Ankylosis in general means immobility of a joint due to any reason, TMJ ankylosis is immobility of the Mandible due to reasons such as trauma, infection, disease, failed surgery, Rheumatoid arthritis and most common being congenital. Temporomandibular Joint is a complex structure that helps in the movement of the mandible with the help of Ligaments and muscles and any deformity in it can directly affect the growth of the mandible and also occlusion.
Types of TMJ Ankylosis:
- False Ankylosis: Ankylosis is caused due to any pathological conditions, mechanical obstruction or extra-articular fibrosis leading to limited joint movement. With the etiology being caused due to extra-articular fibrosis it is termed as False.
- True Ankylosis: Ankylosis is caused due to intra-auricular fibrous or bony fusion of joint structures. There is a loss of normal bony architecture when seen in a radiograph. The causes of True Ankylosis are caused due to enlargement of the coronoid process, depressed fracture of the zygomatic arch or scarring from surgery, irradiation or infection of the TMJ.
- Fibrous Ankylosis: Fibrous growth is seen between the condyle and fossa leading to loss of discal space due to loss of disc.
- Bony Ankylosis: It is seen when callus is formed between the articular surface and condyle leading to synostosis.
- Unilateral and Bilateral Ankylosis
Classification of TMJ Ankylosis:
Source: Textbook of Oral and Maxillofacial Surgery, S M Balaji
I. Classification of Kazanjian 1938:
- True Ankylosis – Intra-articular ankylosis
- False Ankylosis – Extra-articular ankylosis
II. False Ankylosis – Miller et al, 1975
- Myogenic: Caused due to fibrosis within the muscles mostly due to intramuscular hematoma
- Neurogenic: Caused due to lesion or any accident to the CNS leading to decreased activity of the masticatory muscles.
- Psychogenic: Psychological issues leading to Ankylosis known as hysterical trismus.
- Bone impingement: Caused due to any abnormalities of the bone surrounding the joint
- Fibrous adhesion: Formation of any scar tissue due to any external trauma such as heat or radiation therapy.
III. Histologic variations:
- Fibrous – short or long
- Bony – intracapsular or extracapsular
IV. Raveh et al classification
- Class I: Ankylotic bone tissue limited to the condylar process and articular fossa
- Class II: The bone extends out of the fossa involving the medial aspect of the base of skull to the carotid- jugular vessel
- Class III: Extension and penetration into the middle cranial fossa
- Class IV: Combination of Class II and III
V: Topazian, 1966
- Type I: Only the condyle is involved
- Type II: Intermediate
- Type III: Entirecondyle, sigmoid notch and the coronoid process is involved
VI: Shashi Aggarwal, Manorama Berry, 1990 – Based on Condyle
- Type I: Condyle can be identified but disproportionate – partially resorbed, flattened, irregular sclerosed and is medially angulated. The most common cause is Trauma. Moderate new bone formation is seen extending from the neck of the condyle or lateral superior aspect of the ramus to the squamous temporal bone or zygomatic arch. The articular fossa is usually sclerosed and irregular, shallow or deep with sclerosis extending to the temporal bone as well.
- Type II: The Condyle or Articular fossa cannot be identified as the joint architecture is completely disrupted. There is a large mass of new bone from the base of the skull extending to the thickened ramus with the new bone usually seen in a funnel shape.
VII: Bony Ankylosis (TMJ Ankylosis), Sawhney 1986
- Type I: Deformed Condylar head which is flattened and is in close approximation to the upper joint space. Dense fibrous adhesion is seen intra-auricularly. Fibrosis of the joint leads to restricted movements.
- Type II: Condyle is flattened and is in close approximation to the glenoid fossa, a bony fusion of the outer aspect of the articular surface which is anteriorly or posteriorly restricted to a small area.
- Type III: The ramus of the mandible is bridged to the ramus due to a medially displaced fracture dislocating the condyle. The condylar head is atrophic which is either free or fused to the medial aspect of the superior portion of the ramus.
- Type IV: Mandibular Ramus is bridged to the Zygomatic arch with a wider bony block, the joint space is filled with bone replacing the joint completely with it.
The classifications have mentioned almost all the causes of TMJ ankylosis which are divided into True and False types based on the formation of fibrous, fibro-osseous and osseous causes. Let us discuss the major causes of TMJ Ankylosis in detail.
Trauma: Any Physical or Thermal trauma to the TMJ join leads to calcification or fibrous ankylosis. Trauma during Delivery using Forceps can lead to fibrous ankylosis due to bony fusion of the neck of the condyle to the zygomatic arch. Trauma leads to pooling of blood in the joint space which when left untreated or immobile leads to calcification of the hematoma.
Infection: It comes under True type of Ankylosis caused to infection Intra-auricularly. The infection leads to reduced mobility, destruction of the articular surface with the normal physiological process being affected. Due to the destruction of the normal movements and lack of movement it leads to True Ankylosis of the joint.
