Zygomatico-coronoid Ankylosis as Sequel of Inadequate Treatment.

Temporomandibular joint ankylosis may be true or false. Most commonly, trauma and inflammatory conditions lead to this condition. Zygomatico-coronoid ankylosis is a rare extra-articular (false) form of ankylosis of the jaw. This condition may follow treated or untreated midface fractures. Coronoid process locking may be overlooked because attention is generally focused on temporomandibular joint. A review of literature has reported 16 cases of this disorder. The true incidence of this condition may be even higher. In this paper, we present an unusual case of posttraumatic bony ankylosis of the right coronoid process of the mandible with the zygomatic arch in a 30-year-old male. This bony ankylosis was produced by a mass of heterotopic bone formed, following inadequate treatment of midfacial fracture. Extra-oral ostectomy of the ankylotic mass followed by immediate postsurgical aggressive physiotherapy produced good long-term functional outcome.

INTRODUCTION

Facial trauma is most commonly associated with road traffic accidents, falls, assaults, and sport-related trauma. Mandible, temporomandibular region, and middle third region of the face are often involved in such facial injuries. The complex nature of the temporomandibular joint (TMJ) region and its anatomical proximity to important craniofacial structures makes diagnosis and treatment of any TMJ disorder, especially challenging.[1] Facial asymmetry, malocclusion, growth disturbance, ankylosis, and osteoarthritis can manifest as complications following trauma to the TMJ region.[2] The disorder also has an adverse impact on the psychology as well as social life of the individual.

Temporomandibular joint ankylosis is basically classified into two types – intra-articular (true) and extra-articular (false) ankylosis. Fibrous or bony adhesion between the coronoid process and zygomatic arch is a rare cause of extra-articular ankylosis. This condition may follow facial fractures caused by gunshot injuries, treated and untreated fractures of the zygomatico-maxillary complex or mid-face with or without concomitant fracture of the coronoid process, fracture of the mandible, infratemporal space infection, local surgical complications, or chemical burns.[3] The main symptom of this condition is restricted mandibular movements caused by the union of the zygoma and the coronoid process of the mandible.[4]

Zygomatico-coronoid ankylosis (ZCA) was first described by Brown and Peterson. The fusion of the coronoid process of the mandible to the zygomatic bone has been sporadically reported in the literature. A review of literature has reported 16 cases of this entity. Two of such cases were caused by infection, two cases occurred following surgical interventions, while trauma was etiological factor in twelve cases. The treatment planning includes surgical excision of the ankylotic mass followed by vigorous jaw opening exercises.[5]

ZCA has been frequently overlooked and treated as a TMJ disorder. A very few studies on ZCA have been published so far. The purpose of this article is to present a rare occurrence of ZCA subsequent to inadequate treatment and to review the literature.

CASE REPORT

A 30-year-old male reported to our department with chief complaint of painless but progressively reducing mouth opening for 5 months. He was the victim of a motor vehicular accident which occurred 6 months back, sustaining trauma to the face and was diagnosed as a case of Lefort III # with midsymphysis of the mandible #. He was operated and lateral suspension was done for Lefort III # and miniplate fixation was done for midsymphysis #. The patient was discharged uneventfully after 1 week and was advised for regular follow-up. One month postoperatively, the patient noticed a gradual reduction in mouth opening. The patient was advised active jaw physiotherapy but there was no benefit. The patient was lost on follow-up but he reported with the chief complaint of reduced mouth opening [Figure 1a].

Figure 1

(a) Preoperative view of patient at time of presentation. (b) Preoperative mouth opening of the patient = 15 mm with mild deviation of the mandible to the injured (right) side

Medical history including review of systems was nonsignificant. Extraoral clinical examination showed slight asymmetry of the face. Diffuse solitary ill-defined growth was present on the right side of the face at malar region measuring approximately 3 cm × 3 cm in maximum dimensions. Swelling was bony hard in consistency and nontender. There was no palpable depression in the right zygomatic region and there was no evidence of diplopia or infraorbital dysesthesia. Maximum interincisal mouth opening was 15 mm with mild deviation of the mandible to the injured side [Figure 1b]. Protrusive and lateral jaw movements were restricted. On extraoral palpation, no rotary or translatory movements of condyle were perceptible. On intraoral examination, occlusion was found to be satisfactory and no other abnormalities were noticed. The patient was subjected to further investigations.

