Silastic implant as a part of temporomandibular joint arthroplasty. Evaluation of its efficacy

British Journal of Oral and Maxillofacial Surgery (1987) 25, 227-236 © 1987 The British Association of Oral and Maxillofacial Surgeons

SILASTIC IMPLANT AS A PART OF T E M P O R O M A N D I B U L A R J O I N T ARTHROPLASTY. EVALUATION OF ITS EFFICACY SABAH KALAMCHI,* B.D.S., L.D.S.R.C.S., F.F.D.R.C.S., and ROBERT V. WALKER, D.D.S., F.D.S.R.C.S., F.F.D.R.C.S.

Department of Oral Surgery, UTHSCD, Dallas, Texas 75235 Summary. A study was made of 68 patients who had undergone an intra-articular temporomandibular joint (TMJ) arthroplasty, using silastic implants as a part of the procedure, between 1970 and 1985. The use of silastic as a part of the arthroplasty was made when the disc was non-salvable because of perforation or destroyed because of ankylosis or previous surgery. At surgery, all patients had upper and lower arch bars fixed to their teeth by wiring in order to facilitate post-operative nocturnal elastic intermaxillary fixation of the teeth in occlusionas a part of a 3-monthperiod of follow-upphysiotherapy. Both surgery and the follow-upphysiotherapywere considered of equal importance in the management of these patients. The study showed that 63 of 68 patients were relieved of their pre-operative signs and symptoms by the surgery and follow-up physiotherapy. These 63 patients have had no recurrence of their problem.

Introduction Arthroplasty, the creation of an artificial joint for restoration of temporomandibular joint (TMJ) movement, was first described by Barton of Philadelphia in 1826. He cut through the neck of the condyle to mobilise a jaw tethered by joint ankylosis. This was followed by Esmarch's report in 1860 describing the removal of a wedge shaped piece of bone from the ascending ramus of the mandible anterior to the point of ankylosis which created a false joint (Ward, 1961). Since then the insertion of a biologically acceptable alloplastic material became popular in surgery of the TMJ as an aid in preventing osteogenesis and re-ankylosis and to provide a satisfactory surface against which bone could move. Metal (Silver et al., 1977), proplast (Kent et aI., 1983), and silastic (Kreutziger & Mahan, 1975), are c o m m o n materials currently used. Reports on the use of silastic suggest both success and failure in its use, the most common complication being displacement when employed as an implant in the TMJ. That has not been a general finding when silastic has been used in the TMJ at this institution (Gallagher & Wolford, 1982). The aim of this paper is to describe a technique for arthroplasty of the TMJ where silastic is used as a part of the procedure and immediate 3-month follow-up physiotherapy to rehabilitate the jaw and joint back to normal use, Such physiotherapy is an important factor in the overall management of the patient.

Patients and methods Case records of 68 patients who have had a TMJ arthroplasty using silastic implants, were studied. The surgery was performed to help relieve Chronic TMJ

*Requests for reprints

(Received 12 January 1987; accepted 17 February 1987) 227

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pain and to improve limited mouth opening, Patients included in the study had the following conditions present prior to surgery: 1. There was clinical and radiographic evidence of osteoarthritis of the TMJ with distinct unfavourable changes of joint integrity associated with an unsalvable disc. 2. There had been prolonged internal derangement of the TMJ associated with loss of pliancy, severe thinning, or other impairment of the disc. 3. There was failure of previous surgery to the TMJ which included various implants to the joint.

Surgical technique A standard pre-auricular incision approximately 5-6 cm in length is used for all patients. The wound is deepened by alternate blunt and sharp dissection to the temporalis fascia and then extended inferiorly along the temporalis fascia to the zygomatic arch and upper extent of the TM,I lateral capsule (Fig. 1). By blunt dissection the capsule is cleanly exposed approximately 1-1.5 cm in an inferior direction. A vertical incision is made through the capsule directly to the bone of the condylar neck and extended superiorly to the zygomatic arch. The upper limb of this incision remains just superficial to the disc. Opening of the upper joint space is avoided at this point. The periosteum and capsular attachments are freed around the condylar neck and in so doing, the lower joint space is entered to expose the condyle (Fig. 2). Appropriate retractors are used to protect the soft tissue around the condyle. An approximate 2-4 mm vertical height of the condylar head is excised using a number 701 crosscut fissure bur run under sterile saline irrigation. The raw condylar stump is then smoothed with a bone file or bur. At this point, if the disc is found to be perforated (Fig. 3), displaced with loss of pliancy, or extraordinarily thin, it is excised (Fig. 4). If previous surgery has been performed to the joint and the disc has been replaced by an alloplastic material, the prosthesis is removed. The arthroplasty is now completed using silastic as an attachment to the

Fig. 1

Fig, 2 Figure l--Joint capsule exposed. Figure 2--Condylar head exposed.

