Mechanical Effects of Down Fracture in Le Fort osteotomy on the Skull Base

Transcription

1 J Meikai Dent Med 46 1, 55 63, Le Fort Victor Jose KITANO FLORES Le Fort Le Fort Le Fort Le Fort 2 7 Le Fort Le Fort Mechanical Effects of Down Fracture in Le Fort osteotomy on the Skull Base Takuya SONOKAWA, Ryuhei AOKI, Hiroyuki TOYOTA, Yoshimichi URA, Yoko OHYAMA, Shoko KAWAGUCHI, Victor Jose KITANO FLORES and Jun SHIMADA Division of Oral and Maxillofacial Surgery, Department of Diagnostics and Therapeutic Sciences, Meikai University School of Dentistry Abstract : Le Fort I osteotomy has been widely performed in the treatment of jaw deformity. However, complications caused by Le Fort I osteotomy have been frequently reported, and cases of serious complications, of not only decrease in vision, but also impairment of visual function including oculogyration, have been reported. This is thought to be due to the stress caused by the separation of the pterygomaxillary sutures, which might cause the sphenoid bone fracturing or bleeding in the cavernous sinus and result in impairment in visual functions ; however, the detailed cause has not been identified. Since the separation of the pterygomaxillary junction might damage the peripheral blood vessels, we can choose a method of performing Le Fort I osteotomy without separation ; however the down fracture cannot be avoided during the surgery. In this experiment, we performed Le Fort I osteotomy, using a dried human skull, and measured the strains caused by the down fracture in the following seven points : the bottoms of the maxillary tuberosity on both sides, the external plates of the sphenoid processus pterygoideus on both sides, the fossa hypophysilis, and two points across the hypophyseal fossa around the sella turcica. Then, we mechanically examined what kind of impact was had on the basis cranii area, comparing before and after the separation of the pterygomaxillary sutures. After the separation of pterygomaxillary junction, distortion was observed on the basis cranii ; thus, it was indicated that the Le Fort I osteotomy

2 down fracture might affect the visual functions. However, if we can separate the pterygomaxillary junction safely and cautiously, we can minimize the impact and reduce the risk of the occurrence of visual dysfunction. Key words : Le Fort osteotomy, visual impairment, down fracture, separation of the pterygomaxillary junction, strains 1 Le Fort Le Fort osteotomy L 2 L Cheever Wassumund 4 Wassumund 1952 Converse Obwegeser 4, 6 L 5, 6 4, 7 L 3 L 4 L L 4, 8 4, 9 L L L L 14 L L1 L1 18

3 L L L L1 L1 L TYPE KFG D17-23L3M2S Fig 1 3 "$ "% "& 45 DB-120-T- 8 CDV-40B EDX-100A DSC-100A 19 Fig 1 The strain gauges were used in the experiment. # $!%$%+(*!$%"%!"$!"% ")(,%$%"$$"%$%"!"$!"&"%$!"%!"&"%# % 57! "$!"& " "$$"% "$! "$#"%!$'#!" 2 KS 900 G 3.5 mm Black&Decker 10 mm L Wassumund 2, mm #700, Commet 5mm 30 mm 20, Fig 2 strain gage cement CC

4 Fig 2 1-A : Extraoral side, It was adhered a strain gauge to the maxillary tuberosity bottom and lamina laterallis both side. 1-B : Intracranial side, It was adhered a strain gauge to fossa hypophysialis, and both side around the fossa hypophysilis. 1-C : It was adhered strain gauge to the side around the fossa hypophysilis. The third axis of the strain gauge which adhered maxillary tuberosity bottom and lamina laterallis is parallel to the horizontal plane, the third axis of the two strain gauges are installed so as to be straight. In the skull base, third axis of each of the strain gauge was placed so as to be parallel to the sagittal plane. All of the strain gauge tip overlapping 3 axes it was placed so as to face the back of the head direction. Fig 3 Fig 3 Diagram, It was allowed to free fall the weight from a height of 1 m in the grip portion of the separator. Skull was fixed to the pedestal after fixing the foramen at immediate curing resin. 3 1m 10 g 1/10 4 0!"!# Fig 4! E

5 59 Fig 5 This figure shows the strains before pterygomaxillary disjunction. Fig 4 An example of the strain was measured. Although the strain when it is changed as shown 3-A is determined to have occurred, when the 3-B was determined that the strain was not occurs.!!!"! 22, GPa 4 1 p 0.05 Fig 5 Fig 6 This figure shows the strains after pterygomaxillary disjunction. 2 p 0.01 p 0.01 p 0.01 Fig 6

6 Table 1 Strains and angle at each measurement point before and after pterygomaxillary disjunction. before pterygomaxillary disjunction after pterygomaxilalry disjunction Strain Angle Strain Angle the right maxillary tuberosity the right lamina laterallis the left maxillary tuberosity the left lamina laterallis the right side around the fossa hypophysilis the fossa hypophysilis the left side around the fossa hypophysilis Strain εmax 10 6 Angle : degree mean S.D. p 0.05 Table 2 This table shows a represents the stress before and after pterygomaxillary disjunction the right side around the fossa hypophysilis the fossa hypophysilis the left side around the fossa hypophysilis before pterygomaxillary disjunction after pterygomaxillary disjunction Stress : kpa 76.4 kpa 382 kpa, 377 kpa Table 2 Fig 7 Comparison before and after pterygomaxillary disjunction. 3 p 0.05 Table 1, Fig GPa 736 kpa 2246 kpa 690 kpa 567 kpa, 563 kpa 4 Berens

7 61 Huelke 27 2 L 28 Huelke L1 Lanigan 9 L1 RED 29 3 Turvey White 4

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