Thursday, January 6, 2011

Introduction to M-Arch model and Tripod theory application for the nasal tip

The M-Arch Model: A New Concept of Nasal Tip Dynamics
Adamson, P.A., Litner, J.A., Dahiya, R. | Arch Facial Plast Surg | vol. 8, 16 - 25, 2006 

Of the many techniques for addressing the nasal tip, the tripod concept of nasal tip dynamics is one that has stood the test of time. This concept defines the conjoined medial crura as 1 leg of a tripod and each lateral crura as the other legs. The lengths of these legs can be adjusted to alter the tip position. The M-Arch model extends this concept to think of the tripod as an arch with a specific length that can be manipulated anywhere within the arch. Thus, length, projection, rotation, and lobule refinement can be achieved through technical maneuvers performed in a graduated and integrated approach. The M-Arch model also defines the domal arch, a lobular-arch consisting of the intermediate crura and anterior component of the lower lateral crus. A key component in making changes in length, projection, rotation, and lobule refinement is vertical division, specifically, making an incision in the tripod arch that is perpendicular to the long axis of the arch. Vertical divisions can also be used to alter columellar, lobular, and lower lateral crural deformities and change the position of the tip-defining point.

The M-Arch model can be used to change tip projection. Increased tip projection is achieved by increasing tripod arch length anteriorly. Decreased tip projection is achieved by performing a vertical arch division and/or excision at the medial and lateral crural feet. The relative effect on projection and rotation is determined by the placement of the vertical lobule division. Counter-rotation of the tip-defining point occurs when the medial crura are shortened more than the lateral crura. If the reverse is performed, rotation is produced. Rotation shortens the nose; counterrotation lengthens it. With respect to lobule definition, vertical lobular division in the intermediate crus can be a significant tool to address deprojection, rotation, and lobular refinement. It is also useful in diminishing a hanging infratip lobule, narrowing a broad biconvex domal arch, and improving nostril-lobular relationship when the infratip lobule height is relatively large. Various other uses are possible. Ultimately, using the M-Arch model helps the surgeon produce the desired esthetically pleasing nasal tip.

Rhinoplasty, Tripod Theory

Author: Anil P Punjabi, DDS, MD


Surgically manipulating the nasal tip to achieve predictable results is the most difficult feature of rhinoplasty. One who can control the nasal tip is said to be able to master rhinoplasty. Anderson first proposed the rhinoplasty tripod theory. A complete comprehension of the tripod theory and the dynamics of tip projection, support, and rotation allow categorization of the different factors that may need alteration to manipulate the nasal tip.
Rhinoplasty is technically demanding, and tip surgery is an art form. It requires an in-depth knowledge of the complex three-dimensional anatomy of the nose, a complete understanding of its physiology, familiarity with the described techniques of nasal tip surgery, and a well-developed sense of aesthetics; all are essential in mastering rhinoplasty.

The Tripod Theory
The tripod concept of tip projection, support, and rotation described by Anderson provides an understanding of the dynamics of tip rhinoplasty. The anatomy of the two alar cartilages forms a functional tripod that provides tip support. The right and left lateral crura comprise two legs of the tripod, and two conjoined medial crura function as the third leg. Anatomically, the medial crura are shorter than the lateral crura. The medial crural foundation is supported by the attachments to the superior and inferior septum.

Incisions between the upper and lower lateral cartilages (ie, intercartilaginous incisions) and removal of the cephalic border of the lateral crura disrupts the interlocking relationship of the upper and lower lateral cartilages. The length, strength, and shape of each lateral crura produces a torque that pushes the lobular tip of the nose toward the upper lip and away from the peripheral aperture.

Nasal tip support system 

Dr. T.Balu

 The nasal tip tripod is considered to be a dynamic unit suspended and supported by surrounding rigid structures. Other major nasal tip supports include:

  1. The attachment of medial crural feet to the caudal end of quadrangular cartilage
  2. Scroll like attachment of the caudal end of upper lateral cartilage to the cephalic margin of the lateral crura

     According to Tardy there are three major and six minor support mechanisms of nasal tip.

Tardy’s major support mechanisms include:
  1. Size, shape, strength and resilience of medial and lateral crura
  2. Attachment of medial crural foot plate to the caudal border of quadrangular cartilage
  3. Attachment of upper lateral cartilages (caudal border) to alar cartilages (cephalic border).
Janeke and Wright nasal tip support hypothesis:
This hypothesis proposes that fibrous connection between the upper and lower lateral cartilages play a vital role in the nasal tip support mechanism. This is in addition to the support structures suggested by Tardy. According to Wright this fibrous connection between the upper and lower lateral cartilages play a vital role in determining the nasal tip tripod structure.

 Click on Illustrations for larger view and explanation 

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