Anatomic disorders of the temporomandibular joint disc in asymptomatic subjects

J Oral Maxillofac Surg 5x4:147-153, 1996

Anatomic Disorders of the Temporomandibular Joint Disc in Asymp toma tic Subjects RICHARD W. KATZBERG, ROSS H. TALLENTS,

MD,* PER-LENNART WESTESSON, DDS, PHD,“I DDS,$ AND CHRISTIANA M. DRAKE, PHD$j

Purpose: This study determined the prevalence and specific anatomic types of disc displacement in asymptomatic versus symptomatic subjects using magnetic resonance imaging (MRI). Patients and Methods: A detailed MRI assessment was performed on both temporomandibular joints (TMJ) in 76 volunteers and 102 successive patients. Attention was placed on the functional aspects of disc displacement with and without reduction and on the anatomic aspects of disc displacement in the anterior, lateral, medial, anterolateral, and anteromedial directions. These assessments were made by radiologists blinded to the clinical information. Results: Disc displacement was found in at least one joint in 25 of 76 (33%) of asymptomatic subjects and 79 of 102 (77%) of symptomatic subjects. The anatomic types of disc displacement between groups was not statistically significant (P = 55). However, there was a significant difference between asymptomatic and symptomatic subjects, with an odds ratio of 3.91 for disc displacement with reduction and 42.71 for disc displacement without reduction (P < .OOl). Conclusion: Although there was a 33% prevalence of disc displacement in asymptomatic volunteers, there was a highly significant difference in the prevalence of internal derangement in symptomatic subjects. Bruxing was statistically linked to TMJ disc displacement and could explain the anatomic variation in abnormal disc position.

internal derangement in up to 32% of joints.‘-5 However, only the most recent reported investigation, suggesting a prevalence of internal derangement in 21% of asymptomatic subjects, evaluated rotational and sideways disc displacement.5 The purpose of this investigation is to compare the relationship between the signs and symptoms of TMJ diseaseand a detailed MRI assessmentof the presence or absenceof disc displacement in 76 volunteers and 102 successive patients. Attention was placed on the functional aspectsof disc displacement with and without reduction and on the anatomic aspectsof disc displacement in the anterior, lateral, medial, anterolateral, and anteromedial directions.

Internal derangement of the temporomandibular joint (TMJ) related to functional and anatomic abnormalities has been demonstrated in some asymptomatic subjects. Previous studies using either arthrography or magnetic resonance imaging (MRI) with high-resolution surface coils have shown a range of asymptomatic * Professor and Chair, Department of Radiology, University of California Davis Medical Center, Sacramento, CA. t Professor, Department of Radiology, University of Rochester, School of Medicine and Dentistry, Rochester, NY. $ Associate Clinical Professor, Eastman Dental Center, Rochester, NY. $ Associate Professor, Division of Statistics, University of California Davis, Davis, CA. Supported by Grant DE 08059 from the National Institutes of Health, Bethesda, MD. Address correspondence and reprint requests to Dr. Katzberg: Department of Radiology, University of California Davis Medical Center, 2525 Stockton Blvd, MSF Building, Sacramento, CA 95817. 0 1996 American

Association

of Oral and Maxillofacial

Methods VOLUNTEER

SUBJECTS AND PATIENTS

Seventy-six asymptomatic volunteers, without gender bias in selection, were recruited from the Roches-

