Surgical Reconstruction of the Temporomandibular Joint

*Raja Kummoona*

### **Abstract**

This chapter provides a comprehensive overview of the temporomandibular joint (TMJ), including its embryonic development, anatomy, and physiology. It also discusses techniques for management and reconstruction in TMJ disorders, such as TMJ ankylosis (in children and adults), first arch syndromes, and chronic and acute TMJ dislocation and subluxation.

**Keywords:** temporomandibular joint (TMJ), ankylosis, dislocation, subluxation, chondro-osseous graft

## **1. Introduction**

In 1962, Melvin Moss introduced the functional matrix theory, which proposed that the growth of the face is due to functional demand of the periosteal matrix of the facial skeleton. In 1771, John Hunter was the first to nominate the condyle as the primary growth center of the facial skeleton in his book *The Natural History of the Human Teeth* [1]. Moss's theory was more accepted for many years, but we believe the true nature of the growth of the facial skeleton lies within a combination of both theories [2].

### **2. Embryonic development of the TMJ**

Much research has been carried out to understand the formation and development of the mandible and TMJ. The mandible develops from the first pharyngeal arch, which is formed from the neural crest that originates in the mid and hind brain of neural folds. The TMJ develops from mesenchymal condensation of cells, these cells separating between development of squamous portion of temporal bone from condylar cartilage which form the dorsal surface of developing condyle. The early movements of these cells to form the primary TMJ occur at embryonic age 4 months.

Three phases of TMJ development have been reported. The first phase is called the blastemic stage, which occurs during weeks 7–8 of embryonic development. Organization of the condyle, articular disc, and capsule begin at this stage. The second phase is the cavitation stage, during which the inferior joint cavity begins to form at embryonic age 9–11 weeks. This stage involves initial formation of the inferior joint cavity (week 9) and the start of condyle chondrogenesis (week 11). Organization of the superior joint cavity also begins in week 11. The third phase is the maturation stage (after 12 weeks of embryonic development).

The two slits of the joint cavities and the intervening disc form at 12 weeks of embryonic life and the mesenchyme around the joint forms the capsule and the synovial fluid [3].

## **3. Anatomy and physiology of the TMJ**

The TMJ is a synovial joint, unique among all other human body joints because it is the only mobile joint of the craniomandibular part where the mandible articulates with the skull base. It is a highly specialized joint consisting of two compartments. The articular part is covered by fibrocartilage, while other joints are covered by hyaline cartilage. The jaw bones that articulate with it carry teeth and its work is synchronized on both sides like that of the eyes. The TMJ allows for more than 2000 hinge and sliding movements per day in both active masticatory and passive movements like talking, swallowing, and yawning. It is one of the most active joints in the human body.

The ligaments of the TMJ are strong and tough surrounding the condyle and glenoid fossa. There are two types: primary ligaments (temporomandibular ligaments) consisting of outer oblique and inner horizontal ligaments, and minor ligaments (styloid-mandibular and sphenoid-mandibular ligaments) that work as supportive tissue to the capsule. Other accessory ligaments define the border movements of the TMJ.

The disc or meniscus consisted from 4 parts anterior band attached to upper fibers of lateral pterygoid muscle and the lower part of the lateral pterygoid of strong muscle fibers were attached to condylar fossa. The intermediate zone is the area between the anterior and posterior bands, which are positioned normally on the head of the condyle in a closed mouth.

The posterior part of the disc is an elastic recoil fiber attached to the posterior part of the capsule. When the condyle moves forward the posterior band moves with it. Any disorganization between the two parts of the muscle fibers and failure of the posterior band to move with the condyle can cause internal derangements and clicking in the jaw.

TMJ function is controlled by a complex series of reflexes for muscular movement of mastication.

The TMJ consist of two compartments separated by the meniscus: the superior compartment and the inferior compartment. The synovial joint is located in front of the auditory meatus.

Condylar movements are unique. The condyle can move, swing, and rotate within the glenoid fossa, but its movements are limited by ligaments and surrounding muscles.

Synovial lining of the capsule form Ville in both upper and lower joint cavity to secrete fluid for lubrication and the synovial membrane provide sera-mucinous fluid for lubrication and protein for nourishment of the fibro-cartilage part of the joint.

One of the most important functions of synovial fluid that in sudden load exerted on the TMJ, lubrication occurred by squeeze film, sufficiently viscus to be squeezed slowly to persist the long enough to support the load excreted in a short time under sustained high load. The nature of lubrication was a boundary rubbing take place

between the layers of large molecules absorbed in the cartilage surface and failure of lubrication causes great damages to cartilaginous part of the TMJ [3].
