**2. Etiology and pathogenesis of TMJ ankylosis**

Trauma to the TMJ has been cited as the most common underlying reason responsible for ankylosis; however, local infections (e.g. otitis media) and systemic disorders (e.g. rheumatoid arthritis) also can also cause unilateral or bilateral TMJ ankylosis in some cases [4-7]. By improving the immediate management protocol of condylar fracture and proper application of antibiotics to fully address ear infections, the prevalence of ankylosis has decreased significantly in recent years. In addition to the common etiologic factors of TMJ condylar ankylosis, some affected infants with unknown etiological factors have been reported in the literature (Figure 1 a-c) [8].

The pathogenesis of the TMJ ankylosis is described by a sequence of events. The increased intra-articular vascular supply at the traumatized joint develops fibrosis and ultimately

2. **Etiology and pathogenesis of TMJ ankylosis**

**COMPREHENSIVE MANAGEMENT OF TEMPOROMANDIBULAR**

Temporomandibular joint (TMJ) ankylosis is one of the most challenging TMJ disorders that can negatively affect oral related daily functions like mastication, speech and hygiene (1,2). The accepted definition of ankylosis is the bony or fibrous tissue fusion between articular surfaces including the meniscus, glenoid fossa and condylar heads (3). Consequently, jaw functions like the maximal incisal opening (MIO) and lateral excursive movements progressively decrease. This chapter describes the most important issues of early and late management of TMJ ankylosis in both children and adults.

Trauma to the TMJ has been cited as the most common underlying reason responsible for ankylosis; however, local infections (e.g. otitis media) and systemic disorders (e.g. rheumatoid arthritis) also can also cause unilateral or bilateral TMJ ankylosis in some cases (4‐7). By improving the immediate management protocol of condylar fracture and proper application of antibiotics to fully address ear infections, the prevalence of ankylosis has decreased significantly in recent years. In addition to the common etiologic factors of TMJ condylar ankylosis, some affected infants with unknown etiological

**JOINT ANKYLOSIS: STATE OF THE ART**

Hossein Behnia, Azita Tehranchi and Farnaz Younessian

Additional information is available at the end of the chapter

1. **Introduction**

**Figure 1. A 5‐year‐old girl with bilateral condylar ankylosis of unknown etiology (no history of trauma or infection). a) Extraoral facial photograph of the patient demonstrate the upper occlusal canting with the help of a tongue depressor, b) Intraoral photograph shows midline deviation, Figure 1.** A 5-year-old girl with bilateral condylar ankylosis of unknown etiology (no history of trauma or infection). a) Extraoral facial photograph of the patient demonstrate the upper occlusal canting with the help of a tongue depressor, b) Intraoral photograph shows midline deviation, mandibular shift and increased overjet of the patient, c) three dimen‐ sional cone beam computer reconstruction of the patient demonstrates the facial asymmetry.

excessive localized bone formation [4]. Most of the animal studies consider intra-capsular hematoma as the main underlying reason for development of the ankylotic mass following trauma. Observed hemorrhage contains different cellular pathways activated by bone morphogenic proteins (BMPs) and tumoral growth factors (TGFs) [9]. However, a study on human subjects, revealed that hematoma in the joint space does not always result in bony ankylosis [2]. This excessive bone mass does not have a neoplastic nature, but has the potential of continual growth [10]. The presence of abnormal bony mass may restrict mandibular movement, which subsequently may lead in loss of the functional matrix of bone and muscle interaction, and consequently result in growth failure [11]. Inadequately treated or excessive treatment of condylar fractures may lead to growth retardation or growth excess, respectively [3]. Therefore, the best treatment steps for post-traumatic ankylosis and resulting growth abnormality is prevention. 1 **mandibular shift and increased overjet of the patient, c) three dimensional cone beam computer reconstruction of the patient demonstrates the facial asymmetry.** The pathogenesis of the TMJ ankylosis is described by a sequence of events. The increased intra‐ articular vascular supply at the traumatized joint develops fibrosis and ultimately excessive localized bone formation (4). Most of the animal studies consider intra‐capsular hematoma as the main
