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Biomedical subjects

Tatsuo Nakajima

Publications and source records attributed to Tatsuo Nakajima.

At least 19 recordsLinked to original sources
PubMed2006

Adaquate fixation of plates for stability during mandibular reconstruction.

PURPOSE: To determine the most appropriate plate fixation for dispersing the stress around screws in mandibular reconstruction. MATERIAL AND METHODS: Forty-eight three-dimensional reconstructed mandibular models with Central (C) or right Lateral (L) defects were created and divided into three groups, fixed with: (1) two screws on each side, (2) three screws on the left side with the third (middle one) located distally, or (3) three screws on the left side with the third (middle one) located proximally. A 300N vertical load was applied to the left molar region. The maximum stress was calculated using a finite element method and statistically evaluated. RESULTS: Stress was concentrated around the screw at the distal end of the mandibular halves on the loaded side ('crucial screw'). For the C defect, stress concentrated around the 'crucial screw' was greater when there were only two screws for fixation (20.55MPa) than when there were three screws (16.17MPa; p=0.022). No significant difference was found between the two groups with three screws for fixation. For the L defect on the other hand, stress on the 'crucial screw' was relatively greater when there were three screws for fixation (18.9MPa) than when there were only two screws for (12.83MPa; p=0.051). No significant difference was found between the two groups with three screws for fixation. As for the reconstruction plate, the stresses on the plates were not different among the various screw groups for fixation nor among the C and L defects. CONCLUSION: This paradoxical result is explained by plate bowing. Thus in large defects screw positions should take into consideration the potential for plate bowing.

Bite Force↗
PubMed2006

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 bone's 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.

Biomechanical Phenomena↗
PubMed2006

Three-dimensional computer graphics for surgical procedure learning: Web three-dimensional application for cleft lip repair.

OBJECTIVE: In surgical procedures for cleft lip, surgeons attempt to use various skin incisions and small flaps to achieve a better and more natural shape postoperatively. They must understand the three-dimensional (3D) structure of the lips. However, they may have difficulty learning the surgical procedures precisely from normal textbooks with two-dimensional illustrations. Recent developments in 3D computed tomography (3D-CT) and laser stereolithography have enabled surgeons to visualize the structures of cleft lips from desired viewpoints. However, this method cannot reflect the advantages offered by specific surgical procedures. To solve this problem, we used the benefits offered by 3D computer graphics (3D-CG) and 3D animation. DESIGN AND RESULTS: By using scanning 3D-CT image data of patients with cleft lips, 3D-CG models of the cleft lips were created. Several animations for surgical procedures such as incision designs, rotation of small skin flaps, and sutures were made. This system can recognize the details of an operation procedure clearly from any viewpoint, which cannot be acquired from the usual textbook illustrations. This animation system can be used for developing new skin-flap design, understanding the operational procedure, and using tools in case presentations. The 3D animations can also be uploaded to the World Wide Web for use in teleconferencing.

Cleft Lip↗
PubMed2006

The dynamics in implantation for patients with clefts.

OBJECTIVE: To investigate the stresses and strains of an endosseous dental implant in patients with different types of cleft palate in a finite element model. MATERIALS AND METHODS: Seven three-dimensional (3D) maxillary models were designed on a personal computer according to computed tomography slice data obtained from seven dry skulls. Next, computer-aided modification was performed on each model to produce three other 3D models with different cleft patterns. Thus, four model types with different cleft patterns were designed and termed NORM (without cleft), ALVEOLAR (only alveolar cleft), PALATAL (only palatal cleft), and COMPLETE (complete cleft). An implant was embedded into the molar region of each model, and a 300-N vertical load and 50-N horizontal load were applied to simulate mastication. Under these conditions, the stresses occurring at the implant-bone interface were calculated by finite element analysis. RESULTS: Different stress patterns were observed between the models with a palatal cleft (PALATAL and COMPLETE) and those without palatal cleft (NORM and ALVEOLAR). Regarding vertical load application, greater stresses occurred in PALATAL and COMPLETE types than in NORM and ALVEOLAR types. On application of a horizontal load, though the stresses did not show quantitative difference, their vector patterns differed. CONCLUSION: In patients with palatal clefts, characteristic stress patterns occur on the bone-implant interface during mastication. This should be taken into consideration when performing an implant treatment in patients with clefts.

