Brett A. Miles
INTRODUCTION
The temporomandibular joint (TMJ) is unique among the joints of the human skeleton (Fig. 15.1). It is a critical component of the craniomandibular articulation and functions quite uniquely when compared to other skeletal articulations in the human body. The primary function of the TMJ is to support mastication and articulation of the dentition, a complex biomechanical process that is beyond the scope of this chapter. The TMJ also plays a critical role in speaking and swallowing and is central to all mandibular functions.
FIGURE 15.1 The temporomandibular joint region, muscles, and facial nerve location.
Reconstruction of the TMJ, regardless of the indication, attempts to preserve the function of the mandible as well as to maintain facial symmetry. Duplication of the complex functional properties of the TMJ is impossible with current techniques; however, maintaining adequate opening, functional occlusion, and acceptable facial aesthetics are the requirements of appropriate reconstruction. The surgeon must keep these goals in mind when planning reconstructive surgery involving the TMJ.
HISTORY
Patients will often have pain in the preauricular region, pressure sensations, or occlusal disturbances when presenting with processes involving the TMJ. Patients may report other symptoms such as ear pain, clicking/ grinding noises, and rarely inability to open the mouth.
PHYSICAL EXAMINATION
Often the necessity for TMJ reconstruction can be predicted by evaluating the underlying disease. The physical examination of the TMJ requiring reconstruction may range from a completely normal examination in the case where joint resection is necessary for oncologic margins to a severely abnormal examination with complete inability to open the mouth. The patient may exhibit varying levels of trismus, progressive malocclusion, and pain within the joint. Hyperplastic conditions of the condyle may result in shifting of the mandible toward the unaffected side. Conversely, destructive processes may result in mandibular shifting toward the affected side. Occlusal and mandibular excursive mobility should be evaluated and abnormalities such as midline shifts, asymmetry, or other abnormalities of function documented.
The maximum interincisal opening distance should be measured and documented (distance between the upper and lower incisor edges with maximal opening, mm). Examination of the external auditory meatus on the affected side is critical to assess for invasive disease into the meatus or erosion of the tympanic plate of the temporal bone.
Facial nerve function as well as regional sensory disturbances should be evaluated and appropriately documented as the frontal branch of the facial nerve, greater auricular nerve, and auriculotemporal nerve may be involved with pathologic processes in this area. The chest and rib cage in particular should be examined for evidence of previous surgery or trauma.
INDICATIONS
Common indications for reconstruction include benign and malignant processes of the TMJ, or malignant lesions involving the region. Sequelae from adjuvant radiotherapy or bisphosphonate therapy may require resection and reconstruction of the TMJ. Malignant lesions of the temporal bone may also rarely result in the necessity of resection and reconstruction of the TMJ. Malignant processes of the overlying soft tissues such as squamous cell carcinoma or cancer of the parotid gland may invade the temporomandibular region and require ablative procedures to the TMJ. Benign lesions of the mandibular condyle such as condylar hyperplasia, or severe osteoarthritis as well as malignant lesions such as chondrosarcoma or osteosarcoma are also indications for TMJ reconstruction. While osteonecrosis of the TMJ is rare, extensive radiation damage or trauma to the area may also be an indication for reconstruction.
Indications for TMJ reconstruction are summarized below:
• Benign condylar conditions (condylar hyperplasia, severe arthritis)
• Odontogenic tumors (ameloblastoma, myxoma)
• Malignant tumor of the TMJ/condyle (osteosarcoma, chondrosarcoma)
• Malignant tumor in the TMJ region (squamous cell carcinoma, cancer of the parotid gland, sarcoma)
• Severe traumatic injuries (gunshot wounds)
• Osteonecrosis (osteoradionecrosis [ORN], bisphosphonate related osteonecrosis of the jaws [BRONJ])
CONTRAINDICATIONS
There are no specific contraindications to reconstruction of the TMJ. In some cases, reconstruction of the condyle of the mandible must also be accompanied by reconstruction of the glenoid fossa to avoid middle cranial fossa complications (i.e., extensive temporal bone resections). It should also be noted that reconstruction of the TMJ may not be necessary in selected cases and that reasonable function and occlusion may be maintained with appropriate rehabilitation, even in the absence of articulation of the mandible with the skull base.
