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The shape of the condyle and position of the meniscus in temporomandibular joint dysfunction
C 1994 The British .4ssociauon ofOrdl md Manillofacial
Surgmns
I
-
I
The shape of the condyle and position of the meniscus in temporomandibular joint dysfunction R. P. Juniper Depurtment
of‘Oru1 und Maxillofuciul
Surgq-,
John Rudcl&
Hospitul,
Headington,
Oxford OX3 YDC’
The position of the meniscus seems to be significant in the natural history of temporomandibular SUMMARY. joint dysfunction. It can be identified on MRI and arthrography but generally its displacement is referred to only in the sag&al plane. Littlc consideration is given to the shape and size of the condyle which could have great influence upon the position which the meniscus takes up. This paper reports the findings in 105 TM joints which have had arthrotomy for meniscoplasty (meniscopexy) and menisectomy over an &year period. Only 30% of the condyles had a normal size and shape; 24O/;,were excavated on the medial side, 15%~had lost the anterior surface of the condyle and were oblique in shape, 15% were small and round, while 12.5%) were flattened, two having no discernable condyle at all. The meniscus was found to be displaced anteromedially most commonly, with the anterior position, to which reference is so frequently made, being rare; the medial position was more common. The significance of these findings is discussed with particular reference to imaging.
INTRODUCTION Until recently, it has been generally accepted that the position of the meniscus in the temporomandibular joint (TMJ) is significant in the natural history and persistence of TMJ dysfunction. Numerous techniques have been described to determine the position of the meniscus by plain radiography,’ arthrography,2 computed tomography’ and magnetic resonance imaging (MRT).4 It would seem that MRI is becoming the investigation of choice for ascertaining the position of the meniscus’ and videoarthrography for joint dynamics.’ However, with experience, it is thought that the position of the meniscus can be ascertained by clinical findings alone without the need for intrusive and sophisticated techniques.’ Generally its position is referred to only in the sagittal plane. Where the meniscus has been identified in the incorrect position, the operation of meniscoplasty (meniscopexy) has become established as a most successful curative procedure for the condition. The operation has been well described in the early 1970s by McCarty & Farrar8 using an arthrotomy approach, and many surgeons have followed their example with commendable results.” Recently, arthroscopic surgery has been developed to achieve similar effects in some cases.” Whatever the hypothesis as to the cause of the malady, little consideration has been given to the condition of the bony parts of the joint, except in general terms where arthrosis, bony spurs or subarticular cysts have been identified on radiographs. Solberg et al. ‘I have pointed out that there can bc deviations in form of the condyle in TMJ dysfunction, and a recent paper by Muir & Goss” has pointed out that there is frequent evidence that, while there
are changes seen radiographically in symptomatic joints, there can be changes seen in the symptom-free in addition. Kerstens et ~1.‘~ have suggested that the angulation of the eminence may be a primary cause of the condition, predisposing a group of patients to dysfunction. Others have disputed this.14 Which is true? Is it the shape of the joint surface which causes a meniscus to sublux, or is it that a subluxed meniscus changes the contour of the joint surfaces? However such changes do occur, should we not take them into consideration when investigating the joint and devising treatment plans? This paper investigates the condition and shape of the condylar surface in patients who have undergone the open operation of mcniscoplasty and menisectomy over the past 8 years, and attempts to relate them to the position of the meniscus observed at surgery.
METHOD The distance between the insertion of the lateral pterygoid and the crest of the transverse ridge of the condyle is approximately 7 mm. This has been established by examining and measuring 20 dry condyles and 10 autopsy specimens. For the purpose of this paper, the normal height of the condyle was taken to bc 7 mm. Where the lateral pterygoid insertion was found to be included in the articular surface, then it was estimated that there had been a further 1 mm of loss, 8 mm. The records of 105 TMJs which had undergone arthrotomy for the surgical treatment of TMJ dysfunction, and whose surgical findings had been adequately recorded, were analysed. At oper-
72
British Journal
of Oral and Maxillofacial
Surgery
ation, as the upper joint space was opened, the convergence of the posterior and anterior bands was identified and an assessment made of its position in relation to the apex of the lateral pole of the condylc (Fig. 1). At a later stage, when the lower joint space was opened and the joint distracted widely using a custom-made distractor, i5 the shape of the condyle and the condition of its surface was assessed carefully and recorded. The presence and position of adhesions were noted. While it would have been of interest to have recorded the condition and contour of the glenoid fossa and eminence, to do so at surgery was found to be impossible. When the meniscus had been freed of any adhesions, the insertion of the lateral pterygoid was sought; this was readily seen through the anterior recess of the upper joint space. Attempts were made to make accurate measurements within the joint but had to be abandoned due to difficulties of access, particularly to the antcromedial part of the joint. An assessment was made of the distance between that insertion and the transverse ridge of the condyle. In essence, this was an estimate of the remaining vertical height of the condyle. This too was recorded. The surgical findings were then related back to factors in the history which might have influenced their development. This will be the subject of a further paper.
RESULTS 105 joints in 84 patients were examined in this way. Recordings of the size and shape of the condylc and the condition of its surface had all been taken with accuracy and noted down. The recordings of the position of the meniscus were ambiguous or inadequate in 8 joints and these had to be excluded from the examination. The findings are represented graphically in Figure 2, classified according to the shape of the condyle. It will be noted that only 32 (30.5%) of the 105 condyles were assessed as normal in shape. 25 condyles (24%) had a normal contour laterally, but were excavated medially, taking up a concave configuration in the sagittal plane and, to a lesser extent, in the coronal. It seemed that the concavity in most cases, accommodated a displaced meniscus. 16 cases ( 15%) had taken up an oblique configuration, where the anterior part of the condyle had, in effect: become a flat oblique facet. The remaining 2 shapes, small and round ( 16 cases, 15%) and flat ( 13 and 12.5%/o), had marked changes. Not only was the volume of the condyle reduced but 2 cases in the ‘flat’ group had no apparent condylc at all, with the insertion of the lateral pterygoid muscle being included into the articulating surface. The estimated loss of condylar height for each of the shapes described above is shown in the Table.