Alveolar Process↗
PubMed2006

Cleft palate repair using a marginal musculo-mucosal flap.

OBJECTIVE: To describe a modified procedure consisting of a mucoso-periosteal flap palatoplasty with a marginal musculo-mucosal flap (3M flap). This is also the first report of a primary repair for complete cleft palate using the 3M flap. We describe the lengthening effect of the nasal mucous layer of the soft palate and evaluate the fistula formation rate associated with this method. METHODS: This procedure has been performed on 21 patients with unilateral complete clefts and on 27 patients with incomplete clefts. A mucoso-periosteal flap raised from the hard palate was used mainly for closure of the cleft and not for the push-back. The 3M flap repaired the deficit of the nasal mucosa, making sure that the soft palate was lengthened. Intravelar veloplasty was performed also. RESULTS: The dimension of the nasal mucosal defect that can be filled with the 3M flap is 10 to 12 mm in length, oriented anterior-posterior, and 15 to 20 mm wide. Oronasal fistula formation was recognized in only 3 of 48 cases (2 of 21 complete clefts, 1 of 27 incomplete clefts) and were located at the hard-soft palate junction at the anterior portion of the 3M flap. CONCLUSIONS: This method has the theoretical advantages of (1) preventing fistula formation by filling the tissue deficiency with the 3M flap; (2) achieving better velopharyngeal function due to elongation of the soft palate and retropulsion of the muscular bundle, utilizing the 3M flap; and (3) minimizing maxillary growth retardation by adopting a non-push-back method of hard palate repair.

Biological Dressings↗
PubMed2006

A comparative study of most suitable miniplate fixation for mandibular symphysis fracture using a finite element model.

The purpose of this study is to determine the most stable fixation method for mandibular symphysis fractures by comparing the mechanical characteristics of models fixed at different positions with different numbers of plates. Fractures were generated in 3-dimensional finite element models, and were fixed with a single miniplate, parallel double miniplates, or perpendicular double miniplates. A 300 N perpendicular load was then applied on the left molar region, and a finite element analysis was performed. We compared vertical gaps between the fractured surfaces, maximum stress within the screw/plating system, and maximum stress around screw holes in the bone. Compared to the single miniplate, both the parallel and perpendicular double miniplates demonstrated significantly less stress in the screw/plating system and screw holes in the bone. In addition, the perpendicular double miniplateshad significantly smaller vertical gaps between fracture surfaces when compared to the single miniplate. Comparing parallel and perpendicular double miniplate fixations, less stress was found around the screw holes of the perpendicular miniplate models than those of the parallel miniplatemodels. There were no differences in vertical gaps or maximum stress within the screw/plating systems between the 2 double miniplate fixations. These results suggest that perpendicular double miniplate fixation is more suitable for fixing mandibular symphysis fractures.

Bone Plates↗
PubMed2005

The dynamic role of buttress reconstruction after maxillectomy.

BACKGROUND: The purpose of this study was to investigate the dynamic effect of maxillary reconstruction after partial resection of the maxilla. METHODS: On a personal computer, three-dimensional maxilla models were designed based on computed tomographic data obtained from 10 edentulous skull models. Simulation surgery was performed on each model, creating 10 pairs of half-removed maxilla models and corresponding models after reconstruction with a rib. The three different patterns seen in the 10 models were termed normal maxilla, half-removed maxilla, and reconstructed maxilla. After an implant was fixed on the molar region of each model, a 300-N vertical load and a 50-N horizontal load were applied. Using finite element analysis software, the deviation and stress on each model were calculated and compared between different model patterns. RESULTS: Regarding deformity of the maxilla, when a vertical load was applied, no significant difference was observed among the three model patterns. However, a difference was observed in response to a horizontal load in that there was a tendency for deformation to occur, with that of half-removed maxilla being the greatest followed by reconstructed and normal maxilla. Regarding stresses around the implant, when the vertical and horizontal loads were applied, no significant difference was observed among the three model patterns in maximum stress around the implant. CONCLUSIONS: A buttress reconstruction is effective in increasing the stability of the maxilla against a horizontal load. However, the maximum stress around the implant in the molar region is unaffected whether or not removal or reconstruction is performed.