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Fig. 4

Fig. 5 Figure 3--Upper and lower joint spaces opened and demonstrating a disc perforation. Figure 4---Specimen, perforated discs and tops of condyles, right and left TMJs. Figure 5--Silastic disc attached to condylar stump by wiring through the condylar neck and the silastic disc; wires tightened against posterior condylar neck.

top of the raw condylar stump (Fig. 5). Two holes are drilled through the condylar neck approximately 3 m m below the cut edge of the stump. The holes are drilled diagonally from the posterior aspect in a medial and anterior direction to the front of the condylar neck. One hole is started near the centre of the condylar neck posteriorly and the other hole is started near the lateral pole. A disc slightly larger

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than the top of the condylar stump is then cut from a 3 mm thick sheet of silastic and made available for attachment to the stump. Two separate 25 gauge stainless steel wires are passed through the two previously drilled holes and thence through and across the top of the silastic disc atop the stump in a mattress manner. The wires are tightened securely by twisting at the back of the condylar neck, firmly fixing the silastic disc atop the condylar stump (Fig. 5). The jaw is then moved in various excursions including a wide open position to be certain that the condylar stump with the attached silastic implant moves easily and without hindrance.

Follow-up physiotherapy The role of post-operative physiotherapy cannot be over-emphasised. Arch bars are attached to the upper and lower teeth at the time of surgery. These are used for the placement of two or three small elastics at night to hold the teeth in firm occlusion while the patient is sleeping. The elastics are removed on awakening the following morning for full day time use of the jaw. The night elastics are placed the second night after surgery and are then continued for the next 3 months. Jaw opening, stretching and levering are begun the second day after surgery. Jaw range of motion is progressively increased daily during the first 3 or 4 weeks after surgery to eventually exceed an incisal clearance of 40 ram. It is important to reach an incisal opening of 40 mm within the first 3 or 4 weeks after surgery, and to continue the regime of day time use of the jaw and night time immobilisation in the correct occlusal position over a 3-month period. The rationale for holding the teeth and jaw in the correct position at night using the small elastics is to allow healing to occur. Use of the jaw during the day obviously disrupts healing, but it allows jaw range of motion to progressively increase to normal through the use of passive and active stretching movements of the jaw. The alternate use of the jaw during the day and immobilisation at night in the correct occlusal position over a 3-month period permits maturation of scarring to accommodate the full range of jaw movements and yet maintain stable jaw, occlusal, and TMJ positions. Firm fixing of the silastic disc to the condylar stump allows immediate jaw use after surgery without fear of the disc being displaced. A progressively increasing range of jaw movement prevents the restraint of tight scarring within the joint or similar restriction in the extracapsular area which are probable causes of long term tethering of the jaw and pain after surgery. A scar which severely limits jaw opening will cause pain when there is an attempt to move the jaw beyond the tethering effect of the scar. Accordingly, all efforts are made to achieve wide opening of the jaw before the binding effect of scarring is reached. The rationale of the 3-month period of physiotherapy is directed toward allowing all tissues in the area to move smoothly and not become bound before the fullest possible range of opening is reached. An incisal opening of 40 mm is regarded as the minimum toward which the physiotherapy is directed. Each of the 63 successfully managed patients in this series maintained a stable occlusion following this manner of rehabilitation. No occlusal adjustment was required for any patient. Occlusal splint use is not necessary nor considered for any patient.

Results The 68 patients analysed in this study were treated during the time period

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1970-1985. The age and sex distribution of patients are shown in Figures 6 and 7. Seventy-six per cent of the patients treated were over 30 years of age and 97% were female. The length of post-operative follow-up can be seen in Figure 8. Follow-up ranged between 6 months as the shortest period with 14 years 7 months being the longest follow-up time. Over 30% of the patients had a follow-up of more than 5 years and 42% had a follow-up of over 1 year.

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The presenting signs and symptoms of the patients can be seen in Figure 9, the most common reason for patients to seek treatment being pain. Ninety-five per cent of patients complained of pain at their first visit, 79% complained of dysfunction and limited mouth opening, while 12% commented about noticeable joint noise during the initial examination. All patients had pre-operative and post-operative right and left transpharyngeal radiographs of the TMJs in closed and open positions of the jaw. In all patients, pre-operative radiographs showed limited condylar translation in the open jaw position and in 91% of the pre-operative radiographs there were unequivocal changes consistent with osteoarthritis.