Distractor
Fig. I - (A) Photograph and (B) line drawing to show the upper .joint space opened and the position of the convergence of the anterior and posterior bands of the meniscus (*). The metal stilctte is pointing to the convergence. The lateral pole is being demonstrated by the points of Adson’s forceps.
The shape of the condylc
and position
of the meniscus
in temporomandibular
joint dysfunction
73
(1 excluded)
3 (3-8)
(3-6) ‘O
(3: 4) 8 (3-4) F 8 (2-6)
Excavated 24% (25)
\ 13 (3-6)
Oblique 15% (16) 3
4 (4-6)
(l-5)
,c
-
‘\ \
..: : :. .:
6 (3-7)
::
/ :
\ .\ .I /
i-7
Flat 12.5% (13)
::
Mist 3% (3)
a Fig. 2 - The shape of the condylc
/--
b
(2 excluded) KM WV
2
not subluxed
C
and position of the meniscus. For simplicity, a right condyle is depicted (a) from the front. (b) from the lateral side. The number of cases in each classification for the shape of the condyle is seen in the column on the left. (c) depicts the approximate displacement of the meniscus from the lateral pole, with the number of cases displaced in each direction shown. The numbers in brackets give the range of displacement in mm. Where the record for the meniscus position was unclear, the case was excluded. The figure is further explained in the text.
74
British Journal
Table- Estimate condyle
of Oral and Maxillofac;al
of loss of condylar
height
Surgery for each
shape
Shape of condyle
Loss of height (mm)
Normal Medially excavated Oblique Small Round Flattened
0 2.8 (range 0 5) 3.25 (range O-6) 4.65 (range 3 6) 5.6 (range 3-8)
Loss of condylar described.
height
for
each
of the
shapes
of
of condyles
Where the insertion of the lateral pterygoid was seen to be inserted into the articular surface, the loss of height was assumed to be more than the total height of the normal condyle. The position of the meniscus in relation to the condyle for each of the shapes described is also depicted in Figure 2. This was assessed by estimating the position of the convergence of the posterior and anterior bands of the meniscus in relation to the lateral pole of the condyle both in the coronal and sagittal planes. These figures wcrc transposed into angles for simplicity of presentation in Figure 2. The number of cases is shown for each direction of displacement. The distance displaced from the lateral pole, expressed in millimetres, is seen in brackets. It will be recognised immediately that true anterior displacement was rare with true medial being slightly more common. Anteromedial was the commonest direction of all. Figure 3 shows the displacement of the meniscus from the lateral pole in all cases adequately recorded. All the above reported cases had macroscopically smooth condylar surfaces with fibrocartilage cover. Three cases had severe destruction of the joint elements with rough and bleeding condylar surfaces and were discounted from the record.
31(3-6) Fig. 3 - A diagrammatic reprcscntation of the displacement of the meniscus in all the cases, with the numbers in each direction shown (see text).
DISCUSSION
This investigation would have been improved if it had been possible to measure the position of the meniscus and morphology of the condyle with a rule. The distractor used achieves up to 10 mm of access which, for the purpose of mobilising the meniscus and manipulating and suturing it to the correct position, is very satisfactory. To do more than estimate and assess the findings was impossible. Photography was also unsatisfactory for recording purposes, using traditional lenses and illumination. The observations were thoughtfully carried out and represent the most accurate evaluation as it was possible to obtain. It was interesting to find the varied shapes that the condyle achieved. While approximately 30% of the joints had a condyle of normal shape and size, the rest did not. All but 3 of the condyles had macroscopically smooth articulating surfaces, whatever the general contour of the condyle. Amongst the abnormal shapes, the medially cavitated predominated, and all of these had medial or anteromedial subluxation of the meniscus, medial subluxation ranging between 4 and 8 mm. In these cases in particular, it seemed that the condyle had remodelled to accommodate the changed position of the meniscus. There were 16 cases each of the oblique and small round groups. The oblique group had a flat facet which had developed with a regular resorption right across the anterior slope of the condylc. Here there was a tendency for the meniscus to be more anteriorly placed: but there were 3 joints where the meniscus was almost entirely medial. The 16 joints which had degenerated to have small round condyles are particularly interesting, for one has to speculate as to whether these had developed small or had resorbed in uniform fashion. In all cases it was noted that the menisci appeared to be of normal size. Four of these menisci appeared to be in the usual position in the fossa when the joint was originally opened. These are classified as ‘not subluxcd’ in the figure. There were no adhesions in these and, in reality, the meniscus could take up many different positions over the reduced condyle. This may help to explain reports, mainly from literature dealing with imaging, that the meniscus is observed sometimes to be lying lateral” or even posterior to the condyle. Perhaps the most surprising cases were the 13 which had totally flattened condyles with vertical loss estimated between 5 and 7 mm, with 2 of them resorbed right down to the insertion of the lateral pterygoid muscle. yet all of these had a smooth articular surface with apparently normal fibrocartilage on the surface. It would seem from this that the condyle had resorbed in response to chronic trauma or stress, but had maintained a reasonably good articulating surface. Three joints were badly inflamed, very haemorrhagic and with rough and bleeding surfaces. One of these had had a high condylcctomy previously. All of them had perforations of the meniscus itself.
