Cineradiographic analysis of temporomandibular joint physiology

CINERADIOGRAPHIC ANALYSIS OF TEMPOROMANDIBULAR JOINT PHYSIOLOGY HARRISON

Philadelphia,

M.

BERRY,

JR.,

D.D.S.,M.Sc.,* AND F. ALLAN

Pa., and Lancaster,

HOFMANN”*

Pa.

means the production of x-ray motion pictures by means image-intensifying tube. In its broad sense, it also includes the analysis of the resulting films. The cineradiogram records the details of the morphology of an organ or part in each phase of its functional cycle, reproducing the functional dynamism of the organ. As for the analysis or interpretation of these records, Campetil strikes at the heart of the problem by stating, “Even the trained eye and mind, however, are not able to perceive and coordinate the multiple functional changes that occur in one or more structures within an interval shorter or longer than the integration time of human vision. This interpretation based solely on the observation of the images present on the projection screen is subjective, and is limited by the human sensorial powers. When objective and quantitative evaluation of these phenomena is required, or when a clinical or scientific investigation of a subject that is not well known is pursued, special cinefluorographic analysis becomes essential.” This article describes the application of kinetics (the effect of forces upon the motion of material bodies, utilizing Cartesian coordinates) in the study of a cineradiographic record of condylar motion during mastication. The analysis concerns 237 frames of a cineradiographic study of a functioning mandibular condyle. By data reduction methods, to be described later, reproduction of the frames are included. To make an objective and quantitative evaluation of the phenomena recorded on the film, the dynamic processes have been defined by assigning finite mathematical values to points on the image border of the moving condyle, using x-y coordinates. The motion of these points is then reduced to a line graph, and, since a given number of frames (pictures) per second is inherent in a cineradiographic recording, the movement is related to time as well as to space. The study, therefore, may be considered an exercise in applied biometrics with clinical application.

C of an electronic INERADIOGRAPHY

Read before the Academy of Denture Prosthetics, Miami Beach, Fla. A preliminary report presented before The American Academy of Restorative Dentistry, Chicago, Ill. This investigation was supported by a research grant D-240 from the National Institute of Dental Research, U.S. Public Health Service. The cinefiuorographic unit described was made available to the Lancaster Cleft Palate Clinic by a research grant from the Gustavus and Louise Pfeiffer Research Foundation. *Professor and Chairman of the Department of Roentgenology, University of Pennsylvania School of Dentistry. **Director, Technical Research, Lancaster Cleft Palate Clinic. was

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PILOT

STUDY

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Certain facts concerning the programming and execution of this study must be presented at the outset. It was conceived as a pilot study with two main objectives : (l), to design a technique of producing motion pictures directing the rays vertically through the condyle (an inferosuperior projection), and (2) (predicated on the success of number one) applying previously designed methods of data reduction and analysis, and refining and improving upon them. The research design would provide a pattern or problem-solving format to serve as a basis for future controlled studies. Following Cooper’s” astute prediction of the value of cineradiography in clinical dental diagnosis and research, we have devoted much effort to solving the technical problems involved in producing good quality cineradiograms of the temporomandibular articulation, using transcranial and anteroposterior projections. We also developed a program of data reduction and analysis involving a Boscar punch card-electroplotter system. These results have been published previously.B-5 The inferosuperior projection had ndt been attempted, chiefly because of the physical arrangement of the cineradiographic equipment. The x-ray tube was mounted at one end of a rigid horizontal bar, the image-intensifying tube at the other, the x-ray beam being parallel with the floor. Thus it was not readily adaptable for vertical projection of the beam. To provide better accessibility for positioning the patient’s head, it was decided to design a hydraulically operated ceiling-mounted assembly. In the process of this changeover and while the unit was partially disassembled, the tubes were temporarily adjusted to a vertical alignment and it was possible to make this study. For this one pilot study, the subject (patient) was selected with no specific criteria except that he have no obvious deviations from normal in his temporomandibular articulation. He was chosen at random, a person with no dental complaints. He was a man, 64 years of age, a retired dental laboratory technician. who wore complete dentures which happened to have flat plane teeth. He stated that he was well satisfied with the dentures, they caused no discomfort, and that he could “eat anything.” In other words, the patient was chosen neither because of, nor in spite of, his occlusal situation. Subjects for future studies, of course, will be selected carefully according to occlusal situations. Then the objectives will be to study condylar function related to specific types of occlusion with natural and/or artificial teeth. But for this pilot study of cineradiographic production and interpretation, the only important considerations were that he be an asymptomatic John Doe> that he be a cooperative volunteer, and that he be above the child-bearing age. CINERADIOGRAPHIC

