Unfortunately, the role of TMJ surgery in the management of common disorders such as traumatic injuries , internal derangement and osteoarthrosis is less clear and often ill-defined [3,4]. These are placed under the heading of relative indications because nonsurgical management seems to be equally effective in the management of these common disorders as surgical intervention. However, there are situations in which the benefits of TMJ surgery are indisputable. These are further divided into general and specific indications. The most commonly cited general indication for TMJ surgery is in which the joint disorder remains refractory, or is not responding to nonsurgical therapy, in particular, occlusal splints, medication and physiotherapy . Some may argue that the failure of nonsurgical therapy may well reflect the possibility of misdiagnosis, in which surgical intervention should have been considered earlier on if the diagnosis was correctly made in the first place .
From a clinical standpoint, surgery is more likely to succeed if the source of the pain and dysfunction is well localized to the TMJ. Hence, pain is specifically related to the TMJ, particularly when pain is elicited on direct palpation, loading of the joint and functional movements of the joint. Mechanical interferences arising from within the joint that limits its full functional potential, such as painful clicking, locking and crepitus, are all good indicators of likely surgical disorders. It must be emphasized that the more localized the symptoms are to the TMJ, the more likely surgery will have a favourable outcome.
Specific indications for TMJ surgery include chronic severe limited mouth opening and gross mechanical interferences, such as painful clicking and crepitus that fail to respond to TMJ arthrocentesis and arthroscopy. Radiologically confirmed degenerative joint disease, with clinical features of intolerable pain and joint dysfunction, are essentially the key criteria for TMJ surgical intervention .
It must be stressed that where significant joint pathology has been identified, both clinically and radiologically, nonsurgical therapies only treat the symptoms. In these situations, only surgical intervention can treat the disease . Therefore, all TMD practitioners should be alert to the possibility that in some cases the only realistic option is TMJ surgery, which should never be denied to patients because of prejudices or unfounded beliefs that surgery is too risky. Even though most clinical studies are based more on observation than sound scientific principles, the literature is unequivocal in its support for surgery in the management of certain TMJ disorders [7,8].
Surgical procedures to the temporomandibular joint
There are a myriad of surgical procedures that are undertaken to either repair or remove damaged or diseased joint tissues [4,5]. Disc repair and repositioning has fallen out of favour in recent years (Fig. 4), as the results of these procedures have been somewhat equivocal . Studies have shown that the surgical repositioning of displaced discs is often short lived as the discs have been found to revert to their displaced position when imaged postoperatively [10–13]. Furthermore, attempts to repair damaged or worn discs often result in failure because of the lack of a direct blood supply to the disc and the dynamic forces imparted on the disc during normal jaw function, which prevents healing [10,14]. The introduction of TMJ arthroscopy , and later arthrocentesis , further questioned the role of disc repositioning in the management of internal derangement that results in closed lock, as these lesser procedures are found to be effective in releasing stuck joints without the need to reposition the displaced disc [17–19].
Other researchers have discussed the role of removing obstructions to the free movement of the disc such as eminence reduction, or eminectomy, as a means of reducing the symptoms of internal derangement. Once again, the evidence for the efficacy of this procedure is lacking [4,20]. The old idea of high condylar shaves to reduce the pressure on the disc has also been revived on a number of occasions but, once again, long-term data are also lacking .
One procedure that has become the mainstay in the treatment of severe TMJ internal derangement is the discectomy [22–24], or complete removal of the disc (Fig. 5). Discectomy is one of the few TMJ surgical procedures that has more than 20-year follow-up data to show long-term effectiveness [25–29]. Although TMJ discectomy has worked well, the problems encountered are mainly centred on the remodeling effects on the condyle, which radiologically appears as osteoarthrosis [30–32]. Therefore, numerous attempts have been made over the years to replace the disc with either alloplastic or autogenous grafts but with little success. The disastrous experience of Teflon proplast and sialastic implants as disc replacement materials [33,34] has led to the concerted effort to find an autogenous graft that is both safe and effective in reducing condylar remodeling following discectomy [8,35]. Ear cartilage has been shown to lead to fragmentation, fibrosis and ankylosis of the TMJ,  whereas full-thickness skin has the propensity to result in epidermoid cyst formation . Pedicled temporalis muscle and fascia are still used today , but these also have limited functionality with the potential to exacerbate trismus when temporalis muscle is surgically breached . The use of dermis graft from the lower abdomen has been reported with good results, although it has not been found to offer a protective barrier to condylar remodeling . One autogenous graft that has shown some promise is the dermis-fat graft from the lower abdomen, which was first introduced by Dimitroulis  as an interpositional material for TMJ ankylosis, and more recently, for use as a space filler following TMJ discectomy with good outcomes .