The shaue of the condvle and oosition of the meniscus in temooromandibular
Investigations
to illustrate the position of the meniscus
Little attention is paid to the morphology of the joint surfaces when imaging techniques are applied to assess the position of the meniscus. Indeed, all radiographic techniques have their failings when considering the overall shape of the condyle. Imaging techniques could manage to show changes in the shape of the condylar surface, but only with multiple tomographic slices; it would be difficult to assess changes in height of the condyle except only in the crudest terms. In this respect it is clear that plain film radiography has very little to offer except in extreme cases. The concept of ‘concentricity’ of the condyle in the fossa as a measure of the position of the meniscus has been questioned by others” for rather different reasons, but with the evidence from this investigation, it should be abandoned. Those with an oblique conliguration could only give confusing results, and the 29 cases where the condylar volume was markedly reduced, would be meaningless when assessing ‘concentricity’. Tomography and computed tomography could demonstrate the shape of the condyle, but to illustrate the loss of height, together with the loss of bone substance across the joint is difficult: mainly as it is impossible to see the necessary landmarks from which calculations may be made. In the present series, the 16 small round condyles and the 13 flat ones would be certain to have a subluxation of the meniscus of some kind, since the meniscus would be ‘too big’ for the condyle, which appeared to have resorbed within its confines, presumably as a result of chronic trauma and overload. Thus the degree of subluxation of the meniscus in these cases is not particularly relevant since a small condyle allows the meniscus to take up any position relative to it-medial, lateral or even posterior. MRI, using high quality surface coils, is likely to be the best medium to image all the elements of the joint. While bone outline is less clear than when using radiographic techniques, the soft tissue elements are readily visualised, with the anterior and posterior bands of the meniscus readily seen. Above all MRT is the only medium able to depict the insertion of the lateral pterygoid muscle and it is from this that the extent of resorption of the condylar head can be ascertained, and the significance of meniscus subluxation understood. Nitzan et ~1.’ have recently reported that clinical findings alone can depict whether the meniscus is displaced and have questioned the value of arthrography and other investigations which set out to determine the position of the meniscus. While this may be true, there does still seem to be a place for arthrography, as it is the assessment of the dynamics of the joint which is valuable. However, the morphology of the joint has to bc considered before meaning can be given to the behaviour of the visualised components. Simply to assert that the meniscus is anterior is of no value, particularly as this study has shown that pure anterior subluxation is rare, with the pure medial subluxation actually being more common. The ante-
romedial as such.
position
is very common,
ioint dvsfunction
75
but rarely reported
Occlusal hypothesis for TMJ dysfunction There is a school of thought which has suggested that abnormalities in the occlusion of the teeth are the cause of TMJ dysfunction.” It is difficult to believe that discrepancies in the occlusion alone could be responsible for the dramatic changes in the condyle prcscntcd in this paper. With 70% of the joints having vertical loss in the condyle ranging between I and 8 mm, it is difficult to believe that abnormalities in the occlusion corrected by equilibration representing microns of change, really could make a significant difference. Indeed, for the loss of vertical height at the condylc to be accommodated at the occlusion without the development of an anterior open bite, one has to assume that the posterior teeth are intruded, or the anterior teeth extruded. Thus the more likely explanation of the malocclusions described would be the change in the height of the ramus: in other words, the dysfunction causes the malocclusion rather than malocclusion causes the dysfunction. This is supported by the knowledge that malocclusions may be present without a concomitant TMJ dysfunction.” The high condylectomy This was first described by Henny” and has been used by many since. More recently, the high condylectomy has been used in conjunction with meniscoplasty so as to increase joint space.20 The high condylectomy has little rationale, even when it was first performed but, with recent evidence of the particular healing capacity exhibited by the condylar cartilage,2’ it would have even less logic now. All but 3 cases had macroscopically intact cartilage whatever the shape and resorption, and it would seem quite wrong to interfere with it surgically. In addition, 67 of the 105 cases had inherent resorption already with total loss of condylar height in 4 cases. Why reduce this cvcn further? In some it would be impossible. to section Hopkins 22 has develop- cd a tcchniquc the condyle in the neck so as not to interfere with the joint surfaces, again on the grounds that more joint space is needed. It would seem from the present study that ‘nature’ can do this very satisfactorily without surgical interference. Adaptation to stress There are many hypotheses as to the cause of TMJ dysfunction but no proof has been established for any. There is evidence that the TMJ, as compared with other joints in the human body, has great powers of healing21 and it is common experience that, after trauma, the condyle remodels. This has been shown experimcntally.2” The findings in this study would seem to confirm these suggestions. Of the 105 joints studied, all had been giving sufficient pain to interfere with the enjoyment of life, and only 30% could be
76
British Journal
of Oral and Maxillofacial
Sureerv
considered of normal shape. Of the 70% making up the remainder, only 3 had evidence of acute or subacute inflammatory change. Thcrc had been resorption of the condylar head, which appeared to have changed shape to accommodate the changed position of the meniscus, but without evidence of loss of fibrocartilage on the condylar surface.
6.
7.
8.
