MANDIBULAR TRACKINGIdeal mouth opening should be unstrained and appear as a vertical movement with no deviation/deflection from the midline. Attempts at protrusive movement should, as well, be unstrained and free from any lateral movement from the vertical midline. Attempts at lateral movement should be unstrained and free from attempts on the part of the patient to open the mouth in order to achieve lateral movement.
Deviation is defined as movement of the mandible away from the midline during opening and/or protrusion without return to center during the movement. Deflection is defined as movement of the mandible away from midline followed by a return to center. As with limited range of motion deviation and deflection may be the result of muscular, neuromuscular or mechanical factors. As previously stated, muscular/neuromuscular influences may be modified with massage, physiotherapy and p.n.f , while mechanical factors are minimally modifiable and produce more of a repetitive, identical or similar pattern.
Joint mediated deviation may indicate disc dislocation (anterior/medial), capsular adhesion or ankylosis. The deviation will occur to the side of the pathology ("the chin will point to the problem"). Deviation to the same side during mouth opening and protrusion is virtually pathognomonic of a mechanical dysfunction on the side of the deviation.
Mandibular deviation has been documented in the nonsymptomatic population (39). Incidental findings of mandibular deviation without related symptoms (local or peripheral) are generally monitored rather than treated. If this finding arises or develops during the continuum of symptoms following trauma and is associated with limited opening and protrusion, it signals the possibility of a serious joint pathology/injury. This condition is unlikely to remit spontaneously and very well may fail conservative management. A second opinion with an oral and maxillofacial surgeon is suggested for temporomandibular joint injury when symptoms are coupled with mandibular deviation and/or signs of locking. This is especially important now that minimally invasive arthroscopic surgical techniques are available and have proven to be effective for these conditions (42, 68, 71, 105). The more aggressive surgical intervention of arthrotomy has also been shown to be effective for advanced therapy resistant joint-specific disorders (119).
Mandibular deflection may result from disc displacement with reduction and/or muscular influences. Disc displacement may or may not be accompanied by adhesive restriction of disc mobility. The more repetitive and non-modifiable the deflection pattern the more likely that it results from disc displacement and that the disc is adhesively restricted and possibly morphologically altered. This condition may be unilateral or bilateral.
Two basic deflection patterns are seen. The first is termed a "C" type deflection and indicates a unilateral disc displacement on the side of deflection. This would indicate that while the disc is displaced forward of the condyle and may be adhesively restricted from translation in the superior joint space, it is not folded or dysmorphic enough to prevent full condylar translation. During mouth opening the chin will move to the side of the displacement and then return to center. The other major deflection pattern is termed an "S" or "Z" type of deflection indicating a bilateral displacement. This type of deflection pattern occurs when both discs are displaced forward, one more than the other (the second deflection indicates the more anteriorly displaced disc). If both discs are equally dislocated or displaced there may be no deviation or deflection, but rather limited mouth opening at 26 to 32 mm of opening (bilateral disc dislocation) or simultaneous clicking/popping in the temporomandibular joints bilaterally (bilateral disc displacement).
Deflections are frequently associated with joint noises such as clicking/popping in the temporomandibular joints. The noise will usually occur at the apex of the deflection on the side of the displaced disc. It should be kept in mind that the disc may be ideally positioned (not displaced), but adhesively restricted. This can result in altered disc dynamics with deflection toward and clicking/ popping in the involved joint. In cases where clicking and deflection are caused by joint pathology other than disc displacement, conflict between clinical exam findings and an MRI of the joint(s) may result. (See special tests section).
AUSCULTATIONTemporomandibular joint noises were once considered almost pathognomonic of temporomandibular disorders. New thought has led us to believe, however, that many joint noises present with mandibular movement may be part of the natural history of asymptomatic joints (83). These noises may be the result of remodeling and accommodation processes which take place over time or the result of specific architectural predispositions such as superior/posterior condyle positioning. Clicking in the temporomandibular joints has been identified in greater than 40% of the asymptomatic population (39). Any joint noises arising or increasing within three months of trauma, such as whiplash, and/or which are associated with continuing symptoms should be considered important (107). Joint noises do not identify the presence of a temporomandibular disorder, but help to classify the type of disorder when symptoms are present (52).
