Temporomandibular joint condylar prosthesis: A ten-year report

CLINICAL J Oral Maxillofac 41:245-254

UPDATE

Surg

1983

Temporomandibular Joint Condylar Prosthesis: A Ten-year Report JOHN N. KENT, DDS,* DALE J. MISIEK, DMD,t RICHARD K. AKIN, DDS,* EDWARD C. HINDS, DDS, MD,5 AND CHARLES A. HOMSY, ScD” conium surgical alloy with a standard-shaped head, neck, and shank, and was 45, 50, or 55 mm long. The shank was flat and had a 1 mm Proplast I (PTFE-carbon fiber) coating on both medial and lateral surfaces (Fig. 1). Three to four weeks of maxillomandibular fixation was necessary. In 1975, Kent modified the prosthesis to produce a box shank (TMCK). This design had parallel flanges, which fit into grooves cut into the lateral aspect of the mandibular ramus. It improved stabilization and made immediate postoperative function of the mandible possible (Fig. 2). Both flat and box shank prostheses were cast from a chrome/cobalt/ molybdenum alloy and were available in 40 and 47 mm lengths, with a smaller articulating head. Three or four self-tapping screws, cast from the same alloy, were used to secure the prosthesis to the ramus. A metal template (Fig. 3) was used to prepare the flange grooves and screw holes prior to insertion. More recently, white Proplast II (PTFEaluminum oxide) has been used as the coating for the TMCK prosthesis.

In 1972, we reported the use of a metallic temporomandibular joint (TMJ) condylar prosthesis, the shank of which was covered with a biocompatible interface substance, Proplast.**1.2 Three cases of temporomandibular joint reconstruction using this prosthesis were originally described, and a follow-up on those cases and an additional six cases was reported in 1974.3 Treatment planning with tomography was subsequently described.4s5 A brief retrospective survey was presented at the First World Biomaterials Conference, Austria, in 1980 and to the American Association of Oral and Maxillofacial Surgeons, Washington, in 198 1.6.7 During the past ten years, more than 500 of these prostheses have been placed by oral and maxillofacial surgeons throughout the United States. It is the purpose of this paper to provide a clinical update on the use of the metallic condylar implant including long-term follow-up statistics on over 100 cases in which it was used for condylar head replacement in temporomandibular joint reconstruction. Description

of the Prosthesis

Indications for and Placement of Prosthesis

The first condylar prosthesis (TMC), available from 1971 to 1975, was individually cast from Ti-

The Proplast-coated metallic prosthesis is indicated only when the condyle has been rendered nonfunctional; is severely diseased, damaged, or lost because of trauma; or was excised in a previous surgical procedure. It has been used in the following conditions: bony or fibrous ankylosis; severe degenerative, rheumatoid, traumatic, infectious, or metabolic arthritis; congenital absence of the condyle in adults; loss of the condyle in acquired deformities due to neoplasm, infection, or trauma; or malocclusion with facial deformity, such as open bite, retrognathism, or asymmetry secondary to any of the preceding conditions. Contraindications to the use of a Proplast-coated metallic prosthesis include limited capacity of the patient for postoperative cooperation, systemic disease contraindicating the use of any alloplastic ma-

* Professor and Head of Oral and Maxillofacial Surgery, Louisiana State University School of Dentistry; Chief of Oral and Maxillofacial Surgery, Charity Hospital, New Orleans. t Formerly chief resident at Charity Hospital; now in private practice in New Orleans. $ Clinical Associate Professor of Oral and Maxillofacial Surgery, Louisiana State University School of Dentistry and Ochsner Foundation Hospital, New Orleans. 5 Professor and Head, Department of Surgery, University of Texas School of Dentistry. ” Director, Prosthesis Research Laboratory, Fondren Orthopedic Center, The Methodist Hospital, Houston; Research Associate Professor, Division of Orthopedic Surgery, Baylor College of Medicine. Address correspondence and reprint requests to Dr. Kent: Department of Oral and Maxillofacial Surgery, School of Dentistry, Louisiana State University, 1100 Florida Avenue. New Orleans, LA 70119. ** Proplas@ implant biomaterial, Vitek, Inc., 3143 Yellowstone Rd., Houston, TX 77054.

