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Sphenomandibular Ligament

ligamentum sphenomandibulare

The sphenomandibular ligament is a lateral accessory ligament of the TMJ, running from the sphenoid spine to the mandibular lingula beside the mandibular foramen. The inferior alveolar nerve and vessels enter the mandibular foramen through the gap between the ligament and the ramus, making the ligament the medial guide for inferior alveolar nerve block injections. The ligament acts as a medial hinge during mouth opening.

Region: Head & Skull

Anatomical Data

Origin, Insertion & Supply

Origin	Spine of the sphenoid bone
Insertion	Lingula of the mandible at the mandibular foramen

Biomechanics

Function & Actions

Actions	Acts as a hinge axis for mandibular depression; guides condylar rotation during mouth opening

Clinical Relevance

Clinical Notes

The inferior alveolar nerve block is directed toward the mandibular foramen guided by the sphenomandibular ligament as the medial border — the needle is walked along the medial ramus to the foramen. Incorrect block technique placing the needle too posterior can lacerate the pterygoid venous plexus deep to the ligament.

Pathology

Common Injuries & Conditions

Inferior Alveolar Nerve Block Complication

Haematoma formation in the pterygoid space behind the sphenomandibular ligament from inadvertent pterygoid plexus penetration during dental nerve block, producing progressive jaw restriction over 24 hours.