**6. Anatomical aspects for modified Jorgensen - Hayden technique**

A thorough knowledge of the anatomy of the pterygomandibular space is essential for the successful administration of the inferior alveolar nerve block. Anesthetic solutions deposited low in the pterygomandibular space will not diffuse up to where the inferior mandibular nerve enters the mandibular canal. In addition to the neural aspects of the pterygomandibular space, there are vascular pathways, fibrous tissue elements, muscular structures, and glandular tissue that need to be considered to improve the predictability, effectiveness, and safety of block anesthesia. Greater understanding of the nature and extent of variation in intraoral landmarks and underlying structures should lead to improved success rates, and provide safer and more effective IAN anesthesia.

**Pterygomandibular space:** The pterygomandibular space is a small fascial-lined cleft contain‐ ing mostly loose connective tissue. [17] It is bounded medially and inferiorly by the medial pterygoid muscle and laterally by the medial surface of the mandibular ramus. Posteriorly, the parotid gland curves medially around the posterior border of the mandibular ramus to form a posterior boundary of the space, whereas anteriorly, the buccinator and superior constrictor muscles come together to form a fibrous junction, the pterygomandibular raphe. Important structures are positioned in this space: the inferior alveolar nerve (IAN), the inferior alveolar artery (IAA), inferior alveolar vein (IAV), lingual nerve (LN), mylohyoid nerve and the sphenomandibular ligament.

**Pterygomandibular raphe**: The pterygomandibular raphe (pterygomandibular ligament) is a ligamentous band of the buccopharyngeal fascia, attached superiorly to medial pterygoid plate, and inferiorly to the posterior end of the mylohyoid line of the mandible (Figure 1). It is formed by the junction of the buccinators muscle and pharynx superior constrictor muscle. [16]

#### **Figure 1.** Pterygomandibular raphe location.

**Coronoid fossa/notch**: The coronoid fossa/notch is the region of greatest concavity of the anterior border of the ramus of the mandible (Figure 2). [1]

**Temporal crest:** The temporal crest is an extension of the coronoid process, which ends in the retromolar area. [18] An extremely important technical aspect is that on the temporal crest the deep temporal muscle tendon is inserted (Figure 3).

**Sphenomandibular ligament:** The sphenomandibular ligament is a flat, thin band which is attached superiorly to the spine of the sphenoid bone, and, becoming broader as it descends, is fixed to the lingula of the mandibular foramen. [19] The sphenomandibular ligament has a very important influence on the diffusion of anesthetic solution injected into the area.

**Figure 3.** Temporal crest location.

**Figure 1.** Pterygomandibular raphe location.

48 A Textbook of Advanced Oral and Maxillofacial Surgery Volume 2

**Figure 2.** Coronoid fossa location.

deep temporal muscle tendon is inserted (Figure 3).

anterior border of the ramus of the mandible (Figure 2). [1]

**Coronoid fossa/notch**: The coronoid fossa/notch is the region of greatest concavity of the

**Temporal crest:** The temporal crest is an extension of the coronoid process, which ends in the retromolar area. [18] An extremely important technical aspect is that on the temporal crest the

**Sphenomandibular ligament:** The sphenomandibular ligament is a flat, thin band which is attached superiorly to the spine of the sphenoid bone, and, becoming broader as it descends, is fixed to the lingula of the mandibular foramen. [19] The sphenomandibular ligament has a

very important influence on the diffusion of anesthetic solution injected into the area.

**Mandibular foramen:** In the center of the medial ramus of the jaw there is a large hole, the foramen of the mandible, which continues inside with the mandibular canal. Serve as a passage way to IAN, IAA and IAV (Figure 4). [18]

**Mandibular lingula and mandibular groove:** The margin of the mandibular foramen is irregular; presented in front of a prominent ridge, topped by a sharp spine, the mandibular lingula, which gives attachment to sphenomandibular ligament; at its lower and back part there is a notch from which the mylohyoid groove runs obliquely downward and forward, and allocates the vessels and mylohyoid nerve (Figure 5). [19]

**Occlusal plane:** In 1972 Jorgensen and Hayden [16] reported that if we could trace a line parallel to the occlusal plane, passing through the center of the coronoid fossa, we could reach

**Figure 5.** Mandibular lingula position.

a point immediately above the mandibular foramen. According to the literature, a needle inserted 5 mm above the occlusal plane and parallel to it would lie above the lingula in 64% of mandibles and below it in 36%. A needle placed 11 mm above the occlusal plane would be above the lingula in 96% of mandibles. [20]

**Contralateral premolars:** The premolars on the opposite side of injection are used to help direct the syringe (Figure 6).

**Figure 6.** Position of the syringe in relation to the opposite premolar teeth.
