Table 1.
Engineering data.
Fig 1.
A. Schematic diagram of the L-strut on the nasal septum in sagittal view. B. Point 1 is the location of pressure application. Point 2 is the inner corner of the L-strut. Point 3 is the contact region between the maxillary crest and the caudal septal L-strut.
Fig 2.
Assumptions for the L-strut condition.
A. External pressure (0.01N) was applied to the dorsal L-strut in a vertical direction from the rhinion (location 1) to the supratip breakpoint (location 9) at a 2-mm distance. The load was exerted in the 2-mm-wide dorsal segment. The location 9 load condition is the region of the superior point of the L-strut inner corner. B. Fixation area 1 is the bonding area with the perpendicular plate of the ethmoid bone (PPE) in the dorsal L-strut. Fixation area 2 is the bonding area with the maxillary crest. The contact percentage in fixation area 2 was assumed to range from 100% to 20%. The 100% condition of fixation area 2 was when the intact 1-cm-wide caudal strut was in contact with the maxillary crest. This simulation was based on partial resection of the caudal septal segment posterior of the anterior nasal spine (ANS) during actual septorhinoplasty. C. The 20% condition of fixation area 2 was the 2-mm-wide caudal strut in contact with the maxillary bone posterior to the ANS.
Fig 3.
Red and blue indicate the highest and lowest stresses, respectively. Relatively high stress occurred at point 1 (applied load), point 2 (L-strut inner corner), and point 3 (contact between maxillary bone and the L-strut). Increased stress on the L-strut occurred as the location of the applied load moved caudally (supratip breakpoint) and the contact percentage decreased. A. Stress distribution according to the location of the applied load. As the applied load increased near the supratip breakpoint, the stress value increased at point 2 and around point 2. B. The stress distribution according to the contact percentage between the L-strut and the maxillary crest. Increased stress occurred in the caudal segment between points 2 and 3 as the contact percentage decreased.
Fig 4.
Maximum stress at each point in the L-strut.
A. The stress was constant at point 1 (pressure exertion region), regardless of the applied load location and the contact percentage with the maxillary crest. B. Stress at point 2 decreased gradually after an initial increase, according to changes in the applied load caudally from the rhinion. In particular, the maximum L-strut stress occurred at point 2 under the location 5 and 6 load conditions, regardless of changes in contact percentage. C. The stress at point 3 increased when the location of the applied load was changed from the rhinion to the supratip breakpoint.
Fig 5.
Maximum stress values between stress applied at points 2 and 3 according to the location of the applied load and the contact percentage with the maxillary bone.
A. Three-dimensional graph. B. Two-dimensional graph. Stress values increased gradually as the applied load moved closer to the caudal position. The larger stress values at points 2 and 3 occurred under the location 6–9 load conditions. Stress on the L-strut was dependent on the contact percentage. Stress increased steadily at the later transition point and increased rapidly with contact percentages of 45–20%. Stress values, particularly those under the location 6–9 load conditions, increased rapidly in the 45–20% contact range. Moreover, the maximal L-strut stress values at points 2 and 3 were 2.5-fold larger than that of the applied load.
Fig 6.
An explanation of displacement at point 2 (L-strut inner corner).
The difference in the point 2 location was measured in the Z-axis direction before and after a load was applied to the dorsal L-strut.
Fig 7.
A. Displacement values at point 2 rose steadily under the caudal load condition; maximum displacement occurred under the location 8 and 9 load conditions. B. Displacement increased as contact percentage decreased, showing rapid displacement in the 45–20% contact range.
Fig 8.
Results for 100% contact between the caudal L-strut and the maxillary crest.
A. Stress at points 2 and 3 based on the applied load location. Maximum stress occurred at point 3 under the location 8 and 9 loading conditions; stress values at point 2 were higher than those at point 3, with the highest values seen under the location 7 loading condition. B. Displacement at point 2 according to the applied load location. As the applied load location changed from location 1 to location 9 (from the rhinion caudally), displacement increased, and maximum values were seen under the location 8 and 9 load conditions (supratip breakpoint).