PREOPERATIVE PLANNING
Anatomy
The TMJ is unique in the human skeleton as it is classified as a ginglymoarthrodial joint, that is it functions as both a rotational hinge as well as providing gliding movements during wide excursions. The condyle of the mandible articulates with the glenoid fossa of the temporal bone, separated by the articular disc. This disc is composed of dense fibrocartilage, unlike the hyaline cartilage found in most other joints in the skeleton. The TMJ and its associated articular disc are supported by several ligaments that connect the condyle to the base of skull including the temporomandibular ligament and the capsular ligament, as well as the stylomandibular and sphenomandibular ligament. The muscles of mastication, namely the temporalis and masseter muscles, as well as the lateral and medial pterygoid muscles further support and provide movement of the joint. It is the anatomic arrangement of these ligaments and muscles that allow for the complexity of mandibular function. Other anatomical considerations in the region include the parotid gland, which lies directly on the capsular ligament of the TMJ directly below the zygomatic arch. The temporal branches of the facial nerve traverse the zygomatic arch in this region and are the motor nerves most commonly at risk during joint reconstruction (Fig. 15.1). In addition, sensory branches of the auriculotemporal nerve pass on the posterior–medial aspect of the condyle and supply the skin of the temporal area as well as portions of the auricle and external auditory canal. The superficial temporal artery and vein are adjacent to the auriculotemporal nerve branches and may be encountered during dissection of the condyle in this region. Medial to the glenoid fossa at the level of the skull base, the middle meningeal artery passes intracranial via the foramen spinosum. Care must be taken when resecting the condyle to avoid aggressive dissection in this area. Additionally, the external carotid artery lies posterior and medial to the mandibular ramus (as well as the maxillary branch medial to the condylar neck) and should be identified if dissection in this area is indicated. Reconstructive surgery of the TMJ requires an understanding of both the anatomy of the craniomandibular articulation as well as the surrounding structures to provide for functional reconstruction while avoiding iatrogenic sequelae.
Imaging Studies
There are no specific imaging studies required for reconstruction of the TMJ; however, CT with contrast enhancement is relatively standard for evaluation of this area. In addition, panoramic radiographs may be useful to evaluate the extent of odontogenic tumors and cysts as well as other pathologic processes involving the mandible. Occasionally, MRI may be indicated to evaluate the soft tissue surrounding the TMJ as well as the articular disc for pathologic involvement. The pathologic process rather than the planned reconstruction primarily drives the appropriate imaging modality, unless custom TMJ prostheses are planned.
SURGICAL TECHNIQUE
A wide variety of reconstructive techniques have been used to restore the form and function of the TMJ and are listed below.
• Autogenous graft (costochondral, sternoclavicular) (Figs. 15.2 and 15.3)
• Free tissue transfer (fibula, metatarsal) (Fig. 15.4)
• Stock alloplastic reconstruction (titanium, silicone, acrylic, condylar prostheses)
• Custom alloplastic reconstruction (total joint prosthesis) (Fig. 15.5)
FIGURE 15.2 Inframammary incision design for rib graft harvest.
FIGURE 15.3 Costochondral rib harvest and graft inset for condylar reconstruction.
FIGURE 15.4 Fibular free tissue transfer for condylar reconstruction, in situ (via combined preauricular and transcervical approach). Facial nerve preservation was possible in this situation.
FIGURE 15.5 A–C. Total custom joint prosthesis with stereolithographic surgical model. Note combined preauricular and retromandibular approach to allow for placement of the condylar and fossa components of the prosthesis.
Reconstruction of the joint with alloplastic materials is beyond the scope of this chapter; however, advantages such as avoiding donor site morbidity, and a wide variety of options have led to the adoption of this technology for many indications. Problems with material wear and prosthetic failure have been reported and are the disadvantages of alloplastic materials.
Autogenous grafting is also widely used with the costochondral graft being the most commonly used graft. Advantages of the costochondral graft include growth potential in pediatric applications as well as providing autologous tissue with low donor site morbidity and relative ease of harvest. Other options such as the sternoclavicular joint and free metatarsal grafts may be useful in selected situations.