TECHNIQUE

The subject, wearing a lead apron, was seated upright, the head extended slightly forward, and with the occlusal plane parallel with the floor. The cephalostat could not be used for this study inasmuch as its superstructure interfered with the receiving screen of the image-intensifying tube. During the filming, the subject made an effort to keep his head stationary, hut since he was chewing, some movement was inevitable; correction for this was made at the time of frame-l)y-frame

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analysis by reorienting each frame on the Boscar screen to selected fiducial landmarks. The tip of the plastic pointer cone was positioned one inch below the right gonion, the central ray angled at 15 degrees from a perpendicular to the ceiling, so positioned that the central ray passed through the condyle when the jaws were in the closed position. Thus, the center of the receiving screen was situated 9 inches above the skull, and 13.5 inches above the right condyle. Calculations showed that this alignment would produce a roentgenographic enlargement of approximately two and one-half times. In previous studies3 we have shown that with a fractional focus (0.3 mm.) rotating anode tube this amount of enlargement does not produce discernible loss of detail since the geometric unsharpness is less than the inherent unsharpness of the fluorescent receiving screen. Enlargement has the advantage of making details discernible which cannot be perceived in smaller pictures. When the head position adjustments had been made by visual observation through the viewing screen, a Polaroid camera was used to produce a spot-film photographic record of head position and exposure factors. The 16 mm. sound motion picture camera was then locked into position, and the subject was given a 1 cm. cube of raw carrot which he placed between his teeth on the right side. As he commenced to chew, the synchronous motor button was pressed, which tube, camera (at 24 framesenergized the x-ray generator, image-intensifying per-second), sound recording equipment, and lapsed-timed meter. The exposure was run for 24 seconds, at 78 KVP and 4 Ma. The dose to the patient, in air, was 1.9 r, the beam being filtered by 1.0 mm. aluminum and 0.27 mm. copper. DATA

REDUCTION

The processed film was projected at the normal frame rate and studied carefully, It was decided to remove an interesting segment of 237 frames and have them plotted according to a method we3-r’ had used originally for analyzing frames from transcranial studies of temporomandibular function. Accordingly, this segment was sent to the Data Processing Division of the University of Dayton Research Institute, with instructions for single-frame tracings and plottings. Detailed instructions were communicated to the Dayton technicians by letter and telephone. Frame #O was enlarged on the 30 inch screen of the Boscar, and a zero point for the X-Y coordinate system was selected, which was a shadow identifiable at about “7 o’clock” in all frames. A vertical and a horizontal cross hair on the Boscar screen were made to intersect at this point, and its position was recorded on a punch card and typed on read out paper. The X (horizontal) and Y (vertical) distances from 0 of several points along the border of the “basal bone” (posterior fossa wall and lateral skull wall shadow, forming the “horseshoe” shadow) were recorded in like manner. A wax pencil outline of the basal bone image was drawn on the Boscar screen. Each subsequent frame was reoriented to coincide with this fiducial line in order to correct for movement of the head 1,etween frames. h-ext, several points around the mandibular condyle and ramus image were recorded, cutting off arbitrarily at the coronoid process.

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Fig. 1.-A motion picture

photograph camera.

of a dry mandible

as the mandible

in this study n-as Tiewed by the

Fig. 2.-The condyle-ramus outline (black) was plotted from cineradiographic frames superimposed over the specimen. The medial and lateral lips of the condyle are not included in the outline because these thin structures were overpenetrated by the x-rays.

A template of the condyle-ramus image was used to record outlines of this body on each subsequent frame. When all 237 frames had been analyzed, the individual punch cards were fed into an electroplotter which stamped out the numerical values on graph paper. The marks were connected by lines, and each motion picture frame was thus converted to mathematically plotted form. ANIMATED

MOTION

PICTURE

In our own laboratory, we converted these individual plotted forms to Diazo color acetate cells and photographed them on color motion picture film in slow and normal speed, producing a colored animated movie for critical analysis. Each frame was also converted into solid black and white cells, which are reproduced in this article (see Fig. 5). The border scale along each cell represents

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Fig. 3.-A complete plotted cell is superimposed over the specimen 0 = the zero point; OY = the ordinate describing the anteroposterior motion; OX = the abscissa describing the mediolateral motion. The hatched area is “basal bone”: the fossa (bottom) and lateral skull wall are superimposed over the zygoma (along right border of the cell).

