Junpei Miyamoto

The effect of striking angle on the buckling mechanism in blowout fracture.

Background: The buckling mechanism is widely accepted as a mechanism of blowout fractures, along with the hydraulic mechanism. Although many studies have been performed related to the buckling mechanism, none of them have taken the direction of the striking force into consideration. As the orbital floor is not parallel to the horizontal plane, a difference in the striking force direction might affect resultant fracture patterns. The present study aims to investigate whether fracture patterns in the orbital floor were influenced by the striking force direction in terms of the buckling mechanism. Methods: The authors produced three-dimensional models on a workstation simulating eight dry skulls and applied striking forces on the orbital rim of each model from three different angles (0, 15, and 30 degrees in the upward direction). Using finite element analysis, the authors calculated the width of the area where the resultant stresses exceed the bones yielding criterion. The width was termed the “theoretical fracture width” because, theoretically, fracture was expected to occur in the area. Then, the authors compared the theoretical fracture width in groups with the three different striking force angles. Finally, the validity of the theoretical width was verified with an experiment on actual skull models. Results: The theoretical fracture width was the greatest when the striking force was directed at 30 degrees in the upward direction. Conclusions: For the buckling mechanism, fracture would occur in a wider area of the orbital floor when striking force was directed upward than when the force was horizontally directed. This finding would be helpful in predicting fracture width in blowout fractures.

Evaluation of cleft lip bony depression of piriform margin and nasal deformity with cone beam computed tomography : Retruded-like appearance and anteroposterior position of the alar base

Background: As the nasal platform, the piriform margin is considered the most important nasal structure. An insufficient bony structure has been suggested to be the major factor in secondary nasal deformities such as the “depressed alar base.” It is unclear, however, how the piriform margin is depressed or how bony depression influences nasal shape. Methods: Using cone beam computed tomography, the anteroposterior positions of the cleft-side piriform margin and alar base were compared with those of the noncleft side in 52 postoperative unilateral cleft lip patients with no alveolar bone graft. Patients were divided based on cleft type into either the unilateral cleft lip, alveolus, and palate group or the unilateral cleft lip and alveolus group. Results: In all cases, the cleft-side piriform margin was depressed. The anteroposterior position of the alar base was related to the piriform depression in both groups. However, in contrast with bony depression, the cleft-side alar base was located more anteriorly than the non–cleft-side alar base in 35 of 52 patients. Conclusions: The authors’ study suggests that bony depression does not necessarily lead to postoperative alar depression. The postoperative cleft lip alar position can be maintained independently of the collapsed lesser segment of the maxilla. In addition, in many cleft lip newborns the cleft alar crease is hypoplastic, and the paranasal triangle is easily elevated by operative manipulation because of the muscular dysfunction. This shallowness leads to a “retruded” appearance. For improvement, preservation of the paranasal triangle and alar crease plasty are important.

Double-bar application decreases postoperative pain after the Nuss procedure

OBJECTIVE This biomechanical study aims to elucidate whether additional bar application increases postoperative pain after the Nuss procedure for pectus excavatum. METHODS Clinical evaluation: The intensity of postoperative pain was compared between patients for whom a single-bar was used (single-bar group: n = 14) and those for whom double bars (double-bar group: n = 10) were used to correct the thoracic deformity. The evaluation was performed by referring to the frequency with which local anesthetics were self-injected in a patient-controlled anesthetic system and how many days were needed for the patients to resume ambulation. Theoretical evaluation: An original simulation system for the Nuss procedure was developed by producing 3-dimensional finite element analysis models from computed tomographic data of patients with pectus excavatum. With this system, single-bar and double-bar placement was simulated separately for the thorax models of the double-bar group. The stresses occurring on the thoraces were then compared between the two situations. RESULTS Clinical evaluation: Self-injection of local anesthetic was more frequent for the single-bar group than for the double-bar group; single-bar patients restarted ambulation later than the double-bar group. Theoretical evaluation: Stresses on the thoraces were smaller when double bars were applied than when a single bar was applied. CONCLUSIONS Performing double-bar placement decreases postoperative pain. Therefore, surgeons should not hesitate to perform double-bar correction in patients in whom the deformity extends to multiple intercostal spaces, requiring correction of the thorax shape at multiple sites.

