Lateral Crural Steal Procedure in Rhinoplasty: The Maths Behind

Lateral Crural Steal Procedure in Rhinoplasty: The Maths Behind

Ali Riza Oreroglu MD, Baris Cakir MD, Mithat Akan MD

Goals/Purpose: Surgical control of tip rotation and projection are among the most difficult steps in aesthetic and functional rhinoplasty. Maintenance of tip projection without the control of tip rotation is useless and will result in an unsuccessful operation. Various techniques are used for manipulation of tip projection and rotation. The overall result however lies in the experience of the surgeon and which technique he uses to control the tip position.

The lateral crural steal procedure is a technique used for repositioning the dome and control of the medial-to-lateral crus ratio without any lower lateral cartilage division. The lateral crus is advanced onto the medial crus, increasing the length of the medial crus at the expense of the lateral crus. However, it is not so popular due to difficult manipulation of the cartilage and the less predictable result it may have on both the tip projection and rotation. Identifying the new dome position is the most critical step in the lateral crural steal procedure, making it a technique difficult to learn.

The lateral crural steal procedure is a non-destructive technique that not only balances the ratio between the medial and lateral crura, but also has the effect of increasing tip rotation and projection up to a limit. Tip projection increases with every steal from the lateral crus and reaches a peak value after which starts to decrease. The amount of lateral crus to be advanced to obtain the maximum tip projection and the amount to be advanced to obtain the ideal tip projection and rotation are critical values difficult to predict even during surgery.

Our study aims to objectively define the effects of the lateral crural steal procedure on nasal tip projection and rotation and provide the surgeon a preoperative solid idea of the amount of lateral crus length that is needed to be advanced to the medial crus to achieve the required nasal tip projection and rotation.

Methods/Technique: We hereby present the position of the lower lateral cartilage dome in terms of a geometrical ellipse, and define the tip projection as a function of tip rotation and hence calculate tip projection and rotation for every millimeter steal from the lateral crus. To make this calculation universal, the position of the lower lateral cartilage is defined in terms of its beginning and ending points, i.e. the nasal aperture and footplate, hence the effect of steal from the lateral crus on the tip projection and rotation can be calculated for the lower lateral cartilage of any length and position. This mathematical model is formulated as a computer program that can facilitate calculation and give the surgeon a prediction of the effect the steal procedure will create before surgery.

The length of the lower lateral cartilage is measured preoperatively in the lateral nasal view, identifying the lengths of the medial and lateral crura and the horizontal and vertical distances from the nasal aperture to the footplate. These data are entered in the program, which calculates the increase in projection and rotation for every millimeter advancement of the lateral crus to the medial crus, based on the ellipse model.

Results/Complications: The program has been used by three aesthetic surgeons who reported successful identification of the new dome position with a 1-mm precision tolerance. The calculations confirmed the direct relationship between amount of advancement from the lateral crus to the medial crus and tip rotation; being an average of 10°-15° increase in rotation per millimeter of advancement. The relation between crus advancement and tip projection can be plotted as a graph, showing an increase in tip projection that peaks and then starts to decrease as the advancement is increased. This peak projection is also identified per calculation, which is the amount of crus advancement that provides the maximum tip projection.

Conclusion: There are a few studies comparing the lateral crural steal procedure and other tip modifying techniques however only a few objectively evaluate their effects on tip behavior.

The geometric ellipse model enables understanding of the complex effects of the lateral crus steal procedure on tip rotation and projection. Formulation of the dome position enables prediction of the amount of increase in tip projection and rotation for every millimeter steal from the lateral crus.

Using these calculations, the ideal tip projection and rotation generated by the lateral crural steal procedure can be simulated before the actual advancement is performed hence eliminating use of any other destructive tip modifying technique, such as the dome division procedure and reducing the need for an onlay tip graft.

Preoperative identification of the amount of crus advancement can make use of the lateral crural steal procedure easier to learn and popularize this effective non-destructive technique of tip plasty among aesthetic surgeons.