Fig. 4.-A

reproduction

of an original

cineradiographic

frame.

10 mm. on the plotted graph paper, which, it must be remembered, was produced from a radiographically enlarged motion picture frame. To relate this scale to anatomic proportions, reference was made to a still film using the same radiographic technique, with a ball bearing of 4.8 mm. diameter encased in plastic and inserted in the right auditory meatus. This film was then placed in an enlarger and the picture adjusted until its shadow matched the plotted outline. Relating the enlarged diameter of the ball-bearing shadow (12.5 mm.) to its known size (4.8 mm.) results in a 2.6:1 ratio. In other words, a 2.6 mm. unit of movement of the condyle in the cineradiographic film and in its plotted reproduction represents 1 mm. of anatomic motion, or 1 unit equal 0.38 mm., subject to enlargement limitations.

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Fig. 5.-Plotted is 10 units,

CINERADIOGRAPHIC

cells of 237 cineradiographic or 3.8 mm. of anatomic movement.

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frames. Each mark on the X and Each frame represents l/24 second.

Y

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5.-B.

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M---A

Fig.

5.-C.

1x2

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5.-F.

Since the inferosuperior projection is not commonly used in dental practice, it may be well to orient the reader. Fig. 1 is a photograph looking down on a dry mandible from the position occupied by the movie camera used in the study. The familiar almond-shaped condyle can be seen readily. Fig. 2 is the same mandible with the outline of the condyle-ramus shadow (in black) reproduced from the fihn superimposed on it. Note that the medial and lateral lips of the condyle are not included in the black image ; these thin structures were overpenetrated and burned out in the x-ray image. Fig. 3 shows the plotted cell, with the scale, “basal bone” (fossa), and condyle-ramus shadow, superimposed on the specimen. In this figure, the axis Y is in the mid-saggital plane. In the plots of the cineradio-

CINERADIOGRAPHIC

Fig. 6.-The position ramus, in area of coronoid

of point process).

C (posterior

185

ANALYSIS

border

of the condyle)

and point

n

(within

Fig. 7.-The extremes of anteroposterior motion as recorded in the study. Left, frame 27, show the ramus in its most posterior position. Right, frame 169, shows the ramus in its most anterior position. CY position in frame 27 is 9; CY position in frame 169 is 55, a difference of 46 units which indicates 17 mm. of difference anatomically.

graphic study, the Y axis is approximately parallel with the mid-saggital plane. Whatever deviation exists is constant for all frames. Fig. 4 is a photograph of a single motion picture frame from the sequence. Figs. 5 A, through F, are cell reproductions of the 237 motion picture frames, the frame number is in the upper right corner of each cell. The time between each frame is l/24 second. The total sequence represents 9.87 seconds.

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In producing these cells, two points were selected from the plotted forms and designated arbitrarily as point C-for condyle (an imaginary spot at the posterior border of the condyle), and R-for ramus (within the ramus, near the coronoid process) (Fig. 6). 1lie have introduced a small rectangular shadow in the fossa area of each cell as a reference area. Since all movement of point C took place within this area, it may help in relating gross movement of the condple from frame-to-frame without the use of a straightedge. Fig. 7 shows the extremes of movement anteroposteriorly, frames 27 and 169. It must be kept in mind that this is a graphic record in two planes of movement of a body moving in three planes. Whenever the black condyle form ntoves up (an increase along Y), it is recording an opening movement in which the condyle is sliding down the posterior slope of the eminentia as well as moving anteriorly. A decrease in Y indicates a closing movement in which the condyle travels up the posterior slope of the eminentia as well as posteriorly. An increase or a decrease along the S axis depicts, respectively, an outward or a medial shift in a lateral direction.

