Arthroscopic Anterior Release Versus Discectomy as Treatments for Temporomandibular Joint Disc Displacement With Reduction: a Retrospective Controlled Study

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 (DE). TMJ arthroscopy in DDwR might encompass different treatment modalities such as arthroscopic lysis and lavage (level 1 arthroscopy), operative arthroscopy with anterior release (OAA) (level 2 arthroscopy), and operative arthroscopy with disc suturing (level 3 arthroscopy). The arthroscopic treatment of DDwR in this situation has been assessed with a low level of evidence, thus not primarily recommended by the Board of Health and Welfare. No studies comparing DE to arthroscopy treating DDwR are published. Even though there are several publications rating arthroscopy as a potentially good DDwR treatment, 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 might mislead the reader. 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 DE declaring around 85% success rate. When comparing the two different surgical methods DE and arthroscopy regarding other factors than surgical outcome, arthroscopy is less invasive, with almost no negative side effects, shorter operating time, and shorter rehabilitation and sick-leave.

Since there are no studies comparing arthroscopy to DE as treatments for DDwR, the aim is to perform a retrospective controlled study. 2. HYPOTHESIS/RESEARCH QUESTIONS OAA has an equal outcome compared to DE treating patients with DDwR. The outcome will be longitudinally evaluated with a combination of maximum mouth opening capacity, patient reported TMJ pain, and TMJ disability, at pre-determined time-points during a 6-month postoperative period.

The primary research question is which of the two surgical methods that best improves the above stated variables.