Abstract
Anterior disc displacement is one of the most frequent types of temporomandibular joint disorders. Various arthroscopic disc repositioning and suturing techniques were reported to treat patients with disc displacement in the 1990s, but the success rate and long-term stability was not satisfactory. This report describes a new repositioning and suturing technique and discusses its advantages and disadvantages.
Anterior disc displacement is one of the most frequent temporomandibular joint (TMJ) disorders, which often results in clicking, joint pain, a limited range of motion and masticatory difficulties. Disc repositioning is a common procedure for patients with disc displacement to eliminate mechanical interference, to relieve pain and to improve the range of motion. It was first described by Annandale in 1887. Following the development of radiology and medical materials, various modified disc repositioning techniques have been reported over the last three decades. Good results have been reported, with success rates ranging from 77% to 100%. Arthroscopy has proved to be a clinically useful procedure to treat disc displacement. Some clinicians have tried to reposition the disc arthroscopically with various suturing techniques, but the success rate and long-term stability have not been satisfactory.
In the authors’ department, therapeutic arthroscopy has been carried out for more than 30 years. In the 1990s, displaced discs were repositioned according to the methods described by McCain et al. and Ohnishi, but the success rate was not high. A new arthroscopic disc repositioning and suturing technique was designed in 2001, which had been used in 2167 patients (2622 joints) by July 2011. Regarding this technique, the authors consider the following points: the indications for arthroscopic disc repositioning; the disc repositioning technique; postoperative clinical evaluation of short- and long-term results; and magnetic resonance imaging (MRI) evaluation of the short- and long-term results for disc position and condylar remodelling. The authors think that it is important to prove this new disc repositioning technique has high effectiveness before the detailed technique is introduced. We published an MRI evaluation of the short-term results of this disc repositioning technique, which demonstrated a high success rate of 95.42%.
Anterior disc displacement of the TMJ can be categorized as: pure anterior displacement; anterolateral displacement; or anteromedial displacement. The disc repositioning techniques for these situations are not the same. Since pure anterior displacement is the most common, this report will describe the technique for pure anterior displacement and discuss its advantages and disadvantages.
Surgical technique
A 2.3 mm arthroscope, including a video surveillance system and an image printer (Stryker, San Jose, CA) with a 2.8 mm outer protective cannula, is used. The TMJ disc suturing instruments contain a 12-gauge suturing needle and a pair of self-designed needles with an exchangeable lasso-type and hook-type suture gripper (Shanghai ShenDing Industrial Co. Ltd., Shanghai, China). The disc repositioning suture is a custom-made, non-resorbable surgical suture made of medical woven polyester with an inner core (Shanghai Pudong Golden Ring Co. Ltd., Shanghai, China).
The diagnosis of anterior disc displacement is made according to clinical assessment and preoperative MRI ( Fig. 1 a) . The procedure is commonly performed under local anaesthesia. The triple-channel arthroscopic technique of McCain et al. is used. After the first puncture of the fossa, a systematic diagnostic arthroscopy is carried out ( Fig. 1 b). A second puncture is carried out aiming at the anterior recess under direct arthroscopic visualization.
Anterior release
Through the working cannula additional local anaesthesia is injected to avoid pain and to decrease bleeding; it can also reduce the risk of masticatory muscle nerve injury. The coblation probe is inserted to cut the anterior attachment of the disc and the neighbouring part of the lateral pterygoid muscle. The incision line is located approximately 2–3 mm anterior to the anterior band of the disc and is carried out across the whole width from medial to lateral. The depth of the anterior release is no more than 2 mm to avoid breaking large blood vessels and damaging the masticatory muscle nerve in the anteromedial synovium. A sharp trocar is inserted to release the fibres further.
Disc reduction
After the anterior release is completed, the obturator is positioned at the anterior margin of the disc and the disc is pushed backwards. The obturator slides along the surface of the disc and arrives in the posterolateral recess. The retrodiscal tissue is pushed down inferiorly and posteriorly.
Disc suturing
Between the first two punctures, a point is marked on the skin, which is commonly 1.0 cm anterior of the first puncture site. A 12-gauge suturing needle perforates the joint capsule and is inserted into the upper joint space. The arthroscope is moved to find the tip of the needle.
Under direct visualization, the tip of the needle is inserted into the junction of the disc and the retrodiscal tissue near the lateral synovial groove. The needle is pushed in and comes out of the retrodiscal tissue more medially ( Fig. 2 ). A third puncture is performed through a transmeatal approach. The point of puncture is at the anterior wall of the external auditory canal and is usually 10 mm away from the tip of the tragus. A custom-made needle with an exchangeable lasso-type suture gripper is inserted into the posterior recess and faces the tip of the first needle. A custom-made nonabsorbable surgical suture is put into the first needle. Once one of the ends of the suture comes into view under the arthroscope, it is caught by the lasso and pulled through the third portal, leaving the external auditory canal ( Fig. 3 a and b) . The first needle is retracted from the retrodiscal tissue but remains in the joint cavity. The second, also custom-made, hook-type gripper is fed into the lateral part of the posterior recess via the third portal, and the other end of the suture is pulled through, leaving the external auditory canal again ( Fig. 3 c and d). The suturing needle is removed.
to 
(L, lateral; M, medial). (b) Arthroscopic view of the puncture point for the suture needle. (c) The tip of the needle reaches the upper joint space again. (d) Arthroscopic view of the tip of the suture needle. 
A second suture is commonly performed for most patients to keep the disc stable. The point of puncture on the skin for the suturing needle is usually 5 mm posterior to the first one. The needle perforates the joint capsule and enters the posterior pouch in the same direction as the arthroscope. Under arthroscopic guidance, the needle tip enters the retrodiscal tissue between the visible parts of the first suture and leaves it medial of the medial part of the first suture. The following steps are performed as described for the first suture. After suturing is completed, the arthroscope is moved from posterior to anterior to check whether disc repositioning is satisfactory. If not, the anterior release is extended using the coblation device until the disc can be repositioned freely. The sutures are then tied, with the knots underneath the cartilage of the external auditory canal ( Fig. 4 a and b) . The skin incisions are closed.