Another indication for autogenous grafting is in the reconstruction following resection of malignant tumors requiring radiotherapy, and in general, alloplastic materials should be avoided if radiotherapy is planned. An exception to this would be in the case of reconstruction in the pediatric age group in which case radiotherapy to autogenous grafts may result in severe ankylosis and in some cases osseous union to the temporal bone. In this situation, alloplastic materials may be used until the completion of therapy and the autologous grafting may be staged if desired. In cases of severe tissue injury and previous radiation where vascular supply is in question, free tissue transfer techniques should be considered.
Transcervical Approach
The transcervical approach to resection of the condyle has been well described. The ramus of the mandible is stripped free from the surrounding soft tissue in a subperiosteal plane, and the planned resection is performed, delivering the mandibular ramus and condyle inferiorly through the neck. The coronoid process is sectioned or stripped to release the mandible from the temporalis muscle, and the condylar attachments are released with electrocautery and periosteal dissection. The remaining ramus is then prepared, and the previously harvested costochondral graft (see Technique below) is then seated into the glenoid fossa and fixated to the native mandible with titanium plates and screws. The soft tissue attachments of the pterygomasseteric sling are then reapproximated to the ramus/condyle construct with permanent sutures to support the mandibular ramus.
Regardless of transcervical or transfacial approach, the condyle should be secured to the glenoid fossa to prevent postoperative migration. This can be achieved with a variety of techniques including circumzygomatic prolene sutures (using a passing awl) or suspension sutures secured to titanium miniplates placed on the zygomatic arch via a small preauricular incision (Fig. 15.3).
The costochondral graft offers the advantage of a cartilaginous surface opposing the glenoid fossa; however, several interpositional materials may be used to replace the TMJ/disc including auricular cartilage, temporalis muscle, tensor fascia, or alloplastic materials (if alloplastic materials or osseous grafts are used for reconstruction) (Figs. 15.4 and 15.5). Ideally, the temporomandibular disc can be left in situ to support the reconstruction.
Transfacial/Preauricular Approach
Often during the course of tumor ablative surgery or due to anatomical considerations, the lateral ramus and condylar resection proceeds via a combined transcervical and preauricular approach. In these situations, identification and preservation of the facial nerve is required. Cases in which oncologic principles require sacrifice of the facial nerve are obviously less problematic during reconstruction of the condyle. In the event that exposure of the condyle is required with preservation of the facial nerve, there are two possible approaches. A parotidectomy may be performed to identify the branches of the facial nerve at risk and to expose the ramus of the mandible and condyle. This is often required during ablative procedures. Alternatively, a preauricular approach proximal to the cartilage of the external auditory canal may be performed to the level of the temporalis fascia. The temporalis fascia may then be divided revealing the temporal adipose tissue pad, and dissection may proceed to the level of the root of the zygomatic arch. Subperiosteal dissection anteriorly will allow for retraction of the superficial temporal vessels, auriculotemporal nerves, and temporal branch of the facial nerve, which are superficial to this level of dissection. In some situations, formal facial nerve dissection is required (Fig. 15.4). The capsule of the TMJ may then be exposed and incised allowing for access to the mandibular condyle for completion of the resection. The ligamentous attachments and pterygoid muscles may be isolated and tagged at the time of resection of the ramus or condyle and reattached with permanent suture to the condylar reconstruction.
Costochondral Harvest
The technique of rib harvest has been well described. An inframammary incision is designed overlying the appropriate rib for harvest (Fig. 15.2). Generally, the sixth, seventh, and eighth ribs offer sufficient osseous and cartilaginous grafting material for reconstruction of the condyle.
Dissection with electrocautery through the fibers of the pectoralis major/minor muscles and the serratus anterior muscle posteriorly is performed to expose the anterior surface of the rib. Subperiosteal dissection of the rib is performed to allow for sectioning of the graft, which can be accomplished with a reciprocating saw or rib rongeur. The neurovascular bundle located inferiorly is avoided with careful dissection. Periosteal elevators should be used to protect the pleura during rib sectioning. Inadvertent violation of the pleural cavity requires underwater closure of the pleural space with maximal lung inflation to avoid significant pneumothorax. The graft is then cut to length, and the cartilaginous portion of the graft is trimmed with a scalpel, so that approximately 5 mm of cartilage remains on the condylar surface of the graft. Large amounts of cartilage are unnecessary and prone to fracture. A chest radiograph should be obtained after costochondral harvest.
