The postcondylar cartilage graft—An evaluation of an alternative surgical method for the treatment of retrognathia

The postcondylar cartilage graftAn evaluation of an alternative surgical method for the treatment of retrognathia

Dr. Banks

P. Banks, M.B., B.S., F.D.S., R.C.S. Sussex, England Postcondylar cartilage grafts were used for 6 years to advance the mandible surgically in adolescent patients with retrognathia. Thirty-seven subjects were treated; of these, 30 were followed for more than 1 year and have been analyzed. Relapse occurred in 9, caused mainly by displacement of the graft. In the stable group temporomandibular joint changes were studied. Progressive calcification of the graft occurred and a normally functioning joint was established in the advanced position. Improvements in surgical technique-in particular, the fixation of the graft-produced consistent stability in the later cases.

Key words: Retrognathia, mandibular, transplant, cartilage, condyle, surgery

I

n 1954 Trauner’ described a technique for the surgical treatment of retrognathia whereby a block of autogenous cartilage was placed between the bony external auditory meatus and the posterior surface of the mandibular condyle to advance the whole mandible. Banks and Ardouin’ reviewed the subsequent scant literature and presented a preliminary report on 9 patients similarly treated and followed for a maximum of 24 months. In these early cases the postcondylar graft consisted of either autogenous or stored lyophilized allogeneic cartilage. The results were encouraging and suggested that this was a relatively simple operation with low morbidity that was skeletally stable (Figs. 1 and 2). In 1981 Brown and Banks3 presented an intermediate report on 15 patients followed from 5 to 37 months. By this time it was clear that the original surgical technique described by Trauner and used subsequently by Lenart, Poswillo,’ Lachard and Vitton6 and Vitton and associates’ did not stabilize the postcondylar graft adequately in the retrocondylar space. If the graft became displaced partially or totally, relapse occurred and, in order to prevent this, Brown and Banks suggested an alternative surgical technique. The operation was used initially to treat adolescent patients who had Class II, Division 1 malocclusion with moderately severe retrognathia. It was realized that there were a number of theoretical contraindications to advancement of the mandible by means of a postcondylar cartilage graft. There is a deliberate distortion of 406

the temporomandibular joint anatomy. The operation cannot always achieve definitive correction of the occlusion, and the technique does not take into account the changes in the line of action of the mandibular musculature. On the other hand, the operation was simple for the patient, especially when lyophilized bank cartilage was used, and did not require any intermaxillary fixation. (In fact, it became common practice to rest the jaw for 7 to 10 days with intermaxillary fixation because this eliminated virtually all postoperative discomfort.) The operative morbidity was less than with sagittal split osteotomies, and many patients were more prepared to accept the postcondylar graft when the two options were explained. It was eventually used mainly for those patients who were not prepared to tolerate a long period of fixed appliance therapy, but also for a few patients who had been treated unsuccessfully with myofunctional appliances. All the patients were selected by the orthodontic service for surgical treatment and most required and accepted some period of adjunctive removable appliance therapy. The theoretical contraindications mentioned above influenced the selection of cases. It was believed that if adolescent patients were treated there would be more likelihood that adaptive growth would compensate for change in position of the temporomandibular joint and also permit spontaneous or assisted postsurgical occlusal correction. In a high proportion of the early cases so treated, these expectations were realized and a pre-

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Fig. 1. A, Preoperative profile taken June, 1978, at the age of 12 years. This was one of the youngest patients in the series. In most cases it is better to delay surgery until after puberty. B, Postoperative profile 5 years later.

liminary protocol for future selection was established as follows in skeletal Class II, Division 1 cases of moderate severity: 1. Mandibular advancement to a maximum of 12 mm-more than this is usually impossible by this technique because this is the approximate limit of protrusion. 2. Age usually 14 to 16 years-that is, just after the pubertal growth spurt. At this age further simple postoperative orthodontic methods were usually accepted. The results of surgery carried out at a younger age had been unpredictable because of individual variations in growth pattern (Figs. 1 and 8). 3. Intermaxillary fixation for 7 to 10 days o:nly. This was necessary to allow the minimal postoperative swelling to subside for the patients’ comfort. Without some period of intermaxillary fixation, movement in the first few days was unacceptably painful. 4. Sufficient upper incisor proclination to allow an adequate skeletal advance (usually 105” to SN). 5. Postsurgical removable appliance therapy to control the interincisal relationship, particularly when a lateral open bite was created. It had been found that lateral open bite following postcondylar grafts invariably closed rapidly and spontaneously,3 but this

was often achieved by an increase in overbite rather than eruption of posterior teeth (Fig. 3). This article is a report on the results of 5 years’ experience using the postcondylar cartilage graft. Although a relatively large number of patients were treated and followed, the surgical technique, in the light of experience, needed modification. Standardization of the technique has been achieved only for the past 2 years. The early reports’s 3 drew attention to the importance of stable fixation of the cartilage graft. The purpose of the present article is to evaluate the functional and radiographic changes observed in the temporomandibular articulation and to describe the evolution of the surgical technique. Some conclusions concerning skeletal stability can be reached at this stage, but analysis of the whole series to date must take into account the surgical developments along the way. PATIENTS AND METHODS

