Analysis of temporomandibular joint function after orthognathic surgery using condylar path tracings Richard P. Harper, DDS, FRCD(C)* Hamilton, Ontario, Canada
Condylar path tracings provide quantitative and qualitative data regarding the functional status of the temporomandibular joint. This study was designed to identify the functional status of the TMJ by means of condylar path tracings before treatment and to monitor the response of the TMJ to orthognathic surgery. Baseline data for condylar tracings using a sagittal recording device were established in relation to normal limits for opening, protrusive, and medial excursions of the mandible. In 54 patients 108 joints were studied before and up to 1 year after orthognathic surgery. Internal derangements were identified with condylar tracings before treatment in 72% of all joints studied. Also, condylar tracings identified internal derangements that were not found on clinical examination in 11 of 39 patients. Functional adaptation of the TMJ was found to be more favorable for mandibular reduction and maxillary impaction than for mandibular advancement or combined upper and lower jaw procedures. Condylar path tracings were shown to represent a noninvasive technique to identify and monitor the functional status of the TMJ in response to surgical orthodontics. (AMJ OFITHODDENTOFACORTHOP1990;97:480-8.)
S u r g i c a l alterations of the facial skeleton in patients with dentofacial deformity produce adaptive changes in the musculature controlling jaw position and function. ~'7 Little is known, however, regarding the functional status of the temporomandibular joint (TMJ) in these patients before surgical orthodontic treatment or the biomechanical changes that occur in the TMJ after treatment. 8~2 Standard treatment planning and analysis of results for surgical orthodontic patients have essentially involved the collection of morphometric and cephalometdc data. t3t6 Functional analysis generally involves measurement at the incisors of opening and excursive movements of the mandible and a qualitative assessment of condylar movement and TMJ sounds. Temporomandibular joint radiography provides important information regarding the structural and biologic status of the joint and, although TMJ arthrography and magnetic resonance imaging can provide data regarding the functional status of the TMJ, these modalities are not routinely used as part of the diagnostic evaluation of a patient with dentofacial deformity. ~72t Tracing of the condylar pathway during mandibular movement is a noninvasive diagnostic technique that allows quantitative and qualitative analysis of TMJ function. 22"23 With a sagittal recording device, diskcondyle incoordination can be seen as a deviation or *Associate Clinical Professor, Department of Surgery, McMaster University Medical Center. 8/!/14351
480
obstruction in the tracing pathway. Condylar path tracings of mandibular movement have been reported to have diagnostic significance.2427 However, no baseline data regarding normal tracing patterns for a population group without a history or clinical evidence of TMJ internal derangement have been established. The purpose of this study was to establish baseline data regarding the normal limits of condylar path tra0ngs for opening, protrusive, and excursive mandibular movements in a population of patients with no history or clinical evidence of TMJ internal derangement. This was done with the use of a sagittal recording device. Also, the functional status of the temporomandibular joints in patients undergoing surgical orthodontic treatment of dentofacial deformities was investigated by means of condylar path tracings. METHOD To establish baseline data in relation to the normal limits for condylar path tracing lengths, 25 patients (8 men and 17 women, 18 to 36 years of age) who were undergoing surgical orthodontic treatment were identified. None of them had a history or clinical evidence of TMJ internal derangement. Patients were also classified according to standard cephalometric and morphometric analysis into four treatment groups: mandibular prognathism (8 patients), mandibular retrognathism (6 patients), maxillary excess (6 patients), and a combination of maxillary and mandibular dysplasia (5 patients). The examination included TMJ palpation, aus-
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Analysis of TMJ after orthognathic surgery 481
Fig. 1. The sagittal recording device (Axiograph) shown in place. The recording bow is fixed to mandible with mounting stone over lower anterior teeth. The upper component is stabilized over cranium and holds templates with millimeter graph paper in area lateral to mandibular condyles.