COKCLUSION It would seem that the TMJ has great powers of adaptability but the factors which influence this are unknown. The present findings show that there is loss of condylar substance and subluxation of the meniscus in patients suffering severe facial arthomyalgia, but there has to be speculation as to why this occurs. The most likely judgment is that it is a response to chronic stress and overload. When structural change dots occur, the meniscus displaces most commonly in the anteromedial direction, and 70% of joints with such a displacement have significant changes in size and shape of the condyle. These changes are very difficult to assess by present techniques of imaging but it is abundantly clear that plain radiographs are likely to give very little helpful information except where thcrc arc gross changes. Tomography and CT may be able to illustrate the bony change and certain soft tissue changes24 but multiple narrow slices would be necessary. MRI can achicvc the best imaging of the static joint structures and is the only medium to assess the condylar height and the position of the meniscus; it cannot assess the dynamics of the joint. Videoarthrography is the most helpful in this respect, but again the radiologist would need to be aware of the potential changes in morphology which can occur if the diagnosis is to be accurate. The changes seen in 70% of cases where there is notable to profound change in the shape and size of the condyle, suggest that the hypothcscs of the cause of TMJ dysfunction based only upon changes witnessed in the occlusion, are no longer tenable.
9.
IO.
Il.
12.
13.
14.
15.
16.
17.
18.
19. 20.
21.
22. 23.
References 1. Mahan P, Gibbs C, Brannon L. Superior and inferior bellies of the lateral pterygoid muscle EMG activity at basic jaw positions. J Prosthet Dent 1983; 50: 710-717. 2. Lott C, Wilson D, Juniper R. Tcmporomandibular joint arthrography: dynamic study by videorecording. Clin Radio1 1988; 39: 73-16. 3. Christiansen EL, Thompson JR. Computed tomography. In: Westesson PL, Katzberg RW, cd. Imaging of the temporomandibular joint. 1st cd. Baltimore: Williams and Wilkins, I99 I : 17-34. 4. Katzberg RW, Westesson Per-Lennart. Selection of imaging modalities for patients presenting with symptoms of internal derangement. In: Westesson PL, Katzberg RW, ed. Imaging of the temporomandibularjoint. 1st ed. 1. Baltimore: Williams and Wilkins, 1991: 127. 132. 5. Nakasato T, Ehara S, Tamakawa Y, Kobayakawa T. MRI
24.
and arthrography in the evaluation of TMJ disorders. Nippon Igaku Hoshascn Gakkai Zasshi 1991; 51: 912 922. Wcstesson PL, Bronstcin Sidney L. Temporomandibular joint: comparison of single- and double-contrast anhrography. Radiology 1987; 164: 65 70. Nitzan D, Dolwick F, Marmary Y. The value of arthrography in the decision making process regarding surgery for internal derangement of the temporomandtbular joint. J Oral Maxillofac Surg 1991; 49: 375-379; discussion 379-380. McCarty W, Farrar W. Surgery for internal derangements of the temporomandibular joint. .l Prosthct Dent 1979; 42: 191-196. Dolwick M. Surgical management. in: Helms C, Katzberg RI Dolwick Ma eds. Internal derangements of the temporomandibular joint. San Fransisco: Radiology Rcscamh and Education Foundation, 1983: Ch. 8. Ohnishi M. Arthroscopy and arthroscopic surgery. In: Norman J: Brdmley P, eds. A textbook and colour atlas of the temporomandibular joint. 1st ed. London: Wolfe Medical Atlases, 1990: 110-127. Solberg W, Bibb C, Nordstrom B, Hansson T. Malocclusion associated with temporomandibular joint changes in young adults at autopsy. Am J of Orthod 1986; 89: 326 330. Muir B, Goss A. The radiologic morphology of asymptomatic tcmporomandibular joints. Oral Surg Oral Med Oral Pathol 1990; 70: 349.354. Kerstens H. Tuinzing D, Golding R, Van der Kwast W. Inclination of the temporomandibular joint eminence and anterior disc displacement. Int J Oral Maxillofac Surg 1989; 18: 229-232. Alsawaf MM,Garlapo D, Gale E, Carter M. The relationship between condylar guidance and temporomandibular joint clicking. J Prosthet Dent 1989; 61: 349-354. Juniper R. A new instrument-temporomandibular joint distraction forceps. Br J Oral Maxillofac Surg 1987; 25: 169 170. Westesson P. 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 Pathol 1989; 68: 551 554. Cholitgul W? Petersson A. Rohlin MM,Akerman S. Clinical and radiological findings in tcmporomandibular joints with disc ncrforation. Int J Oral Maxillofac Sure 1990; 19: 220-225. Droukas B, Lindee C, Carlsson G. Relationship between occlusal factors and signs and symptoms of mandibular dysfunction. A clinical study of 48 dental students. Acta Odontol Stand 1984; 42: 277-83. Hcnny F, Baldridge 0. Condylcctomy for the persistently painful temporomandibular joint. J Oral Surg 1957; 15: 24-3 1. Eppley BL, Delfmo JJ. Surgical treatment of internal derangements of the temporomandibular joint: evaluation of two techniques. J Oral Maxillofac Surg 1988; 46: 721-726. Robinson P. Articular cartilage of the temporomandibular joint+an it regcncratc? Huntcrian Lecture, Royal College of Surgeons of England 1992: Novcmbcr. Hopkins R. Personal communication. Luz J, Jaeger R, DeAraujo VC, DeRezende JR. The elfect of indirect trauma on the rat temporomandibular joint. Int J Oral Maxillofac Surg 1991; 20: 48 52. Wilkinson T; Marynuik G. The correlation between sagittal anatomic sections and computerised tomography of the TMJ. J Craniomandib Pratt 1983; I: 37-45.
