Extraarticular joint ankylosis: a rare presentation
- 1 Dental and Oral Surgery Unit-1, Christian Medical College, Vellore, Tamil Nadu, India
- 2 Dental Surgery Unit 1, Christian Medical College, Vellore, Tamil Nadu, India
- Correspondence to Dr Saurabh Kumar; dr.s.kumar.bds@gmail.com
Abstract
Pseudoankylosis is a rare condition that causes inability to open the mouth due to condition related to outside of the temporomandibular joint. Most literature refers to this hypomobility disorder, a result of fusion of the zygomatic bone to the coronoid process, and very rarely is insidious coronoid hyperplasia causing mechanical interference with the posterior maxilla has been reported. We present a case of a 45-year-old woman, who presented with coronoid malformation and overgrowth resulting in progressive decrease in mouth opening. She was managed with coronoidectomy, following which good mouth opening was obtained. In this paper we discuss about the diagnosis and management of this rare disorder.
Background
True ankylosis results from any condition that induces bony adhesions between the articulating surfaces, for example, from infection, trauma or arthritis. Pseudoankylosis on the other hand results in restricted mandibular mobility from a pathologic condition outside the temporomandibular joint (TMJ), most importantly from muscular, osseous, neurologic or psychiatric disorders.1 The proper mechanism explaining the development of extraarticular ankylosis is unclear. It may result from metaplastic changes in connective tissue elements that do not ordinarily have osteogenic potential, following trauma, infection or surgery. Extrinsic joint conditions causing mandibular hypomobility is very rare. Most often the cause for extrajoint hypomobility disorder is trauma, seen in 70% of the reported cases.2 Trauma results in fusion of the coronoid process with the fractured zygomatic bone hence resulting in subsequent trismus. Coronoid malformation presenting as an overgrowth resulting in mechanical interference with the zygomatic process of maxilla is rarely reported. The extent of restricted mandibular mobility in TMJ pseudoankylosis varies considerably, ranging from partial to complete restriction.3 Diagnosis of patients presenting with restricted mouth opening is always challenging. Multiple factors in the orofacial region is responsible for this abnormality. While a true TMJ ankylosis is always associated with characteristic clinical and radiographic findings, diagnosis of pseudoankylosis or the extraarticular joint ankylosis has always remained difficult due to its masquerading features with other benign and malignant orofacial conditions. Treatment consist of surgical management along with aggressive jaw physiotherapy to prevent relapse.4
Case presentation
A 45-year-old woman, reported to oral and maxillofacial clinic at Christian Medical College and Hospital, Vellore, with a chief compliant of pain over the left side of the face since 2–3 months with progressive decrease in mouth opening since 15 years. The patient had no significant medical history or history of any previous trauma. Interincisal mouth opening was recorded as 13 mm (figure 1). Orthopantomogram (OPG) of the patient showed a radiopaque mass over the left side coronoid process suggestive of coronoid hyperplasia (figure 2). TMJ tomogram open and closed mouth showed limited movement of condyle in the left TMJ (figures 3 and 4). CT scan also revealed coronoid process impingement into the posterior aspect of maxilla (figures 5 and 6). Based on the patient’s clinical presentation and radiographic characteristics a provisionally diagnosis of left side coronoid hyperplasia was made. Coronoidectomy and removal of the hyperplastic coronoid were planned under general anaesthesia. Extraoral left submandibular approach was used to approach the coronoid process and osteotomy of the hyperplastic coronoid stump was done (figures 7 and 8). Histopathology of excisional bone biopsy revealed osteosclerosis with focal osteonecrosis of the specimen. On 2-year follow-up the patient presented with satisfactory dental occlusion with maximum mouth opening of 34 mm and inconspicuous extraoral surgical scar with no radiographic findings of any recurrence on OPG (figures 9 and 10).
13 mm interincisal mouth opening at the time of presentation.
Orthopantomogram of the patient showed a radiopaque mass over the left side coronoid process.
Temporomandibular joint (TMJ) tomogram showing normal condylar movement in the right side TMJ during opening the mouth.
Temporomandibular joint (TMJ) tomogram showing restricted condylar movement in the left side TMJ during opening the mouth.
Axial CT showing left sided coronoid mass abutting the posterior wall of the maxilla.
CT 3D reconstruction image showing coronoid elongation.
Surgical access using submandibular incision, with coronoidectomy defect post resection.
Coronoidectomy specimen with attached part of temporalis muscle.
Adequate mouth opening at 2-year follow-up.
Orthopantomogram at 2-year follow-up showing absence of coronoid regeneration and the osteotomy defect at the left coronoid region.
Investigations
Investigations included an OPG, TMJ tomogram open and closed mouth including CT scan of facial structure including TMJ.