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In 59 patients, the histopathology report of the excised condylar top confirmed the presence of osteoarthritis, while in seven patients the histological pattern of the condyle was found to be normal. In two cases, histopathological examination of the condyles established the existence of osteomyelitis (Fig. 10). All patients had measurements made of pre-operative incisal opening, incisal opening at the completion of the 3-month period of physiotherapy, and incisal opening at the time of the last follow-up examination. As an arbitrary consideration, a 40-60 mm incisal opening is considered a normal range of opening. Even though it is known that many people function well with an incisal opening considerably less than 40 ram, for the purposes of this study when an incisal opening was less than 40 mm it was judged that a tethering effect was operating somewhere about the joint. No patient who has an incisal opening beyond 40 mm feels that there is restraint in jaw opening. Most patients begin to notice that some limitation in incisal opening is beginning to occur at the 35 mm level. Patients occasionally strike their teeth with eating utensils or their toothbrush at an incisal opening in the 30 mm range, and dentists consider that there is restricted access to a patient's mouth at a 30 mm incisal opening. When a patient has an incisal opening of 25 mm or less, he is considered to be overtly compromised. Accordingly, all physiotherapy following surgery of the TMJ is directed toward regaining a pain-free incisal opening of 40 mm or more. The lowest pre-operative incisal opening of any patient in the study was 9 mm and the widest was 34 mm with a mean of 29 ram. At long-term follow-up, the lowest incisal opening of any patient in the group of 63 patients who were considered successfully managed by the surgery and follow-up physiotherapy was 38 ram, and the widest opening was 50 rain with a mean of 42 mm (Fig. 11). Most of the patients were referred from general dental practitioners who had previously treated the patients by non-surgical means. Eight patients had previous surgery to their joints. Even though 63 patients were relieved of their pre-operative signs and symptoms by the surgery and physiotherapy described, the remaining five patients included in the study have had persistence of their' pre-operative signs and symptoms, including pafn and a limited incisal opening.

Fig. 12A Figure 12A--A pre-operative transpharyngealradiograph of a 59 year-oldwomanwith severe pain and osteoarthritis of right TMJ when first seen in July 1971.

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Discussion

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Sixty-three of 68 patients who had silastic used as a part of TMJ arthroplasties performed for relief of pain and/or dysfunction because- of 0steoarthritis and unsavable discs fared well over a long follow-up period. From a clinical standpoint, tissue tolerance of the silastic was deemed satisfactory because there were no signs of rejection. The longest follow-up period was 14 years and 7 months for a patient who had surgery in August 1971 (Fig. 12A-D). The patient had excellent function with a normal incisal opening (47 ram) and excursive movements of the mandible. There were no signs or symptoms of pain or discomfort even though the last radiograph

Fig. 12B Figure 12B--Immediate post-operative transpharyngeal radiograph of right TMJ after arthroplasty with silastic disc attached to condylar stump, August 197l.

Fig. 12C Figure 12C--Transpharyngeal radiograph of patient's right TMJ 1 year after surgery, August 1972.

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Fig. 12D Figure 12D--Follow-up transpharyngeal radiograph of patient's right TMJ, 14 years 7 months after surgery; fixation wire broken through fatigue; no symptoms; normal condylar movement. Silastic is displaced.

showed that the original fixation wire for the silastic had broken (Fig. 12D), probably because of metal fatigue. Silastic does compress and will return to its original form. Such repetitive, microscopic bending of the wire probably caused it to break. This did not cause displacement of the silastic, interfere with jaw function or cause pain or discomfort. Of the five arthroplasties considered as failures, two patients had multiple operations on the failed joint in the past. These two patients were noncompliant in their follow-up physiotherapy. Another two patients had their arthroplasties repeated because there was a relapse in TMJ function and a reduction of incisal opening to less than 10 mm over a year after the original surgery. The fifth patient had displacement of the silastic implant which required removal. References Barton, J. R. (1826). On the treatment of anchylosis by the formation of artificial joints. North American Medical and Surgical Journal, 3, 279. Esmarch, F. (1860). In: Behandling der Narbigen Kieferklemmer dutch Bildung eines Kunsdichen Gelenkes im Unterkiefer. Kiel: Schwers. Gallagher, D. M. & Wolford, L. M. (1982). Comparison of silastic and proplast implant in the temporomandibular joint after condylectomy for osteoarthritis. Journal o[ Oral and Maxillofacial Surgery, 40, 627. Kent, J. N., Misiek, D. J., Akin, R. K., Hinds, C. E. & Homsy, C. A. (1983). Temporomandibular joint condylar prosthesis: a ten year report. Journal of Oral and Maxillofacial Surgery, 41, 248. Kreutziger, K. L. & Mahan, P. E. (1975). Temporomandibular degenerative joint disease: diagnostic procedure and comprehensive management. Journal of Oral Surgery, 40, 297. Silver, C. M., Motamed, M. & Carlotti, W. E. (1977). Temporomandibular joint with the use of vitallium condylar prosthesis. Report of three cases. Journal of Oral Surgery, 35, 909. Ward, T. G. (1961). Surgery of the temporomandibular joint. Annals of the Royal College of Surgeons, 28, 139.