Dynamic effects of the Nuss procedure on the spine in asymmetric pectus excavatum

OBJECTIVE This study aimed to elucidate dynamic effects of the Nuss procedure on the spine in the treatment of patients with pectus excavatum with asymmetric thoraces. METHODS Twenty-five patients with pectus excavatum who underwent the Nuss procedure were categorized into 4 groups by preoperative morphology of the spine and thoracic asymmetry. In group 1 (n = 8), the right side of the thorax was concave and the spine bowed to the right. In group 2 (n = 4), the right side of the thorax was concave and the spine bowed to the left. In group 3 (n = 5), the left side of the thorax was concave and the spine bowed to the right. In group 4 (n = 8), the left side of the thorax was concave and the spine bowed to the left. With computed tomographic data, finite-element models were produced to simulate each patients thorax. Thereafter, dynamic response patterns of the spine to the Nuss procedure were examined. Validity of these biomechanical findings was verified by referring to clinical outcomes. RESULTS In group 1 and group 4 models, deformed spines were straightened; in group 2 and group 3 models, spinal bowing increased. These biomechanical findings were compatible with clinical evaluations. CONCLUSIONS Performance of the Nuss procedure for asymmetric pectus excavatum exerts dynamic influence on the spine. Response patterns of the spine are predictable from morphologic relationships between the asymmetric patterns of the anterior thoracic wall and the spine.

Full-thickness reconstruction of the eyelid with rotation flap based on orbicularis oculi muscle and palatal mucosal graft: Long-term results in 12 cases

BACKGROUND Numerous techniques have been proposed for full-thickness eyelid reconstruction. Previously, we reported full-thickness eyelid reconstruction with a rotation flap based on the orbicularis oculi muscle and palatal mucosal graft. Here, we report long-term results in 12 cases. METHODS After confirmation of defect size, the mucosal defect was covered with a split-thickness palatal mucosal graft. The rotation flap was elevated at the lateral orbital region and the skin defect was covered. Seven cases were reconstructions after tumour excision and five cases were for lagophthalmos after trauma. In cases of tumour excision, five cases had full defects of the lower eyelid and two cases had defect of the lower eyelid lateral to the punctum. In the cases of lagophthalmos, four cases had upper eyelid contracture and one had lower eyelid contracture. RESULTS Postoperatively, one case showed severe venous congestion of the flap, which led to scleral show. In the other 11 cases, there were no complications, and cosmetic results were excellent. CONCLUSIONS With our method, cosmetically good results can be obtained in either upper or lower eyelids. In the rotation flap based on the orbicularis oculi muscle, the undermined area is small, invasion is minimal, and the effects of scar contracture can be minimised. Minimal shrinkage of palatal mucosal grafts prevents the reconstructed eyelid from sagging. In only one case, poor design of the flap led to flap congestion. However, this complication can be avoided with the proper design.

Age-related change of postoperative pain location after Nuss procedure for pectus excavatum

OBJECTIVE The present study aims to evaluate age-related change of postoperative pain after the Nuss procedure by referring to clinical cases, and to elucidate the biomechanical aetiology of the change by using the finite element method. METHODS Twelve paediatric patients (paediatric group: 9.4+/-2.3 years old) and 13 adult patients (adult group: 26.3+/-5.5 years old) who received the Nuss procedure for pectus excavatum were included in the study. On the second postoperative day, the patients were asked to indicate regions on the thorax where they felt the greatest pain. The locations of these regions were compared between the two groups. In addition, stress-distribution patterns were examined using finite element models produced by simulating the thoraces of the patients. The stress-distribution patterns were compared between the two groups. RESULTS The patients of the paediatric group and adult group tend to have pain on the anterior and posterior regions of the thorax, respectively. The finite element study revealed that paediatric thoraces and adult thoraces develop intensified stresses in the anterior region and the posterior region, respectively. CONCLUSION Postoperative pain tends to occur in the anterior part of the thorax for paediatric patients and in the posterior part of the thorax for adult patients, reflecting the stress distributions of these two distinct patient populations.