The Author R. P. .Juniper Department of Oral and Maxillofacial John RadclilTe Hospital Headington . Oxford OX3 9DU Correspondence
and requests
Paper received 11 March 1993 Accepted 3 September 1993
Surgery
for ofTprints to R. P. Juniper
Surgmns
I
-
I
The shape of the condyle and position of the meniscus in temporomandibular joint dysfunction R. P. Juniper Depurtment
of‘Oru1 und Maxillofuciul
Surgq-,
John Rudcl&
Hospitul,
Headington,
Oxford OX3 YDC’
The position of the meniscus seems to be significant in the natural history of temporomandibular SUMMARY. joint dysfunction. It can be identified on MRI and arthrography but generally its displacement is referred to only in the sag&al plane. Littlc consideration is given to the shape and size of the condyle which could have great influence upon the position which the meniscus takes up. This paper reports the findings in 105 TM joints which have had arthrotomy for meniscoplasty (meniscopexy) and menisectomy over an &year period. Only 30% of the condyles had a normal size and shape; 24O/;,were excavated on the medial side, 15%~had lost the anterior surface of the condyle and were oblique in shape, 15% were small and round, while 12.5%) were flattened, two having no discernable condyle at all. The meniscus was found to be displaced anteromedially most commonly, with the anterior position, to which reference is so frequently made, being rare; the medial position was more common. The significance of these findings is discussed with particular reference to imaging.
INTRODUCTION Until recently, it has been generally accepted that the position of the meniscus in the temporomandibular joint (TMJ) is significant in the natural history and persistence of TMJ dysfunction. Numerous techniques have been described to determine the position of the meniscus by plain radiography,’ arthrography,2 computed tomography’ and magnetic resonance imaging (MRT).4 It would seem that MRI is becoming the investigation of choice for ascertaining the position of the meniscus’ and videoarthrography for joint dynamics.’ However, with experience, it is thought that the position of the meniscus can be ascertained by clinical findings alone without the need for intrusive and sophisticated techniques.’ Generally its position is referred to only in the sagittal plane. Where the meniscus has been identified in the incorrect position, the operation of meniscoplasty (meniscopexy) has become established as a most successful curative procedure for the condition. The operation has been well described in the early 1970s by McCarty & Farrar8 using an arthrotomy approach, and many surgeons have followed their example with commendable results.” Recently, arthroscopic surgery has been developed to achieve similar effects in some cases.” Whatever the hypothesis as to the cause of the malady, little consideration has been given to the condition of the bony parts of the joint, except in general terms where arthrosis, bony spurs or subarticular cysts have been identified on radiographs. Solberg et al. ‘I have pointed out that there can bc deviations in form of the condyle in TMJ dysfunction, and a recent paper by Muir & Goss” has pointed out that there is frequent evidence that, while there
are changes seen radiographically in symptomatic joints, there can be changes seen in the symptom-free in addition. Kerstens et ~1.‘~ have suggested that the angulation of the eminence may be a primary cause of the condition, predisposing a group of patients to dysfunction. Others have disputed this.14 Which is true? Is it the shape of the joint surface which causes a meniscus to sublux, or is it that a subluxed meniscus changes the contour of the joint surfaces? However such changes do occur, should we not take them into consideration when investigating the joint and devising treatment plans? This paper investigates the condition and shape of the condylar surface in patients who have undergone the open operation of mcniscoplasty and menisectomy over the past 8 years, and attempts to relate them to the position of the meniscus observed at surgery.
METHOD The distance between the insertion of the lateral pterygoid and the crest of the transverse ridge of the condyle is approximately 7 mm. This has been established by examining and measuring 20 dry condyles and 10 autopsy specimens. For the purpose of this paper, the normal height of the condyle was taken to bc 7 mm. Where the lateral pterygoid insertion was found to be included in the articular surface, then it was estimated that there had been a further 1 mm of loss, 8 mm. The records of 105 TMJs which had undergone arthrotomy for the surgical treatment of TMJ dysfunction, and whose surgical findings had been adequately recorded, were analysed. At oper-
72
British Journal
of Oral and Maxillofacial
Surgery
ation, as the upper joint space was opened, the convergence of the posterior and anterior bands was identified and an assessment made of its position in relation to the apex of the lateral pole of the condylc (Fig. 1). At a later stage, when the lower joint space was opened and the joint distracted widely using a custom-made distractor, i5 the shape of the condyle and the condition of its surface was assessed carefully and recorded. The presence and position of adhesions were noted. While it would have been of interest to have recorded the condition and contour of the glenoid fossa and eminence, to do so at surgery was found to be impossible. When the meniscus had been freed of any adhesions, the insertion of the lateral pterygoid was sought; this was readily seen through the anterior recess of the upper joint space. Attempts were made to make accurate measurements within the joint but had to be abandoned due to difficulties of access, particularly to the antcromedial part of the joint. An assessment was made of the distance between that insertion and the transverse ridge of the condyle. In essence, this was an estimate of the remaining vertical height of the condyle. This too was recorded. The surgical findings were then related back to factors in the history which might have influenced their development. This will be the subject of a further paper.
RESULTS 105 joints in 84 patients were examined in this way. Recordings of the size and shape of the condylc and the condition of its surface had all been taken with accuracy and noted down. The recordings of the position of the meniscus were ambiguous or inadequate in 8 joints and these had to be excluded from the examination. The findings are represented graphically in Figure 2, classified according to the shape of the condyle. It will be noted that only 32 (30.5%) of the 105 condyles were assessed as normal in shape. 25 condyles (24%) had a normal contour laterally, but were excavated medially, taking up a concave configuration in the sagittal plane and, to a lesser extent, in the coronal. It seemed that the concavity in most cases, accommodated a displaced meniscus. 16 cases ( 15%) had taken up an oblique configuration, where the anterior part of the condyle had, in effect: become a flat oblique facet. The remaining 2 shapes, small and round ( 16 cases, 15%) and flat ( 13 and 12.5%/o), had marked changes. Not only was the volume of the condyle reduced but 2 cases in the ‘flat’ group had no apparent condylc at all, with the insertion of the lateral pterygoid muscle being included into the articulating surface. The estimated loss of condylar height for each of the shapes described above is shown in the Table.