245

246

CLINICAL

UPDATE

FIGURE I. Left. Prc bplast I coated metallic con dylar prosthesis with flat s (TMC type). ProFIGURE 2. Right. plast I coated metallic : condylar prosthesis with box shank (TMCK type).

terial, inadequate ramus height for implant tit and stallilization, and growth that is still taking place. Surgical

Techniques

The surgical procedure for placement of the Proplast-coated metallic prosthesis involves gaining access to the ramus and condyle through a retromandibular/submandibular approach. The deformed condyle or ankylosed area is exposed and excised with air-driven oscillating saws to provide a 1 cm space for placement of the condylar prosthesis. Occasionally, preauricular exposure of the TMJ is necessary. In patients with hypomobility, a coronoidectomy is usually done to facilitate postoperative function and allow rotation or advance-

ment of the mandible for correction of open bite or retrognathia. In addition, the use of a large orthopedic bone hook and suprahyoid myotomy may be necessary to advance the mandible and correct the open bite deformity frequently seen in patients with severe ankylosis. In bony ankylosis. preparation of a very shallow articular fossa, but not to the original fossa depth, is performed with large burs. After a predetermined occlusion has been established, maxillomandibular wire fixation is applied (a wafer splint is helpful), and the lateral surface of the ramus is prepared with the use of the metal template (Fig. 3). Parallel grooves, 2 mm deep, are prepared on the lateral surface to provide seating of the flanges of the box (TMCK) type prosthesis. Screw holes are prepared with a No. 703 bur, the diameter

FIGURE 3. Lefr, Metal template used to prepare both screw holes for the condylar prosthesis and flange grooves for the box shank. FIGURE 4. Right. Preparation of lateral surface for box shank condylar prosthesis, showing screw holes, parallel grooves, and decorticated area to improve lit of prosthesis.

KENT ET AL

247

FIGURE 5. Proplast-coated 47 mm TMCK condylar prosthesis, secured with four self-tapping screws.

of which is no larger than the inside diameter of the screws. Occasionally, lateral decortication is necessary to improve the tit of the prosthesis (Fig. 4). Three or four self-tapping screws, 8 or 11 mm, are placed to secure the prosthesis (Fig. 5). Occasionally, a nut has been placed engaging the second screw on the lingual aspect of the ramus for added stabilization (Fig. 6). Three to four weeks of immobilization for the flat (TMC) condyle is recommended, followed by gradually more vigorous opening exercises. The box (TMCK) condyle, with two parallel flanges recessed in the lateral ramus,

provides additional stabilization, thus permitting immediate postoperative mobilization. Materials

and Methods

In January 1980, a retrospective survey by Misiek and Kent was undertaken to evaluate the following parameters: preoperative TMJ findings (demographic information, dentofacial profile, TMJ symptoms, contributing diagnosis, previous surgical therapy, radiographic findings, and jaw excursions), surgical findings, current surgical therapy, postoperative findings (vertical dimension maintenance, incisal opening, and lateral excursions), and Proplast metallic condyle type and technique. A comprehensive, four-page survey questionnaire dealing with each of those categories was sent to private practitioners and oral and maxillofacial surgery residency programs using the condylar prosthesis. The survey also allowed the reporting of other treatment modalities such as silicone rubber block for interpositional arthroplasty. Because of the nonparametric nature of the data reported, statistical analyses were found to be inappropriate. Rather, with the volume of response and length of follow-up involved in the cases reported, presentation of data in raw form more adequately reflected the clinical performance of the Proplastcoated metallic condylar prosthesis. Results

FIGURE 6. Left. Posteroanterior radiograph showing a nut to improve stabilization of 40 mm TMCK prosthesis. Righr, Fiveyear posteroanterior radiograph showing satisfactory position of 47 mm TMCK condylar prosthesis with four self-tapping screws.

PREOPERATIVE

A total of 109 prostheses placed in 80 patients was reported. Sixty per cent of those patients repre-

CLINICAL

248 Table 1.

Demographic

Males Females Average age (yr) Age range (yr) Number of condyles Average follow-up (mo) Follow-up range (mo)

Table 2.

