S8B-04 SESSION 8B: FACE RESEARCH - PART I ANALYSIS OF DIFFERENTIAL EXCURSION OF THE TEMPORALIS MUSCLE AND TENDON INSERTION ON THE CORONOID PROCESS: IMPLICATIONS IN LABBE PROCEDURE

Abstract

Introduction: Lengthening Temporalis Myoplasty (Labbe procedure) is a one-stage procedure performed for reanimation of the middle third of the face with the ultimate purpose of creating a natural smile. The Temporalis muscle is a broad muscle with multiple tendon slips that coalesce into a single tendon which inserts on the coronoid process. During Labbe procedure, the muscle is detached from its origin and advanced anteriorly and inferiorly to allow reattaching the temporalis muscle tendon to the oral commissure. We hypothesized that the tendinous insertion pattern of anterior and posterior halves of the muscles has implications on the differential excursion of the muscle. Methods: The anatomy and patterns of tendon insertion of four temporalis muscles in 2 fresh cadavers were analyzed. Results: In all dissected specimens, the temporalis muscle tendon inserted on the apex, convex anterior border, concave posterior border, lateral surface, and medial surface of the coronoid process. Posteriorly, the insertion extended to the midpoint of the sigmoid notch (mean of 1.2 cm from the apex of the coronoid process). Anteriorly, the insertion extended onto the anterior border of the ramus (mean of 1.5 cm from the apex of the coronoid process). Laterally, the insertion extended inferiorly to cover a mean surface of 1.8 cm from the apex of the coronoid process. Medially, the anterior half of the tendon inserted on a mean surface of 2 cm while the posterior half inserted on a mean surface of 5 mm from the apex of the coronoid process. The posterior half of the muscle inserted (via the posterior half of the tendon) to the posterior border of the coronoid process, anterior half of the sigmoid notch, and the most superior 5 mm of the medial surface while the anterior half of the muscle inserted (via the anterior half of the tendon) onto the apex, anterior border of the coronoid process, the most superior 1.5 cm of the anterior border of the ramus, and the most superior 2 cm of the medial surface. When traction was individually applied to the posterior and anterior halves, the excursion appeared confined to the respective half of the tendon inserting the muscle part subject to traction. Conclusion: In Labbe procedure, the posterior half of the muscle is placed under optimal tension and it is the part that provides the majority of the excursion. Inclusion of the posterior half of the temporalis tendon when suturing the tendon to the oral commissure is crucial to ensure optimal excursion of the temporalis muscle during Labbe procedure. Knowing the topography and pattern of tendon insertion permits achieving this goal.