Differential diagnosis
Trismus is a result of varied benign and malignant condition. Since the patient has a gradual reduction of mouth opening and the disease was not an acute development, malignancy was ruled out. TMJ ankylosis or myositis ossificans were other differentials. Radiographic imaging presented as a coronoid pathology suggestive of extraarticular joint ankylosis.
Treatment
Surgical removal of the left side coronoid was considered to release the pseudoankylosis of the hypertrophic coronoid with the posterior maxilla.
Outcome and follow-up
Two-year follow-up revealed satisfactory mouth opening with stable occlusion.
Discussion
Pseudoankylosis of the TMJ is much less frequent than true form of ankylosis. It is characterised by mandibular hypomobility caused by pathology extrinsic to the joint.4 Multiple causes for extra-joint ankylosis have been reported in the literature, of which trauma, infection and iatrogenic cause have been the most commonly reported.5 Progress of bony union resulting in fusion of the sigmoid notch to the zygomatic arch and skull base has been reported in advanced cases of true ankylosis.6 7 Often cases with true ankylosis present with concomitant coronoid elongation and hyperactive temporalis. This need to be corrected by coronoidectomy procedure at the time of ankylosis surgery. Coronoidectomy has been proposed by kaban as an important aspect in ankylosis management. Coronoid elongation in cases with true ankylosis has been mainly attributed to the surrounding soft tissue structures which are directly and indirectly involved in the process of mastication, mainly the temporalis, the suprahyoid muscles, masseter, TMJ and the buccal submucosal tissue.8
Pseudoankylosis is clinically characterised by limited mandibular movement with no pain. Patients often present with minimal clinical symptoms and pose a diagnostic challenge. Various pathologic causes for coronoid enlargement include benign bony pathologies mainly osteochondroma, osteoma, exostosis or developmental anomalies as seen in Jacobs disease or some form of mucopolysaccharide disorder.9 OPG can identify the presence of elongated coronoids, condyle mass or true form of TMJ ankylosis. However, a CT scan is usually ideal as it can detect bony fusion, thus differentiating pseudoankylosis from true ankylosis.2 In our case CT showed a left side coronoid mass which was abutting to the posterior aspect of maxilla extending to the zygomatic process. Coronoid hyperplasia causing mechanical interference to the mobility of the jaw can be effectively treated with coronoidectomy.5 The decision whether to perform surgical intervention in pseudoankylosis depends on patient-related factors such as chewing problems, the extent of mouth opening and the impact on psychosocial status. Also, the duration of the restricted mobility plays a role in surgical planning.3 In our case coronoidectomy was done which showed good results. Pseudoankylosis may be approached surgically by intra- or extraoral approaches for performing coronoidectomy in order to restore jaw movements. Extraoral approaches include hemicoronal incision, submandibular approaches and preauricular incision. The intraoral approach requires an incision over the external oblique ridge to reach the coronoid process and perform a coronoidectomy with resection of the ankylotic block segment.10 The decision regarding the type of surgical technique and surgical approach should depend on the visibility, risk of complications and cosmetic patient demands. Consequently, the surgical approach to remove an elongated coronoid process should be case specific and depends on the extent of the deformity.3 In our case coronoidectomy gave good results and excellent mouth opening. Management of TMJ pseudoankylosis involves relief of the reduced mouth opening, restoration of chewing ability and correction of the related psychosocial effects.3 The immediate postoperative period is the most critical time for successful relief from jaw hypomobility. Coronoidectomy involves surgical removal of the coronoid process from the mandibular ramus and is used as treatment of choice. The stability of the outcome, however, is considered questionable because of the risk of reattachment of the coronoid process is always there, and the patient needs a long term close follow-up.11 However, coronoidectomy in combination with prolonged postoperative physiotherapy has demonstrated satisfying long-term results with substantial improvement in mouth opening.10 12 13 The overall outcome for the surgery is significantly improved by adjunctive post-surgery physiotherapy.14 15 In our case patient was started on mouth opening exercises immediate postoperatively which yielded good results. Wedge, spatula and Therabite appliance have all shown good results.16 17 Immediate initiation of physiotherapy multiple times including jaw opening and translational movements in various directions must be encouraged for effective result.
Learning points
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Pseudoankylosis is difficult to diagnose and proper protocol for management of this condition henceforth warranted.
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Early diagnosis and intervention are key in the management, as delay in surgery could result in progression of the condition bilaterally.
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Coronoidectomy has been found to be a good treatment option for this condition. Surgical intervention with active physiotherapy yields good results.
Ethics statements
Patient consent for publication
Footnotes
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Contributors Dr SK, Dr APC were involved in the clinical management as well as inception of the paper. Dr SK was involved in the literature research and writeup.
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Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
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Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
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Competing interests None declared.
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Provenance and peer review Not commissioned; externally peer reviewed.
- © BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.
References
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