Dentofacial

Information

Ankylosis

Rheumatoid Arthritis

Osteoarthritis

15 42

0 7

1

I

7

7

33.2

43.9

37.4

35.1

15-56

23-60

30-52

15-48

Miscellaneous

76

12

12

9

25.8

20.8

27

25.9

l-120

10-42

4-84

6-72

Profile* Ankylosis

Rheumatoid Arthritis (%)

Class I Class II Class III

39 32 1

(54.2) (44.4) (1.4)

5 7 0

(41.7) (58.3) (0)

9 3 0

(75) (25) (0)

Total

72

(100)

12

(100)

12

6 3

(8.3) (4.2)

0 0

(0) (0)

59 4

(81.9) (5.6)

10 2

72

(loo)

12

height No deformity Total

NO.

(8)

Miscellaneous

Osteoarthritis

No.

Asymmetry Crossbite Decreased ramus

UPDATE

NO.

1%)

NO.

( %I

5 3

(62.5) (37.5) __(0)

(100)

8

(100)

0 0

(0) (0)

2 3

(25) (37.5)

(83.3) (16.7)

2 10

(16.7) (83.3)

2

1

(25) (12.5)

(100)

12

(100)

8

(100)

2

* Reported for 104 of 109 condyles placed (95.4%).

sented the efforts of 20 private practitioners and teaching institutions, whereas the remaining 40% were treated by these authors at the Louisiana State University Medical Center at New Orleans and the University of Texas Health Sciences Center at Houston. Demographic information (Table 1) shows that females outnumbered males by 3: 1 or more in each of four major diagnostic categories. The average ages were 33.2 and 43.9 years for patients with ankylosis and rheumatoid arthritis, respectively, and the ages individually ranged from 15 to 60 years. Ankylosis was the predominant diagnosis for which the metallic condyle was placed. Follow-up for all cases averaged 25.4 months; individually, the range was from one to 120 months. The preoperative dentofacial profile was reported for 95.4% (104 of 109) of condyles placed (Table 2). Each condyle and corresponding hemimandible was considered as a single entity to avoid confusion between patients requiring bilateral vs unilateral condylar reconstructions. Class II (retrognathic) profiles were found in many cases, with rheumatoid arthritis and ankylosis cases showing significantly

high percentages, 58.3% and 44.4%, respectively. Decreased ramus height, the primary contributing factor in an acquired retrognathic profile, was even more evident, being reported in 81.9% of ankylosis cases and 83.3% of rheumatoid arthritis cases. Although open bite deformities were not reported, it is only logical that open bites would exist in most instances of acquired retrognathia resulting from decreased ramus height. In our own clinical experience, this has been a constant finding. Because ankylosis was the diagnosis in the majority of cases, etiologic factors contributing to this diagnosis were studied (Table 3). Trauma such as mandibular fractures, intracapsular hematomas, and birth injuries, is well known to be a major cause of TMJ ankylosis, and this was borne out by the fact that some history of trauma was reported in 82.5% and 53.8% of the prosthesis successes and failures, respectively. Arthritides, whether post-traumatic, post-infectious, or due to degenerative changes, were also noted to antedate the onset of ankylosis. However, the intervening therapy, operative or nonoperative, may have been more of a factor in these instances.

KENT ET AL

249

Previous surgical therapy is given in Table 4. Of the 34 previous arthroplasty procedures reported, 24 were performed with placement of silicone rubber blocks, and others with thin sheets of Teflon or silicone rubber. A high percentage of these required reoperation because of displacement of the material and loss of ramus vertical height. Previous mandible fractures (Table 4) occurred in 3 1 patients who had subsequently undergone reconstruction with Proplast-coated metallic condyles. Of the 33 fractures treated by closed reduction, 31 were subcondylar fractures, of which 21 had significant condylar displacement. Ankylosis developed in each of these, suggesting that perhaps surgical repositioning of the displaced fractured condyle may have prevented ankylosis. In the miscellaneous category, several diagnoses were listed (Table S), developmental hyperplasia Table 3. Contributing (76 Condyles)