cultation, and range of motion measured at the incisors. Condylar path tracings were recorded for maximum opening, protrusion, and medial excursion of the mandible by means of a sagittal recording device (Sam Axiograph, SAM Prazisionstechnik Taxisstr, Munich, West Germany). The lengths of each opening, protrusive, and medial condylar tracing for fight and left sides were measured, and the mean~ and standard deviations were recorded before and up to 1 year after orthognathic surgery. In another group of 33 patients (age range 18 to 36 years, including 27 women and 6 men) being treated for dentofacial deformities condylar path recordings were made before and up to 1 year after orthognathic surgery. In each of these cases there was clinical evidence of internal derangement in the form of palpable or audible clicks in one or both mandibular joints. These patients were also classified according to facial deformity and included the following: mandibular prognathism (9 patients), mandibular retrognathism (12 patients), maxillary vertical excess ( 7 patients), and a combination of maxillary and mandibular dysplasia (5 patients). The tracings for all three condylar movements were similarly measured and the means and standard deviations were recorded. The paired t test was used to determine significance within each group between preoperative and postoperative values. A second study was completed to determine the effects of orthognathic surgery on TMJ function. Condylar path tracings of 108 temporomandibular joints in 54 patients with dentofacial deformities were analyzed. A surgical-orthodontic history and physical examination were completed for each patient. This included
documentation of TMJ function with palpation, auscultation, and range-of-motion data. The functional range of the mandibular opening and lateral excursions was also measured in millimeters in relation to the midline of the upper incisors at each phase. The patients were divided into the following treatment groups: maxillary LeFort I impaction (13 patients), mandibular sagittal split reduction (13 patients), mandibular sagittal split advancement (18 patients), and combined maxillary and mandibular osteotomy (10 patients). The study included 42 women and 12 men 18 to 36 years of age. Condylar path tracings were taken in each group before surgery and up to 1 year after surgery. The sagittal recording device consists of a recording bow fixed to the mandible with mounting stone over the lower dentition (Fig. 1). Movement of the mandible, therefore, is directly translated to the recording arm of the instrument. The lateral arms of the recording bow are adjustable to facilitate the axis point determination. The upper component of the instrument is stabilized over the cranium; it holds templates with millimeter graph paper in the region lateral to the temporomandibular joint and also marks the orbital point, allowing transfer of the orbital-axis line to the graph paper. The axis of rotation of the mandibular condyles was determined by rotational analysis, using the fixed mandibular clutch with adjustable arms of the recording bow to mark the axis point on graph paper of the flag bow positioned in the preauricular area (Fig. 2). Once the condylar axis is determined, a recording gauge was inserted at the axis point. Tracings of condylar movement are made with the mandible moving in the protrusive-retrusive pathway, the opening-closing path,
482
Am. J. Orthod. Dentofac. Orthop. June 1990
Harper
Fig. 2. The recording bow of Axiograph fixed to mandibular arch is adjusted toward center of arc as mandibular condyle rotates in first 10 to 15 mm of an opening-closing pathway. This center point is the axis of rotation of mandibular condyle.
Fig. 3. The axis of rotation of condyle is marked on 1 mm graph paper of the flag bow overlying TMJ (left). A recording gauge is inserted at axis point (right) and pathway of condylar axis is traced through protrusion-retrusion, opening-closing, medial, and medial-retrusive pathways.
the medial path, and the medial-retrnsive path (Fig. 3). The axis-to-orbital line was subsequently drawn on each tracing, and the angle taken by the condyle in the opening pathway was measured in relation to this line. Quantitative analysis of the condylar path tracings is based on the length of each tracing, the curvature of the tracing, and the position of distortions in the tracings produced by a disk-condyle interference relative to the axis point. RESULTS
The means and standard deviations for opening, protrusive, and medial excursive condylar path tracing lengths in 25 patients with no history of clinical findings of TMJ internal derangement before and up to 1 year after orthognathic surgery are shown in Table I. These
results represent analysis of 50 condylar path recordings. The paired t test found no significant difference between the preoperative and postoperative ranges of condylar translation for all three movements. Table II shows the means and standard deviations of condylar path tracing lengths for opening, protrusive, and medial excursions for 33 patients showing dentofacial deformity and clinical evidence of TMJ internal derangement in one or both joints before and after orthognathic surgery. Although the standard deviations in this group are wider than those in the control group, the t test for unpaired data shows no significant difference between the means. However, the range of condylar translation in each of the mandibular movements measured 6 to 12 months after orthognathic surgery in the group with preexisting TMJ internal derangement
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Analysis of TAIl after orthognathic surgery
483
Table I. Measurements of condylar path tracings before and after orthognathic surgery in 25 patients with no history or clinical findings of TMJ internal derangement [
Right
I
Left
Presurgery Opening Protrusive Medial
13.7 ± 2.6 (14) 9.8 ± 2.7 (9.5) 12.6 ± 2.5 (13)
14.1 ± 1.9 (14) 10.2 ± 2.6 (10.5) 13.8 ± 2.0 (13.5)
12.5 ± 2.3 (13) 8.0 ± 1.7 (8) 12.3 ± 1.8 (13)
12.5 ± 2.3 (12) 8.0 -+- 1.9 (8) 13.1 ± 2.0 (12.5)
Postsurgery (6 mo to 1 yr) Opening Protrusive Medial
The t test shows no significant difference between orthognathic surgery tracing lengths before and after surgery.
