Temporomandibular disorders (TMD) are sometimes encountered in dental practice when patients may complain of cramp-like pain in their masticatory muscles or painful clicking in their temporomandibular joints (TMJ) which may have been exacerbated by lengthy dental procedures. While most patients recover with simple measures such as jaw rest and soft diet, others require professional care that may involve any combination of occlusal splint therapy, physiotherapy and medications. Of the TMD patients who seek professional care, only about 5% harbour a functional or pathological problem in their TMJ which may be amenable to surgery.1–5
While occlusal splint therapy is pivotal to the management of most TMD,2 it is unfortunate that some dental practitioners have a poor appreciation of the small but important role of surgery4 in the management of TMD which results in some patients being denied access to appropriate care. As far as the surgical management of joint disease is concerned, TMJ arthrocentesis appears to be the panacea for all disorders regardless of how significant the joint disease may be. Regrettably, many practitioners fail to realize that TMJ arthrocentesis has limited applications, such as acute onset closed lock, and cannot treat advanced joint disease.1 To use a dental analogy, it is like using fissure sealants to treat grossly carious teeth, which is obviously not going to solve the problem.
A failure to appreciate surgical joint pathology by the TMD clinician may result in a concoction of non-surgical therapies that fail to address the patient’s intra-articular disease.2 Eventually, patients may become disheartened by the lack of progress and spiral into a vicious cycle of anxiety and depression as they are led to believe that there is nothing more that can be done for them. In a small number of these patients TMJ surgery may well be the answer, but the lack of familiarity on the treating clinician’s part makes them reluctant to refer the patient for surgery. The aim of this paper was to review the role of TMJ surgery and its place in the treatment armamentarium of temporomandibular disorders using clinical cases treated by the author as a means of illustrating the benefits of surgery in select patients.
The rationale for temporomandibular joint surgery
While surgery is often considered as an option of last resort, there are instances where surgery is the definitive and sometimes the only treatment option.3,4 In a fundamental sense, surgery is used to restore and repair damaged tissue or remove tissue that cannot be salvaged. Surgery is also used to promote healing of tissues by replacing missing tissues with grafts.4,5 For example, it is ludicrous to suppose that a chronically displaced disc can be reduced by indirect, non-surgical therapies. Equally doubtful is the non-surgical management of collapsed articular cartilage and osteophytes that interfere with the smooth, pain-free function of the joint. These are just two common examples where surgery plays a pivotal role.
Where there is significant disease in the joint, in many cases, surgery is the definitive treatment modality.5 A clear understanding of joint pathology and the role that surgery plays in the management of joint disease are indispensable requirements for all successful TMD practitioners. Magnetic resonance imaging (MRI) has provided us with a fascinating view of the TMJ6 and there is little excuse on the part of all TMD practitioners, in particular, not to familiarize themselves with this useful investigative modality. The right combination of symptomatic history, clinical features and radiological signs will readily reveal whether the TMD patient is an appropriate candidate for surgery.3 It is crucial that all TMD practitioners familiarize themselves with every treatment option available, and not forget that TMJ surgery is one essential treatment modality that must never be overlooked.
In the ideal world, the role of surgery should be subject to the scrutiny of scientific clinical trials. Unfortunately, unlike pharmacotherapy, clinical trials involving surgery, where the benefits are compared to placebo, cannot be undertaken for obvious ethical reasons.7 We cannot perform ‘sham’ operations to determine if the proposed surgery undertaken is better than a placebo response. As far as TMJ surgery is concerned, we must rely on best available evidence that has appeared in the literature over the past four decades.3,7,8
Indications for temporomandibular joint surgery
Open surgery (arthrotomy) of the TMJ is undertaken for a wide range of joint disorders. In 1994, Dolwick and Dimitroulis4 divided the indications for surgery into relative and absolute (Table 1). As far as absolute indications are concerned, TMJ surgery has a definite undisputed role in the management of uncommon or rare joint disorders. TMJ ankylosis, whether fibrous or bony, is a classic example of a TMJ disorder where surgery has a pivotal role. Other rare disorders, such as synovial chondromatosis, provide another example of the clear role that surgery has in removing the abnormal growths.
|1. Ankylosis – e.g. fibrous or osseous joint fusion|
|2. Neoplasia – e.g. osteochondroma of the condyle|
|3. Dislocation – i.e. Recurrent or chronic|
|4. Developmental disorders – e.g. condylar hyperplasia|
|1. Internal derangement|
|A. General indications|
|i. Disorder not responding to non-surgical therapy|
|ii. Where the TMJ is the source of pain and dysfunction|
|a. Pain localized to the TMJ|
|b. Pain on functional loading of the TMJ|
|c. Pain on movement of the TMJ|
|d. Mechanical interference with TMJ function|
|B. Specific indications|
|i. Disorder not responding to TMJ arthrocentesis or arthroscopy|
|ii. Chronic severe limited mouth opening|
|iii. Advanced degenerative joint disease with intolerable symptoms of pain and joint dysfunction|
|iv. Confirmation of severe joint disease on CT scan or MRI|
Unfortunately, the role of TMJ surgery in the management of common disorders such as traumatic injuries,9 internal derangement and osteoarthrosis is less clear and often ill-defined.3,4 These are considered under the heading of relative indications because non-surgical therapies appear to be equally effective in the management of these common disorders as surgical intervention. However, there are situations where 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 where the joint disorder remains refractory, or not responding to non-surgical therapy, in particular, occlusal splints, medication and physiotherapy.2 Some may argue that the failure of non-surgical therapy may well reflect the possibility of misdiagnosis where surgical intervention should have been considered earlier on if the diagnosis was correctly made in the first place.3 This is not to say that chronic pain syndromes should be ignored, since failed conservative therapy may well indicate a plethora of chronic pain conditions that require specialist pain management, which is a whole subject in its own right, and so will not be elaborated any further in this paper. Suffice to say that clinicians must be careful to differentiate between failed TMD cases that require chronic pain management and those that would benefit from a surgical opinion.