Diagnosis

in Ankylosis

Successful Prostheses (63) %

Failed Prostheses (13) %

82.5

53.8

57.1 27.0

15.4 15.4

1.6

7.7

Table 5. Miscellaneous Diagnoses

Preoperative 3 2 1 1

Developmental hyperpfasia Aseptic necrosis Developmental hypoplasia Osteochondroma Desmopfastic fibroma Trauma

-

1 I 9

Table 6. Preoperative of Condyle*

Radiographic % Occurrence

Decreased interarticufar spat :e Irregular condyfar contour Fibrous ankyfosis Condyfar flattening Bony ankyfosis Condyfar displacement Severe condyle erosion Osteophytes Condyfar fipping Coronoid enlargement Subarticufar radiofucencies

85.3 66.1 48.6 24.8 21.1 19.3 17.4 14.7 13.8 10.1 6.4

Findings (Cases) (93) (72) t53) (271 (23) (21) (191 (16) (15) (11) ( 7)

+ May represent more than one finding per case. History of trauma Post-traumatic arthritis Osteoarthritis Postinfectious arthritis

Table 4.

Prevlous

Surgical Therapy* Occurrence

Arthropfasty with interpositional polymer blocks/sheeting Closed mandibular fractures Condyfectomy Open mandibular fractures Facial fractures (LeFort and trimafar) Coronoidectomy Propfast Teflon laminate implantation Lateral pterygoid myotomy Condylar shave Condylotomy Eminectomy Joint scarification and capsular pfication Closed (Gigfi saw) vertical ramus osteotomy Accidental horizontal ramus osteotomy Meniscectomv

34 33t 25 20t 8 7 6 5 4 4 3 3 2 1 1

* May represent more than one previous surgical procedure per patient. + These numbers reflect both single and multiple fractures occurring per case of condyfar reconstruction. The 53 fractures reported occurred in 31 patients who underwent reconstruction with the Proplast-coated metallic condyle.

being the most frequent. In one patient, complete bilateral aseptic necrosis of the condyle occurred following closed (Gigli saw) vertical subcondylar osteotomies for mandibular prognathism. This resulted in decreased ramus height, retrognathism, and open bite. The common factor in each of the other miscellaneous diagnoses was the necessity for condylectomy followed by TMJ reconstruction. In all of the diagnostic categories, radiographs were necessary to complement the clinical evaluation. More importantly, information regarding the status of the present condyle or its replacement was obtained to determine the plan of reconstruction. Table 6 shows that decreased interarticular space was the most common preoperative radiographic finding. POSTOPERATIVE

Successful results outnumbered failures in each diagnostic category (Table 7) regardless of whether the flat (TMC) or box (TMCK) design was used. However, the success rate clearly improved with the advent of the box design (success rate of 90.5% overall and 94.2% for ankylosis) as opposed to the flat design (success rate of 60% overall and 58.3% for ankylosis). Correct ramus height was established at the outset as one of the prime goals of condylar reconstruction. Maintaining or increasing ramus height

250

FIGURE 7. Panoramic radiograph shows glenoid fossa resorption and displacement of condylar prosthesis into the middle cranial fossa at 24 months in a patient with rheumatoid arthritis.

plays an important role in the success or failure of the reconstructive effort. Table 8 shows that 98.8% of successful cases had maintained or increased ramus height, whereas only 1.2% had decreased height. Failures, however, showed only a 52.7% rate of maintained or increased ramus height, whereas a decrease was seen 47.3% of the time. When only ankylosis was considered (Table 9) and results were classified according to flat and box design reconstruction, ramus height was maintained or increased in 100% of successful flat and 97.6% of successful box condyles, whereas a decrease was noted in only one of the 43 box condyles. Both flat and box condyles showed higher rates of decreased ramus height in cases that failed; however, these represent a small number, three and one, respectively, in relation to the total number of condyles (76) placed for ankylosis. Incisal opening, probably the single most important objective measure of postoperative function, is also depicted in Table 8. Overall, 96.4% of successful cases showed maintained or increased opening, whereas 3.6% showed decreased opening. Failures had a higher rate of decreased opening, 26.4%, and opening was still maintained or increased in the majority, 73.6%, of cases where reankylosis was not a factor in ultimate failure. Table 9 shows similar percentages for ankylosis cases, where increased incisal opening is a primary objective for reconstruction. Though decreased opening was noted in one (7.1%) of the successful flat condyles and two (4.7%) of the successful box condyles, the quantitative decrease was minimal in each case (1 - 3 mm) and represented negligible decreases in preoperative opening of the 20-25 mm range. The 62.5% decrease noted in the flat condyle failure category represented a substantially greater decrease in opening, on the order of lo-20 mm, and was probably related to postoperative immobilization as well as poor cooperation with physiotherapy. Finally, lateral excursions were evaluated. It must be understood that when the condylectomy for condylar reconstruction is done, the lateral