Surgeons

0278-2391/96/5402-0003$3,00/O

147

148

ANATOMIC DISORDERS OF THE TMD

ter, New York, area and were examined by one of the authors (R.H.T.) and a TMJ fellow for signs or symptoms of TMJ disease. Of these 76 subjects, 39 were women and 37 were men. The mean age was 28.3 & 6.7 (standard deviation), with a range of 19 to 49 years. A complete head and neck physical examination and detailed oral examination were performed, and any subjects with a history of TMJ pain or physical signs of clicking, locking, or tenderness in or around the TMJ were excluded. One hundred two successive, prospectively selected, patients presenting to the Eastman Dental Center TMJ Clinic for evaluation of possible TMJ disease were selected for the same detailed clinical assessment as the volunteers. Of these 102 subjects, 90 were female and 12 were male. The mean age was 29.9 +- 10.7 years, with a range of 10 to 66 years. The same clinicians who evaluated the volunteers also evaluated the patient group. Patients included in the study had either a clicking, locking, or crepitus as well as TMJ pain. The volunteer subjects gave informed written consent for the study as approved by The Human Investigation Committee of the University of Rochester. MRI SCANSOFTHE TMJ A detailed MRI assessment of each pair of TMJs in all subjects was performed with a 1.5-tesla MRI system (Signa scanner, General Electric Medical Systems, Milwaukee, WI), using bilateral high-resolution 6 x 8-cm rectangular surface coils with the jaw first in the closed, rest position and then at the maximal opened position capable by the patient.6.7 An initial axial localizer with a 52-second scanning time was performed with a repetition time (TR) of 400 msec, an echo time (TE) of 16 msec, a field of view of 18 cm, a slice thickness of 3 mm, and a 256 x 128 scanning matrix. These images were acquired to protocol bilateral orthogonal sagittal planes of both TMJs in the closed jaw position, using a TR of 2,000 msec, TEs of 19.80 msec, 3-mm image slice thicknesses, field of view of 10 cm, and a scanning matrix of 256 X 192. These were followed by bilateral sagittal plane open-jaw images with a TR of 1,500 msec, and TEs of 1,980 msec. The final imaging sequence was with the jaw closed and acquired coronal images of both TMJs with a TR of 2,000 msec, and TEs of 1,980 msec. The MRI studies were independently assessed by two readers blinded as to the clinical information and using established criteria for normal disc position versus disc displacement. Normal disc position was defined as the posterior band of the disc being located at the superior or 12 o’clock position relative to the condye.‘-” Primary categories of the status of the joint that were also assessed and tabulated were 1) normal disc position; 2) disc displacement with reduction; and

3) disc displacement without reduction. After the readers had made independent assessments of the status of the joint, disagreements were resolved by conference. Disc displacement was also more specifically defined as the posterior band of the disc being in an anterior, anteromedial, anterolateral, medial, or lateral position relative to the superior part of the condyle as the reference point. ” CLINICAL ASSESSMENTOF TMJ PAIN AND DYSFUNCTION Clinical signs that were assessed and tabulated included the presence of clicking and its characteristics during opening and closing joint maneuvers; the presence of jaw locking either in the closed or opened positions, and the relationship to range of motion determinations; and the presence of joint crepitus. Symptoms such as unilateral or bilateral TMJ pain, unilateral or bilateral ear pain, generalized, frontal, or temporal headache, and neck pain were tabulated. The physical evaluation, based on that described by Helkimo, and involving a detailed examination of the clinical features associated with TMJ dysfunction, was used.‘4’15 The presence of joint sounds was assessed by placing a stethoscope on the skin anterior to the tragus overlying the condyle. The patient was then instructed to open and close the jaw slowly. Clicking was defined as a single distinct sound emitted from the joint during either the opening or closing jaw movement. Crepitation was defined as multiple scraping or grating sounds emitted from the joint during opening or closing.6 Salient historical features included inquiry regarding a history of clicking, crepitus, open- or closed-jaw locking, or trauma to the joint. Muscles of the head and neck related to mastication or muscle tension were palpated. These included the temporalis, sternocleidomastoid, both the superficial and deep portions of the masseter muscle, the insertion of the medial pterygoid muscle, and the insertion of the temporal tendon onto the coronoid process. All of the areas examined were recorded as being either tender or nontender to palpation. The range of mandibular movement was measured and tabulated in millimeters using the method described by Agerberg.16 Mouth opening was assessed using a gauge graded in millimeters. The maximal opening of the mouth was calculated by adding the maximum interincisal distance to the amount of the vertical open bite. To measure the maximal right and left lateral movement, a vertical mark was drawn with a wax pencil in the median plane on the labial surfaces of two opposing incisors. The patient was then asked to open the mouth until the teeth were slightly separated and move the lower jaw to the right and then to the left.

149

KATZBERG

ET AL

Table

Comparison

1.

of Volunteers

Patients

One or Both Joints Having Disc Displacement With Reduction Only

No Abnormality Patients (n = 102) Volunteers (n = 76) Odds ratio

Versus

for Presence

of Disease

Disc Displacement With Reduction on One Side and Without Reduction on the Other Side

One or Both Joints Having Disc Displacement Without Reduction Only

23

41

18

20

51

23 3.91

1 38.45

1 42.71

NOTE. P < .OOl, test for trend.

