Osteoarthrosis of the tempo-romandibular joint. A clinical and radiological study of 16 patients

MARTÍNEZ BLANCO M, BAGÁN JV, FONS A, POVEDA-RODA R. OSTEOARTHROSIS OF THE TEMPOROMANDIBULAR
JOINT. A CLINICAL AND ND RADIOLOGICAL STUDY OF 16 PATIENTS. MED ORAL 2004;9:106-15.

SUMMARY

A study is made of the clinical and radiological characteristics of 16 patients with osteoarthrosis (OA) of the temporo-mandibular joint (TMJ). The study comprised those patients satisfying the diagnostic criteria for OA proposed by Stegenga et al. in 1989. The patients were subjected to a clinical and radiological diagnostic protocol (including the obtainment of magnetic resonance imaging data).
The most relevant clinical findings were the detection of crepitants in 93.8% of cases, with a reduction in mandibular movement range. Radiology in turn identified joint surface alterations in 62% of cases on the right side, and in 68.8% of the patients on the left side. The joint disc dynamic position study showed anterior displacement without reduction in 50% of cases in the right joint and in 43.8% of patients in the left joint.
In conclusion, patients with OA of the TMJ present joint sounds and a reduced mandibular movement range - the salient radiological characteristic being altered joint morphology.

Key words: Osteoarthrosis, temporomandibular joint.

INTRODUCTION

Arthrosis or osteoarthrosis (OA) is a degenerative disorder and the most common non-inflammatory disease of the joints (1-3). OA is characterized by three phenomena (4): destruction of the joint surface cartilage; bone remodeling with neoformative phenomena (osteophytes); and bone rarefaction (subchondral cyst formation) with secondary synovitis. These three processes may vary in intensity, and while bone destruction and remodeling is often asymptomatic, in other cases it may generate important symptoms (5). Of the patients treated for temporomandibular joint (TMJ) dysfunction (TMJD), 8-12% are diagnosed with OA (6-9). The prevalence increases with age, and after age 65 OA affects all individuals to one degree or other (1). Autopsy-based studies have shown 22-40% of the population to have OA, which in many cases failed to produce symptoms (10). On the other hand, some series have found the disease to be 6 times more common in women than in men. In turn, one or both TMJs can be affected simultaneously (6,7,1-13).

The pathogenesis of OA of the TMJ has been related to different factors:

(a) Evolution of the disease and patient age. A strong association is observed between increased OA incidence and patient age. In this sense, infrastructural changes develop in the joints with age (1,6,7,11-13), and although the pathogenic relation between age and OA is unclear, the changes in the joint tissues caused by age could affect their mechanical properties and facilitate the development of OA.

(b) Joint overload. This may be produced by parafunctional habits, occlusal interferences, malocclusions and tooth loss (13), with a loss of the normal joint tissue adaptation capacity - giving rise to fracture of the cartilage responsible for resisting the different compression forces to which the TMJ is exposed (14,15).

(c) Internal derangement of the TMJ. In a radiological study, Westerson (16) demonstrated the existence of a relation between anterior disc displacement without reduction and articular bony changes. An association has also been found between joint disc perforation and degenerative disease (17-19).

(d) Microtraumatisms. Sudden forces applied to the region of the TMJ (e.g., a blow to the chin) can induce degenerative changes in the joint (1,20).

In general, any type of joint disorder can ultimately lead to OA of the TMJ (1). Upon clinical exploration, patients with OA of the TMJ present limited mandibular movement, and a soft end-feel is often present, unless OA is associated with anterior disc luxation. In general, the affected patient presents joint crepitation upon auscultation of the TMJ, particularly if the disorder has been present for some time. Lateral palpation of the condyle and masticatory muscles is usually painful, as is manual loading of the joint (2,21,222).

The possible radiological changes in turn comprise erosion, sclerosis and leveling (affecting both the condyle and joint eminence), with the formation of osteophytes evidenced as overgrowth of the marginal bone, and the appearance of subchondral cysts (seen as concavities in the bone) (22,23).

Different evolutive stages have been proposed in application to mandibular OA. Accordingly, in an initial stage OA is difficult to distinguish from other TMJ disorders. In an intermediate stage TMJ pain develops, and in the terminal stages of the disease the symptoms subside and function normalizes - with radiological evidence of increased bone degeneration and an increased frequency of meniscal perforation (24,25).