Largely within the criteria outlined above, 37 cases were treated by postcondylar cartilage graft over a 6year period. There have been two total failures due to early postoperative infection of either side. Thirty of these patients were followed for more than 1 year and were subjected to analysis in the present article.

408

Banks

DW -

Pre op June78

------

hnm post op DW

. .._ -...-

April

-

March

79 83

Fig. 1 (Cont’d). C, Immediate pre- and postoperative lateral cephalometric tracings to show mandibular advancement and the lateral open bite created in the molar region. D, Lateral cephalometric tracings taken 10 months after the surgical procedure and 4 years later. The earlier tracing demonstrates closure of the lateral open bite while the patient was wearing a simple removable appliance to maintain the interincisal relationship. The later tracing demonstrates further forward growth of both jaws with no relapse of the overjet.

Fig. 1 (Cont’d). E, Full-face appearance postoperatively.

5 years postoperatively. F, Mandibular Normal lateral and protrusive movements were present.

opening 5 years

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The median age of the group at operation w.as 15.3 years, and the mean follow-up period was 38 months. Mandibular advancement ranged from 5 to 14 mm (mean, 8.6 mm). Lyophilized allogeneic bank cartilage was used in 21 cases and autogenous costal cartilage in 9 cases. Changes in the temporomandibular articulation were monitored from serial lateral tomograms, together with posteroanterior and occipitomental radiographs. Serial clinical examinations of the range of join: movement was carried out, and abnormal signs and. symptoms were recorded. Cephalometric

JL

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499

Aug 77

-_-----__ Jul 78 Aug 82 i)

:

analysis

In all cases standard, lateral cephalometric radiographs were taken preoperatively, during the brief period of fixation, immediately after release of fixation, and at regular intervals thereafter. Since the whole mandible was displaced forward and further growth of the facial bones took place in many patients, cephalometric assessment presented some problems. Previous analyses of relapse after mandibular advancement** 9 employed measurements such as condylion-pogonion and gonial arc tracings to assessmandibular stability; however, as the cases shown in Figs. 4 and 8 demonstrate, postcondylar graft cases do not readily lend themselves to such analysis because of variable further growth. Serial radiographs in each case were superimposed, using the best fit of sella, anterior cranial fossa tracings, and nasion. In each case the anteroposterior position of pogonion was serially recorded by dropping a perpendicular from the sella-nasion line and measuring the distance forward of sella. The stability of the chin point was an index of the clinical effectiveness of surgery, but not necessarily the stability of the postcondylar graft itself (Fig. 4). Temporomandibular

Pre-op

cartilage

joint

analysis

A more accurate evaluation of the operation was obtained from analysis of the changes around the temporomandibular joint. Serial linear tomograms in the sagittal plane were taken immediately postoperatively, and at 3-month and 6-month intervals thereafter. Tomograms were taken with the teeth in occlusion and with maximum opening of the mouth. For the purpose of comparison, a tracing of the best film from each tomographic series was made. It included the bony external auditory meatus, the wire retaining the postcondylar graft, the articular fossa and eminence, and the outline of the graft where calcification was present.3 In addition, the position of the wire retaining the graft was monitored from serial posteroantet-ior and occipitomen-

Fig. 2. Lateral cephalometric tracings of male patient. Bilateral autogenous postcondylar grafts were carried out in September, 1977, with 14-mm advancement when the patient was 14 years 6 months of age. The continuing skeletal stability after discontinuation of postopfxative retention by a removable appliance is demonstrated.

tal radiographs. The following parameters were recorded: 1. Condylar advance as determined by the anteroposterior dimension of the block of cartilage recorded at the time of surgical intervention. 2. Stability of fixation of the graft. Displacement of the graft was assumed to have occurred if displacement or breakage of the retaining wire was seen in either lateral or posteroanterior radiographs, accompanied by backward repositioning of the condylar head compared with previous comparable views. 3. Resorption of the graft. If the condylar head was seen to regress back toward its original position on serial radiographs and there was no change in the position of the retaining wire, it was assumed that the graft was resorbed. 4. Remodeling of the condyle, articular fossa, and eminence was recorded from comparison of the tracings of serial tomograms. These radiographs provided adequate records for observance of gross changes in form but were not suitable for accurate measurement.