CLINICAL

UPDATE

pterygoid muscle attachment is usually lost. Therefore, maintained or increased excursions will rarely be present, although several patients demonstrated movement of the metallic condylar head onto the articular eminence. Table 8 shows that in successful cases, excursion was maintained in 59.8% and increased in 26.8%, whereas decreased excursions occurred in 13.4% of cases. Failures showed a greater decrease in excursions, 26.4%, which was probably related to corresponding decreases in ramus vertical dimension and incisal opening previously discussed. Once again, Table 9,

FIGURE 8. Total joint reconstruction with Syncar-NomexProplast glenoid fossa and Proplast II-coated TMCK prostheses used to correct TMJ dysfunction with retrognathidopen bite found in patients with rheumatoid arthritis, seronegative arthritides, and idiopathic condylar resorption.

KENT ET AL

Table 7.

Effect of Shank Design Flat (35)

Box (74)

Diagnosis

success

Ankylosis Rheumatoid arthritis Osteoarthritis Miscellaneous

14

10

49

3

0 5 - 2 21

0 2 - 2 14

8 5 5

4 0 0

Total

FailUIe

(60%)

with only ankylosis cases, shows similar percentages, with excursions maintained or increased in successful flat (92.9%) and box (95.3%) condyles, and decreased in 7.1% and 4.7% of the former and latter, respectively. Decreased excursions in 37.5% (three) of flat and 33.3% (one) of box condyle failures are also noted. Because lateral excursions are not expected to be increased by condylar reconstruction alone, the results could relate to the increased freedom and range of motion created by relieving the ankylosis. One might expect this to be true, especially in cases where the contralateral condyle was unaffected; however, no significant difference in percentages occurred when bilateral and unilateral cases were evaluated in separate groups. A most important factor in successful postoperative function is physiotherapy. The sooner the physiotherapy can be started, especially in ankylosis cases, the better. Postoperatively, immobilization (Table 10) was used for an average of 2.9 weeks in 84.2% of successful flat condyles and for an average of 4.5 weeks in 83.3% of failed condyles. The box condyles, specifically designed to obviate the need for postoperative immobilization, had no fixation used in 56.7% of successes. Comparing the flat condyle failures in which immobilization lasted an average of 4.5 weeks, and the box condyle failures, in which no immobilization was used, reankylosis was seen in five of 14 flat condyle failures, a 35.7% occurrence. There were no instances of reankylosis seen with the use of the box condyle, indicating that immobilization may have been a significant factor in reankylosis. Failures have been mentioned throughout this discussion without being individually addressed. Table 11 delineates the reasons for failure in all 21 cases. Reankylosis was seen only with flat design condyles, strongly implicating the effect of postoperative immobilization. Infection was seen with loosening of the prostheses or in patients who had had numerous operations for repeated ankylosis. Infection has decreased over the years because of improved stabilization and familiarity with the han-

Success

(40%)

67

FailWe

(90.5%)

7

(9.5%)