Distractor
Fig. I - (A) Photograph and (B) line drawing to show the upper .joint space opened and the position of the convergence of the anterior and posterior bands of the meniscus (*). The metal stilctte is pointing to the convergence. The lateral pole is being demonstrated by the points of Adson’s forceps.
The shape of the condylc
and position
of the meniscus
in temporomandibular
joint dysfunction
73
(1 excluded)
3 (3-8)
(3-6) ‘O
(3: 4) 8 (3-4) F 8 (2-6)
Excavated 24% (25)
\ 13 (3-6)
Oblique 15% (16) 3
4 (4-6)
(l-5)
,c
-
‘\ \
..: : :. .:
6 (3-7)
::
/ :
\ .\ .I /
i-7
Flat 12.5% (13)
::
Mist 3% (3)
a Fig. 2 - The shape of the condylc
/--
b
(2 excluded) KM WV
2
not subluxed
C
and position of the meniscus. For simplicity, a right condyle is depicted (a) from the front. (b) from the lateral side. The number of cases in each classification for the shape of the condyle is seen in the column on the left. (c) depicts the approximate displacement of the meniscus from the lateral pole, with the number of cases displaced in each direction shown. The numbers in brackets give the range of displacement in mm. Where the record for the meniscus position was unclear, the case was excluded. The figure is further explained in the text.
74
British Journal
Table- Estimate condyle
of Oral and Maxillofac;al
of loss of condylar
height
Surgery for each
shape
Shape of condyle
Loss of height (mm)
Normal Medially excavated Oblique Small Round Flattened
0 2.8 (range 0 5) 3.25 (range O-6) 4.65 (range 3 6) 5.6 (range 3-8)
Loss of condylar described.
height
for
each
of the
shapes
of
of condyles
Where the insertion of the lateral pterygoid was seen to be inserted into the articular surface, the loss of height was assumed to be more than the total height of the normal condyle. The position of the meniscus in relation to the condyle for each of the shapes described is also depicted in Figure 2. This was assessed by estimating the position of the convergence of the posterior and anterior bands of the meniscus in relation to the lateral pole of the condyle both in the coronal and sagittal planes. These figures wcrc transposed into angles for simplicity of presentation in Figure 2. The number of cases is shown for each direction of displacement. The distance displaced from the lateral pole, expressed in millimetres, is seen in brackets. It will be recognised immediately that true anterior displacement was rare with true medial being slightly more common. Anteromedial was the commonest direction of all. Figure 3 shows the displacement of the meniscus from the lateral pole in all cases adequately recorded. All the above reported cases had macroscopically smooth condylar surfaces with fibrocartilage cover. Three cases had severe destruction of the joint elements with rough and bleeding condylar surfaces and were discounted from the record.
31(3-6) Fig. 3 - A diagrammatic reprcscntation of the displacement of the meniscus in all the cases, with the numbers in each direction shown (see text).
DISCUSSION
This investigation would have been improved if it had been possible to measure the position of the meniscus and morphology of the condyle with a rule. The distractor used achieves up to 10 mm of access which, for the purpose of mobilising the meniscus and manipulating and suturing it to the correct position, is very satisfactory. To do more than estimate and assess the findings was impossible. Photography was also unsatisfactory for recording purposes, using traditional lenses and illumination. The observations were thoughtfully carried out and represent the most accurate evaluation as it was possible to obtain. It was interesting to find the varied shapes that the condyle achieved. While approximately 30% of the joints had a condyle of normal shape and size, the rest did not. All but 3 of the condyles had macroscopically smooth articulating surfaces, whatever the general contour of the condyle. Amongst the abnormal shapes, the medially cavitated predominated, and all of these had medial or anteromedial subluxation of the meniscus, medial subluxation ranging between 4 and 8 mm. In these cases in particular, it seemed that the condyle had remodelled to accommodate the changed position of the meniscus. There were 16 cases each of the oblique and small round groups. The oblique group had a flat facet which had developed with a regular resorption right across the anterior slope of the condylc. Here there was a tendency for the meniscus to be more anteriorly placed: but there were 3 joints where the meniscus was almost entirely medial. The 16 joints which had degenerated to have small round condyles are particularly interesting, for one has to speculate as to whether these had developed small or had resorbed in uniform fashion. In all cases it was noted that the menisci appeared to be of normal size. Four of these menisci appeared to be in the usual position in the fossa when the joint was originally opened. These are classified as ‘not subluxcd’ in the figure. There were no adhesions in these and, in reality, the meniscus could take up many different positions over the reduced condyle. This may help to explain reports, mainly from literature dealing with imaging, that the meniscus is observed sometimes to be lying lateral” or even posterior to the condyle. Perhaps the most surprising cases were the 13 which had totally flattened condyles with vertical loss estimated between 5 and 7 mm, with 2 of them resorbed right down to the insertion of the lateral pterygoid muscle. yet all of these had a smooth articular surface with apparently normal fibrocartilage on the surface. It would seem from this that the condyle had resorbed in response to chronic trauma or stress, but had maintained a reasonably good articulating surface. Three joints were badly inflamed, very haemorrhagic and with rough and bleeding surfaces. One of these had had a high condylcctomy previously. All of them had perforations of the meniscus itself.
