ANATOMY OF TMJSURGICAL PART

BY- DR. DHAVAL TRIVEDI

RELATIONSAnteriorly - Mandibular notch Lateral pterygoid Masseteric nerve and artery

The location of the masseteric artery was then determined in relation to 3 points process:

1) the anterior-superior aspect of the condylar neck = 10.3 mm;

2) the most inferior aspect of the articular tubercle = 11.4 mm;

3) the inferior aspect of the sigmoid notch = 3 mm

Posteriorly - parotid gland Superficial temporal vessels Auriculotemporal nerve

Laterally – Skin and fascia Parotid gland Temporal branches of facial nerve

Medially - Tympanic plate (separates from ICA) spine of sphenoid Auriculotemporal & chorda tympani nerve middle meningeal arterymaxillary artery

Facial nerveTo locate the facial nerve, an incision is made just in front

of the tragus of the ear from the root of the zygoma to the angle of the jaw. Here the incision is carried forward about one finger breadth below the ramus of the mandible as far as is necessary to obtain adequate exposure.

The incision is carried down through skin and subcutaneous tissue to the cartilage bounding the anterior extremity of the external auditory canal. Then, with blunt dissection, the cartilage of the external auditory canal is separated from the capsule of the parotid gland as far & medially as is possible or until a firm bony resistance is met.

This is the base of the styloid process and is encountered at a depth of about 1.5 inches (4 em.) from the skin incision. It is important to remember to stay high just under the root of the zygoma, so that the base of the styloid process is the first important structure to be identified.

With finger dissection and palpation, the styloid process can next be identified immediately below its base; a good headlight and a dry field greatly facilitate this stage of the operation.

With gentle traction on the capsule of the parotid gland anteriorly, the facial nerve is brought into view, emerging from the medial aspect of the styloid process and coursing sharply upward and laterally to enter immediately the capsule of the parotid gland.

The nerve usually is heavily invested in fascia and a.ccompanied by the stylomastoid artery that may prove troublesome if severed.

TheThe length of the facial nerve which is visible to the surgeon is about 1.3 cm.

The distance from the most anterior concavity of the bony external auditory canal to the most posterior significant temporal branch of the facial nerve was measured, with a mean of 2.0 * 0.5 cm and a range of 0.8 to 3.5 cm.

The mean distance from the bifurcation of the main trunk of the facial nerve to the lowest concavity of the external auditory canal was 2.3 *0.28 cm, with a range of 1.5 to 2.8 cm.

The mean distance from the bifurcation of the facial nerve to the postglenoid tubercle was 3.0 + 0.31 cm, with a range of 2.4 to 3.5 cm.

mean distance from most posterior ramus of the temporal branch of the facial nerve to the most anterior aspect of the external acoustic canal is 2.12 cm ± 0.21 cm (range, 1.68 to 2.49 cm).

Knowledge of the distances and the range of the facial nerve branches from fixed bony landmarks within the surgical field alerts the surgeon to the areas of highest risk