Secondary Traumatic TMJ Reconstruction

Ankylosis

Posttraumatic ankylosis of the TMJ injury is an uncommon complication of condylar injury and is of particular concern in pediatric cases where significant growth disturbances may result. This includes facial asymmetry, retrognathism, and secondary midface growth deficiency. In the adult patient, it may present as trismus with resultant compromised mastication, speech, oral hygiene, and even psychosocial distress. This complication usually results from comminuted intracapsular injuries, particularly when the articular disk is disrupted. It has also been suggested that concomitant anterior mandibular fractures, which allow posterior facial widening and consequent lateral displacement of fractured condyles, also increase the risk for this complication. Treatment can depend on the severity of the condition with various treatment modalities at the clinician's disposal, including gap arthroplasty, costochondral grafting, and total joint replacement. The growing patient offers additional reconstructive challenges and often requires further corrective surgeries consequential of dynamic changes in the growing patient. Complete bony TMJ ankylosis has been typically managed with gap arthroplasty, autogenous tissue graft or alloplastic arthroplasty. Autogenous grafting techniques usually require a period of immobilization postoperatively to allow adequate healing and limit the risk of graft failure resulting in mandibular functional delay. The lack of early mobilization and lack of soft tissue interface can risk reankylosis and should this occur, then total alloplastic reconstruction may be considered. In the growing patient, ankylosis of the TMJ may lead to asymmetrical mandibular growth resulting in height reduction of the affected ramus and subsequent facial asymmetry with chin deviation to the affected side, due to normal growth of the opposite side and impaired growth of the affected side. Compensatory occlusal disturbances may also occur such as overeruption and tipping of teeth to help reestablish functional occlusion. TMJ ankylosis in growing subjects has traditionally been managed by autogenous grafting, with the costochondral grafts as the most widely used method for these TMJ reconstructions. The rationale for autologous grafting is to maintain growth potential but growth and resorption can be unpredictable and other complications such as ankylosis have been reported.

Sawhney classified four types of pathological changes in the ankylosed TMJ. Type 1 describes flattening of the condylar head with surrounding dense fibrous adhesions making movement impossible. Type 2 includes a flattened or deformed condylar head, with close proximity to the articular surfaces, and a limited bony fusion of the outer, anterior or posterior surface. Type 3 includes a bony block bridging across the ramus and the zygomatic arch, with the displaced articular head fused to the medial side of the ramus, or the presence of an atrophic condylar head. Type 4 presents as a large bony block that completely replaces the usual joint architecture.

Condylar Malunion/Malposition With Malocclusion and/or Facial Asymmetry

Loss of posterior mandibular vertical dimension due to traumatic injury can cause occlusal discrepancies as either an anterior open-bite where bilateral mandibular height is lost, or premature contact of the posterior teeth with contralateral open-bite where there is unilateral vertical height loss. Fig. 3.10.2 illustrates left condylar hypoplasia and the resultant loss of left vertical height in a young patient following an old traumatic fracture dislocation injury. In the absence of successful primary trauma reconstructive surgery or other management to help reestablish normal vertical height and correct occlusal discrepancies, then joint reconstruction (autogenous or alloplastic) or osteotomy may be considered. In the growing patient, loss of vertical height on the affected side may either be due to ankylosis and the resultant hypomobility or from direct injury to the condylar cartilaginous cap. It has been widely accepted for the growing patient where preservation of growth potential is desired, autogenous grafting such as the costochondral graft, is preferred over alloplastic TMJ reconstructive solutions. However, very good results using alloplastic devices in growing patients are emerging, with maintenance of facial symmetry in both unilateral and bilateral cases.

Degenerative Joint Disease

Traumatic injury to the TMJ, whether direct or indirect, can lead to osteoarthritic changes within the joint. Posttrauma joint effusion is well known in the orthopedic literature and has frequently been observed in posttraumatic imaging of the TMJ by magnetic resonance imaging (MRI), whilst other studies have shown arthroscopic evidence of TMJ articular damage following mandibular fracture injuries. The pro­inflammatory cytokine interleukin-6 (IL-6) has been shown to play a key role in the pathogenesis of arthritis and has been found in higher concentrations in TMJs with internal derangement and osteoarthritis when compared to TMJs without joint effusion. Nogami et al. found a correlation between MR evidence of joint effusion and concentration of IL-6 in washed-out synovial fluid samples collected from patients with mandibular condyle fractures. TMJ arthritis is one of the most common diseases affecting this joint and has a variety of other etiologies besides trauma, including inflammatory, infectious, metabolic, degenerative osteoarthritis, and systemic arthritides. Therefore, where preexisting disease is present, then certainly a traumatic insult can exacerbate the primary disease state. Symptoms depend on disease progression but patients may typically present with constant preauricular pain, with or without radiation and crepitus. Other symptoms may include TMJ locking, clicking, popping, and mandibular deviation on opening. Although a majority of patients earlier in the disease process will respond to nonsurgical treatment modalities or limited surgical intervention, when the mandibular condyle is extensively damaged, degenerated or lost, replacement with either autogenous graft or alloplastic implant is an acceptable approach to achieve optimal functional and symptomatic improvement.