In order for a patient to be diagnosed with OA of the TMJ, the following criteria must be met (26): the existence of crepitants upon auscultation of the joint; limited mandibular mobility with deviation to the affected side upon opening the mouth; and the existence of radiological evidence of structural bone modifications. Furthermore, other authors such as Clark et al. (27) consider it necessary to determine the dynamic position of the disc in order to establish a definitive diagnosis.

The aim of the present study is to determine the presence of possible etiological factors related to the appearance of OA of the TMJ and describe the clinical and radiological characteristics of the affected patients.

MATERIAL AND METHODS

The present study involved 16 patients seen in the Service of Stomatology (Valencia University General Hospital. Valencia, Spain) between October 1999 and December 2000. Following a preliminary evaluation, the inclusion criteria comprised two conditions: (a) Limitation of mandibular movement, regarding as pathological a maximum aperture of under 35 mm in males and 30 mm in females, with pathological latero-propulsion being defined as less than 7 mm (according to Kaplan, as cited by Bermejo)(27,28); (b) Crepitation (or antecedents of such sounds) at TMJ auscultation. Crepitation is defined as a diffuse and sustained sound perceived as a "gravel"-like or "crackling" effect in the joint (29-31).

Of the 16 patients studied, all but one were women (93.8%). The mean age was 46.6 years (range 23-67)(standard deviation 12.74; standard error of the mean 3.18). Informed consent to participation in the study was obtained in all cases. The demographic data were collected, and the patients were questioned about their reasons for seeking medical care and the duration of the disorder. The possible existence of parafunctional habits was documented, as well as patient emotional status. The subjects were likewise questioned about possible sleep disorders and the quality of sleep, since some authors have related pain syndromes with the quality of sleep (29,30,32). Posteriorly, in the dental chair, the following explorations were carried out:

- Facial and mandibular inspection, in search of asymmetries, with examination of the TMJs.

- Palpation of the TMJs and masticatory muscles. TMJ pain was assessed by digital palpation of the joints both with the jaw in the resting position and during dynamic movement.

- Joint sound auscultation by placing a stethoscope over the joint region, registering the character of the sounds and determining whether they were generated during oral aperture or closing, or whether they were produced during both mandibular movements (reciprocal clicks).

- Relaxed mandibular manipulation of the patient, in order to assess the elasticity of the soft tissues and determine the presence or absence of pain.

- Mandibular movements, using calipers and recording the range of movement at mandibular aperture, right laterality, left laterality, propulsion, and the resting mandibular space. Hard or soft end-feel was also recorded, together with the absence or presence of pain.

- Evaluation of occlusion, recording the corresponding Angle class, the existence of wear surfaces, occlusal interferences and the presence of prematureness and missing teeth.

Two radiological studies were requested for each patient: (a) Orthopantomography in which only the joint regions were visualized; (b) Maxillofacial magnetic resonance imaging (MRI) at TMJ level, assessing condylar and joint eminence morphology, the presence of erosions, sclerosis, leveling, osteophytes and/or subchondral cysts affecting the mandibular condyle and/or articular eminence, and ATM disc position during mandibular aperture and closure.

The results obtained were analyzed with the SPSS version 10.0 statistical package, comprising a descriptive study involving the arithmetic mean, standard deviation (SD) and standard error of the mean (s.e.m.) for the continuous quantitative variables, and frequency and percentage tables for the discrete qualitative and quantitative variables.

RESULTS

On analyzing the local factors related to OA, 25% of the participating patients were seen to be totally edentulous, 62.6% presented missing teeth in either the anterior or posterior sectors, and only 12.5% retained all their teeth. Of the 16 subjects evaluated, 10 (62.5%) referred some type of parafunctional habit. As to the contribution of occlusion, 10 of the 16 patients (62.5%) presented occlusal interferences, and 8 (50%) showed wear surfaces as a result of such occlusal interferences, or secondary to parafunctional habits.

In relation to the general factors, three of the 16 patients (18.8%) suffered arthrosis of other joints, and two (12.5%) presented osteoporosis. As to the evaluation of emotional tension, 8 subjects (50%) referred stressful living conditions. The evaluation of sleep alterations in turn showed 8 individuals (50%) to suffer disturbances in sleep quality or quantity.

The duration of symptoms was under one year in 5 of the 16 subjects (31.3%). In another 5 cases (31.3%) the duration was between 1-2 years, and in the remaining 6 (37.6%) symptoms duration totaled over two years.