410

Banks

A.C.

Q

llyr

D.W.

Q

Immediate

12yr

CA.

d

12~

post - op

D.C. Q

13yr

6 months

D.P.

d

14yr

post-op

Y’’ / :I ._,’ Fig. 3. Cephalometric tracings of the lower incisor region in five consecutive patients in whom the mandibular advancement produced by bilateral postcondylar grafts resulted in a lateral open bite. In each case the lateral open bite closed spontaneously, but in four of the cases (Patients A. C., C. A., D. C., D. P.), this was achieved mainly by an increase in the overbite.

HF PreopAug81 -------- Imm post op

HF _------- Aug 81 May 83

Fig. 4. A, Preoperative and immediately postoperative lateral cephalometric tracings of male patient 15 years 11 months of age. Bilateral lyophilized postcondylar cartilage grafts were carried out in July, 1981, with 1 O-mm advancement. The two positions of pogonion relative to a perpendicular from the line sella-nasion are shown as Pg’ (preoperative) and Pg” (postoperative). the point condylion (Co) is somewhat arbitrary because of difficulty in identification, but both this point and the gonial arc (GA) were traced only on the preoperative radiograph and transferred to superimposed later films. B, Lateral cephalometric tracings of the same patient taken immediately after operation and 21 months later. The point condylion (Co) and the gonial arc (GA) have been transferred from the preoperative tracing. The positions of pogonion relative to a perpendicular from the line sella-nasion are marked as Pg” and Pg”‘. Partial displacement of both postcondylar grafts could be demonstrated on temporomandibular joint radiographs. The cephalometric tracings confirm the relapse of the condylar head but there has not been an equivalent relapse of the chin point and gonion, indicating that compensatory mandibular growth has taken place at the condylar neck.

5. Calcification of the graft was assumed to have occurred when radiopacity was observed. The first appearance of radiopacity was recorded as early calcification. Complete calcification of the graft was

assumed when the radiopacity was comparable with

surrounding bone. If there was no observable change in the position of the condylar head in relation to the external auditory

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Fig. 5. A and 8, Right and left temporomandibular joint tomograms taken on March 23, 1981, showing wire loop fixation of the postcondylar cartilage grafts. C and D, Right and left temporomandibular joint tomograms on Sept. 13, 1983. The wire on the right side has broken with displacement of the cartilage graft. The calcified outline of the graft can be seen. On the left side the cartilage has become laterally displaced with similar relapse of the condylar position. Again, the calcified outline of the graft can be seen, demonstrating its dimensional stability.

meatus and articular eminence in serial radiogra.phs, the operation was termed stable at the rearranged temporomandibular joint. RESULTS Stability of the postcondylar

graft

Radiographic analysis of the graft position was adequate to categorize the patients into two groups: (1) twenty-one patients in whom the graft position was stable and (2) nine patients in whom the coc.dyle relapsed partially or completely back to its original position (Table I). Analysis of these superficially disappointing results revealed the predominant cause of relapse to be postoperative displacement of the cartilage graft :resulting from failure in operative technique (Table II). This occurred in six patients, with lateral displacement present

Table I. Postoperative position of condyles (mean

follow-up 38 months) Total relapse Partial relapse No observable

change

6 3 21

in five cases and inferior displacement in one. Displacement usually took place during the first month after release of fixation, but two of the grafts in different patients displaced at 4 months, and one displaced between examinations at 7 and 12 months when the retaining wire supporting the cartilage graft was found to have fractured. A change in position of supporting wires in posteroanterior and occipitomental radiographs is diagnostic of displacement. Tomograms show retroposition of the condyle with overlap of the fixation wires (Fig. 5).

