Tsuyoshi Kaneko

Finite element analysis of the stresses around fixtures in various reconstructed mandibular models–Part II (effect of horizontal load)

UNLABELLED AIM OF EXPERIMENT: Having already studied the effect of vertical load (Nagasao et al., 2002), the purpose of this study was to investigate the effect of horizontal load on implants embedded into a virtually reconstructed mandible. MATERIAL AND METHODS Three-dimensional virtual models of various reconstructed mandibles were designed on a PC and 50 N horizontal loads were applied on the cantilever portion of the upper structure. Then, using a finite element analysis, stresses occurring around the implants were calculated, and the directions of the forces that cause the maximum von Mises stresses were evaluated. Finally, the results were compared with those from vertical loading. RESULTS In all models, the maximum stresses occurred around the implants embedded on the premolar region of the loaded side. In addition, the locations at which the maximum von Mises stresses occurred were greatly influenced by the structural character of the loaded side. CONCLUSION When horizontal loads were applied to reconstructed mandibles, the location and direction of the maximum stresses around the dental implants appeared to be influenced much more by the structural characters of the reconstructed mandibles when compared with vertical loads.

Gastric tube-to-tracheal fistula closed with a latissimus dorsi myocutaneous flap

A gastric tube-to-airway fistula is a very rare complication after esophageal reconstruction. A patient with a gastric tube-to-tracheal fistula that developed more than 9 years after surgery for cancer of the cervical esophagus was treated with transposition of a pedicled latissimus dorsi myocutaneous flap. Careful perioperative respiratory management helped save the patients life.

Interaction of hydraulic and buckling mechanisms in blowout fractures.

The etiology of blowout fractures is generally attributed to 2 mechanisms—increase in the pressure of the orbital contents (the hydraulic mechanism) and direct transmission of impacts on the orbital walls (the buckling mechanism). The present study aims to elucidate whether or not an interaction exists between these 2 mechanisms. We performed a simulation experiment using 10 Computer-Aided-Design skull models. We applied destructive energy to the orbits of the 10 models in 3 different ways. First, to simulate pure hydraulic mechanism, energy was applied solely on the internal walls of the orbit. Second, to simulate pure buckling mechanism, energy was applied solely on the inferior rim of the orbit. Third, to simulate the combined effect of the hydraulic and buckling mechanisms, energy was applied both on the internal wall of the orbit and inferior rim of the orbit. After applying the energy, we calculated the areas of the regions where fracture occurred in the models. Thereafter, we compared the areas among the 3 energy application patterns. When the hydraulic and buckling mechanisms work simultaneously, fracture occurs on wider areas of the orbital walls than when each of these mechanisms works separately. The hydraulic and buckling mechanisms interact, enhancing each others effect. This information should be taken into consideration when we examine patients in whom blowout fracture is suspected.

Effectiveness of additional transmalar Kirschner wire fixation for a zygoma fracture

Background: The purpose of this study was to verify the effectiveness of transmalar Kirschner wire fixation as additional fixation for the treatment of zygoma fractures. Methods: The authors compared two methods for zygoma fixation at the frontozygomatic suture from both theoretical and clinical viewpoints: miniplate fixation (plate fixation) and miniplate fixation with an additional transmalar Kirschner wire fixation (wire plus plate fixation). For the theoretical study, the authors produced zygoma fractures on 20 skull simulation models; these were generated on the basis of computed tomographic data of actual dry skulls. In their simulation surgery, they fixed the fractured zygoma with the above-mentioned two fixation methods, producing 20 plate fixation models and 20 wire plus plate fixation models. A 10-kgf load was then applied on the fractured zygoma in the anteroposterior and superoinferior directions. Finally, the stresses around the fixation screws and the deviation of the zygoma were calculated using finite element analysis. For the clinical study, the authors compared the postoperative zygoma alignment based on computed tomography of six patients treated with plate fixation and eight patients treated with wire plus plate fixation using a visual analogue scale. Results: In the theoretical study, the wire plus plate fixation models demonstrated a significant decrease in both the stresses around the screws and the deviation of the fractured bone compared with the plate fixation models. In the clinical study, the visual analogue scale scores for the wire plus plate fixation group were significantly higher than those for the plate fixation group. Conclusion: Because the additional transmalar Kirschner wire fixation can effectively increase the stability of the fractured zygoma that has been fixed with one miniplate, it should be recommended as an effective technique for the treatment of complicated zygoma fractures.

Surgical creation of a Cupid's bow using W-plasty in patients after cleft lip surgery

The three-dimensional contour of the Cupids bow is extremely important from a cosmetic standpoint, and many patients with bilateral or unilateral cleft lip require revision or reconstruction of the Cupids bow.A number of surgical techniques have been reported for creating the Cupids bow, among which the methods of Gillies and Onizuka are the most widely known. In the methods of Gillies and Onizuka, the dog-ear can result in excessive volume in the vermilion notch, raising the trough in the Cupids bow and leading to regression during the post-surgical period. We have improved upon these techniques using the W-plasty and have obtained satisfactory results that preserve the white skin roll. In our method, the left and right prominence of the Cupids bow is created through an incision of the white lip, while the central trough is created through a curvilinear incision of the vermilion mucosa. At the two sites of the white lip tissue and the curvilinear incision of the central vermilion tissue, the white skin roll is preserved as much as possible. In patients where the Gillies method had been used, the Cupids bow tended to be flattened gradually after surgery. We report on the details of our method and the case reports using the technique.

Reconstruction of the Total Cheek Defect by Free Myocutaneous Flap

Our reconstructive method utilizing the free latissimus dorsi myocutaneous flap by microneurovascular anastomosis is a rewarding method for the patient with total cheek defect after cancer surgery of the maxillary sinus from the standpoint of morphology, function, and psychology.