Water's view [Figure 2] revealed an irregular-shaped radio-opaque mass over the right zygomatic region. There was loss of normal architecture of the coronoid process and zygomatic arch on the right side. The right coronoid process was enlarged, deformed, and in continuation with the bony mass over the right zygomatic region. A computed tomography (CT) scan revealed fused and ankylosed zygomatic arch and coronoid process on the right side. There was presence of an irregular bony growth from the superior portion of the right coronoid process, uniting with the temporal surface of the zygoma which showed bone formation on its medial aspect having homogeneous bony texture [Figures 3a–c]. Zygomatico-coronoid fusion was completed by this mass of bone formed. The other significant finding on CT scan was hypertrophied and malformed right zygomatic arch.

Figure 2

Waters’ view revealed loss of normal architecture of the coronoid process and zygomatic arch on the right side (red circle). Left zygomatic arch is fairly visible

Figure 3

(a-c) Computed tomography showing irregular bony growth from the right coronoid process of the mandible uniting zygomatic arch

Surgical procedure was explained to the patient. Informed consent was taken. The surgery was carried out under general anesthesia after awake nasoendotracheal intubation. Using hemicoronal incision, the lateral rim of the right orbit, anterior aspect of the right infratemporal fossa, and right zygomatic arch were exposed. Having accessed the right zygomatic arch, the presence of ankylotic osseous block affecting the zygomatic arch and the coronoid process of the mandible was revealed. It was found that the enlarged coronoid had fused with the mushroom-shaped bone over the zygoma [Figure 4a]. It measured approximately 2.5 cm × 2 cm × 1.5 cm. As the next stage of the procedure, ostectomy was performed by means of osteotomes and fissure burs removing the ankylotic osseous mass [Figure 4b]. The mass was removed in pieces. Ipsilateral coronoidectomy was performed through same approach. On careful examination, it was noted that there was fibrous ankylosis of the right condyle. There was no bony union between condyle and glenoid fossa. Hence, ipsilateral condylectomy was also performed and a gap of 1.5 cm was created between roof of the glenoid fossa and the mandible [Figure 4c]. Resected condyle was contoured to form zygomatic arch and secured with miniplates. Following this procedure, mouth opening of 40 mm was achieved at the end of surgery [Figure 4d]. The wound was sutured in layers.

Figure 4

(a) Ankylotic bony mass exposed. (b) Resection of ankylotic mass. (c) After the ostectomy, a gap of at least 1.5 cm between the roof of the fossa and the mandible was created. (d) Intraoperative mouth opening achieved: 40 mm

The patient was started on aggressive physiotherapy from the 1st day after surgery. Physiotherapy was painful initially; but the patient managed it well in time. The patient was discharged after 1 week with interincisal opening of 31 mm. In the 1st month, the interincisal opening was stable around 30 mm. Intensive physiotherapy was continued for several months. The unforced mouth opening increased to 35 mm, 2 months after surgery and 40 mm after 6 months of surgery [Figure 5]. Mandibular function was adequate and protrusive and lateral movements of the jaw were restored. The patient was subjected to postoperative investigations which included orthopantomogram and computed tomogram [Figures 6a–c].

Figure 5

Mouth opening after 6 months = 40 mm

Figure 6

(a-c) Computed tomogram taken 1 month after surgery showing level of resection and gap between roof of the glenoid fossa and the mandible and also reconstructed zygomatic arch secured with miniplates

DISCUSSION

TMJ ankylosis is a structural disease that produces functional and esthetic disability in the form of limited mouth opening and facial deformity. This condition is most commonly associated with trauma (13%–100%), local or systemic infection (0%–53%), or systemic diseases, such as ankylosing spondylitis, rheumatoid arthritis, or psoriasis.[36]

