Mechanical Analysis of the Effects of Cephalic Trim on Lower Lateral Cartilage Stability

Abstract

Objective To determine how mechanical stability changes in the lower lateral cartilage (LLC) after varying degrees of cephalic resection in a porcine cartilage nasal tip model. Methods Alar cartilage was harvested from fresh porcine crania (n=14) and sectioned to precisely emulate a human LLC in size and dimension. Flexural mechanical analysis was performed both before and after cephalic trims of 0 (control), 4, and 6 mm. Cantilever deformation tests were performed on the LLC models at 3 locations (4, 6, and 8 mm from the midline), and the integrated reaction force was measured. An equivalent elastic modulus of the crura was calculated assuming that the geometry of the LLC model approximated a modified single cantilever beam. A 3-dimensional finite element model was used to model the stress distribution of the prescribed loading conditions for each of the 3 types of LLC widths. Results A statistically significant decrease (P=.02) in the equivalent elastic modulus of the LLC model was noted at the most lateral point at 8 mm and only when 4 mm of the strut remained (P=05). The finite element model revealed that the greatest internal stresses was at the tip of the nose when tissue was flexed 8 mm from the midline. Conclusion Our results provide the mechanical basis for suggested clinical guidelines stating that a residual strut of less than 6 mm can lead to suboptimal cosmetic results owing to poor structural support of the overlying skin soft-tissue envelope by an overly resected LLC.

Lateral Crural Tensioning for Refinement of the Wide and Underprojected Nasal Tip

“…The eventual result is often severe distortion of the nasal tip leading to lobular pinching, alar retraction, bossae formation, asymmetry, excessive tip rotation, unwanted loss of tip projection, and/or symptomatic nasal valve collapse. [1][2][3][4][5][6][7][8][9][10][11][12]20,24,25 Patients with naturally weak tip cartilage are at disproportionally high risk for morbidity after the cephalic trim maneuver because the tip is already at or near the threshold for collapse, and these patients often develop unsightly tip deformities despite comparatively modest cephalic resections. [1][2][3]24 Moreover, tip width does not correlate with cartilage stiffness, and overly pliable, weak tip cartilages are often encountered in ultrawide bulbous noses.…”

“…5). 4,7,11,26 Ironically, severe crural over-resection may not become immediately evident in the thick-skinned nose because postoperative swelling-which is typically more severe and longer lasting in thick nasal skin-may conceal the initial tip deformity for many months. However, as the swelling subsides and the surgically weakened tip framework is subjected to the sustained and potent forces of fibrosis combined with the repetitive inward sidewall flexion generated during nasal inspiration, stigmatic tip deformities and/or functional impairment eventually become evident.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] Although this trend is rapidly spreading among rhinoplasty enthusiasts, the number of failed rhinoplasty outcomes stemming from cartilage overresection seems to be growing rapidly, suggesting that aggressive excisional techniques are still practiced widely even today. 1 Nonetheless, there are now safe and effective alternatives to excisional rhinoplasty in which little if any tip cartilage excision is required.…”

“…Instead, the LCS uses redistribution and/or repositioning of the existing skeletal elements to derive a more attractive, stable, and functional tip configuration. Although a modest amount of cartilage must be excised from the nasal dome when performing an aggressive LCS, cartilage removal is confined to the medialmost aspect of the lateral crus in an area of comparatively minimal structural consequence, 11 thereby preserving virtually all of the naturally derived skeletal support. And, when the traditional LCS is used in combination with a SEG, the LCS/SEG combination-herein referred to as LCT-becomes a far more potent and versatile surgical workhorse for tip refinement.…”

A Patient With Nasal Valve Compromise

“…To prevent this complication, it is now recommended that a minimum of 6 mm of each lateral crus be left following cephalic trim. 6 Facial paralysis, with dysfunction of the dilator muscles of the nose, is another potential cause of ENV compromise.…”