Temporomandibular Joint Arthroscopic Lysis and Lavage Compared to Operative Arthroscopy in Disc Displacement With Reduction: a Randomised, Double-blind, Controlled Trial

1. BACKGROUND The temporomandibular joint (TMJ) is a bilateral joint comprised of two cartilage covered bone surfaces that articulates against each other during mouth opening and closing. A dense cartilage disc is situated between the two joint surfaces creating two separate joint compartments.

Disc displacement (DD) is characterised by an improper position of the TMJ disc relative to the articulating surfaces and affects up to 30% of the population. DD with reduction (DDwR) is a sub-diagnosis of DD where the disc has got displaced, often in an anteromedial direction. During mouth opening the disc reduces into its right position with a snapping sound and on mouth closing the disc dislocates again. DDwR is often not affecting the patient but under somewhat unclear circumstances it might sometimes create pain and severe functional disability. A recent Swedish publication has shown that patients with TMJ disorders had significantly more days of work disability (2-3 times more) compared to a non-TMD cohort followed over a ten year period. The reliance on social security benefits in the group of patients that had TMJ surgery more than once were more accentuated compared to other TMJ disorder patients.

The primary treatment for DDwR is non-surgical, most often physiotherapy and/or occlusal splint therapy. If non-surgical treatment fails the Swedish National Board of Health and Welfare primarily recommends open joint surgery, discectomy. TMJ arthroscopy in this situation has been assessed with a low level of evidence, thus not primarily recommended. Although, there are several publications rating arthroscopy as a potentially good DDwR treatment, but these publications often present their results mixing several TMJ diagnoses and most often in the form of retrospective case series, making clear conclusions hard to make. Another problem with present studies on TMJ arthroscopy due to DDwR is that successful treatment seldom is predefined as parameters to be fulfilled considering both clinical measurements and patient reported outcome. Instead, one parameter after another is analysed in singularity, which unfortunately do not give the reader the whole picture. Although, in a couple of studies a weighted success rate is demonstrated where arthroscopy seems very successful treating DDwR with rates between 81-90 %. This is well in parity with earlier studies on discectomy declaring around 85% success rate.When comparing the two different surgical methods discectomy and arthroscopy, arthroscopy is less invasive, almost no negative side effects, shorter operating time, and shorter rehabilitation and sick-leave.

Arthroscopic treatment of DDwR has been described with two different methods, arthroscopic lysis and lavage (ALL) and operative arthroscopy with anterior release (OAA), never compared with each other in a randomised controlled fashion. ALL is performed with a rod-shaped lens inserted into the TMJ cavity enabling direct visualisation, The operative procedure involves manipulation of disc position, semi-blind release of adhesions (lysis), and irrigation (lavage) of the joint with either saline solution or Ringer's solution. Generally the procedure is performed under general anaesthesia, but there are reports on ALL performed in local anaesthesia or conscious sedation. OAA is basically an ALL expanded with an extra instrument canal/working cannula inserted into the TMJ enabling ablation of the anterior disc attachment and scarification (coagulation) of the posterior attachment under direct visualisation. The OAA procedure is performed under general anaesthesia. Comparing ALL and OAA has been done in a retrospective manner, and in patients with DDwR there were a 30% difference in MIO postoperative at 6 months in favour of OAA and almost the same difference when considering TMJ pain.

Synovial fluid from the TMJ has been used since the mid-90's mostly for analysing inflammatory markers. Proteomics is a relatively new technique for analysing protein profiles and has only been applied a couple of times in the field of TMJ pathology. Since the aetiology of DD is still not known, proteomics provides a comprehensive insight of the protein profile of TMJ disorders.