial Surgery of DAPM RV Dental College and Hospital with a chief complaint of restricted mouth opening with anterior openbite secondary to gunshot injury. Patient hada alleged history of gun shot on his right side of the face while driving one year back and surgical management was done for multiple facial bone fractures and the avulsed soft tissue. After six months of follow up, the patient noticed difficulty in speech, mouth opening and lower jaw movements. On clinical examination facial asymmetry wasnoted with retruded chin and deviation of the mandible towards the right side. A mouth opening of 25mm was recorded. Flatness and elongation of the face noted on the unaffected side(Fig.1) with Classic Angle’s class II malocclusion on the affected side with a unilateral posterior cross bite on the ipsilateral side. CT confirmed a complete bony consolidation replacing the joint space with distortion of the normal TMJ anatomy.(Fig.2-3)

Treatment:

After adequate patient preparation with routine blood investigations, the ankylotic mass was removed and Interpositionalarthroplasty using Temporalis fascia flap was performed using pre-auricular surgical approach under general anaesthesia. The Pre-auricular incision was placed to gain access to the desired surgical field.The incision was outlined at the junction of the facial skin with the helix of the ear(Fig.4). A natural skin fold along the entire length of the ear wasused for the incision.The incision was made through skin and subcutaneous connective tissues (including temporoparietal fascia) to the depth of the temporalis fascia (superficial layer). Haemostasis was achieved before proceeding with deeper dissection.Blunt dissection was carried out until the superior portionof the incision was undermined (that the part above the zygomatic arch) and a flap was retracted anteriorly.At the root of the zygoma, another incision was made through both the superficial layer of temporalis fascia and the periosteum of the zygomatic arch. The sharp end of a periosteal elevator inserted in the fascial incision, deep to the superficial layer of the temporalis fascia, and swept back and forth motion to dissect this tissue from the underlying areolar and adipose tissues.Ankylotic mass was noted, exposed and excised to create a gap of 10 mm. Recontouring of the glenoid fossa was done and a maximum mouth opening of 37mm was measured and recorded.Temporalis fascia flap was adequately mobilized with the base of the flap lying above the zygomatic arch andinterpositioned in the gap between zygomatic arch and ramus stump and was secured to the posterior edge of the preauricular incision with 3 0 vicryl sutures. (figure.5-6) Patient was given physiotherapy in the form of jaw exercises from the third postoperative day. Postoperative follow up was done for one year and the healing was uneventful with no evidence of re-ankylosis.(Fig-7-8)

DISCUSSION:

Gunshot wound-related trauma to themidface and TMJ region is allied with transmission of aenormous amount of kinetic energy to the affected area, which in turn may cause damage to local anatomic structures such as bone and cartilage.⁷ Secondary to this injury may lead to complications such as edema, limited mouth opening, and TMJ ankylosis.¹

Surgical management of TMJ ankylosis includes A.Condylectomy B. Gap arthroplasty C.Interpositionalarthroplasty and D.Total joint replacement.

One of the surgical procedure is gap arthroplasty without interposition. Arthroplasty without interposition requires a gap of 10–20 mm.³ Topazian reported a recurrence rate of 53% for gap arthroplasty without interposition.⁴ Gap arthroplasty is not only a relatively simple procedure with short-operating time but also has disadvantages such as creation of pseudo articulation with a short ramus and an increased risk of TMJ reankylosis. Hence, interpositional gap arthroplasty is preferable. Verneuil introduced interpositional arthroplasty (1886) to reduce the high recurrence rate and the technical difficulties involved in the TMJ surgery. The main function of an interpositional material is to eliminate contact between two bony surfaces of the joint and avoid recurrence.⁵ The surgical protocol followed was the one proposed by Kaban et al in 2009 which included ankylotic mass resection, interposition of temporalis fascia, early mobilization with aggressive physiotherapy.⁶ A cautious surgical technique followed by careful atten¬tion to longterm physiotherapy considered to be vitalto achieve a satisfactory result.⁸ Many recent studies have shown that the choice of interposition material in case of interpositionalarthroplasty is significant in inhibiting recurrence.^9,10

The temporoparietalfascialflap is an axial flap based on the superficial temporal vessels. Deep to the skin and subcutaneous tissues is the superficial temporal fascia, also known as the temporoparietal fascia. At the superior temporal line, this fascial layer continues superiorly as the epicranium, also known as the galeaaponeurotica. It continues inferiorly at the level of the zygoma as the SMAS, or superficial musculoaponeurotic system.

The advantages of this flap includes

1. Autologous nature; therefore least immunoreactive.

2. Proximity to the joint, enabling excellent mobility andcoverage of the arthroplasty gap, minimal donor site morbidity both cosmetically and functionally.

3. Minimal damage to the temporal branch of the facialnerve.

4. Good resilience and blood supply.

5. Hollowing in the temporal region is not evident.

6. Minimal intraoperative blood loss.

7. Low degree of friction and good positional stability.¹¹

This report on our experience with the temporalis fascia flap used as an interpositioning material in the surgical management of TMJ ankylosis produced good results in mouth opening, jaw function, with no evidence of recurrence.