Auscultation of the temporomandibular joints can be performed with light digital palpation or use of a stethoscope. Joint vibration analysis (JVA) machines are sometimes used to record joint noises. These machines can accurately record many characteristics of temporomandibular joint noises (45, 46). The data gained from JVA needs to be interpreted in light of the history and entire clinical exam however before an accurate diagnosis can be made.
During the standard TMD examination the doctor should place the stethoscope and/or the finger tips of the second and third digits lightly over the lateral poles of the temporomandibular joints. This contact should be no heavier than light skin contact to preclude putting pressure on the lateral poles of these joints. The doctor instructs the patient to fully open and then close the mouth. The patient is then subsequently instructed to protrude, retrude and laterotrude the mandible. Various joint noises may be heard and should be recorded. Joint noises are usually referred to as clicking, popping and crepitus. Clicking/popping in the temporomandibular joints which occurs within the normal range of motion (less than 40 to 50 mm) most frequently occurs as a result of disc displacement and/or adhesions. This second cause (adhesions) is important to remember because it clinically mimics disc displacement, but may be interpreted as a normal joint on an MRI (see special tests). Persistent joint noise coupled with continued symptoms and joint tenderness is an important clinical finding whether it results from disc displacement or adhesions. Clicking/popping in the temporomandibular joints is often thought to occur as a result of "spasm" or incoordination of the superior heads of the external pterygoids. This is very unlikely however as research has shown that this muscle has little or no mechanical advantage over the disc (5). Intermittent clicking which seems stress/clenching related is more likely due to hypertonicity of the elevator muscles during joint movements. The strong possibility of concurrent disc complex instability, adhesions and/or disc displacement exists in these cases.
You may notice that deflection is present without clicking during the examination. While this may be a muscular affect, you should challenge this finding by modifying your examination procedure. To do this, lightly grasp the chin and guide the mandible through a straighter course of opening and protrusion. Muscular influences on deflection are minimized then and clicking/popping and even intermittent locking may be observed.
Clicking and deflection are usually coordinated manifestations of the same event, i.e. discal and/or adhesive interference with condylar translation. As such, uncomplicated clicking usually occurs at the apex of mandibular deflection toward the involved joint. Variations on this theme may occur, however. The most important of these is encountered when deviation to one side is accompanied by clicking on the opposite side. The doctor may misinterpret this clicking as indicative of the primary problem, especially as this may be the more painful side. It is the side toward which the mandible deviates which is more profoundly deranged, however, especially if deviation occurs during both protrusion and mouth opening lack of treatment of the side toward which the mandible deviates will undermine any attempt to treat the side productive of the clicking.
Crepitus may be detected during auscultation. This is described as a "ground glass" sound and signals the possibility of discal or, more commonly, retrodiscal perforation (43). If this is present in a symptomatic joint, it identifies an advanced problem which may prove difficult to manage even with surgical techniques. While conservative care is appropriate and may prove successful, early referral for surgical consultation is recommended if clear and steady progress is not achieved. Crepitus may or may not be associated with deflection, deviation and/or decreased range of motion. As with clicking, crepitus may be present without symptoms if there is no associated inflammation. These cases are generally monitored rather than treated unless there is a report of shift in facial contour or occlusion. If alteration of facial contour and/or a shift in occlusion is reported by the patient, they should always be referred for an expert opinion.
Noises described as popping or clunking may occur at the widest point of mouth opening (generally 50+mm). These sounds occur as the condyle passes over the temporal eminence. This indicates joint hypermobility. This may be a manifestation of general ligament laxity or of local ligament damage/degradation. This hypermobility is clinically more significant if the temporal eminence is steep (like a vertical wall). Temporomandibular joint hypermobility has been observed in the asymptomatic population. Coupled with symptoms however it calls for strict patient compliance with instructions to limit full mouth opening. If hyper-translation is allowed to continue after inflammation has begun, substantial joint damage and even non-reducing joint dislocation may occur as pathology progresses.
As a final point in this section the issue of the "posterior disc" should be addressed. This was a popular concept before accurate imaging techniques alerted us to the prevalence of the anterior/medial disc displacement. As it turns out the posterior disc is a very uncommon occurrence and when it is observed it is usually a transient position which occurs during functional mandibular movements. That is, if the disc is prevented from translating by adhesions in the superior joint space, the condyle may click onto and past the disc causing a momentary posterior disc positioning. In these cases generally the closing click is louder than the opening click. This finding implies that not only is the disc non-mobile, but that the collateral attachments of the disc to the condyle are weakened allowing the condyle to move both forward of and posterior to the disc during these respective condylar movements. In contrast to this, the anteriorly displaced disc that is not adhesively restricted and has intact collateral attachments presents almost invariably with an opening click that is louder than the closing click (the closing click may in fact be inaudible). The dysfunctional posterior disc phenomenon may also occur secondary to changes in disc shape. In our experience patients presenting with a dominant closing click have a poor prognosis for success with conservative care. While conservative care may be tried and very well may succeed, there is no scenario in which thrusting the mandible in an A-P direction to seat the condyle under a posterior disc is appropriate.
