Temporomandibular joint disorder (TMD) is a collective term for a range of different clinical problems that encompass the muscles of mastication, the temporomandibular joint (TMJ) and the associated structures [1, 2]. It is estimated that 20–30% of adults [2, 3] will experience the symptoms of TMD. The aetiology of TMD remains unknown but is thought to include parafunctional activity, stress, previous trauma and internal derangement of the disc complex [2].

Closed lock is a specific type of TMD where there is derangement of the articular disc complex and refers to the displacement of the disc, most commonly anteromedially, without reduction and resultant limited mouth opening [4].

In a normal joint, on initial mouth opening, the condylar head rotates followed by translation along the articular eminence on further opening. The articular disc will translate with the condyle to remain interpositioned between the head and the eminence. In patients with closed lock, the translation of the condyle is limited by the failure of the meniscus to reduce, as a consequence of the disc being displaced, most commonly anteromedially, with the posterior band becoming trapped anterior to the condyle [5]. It has been postulated that the articular disc may be attached to the eminence via adhesions, preventing reduction and has been linked with osteoarthrosis [6].

Closed lock can be described as being acute or chronic depending on the duration of locking [4] and is frequently accompanied with characteristic symptoms including: significant jaw pain, limitations of jaw movement (namely reduced maximal opening) and functional impairment (eating) [7]. However, a number of patients with anteromedial meniscus displacement report no clinic symptoms [8, 9] indicating that other factors are influential to the aetiology and severity of closed lock [9]. These factors include the depth of the glenoid fossa, the steepness of the eminence and the size of the condylar head [8].

The treatment modalities for closed lock are well documented within the literature and include both medical and surgical management options. Medical management includes the use of non-steroidal anti-inflammatories, steroid therapy, rehabilitation with orthotic devices, physical therapy and cognitive behavioural therapy [7]. The minimally invasive surgical options including arthroscopy and arthrocentesis are considered as first-line surgical modalities, with open surgery including: condylar shave, plication procedures and eminectomy of the articular eminence as alternative, secondary surgical procedures [7]. The consensus of the current literature is that surgical treatment for TMJ disc displacement without reduction, including that of closed lock, should be deferred for a minimum of 6 months to allow sufficient time for comprehensive medical management and rehabilitation [4, 7]. Closed lock that proves refractory to non-surgical interventions should then be considered for an interventional surgical approach. In this retrospective study, the rationale for eminectomy as a surgical treatment option for closed lock is the removal of the articular eminence, which thereby eliminates the anatomic structure against which the articular disc becomes trapped on mouth opening and thereby relieves some or all of the symptoms. It has been hypothesised that articular eminectomy may successfully treat patients suffering closed lock and was first described by Stassen and Currie in 1994 [8]. The pilot study concluded that ‘Eminectomy appears to be a safe and simple method of reducing a closed lock of the TMJ’ [8].

Eminectomy as a standard surgical procedure was carried out by a preauricular incision using the Al-Qayat Bramley approach to expose the articular eminence followed by adequate removal and recontouring of the articular eminence using a bone saw [10]. This procedure helps to eliminate mechanical interference and facilitates a smooth functioning surface for the joint translation. Unlike some open TMJ surgical procedures, the procedure is intra-capsular and the disc is not surgically repositioned and there is no interference with the internal joint mechanism [5]. The surgical treatment has a potential risk of damage to the temporal and zygomatic branches of the facial nerve. The literature reports varying degrees of incidence, from 9 to 18% of patients reporting transient weakness of facial nerve post-operatively [4]. The success of the operation can be measured by the following criteria: reduction in pain, improvement in function (mouth opening) and reduction in clicking.

This study aims to assess the effectiveness and role of eminectomy as an alternative surgical option for the management of chronic closed lock.