Fig. positions

AREA

8.-The of point

OF

“area of activity,” C in 237 frames.

or

outline

of

the

extreme

nvx?ial,

posterior,

and

lateral

ACTIVITY

With the cineradiographic data reduced to this form, the extreme boundaries of the movement of point C were plotted to define its “area of activity” (Fig. S). Note that all activity involving any degree of mediolateral movement took place in an area anterior to the Y-15 level. The one retrusion to the back wall of the fossa occurred in frame 27, and this one excursion to Y-9 identifies the most posterior position point C reached in the entire chewing sequence. This intriguing phenomenon tempts one to interpret it to clinical advantage, hut such

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a desire should be restrained, at least until more controlled studies of this type have been made. The diagram defines the area of activity of only one individual in only 237 frames of a chewing exercise. It does not say whether the condyle went beyond these boundaries in earlier or later portions of the exercise, although, in nearly 10 seconds of chewing, this diagram probably includes most of the extreme positions reached. Whether this is a typical area of activity diagram which this patient would repeat, or other patients would exhibit, is certainly unknown; we will attempt to find out, however, with additional studies. Since centric relation was not determined in this study, the X-Y values of the C and R points in centric relation are unknown. Therefore, it is not known whether centric relation is exhibited in any of the plotted frames, although it is known that persons do not necessarily chew in centric relation, but probably “chew through it.” In future studies, several feet of film will be run while the patient’s mandible is in centric position and before the subject starts chewing. Thus the X-Y value of centric relation can be determined, and placed on punch cards, and, with proper programming, a computer can conduct a search for subsequent frames which show these same values. LATERAL

MOVEMENT

OF

THE

CONDYLE

Attention is again called to frame 27, the most posterior position of the condyle in this sequence. Frames 28, 29, and 30 show the condyle moving from this position in a forward and outward direction which is compatible with the classical definition of Bennett movement. Bennett’s6 original description of the movement which now bears his name occurred during “. . . extreme lateral movement, with the teeth in continuous occlusion”. He noted that “. . . in movement towards the side on which the condyle might be expected to remain stationary there is a quite considerable movement of the condyle outwards away from its articular surface, and slightly downward.” The Bennett movement is usually recorded as a condylar path followed when movements are made from centric occlusion outward with the teeth in contact. However, Isaacson holds that, “The Bennett movement is a component of the more complex excursive movement.” Page* describes it as a component of the natural functional jaw movements, while Granger” states that, “The mandible can execute various degrees of the Bennett movement in various lateral protrusive paths, and varying degrees of opening, or tooth contacts.” These concepts attribute rather wide latitude to this movement. Furthermore, as SicherlO says, “In mastication the lateral movement is utilized in the reverse direction as the masticatory stroke,” or, as Grange+ puts it, “. . . it is actually used in the opposite direction.” Two interesting movements are shown in Figs. 9 and 10, which consist of color acetate overlays. Fig. 9 shows a lateral movement in frames 100, 101, and 102. Fig 10 shows a pivotal swing around point C in frames 130 and 131. To provide a more compact method of analyzing the diverse chewing movements, a line graph was constructed (Fig. 11). The bottom graph, CY, indicates the travel of point C in the Y direction; above it, CX, is the excursion of point C in a lateral direction along X; next RY, the movement of point R in its Y excur-

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1964

Fig. 10.

Fig. 9.-Acetate overlay cells from three frames depict the anterolateral glide in frames 100, 101, 102 (left to right). Fig. lO.-Transparent acetate overlays made from frames 130 and 131. They show a pivotal motion to the right around Point C (Fig. 6).

sions; and at the top, the graph of point R in its X direction. Along the left margin is the scale of units taken from the plots made from the original cineradiographic frames. Each of the four graphs has its own unit scale; CY graph goes from 10 to 50 Y units; CX graph goes from 40 to 68 X units; RY goes from 85 to 125 Y units; and graph RX goes from 20 to 55 X units. Each unit equals 0.38 mm. of anatomic movement. The scale along the bottom indicates the frame numbers, from frame 0 to 237. The film was made at 24 frames per second, therefore, the travel of points C and R are plotted against this time base. Each line represents 5 frames, or .5/24 second. From this graph, it is easy to see how one or both points (C or I?) are moving in both an anteroposterior (Y) and medial-lateral (X) direction. The full significance of this analysis will be realized in conjunction with presently planned studies, but even in its present graph form it offers much food for thought. METHODS

OF ANALYSIS

A few examples of methods of analysis are suggested. A straight line indicates an excursion with linear velocity. A good example is found in frames 62-65, where point C goes from Y35 to Y16 in a straight line. This is a closure of linear velocity, traveling 19 units (7.2 mm.) in 3 frames (0.125 sec.). The CX component for these frames is nearly a plateau (CX 54, 55, 56), so this closure occurred with essentially no lateral deviation.

