R. Martín-Granizo López¹, J. Giner Díaz², J.J. Sánchez Gutiérrez¹

Recibido: 20.10.05

Aceptado: 29.11.05

1 Médico Adjunto.
2 Médico Residente.
Servicio de Cirugía Oral y Maxilofacial (Jefe de Servicio: Dr. A Berguer).
Hospital Clínico San Carlos. Madrid, España.

Correspondencia:
Rafael Martín-Granizo López
C/ Guzmán el Bueno, 70, 4ºA
28015, Madrid, España.
E-mail: rmartin.hcsc@salud.madrid.org

Introduction

The anchored disc phenomenon (ADP) was first described by Dr. Dorrit Nitzan in 1991 as a possible causative factor of a sudden restriction in mouth opening.^1,2 Later, she herself studied the lubrication process within the temporomandibular joint (TMJ) based on her experience in orthopedic surgery,³ and she finally put forward the pathogenic hypothesis behind this syndrome.⁴ The anchored disc phenomenon has also been termed stuck syndrome. Some authors include it within the variants of the temporomandibular dysfunction syndrome (TMDs), and one of the causative factors of closed lock.⁵

Clinically, ADP manifests as a limitation in mouth opening and laterotrusion towards the contralateral side. It is generally sudden, accompanied by pain on forcing the mouth open, and the end-feel is hard. The suspected diagnosis has to be confirmed by means of a MR imaging study, which typically shows a static disc during opening and closing of the mouth. The treatment traditionally proposed consists in a type of minimally invasive surgery, either arthrocentesis or arthroscopy.⁵

The objective of this article is to show some unusual arthroscopic findings that have not been described previously and that were discovered in a clinical case with ADP.

Clinical Report

A 37-year-old female was referred to our department from another center complaining of pain in both temporomandibular joints that had been evolving for several years. She stated that she had undergone various types of conservative treatment, but that these had been unsuccessful. For a year she had been using a Michigan-type splint that had led to some improvement. She stated that four months previously she had suffered a sudden restriction in mouth opening, together with an increase in pain in the left TMJ, and that from that point she had been unable to use the splint. On being asked if she heard joint noise she said that up until then she had heard a clicking in both joints on opening and closing her mouth, but that this had since stopped. There had been other blocking incidences but these had resolved spontaneously. An oral aperture limitation of 20 mm was observed on examination, together with mandibular laterodeviation to the left side of 2 mm. The laterotrusions were of 5 mm to the left side and 1 mm towards the right side. The left TMJ was painful to palpation and load bearing was positive on the left side. The end-feel was hard, with increased pain in the left TMJ. The initial clinical judgment was of closed lock of left TMJ.

Imaging test were requested. The OPG did not reveal any relevant bone alterations, and the condyles were undeformed and symmetric, although small. The T1 weighted MR sequence showed both TMJs in sagittal and coronal views in closed mouth and maximum open mouth positions. This showed anteromedial disc displacement that was not recaptured by the left TMJ on mouth opening, (Fig. 1) and a disc that was stuck or anchored in the right TMJ (Fig. 2). The T2 weighted sequences showed intra-articular effusion of the left TMJ. The final diagnosis was of disc luxation without reduction of left TMJ, and anchored disc of right TMJ.

With this diagnosis arthroscopic surgery was suggested for diagnosing and treating this pathology. She was operated on under general anesthesia with nasotracheal intubation and prepared according to the normal protocol. An arthroscope similar to the Dyonics HD 900 (Smith & Nephew Inc., TARMA S.A.) was used with a 1.9 mm diameter lens and with an angle of vision of 30º and a xenon light source. The operation was recorded on a U-matic video (Sony VO5630) and images were captured and printed using a video printer (Sony Color Video Printer, Mavigraph UP- 3000P). The right TMJ and the upper right joint space were approached first using a standard posterolateral portal and an intermediate portal for serum outflow. The examination was carried out by means of the usual protocol, posterior to anterior, lateral to medial, and initially a nearly normal joint was observed with no synovitis and with little inflammation of the posterior band (Fig. 3). The correct position of the disc was observed in the open mouth position together with 100% roofing (the percentage of the mandibular condyle that is covered by the disc). This can be verified in the open mouth position by observing if the union between the disc and the posterior band is behind the major axis of the TMJ eminence (Fig. 3). On progressing forward, an erythematous area was encountered that was well-defined and that measured 10 mm in diameter. It was affecting the synovial tissue that was covering the middle part of the eminence (Fig. 4). An examination of the medial portion revealed a fibrous adherence in a line that joined the middle of the articular disc with this area of the eminence (Fig. 5). This was cut by means of direct lysis with the point of the arthroscope (Fig. 6). As the examination of the anterior recess revealed no pathological findings, and as the correct movement of the disc in the joint was verified, extensive intra-articular lavage was carried out with 500 ml of Ringer’s lactate solution, and the right arthroscopy was completed. The arthroscopy of the left TMJ revealed an anterior displacement of the disc without reduction, roofing of 30%, and grade III synovitis with thick adhesions in the anterior joint recess. Anterolateral triangulation was carried out, the adhesions were resected, an anterior myotomy was performed with a monopolar knife and the posterior band was infiltrated with subsynovial injections with corticoids following coagulation with an electric bipolar bistoury.

