Ramus of the mandible

What parts does the ramus of the mandible consist of?

The ramus is one of the three main parts of the mandible. Topographically, two processes are distinguished on it:

• Coronoid process (Processus coronoideus) — the powerful temporalis muscle attaches to it; its reflex contraction during trauma can lead to detachment of the process.
• Condylar process (Processus condylaris) — participates in the formation of the temporomandibular joint. Upon palpation, the detection of a "bony step" indicates a displaced fracture.

The mandibular foramen is located on the ramus, for which various structural variants have been described, including complete absence or the presence of a bony overhang covering it — the lingula.

Topography and adjacent fascial spaces

The ramus of the mandible is located at an angle to the sagittal plane: its anterior border is closer to the midline, and the posterior border is further away. It serves as a boundary for a number of important anatomical spaces of the face:

• Masseteric-mandibular space (spatium masticatoriomandibulare) — is 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 laterally by a dense layer of compact bone on the inner surface of the ramus.
• Intermandibular fascial space (according to N.I. Pirogov) — the ramus forms its outer wall.

Clinical significance in dentistry (anesthesia)

The inner surface of the ramus is a key landmark for anesthesia of the inferior alveolar and lingual nerves.

• With the apodactylar method, the needle is advanced until it contacts the bone tissue of the ramus to 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 contact. In this case, the syringe is retracted further to the opposite side — to the level of the second molar.
• With P.M. Egorov's method, the ramus is conventionally divided into four quadrants by two intersecting lines. The target point for anesthetic injection is the middle part of the posterior upper quadrant.
• With S.A. Rabinovich's modification, the anesthetic depot is created at the lateral part of the mandibular neck.

Injuries and pathologies of the mandibular ramus

• Fractures: a shear mechanism from a blow directed upward and forward anterior to 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 mandibular body in the angle region over a wide area leads to a transverse fracture of the ramus, most often in its middle third.
• Gunshot wounds: tangential bullet wounds can lead to marginal defects: the outer compact plate is shot away along with the spongy bone. Wounds in the sagittal plane typically damage the ramus, the lateral part of the body, and the angle of the mandible.
• Oncology: the ramus can be involved in the process during the spread of buccal mucosa cancer, which is accompanied by persistent trismus (limitation of jaw opening). For X-ray diagnostics of lesions of the body and ramus, direct and lateral projections are used.

Class and exam questions

What else to study on this topic

• Body of the mandible (Corpus mandibulae)
• Temporomandibular joint (TMJ)
• Pterygomandibular space
• Inferior alveolar nerve (n. alveolaris inferior)

Other topics in the "Anatomical Structures" section

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