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ANALYSIS

The CY graph shows 26 anterior (increase of Y) excursions of linear velocity, each excursion starting from, and ending with, a complete reversal of direction. Five of these consisted of only 1 unit travel (0.38 mm.) in 1 frame (l/24 sec.), which is dissecting the movement to very fine proportions. There are 2 excursions of linear velocity of 2 units (0.76 mm.) in 1 frame (l/24 sec.). There are 4 linear velocity openings of 5 units (1.90 mm.) in 1 frame (l/24 sec.). The greatest amount of linear velocity opening occurs in frames 121-122, when point C travels 11 units (4.2 mm.) in l/24 sec. In two excursions (frames 116-119 and 227-230) there is linear travel of 21 units (8 mm.) in 3 frames (l/S sec.). The largest excursions are not of linear velocity. There is a lag at the start and/or end, or in the middle. In all of the closures of greatest magnitude there is a perceptible lag at the initial phase. (This clearly seen in graph form, but was not recognizable in the projected film.) For example, note the closures in frames 88-91, 97-100, 134-138, 159-164, 169-177. Our thinking is that this is evidence of the “split-second timing” so often referred to by Sicher.12 Speaking of the importance of timing in the function of the neuromuscular mechanism, he states, “If the mouth is opened maximally, . . . then if the jaws are closed, it is of greatest importance that the external pterygoid muscles, which are maximally contracted at the end of the opening phase, relax a split second before the elevators and retractors go into action.”

Fig. Il.-Line graphs of X and Y motion bottom scale Is time (24 frames = 1 second).

of points

C and R. Left

scale is Jn units;

the

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J. Pros. &IT. Jan..Feb., 1964

Analysis progresses by combining two or more excursions into “events,” and “events” into “cycles.” This study per se contains much food for thought, but, even more important, it provides a springboard for further studies, guidelines for conducting them, and therein means of gaining insight into the physiology of the stomatognathic system. The authors wish to express their appreciation to their colleague, Mr. Richard M. Miller, for his assistance in the production of audiovisual materials. REFERENCES

1. Campeti, F. L.: Diagnostic Analysis of Cinefluorograms in Ramsey, G. H. S., Watson, J. S., Jr., Tristan, T. A., Weinberg, S., Cornwell, W. S. : Cine-Fluorography, Springfield, Ill., 1960, Charles C Thomas! Publisher, pp. 159-171. 2. Cooper, H. K., and Hofmann, F. A.: The Application of Cinefluorography With Image Intensification in the Field of Plastic Surgery, Dentistry, and Speech, Plast. & Reconstruct. Surg. 16:13.5-137, 1955. 3. Berry, H. M., Jr., and Hofmann, F. A.: Cinefluorography With Image Intensification for Observing Temporomandibular Joint Movements, J.A.D.A. 53:517-527, 1956. 4. Berry, H. M,, Jr., and Hofmann, F. A.: Preliminary Work on Cinefluography, With Image Intensrfication, in the Study of the Temporomandibular Joint, Oral Surg., Oral Med. & Oral Path. 10:63-68, 1957. 5. Berry, H. M., Jr., and Hofmann, F. A.: Cineradiographic Observations of Temporoman; dibular Joint Function, J. PROS. DEN. 9:21-33, 1959. 6. Bennett, N. G.: Contribution to the Study of the Movements of the Mandible, Proc. Roy. Sot. Med., pp. 79-95, 1908; J. PROS. DEN. 8:41-54, 1958. Isaacson, D.: Clinical Study of the Bennett Movement, J. PROS. DEN. 8:641-49, 1958. s7 Page, H. L. : The Bennett Movement, D. Digest 5’7:412-414, 1951. 9: Grangerr7Eig5t : Functronal Relations of the Stomatognathic System, J.A.D.A. 48 :63810. Sicher, H:: Functional Anatomy of the Temporomandibular Joint iti Sarnat, B. G., editor: The Temporomandibular Joint, Springfield, Ill., 1951, Charles C Thomas, Publisher, pp. 3-40. Granger, E. R. : Centric Relation, J. PROS.DEN. 2:160-171, 1952. ::: Sicher, H.: Positions and Movements of the Mandible, J.A.D.A. 48:620-625, 1954. 4001 SPRUCE

ST.

4, PA.

PHILADELPHIA

24 N.

LIME LANCASTER,

ST.

PA.