A home-based physiotherapy protocol was established and the patient evolved satisfactorily. At 6 months she had a maximal mouth opening of 40 mm and laterotrusion of 5 mm to both sides, and the pain had diminished.

Discussion

Some authors have defined the possible pathogenesis of ADP as a sudden adhesion of the articular disc to the fossa that could be caused by changes in the normal lubrication of the joint as a result of intermittent overloading leading to free oxygen radicals (oxidative stress) and a degradation of hyaluronic acid. The end result would be an increase in the friction between the disc and the bone components of the TMJ leading to secondary disc displacement, and later to a degenerative process of the joints (osteoarthrosis).^2-4,6,7 Initially it was thought that the disc was anchored to the fossa by a negative pressure mechanism⁸ although it has now been demonstrated that there is a biochemical change leading to the adhesion of the surfaces.² In this sense, the articular disc, which is slightly concave in the central fibrocartilaginous part, adapts to the bone surfaces in which it is placed (condyle and fossa). It adheres to the glenoid fossa as if it were a suction cup and it therefore remains static during mouth opening and closing. According to various studies the disc will, on most occasions, remain in its proper position although it may sometimes be anchored in an anterior position.⁵ These same studies show that this is the reason why the disc maintains a normal morphology in most ADP cases, as can be observed in the present case (Fig. 2).

Clinically ADP appears as an anterior disc displacement without closed lock. Therefore, for differentiation purposes imaging studies have to be carried out, with MR imaging currently having the most sensitivity and specificity.

In most ADP cases, the disc will adhere to the fossa-eminence of the joint so strongly that conventional conservative treatment (muscle relaxants, occlusal splints...) is unable to solve the problem. As a result of this, many authors propose surgery as the treatment of choice.^6,9 Within the surgical alternatives, minimally invasive techniques seem to be the methods of choice. Arthrocentesis is a technique with very little morbidity that is widely used today for the treatment of various pathologies of the joint, and it can be carried out under local anesthesia.¹⁰ It consists in instilling liquid (generally saline) into the TMJ and the posterior lavage of the joint. On most occasions this is enough to resolve ADP.^6,10 Nitzan and Etsion¹¹ explained the mechanism with which arthrocentesis acts on ADP. Their hypothesis was that by injecting fluid into the superior articular space, the surfaces are separated by means of hydro-dissection, thus helping to restore motility of the articular disc. We believe, as do other authors,¹² that the increase in intra-articular pressure could also lead to the disc being released from the fossa; thus, simple instillation without joint lavage could be enough to resolve many cases of ADP, although lavage carried out later on during the arthrocentesis would help to clean away all the toxins, proteins and inflammatory substances that accumulate in the joint.¹³

Arthroscopy is a highly effective technique for dealing with ADP that also provides images of the joints, allowing work to be carried out directly on the different structures. It has been used traditionally in different pathologies such as TMDs or osteoarthrosis.^9,14 Its use has also been described for treating ADP, although a recent study by Sanroman compares arthroscopy with arthrocentesis. No significant differences were found between these techniques, and both were equally effective for treating ADP.⁶ He describes the arthroscopic findings in the TMJ with ADP, reporting that the rate of roofing that in most cases was between 75% and 100%, as in the case we present. Synovitis of the posterior band was the most common finding, although in the present case there was none, and fibrous adhesions were common.⁶ With regard to adhesions, it should be pointed out that it is a relatively frequent finding in joint pathology, although most appear in the anterior and medial recesses of the TMJ.¹⁵ In fact, in our personal experience of more than 320 arthroscopies, we have never found an adhesion that was situated in the middle portion of the articular disc and fossa without associated synovitis (Fig. 5 and 6). But, possibly the most surprising discovery in this case was the erythematous area found in the middle area of the glenoid fossaeminence, and the normal appearance of the synovial membrane surrounding it (Fig. 4). Our hypothesis is that the releasing of the adhered disc, which was carried out immediately before introducing the cannula into the posterior recess and instilling saline, could have produced the erythematous area as a result of a hemorrhagic subfusion as both tissues were released, leaving a mark similar to that left by a suction cup in a window when it is unstuck. The adhesions in this case could be due to the lengthy evolution of ADP, as it has been demonstrated that these are more frequent in cases that have been developing for longer.¹⁵

Future studies may possibly be necessary that correlate arthroscopic findings in ADP in order to ascertain whether what was found in our case is specific to this pathology.

References

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