Table II. Measurement of condylar path tracings in 33 patients presenting with clinical signs of TMJ internal derangement before and after orthognathic surgery Right Preorthognathic surgery Opening Protrusive Medial
[
Left
13.2 _ 4.1 (15) 10.5 ± 3.0 (10.5) 14.1 ± 2.9 (15)
12.7 ± 3.8 (14) 10.3 ± 2.4 (10) 14.6 ± 1.9 (15)
10.1 ± 4.1 (10)* 7.8 ± 2.8 (8.5)** 11.3 ± 3.6 (12)**
10.1 ± 4.2 (10.5)* 8.1 ± 2.7 (8.0)** 11.9 ± 3.4 (12)**
Postorthognathic surgery (6 mo to 1 yr) Opening Protrusive Medial
Paired t test shows significance between tracings before and after orthognathic surgery: *p < 0.01; **p < 0.001.
Table III. Assessment of TMJ dysfunction in surgical-orthodontic patients Patients (N = 54) 5 8 6 20 9 6
Part of the chief complaint (findings)
Examination* (findings)
Condylar pathway tracing (findings)
None None Positive Positive None Positive
None Positive None Positive None None
Positive Positive Positive Positive None None
*Examination consists of: Palpation, auscultation, and range of motion.
was significantly reduced as compared with pretreatment values for opening (p < 0.01), protrusion (p < 0.001), and medial excursions (p < 0.001). In a separate study, analysis of condylar path tracings of temporomandibular joints in 54 patients undergoing surgical orthodontic treatment showed 39 patients (72%) had evidence of internal derangement (Table III). However, I 1 of these patients had no clinical evidence of TMJ dysfunction. The condylar path tracings also
confirmed internal derangements in all 28 patients with positive clinical findings. Of the 108 joints studied, 60 (56%) showed evidence according to condylar path tracings of TMJ internal derangement before surgery, whereas after surgery the number of joints With evidence of internal derangement was reduced to 47 (44%) (Table IV). After surgery, 17 of the 60 (28%) dysfunctional joints showed normal condylar path tracings and no evidence on clin-
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Am. J. Orthod. Dentofac. Orthop. June 1990
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Table IV. Effects of surgical-orthodontic treatment on TMJ internal derangements based on condylar pathway tracings Classification Mandibular reduction Mandibular advancement Maxillary LeFort I Combination surgery TOTAL(percent is the average)
I
Total joints analyzed per group 26 36 26 2._.__00 108
Presurgical internal derangements I I (42%) 24 (67%) 15 (58%)
I I
Postsurgical internal derangements 6 (23%) 21 (58%) 8 (31%)
10 (50%)
lZ (60%)
60 (56%)
47 (44%)
Table V. Alterations in disk-condyle coordination after orthognathic surgery determined by condylar
pathway tracings
Classification
CPT within normal limits presurgery changed to obstruction or clicks postsurgery
Clicks or obstruction presurget), changed to CPT within normal limits postsurgery
Mandibular reduction Mandibular advancement Maxillary LeFort l Combination surgery
0f 15 1/ 12 1/ 11 2/10
5/11 4/24 8/15 0/10
8%
28%
TOTALCHANGES
CPT, Condylar pathway tracing. NOTE: Number of joints showing changes in CPT/totaI joints.