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.

An anatomical study of the three-dimensional structure of the nasal septum in patients with alveolar clefts and alveolar-palatal clefts.

Background: The present study was performed to quantitatively analyze the three-dimensional morphology of the nasal septa of patients with alveolar and alveolopalatal clefts. Methods: Twenty-five unilateral complete cleft lip patients with alveolar clefts only (alveolar cleft group) and 35 unilateral complete cleft lip patients with alveolar and palatal clefts (alveolar and palatal cleft group) were included in the study. Although no patient in either group had undergone alveoloplasty, all patients had undergone palatoplasty. The degree of nasal septum deviation was studied for each patient at three different depths along the anteroposterior axis using three-dimensional computed tomographic data; the data were compared between the two groups to elucidate whether the difference in cleft type affects the morphologic patterns of the nasal septum. Results: The nasal septa of the alveolar and palatal cleft group patients presented more uneven morphologic patterns than those of the alveolar cleft group patients. In the alveolar cleft group, the nasal septa did not present significantly different degrees of deviation at their anterior and posterior parts. In the alveolar and palatal cleft group, however, the posterior parts of the nasal septa presented greater deviation than the anterior parts. In the alveolar and palatal cleft group, furthermore, a significant correlation was observed between the severity of the cleft and the degree of the nasal septum deviation. Conclusions: The nasal septa present different three-dimensional morphologic patterns between the patients with alveolar clefts only and those with alveolopalatal clefts. This difference should be considered when performing surgical treatments for these patients.

The boomerang osteotomy – A new method of reduction malarplasty

BACKGROUND To achieve optimal outcomes in reduction malarplasty, it is important to preserve the natural curvature of the cheek while reducing the zygoma prominence and the width of the midface. The present article introduces an effective technique that aims to achieve these purposes. METHODS Through an intraoral approach, boomerang-shaped bone incision lines are marked on the anterior aspect of the zygomatico-maxillary junction. The lines are placed medial to the most prominent part of the zygoma. The zygomatic arch is divided at its posterior part through a small incision made in the pre-auricular region. By performing these manoeuvres, a unit of bone-composed of a part of the zygoma body and zygomatic arch - is mobilised. The mobilised bone is shifted medially, reducing the width of the midface and making the zygoma region less prominent. After performing reduction malarplasty for 89 patients (10 males and 79 females) using this technique, clinical outcomes were evaluated. RESULTS Outcomes of the treatment was optimal, with over 80% of the patients evaluating the results as excellent in terms of effectiveness in malar prominence, facial width and symmetry. CONCLUSION Because the continuity of the main part of the zygoma body and zygomatic arch is preserved in our technique, medial transfer of the zygoma is enabled while preserving the natural curvature of the malar region and the superior-inferior position of the zygomatic arch. Because of these advantages, we recommend our technique as an effective technique of reduction malarplasty.

What happens between pure hydraulic and buckling mechanisms of blowout fractures

OBJECTIVE The present study aims to evaluate how the ratio of the hydraulic and buckling mechanisms affects blowout fracture patterns, when these two mechanisms work simultaneously. MATERIALS AND METHODS Three-dimensional computer-aided-design (CAD)models were generated simulating ten skulls. To simulate impact, 1.2J was applied on the orbital region of these models in four patterns. Pattern 1: All the energy works to cause the hydraulic effect. Pattern 2: Two-thirds of the energy works to cause the hydraulic effect; one-third of the energy works to cause the buckling effect. Pattern 3: One-third of the energy works to cause the hydraulic effect; two-thirds of the energy works to cause the buckling effect. Pattern 4: The entire energy quantum works to cause the buckling effect. Using the finite element method, the regions where fractures were theoretically expected to occur were calculated and were compared between the four patterns. RESULTS More fracture damage occurred for Pattern 1 than Pattern 2, and for Pattern 3 than for Pattern 4. CONCLUSION The hydraulic and buckling mechanisms interact with one another. When these two mechanisms are combined, the orbital walls tend to develop serious fractures.