On palpating the TMJ, 5 patients (31.3%) referred pain in the right joint, versus 6 (37.6%) in the left. Table 1 shows the absolute and percentage values corresponding to the number of patients referring pain in response to palpation of each of the masticatory muscles. Of note is the fact that most patients referred pain upon palpation of the medial as well as lateral pterygoid muscles.

Auscultation revealed right TMJ crepitation in 93.8% of the patients, versus left TMJ crepitants in 87.5%. One patient presented clicks on the right side, while in two patients (12.5%) TMJ auscultation proved normal.

In relation to the range of mandibular movement, the 16 patients with mandibular OA showed an average mandibular aperture of 32 mm (range 10-50 mm; SD 9.5, s.e.m. 2.38). In turn, mean right and left laterality was 4.69 mm (range 3-10 mm; SD 1.92, s.e.m. 0.48) and 5.13 mm (range 2-10 mm; SD 2.31, s.e.m. 0.58), respectively. Of the 16 patients studied, the mean protrusion movement range was 3 mm (range 1-6 mm; SD 1.32, s.e.m. 0.3).

The radiological study revealed the existence of morphological alterations in 62.5% of the cases on the right side, versus in 68.7% on the left. One patient also presented left condylar erosion, while four suffered joint surface sclerosis and 7 presented osteophytes. One-half of the study subjects showed joint surface leveling.

Finally, dynamic joint disc evaluation showed half of the patients to present anterior disc displacement without reduction on the right side, versus 43.8% on the left side. Disc perforation was diagnosed in one patient.

DISCUSSION

The prevalence of osteoarthrosis of the temporomandibular joint varies from 22-38% of the population in the 20-90 years age range. It has been found that signs of OA may be present in up to 80% of the population in the 60-80 years age interval, though such signs can also be identified in 3% of individuals under age 40 (33). In the present study the mean patient age was 46.6 years (range 23-67), in agreement with the observations of other authors. On the other hand, Boering (34) identified radiological alterations in 86% of the subjects under age 20 - though most of these changes disappeared over time, probably as a result of remodeling associated with growth and repair capacity. In turn, Wildman (35) studied the prevalence of OA in young patients with TMJ dysfunction, observing osteoarthrotic changes in 66% of the subjects. Recent autopsy studies involving young adults (under age 40) and older individuals (over age 40) have shown only 4% of the joints among the younger subjects to present signs of OA, versus 22% in the older group (36).

OA of the TMJ is a degenerative process involving impairment of joint tissue adaptive capacity under conditions of increased stress, due to the intervention of both local and systemic factors. Different authors (37,38) indicate that joint overload produced by parafunctional masticatory activity can induce adaptive changes in the TMJs, and that such adaptive phenomena may fail, giving rise to OA. In our study, of the 16 participating subjects, 10 (62.5%) referred some type of parafunctional habit. Capurso (38), in a study of 406 patients with signs and symptoms of TMJ disorders, concluded that bruxism was present in 35.9% of cases. Allen et al. (39) in turn investigated 569 patients over a 10-year period, reaching the conclusion that parafunctionalism is effectively related to pain in the temporomandibular region. Rugh and Harlan (40) reviewed the effects of bruxism upon the TMJs, and concluded that this parafunctional habit can cause important damage to any part of the masticatory apparatus.

As to the contribution of occlusion, Selligman and Pullinger (41), based on epidemiological data, demonstrated the association between occlusal factors and OA of the TMJ. In our series, occlusal analysis showed 10 of the 16 patients (62.5%) to have occlusal interferences, and in 8 of them (50%) wear surfaces were identified as a result of these occlusal interferences or the referred parafunctional habits. In the present study, 25% of the patients were edentulous, while 62.6% had missing teeth in the anterior or posterior sectors, and only 12.5% retained all their teeth. These observations could support the theory of authors such as Oberg, who consider that partial or complete edentulous status can constitute one of the etiological factors of OA of the TMJ - due to the adverse biomechanical loading involved. This correlation has not been confirmed, however (11).

Regarding the systemic factors underlying OA of the TMJ, of the 16 patients in our series three (18.8%) suffered arthrosis in other locations, and two (12.5%) had osteoporosis. Their joint problems could therefore be related to the observed systemic disorders - though a review of the literature yielded no analysis of this possible relationship. On the other hand, emotional tension can influence the functional alterations of the masticatory system (30). In this context, 8 of our patients (50%) referred stress. The amount and quality of sleep may also be related to certain forms of TMJ dysfunction, as demonstrated by Moldofsky (29,30) in patients with fibrositis, and by Molony (32) in subjects with fibromyalgia. In our series of patients sleep disorders were documented in 50% of cases - though no data are found in the literature relating OA of the TMJ to sleep disorders.