Computer Graphics↗
PubMed2005

Secondary repair of cleft lip nose deformity using subcutaneous pedicle flaps from the unaffected side.

We used three types of subcutaneous pedicle flaps harvested from the unaffected side of the nostril to repair postoperative nose deformity caused by primary cleft lip surgery. By moving the subcutaneous pedicle flap from a nearby tissue-rich area, it was possible to achieve a favourable symmetrical nasal contour for the narrowing of the nostril cavity, depression of the nostril floor and the columella deviation of the affected side. The method, we used here is technically simple. We believe this procedure is a method of choice for repairing small deformities of the nose occurring after primary or secondary cleft lip surgery.

Adult↗
PubMed2005

Analysis of 109 Japanese children's lip and nose shapes using 3-dimensional digitizer.

We assessed lip and nose shapes, which played an important role in performance evaluations, before and after cleft lip and nose surgery. We used a noncontact-type semiconductor laser 3-dimensional measurement system on normal Japanese children to obtain 3-dimensional images of noses and lips, which were accurate enough to measure facial shapes. We could rotate these images on the computer, therefore we measured the following points: the distance between the peaks of the Cupid's bow and the width of the labial fissure (frontal view), and the width of the nose and the nasal tip protrusion (basal view). Lip and nose shapes were evaluated for each gender. Additionally, nasolabial angles (NLA) were measured on the lateral views of faces. We classified the morphology of the philtral columns into four types; (1) triangular type, (2) parallel type, (3) concave type, and (4) flat type. We also classified nostril shapes into four types: (1) teardrop type, (2) heart shaped type, (3) round type, and (4) triangular type. We calculated the average of the 3-dimensional coordinate values for each landmark, and created standard facial models of normal Japanese children. Moreover, we invented a new morphological evaluation method before and after cleft lip and nose surgery, using the 3-dimensional data converting and editing software. The method was more feasible to evaluate the assessment cleft lip and nose surgery, by quantifying the surface areas of right and left nostrils and the surface areas of upper and lower vermilions, even now by measuring with the eyes and comparing them.

Anthropometry↗
PubMed2005

The fetal dermal but not loose fascial mesenchymal cells possess regenerative activity of dermal structure.

Fetal skin possesses a regenerative activity until certain developmental stages. However, the origin of cells that regenerate dermis after wounding has not been clarified yet. In the present study we located the origin of cells that reconstruct fetal dermal structure by histological examination and by marking cells in the loose fascia. Next we evaluated the regenerative activity of fetal dermal mesenchymal cells by cotransplanting with fetal epidermal cells onto the skin defect of scid mice. We conclude that fetal dermal mesenchymal cells but not loose fascial cells possess regenerative activity even on the environment in scid mice.

Animals↗
PubMed2004

Influence of antiplatelet substances on platelet-rich plasma.

PURPOSE: Platelets containing a number of growth factors (platelet-derived growth factor [PDGF], transforming growth factor-beta [TGF-beta], etc) can be obtained in high concentrations through centrifugal separation and are used in clinical applications as platelet-rich plasma (PRP). However, only a few studies have been conducted on the growth factors present in PRP. In this study, we focused on the concentrations of growth factors in PRP and clarified the influence of using antiplatelet substances in the process of platelet concentration to improve the concentration rate of growth factors in PRP. MATERIALS AND METHODS: We made platelet pellets from whole blood obtained from humans with or without some antiplatelet substances (prostaglandin E1, aspirin, apyrase). Platelet pellets were resuspended in phosphate-buffered saline as platelet resuspensions. We measured PDGF and TGF-beta1 concentrations in the samples. In measurements, we had the samples treated to release growth factors from platelets to measure accurate concentrations. RESULTS: PDGF and TGF-beta1 were concentrated to a mean of over 400% in the samples with antiplatelet substances as compared with the samples without antiplatelet substances. CONCLUSIONS: The antiplatelet substances were effective for efficiently concentrating growth factors in platelets.

