Ankylosis is a condition in which movement is restricted because of fusion of the intra articular joint components. Intra Articular ankylosis may be bony or fibrous. In bony ankylosis, the condyle or ramus of the jaw is attached to the temporal or zygomatic bone of the cranium. In fibrous ankylosis, a soft tissue (fibrous) union of joint components occurs. Most temporomandibular joint ankylosis cases are caused by mandibular trauma or infection. Severe arthritis, therapeutic radiation exposure to the joint (cancer treatment), or genetic predisposition may give rise to ankylosing spondylitis.
In a webinar conducted by MedPiper Technologies and Journomed in association with AOMSI on Oral & Maxillofacial Surgical Care in Children, the speakers Dr. J Naveen Kumar and Dr. R Rammohankumar extensively discussed how mandibular (lower jaw) fractures in children can lead to Temporomandibular joint (TMJ) Ankylosis. The event was moderated by Dr. P Senthil Murugan, Associate Professor at Saveetha Dental College and Hospital, Chennai. Dr. S Jimson, Hon. State Secretary of AOMSI, TN & Puducherry Branch, coordinated the event.
Around 75% of Dental Traumas lead to TMJ ankylosis. In jawline fractures, the kinetic energy from the impact of the fall or the trauma gets transmitted to the end joints of the face. Since the articulating surface of a child’s condyle is thin, any impact force can shatter it into multiple pieces. There are also more blood vessels surrounding a child’s condyle as compared to an adult. Hence there is a higher chance that the shattered condyle bits can rupture these blood vessels and cause bleeding from the marrow.
A clot is formed to stop the bleeding. The clot then forms a bone due to the high growth potential of the child and this bone will fuse with the temporal fossa of the cranial base area thus causing TMJ ankylosis.
A child suffering from TMJ ankylosis may experience problems such as
- Difficulty in opening the mouth
- Inability to chew and swallow
- Poor Oral Hygiene leading to Rampant Caries, Generalised Gingivitis and Periodontal Diseases
- Speech difficulties (corrected by removing the teeth)
- Irregular and asymmetrical growth of the mandible causing breathing difficulties (obstructive sleep apnea)
Sometimes the ankylosis can be bilateral in nature where there is complete hypoplasia or the mandible. There is no proper development of the chin and there is no distinct chin neck angle causing severe airway obstruction and heightened breathing troubles.
Extensive surgical interventions such as condylectomy, gap arthroplasty or interpositional arthroplasty help in managing TMJ ankylosis. The fused condyle is removed by a procedure called condylectomy. Gap arthroplasty is a procedure where a gap is made between the fused articulating surfaces i.e between the condyle and the cranial base. To prevent re-ankylosing, the gap has to be maintained and is hence filled with interpositional materials. Some of the preferred interpositional materials include temporal fascia, abdominal derma, costochondral cartilage or rib graft. These materials are chosen as they have the ability to grow as the child grows and can thus prevent asymmetrical growth of the jaw. The gap can also be filled with silicone.
Aggressive physiotherapy is required once the surgeries are done. Immobilisation of the jaw can lead to re-ankylosing. Constantly opening and closing the mouth will ensure that there is no bone to bone contact and prevent re-ankylosis.
Prosthetics are used to treat TMJ ankylosis in adults (in whom the growth potential is complete) via alloplastic joint reconstruction and it helps to restore the morphology of the jaw. However these prosthetics cannot be used in children as they still have growth potential. If prosthetics are used in children, the other side of the jaw will continue to grow whereas the reconstructed side will not grow, which leads to an asymmetrical jaw.
When the ankylosing joint is removed, there will be a shortening of the ramus which can also give rise to asymmetry or the jaw. This asymmetry has to be corrected not just for cosmetic reasons but to also prevent the backward growth of the jaw that can crush the pharynx and cause breathing problems. The asymmetry is corrected by a procedure called distraction osteogenesis where a shorter bone is made into a longer one using a device called a distractor.
Either a uniplanar biplanar, extraoral or intraoral distractor is fixed onto the remaining shortened ramus. The attender can then activate these distractors which makes the mandible grow forwards and downwards to attain symmetry. The procedure also helps to restore breathing by relieving the pressure on the pharynx. Sometimes the distraction is done even before removing the ankylotic fused joint (primary distraction) as the ankylotic mass serves as the anchorage point for the jaw distraction.
“Children are not small adults and they have a completely different anatomy as compared to adults,” says Dr. J Naveen Kumar. Hence it is important to understand why different oral and maxillofacial surgical approaches should be used for managing ankylosis in children.