The amount of wear to the anterior and posterior teeth, as an index of bruxing, was assessedand recorded using a scale described by Hansson and Nilner.17 The occlusion was classified based on the system established by Angle.‘* STATISTICAL

ASSESSMENT

The subject was used as the unit of observation for statistical analysis. All subjects having abnormalities were tabulated as occurring in either the right only, left only, or both joints. Because of the complexity of the data set, somesymptoms and causative factors were side specific, and others were specific to the subject. To achieve interpretable measuresof association, separate stepwise logistic regressions were performed for abnormalities in the left and right TMJs.19 The outcome variable was disc displacement (present or absent). Two-tailed logistic regression analysis, both with and without adjustment for gender, was performed to determine whether patients were more likely to suffer from disc displacement than volunteers. All P values less than .05 were considered statistically significant. Results

Overall, 25 of 76 (33%) of volunteers, 16 females and 9 males (approximate ratio, 2:1), and 79 of 102 (77%) of patients, 72 females and 7 males (approximate ratio 10: l), had at least one abnormal TMJ (Table 1). Of the subjectswith abnormalities, bilateral internal derangement was noted in 11 of 76 (14%) of the volunteers and 52 of 102 (51%) of the patients. Disc displacement without reduction (Fig lA, B, C) in at least one TMJ was noted in 2 of 76 of volunteers (2.6%) versus 38 of 102 (37%) of patients. Disc displacement with reduction, was found in on one or both sides 23 of 76 (30%) of volunteers (Fig 2A, B) versus 41 of 102 (40%) of patients. Subject groups were categorized emphasizing disc displacement with reduction versus disc displacement without reduction to determine if there was a hierarchy of disease stage. The test for trend showed an odds ratio of 3.91 (95% confidence

interval [CI] = 1.84, 8.55) for disc displacement with reduction on one or both sides and an odds ratio of 42.71 (95% CI = 6.12, 1,872.84) for disc displacement without reduction on one or both sides (P < .OOl). Although epidemiologic studies suggest an equal prevalence of TMJ problems in malesand females, the high ratio of female versus male patients led us to look at the possibility of confounding in the statistical analyses.‘5>1720-23 Table 2 demonstratesthe relationship between TMJ abnormality in volunteers versus patients adjusted for sex. The odds ratio for female subjects was 5.75, and the odds ratio for male subjects was 4.36. The null hypothesis that the odds ratio for females equalsthe odds ratio for males and equals 1 had a P < .Ol. This indicated that there was a relationship between symptoms and internal derangement (ie, if symptoms are present, internal derangementwas more likely to be present regardlessof sex). The null hypothesisthat sex was not a factor was rejected with a P < .05. This indicated that not adjusting for sex would suggest a stronger relationship than really existed between symptoms and internal derangement. The null hypothesis that the odds ratio for females equals that of males had a P value of < .05. This indicated that the relationship between symptoms and internal derangement was the samefor males and females. Interpretation of the MRI studiesshoweda 90.8% (323 of 356) interrater agreementfor the primary diagnosisof normal discpositionversusdisc displacementwith or witbout reduction. In the volunteer subjects,9 of 3.5(26%) of abnormaljoints showed anterior disc displacement,9 of 35 (26%) of abnormal joints showed anteromedialdisplacement (Fig lB), 3 of 35 (8.5%) of abnormaljoints showedmedial displacement;12 of 35 (34%) of abnormal joints showedanterolateraldisplacement(Fig 3A, B), and 2 of 35 (6%) of abnormaljoints showedlateral displacement. In the patient group, 54 of 103 (52%) of abnormal joints had anterior displacement,28 of 103 (27%) abnormaljoints had anteromedialdisplacement;12 of 103(12%) abnormaljoints had medial displacement;35 of 103 (34%) abnormaljoints had anterolateraldisplacement,and 4 of 103 (4%) abnormaljoints had lateral displacement.There was no difference between patients and volunteers in the

150

ANATOMIC

DISORDERS

OF

THE

TMD

FIGURE I. A, This is an MRI of the left TMJ in an asymptomatic volunteer having disc displacement without reduction, bilaterally. The disc (arrows) is noted displaced anteriorly to the condyle (c), which is flattened and deformed. Similar findings were noted on the contralateral TMJ. B, This is the coronal MRI of the same asymptomatic subject showing abnormalities of condylar shape and marrow signal associated with a medial component (arrows) to the disc displacement. C, Medial disc (arrows) on the contralateral side in coronal plane. The findings in this asymptomatic subject were of bilateral disc displacement without reduction in the anteromedial direction and with degenerative joint disease.