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 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 limit 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.4
It must be stressed that where significant joint pathology has been identified, both clinically and radiologically, non-surgical therapies only treat the symptoms. In these situations, only surgical intervention can treat the disease.3 Therefore, all TMD practitioners should be alert to the possibility that in a few select 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
Prior to the introduction of sophisticated imaging such as CT and MRI, surgeons were less discerning with their patients and considered joint surgery as part investigative and part therapeutic. This resulted in poor outcomes for some patients who had chronic neuromuscular pain conditions and normal TMJs that were subjected to surgical insults that failed to relieve their symptoms. In light of past mishaps, contraindications to surgery have become intertwined with the adverse risks of TMJ surgery (outlined in Table 2). Therefore, it is critical to point out that surgery has no role in the management of patients with chronic pain syndrome or muscular problems that do not involve the joint itself.
|1. Poor patient selection|
|a. Patient is an unreliable historian|
|i. Secondary gain|
|ii. Compensation seeking|
|b. Patient has unrealistic expectations of surgical outcome|
|c. Significant medical history|
|d. Psychiatric history|
|2. Inexperienced clinician|
|a. Poor diagnostic skills|
|b. Limited surgical experience|
|ii. Infection and wound breakdown|
|3. Surgical mishaps|
|a. Facial nerve paresis|
|i. Condylar resorption|
|ii. Overzealous arthroplasty|
|d. Severe trismus (arthrogenous)|
|4. Persistent symptoms|
|a. Failure to continue supportive non-surgical therapy|
|b. Poor patient compliance – cannot follow instructions|
|c. Misdiagnosis – chronic pain syndrome, myofascial pain, normal joint|
Surgical procedures to the temporomandibular joint
TMJ surgery is technically one of the more difficult surgical dissections in the maxillofacial region. While the close proximity of the facial nerve is the main reason for the difficult surgical access, other important anatomical structures such as the terminal branches of the external carotid artery and accompanying rich plexus of veins also add to the complexity of the dissection. With the middle cranial fossa above, and the middle ear behind the TMJ, there is little room for surgical error as both these cavities are only a few millimetres away from the joint itself. That is why few oral and maxillofacial surgeons have the inclination, confidence, skill and experience to tackle such a small inaccessible joint, which is approached via an incision in the skin crease in front of the ear.
There are myriad surgical procedures which are undertaken to either restore, repair or remove damaged or diseased joint tissues.4,5 TMJ arthrocentesis and arthroscopy have proven to be the most effective way of managing ‘stuck’ joints by the simple process of lubricating the superior joint space and allowing mobilization of the articular disc.1,10 While TMJ arthrocentesis is useful for cases of acute onset closed lock,1 TMJ arthroscopy (Fig 1) provides a more effective approach to the management of chronic (>3 months) or recalcitrant cases of closed lock.11 Disc repair and repositioning has fallen out of favour in recent years as the results of these procedures have been somewhat equivocal.12 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.12–15 Furthermore, attempts to repair damaged or worn discs often result in failure due to 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.12,16 The introduction of TMJ arthroscopy,17 and later arthrocentesis,18 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.10,19,20
Others 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.4,21 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, the long-term data are also lacking.22
One procedure which has become the mainstay in the treatment of severe TMJ internal derangement is the discectomy,23–25 or complete removal of the disc. Discectomy is one of the few TMJ surgical procedures which have >20 year follow-up data to show the long-term effectiveness.26–30 While TMJ discectomy has worked well, the problems encountered are mainly centred on the remodelling effects on the condyle which radiologically appears as osteoarthrosis.31–33 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 materials34,35 has led to the concerted effort to find an autogenous graft that is both safe and effective in reducing condylar remodelling following discectomy.8,36 Ear cartilage has been shown to lead to fragmentation, fibrosis and ankylosis of the TMJ37 while full thickness skin has the propensity to result in epidermoid cyst formation.38 Pedicled temporalis muscle and fascia are still used today,39 but these also have limited functionality with the potential to exacerbate trismus when temporalis muscle is surgically breached.8 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 remodelling.40 One autogenous graft that has shown some promise is the dermis-fat graft from the lower abdomen which was first introduced by Dimitroulis41 as an interpositional material for TMJ ankylosis, and more recently for use as a space filler following TMJ discectomy with good outcomes.8
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.42 Even if the perfect disc substitute is successfully developed, the problem remains as how to properly anchor the new disc to the surrounding tissues that would allow the ideal disc-condyle relationship to be maintained during normal joint function.
