The role of temporomandibular joint (TMJ) surgery is ill-defined, so a universal classification is needed to collate the evidence required to justify the surgical interventions undertaken to treat TMJ disorders. The aim of this article is to introduce a new classification that divides TMJ disorders into 5 categories of escalating degrees of joint disease that can be applied to TMJ surgery. Using a category scale from 1 to 5, with category 1 being normal, and category 5 referring to catastrophic changes to the joint, the new classification will provide the basis for enhanced quantitative and descriptive data collection that can be used in the field of TMJ surgery research and clinical practice. It is hoped that this new classification will form the basis of what will eventually become the universal standard surgical classification of TMJ disorders that will be adopted by both researchers and clinicians so that ultimately, the role of TMJ surgery will be based on evidence rather than conjecture.
The role of temporomandibular joint (TMJ) surgery is not well defined. Part of the reason is that hard evidence is lacking since, unlike orthopaedic surgery, there is no universal classification that allows the collection of standard data that can be used to compare the various techniques published in the literature. Temporomandibular disorder (TMD) specialists have been proactive in establishing the Research Diagnostic Criteria (RDC) for TMD and have used this as the basis for assessing various non-surgical strategies. The field of TMJ surgery has only managed to come up with what constitutes successful TMJ surgery outcomes.
Evidence is needed to define the role of TMJ surgery, and evidence needs data which can only be derived from universal medical codes. Universal medical codes are collected from classifications and what the field of TMJ surgery needs is a universal classification in order to collate the evidence required to justify the surgical interventions undertaken to treat TMJ disorders. The aim of this article is to introduce a new surgical classification that includes all TMJ specific disorders that can be applied to future studies related to TMJ surgery.
Reasons for classification
Medical classification is the process of transforming descriptions of diagnoses and procedures into universal medical code. It is from these codes that data can be collected and analysed for the purpose of providing the hard evidence needed to determine whether TMJ surgery is effective in providing material benefit to patients. In other words, the hard evidence for TMJ surgery can only be secured with a universally recognized surgical classification of TMJ disorders.
Presently, there are 3 main classifications related to TMD; the Research Diagnostic Criteria (RDC) for TMD, the Wilkes Classification for TMJ internal derangement, and the most recent American Academy of Orofacial Pain (AAOFP) Classification of TMD. The RDC-TMD classification is the most widely used by TMD researchers who stress the importance of psychosocial dysfunction (Axis II) as opposed to physical disorders (Axis I) and come up with a wide variety of complex calculations that often have little bearing on clinical practice. The RDC-TMD has remained firmly embedded in the research world with little use in clinical practice.
The Wilkes classification is the most widely used classification that has been adopted by surgeons who treat TMJ disorders. Its widespread adoption is linked to its simplicity in describing escalating joint pathology in 5 stages, but it concentrates on only 2 disorders (internal derangement and osteoarthritis) and fails to include other TMJ disorders such as ankylosis and tumours which are covered by a host of other sub-classifications that will not be elaborated here.
The AAOFP classification of TMD has refocused its attention on articular disorders with a more widespread appreciation of joint disease, not confined to internal derangement, but also ankylosis, trauma and even developmental conditions of the TMJ are listed. The masticatory muscle disorders are listed simply as local, general and centrally mediated which reflects the poor understanding of extra-articular disorders related to TMD. While the AAOFP classification of TMD is a vast improvement on the cumbersome RDC-TMD, there is still a problem when it comes to data collection as the AAOFP classification does not allow for degree of disability which is quantifiable like the Wilkes Classification.
In 1994, Dolwick and Dimitroulis published a table which divided indications for TMJ surgery into relative and absolute. Relative indications were stipulated for common TMJ disorders such as internal derangement and osteoarthrosis, while absolute indications were reserved for less common TMJ disorders such as ankylosis and neoplasia of the TMJ. Surgical indications such as this only indicate when TMJ surgery should be considered, but does not stipulate what kind of surgery is required and for which disease.