distribution of these anatomic types of displacements, with a P value of .55 (Fisher’s exact test). A comparison of signs and symptoms of TMJ dysfunction versus the MRI assessment of disc displacement showed positive associations with an abnormality of the disc on the contralateral side (P < .OOl); clicking with disc displacement with reduction (P < .05), and jaw pain on the same side (P < .05). There was no statistically significant association between disc displacement and ear pain, headache, locking of the jaw, muscle tenderness, neck pain, temporal or frontal headaches, or joint crepitus. Bruxism was not significant when included in the side-

specific analysis; it was significant, however, when outcome was assessed as “no abnormality” versus “abnormality” (one or both sides) and volunteers and patients were combined (P = 0.001; odds ratio = 1.69; 95% CI = 1.50, 1.88). No significant relationship was noted between disc displacement and trauma or clenching. Discussion Kaplan et al’ have described no internal derangements in 62 joints of 31 asymptomatic volunteers, when arthrography was used, and Kircos et al2 described 32% positive joints in 21 symptomatic volun-

KATZBERG

ET

151

AL

FIGURE 2. A, MRI of the right TMJ in the sagittal plane and with the jaw closed shows an anterior disc (arrows). B, Open jaw position shows the disc (arrows) to have reduced into a normal relationship between the condyle (c) and temporal bone (t). This patient had no signs or symptoms of internal derangement related to disc displacement.

teers when MRI was used. However, in the latter study, no mention was made of rotational and sideways disc displacement. Tasaki et al5 examined 114 joints in 57 asymptomatic subjects by MRI and reported a 21% prevalence of internal derangement. Attention was paid to rotational and sideways disc displacements.The purposeof this latter investigation was to develop a classification system for disc displacement in the TMJ and to study the prevalence of the various types of TMJ disc displacement in patients and asymptomatic volunteers. The authors concluded that disc displacement can be asymptomatic and that anterior and anterolateral displacementswere the most common. The current investigation showed a distribution of anatomic types of

disc displacement, suggesting a higher frequency of anterior disc displacement and relatively equal frequencies between the rotational and sideways locations, declining laterally or medially. In addition, no difference was found between the distribution of disc displacement between asymptomatic volunteers and patients. The similar proportion of medial and lateral disc displacement challenges our hypotheses regarding causes of disc displacement. The attachment of the superior belly of the lateral pterygoid muscle onto the medial aspect of the joint capsule and the belief that muscle spasmof the superior belly of the lateral pterygoid muscle is a cause of disc displacement, has led to the speculation that most disc displacements are in the medial direction. This investigation showed a statistical association between internal derangement and bruxism. Previous studies have suggestedthat bruxism may be associated with progression from disc displacement with reduction to disc displacement without reduction.24x25 Whether internal derangementleads to bruxing or vice versa cannot be established from this investigation. One speculation would be that the force of bruxing could be transmitted to the apex of the condyle, resulting in extrusion of the disk into a variety of locations that follow the anatomic paths of least resistance. Because the capsule and lateral and medial ligaments support the sides of the joint structures, lateral and medial disc extrusion shouldbe lesslikely than anterior disc extrusion, as observed in this investigation. Posterior extrusion would be extremely unlikely, given the slightly anterior, normal location of the disc relative to the condyle. Our study confirms prior suggestionsthat disc displacement in one TMJ is related to disc displacement on the contralateral side, clicking, and jaw pain, which was side specific. The relatively high association of abnormality on the contralateral side is probably related to the important, but often unappreciated, aspect of the TMJ articulation, the unified action of both TMJs linked by the bony yoke of the jaw. Although our study Table 2. Comparison Patient Study Groups

of Volunteer

Versus

Internal Derangements Symptomatic Female

subjects*

Yes

No Male

subjects+

* Odds ratio t Odds ratio

= 5.75. = 4.36.

YCb

NO

72 16

18 23 5 28

Yes

I

No

9

152

ANATOMIC

FIGURE 3. A, This is an asymptomatic volunteer showing a low signal intensity the disc. B, However, the coronal image shows a sideways lateral disc displacement click could be detected.