ical examination for abnormal joint function (Table V). Eight of the 15 (53%) dysfunctional joints in the maxillary group and 5 of the 13 (39%) in the prognathic group had normal function after treatment, according to examination and condylar path tracings. One of 11 normal joints in the maxillary LeFort I group showed abnormal tracing patterns after orthognathic surgery. In the mandibular advancement group, 4 of 24 (17%) dysfunctional joints had condylar path tracings within normal limits after orthognathic surgery and one of the 12 joints that were normal before treatment showed abnormal tracing patterns after orthognathic surgery. None of the joints in the combination group showed improvement after surgery. However, of the 10 joints in this group with tracings that were within normal limits before surgery, two showedabnormal tracing patterns after orthognathic surgery. DISCUSSION
Surgical correction of dentofacial deformities has been shown by Karabouta and Martis 28 and Magnusson et al. 29 to improve the signs and symptoms relating to TMJ pain and dysfunction. On the basis of similar parameters of TMJ assessment, the findings in this study generally agree with their results. There was an overall decrease in the reported occurrence of headache and
pain on mandibular function and an increased satisfaction with chewing efficiency. However, condylar path tracings revealed abnormalities in the biologic status of the joint that were not detected on clinical examination or that were not reported by the patient in the clinical history. Van Willigen 23°used a sagittal recording device and included simultaneous phonograms and electromyography when comparing the condylar movement patterns in normal TMJs with the condylar movement patterns of joints with disk-condyle incoordination. He was able to show deflections and changes in the speed of condylar movement before clicks in the dysfunction group. This type of investigation provided a visual record of the disk-condyle relation and valuable information regarding the mechanism of the dysfunction. Mongini and Capurso 24 studied pantographic tracings of mandibular border movements in patients with TMJ dysfunction. Their studies concluded that both neuromuscular and articular abnormalities were reflected in the tracing patterns. Shields et al. 3~ and Simonet and Clayton 32 reported a positive correlation between condylar tracings and TMJ dysfunction. It is noted in this report that although the standard deviations for opening, protrusive, and medial excursive movements for the group of patients with evidence of TMJ dysfunction are wider than in the control group, the means are signif-
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icant only in the posttreatment analysis. These results suggest that functional rehabilitation of the TMJ may be compromised for patients with preexisting TMJ internal derangement. Also, analysis of the condylar path tracings must evaluate both the quantitative and the qualitative features of the recordings. According to condylar path tracings, improvements in the functional patterns of the joint after orthognathic surgery were shown to occur. Alterations in diskcondyle coordination seem to relate to the nature of the preexisting derangement and to the type of surgical procedure performed. Clicks were more likely to be resolved after prognathic reduction and maxillary impaction surgery than after mandibular advancement or combination maxillary and mandibular surgery. The sagittal split reduction osteotomy is more likely to result in a slight anterior rotation of the condylar head that would predispose it to improved coordination of diskcondyle function. However, the sagittal split advancement osteotomy tends to rotate the condylar head posteriorly and would tend to a disk-condyle incoordination. Any maneuver that would force the condylar head in a posterior or superior direction may precipitate an internal derangement in a joint that is already predisposed to incoordination. The findings of mandibular hypomobility after orthognathic surgery may be explained in terms of TMJ internal derangement. The results of condylar pathway tracing studies support the finding by Storum and Bell 33 of a higher incidence of hypomobility after mandibular advancement osteotomy but improved function after LeFort I osteotomy and mandibular reduction osteotomy. Results of the condylar pathway tracing studies suggest that improvements in disk-condyle coordination are more frequently seen after LeFort I osteotomy. These results may be attributed to improved neuromuscular balance in the absence of condylar manipulation by the surgeon. Combined maxillary and mandibular procedures tend to show poor results in terms of temporomandibular joint rehabilitation. A major reason for these findings relates to the fact that this group shows a high degree of internal derangement combined with significant adaptive condylar changes before surgical orthodontic treatment and that the potential for unfavorable condylar manipulation in this group is higher. The adaptive phase for these patients may, in fact, extend well beyond a 1-year posttreatment period. The condylar path tracing is a noninvasive diagnostic technique that provides graphic data pertaining to the functional and biologic status of the temporomandibular joint. A normal condylar path tracing occurs
Analysis of TMJ after orthognathic surgery 485
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