412

Banks Table II. Causes of relapse of condylar position Total relapse-6

patients

Bilateral displacement of cartilage Resorption of graft Excessive superior remodeling of condyle Partial

relapse-3

3 2 1

patients

Unilateral displacement of cartilage Bilateral partial displacement of cartilage

2 I

Analysis of the forward position of pogonion in relation to sella was recorded in the 2 1 patients in whom the postcondylar graft was stable. The measurements recorded are preoperative, immediately after release of intermaxillary fixation (7 to 10 days postoperatively), and after the latest examination (mean follow-up of 38 months). A similar analysis was made of the 9 patients in whom displacement or resorption of the graft was observed. The results are shown in Table III. Since a steep articular eminence appeared to be unfavorable with regard to graft stability and a steep eminence was often associated with a high mandibular plane angle, a further analysis of the mandibular plane angle in the cartilage displacement group was carried out and compared with the stable group as follows: Fig. 6. Operative photograph of one of two cases in which resorption of a lyophilized graft was observed. In this case the joint area was reexplored, and the photograph shows the right postcondylar space. A small remnant of the original cartilage (C) can be seen. The retaining wire (arrow) now lies free within the tissues, having originally passed through the cartilage graft. The small stainless steel washer above the root of the zygomatic arch can be seen.

Resorption of the graft occurred in 2 patients out of 30 (Fig. 6). Both of these patients had received lyophilized cartilage grafts from the same small batch that, coincidently, was also employed in the two patients with postoperative infection of the graft bed. This batch of cartilage was discarded after the second infection occurred, in spite of being found sterile after culture of several samples. In one subject only, excessive remodeling of the superior surface of the condyle on both sides allowed total relapse of the chin point to take place, in spite of stability of the cartilage grafts (Fig. 7). STABILITY OF THE MANDIBLE Although the median age at operation was 15.3 years, this included four patients operated on between 11 and 12 years of age. There was, therefore, considerable variation in the further growth of different patients within the series.

Cartilage graft displacement 33.44” t 7.00” Stable group (n = 21)-mean 2.13557; P -c 0.05

group 27.79”

(n = 9)-mean T 6.33”;

t =

In many patients forward posturing of the mandible produced a lateral open bite on each side. If the lateral open bite was allowed to close spontaneously, it often did so at the expense of the interincisal relationship, with an increase in the incisor overbite and subsequent proclination of the upper labial segment; the overjet increased and it appeared that relapse was occurring.’ This state of affairs worsened when further vertical or forward growth of the midface took place-an important reason for not operating too early as illustrated in the following case report. CASE REPORT (AC)

One case (Fig. 8) was unique to the series and not included in the overall analysis. A postcondylar cartilage graft was performed in 1978 on an 1 I-year-old patient with a iO-

mm mandibular advance. Measurement of overjet over the next 4 years appeared to demonstrate relapse, but the cephalometric analysis showed this to be entirely the result of further vertical maxillary growth and upper incisor proclination. At 16 years the postcondylar space on each side was reexplored, allowing inspection of the original grafts. Complete incorporation into the skeleton had taken place and the calcified retrocondylar block was identical in size to the original graft (Fig. 8, F). A further autogenous cartilage graft

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Fig. 7. A and B, Right and left temporomandibular joint tomograms taken on Oct. 15,198l. Postcondylar cartilage grafts were inserted 3 months previously and are radiolucent. The retaining wire loops can be seen, indicating the position of the grafts. C and D, Same views on March 9, 1983. This was an isolated case in which excessive remodeling of the top of the condylar head occurred on both sides, causing enough posterior collapse to allow the chin point to regress. An anterior open bite did not develop. In these views calcification c4 both grafts is fairly advanced.

was inserted; thus, in two operations a 20-mm forward repositioning of the condyle was produced. This proved to bc overambitious, and 3 months after the second operation the patient developed pain and trismus. The second gr.aftswere removed and a routine sagittal split was carried out with no subsequent problems. Histologic examination of the grafts that had been removed revealed apparently normal cartilage with a vital cellular element.

It was apparent that 11 years is too young for a predictable surgical result, although growth in some of the younger patients, such as that illustrated in Fig. 1, was favorable and the eventual result was satisfactory. The above case was important in the development of the operation because it appeared to establish a limit of tolerance to forward repositioning of the joint. This was the only patient who developed joint dysfunct:lon. The case also demonstrated that the observed radiopacity of the graft area seen on serial radiographs was true ossification and incorporation into the skeleton.

TEMPOROMANDIBULAR

JOINT CHANGES

In 21 casesthe postcondylar cartilage graft remained dimensionally stable, with no change in the mandibular position (Table III). In this group the long-term changes in the articulation were analyzed from serial tomograms (Table IV). The group comprised 41 grafts; one adult received a unilateral graft to correct a slight asymmetry. The following changes occurred: Condykizr changes. Remodeling of the condyle was noted in 29 grafted joints. In 26 of these, the remodeling occurred on the back of the condyle and in 3 remodeling occurred anteriorly. (Superior surface remodeling to an extreme degree was noted in 1 case previously recorded in the relapse group.) Posterior remodeling presented as scalloping of the condylar outline within the first 3 months and frequently the condylar shape reverted to its preoperative outline after approximately 1 year (Fig. 9). Posterior remodeling was insufficient to cause significant retroposition of the mandible.