shows a high prevalence of internal derangement in asymptomatic subjects, there is a very strong statistical difference between asymptomatic volunteers and symptomatic subjects with regard to the prevalence of disc displacement in these two study groups. In addition, the highest odds ratio associated with disc displacement without reduction versus disk displacement with reduction supports the notion that our concepts of progressive stages of the disorder are generally well founded. MRI studies of asymptomatic subjects evaluated for knee, cervical spine, and lumbar spine disorders indicate similar disease prevalences in asymptomatic subjects in these body parts as well.‘“‘“’ This emphasizes the necessity for comparison of clinical signs and symptoms with imaging findings, because imaging findings alone are not diagnostic of disease. Many reports have emphasized the high ratio of females to males in patients presenting with TMJ pain and dysfunction. Our patient material confirms this high ratio, but demonstrates only a slight preponderance of females versus males for disc displacement in a nonpatient population. This is in line with the results of previous epidemiologic studies, which suggest that there are no obvious differences in the sex distribution of symptoms related to TMJ or that the differences are not as large as might be expected based on experiences in patient populations.‘5~‘7~20~2’ We also encountered a rather large number of young patients, also predominantly females, in our patient material. Twenty-one of the 102 patients (21%) were of 10 to 19 years old, with a female to male ratio of 4.25. Previous studies have

structure (arrows)

DISORDERS

OF

THE

TMD

(arrows) in the TMJ fossa, possibly representing that reduced on opening. No audible or palpable

suggested that disc displacement of the TMJ is not necessarily uncommon in the younger age population.” We could find no statistical association between trauma and internal derangement. This is surprising, and casts doubts on previous studies giving anecdotal relationships. So many subjects have sustained injuries to the jaw at one time or another, which may lead to spurious associations. Because none of the suspected symptoms were rare, our sample sizes were sufficiently large to detect associations with the presence or absence of disc displacement. We analyzed symptoms in side-specific models. Potentially the results could be confounded by findings in the contralateral joint. Although we attempted to adjust for abnormalities in the contralateral side, we assume some symptoms to be side specific and unrelated to the contralateral side. However, the validity of this assumption cannot be adequately tested in this clinical model. In summary, there is a high prevalence of disc displacement in asymptomatic volunteers, but there is also a clear association between disc displacement and TMJ pain and dysfunction. This supports our notion that the severity of disc displacement without reduction is greater than disc displacement with reduction. Bruxing is statistically linked to TMJ disc displacement and could explain the anatomic distribution of abnormal disc positions. References 1. Kaplan PA, Tu HK, Sleder PR, et al: Inferior joint space arthrography of normal temporomandibular joints: Reassessment of diagnostic criteria. Radiology 1.59585, 1986

GEERT

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BOERING

2. Kircos LT, Ortendahl DA, Mark AS, et al: Magnetic resonance imaging of the TMJ disc in asymptomatic volunteers. J Oral Maxillofac Surg 45:852, 1987 3. Westesson P-L, Eriksson L, Kurita K: Reliability of a negative clinical temporomandibular joint examination: Prevalence of disk displacement in asymptomatic temporomandibular joints. Oral Surg Oral Med Oral Path01 68:551, 1989 4. Drace JE, Enzmann DR: Defining the normal temporomandibular joint: Closed-partially open-, and open-mouth MR imaging of asymptomatic subjects. Radiology 177:67, 1990 5. Tasaki MM, Westesson P-L, Isberg AM, et al: Classification and prevalence of temporomandibularjoint disc displacement in patients and asymptomatic volunteers. Am J Orthod Dentofacial Orthop (in press) 6. Katzberg RW: Temporomandibular joint imaging. Radiology 170:297, 1989 7. Katzberg RW, Bessette RW, Tallents RH, et al: Normal and abnormal temporomandibular joint: MR imaging with surface coil. Radiology 158: 183, 1986 8. Farrar WB, McCarty WL Jr: Inferior joint space arthrography and characteristics of condylar paths in internal derangements of the TMJ. J Prosthet Dent 41:548, 1979 9. Wilkes CH: Structural and functional alterations of the temporomandibular joint. Northwest Dentistry 57:287, 1978 10. Katzberg RW, Dolwick MF, Bales DJ, et al: Arthrotomography of the temporomandibular joint: New technique and preliminary observations. AJR Am J Roentgen01 132949, 1979 Il. Katzberg RW, Dolwick MF, Helms CA, et al: Arthrotomography of the temporomandibular joint. AJR Am J Roentgen01 134:995, 1980 12. Westesson PL: Double contrast athrotomography of the temporomandibular joint: Introduction of an arthrographic technique for visualization of the disk and articular surfaces. J Oral Maxillofac Surg 41:163, 1983 13. Katzbeg RW, Westesson PL, Tallents RH, et al: Temporomandibular joint: MR assessment of rotational and sideways disk displacements. Radiology 169:741, 1988 14. Helkimo M: Studies on function and dysfunction of the masticatory system. I. An epidemilogical investigation of symptoms of dysfunction in Lapps in the north of Finland. Proc Finn Dent Sot 70:37, 1974 15. Helkimo M: Studies on function and dysfunction of the masticatory system. IV. Age and sex distribution of symptoms of dysfunction of the masticatory system in Lapps in the north of Finland. Acta Odontol Stand 32:255, 1974 16. Agerberg G: Maximal mandibular movements in young men and women. Svensk Tandlakaretidskrift 67:81, 1974 17. Hansson T, Nilner M: A study of the occurence of symptoms

18. 19.