POSTOPERATIVE MANAGEMENT
Perhaps the most important aspect of temporomandibular reconstruction is the postoperative rehabilitation. Disarticulation of the condyle and reconstruction separates the muscles of mastication from the mandible, and postoperative physical therapy must be employed during the first 6 to 12 weeks of healing to avoid permanent facial deformity, malocclusion, and poor functional results. In addition to the technical aspects mentioned above, dentate patients should have the occlusion supported with arch bars and guiding elastics to maintain the occlusion during healing. Maximal opening and excursive movements should be initiated 1 week after surgery and continued for several weeks to prevent postoperative trismus and malocclusion. The importance of maintaining the maximum opening possible cannot be overstated. This is especially important if radiotherapy or radiotherapy is planned postoperatively. Inappropriate postoperative rehabilitation resulting in severely limited opening is not easily addressed in the majority of cases.
COMPLICATIONS
Complications of reconstruction of the condyle include injury to sensory and motor nerves, infection, and perforation of the external auditory meatus. Donor site complications such as pneumothorax are managed in the standard fashion. A small, stable pneumothorax may be observed, but a chest tube is indicated for a large or expanding pneumothorax.
Long-term complications such as graft migration, graft resorption, and the resulting malocclusion can be avoided by employing condylar suspension techniques, arch bars with guiding elastics, and elastic jaw support straps. Rigorous physiotherapy and monitoring are required in the postoperative period to avoid occlusal disturbances and the associated functional consequences.
RESULTS
Functional results, in general, are quite good with condylar reconstruction. Some mild limitation of excursive and opening movements is to be expected. The majority of patients will tolerate a normal diet when healing is complete. Postoperative trismus related to adjuvant therapy and surgery remains problematic for patients with extensive malignant tumors.
PEARLS
• Reconstruction of the ramus and/or condyle can be performed with autogenous or alloplastic techniques, the selection of which is driven by a variety of considerations including diagnosis, age, and reconstructive goals.
• Coronoidectomy should be performed in the majority of cases to prevent postoperative trismus.
• Interpositional grafts should be considered if the temporomandibular disc is resected.
• Cartilage of costochondral grafts (sixth, seventh, and eighth ribs) should be trimmed to approximately 5-mm thickness.
• Postoperative rehabilitation is the single most important factor in the long-term success after reconstruction of the condyle.
• Correction of unfavorable results is extremely challenging once 6 to 8 weeks of healing has elapsed.
PITFALLS
• Prosthesis hardware failure continues to be a challenge long term.
• Patients undergoing radiotherapy postoperatively are at increased risk of exposure of hardware, osteonecrosis, and graft resorption.
• Autogenous grafts are prone to osteoneogenesis and ankylosis in patients in the pediatric age group, and rehabilitation is critical.
• Injury of the temporal branch of the facial nerve can be avoided by meticulous surgical technique
• Damage to the middle meningeal artery medial to the mandibular condyle must be avoided.
• Inappropriate postoperative physiotherapy may result in inadequate mouth opening and malocclusion, which is extremely difficult to correct.
INSTRUMENTS TO HAVE AVAILABLE
• Standard head and neck reconstruction tray
• Steven tenotomy scissors, curved 15 cm 6 inches
• Baby Metzenbaum scissors 14 cm 5 ¼ inch
• DeBakey straight 1.5 mm tip
• Rib harvest set
SUGGESTED READING
Saeed N, Hensher R, McLeod N, et al. Reconstruction of the temporomandibular joint autogenous compared with alloplastic. Br J Oral Maxillofac Surg 2002;40(4):296–299.
Khariwala SS, Chan J, Blackwell KE, et al. Temporomandibular joint reconstruction using a vascularized bone graft with Alloderm. J Reconstr Microsurg 2007;23(1):25–30.
Marx RE, Cillo JE Jr, Broumand V, et al. Outcome analysis of mandibular condylar replacements in tumor and trauma reconstruction: a prospective analysis of 131 cases with long-term follow-up. J Oral Maxillofac Surg 2008;66(12):2515–2523.
Driemel O, Braun S, Müller-Richter UD, et al. Historical development of alloplastic temporomandibular joint replacement after 1945 and state of the art. Int J Oral Maxillofac Surg 2009;38(9):909–920.
Singh V, Verma A, Kumar I, et al. Reconstruction of ankylosed temporomandibular joint: Sternoclavicular grafting as an approach to management. Int J Oral Maxillofac Surg 2011;40(3):260–265.