What are the structural parts of the mandibular ramus?
The ramus is one of the three main parts of the mandible. Topographically, it features two distinct processes:
- Coronoid process (Processus coronoideus) — the powerful temporalis muscle attaches here; reflex contraction of this muscle during trauma can lead to an avulsion fracture of the process.
- Condylar process (Processus condylaris) — participates in forming the temporomandibular joint. Palpation revealing a "bony step" indicates a displaced fracture.
Located on the ramus is the mandibular foramen, which exhibits various anatomical variations, such as complete absence or the presence of an overlying bony shelf known as the lingula.
Topography and Adjacent Fascial Spaces
The mandibular ramus is oriented at an angle to the sagittal plane: its anterior border lies closer to the midline, while the posterior border lies further away. It forms the boundary for several important anatomical spaces of the face:
- Masseteric-mandibular space (spatium masticatoriomandibulare) — located between the masseter muscle (m. masseter) and the ramus of the mandible (ramus mandibulae). It contains loose connective tissue, as well as the masseteric artery, vein, and nerve (a., v. et n. massetericae).
- Pterygomandibular space — bounded externally by the dense layer of compact bone on the inner surface of the ramus.
- Intermuscular fascial space — the ramus forms its outer wall.
Clinical Significance in Dentistry (Anesthesia)
The inner surface of the ramus is a key landmark for anesthetizing the inferior alveolar and lingual nerves.
- Using the apodactyl technique, the needle is advanced until it contacts the bone of the ramus at a depth of 1.5–2 cm. If the inclination of the ramus to the sagittal plane is pronounced, the needle may pass parallel to the bone without making contact. In this case, the syringe is shifted further toward the opposite side—to the level of the second molar.
- Using Egorov's method, the ramus is conventionally divided into four quadrants by two intersecting lines. The target point for anesthetic injection is the middle of the posterosuperior quadrant.
- Using Rabinovich's modification, the anesthetic depot is established at the lateral part of the mandibular neck.
Trauma and Pathologies of the Mandibular Ramus
- Fractures: A shear mechanism from a blow directed upward and forward from the angle of the jaw causes a longitudinal fracture of the ramus. A compression mechanism from a blow directed upward against the base of the jaw body in the angle region over a wide area leads to a transverse fracture of the ramus, most commonly in its middle third.
- Gunshot wounds: Tangential bullet wounds can result in marginal bone defects: blowing off the outer compact plate along with the spongy bone. Wounds in the sagittal plane typically damage the ramus, the lateral body, and the angle of the mandible.
- Oncology: The ramus can be involved in the spread of oral squamous cell carcinoma from the buccal mucosa, accompanied by persistent jaw-clenching (trismus). Direct and lateral radiographic projections are used to diagnose lesions of the body and ramus.