dling of the prosthesis. Inadequate stabilization of prostheses with screws was a surgical error that could have been avoided. In five cases of inadequate screw stabilization, only two screws were used in three patients who had enough bone for three or more. One case failed when both buccal and lingual cortical plates were not engaged, and finally, stabilization of the prosthesis with only two screws occurred in a patient with inadequate bone height. Placement error also represented a technical problem and not a problem with the prosthesis. Metal fatigue, induced by severe bending at surgery, occurred in one case in which the shank fractured during function. Glenoid fossa resorption was seen in bilateral reconstruction of two patients with rheumatoid arthritis who have functioned with the prosthesis for 24 months or longer. Severe glenoid fossa resorption, anterior open bite, limited function, and radiographic evidence of condylar displacement near or into the middle cranial fossa developed in both patients (Fig. 7). In an attempt to solve this problem, custom glenoid fossa implants were made (Fig. 8). The implant is a laminated construction of Proplast (superior layer), Teflon FEP polymer incorporating an embedded polyaramid fabric of Nomex (middle layer), and a hard fused Teflon TFE (Syncar) polymer reinforced with graphite fiber for condylar articulation (inferior layer). Varying thicknesses and shapes of the glenoid fossa implant may be custom designed from cephalometric views, lateral AP tomograms, and basilar views of the TMJ.* The implant can be easily modified intraoperatively for adaptation to the glenoid fossa, articular eminence and zygomatic arch.? Discussion

The Proplast-coated duced very satisfactory

metallic condyle has proresults in rehabilitation of

* Available from Vitek, Inc., Houston, Texas t Kent JN, Block MS, Homsy CA: A new glenoid fossa prosthesis (unpublished data)

CLINICAL

252 Table 8.

Postoperative

Findings: All Cases (100 Condyles

Reported)

Successes”

Height

Failures? INO.

R

(NO.)

m,

59.8 39.0 1.2

(48) (32) (1 )

31.6 21.1 47.3

(6) (4) (9)

100

(81)

100

(19)

36.6 59.8 3.6

(30) (48) (3 )

36.8 36.8 26.4

(7) (7) (5)

100

(81)

100

(19)

59.8 26.8 13.4

(48) (22) (11)

57.8 15.8 26.4

(11) ( 3) ( 5)

100

(81)

100

(19)

of ramus

Maintained Increased Decreased Total Incisal

UPDATE

opening

Maintained Increased Decreased Total Lateral exciirsions Maintained Increased Decreased Total * Reported in 81 of 88 cases (92.1%). t Reported in 19 of 21 cases (90.5%).

adult patients suffering from ankylosis, severe arthritides, and unusual aberrations of the temporomandibular joint. Its use, however, should be restricted to adult patients, and in this study no one under the age of 15 years underwent condylar reconstruction in this manner. The reasons for this are twofold: first, in a child or young adolescent, who has not reached full growth potential, the anatomy of the ramus and temporomandibular articulation will not accommodate the Proplast-coated metal condyle; second, a biologic material, such as a costochondral composite graft,s has a greater propensity to respond to the dynamic changes present during the growth period than does an inert, static, alloplastic material. Interpositional arthroplasty has been the mainstay of treatment for ankylosis for over 100 years. The most popular material previously advocated has been silicone rubber block, which performs well in most instances. There are several problems with interpositional arthroplasties, however, which may compromise the results. When an osteotomy is performed at the base of the condylar neck and an articulation is created at this level, anatomic reconstruction of the TMJ is not accomplished. A hinge motion results, producing an articulation that may not be balanced with the contralateral side. Because function is no longer physiologic, neuromuscular abnormalities, internal derangements, and bony degeneration may occur on the contralateral side. Finally, improper stabilization and fixation of interpositional polymers

(silicone rubber block, Teflon, acrylic, etc.) may result in slippage, extrusion, malocclusion, and compromised jaw function. This is particularly true in ankylosed retrognathic/open bite patients, in whom simultaneous advancement of the mandible necessitates large polymer blocks retropositioned to the advanced mandibular stump. For this reason, we have always advocated securing interpositional blocks to the temporal bone rather than the remaining condylar stump. The design and placement of the Proplast-coated metallic condyle produces anatomic reconstruction in most patients, as well as simultaneous correction of mandibular retrognathia and open bite. Review of the ankylosis patients in this study demonstrates a high percentage of preoperative retrognathia and open bite. Table 9 shows that 90% to 95% of all successful prostheses placed for ankylosis had maintained or increased ramus height, incisal opening, and lateral excursions. We believe these data reflect a more physiologic result. Thus, simultaneous correction of the dental-skeletal problem is a clear indication for use of a metallic condylar prosthesis as opposed to interpositional arthroplasty materials. Rheumatoid arthritis, seronegative arthritides, and idiopathic condylar resorption merit separate discussion because the pathophysiologies of these diseases are different from all other conditions considered here. Rheumatoid and seronegative arthritides are systemic entities, which may not be correctable with conservative measures alone. The

KENT ET AL

Table 9.