Inflammation: Inflammatory Arthritis (Rheumatoid) leads to ankylosis in less than 7% of the cases. The causes of Inflammation of the TMJ joint include Stills disease or juvenile rheumatoid arthritis, Marie-Strumpell disease (ankylosis spondylitis), psoriatic arthritis, fibrodysplasia ossificans progressiva, and osteoarthritis.
Following Arthroplasty: TMJ Ankylosis is seen in patients following Mandibular orthognathic procedures or TMJ arthroplasty. Following disc repair there can be adhesion between the disc and articular eminence. In case of lack of physiotherapy postoperatively can lead to bony ankylosis after discectomy procedure.
Neoplasia: Due to any tumor of the condyle or metastatic lesion or chondromastosis of the TMJ leading to TMJ Ankylosis.
Congenital: Bony fusion of the maxilla and mandible can be seen in rare conditions.
Diagnosis of TMJ Ankylosis:
There are certain clinical and radiological features that help in diagnosing TMJ Ankylosis with the main feature being restricted mouth opening which depends on whether the Ankylosis is Unilateral or Bilateral.
Clinical Features and Examination:
Mouth Opening and Mandibular movement: It differs based on the type of Ankylosis – Fibrous Ankylosis there will be reduced jaw motion which is less than 15mm, Deviation of the mandible is seen in Unilateral ankylosis towards the side of ankylosis.
Mandibular deficiency: When there is ankylosis from an early age there will be reduced growth of mandible due to reduced ramal height, micrognathia, birds face appearance is seen in bilateral ankylosis. Antegonial notch is prominent due to the pull of the muscles attached to the mandible. The facial deformity is due to reduced epiphyseal growth as a result of the absence of stimulation from the functional matrix.
Facial Asymmetry: The chin is deviated towards the ankylosed side along with micrognathia in case of unilateral ankylosis There is a deficiency of body of mandible on the normal side. Along with asymmetry, there will be malocclusion, caries, halitosis and hypertrophic suprahyoid musculature.
Clinical features of Unilateral Ankylosis:
- Facial Asymmetry
- Reduced growth of mandible on Ankylosed side
- The Chin and mandible deviates towards the affected side
- The unaffected side is elongated and flat due to normal growth as compared to the affected side
- Restricted mouth opening
- Posterior crossbite on the affected side with Class II malocclusion
Clinical features of Bilateral Ankylosis:
- Class II malocclusion
- Restricted mouth opening
- Micrognathic mandible but symmetrical
- Bird face deformity is seen
- Impacted teeth due to micrognathic mandible
- Anterior open bite is seen with protrusive maxillary incissors
Radiographic Examination of TMJ Ankylosis:
Arthrography helps in identifying fibrous ankylosis but not useful in bony ankylosis
A Panoramic radiograph is required for initial screening
Plain film radiograph helps in visualizing the joint space (reduction or complete obliteration)
Temporomandibular joint tomography – coronal and sagittal sections help in localizing and determining the amount of ankylosis. For checking condyle, joint space integrity, location of osseous union tomographic sections of the entire joint space are required.
CT of TMJ is useful in identifying spicules of bone which bridge the joint space and cannot be identified in other diagnostic approaches. This gives the best detail regarding the medical extension of the ankylotic mass. The posterior and medial aspects can be viewed with the CT effectively.
Treatment of TMJ Ankylosis:
There are many factors to be considered for the Treatment plan in TMJ ankylosis like age, unilateral or bilateral, fibrous or bony type, the extent of it, patient requirements (Functional or aesthetic).
Treatment in Children below 5 Years of Age: These children are more susceptible to deformities and surgical consideration should be done to improve the mandibular function and also to achieve normal growth and development. As there is growth the ankylosed joint needs to be removed and reconstructed with a graft that is capable of active growth along with other surrounding structures. A Rib or Costochondral graft has intrinsic growth potential, the natural contour of the rib matches the condylar anatomy.
In adult’s, removal of the Ankylosed portion, both bony and fibrous parts and reconstruction of the joint to facilitate movement is necessary as there is no growth.
Management of TMJ Ankylosis by Kaban:
- Resection of the fibrous or bony aggressively
- Coronoidectomy on the affected side (Unilateral Ankylosis)
- Contralateral Coronoidectomy (Intraoral approach) if it is less than 35mm
- Reconstruction of ramus with a costochondral graft
- The lining of the TMJ with temporalis fascia
- Early mobilization and aggressive physiotherapy
- Rigid fixation
Temporalis muscle flap is most commonly used with Al Kayat-Bramley incision. It has a temporalis extension allowing elevation of a temporalis fascia flap for interposition. Other incisions are periauricular and submandibular incisions (Extraoral) through which the joint is accessed after exposing the temporalis fascia, the zygomatic arch is reached. The periosteum is incised over the arch by giving an incision over the lateral capsule. After reaching the arch – Gap Arthroplasty or Interpositional arthroplasty is done. The various interpositional materials are Autogenous tissue grafts – Muscles (temporalis), Skin, Fat, Fascia lata, dermis, cartilage.
Alloplastic materials – Tantalum, Vitalium, Acrylic, Teflon, Silicone sheeting and Silicon blocks are used.