The shaue of the condvle and oosition of the meniscus in temooromandibular
Investigations
to illustrate the position of the meniscus
Little attention is paid to the morphology of the joint surfaces when imaging techniques are applied to assess the position of the meniscus. Indeed, all radiographic techniques have their failings when considering the overall shape of the condyle. Imaging techniques could manage to show changes in the shape of the condylar surface, but only with multiple tomographic slices; it would be difficult to assess changes in height of the condyle except only in the crudest terms. In this respect it is clear that plain film radiography has very little to offer except in extreme cases. The concept of ‘concentricity’ of the condyle in the fossa as a measure of the position of the meniscus has been questioned by others” for rather different reasons, but with the evidence from this investigation, it should be abandoned. Those with an oblique conliguration could only give confusing results, and the 29 cases where the condylar volume was markedly reduced, would be meaningless when assessing ‘concentricity’. Tomography and computed tomography could demonstrate the shape of the condyle, but to illustrate the loss of height, together with the loss of bone substance across the joint is difficult: mainly as it is impossible to see the necessary landmarks from which calculations may be made. In the present series, the 16 small round condyles and the 13 flat ones would be certain to have a subluxation of the meniscus of some kind, since the meniscus would be ‘too big’ for the condyle, which appeared to have resorbed within its confines, presumably as a result of chronic trauma and overload. Thus the degree of subluxation of the meniscus in these cases is not particularly relevant since a small condyle allows the meniscus to take up any position relative to it-medial, lateral or even posterior. MRI, using high quality surface coils, is likely to be the best medium to image all the elements of the joint. While bone outline is less clear than when using radiographic techniques, the soft tissue elements are readily visualised, with the anterior and posterior bands of the meniscus readily seen. Above all MRT is the only medium able to depict the insertion of the lateral pterygoid muscle and it is from this that the extent of resorption of the condylar head can be ascertained, and the significance of meniscus subluxation understood. Nitzan et ~1.’ have recently reported that clinical findings alone can depict whether the meniscus is displaced and have questioned the value of arthrography and other investigations which set out to determine the position of the meniscus. While this may be true, there does still seem to be a place for arthrography, as it is the assessment of the dynamics of the joint which is valuable. However, the morphology of the joint has to bc considered before meaning can be given to the behaviour of the visualised components. Simply to assert that the meniscus is anterior is of no value, particularly as this study has shown that pure anterior subluxation is rare, with the pure medial subluxation actually being more common. The ante-
romedial as such.
position
is very common,
ioint dvsfunction
75
but rarely reported
Occlusal hypothesis for TMJ dysfunction There is a school of thought which has suggested that abnormalities in the occlusion of the teeth are the cause of TMJ dysfunction.” It is difficult to believe that discrepancies in the occlusion alone could be responsible for the dramatic changes in the condyle prcscntcd in this paper. With 70% of the joints having vertical loss in the condyle ranging between I and 8 mm, it is difficult to believe that abnormalities in the occlusion corrected by equilibration representing microns of change, really could make a significant difference. Indeed, for the loss of vertical height at the condylc to be accommodated at the occlusion without the development of an anterior open bite, one has to assume that the posterior teeth are intruded, or the anterior teeth extruded. Thus the more likely explanation of the malocclusions described would be the change in the height of the ramus: in other words, the dysfunction causes the malocclusion rather than malocclusion causes the dysfunction. This is supported by the knowledge that malocclusions may be present without a concomitant TMJ dysfunction.” The high condylectomy This was first described by Henny” and has been used by many since. More recently, the high condylectomy has been used in conjunction with meniscoplasty so as to increase joint space.20 The high condylectomy has little rationale, even when it was first performed but, with recent evidence of the particular healing capacity exhibited by the condylar cartilage,2’ it would have even less logic now. All but 3 cases had macroscopically intact cartilage whatever the shape and resorption, and it would seem quite wrong to interfere with it surgically. In addition, 67 of the 105 cases had inherent resorption already with total loss of condylar height in 4 cases. Why reduce this cvcn further? In some it would be impossible. to section Hopkins 22 has develop- cd a tcchniquc the condyle in the neck so as not to interfere with the joint surfaces, again on the grounds that more joint space is needed. It would seem from the present study that ‘nature’ can do this very satisfactorily without surgical interference. Adaptation to stress There are many hypotheses as to the cause of TMJ dysfunction but no proof has been established for any. There is evidence that the TMJ, as compared with other joints in the human body, has great powers of healing21 and it is common experience that, after trauma, the condyle remodels. This has been shown experimcntally.2” The findings in this study would seem to confirm these suggestions. Of the 105 joints studied, all had been giving sufficient pain to interfere with the enjoyment of life, and only 30% could be
76
British Journal
of Oral and Maxillofacial
Sureerv
considered of normal shape. Of the 70% making up the remainder, only 3 had evidence of acute or subacute inflammatory change. Thcrc had been resorption of the condylar head, which appeared to have changed shape to accommodate the changed position of the meniscus, but without evidence of loss of fibrocartilage on the condylar surface.
6.
7.
8.
