so, it should prevent excessive upward rotation of the mandible (Burch 1970), which sometimes causes problems in patients with a significantly reduced vertical dimension.
Stylomandibular ligament
66 Situation with jaws closed
Lateral view of a macroscopic anatomical preparation approximating the habitual condylar position. The ligament runs from the styloid process (1) to the posterior border of the angle of the jaw. In this mandibular position the ligament (arrows) is essentially free of tension. Chronic nonphysiological loading (Fig. 68) can lead to insertion tendinosis (Ernest syndrome; Brown 1996).
67 Situation during rotational jaw opening
Preparation shown in Figure 66 after the initial opening rotation. Rotational movement of the condyle against the articular protuberance causes a relaxation of the ligament (arrows). With further rotational opening, the angle of the jaw would swing farther posteriorly and allow even more slack in the ligament.
68 Situation during translation
Same preparation following anterior translation (= protrusion). Anterior translational movements in the temporomandibular joint always increase tension in the ligament (arrows). This helps to protect more sensitive structures (such as the superior stratum) from overextension during protrusion. Excessive closing rotation of edentulous jaws can likewise produce tension in the ligament.
The sphenomandibular ligament has its sole origin on the sphenoidal spine in only about one-third of patients (Burch 1966). In the majority of individuals it also inserts into the medial wall of the joint capsule, in the petrotympanic fissure or on the anterior ligament of malleus (Cameron 1915, Loughner et al. 1989, Schmolke 1994). By means of its insertion on the lingula of the mandible, the sphenomandibular ligament limits protrusive and mediotrusive movement (Langton and Eggleton 1992) as well as passive jaw opening (Hesse and Hansson 1988, Osborn 1989). The importance of the sphenomandibular ligament to the physiology of movement is negligible in comparison with the previously described ligaments (Williams et al. 1989), as is confirmed by the lack of related clinical symptoms.
The discomalleolar ligament (= Pinto’s ligament) was described by Pinto (1962) as a connection between the malleus and the medial wall of the joint capsule. However, a separate ligament can be demonstrated here in only 29% of temporomandibular joints (Loughner et al. 1989).
Tanaka’s ligament represents a cord-like reinforcement of the medial capsule wall, similar to the lateral ligament (Tanaka 1986.1988).
Sphenomandibular ligament
69 Situation at the habitual condylar position
Macroscopic anatomical preparation displaying the left sphenomandibular ligament from the medial. The ligament runs from the spine on the underside of the sphenoid bone (spina ossis sphenoidalis) to the lingula of the mandible (Rodriguez-Vazquez et al. 1992). With the jaws in this position the ligament (arrows) is essentially relaxed. Besides the ligament, a section of the lateral pterygoid muscle can be seen.
70 Situation during opening rotation
Same preparation after opening rotation. As long as the condlye is rotating against the articular protuberance without leaving the fossa, the ligament (arrows) becomes progressively more relaxed. Only after translation begins does the ligament re-acquire the same degree of tension it had when the jaws were closed.
71 Situation during translation
Macroscopic anatomical preparation after anterior translation (= protrusion). In synergy with the stylomandibular ligament, tension in this ligament is increased as translation progresses. The stylomandibular and sphenomandibular ligaments together restrain protrusive and mediotrusive movements. If a pain-producing lesion in one of these ligaments is suspected, passive movements must be used to test the ligaments.
Arterial Supply and Sensory Innervation of the Temporomandibular Joint
The arterial blood supply of the temporomandibular joint is provided primarily by the maxillary artery and the superficial temporal artery (Boyer et al. 1964). Both of these arteries are also the principle supply for the muscles of mastication. Apart from the network of arteries surrounding it, the condyle is also supplied from the inferior alveolar artery through the bone marrow (Okeson 1998). The venous drainage is through the superficial temporal vein, the maxillary plexus, and the pterygoid plexus.
The sensory innervation of the joint capsule and its receptors has already been addressed briefly on page 27. The temporomandibular joint is innervated predominantly by the auriculotemporal, masseter, and temporal nerves (Klineberg et al. 1970, Harris and Griffin 1975). Proprioception occurs through four types of receptors (Thilander 1961, Clark and Wyke 1974, Zimny 1988): Ruffini mechanoreceptors(type I), pacinian corpuscles (type II), Golgi tendon organs (type III), and free nerve endings (type IV). These receptors are located in the joint capsule, the lateral ligament, and in the bilaminar zone and its genu vasculosum. The anteromedial portion of the capsule contains relatively few pain receptors, of type IV (Thilander 1961).
72 Arterial supply
Diagram of the arterial blood supply of a left temporomandibular joint (modified after Voy and Fuchs 1980). The condyle is supplied with blood from all four sides. In addition, there are anastomoses with the inferior alveolar artery within the marrow spaces. Because of the abundant blood supply, avascular necrosis is rarely found in the condyle (Hatcher et al. 1997). Compression of the anterior vessels by anterior disk displacement (Schell-has et al. 1992) will not interfere with the condyle’s blood supply.
73 Sensory innervation of a left temporomandibular joint
The afferent nerve fibers arise from the mandibular branch of the trigeminal nerve and exhibit four types of nerve endings. In rats, fret nerve endings (type IV), which are potential pain receptors, have beer found in the capsule, lateral ligament, bilaminar zone, and in the pars anterior and pars posterior o the disk (Ichikawa et al. 1990, Kido et al. 1991). This has not been verified for human disk structures however.
74 Innervation in the capsule region
Schematic diagram of the different areas of innervation (modified from Ishibashi 1974, Schwarzer 1993) Activation of the type-IV receptor in the capsule increases the activity of sympathetic efferent fiber (Roberts and Elardo 1985). Because