On analyzing the data obtained from the clinical exploration regarding the duration of the symptoms, 5 of our patients (31.3%) referred a duration of under one year, while the 11 remaining subjects (68.8%) had suffered symptoms for longer periods of time. According to Okeson (21), the symptoms usually describe a standard Gaussian-like curve, with increasing severity in the first 4-7 months, followed by leveling 8-9 months after symptoms onset, and an ultimate reduction after between 10-12 months. However, the duration of the evolution from one stage to another varies among patients according to the underlying etiological factors and the individual tissue adaptation capacity. This is why in our patients emphasis was placed on the control of those factors which could be implicated in the initiation and development of symptoms (parafunctional habits, occlusal interferences, missing teeth, etc.). Other authors such as Berret (42) consider that a part of the population presents asymptomatic OA. However, in our series all 16 patients referred some symptoms during the course of the disease.

Upon palpation of the TMJs, 31.3% of the patients referred pain on the right side, versus 37.5% on the left side. The appearance of joint capsular pain has been described as one of the symptoms which appear in OA of the TMJ (6,43,44). In this sense, one of the possible causes of joint pain is joint structural deterioration. Consequently, it may be postulated that patients without pain do not yet present important joint surface deterioration.

On palpating the muscles associated with the TMJ, both the medial and lateral pterygoid muscles, and particularly the latter, were the muscles most often affected in our series of patients. In this sense, pain of the masticatory muscles is one of the clinical symptoms present in OA of the TMJ (2,21,22,25,44), and the observation that the lateral pterygoid muscles were the most affected could be explained by the fact that these muscles insert in the joint capsule - as a result of which their function may be expected to be more directly altered as a result of joint deterioration.

Joint auscultation showed 93.8% of the patients to generate crepitants in the right TMJ, versus 87.5% in the left joint. The presence of such joint crepitation, either at the time of exploration or at some other point in the course of the disease, constitutes one of the diagnostic criteria of OA (26,43,44). In this context, crepitation is a predictive sign of TMJ osteoarthrosis (44,45). In the study published by Rohlin et al. (46), 10 of 12 joints with crepitants had suffered degenerative changes, while the remaining two showed important remodeling.

The presence of limitations in mandibular movement - detected in all of our patients - in relation to the degree of aperture and/or the extent of eccentric excursions, is likewise a diagnostic criterion of OA of the TMJ (26,43,44).

The radiological study showed the presence of morphological alterations of the joint surfaces in 62.5% of cases on the right side and in 68.7% on the left. All the radiological findings in our series coincide with those referred by different authors in relation to OA of the TMJ (22,23,47,48). However, some investigators (47,49) consider it difficult - when not impossible - to radiologically distinguish between a degenerative process and adaptive remodeling. In this sense, joint surface leveling can be associated with subchondral sclerosis independent of arthrosis, effectively responding to an adaptive response to increased joint loading.

The position of the joint disc has also been related to OA of the TMJ. Westesson (50) conducted a radiological study comprising 128 patients with internal derangement of the TMJ. Bone changes were found to be present in 50% of the patients with anterior disc displacement without reduction. This coincides with our own findings, where half of the series of patients presented anterior disc displacement without reduction on the right side versus 43.8% on the left, while one patient suffered disc perforation. Anderson and Katzberg (51) obtained comparable results in a study of 141 patients where only 9% with anterior luxation reduction showed signs of degeneration, while 39% of those without reduction and 60% of the subjects with disc perforation presented degeneration.

In conclusion, osteoarthrosis of the TMJ is more frequent in females than in males. The most common local etiological factors were found to be joint overload induced by parafunctional habits, missing teeth and occlusal interferences. No systemic factor could be identified in our setting in relation to the etiology of OA of the TMJ. One-half of the patients referred emotional stress. Clinically, and regardless of the symptomatology, all patients presented joint crepitation upon auscultation, with a reduction in the range of mandibular movement - either at the time of the study or at some other point during the course of the disease. The salient radiological feature was altered joint morphology and the presence of anterior disc displacement without reduction.

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