PALPATIONPalpation is perhaps the most undervalued and misunderstood of the TMD exam procedures. Palpation findings for muscles, joints, ligaments and tendons are often considered equally reliable or unreliable and lumped under the heading of "subjective" data. In fact, with regards to muscles and joints, inter-examiner and serial intra-examiner reliability is different for each tissue. This includes studies of the cervical, lumbar and masticatory regions (19, 44, 60,90).
The effectiveness of palpation for differentiating patients from non-patients has not been thoroughly validated. The following statements represent the reliable information derived from skilled palpation:
Cervical and/or masticatory muscle tenderness is not a reliable indicator of local muscle pathology as tenderness may represent the affect of a CNS process stimulated by peripheral pathology (90, 105, 115).
In a patient population tenderness over the lateral poles of the condyles identifies capsular inflammation accurately especially if the tenderness is equal to or greater than 2 on a 0 to 3 scale and the condyles are as tender or more tender than the ipsilateral masseter and temporalis musculature (105).
Palpation of the lateral and posterior capsule of the temporomandibular joint with an algometer shows acceptable inter and intra-examiner reliability and can identify patients from non-patients (13).
Females report temporomandibular joint capsule pain at a lower pain pressure threshold than males when tested by algometer (13).
Many difficult questions are now being asked which challenge our ideas about myofascial disorders. In the field of TMD this is very troublesome as a "myofascial" diagnosis is one of the most commonly assigned in clinical practice. Results from four surgical studies and two temporomandibular joint anesthetic injection studies challenge the idea that we can identify myogenous disorders exclusively by the presence of muscular tenderness to palpation. These studies have demonstrated remission of both masticatory and cervical myofascial tenderness when the temporomandibular joints are injected with an anesthetic and/or operated (17, 68, 70, 105, 113). This is not to say that all myofascial presentations are driven by joint inflammation, but rather that muscle tenderness alone cannot rule in a true primary myogenous disorder, cannot rule out an arthrogenous disorder and cannot rule in a mixed arthrogenous/ myogenous disorder as the arthrogenous disorder is capable of driving the entire muscular component (105). Joint tenderness as an isolated finding may not be an accurate inclusionary factor for symptomatic capsulitis as it has been noted that joint receptor discharge increases with muscle activity (66). In fact, comparing locations, patterns and relative degrees of tenderness in the muscles and joints of the head and neck may give us the most useful diagnostic impression (105). It should be noted that the presence of cervical muscle tenderness in patients expressing symptoms in the head and neck has been identified as indicating a high probability of TMD (40, 109, 115).
Palpation of the masticatory and cervical/upper shoulder regions is necessary and important in the TMD examination. These tests are necessary to satisfy the demands of standard of care and can provide useful information in the following ways. First, identification of trigger points and muscle hypertonicity provides targets for treatment in true non-arthrogenous myofascial conditions (112). Second, certain patterns of muscle tenderness and hypertonicity can be informative diagnostically when temporomandibular joint tenderness is present concurrently (105). Third, when temporomandibular joint pathology is suspected of being the driving force behind the symptoms, specific areas of muscle tenderness and hypertonicity can serve as target areas for anesthetic temporomandibular joint injections and/or joint-specific treatment trials (17, 105, 107).
TEMPOROMANDIBULAR JOINT PALPATION - TECHNIQUETo palpate the temporomandibular joints most effectively have the patient move the chin to the side opposite the joint palpated. When the joint is palpated with the teeth together or the mandible at rest there is approximately 5-10 min of tissue between your finger and the joint capsule. Having the patient maneuver the chin to the opposite side will surface the condyle for more accurate palpation.
Palpate the condyle with three to five pounds of pressure.
Palpate the entire condyle accessible to you as the lateral capsule is complex and certain areas may be tender while others remain nontender. Any tender areas of the capsule should be recorded.