Adult↗
PubMed2004

Basic studies on the bone formation ability by platelet rich plasma in rabbits.

PURPOSE: Platelets, which contain many growth factors, such as platelet-derived growth factor (PDGF) and transforming growth factor-beta(TGF-beta), can be obtained in high concentrations by centrifugal separation and are being used as platelet-rich plasma (PRP) in clinical applications. The authors evaluated the bone formation ability by PRP in rabbits. MATERIALS AND METHODS: In experiment 1, the authors made platelet precipitations from the whole blood obtained from rabbits. Each precipitated platelet was resuspended in fibrin glue. The glue was applied to a 1-mm wide slit defect of the same rabbit mandible. After 1 week, the authors observed the histologic appearances. In experiment 2, the fibrin glue containing the precipitated platelet was applied to a bicortical defect of a rabbit cranium with beta-tricalcium phosphate (beta-TCP) granules as artificial bone material. After 1 week, 1 month, and 2 months, the authors observed the radiologic and histologic appearances. RESULTS AND CONCLUSIONS: In both experiments, a prosperous bone formation was observed from the beginning more in the group treated with PRP than in the group untreated. In experiment 2, gradual appearances of the bone formation were observed in the bubble of beta-TCP. In application with artificial bone materials, bone formations by PRP were suitably observed.

Animals↗
PubMed2004

Transplanted mesenchymal stem cells are effective for skin regeneration in acute cutaneous wounds.

Mesenchymal stem cells (MSCs) possess the capacity for site-specific differentiation of cell types in response to cues provided by different organs. This phenomenon suggests that MSCs participate in cutaneous wound regeneration. However, there are no prior reports on the influence of the local application of MSCs on cutaneous wound regeneration. To examine the effects of MSCs on wound regeneration, we cultured bone marrow cells of the femur of rats and treated the plastic adherent cells with a differentiation medium to induce differentiation. After treatment, we found that the bone marrow-derived plastic adherent cells possessed myogenesis, chondrogenesis, and adipogenesis capabilities, indicating that these cells are MSCs. The bone marrow-derived plastic adherent cells were injected intradermally into the skin of rats, and linear full-thickness incisional wounds were made immediately through the injected area. At 14 days after operation, wounds transplanted with bone marrow-derived plastic adherent cells had healed with very fine scars. Collagen architecture was thick and appeared to be similar to normal dermis. Histomorphologic scale analysis demonstrated significant differences between the control and the wounds transplanted with bone marrow-derived plastic adherent cells. These results indicate that transplanted MSCs can respond quite normally to wound healing and regenerate dermal structure.

Acute Disease↗
PubMed2003

Long-term outcome of simultaneous repair of bilateral cleft lip and nose (a 15 year experience).

We have performed primary repair of bilateral cleft lip and nose on 169 patients in the past 15 years. During the first eight years, we used a small triangular flap skin design for the lip and for the nose correction, we used a corrective nasal cartilage lifting suture through rim incisions in order to bring the nasal dome cartilage toward the center and create the columella. The small triangular flap at the columella base was rotated 90 degrees posteriorly to emphasize the contour of the nasolabial angle. In the subsequent 7-year period, the lip design was changed to the straight line method, and an inverted trapezoid suture was placed between the alar and nasal dorsum at four points. By this procedure displaced cartilages are moved into correct position and the alar groove became more distinct.Long-term observations showed a favorable configuration of the nose, and eliminated the bilateral cleft nose stigma with only minimum degree of growth disturbance. The remaining problem is the somewhat superior faced nasal tip. To leave the bilateral cleft lip nasal deformity uncorrected for a long period places great psychosocial burden on the patient and the family. We believe that it is desirable to conduct early lip and nose repair synchronously in a minimally invasive manner, as a collaborative effort between plastic surgeons with specialized training in cleft lip repair and an interdisciplinary team.

Aged↗