COKCLUSION It would seem that the TMJ has great powers of adaptability but the factors which influence this are unknown. The present findings show that there is loss of condylar substance and subluxation of the meniscus in patients suffering severe facial arthomyalgia, but there has to be speculation as to why this occurs. The most likely judgment is that it is a response to chronic stress and overload. When structural change dots occur, the meniscus displaces most commonly in the anteromedial direction, and 70% of joints with such a displacement have significant changes in size and shape of the condyle. These changes are very difficult to assess by present techniques of imaging but it is abundantly clear that plain radiographs are likely to give very little helpful information except where thcrc arc gross changes. Tomography and CT may be able to illustrate the bony change and certain soft tissue changes24 but multiple narrow slices would be necessary. MRI can achicvc the best imaging of the static joint structures and is the only medium to assess the condylar height and the position of the meniscus; it cannot assess the dynamics of the joint. Videoarthrography is the most helpful in this respect, but again the radiologist would need to be aware of the potential changes in morphology which can occur if the diagnosis is to be accurate. The changes seen in 70% of cases where there is notable to profound change in the shape and size of the condyle, suggest that the hypothcscs of the cause of TMJ dysfunction based only upon changes witnessed in the occlusion, are no longer tenable.
9.
IO.
Il.
12.
13.
14.
15.
16.
17.
18.
19. 20.
21.
22. 23.
References 1. Mahan P, Gibbs C, Brannon L. Superior and inferior bellies of the lateral pterygoid muscle EMG activity at basic jaw positions. J Prosthet Dent 1983; 50: 710-717. 2. Lott C, Wilson D, Juniper R. Tcmporomandibular joint arthrography: dynamic study by videorecording. Clin Radio1 1988; 39: 73-16. 3. Christiansen EL, Thompson JR. Computed tomography. In: Westesson PL, Katzberg RW, cd. Imaging of the temporomandibular joint. 1st cd. Baltimore: Williams and Wilkins, I99 I : 17-34. 4. Katzberg RW, Westesson Per-Lennart. Selection of imaging modalities for patients presenting with symptoms of internal derangement. In: Westesson PL, Katzberg RW, ed. Imaging of the temporomandibularjoint. 1st ed. 1. Baltimore: Williams and Wilkins, 1991: 127. 132. 5. Nakasato T, Ehara S, Tamakawa Y, Kobayakawa T. MRI
24.
and arthrography in the evaluation of TMJ disorders. Nippon Igaku Hoshascn Gakkai Zasshi 1991; 51: 912 922. Wcstesson PL, Bronstcin Sidney L. Temporomandibular joint: comparison of single- and double-contrast anhrography. Radiology 1987; 164: 65 70. Nitzan D, Dolwick F, Marmary Y. The value of arthrography in the decision making process regarding surgery for internal derangement of the temporomandtbular joint. J Oral Maxillofac Surg 1991; 49: 375-379; discussion 379-380. McCarty W, Farrar W. Surgery for internal derangements of the temporomandibular joint. .l Prosthct Dent 1979; 42: 191-196. Dolwick M. Surgical management. in: Helms C, Katzberg RI Dolwick Ma eds. Internal derangements of the temporomandibular joint. San Fransisco: Radiology Rcscamh and Education Foundation, 1983: Ch. 8. Ohnishi M. Arthroscopy and arthroscopic surgery. In: Norman J: Brdmley P, eds. A textbook and colour atlas of the temporomandibular joint. 1st ed. London: Wolfe Medical Atlases, 1990: 110-127. Solberg W, Bibb C, Nordstrom B, Hansson T. Malocclusion associated with temporomandibular joint changes in young adults at autopsy. Am J of Orthod 1986; 89: 326 330. Muir B, Goss A. The radiologic morphology of asymptomatic tcmporomandibular joints. Oral Surg Oral Med Oral Pathol 1990; 70: 349.354. Kerstens H. Tuinzing D, Golding R, Van der Kwast W. Inclination of the temporomandibular joint eminence and anterior disc displacement. Int J Oral Maxillofac Surg 1989; 18: 229-232. Alsawaf MM,Garlapo D, Gale E, Carter M. The relationship between condylar guidance and temporomandibular joint clicking. J Prosthet Dent 1989; 61: 349-354. Juniper R. A new instrument-temporomandibular joint distraction forceps. Br J Oral Maxillofac Surg 1987; 25: 169 170. Westesson P. 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 Pathol 1989; 68: 551 554. Cholitgul W? Petersson A. Rohlin MM,Akerman S. Clinical and radiological findings in tcmporomandibular joints with disc ncrforation. Int J Oral Maxillofac Sure 1990; 19: 220-225. Droukas B, Lindee C, Carlsson G. Relationship between occlusal factors and signs and symptoms of mandibular dysfunction. A clinical study of 48 dental students. Acta Odontol Stand 1984; 42: 277-83. Hcnny F, Baldridge 0. Condylcctomy for the persistently painful temporomandibular joint. J Oral Surg 1957; 15: 24-3 1. Eppley BL, Delfmo JJ. Surgical treatment of internal derangements of the temporomandibular joint: evaluation of two techniques. J Oral Maxillofac Surg 1988; 46: 721-726. Robinson P. Articular cartilage of the temporomandibular joint+an it regcncratc? Huntcrian Lecture, Royal College of Surgeons of England 1992: Novcmbcr. Hopkins R. Personal communication. Luz J, Jaeger R, DeAraujo VC, DeRezende JR. The elfect of indirect trauma on the rat temporomandibular joint. Int J Oral Maxillofac Surg 1991; 20: 48 52. Wilkinson T; Marynuik G. The correlation between sagittal anatomic sections and computerised tomography of the TMJ. J Craniomandib Pratt 1983; I: 37-45.
The Author R. P. .Juniper Department of Oral and Maxillofacial John RadclilTe Hospital Headington . Oxford OX3 9DU Correspondence
and requests
Paper received 11 March 1993 Accepted 3 September 1993
Surgery
for ofTprints to R. P. Juniper