In the development of a new classification, it is essential to purge the weaknesses and build on the strengths of previous classifications. Dozens of new medical classifications are introduced to the literature every year, but history has shown that only the simplest, such as the classic Le Fort classification for midface injuries, that are easy to remember and simple to understand are universally adopted. The criteria for the new classification are given in Table 1 . The purpose of this new classification ( Table 2 ) is to specify the role of TMJ surgery in all TMJ disorders in a graded fashion across a spectrum of 5 categories of escalating degrees of joint disease.
|Simple – easy to understand and remember|
|Clear – unambiguous description of each category|
|Focused – on the TMJ|
|Inclusive – of all TMJ disorders and diseases|
|Specific – so that patient populations can be easily defined and compared|
|Universal – adopted by all TMD clinicians and researchers|
|No surgery required or indicated|
|TMJ minor changes (all joint components are salvageable)|
|TMJ arthrocentesis/arthroscopic lavage|
|TMJ moderate changes (most joint components are salvageable)|
|TMJ operative arthroscopy/TMJ arthroplasty|
|TMJ severe changes (few joint components are salvageable)|
|TMJ discectomy ± condylar surgery|
|TMJ catastrophic changes (nothing in the joint is salvageable)|
|TMJ resection ± total joint replacement|
Category 1: TMJ normal joint
No surgery is required. In this category ( Table 3 ), a patient may present with pain specifically centred around the TMJ but report no history of locking, dislocation or difficulty chewing. There are no audible or palpable joint noises and the patient exhibits a full range of jaw movement with symmetrical opening. Plain films, magnetic resonance imaging (MRI) and computed tomography (CT) scans show normal joint with no radiological abnormalities ( Fig. 1 ). The patient may have sustained recent acute trauma following whiplash, fall or assault or experienced an ear infection. In long standing cases the TMJ arthralgia may be secondary to myofascial pain, fibromyalgia or part of a neuralgia or psychosomatic disorder. TMJ surgery has no role in these situations and patients must be carefully assessed for other ailments that may be contributing to or exacerbating the TMJ arthralgia.
|No joint noises|
|No history of locking or dislocation|
|Full range of jaw movement|
|OPG – normal condyles|
|MRI – normal TMJ|
|Joint contusion – acute trauma|
|Ear pathology – otalgia|
|Medication ± splint|
|Surgery has no role|
Category 2: TMJ minor changes
All joint components are salvageable. In this category ( Table 4 ) a patient may present with intermittent TMJ pain, joint clicking and occasional locking. Plain films demonstrate normal condyles but MRI may show mild disc displacement with reduction or excess fluid in the joint indicative of inflammation ( Fig. 2 ). TMJ arthrocentesis may be appropriate for cases of acute onset closed lock and TMJ arthroscopy may demonstrate mild inflammation with occasional adhesions. Both procedures may help unlock a stuck joint, but the primary treatment modality remains conservative (i.e. anti-inflammatory medication, jaw rest, soft diet).
|Intermittent joint pain|
|OPG – normal condyles|
|MRI – disc displacement with reduction|
|Disc and condyle normal contour|
|Early TMJ internal derangement|
|TMJ arthroscopic lavage|
Category 3: TMJ moderate changes
Most joint components are salvageable. In this category ( Table 5 ), patients report painful long-standing closed lock (>2 months), joint swelling or painful recurrent dislocation of the TMJ. The patient may report difficulty chewing with moderate to severe pain levels exacerbated by jaw function. Mandibular opening is restricted either because of fear of dislocation or actual joint pain which often results in deviation of the mandible to the affected side. Because of the restricted mouth opening joint noises are often absent. While plain films may show normal condylar morphology, MRI shows non-reducing disc displacement. The disc may exhibit mild contour deformity and there may be a prominent articular eminence that obstructs the backward path of the translated condyle ( Fig. 3 ). Diagnostically, the patient may have suffered an acute event such as a fracture dislocation of the condylar head or simply dislocation of the condyle. In long standing cases, the patient may be suffering from moderate TMJ internal derangement or synovial chondromatosis. In category 3 cases, the patient would benefit from operative TMJ arthroscopy, modified condylotomy, TMJ arthroplasty consisting of disc repositioning with or without eminectomy, or open reduction and internal fixation of displaced condylar fractures.
|Painful chronic closed lock|
|Recurrent joint swelling|
|Painful recurrent dislocation|
|OPG – normal condyles|
|MRI – disc displacement without reduction|
|Disc normal or mildly deformed contour|
|Moderate TMJ internal derangement|
|Recurrent TMJ dislocation|
|TMJ synovial chondromatosis|
|Dislocated condylar fracture|
|TMJ arthroscopy (operative)|
|TMJ arthroplasty – disc plication/repositioning ± eminectomy|
|ORIF fractured condyle|