Temporomandibular joint replacements
Where 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 which is easily harvested and fashioned into a new condyle and secured to the ramus of the mandible with wires or screws.36,43 While 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 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 2). Hemi-prosthetic joints consisting of a prosthetic fossa alone have been well described and appear to work well.44 However, the use of prosthetic metal condyles against a natural bony fossa cannot be recommended as they 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 as well as custom-made prostheses, have benefited from the technological advances and extensive experience of our orthopaedic colleagues.45,46
To help illustrate the role of TMJ surgery, three clinical cases treated by the author will be described below.
A 23-year-old female was referred to the author for management of a four-month history of chronic closed lock. She had a previous long-standing history of painful clicking in the right TMJ that was successfully managed with occlusal splint therapy up until four months prior to presentation when she woke up with limited mouth opening that failed to respond to subsequent physiotherapy, anti-inflammatories and ongoing splint therapy. On presentation, the patient had a maximum interincisal opening of 20 mm with gross deviation of the mandible to the right side on opening, indicative of lack of translation of the right mandibular condyle. Radiological investigations (including MRI) showed non-reducing disc displacement in the right TMJ. The patient underwent right TMJ arthroscopy which highlighted the presence of inflammation of the synovial capsule as well as adhesions (Fig 3) which were arthroscopically treated by lavage and lysis of adhesions with injection of steroids. The disc was arthroscopically released and mobilized and by the end of the procedure 40 mm of interincisal opening was achieved. Postoperatively, the patient was able to achieve 42 mm within three weeks of the procedure with reduced clicking in the right TMJ. By six weeks her pain levels had significantly diminished, although she was advised to return to her occlusal splint as a precautionary measure.
A 63-year-old female was referred to the author for management of a constant dull pain in the left TMJ that had become progressively worse over the previous 12 months despite 18 months of occlusal splint therapy by her dentist and six months of low-dose tricyclic medication by her medical practitioner. She was referred to an oral medicine specialist who immediately ordered radiological investigations which demonstrated calcified bodies within the articular disc of the left TMJ (Fig 4). Fortunately, the surrounding condyle, glenoid fossa and articular eminence were unaffected. The patient underwent left TMJ surgery through a preauricular incision where the disc was found to be peppered with calcified firm lumps (Fig 4) and so was completely excised. As part of the reconstruction, the resultant joint cavity was filled with an abdominal dermis-fat graft to prevent haematoma, scarring and possible ankylosis formation within the joint. The disc specimen was sent for histopathology which was reported as pseudogout, a rare condition mainly found in the fingers and toes. The patient remained in hospital overnight and was fully recovered within two weeks of her procedure. She was back to a normal diet in six weeks with smooth, pain-free function in the left TMJ. She was last reviewed four years following her surgery with no clinical or radiological evidence of recurrence of the lesion, and continued to enjoy full range of pain-free function in the left TMJ.
A 46-year-old female was referred to the author for surgical management of severe osteoarthrosis affecting the right TMJ that had become painfully intolerable over the previous six months. The osteoarthrosis was clearly visible on routine OPG which showed severe destruction of the right mandibular condyle (Fig 5). Arthroscopic biopsy of the right TMJ was undertaken to exclude the possibility of neoplasia. The patient was taken to theatre where she had the right TMJ resected and a total prosthetic joint replacement was undertaken to restore the missing joint components. The histopathology confirmed severe osteoarthrosis with significant degeneration of the right mandibular condyle and articular disc. Her four nights in hospital were uneventful and she was back to a normal diet in six weeks. At her one-year review, she reported no joint pain with an interincisal opening of 36 mm and was enjoying a normal dietary range. Apart from three months of physiotherapy, no further TMD therapy was required postoperatively.
Risks vs. benefits of temporomandibular joint surgery
While the classically cited risks for TMJ surgery are facial nerve palsy and scarring (Fig 6), there are, in fact, many potential risks that are not so obvious to non-surgical practitioners such as malocclusion, restricted mouth opening and deafness47 (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, most complications associated with TMJ surgery are of a temporary nature and account for less than 5% of all procedures.4,5
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, have a good understanding of their disorder, and do not harbour unrealistic expectations for treatment outcomes. On the other hand, 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 unrealistic expectations. In these situations the risks of surgery would far outweigh the benefits.
A multidisciplinary team approach to TMD management, especially where surgery is involved, is essential in the fundamental care of all TMD patients. 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.
The future of temporomandibular joint surgery
While 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 many other joints in the body. It is no coincidence that orthopaedic surgery is the largest and busiest of all surgical specialties worldwide and much can be learned from their vast experience of surgery to the knee, hip and shoulder joints.
Current advances in TMJ surgery have been overshadowed by the universal perception among dental practitioners that TMJ surgery still entails unacceptable risks. All dental practitioners should be aware of the benefits of TMJ surgery so that patients do not suffer unnecessarily from ongoing non-surgical 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.