Temporomandibular Joint Movements during Rigid Bronchoscopy and Laryngoscopy under General Anesthesia and Pre-Post Intervention Comparisons

Rigid bronchoscopy, introduced by G. Killian in 1898, prevailed until it became largely replaced by the fl exible fi ber bronchoscope introduced by S. Ikeda in 1966. In recent decades it experienced a renaissance as new interventional techniques require general anesthesia with safe ventilation and suffi cient access for instrumentation. In contrast to intubation via laryngoscopy where the fl oor of the mouth is lifted by inserting the scope above the epiglottis, the rigid bronchoscope is introduced by lifting the base of the tongue and the epiglottis with the scope and entering the larynx (Figure 1). In both procedures the temporomandibular joint undergoes a considerable passive rotational and translational forward movement. Abstract


Introduction
approximately assessed by the distance of the cuting edges of the teeth. However measuring of lateral movements and protrusion can not be precisely measured, bacause this and other methods ar static. Electronic movement registration is user independent and creates an objective storable image. The CADIAX III system (GAMMA AG, Klosterneuburg, Austria) allows the user to present translation and rotation separately and in temporal progression. To establish the basic feasability of the project, a preliminary test was performed in a dummy (Figure 3,4).
The temporomandibular joint (TMJ) is unique in the human musculoskeletal system and different in its phylogenetic origin. Quadratum and mandibulare (Meckel´s cartilage) derive from the fi rst visceral arch. Between them the primary TMJ is positioned, which is converted into the hammer-anviljoint. The bigger, frontal part of Meckel´s cartilage delivers the mandible. Between mandible and skull a new joint is formed.
This secondary joint is to be found in mammals only.

Anatomy and physiology of the temporomandibular joint
The short and pertinent defi nition of the temporomandibular joint presented by the Viennese anatomist Harry Sicher still applies: The temporomandibular joint is a synovial gliding joint with a fl exible socket [1]. The bony parts are the fossa and eminentia articulare on the temporal bone and the caput mandibulae ( Figure 2). These bony parts are completed by the articular disc located on top of the caput mandibulae and the extensive articular capsule surrounding the system. The articular disk separates an upper from a lower compartment.
Clearly distinguishable ligamentary structures are embedded in the capsule which form rational boundaries of terminal positions [2]. The activity of the temporomandibular muscles is required for guiding and positioning the joint. This function was demonstrated inter alia in 1973 by the "group of four" led by R. Slavicek. Infusion of curare to conscious subjects caused a slackening and downward motion of the mandible [3].  [4]. From a dental surgery point of view, it is essential that the anesthetist should establish the range of mandibular movement when examining a patient by assessing the visibility of the palate and uvula (Malampati score). This at least gives him or her a rough idea whether any restrictions are present [5,6]. There are very many possible reasons for an inability to open the mouth to its fullest extent, but a description would be beyond the scope of this study.

Method for Measuring the Movements of the Temporomandibular Joint
Mechanisms to record lower jaw movement meanwhile are common in dentistry. Before the introduction of electronic registration systems, mechanical devices were long in use.
However, as the motion oft he condyles is hardly more than 10mm, for interpretation one needs an 8x magnifying glass.
With the Helkimo-Index the maximum opening can be   An uncompromised function curve of the temporomandibular joint shows concavity, is long enough, excursion and incursion are identical, both sides are equal and there is no side shift.
In an anesthesized and relaxated patient it is possible that by laryngoscopic intubation or insertion of a rigid bronchoscope passive stretching of the capsule and ligaments may cause serious damage to the joint. After stretching of the ligaments, in extreme movements even luxation may occur. The aim of the study was to investigate, whether rigid bronchoscopy and laryngoscopy are causing extreme excursions of the joint and may lead to persisting trauma Table 1.
-Does a before and after comparison suggest that irritation or trauma has occurred?

Patients and Procedures
Fifteen patients took part in the study. We selected patients over 18y from the Thoraxklinik who gave their informed consent. Patients were eligible who understood the procedure and had suffi cient dentition in their lower jaw to allow a paraocclusal clutch to be put in place. A paraocclusal clutch is an adjustable metal tray with a synthetic matrix that is affi xed laterally to the teeth of the lower jaw such that the upper and lower teeth almost touch, whilst at the same time allowing lower jaw movement to be plotted on a recording system. No other inclusion or exclusion criteria were implemented. After clinical examination, especially with regard to the denture, a fi rst recording was performed on the awake patient in the preparation room. After transfer to the bronchoscopy suite and induction of general anesthesia, preoxygenation was performed via nasal mask with the lower arch elevated ( Figure   5). After suffi cient ventilation the lower arch was attached to the dental clutch and the bronchoscope was introduced ( Figure   6). This was not always easy via the midline due to the volume of the CADIAX III system or due to limitations of the mouth opening. Then, the bronchoscope was introduced via the side of the mouth and sometimes it needed several attempts to lift the epiglottis and enter the larynx. After conclusion of the bronchoscopy the patient was transferred to the recovery room Answers were sought to the following questions: -What movements take place in the temporomandibular system during rigid bronchoscopy?
-Are these movements within physiologically normal limits?
-Is there a correlation between the anesthetic process (anesthesia record, degree of relaxation) and the curves traced?
-What is the ratio of translational to rotational components?  and after fully awakening a repeat recording was performed.
Pre-, intra-and post-procedural recordings were analyzed and compared. Normal overall appearance, slightly reduced nutritional condition Graphs 4-7.

Comparison of condylography tracings before and
In the next case the curves were traced during laryngoscopy.
The purpose of this experiment was to identify any differences between bronchoscopy and laryngoscopy. Therefore, no before-after comparison was attempted. For laryngoscopy, the anesthetist advances the instrument to the base of the tongue and raises the fl oor of the mouth to allow inspection of the larynx. Accordingly, the condylar trajectories produced are likely to be different from those seen in association with bronchoscopy. The condylography equipment was set up in the following cases in a manner identical to that already described.

Discussion
Statistical analysis needs to produce results that can be generalized. To this end levels of statistical signifi cance need to be defi ned prior to initiating a study. That was not the intention of the study described in this paper, and in any case would not have been possible in such a small patient population. It made sense, nevertheless, to conduct a case comparison, as the identifi cation of a trend may provide a basis for future statistical analysis in a larger study. The variation of tracings that we found in our patients is very wide compared to normal mandibular movements. The movements traced during rigid