414

Banks

AC -----. AC

-

Pre op Jan

-.----

Imm

post

79

-

Post

op

July

82

Jan

79

op

Fig. 8. A, Pre- and postoperative lateral cephalometric tracings of case referred to in text. The patient was 11 years old at the time of surgery. Co = condylion, GA = gonial arc. B, Lateral cephalometric tracings taken immediately postoperative and 3 years later. The preoperative position of condylion (Co) and the preoperative gonial arc (GA) have been superimposed on the tracing. Continued downward and forward growth of the midface has taken the upper labial segment out of control of the lower lip with resulting unacceptable increase in the overjet. Some overall mandibular growth has taken place, but the condylar advancement has been maintained by the postcondylar graft.

Fig. 8 (Cont’d). C, Right temporomandibular joint tomogram taken 17 months postoperatively. The postcondylar graft is outlined by peripheral calcification. D, Same joint 2 years later, just before reexploration of both sides and insertion of additional grafts. The original graft appears to be fully incorporated into the skeleton.

Changes in the articular eminence. In 29 joints change in the angulation of the articular eminence was recorded. The changes were minimal, the eminence appearing to be slightly flattened anteroposteriorly. Remodeling was evidently complete by 12 to 18 months after surgical intervention (Fig. 9). Changes in the cartilage graft. Progressive calcification of the graft was consistently observed. This was evident radiographically as early as 6 months after the surgical procedure but usually took place between 12 and 30 months postoperatively (Figs. 5, 7, 8, and 9). Within the follow-up period, 23 of the grafts showed evidence of calcification, This process started at the periphery when an outline of the cartilage appeared radiographically and, in most cases, seemed to be complete after 2 years. In all patients, apart from the two mentioned previously in whom the graft resorbed, there appeared to be little or no change in the dimension of the cartilage block. The appearance of calcification at the periphery of the block allowed comparison between serial tomograms. After 18 months to 2 years, the graft was found to be fully calcified and incorporated into the retrocondylar skeleton. Displacement can occur theoretically until such time as the graft is skeletally incorporated and was observed on one occasion in this series to take place between the 7 and 12 months’ postoperative examinations. There appeared to be no difference in behavior between autogenous and lyophilized bank grafts.

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Fig. 8 (Cont’d). E, Left postcondylar region at operation 1 day after tomogram shown in D. The original graft has been replaced by bone. F, Another view of the same side to demonstrate that the dimension of the retrocondylar block of bone is identical to the dimension of the original cartilage graft. G, Same patient. A second autogenous cartilage graft was inserted at the second operation. This had to be removed 3 months later because of severe mandibular joint dysfunction. This is a photomicrograph of the graft showing it to have the appearance of normal vital hyaline cartilage.

Fixation of the graft (Table V)

Spontaneous displacement of the cartilage graft was observed in a few of the early cases.’ At that time Trauner’s original method of retention was in use. That method involved a stainless steel washer below the block linked by a wire through the cartilage to 2.similar washer above the posterior part of the zygomalic arch. It was difficult to hold the cartilage medially with this technique, and in most subsequent cases the cartilage

block was contained within a loop of wire.3 This me:thod did not stand the test of time and was abandone:d in 1982. The method of fixation employed since JamJary, 1983, and applied to the last 10 patients in the total series of 37 made use of a 2- or 3-mm Kirschner wire drilled down into the cartilage from above the zYPmatic arch after the graft had been fixed by Traulner’s original technique. The cartilage was pushed med lially

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Fig. 9. Serial temporomandibular joint tomograms covering a 3-year period after bilateral lyophilized postcondylar cartilage grafts. A, Immediately after operation showing retaining wires (Trauner technique). B, Tomogram taken 3 months later, showing typical posterior condylar remodeling.