TMJ ankylosis may be classified on the basis of location (intra- or extra-articular), type of tissue involved (bony, fibrous, or fibro-osseous), and extent of fusion (complete or incomplete). Ankylosis may be true or false. Any condition that gives rise to an osseous or fibrous adhesion between the surfaces of the TMJ is true ankylosis while false ankylosis results from the conditions not directly related to the joint.[6]

In 1853, enlargement of coronoid process was first reported by Langenbeck. In 1899, fusion between the coronoid process and zygoma was first described by Jacob. The earliest study was done by Brown and Peterson in 1946 who reported three cases of ZCA caused by gunshot wounds. Gridly and Marlette reported cases with infection of the maxilla leading to ZCA. Lindsay et al. treated a fibrous ZCA in 1966 which occurred subsequent to a tumor removal. In 1971, Troyer reported an unusual case of ZCA that occurred as a result of surgery to correct prognathism.[5]

Twelve of sixteen cases were caused by trauma. Among these 12 cases, 9 cases were caused by trauma to the coronoid process and 3 cases were caused by trauma to the zygoma. Cases of direct trauma to the zygoma were first reported by Findlay in 1972. Kellner et al. (1979) and Rikalainen et al. (1981) reported similar cases. However, to be more specific, the etiologic factor in our case was inadequate treatment following trauma to midface. Apart from history and clinical examination, radiographic examination and CT are significant elements in diagnosis and planning treatment in patients in whom TMJ ankylosis is suspected.[6]

The mechanisms by which the ankylosis develops are unclear since heterotopic bone is rarely encountered in the maxillofacial region. Following trauma, infection or surgery, metaplastic changes occur in connective tissue elements that normally do not have osteogenic potential.[3] However, history of trauma and previous surgery of the region and radiographic presence of island of bone between the zygoma and coronoid process leads to heterotopic ossification (HO) as the probable cause of ankylosis in our case. HO is the formation of lamellar bone at sites where bone is not present normally[7] and it occupies the space in soft tissue where it does not normally exist.[8] The HO of muscles, ligaments, and tendons is a potential complication following trauma, surgery, neurological injury, and severe burns.

The patient presented in this paper was diagnosed with posttraumatic, extra-articular ZCA resulting in significant immobilization of the jaw. In retrospect, the sustained trauma would have resulted in the fracture of the right zygomatic arch and possibly the coronoid process of the mandible as well. Unattended fracture resulted consequently in a union, initially fibrotic, then osseous between the zygomatic arch and coronoid process of the mandible. It was surprising that the patient did not manifest any deformation of the curvature of the right zygomatic arch, which may have been due to the deposition of the bony tissue at the fracture site and thus compensate for posttraumatic bone displacement.

The treatment is obviously surgical.[5] Lindsay et al. stated that conservative treatment is unsuccessful.[9] This included forceful opening of the jaws, with the patient under general anesthesia.[10] Most authors agree that the most successful treatment for this condition is a coronoidectomy. However, there is a diversity of opinion regarding coronoidectomy, whether it should be performed intraorally or extraorally.[5]

Considering the extent and amount of ankylotic bony mass and restricted mouth opening in our patient, the hemicoronal approach seemed to be the best choice. Access to the affected site was excellent and sufficient removal of ankylotic osseous bony mass was made possible. Early postoperative mouth opening exercises, strict follow-up, and even forceful opening are necessary to overcome postoperative adhesions that may develop.[3]

CONCLUSION

The unique feature of our case is that the fusion between coronoid process and zygoma was by an island of bone which could be a result of HO secondary to inadequate treatment of previous trauma. Extraoral ostectomy of the ankylotic osseous mass followed by aggressive physiotherapy produced good long-term functional result.

To conclude, ZCA is a very rare condition. Oral and maxillofacial surgeons should have a thorough knowledge of the clinical and radiographic features of this rare entity. Furthermore, in cases of ankylosis, instead of concentrating only on the TMJ, the coronoid process should also be assessed properly. Furthermore, to prevent recurrence, postoperative physiotherapy is required.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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Conflicts of interest

There are no conflicts of interest.