253

Postoperative Findings: Ankylosis (76 Condyies) Success (57) Flat

Failure (II) Box*

%

(No.)

21.4 78.6 0

( 3) (11)

Flat

%

tNo.)

%

Box (No.)

D/c

INO.1

of rnt?zcIs

Heighr

Maintained Increased Decreased Total Inrisal

(29) (13) ~ ( 1)

25.0 37.5 37.5 ___

100

(43)

100

34.8 60.5 __4.7

(15) (26)

0 37.5 ~62.5

66.7 0 ~ 33.3

(2) (3) __(3)

(2) (0) __(1)

100

(8)

(3)

opening

Maintained Increased Decreased

0 92.9

( 0) (13) ~( 1)

7.1 100

Total Luieral

(0) (14)

100

67.4 30.2 __ 2.4

(14)

100

~( 2) (43)

100

(0) (3) - (5) (8)

62.7 32.6 __4.7

(27) (14) _( 2)

37.5 25 ~37.5

(3) (2) ~ (3)

100

(43)

33.3 66.7 __0 100

66.7 0 - 33.3

(1) (2) __(0) (3)

excursions

Maintained Increased Decreased

50 42.9

(7) (6) ~ (1) (14)

LLL 100

Total

100

(2) (0) __(1) (3)

100

(8)

* Reported in 43 of 49 cases (87.8%). t Reported in 8 of 10 cases (80%).

Table 10.

Postoperative Immobilization: 109 Condyles Success (85)

Failure (21)

Flat*

Maxillomandibular

Fixation

Not used Used Average duration (wk)

Flat

BOX

%

(No.)

%

(No.1

%

15.8 84.2 2.9

(3) (151

56.7 43.3 2.9

(38)

16.7 83.3 4.5

(2%

BOX

INo.)

(2) (12)

%

100 0 0

(No.)

(7) (0)

* No report in three condyles placed.

ongoing disease process may be quiescent and sudden exacerbations produce debilitating pain and dysfunction. Medical treatment can control the disease in most persons, but deformity of the mandible may be significant, necessitating condylar reconstruction with simultaneous correction of open bite and retrognathia. Because of the disease, however, Table Il.

Prosthesis Failures

Reankylosis Infection Inadequate ramus stabilization Glenoid fossa resorption”

Placement error Metal fatigue Total * Rheumatoid arthritis only

Flat

Box

5 4

1

4

I

0

4 1

0 - 1 14

7

use of a prosthesis rather than an autogenous graft is indicated. Unfortunately, continued inflammation of periarticular soft tissues may be present and glenoid fossa erosion may continue. In our group of seven patients with rheumatoid arthritis who underwent condylar reconstruction (five bilateral), two have experienced severe bilateral glenoid fossa resorption after functioning with the prosthesis for two years or more. Their prostheses have been displaced superiorly, encroaching on the middle cranial fossa (Fig. 7), with development of hypomobility, pain, open bite, and relative retrognathia. Considerable stress occurs at the bonemetal interface in the glenoid fossa because of forces created by the muscles of mastication and mandibular

function.

Because

the fossa is unpro-

tected by a normal fibrocartilage disc and is more susceptible to pressure resorption, we believe that a more even distribution of these forces over a wide area would be biomechanically more favorable.