Table III. Analysis of the forward position of Pogonion in relation to sella

Stable group (21 patients) Relapse group (9 patients)

Preoperative

Postoperative

53.5 t 5.0

62.62 2 5.2

45.6 f 9.38

52.8 2 10.9

Net advance

Last recorded (mean 38 months) postoperative

+9.15 2 2.33

63.6 2 5.0

+7.17 2 2.88

47.2 k 11.3

Net postsurgical change

+1.05 2 1.94 -5.5

t 2.28

Mean distance in mm ( f SD) from S point to the intersection of SN with perpendicular to pogonion. The two preoperative groups cannot be regarded as coming from the same population: the means are significantly different (t = 3.024, P < 0.01) and the variances differ significantly (F = 3.519, P < 0.05). The net advance is significantly different (t = 2.089, P < 0.05) and the difference in net postsurgical change is highly significant (t = 8.047, P < 0.001).

as the Kirschner wire was inserted, and the rigid wire prevented subsequent lateral displacement of the cartilage (Fig. 10). To date, all the grafts thus secured have remained completely stable. -Two of the 2-mm diameter Kirschner wires subsequently moved upward toward the skin surface, threatened to extrude, and had to be removed. None of the thicker 3-mm wires has shown any tendency to migrate in this way. In 198 1 the available cartilage from cadaver sources was consistently small and of poor quality. Eight postcondylar grafts during this period were constructed as a sandwich formed of two pieces either wired to-

gether or glued with cyanoacrylate cement. Five of the grafts so formed either displaced or became infected, and the method was abandoned. TEMPOROMANMBULAR

JOtNT FUNCTION

Within the limits of mandibular advancement achieved by this technique (maximum, 14 mm), no long-term disturbance of mandibular function was observed. There was limitation of opening and little or no lateral movement of the jaw up to 3 months after surgery. Between 3 and 6 months protrusive and lateral movements became reestablished. In all cases followed

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Fig. 9 (Cont’d). C, Twenty months after surgery. The condyles are now of normal shape. The cartilage grafts are calcified and appear incorporated into the bone of the postcondylar region. D, Views taken 1 year later with the mouth open. The minimal remodeling of the articular eminence and its relationship to the repositioned condyle in the ape? position are demonstrated. IV. Long-term changes in articulation analyzed from serial tomography

Table

Stable group-21

patients

(1 unilateral)

41 grafts Lyophilized Autogenous Remodeling of condyle Remodeling of articular eminence Calcification of graft

Table

V. Fixation of graft-37

Trauner method wi loop Sandwich-wired Sandwich-cyano-acrylate glue Kirschner wire

21 14 29 20 23

patients (73 grafts) 13 (6 displaced) 32 (7 displaced) (4 resorbed) 3 (2 disp1ace.i) 5 (3 infected, 20 (none displaced)

for more than 1 year, mandibular excursion was recorded to be within normal limits-that is, unrestricted and pain free. In those cases in which graft displacement cccurred, patients were sometimes aware of a lateral bulge and narrowing of the external auditory meatus was noted.

Fig. 10. Diagrammatic representation of retention of a postcondylar graft using a soft-wire loop tied over a square washer above the zygomatic arch. Lateral displacement is prevented by drilling a rigid 3-mm Kirschner wire down from above into the cartilage graft after it has been wired into place as described above.

Sometimes the patient was aware of crepitation on opening, but in no case has it been necessary to remove the displaced cartilage (other than the two cases in which the graft had become infected and the case reported above). DISCUSSION

Although the technique for advancing the retrognathic mandible by means of a postcondylar graft was

Fig. 11. A, Operative photograph of left condylar space 8 months after insertion of a lyophilized postcondylar cartilage graft (case referred to in text). The graft (C) shows no evidence of resorption. 8, Same view after freeing the graft from its bed just before removal. The original costal cartilage shape in cross section has been maintained. C, Photomicrograph of graft after removal. The cartilage contains the shrunken nuclei of dead chondrocytes. Areas of early calcification are clearly visible.

described by Trauner in 1954,’ there have been no previous attempts to evaluate the technique over a reasonable period of time. The operation involves a deliberate distortion of the temporomandibular joint and alters the line of action of all the muscles of mastication. Furthermore, it cannot be used to achieve definitive correction of the occlusion, and a bilateral open bite is frequently observed in the immediate postoperative period. At the outset of the series, it was hoped that the

operation would take the place of orthodontic therapy in the selected cases. McNamara’O reported favorable adaptation of neuromuscular function following forward posturing of the mandible in rhesus monkeys with myofunctional appliances. He also reviewed the literature and confirmed by his own studies that mandibular adaptation would occur which, in young monkeys, was primarily skeletal, whereas compensatory movement of teeth became more significant with increased maturation. The experimental studies on functional reposi-

