Movement of the temporomandibular joint during tracheal intubation

Abstract

Laryngoscopy causes temporary postoperative dysfunction of the temporomandibular joint (TMJ): during iatrogenic TMJ manipulation in anaesthetised patients, the TMJs have lost the protection afforded by the tone of the surrounding muscles. Thus far, the exact type and extent of TMJ movements have not been known. The purpose of this study was to develop a method to visualise and assess TMJ movements during intubation by means of electronic axiography, a diagnostic monitor of TMJ movements used in dentistry: registration of the hinge axis (HA) as an equivalent of the condylar paths on extra-oral sagittaly mounted, parallel plates. The HA is individually defined in each patient by the pure, rotating TMJ movement during initial mouth opening (no farward gliding of the condyles, incisor distance up to 10 mm). The parallel plates are placed in the TMJ region in the skull-mounted plate bow: both registration tips ("drawing" the HA tracings on the electronic plates) are connected to the mandible by a face bow, paraocclusally fixed to the teeth. The face bow is individually shaped for each patient to allow mask ventilation and free movement of the laryngoscope during intubation. HA tracings are registered and calculated for both sides independently every 24 ms with the SAM/Klett system and presented on sagittal and frontal projections. In the operating theatre, the active mouth-opening traces (MOT) are registered first and the passive endotracheal intubation traces (EIT) after induction of anaesthesia (same head position). With informed consent and approval by the ethics committee of the Landesärztekammer Rheinland Pfalz. 40 male patients (ASA I. Mallampati I, limb surgery) were randomly allocated to four groups (n = 10 each). OS: Oral intubation, suxamethonium (1.5 mg/ kg); OV: Oral intubation, vecuronium (0.1 mg/kg); NS: Nasal intubation, suxamethonium (1.5 mg/kg); and NV: Nasal intubation, vecuronium (0.1 mg/kg). Intubation was performed 100 s after injection of the relaxant. Pre- and postoperatively (every 24 h over 3 days, in case of positive findings longer) recorded were: active movements of the mandible (maximal mouth opening/ max. laterotrusion); dysfunction of the TMJ; and pain sensation in the TMJ (Helkimo rating). MOTs and EITs were recorded and analysed with the system described and typical EIT patterns were identified: bland, clinically uneventful intubations (n = 7), massive distraction and laterotrusion of the EIT compared to the MOT (n = 24), and blocked or limited TMJ movements resulting in intubation problems (n = 1). With the method presented, TMJ movements could be visualised during endotracheal intubation for the first time. It can be used to assess techniques, routes, and instruments for intubation as well as to evaluate potential traumatising movements during endotracheal intubation.