Novel Z Technique to Overcome Warping of Costal Cartilage.

Abstract

Rhinoplasty has become one of the most popular operations in recent years and autologous costal cartilage is usually chosen as the graft material in dorsal augmentation. However, the warping tendency of rib cartilage may jeopardize the aesthetic results of rhinoplasty.1,2 Many methods have been proposed to address this problem. The accordion technique is based on the theory that protein polysaccharides—the biomechanical infrastructure of all cartilage—produce interlocking stresses (intrinsic forces) that lead to warping.3 In this procedure, to break the recoil mechanism responsible for warping, transverse cuts were made through 75% of the graft width every 1 to 2 mm along the entire graft length, alternating between its two sides.4 This method has been widely used for dorsal augmentation but has not eliminated the problem; mild warping is still reported. Our group theorizes that this technique eliminates the graft’s intrinsic warping forces but increases the graft’s pliability and therefore the likelihood of distortion when an external force is applied. When grafts are implanted for dorsal augmentation, the following conditions will occur. First, although the costal cartilage is carved to match the shape of the nasal bone, a small space will exist between graft and bone, allowing a slight displacement of grafts. Second, the length of the dorsal graft (~4 cm) increases the rate of external forces, including gravity, inspiratory and expiratory forces, and asymmetric facial muscle activity. Third, the caudal end of the graft is fixed firmly to the nasal tip cartilage framework, but the cephalic end is only loosely placed under the periosteum; this makes the graft susceptible to deformation when it undergoes external forces. Therefore, the graft’s pliability magnifies the effect of external forces and contributes to the warp of dorsal graft. A good prefabricated technique to decrease the risk of warping should not only eliminate intrinsic warping forces but also decrease the deforming effect of external forces. To achieve this, the authors combined the principles of the oblique split technique and accordion technique to create a new Z technique for nose dorsal augmentation. Different from the accordion technique, oblique cuts (45 degrees to the longitudinal axis) were made along the graft length every 4 mm, with alternate short (5.5 mm) and long incisions (10.0 mm) made on the two sides (Fig. 1). The warping angles and biomechanical test of the Z technique were compared with the accordion technique in an in vitro study. The results indicated that by changing the cutting direction and the angle of the incision to the longitudinal axis, not only were the intrinsic warping forces eliminated, but also every part of the operated graft was antagonistic to each other so that the pliability and effects of external forces were decreased.Fig. 1.: Accordion technique and Z technique. The grafts were incised along the length of the graft; the spacing between two adjacent cuts is about 4 mm in both techniques. The cuts are 90 degrees to the long axis in the accordion technique and 45 degrees to the long axis in the Z technique.Although further in vivo studies should be performed, the novel Z technique is a simple and reliable procedure to overcome the problem of costal cartilage warping after dorsal augmentation in rhinoplasty. ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (grant 82072182) and the Shaanxi Province Key R&D Program Project, China (grant 2020SF-179). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the article. DISCLOSURE The authors declare that they have no competing interests.