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tioning of the mandible all suggest that the histologic structure of the temporomandibular joint is stable and resistant to changes in function.“. ‘I It was, therefore, hoped that a dimensionally stable, biologically compatible postcondylar graft used to posture and support the mandible in a forward position would be followed by muscle realignment and dentoalveolar compensation if carried out during adolescence. This appears to have occurred in all cases in which the graft itself remained stable. However, during the course of the study it soon became apparent that orthodontic supervision both pre- and postoperatively was necessary, although any appliances required were of the simple, removable kind used mainly for postoperative control of the interincisal relationship.*. 3 The use of simple, removable appliances postoperatively has enabled controlled closure of any lateral open bite to be achieved satisfactorily in all the later cases. Cartilage as a graft material is remarkably resistant to remodeling,” and no difference was obse::ved between lyophilized bank cartilage and autografts. It was notedI that lyophilized cartilage placed subperiosteally will retain its shape and consistently ossify slowly, the process being complete within 18 months. Ossification does not occur if the cartilage is placed supraperiosteally. I3 The technique used for postcondylar grafts involves detachment of the posterior part of the joint capsule by subperiosteal dissection in the glenoid fossa and down the front of the bony external auditory meatus. The cartilage graft is placed subperiosteally and the whole joint is displaced forward. There is no surgical encroachment on the joint cavity, and the relationship of the meniscus to the capsule and condylar head is thought to be maintained. Dimensional stability of the cartilage graft was consistently observed in this series. The graft was shown to calcify from the periphery and eventually became ossified and incorporated into the retrocondylar skeleton (Fig. 8, E and F). The quality of the graft material seems to be important. During 1981 a batch of cartilage from an older cadaver was (coincidently or otherwise) associated with a series of complications. Resorption of the lyophilized grafts occurred in two patients, one of whom has recently been subjected to furtner operative correction ( Fig. 6). In two other patients, postoperative infection supervened at this time. In one of these, the infection was unilateral and the other graft remained undisturbed for 8 months. The patient was readmitted for a sag&al split advance, at which stage the remaining cartilage graft was removed. It was found to be perfectly positioned and dimensionally unchanged (Fig. 11). Direct inspec-

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tion of grafts at reoperation is rarely possible but has provided valuable information on the few occasions when it could be accomplished. It was demonstrated in this series of patients that a healthy cartilage graft placed behind the condyle will remain dimensionally stable and eventually become incorporated into the retrocondylar skeleton. The condyle and fossa undergo relatively minor remodeling, and a normally functioning new joint becomes established in a more forward position. In only one subject was the condyle remodeled to the extent that observable relapse of the mandibular position occurred (Fig. 7). If the operation is carried out at the most favorable age-that is, after the pubertal growth spurt-changes in the mandible are mainly limited to dentoalveolar compensation. This article is primarily concerned with observation of the temporomandibular joint changes, and the cephalometric analysis was confined to measuring the anteroposterior position of the chin point in relation to the sella-nasion line. When the postcondylar graft remained in position, as in the stable group, the position of pogonion remained stable. When the cartilage became displaced or resorbed, it was not surprising that the chin point relapsed (Table III). Although the numbers were small, it was surprising to find that the mean measurement used to assess the forward position of pogonion relative to the cranial base differed significantly in the graft-stable group and graft-displacement group. This suggests that a particular facial morphology may predispose to graft displacement. It was noted in 1 subject that the condyle rode back above the cartilage block which, in effect, became displaced inferiorly. This was the patient with the highest mandibular plane angle in the series with an associated steep posterior incline on the articular eminence. Analysis of the mandibular plane angle to sella-nasion suggested that a high mandibular plane angle might predispose to graft displacement and relapse. The sample size is small, however. There is some evidence from this series to suggest that, when partial displacement of one or both cartilage blocks has occurred, compensatory lengthening of the mandible can take place at the condylar process with maintenance of the occlusion and the position of the chin (Fig. 4). It was impossible to produce a statistically valid cephalometric appraisal while the surgical technique was subject to modification. It now appears that lyophilized cartilage can be reliably employed as a graft material and that the method of surgical fixation is dependable. A continuing analysis of cases operated on since January, 1983, with Kirschner-wire fixation of