CLINICAL

254 Therefore, a method of total joint replacement, using the metallic condyle in combination with a custom glenoid fossa implant, has been used successfully in 15 patients during the past 18 months. Although long-term follow-up is not available, we are encouraged by the concept of total joint reconstruction in patients with rheumatoid and seronegative arthritides and idiopathic condylar resorption. In addition, we have used the fossa implant in other condylectomy patients with damaged or lost meniscus to avoid fossa resorption from metal condyles. The fossa implant has also been used as an interpositional arthroplasty material alone because the fossa depth can be predetermined by design and altered at surgery. Finally, changes in design to improve surgical technique and results have recently been introduced to make the condylar prosthesis more adaptable to variations in anatomy of the lateral ramus surface and the angular relation of the glenoid fossa region with the ramus. The improved design includes one L-shaped flange as opposed to two parallel flanges on the shank to be recessed into the lateral ramus surface. By angulating the condylar neck, the shank and flange of the prostheses are parallel to the posterior border of the mandible, particularly in mandibular advancement cases. This should result in easier placement and retention of sufficient stabilization for immediate postoperative function. Furthermore, self-tapping bolts and nuts have been introduced to improve long-term stability. Conclusions The Proplast-coated metallic condyle was successful in 87.3% of cases requiring functional TMJ rehabilitation. The box (TMCK) shank design, with a success rate of 89.4%, was found to be clinically superior to the flat (TMC) shank design with a success rate of 60%. We have found that at least three screws are needed for adequate stabilization. Stabilization is further improved with a fourth screw, when 47 mm condyles are used, a nut engaging one of the screws on the medial aspect of the ramus, or both. This type of stabilization allows immediate postoperative function, which is essential to the success of condylar reconstruction. Placement and stabilization of the prosthesis recently has also been improved with a change in the shank design, alignment of the head, and introduction of a self-tapping bolt and nut.

UPDATE

With this prosthesis, vertical height of the ramus can be predictably restored and maintained and postoperative function improved in most cases. The method has been used successfully in cases where interpositional arthroplasty with silicone rubber block has failed, which suggests that this prosthesis is an improvement on former modes of therapy in some patients. In patients with coexisting ankylosis and retrognathic/open bite deformity, the prosthesis is capable of simultaneously correcting both problems. This is an advantage over the use of interpositional polymer blocks, which are retropositioned in relation to the mandibular stump and are predisposed to slippage and displacement.

Acknowledgments The authors thank the following oral and maxillofacial surgeons for their contribution of cases and retrospective data: Donald H. Chiles, DDS, Leon F. Davis, DDS, MD, Walter Guralnick, DMD. Markell Kohn, DDS, Myer S. Leonard, DDS, MD, Ronald B. Marks, DDS, Robert C. Meador, DDS, Glenn A. Miller, DDS, Michael H. Dyer, DDS, Donald B. Osbon, DDS, Bruce Sanders, DDS, Robert B. Scheffer, DDS, Marvin M. Slott, DDS, Philiu J. Smith. DDS. Richard A. Smith. DDS. George C. Soteranos, DMD, Jim Thatcher, DDS, Department of Oral and Maxillofacial Surgery, Washington University, Barnes Hospital, St. Louis, Missouri, Roger A. West, DMD.

References 1. Hinds EC, Homsy CA, Kent JN: Use of a biocompatible interface for combining tissues and prostheses in oral surgery, in Kay LW (ed): transactions of the IVth International Conference on Oral Surgery. Copenhagen, Munksgaard, 1972, p 210 2. Kent JN, Homsy CA, Gross BD, Hinds EC: Pilot studies of a porous implant in dentistry and oral surgery. J Oral Surg 30:608, 1972 3. Hinds EC, Homsy CA, Kent JN: Use of a biocompatible interface for binding tissues and prostheses in temporomandibular joint surgery. Oral Surg 38:512, 1974 4. Kent JN, Homsy CA, Hinds EC: Proplast in dental facial reconstruction. Oral Surg 35:909, 1975 5. Kent JN, Lavelle WE, Dolan KD: Condylar reconstruction: Treatment-planning. Oral Surg 37:489, 1974 6. Kent JN, Misiek DJ, Akin RK, Hinds EC, Homsy CA: Temporomandibular Joint Reconstruction II: An 8 year Clinical Report on PTFE-Graphite Metallic Prosthesis for Condyle Replacement. First World Biomaterials Congress, Baden near Vienna, Austria, April 8- 12, 1980 7. Misiek DJ, Kent JN, Akin RK, Hinds EC, Homsy CA: Nine-year report on Proplast coated metallic prostheses for condyle replacement. Presentation, 63rd Annual Meeting, American Association of Oral and Maxillofacial Surgeons, Washington, DC, September 21, 1981 8. Kennett, S.: Temporomandibular joint ankylosis: The rationale for grafting in young patient. J Oral Surg 31:744, 1973.