As yet, there has been limited success by tissue engineering laboratories to fabricate a disc substitute using biological scaffolds impregnated with stem cells, which are modulated by active biochemical agents to produce a new disc that can be used to replace a diseased or worn disc . Even if the perfect disc substitute is successfully developed, the problem remains as to how to properly anchor the new disc to the surrounding tissues that would allow an ideal disc–condyle relationship to be maintained during normal joint function.
Temporomandibular joint replacements
When there is end-stage joint disease, tumour or severe trauma, and none of the components of the TMJ can be salvaged, then both disc and condyle must be resected. This leaves patients with the dual physical handicaps of lower facial asymmetry and malocclusion, unless the joint is reconstructed with either autogenous grafts or alloplastic joints.
Unlike other joints in the body, the TMJ has had a long history of joint replacement materials consisting largely of autogenous grafts, in particular, the costochondral rib graft (Fig. 6) that is easily harvested and mannered into a new condyle and secured to the ramus of the mandible with wires or screws [35,42]. Although rib grafts have been useful in young patients, older patients are not appropriate for rib graft replacements because of the brittle nature of the rib, which increases the likelihood of fracture and also because of ankylosis when the cartilaginous cap is placed hard up against the glenoid fossa.
In older patients, the most appropriate joint replacement for the TMJ is the alloplastic prosthesis consisting of a metal condyle articulating against a high-molecular weight polymer fossa prosthesis (Fig. 7). Hemi-prosthetic joints consisting of a prosthetic fossa alone have been well described and seem to work well . However, the use of prosthetic metal condyles against a natural bony fossa cannot be recommended as these result in erosion of the skull base, unless it is protected by a prosthetic fossa. Early prosthetic joint replacements met with little success but more recent prosthetic joints, including both off-the-shelf varieties and custom-made prostheses, have benefited from the technological advances and from the extensive experience of our orthopaedic colleagues [44,45].
Risks versus benefits of temporomandibular joint surgery (Table 2)
Although the classically cited risks for TMJ surgery are facial nerve palsy and scarring, there are, in fact, many potential risks that are not so obvious to nonsurgical practitioners, such as malocclusion, restricted mouth opening and deafness  (Table 2). An inexperienced surgeon who seldom ventures into the TMJ is more likely to encounter problems through poor diagnostic skills, which may result in poor patient selection and suboptimal surgical technique that does more harm than good for the patient. Fortunately, in experienced hands, complications associated with TMJ surgery are uncommon.
The benefits of TMJ surgery can only be realized by appropriate case selection, which is supported by an accurate diagnosis. An experienced surgeon with good patient skills will be able to identify patients who are compliant with treatment regimes, who have a good understanding of their disorder and who do not harbour unrealistic expectations for treatment outcomes. In contrast, an inexperienced surgeon with poor patient skills will be tempted to operate on patients who have a poor understanding of their disorder, a long history of poor compliance with treatment and with unrealistic expectations. In these situations, the risks of surgery would far outweigh the benefits.
A multidisciplinary team approach to TMD management, especially in which surgery is involved, is essential in the fundamental care of all patients with TMD. Surgeons who work in isolation run the risk of overlooking serious issues that may adversely impact on the long-term care and well-being of the patient. Therefore, it is important that input from all members of the specialist team is carefully considered so that a balanced judgement can be made as to whether the patient in question is an appropriate candidate for TMJ surgery. And most importantly, a decision has to be made as to whether the benefits of TMJ surgery far outweigh the inherent risks.
Future of temporomandibular joint surgery
Although we all harbour a tendency to consider the TMJ as a special joint, it is not immune from the disorders and diseases that afflict other joints. Therefore, it should be no surprise that the future holds great promise for TMJ surgery, which is reflected in the dominance of orthopaedic surgery that largely treats disorders and diseases of various joints in the body. Much can be learned from the vast experience of orthopaedic surgery.
Current advances in TMJ surgery have been overshadowed by the universal perception among nonsurgical practitioners that surgery still entails unacceptable risks. Concerted efforts must be made to educate all TMD practitioners of the benefits of TMJ surgery so that patients do not suffer unnecessarily from ongoing nonsurgical treatments that ultimately prove to be ineffective in the management of their condition. Clinicians have a fundamental duty to their patients to offer them the best available treatment.
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Keywords:© 2011 Egyptian Associations of Oral and Maxillofacial Surgery
Temporomandibular joint surgery; TMJ arthrotomy; TMJ prosthesis