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the graft will form the subject of a further article after an adequate follow-up period. The operative morbidity following a postcondylar cartilage graft is minimal. It is preferable to have 7 to 10 days of intermaxillary fixation, as this eliminates virtually all the postoperative discomfort. It was found that many of the patients were prepared to accept a postcondylar graft, whereas they and their parents had considerable reservations about a sagittal split procedure. Nevertheless, it is clear that the overall percentage of relapse is too high for the operation to be acceptable without further justification. Relapse occurred predominantly because of displacement of the cartilage graft, usually in a lateral direction. Displacement of the cartilage may occur the first few days after surgery, but unless the skeletal internal fixation is secure, it may also displace up to 12 months after surgery. The graft’s position is delineated by the retaining wire and any lateral displacement is detectable from posteroanterior and occipitomental radiographs. On three occasions the retaining wire broke between 4 and 12 months after surgery, allowing late displacement of the graft in 2 patients. Initially the grafts were retained by the method described by Trauner in 1954, but it was found that nearly half of these shifted laterally with relapse. A modification of the technique3 has not stood the test of time, with displacement occurring in 7 of 32 grafts (Table V). In 1983 the method of fixation utilizing a Kirschner wire to resist lateral movement was introduced and has to date prevented any relapse caused by graft displacement. It is important to ensure that the cartilage employed is large enough to be cut down to an exact size; attempts to fix two smaller pieces together have all failed. CONCLUSION

After 6 years’ continuous follow-up of cases of retrognathia treated by postcondylar cartilage graft, some conclusions can be reached. The low morbidity of the operation and the stability of the successful cases are encouraging. Long-term function of the temporomandibular joint is unaffected, with full recovery of protrusion and lateral excursion. As a result of minimal remodeling of the condyle and fossa, the articulation re-forms in a more anterior position, with the cartilage graft incorporated into the retrocondylar skeleton. The surgical technique is applicable to selected cases with Class II, Division 1 occlusal relationships requiring a mandibular advance of up to 12 mm. Ideally, it should be carried out at 14 to 15 years of age and not earlier. Good-quality lyophilized bank cartilage ap-

pears to have no disadvantages as compared with autografts. Adequate fixation of the graft is essential, or displacement and relapse will take place. The methods of fixation originally employed in this series have proved unreliable, but the modified technique applied to the last 10 cases has not yet failed; however, longer-term evaluation of these cases is required. Finally, it must be reemphasized that close liason with the orthodontist is essential for both presurgical selection and preparation and postoperative control. The author would like to acknowledge the assistancereceived in the preparation of this article from the Department of Photography and Medical Illustrations at the Queen Victoria Hospital, East Grinstead, Sussex, England. and, in particular, Mr. Trevor Hill and Mrs. Eileen Pope. He would also like to acknowledge the cooperation and advice of his consultant orthodontic colleagues, Mr. A. R. Thorn and Mr. D. G. Ardouin. Statistical data were prepared by Dr. W. Harvey, Ph.D., senior biochemist at the Eastman Dental Hospital, London. REFERENCES 1. Trauner R: Die retrokondylare Implantation; eine Operationsmethode zum Vorbringen des Unterkiefers beim Distalbik. Deutsche Zahn-, Mund- und Keiferheilkd mit Zentralblatt fiir die Gesamte Zahn-, Mund- und Keiferheilkd 20: 391, 1954. 2. Banks P, Ardouin DG: The post-condylar cartilage graft in the treatment of distocclusion-a preliminary report. Br .I Oral Sug 18: 17-33, 1980. 3. Brown AE, Banks P: The post-condylar cartilage graft in the treatment of retrognathia-an assessmentof stability and function. Int J Oral Surg Supp 1: 286-291, 1981. 4. Lenatt V: Reflexions sur le traitement operatoire des retrognathies. Rev Stomatol Chir Maxillofac 69: 608, 1968. 5. Poswillo DE: The aetiology and surgery of cleft palate with micrognathia. Ann R Co11Surg Engl 43: 61, 1968. 6. Lachard J, Vitton J: Traitement des retrognathies mandibulaircs par greffe cartilageneuse retrocondylienne. Ann Chir Plast Esthet 18: 50, 1973. 7. Vitton J, Gola R, Blanc JL, Lachard J: L’operation de Trauner. Rev Stomatol Chir Maxillofac 74: 633, 1973. 8. Kohn MW: Analysis of relapse after mandibular advancement surgery. J Oral Surg 36: 676-684, 1978. 9. Lake L, McNeil1 RW, Little RM, West RA: Surgical mandibular advancement: a cephalometric analysis of treatment response. AM J ORTHOD 80: 376-394, 1981. 10. McNamara JA: Neuromuscular and skeletal adaptations to altered function in the orofacial region. AM J ORTHOD 64: 578-606, 1973.

11. Hiniker JJ, Ramfjord SP: Anterior displacement of the mandible in adult rhesus monkeys. J Prosthet Dent 16: 503-512, 1966. 12. Sailer HF: Experiences with the use of lyophilized bank cartilage for facial contour correction. J Maxillofac Surg 4: 149, 1976. 13. Sailer HF: Personal communication, 1984. Reprint

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Dr. P. Banks Queen Victoria Hospital East Brinstead Sussex, England