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21. 22.

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27.

28.

29.

30.

3 1.

32.

of diseases of the temporomandibular joint masticatory musculature and related structures. J Oral Rehabil 2:3 13, 1975 Angle EH: Classification of malocclusion. Dental Cosmos 41248, 1899 Armitage P, Berry G: Statistical Methods in Medical Research (ed 2). Cambridge, MA, Blackwell Scientific Publications, 1987 Agerberg G, Carlsson GE: Symptoms of functional disturbances of the masticatory system: A comparison of frequencies in a population sample and in a group of patients. Acta Odontol Stand 33: 183, 1975 Solberg WK, Woo MW, Houston JB: Prevalence of mandibular dysfunction in young adults. J Am Dent Assoc 9825, 1979 Egennark-Eriksson I, Carlsson GE, Ingervall B: Prevalence of mandibular dysfunction and orofacial parafunction in 7-, 1 land 15year-old Swedish children. Eur J Orthod 3:163, 1981 Locker D, Grushka M: Prevalence of oral and facial pain and discomfort: Preliminary results of a mail survey. Community Dent Oral EuidemioI I5:169. I987 Dolwick MF, Riggs RR: Diagnosis and treatment of internal derangements of the temporomandibular joint. Dent Clin North Am 27:561, 1983 Lund H, Westesson P-L, Kopp S: Three year followup of patients with reciproca1 temporomandibuiar joint clicking. OraISurg Oral Med Oral Path01 63:530, 1987 Nagendak WG, Femandez FR, Halbrun LK. et al: Magnetic resonance imaging of meniscal degeneration in asymptomatic knees. J Orthop Res 8:3 11, 1990 Komick J, Trefelner NE, McCarty S, et al: Meniscle abnormalities in the asymptomatic population in MR imaging. Radiology 177:463, 1990 Boden SD, Davis DO, Dina TS, et al: A prospective and blinded investigation of magnetic resonance imaging of the knee: Abnormal findings in asymptomatic subjects. Clin Orthop 282~177, 1992 Shellock FG, Morris E, Deutsch AL, et al: Hematopoietic bone marrow hyperplasia: High prevalence on MR images of the knee in asymptomatic marathon runners. AJR Am J Roentgenol 158:335, 1992 Boden SD, McCowin PR, Davis DO, et al: Abnormal magnetic resonance scans of the cervical spine in asymptomatic subjects. J Bone Joint Surg Am 72:1178, 1990 Boden SD, Davis DO, Dina TS, et al: Abnormal magnetic resonance scans of the lumbar spine in asymptomatic subjects: A prospective investigation. J Bone Joint Surg Am 72:403, 1990 Katzberg RW, Tallents RH, Hayakawa K, et al: Internal derangements of the temporomandibular joint: Findings in the pediatric age group. Radiology 154: 125, 1985

J Oral Maxiilofac Surg 54:153-155, 1996

Discussion Anatomic Disorders of the Temporomandibular Joint Disc in Asymptomatic Subjects Geert Boer&,

DMD, PhD

University

Groningen,

Hospital

The Netherlands

This article deals with an important issue in temporomandibular joint (TMJ) pathology: the prevalence of disc displacement in asymptomatic persons demonstrated by magnetic resonance imaging (MRI). The findings are compared

with the prevalence in a group of symptomatic patients. The underlying questions seem to be: 1) What is the clinical relevance of the coincidental finding of a displaced disc in the TMJ on the MRI and; 2) How strong is the relationship between clinical signs and symptoms of TMJ dysfunction and the positive MRI findings? Unfortunately, these questions are not clearly answered in this article. MRI studies of asymptomatic TMJs have been published before.‘.’ The findings in this investigation of a disc displacement on MRI in 33% of asymptomatic volunteers seems to be in harmony with the prevalence previously described in the literature. In my opinion, however, this percentage is