In recent years, the number of patients with mandibular defects is increasing, and the orthognathic surgery of mandible has become a common treatment for re-establishing functional and aesthetic anatomy by repositioning displaced skeletal elements. To decrease a heavy burden and high risk of the surgery falling on the patients and clinicians, the present authors have developed a mechanical support system for orthognathic surgery. An easy, quick and patient-specific mesh generation including the periodontal ligament is essential. First, a mandible template was obtained manually, which requests the small number of elements. It is composed of 7 different materials and could reproduce the original shape of each material pretty well with a reduced number of elements. Next the template of around 6600 nodes is mapped by a simple formula in a moment of time to fit the patient's mandible polygonal image obtained from an individual CT image. The calculation with the resulted patient-specific mesh by a 3D FEM code is also performed successfully.

Keywords

FEM, Patient Specific Model, Mandible, Tooth, Periodontal Ligament

Paper information

Yoshihiro TAKAO, Junpei TAKAHASHI, Masahiko TERAJIMA, Wen-Xue WANG and Akihiko NAKASHIMA, “An Easy and Quick Formulation of Patient-Specific 3D-FEM Dentate Mandible Model with Periodontal Ligament for Mechanical Analysis”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 4 (2009), pp.550-561 . doi:10.1299/jbse.4.550

To evaluate motions and joint reaction forces of the total knee prosthesis during deep knee flexion such as kneeling and sitting straight, a simulator that reproduces the passive motion of the knee has been developed. The main feature of the simulator is that the knee joint is accurately and repeatedly moved from 0° to 180° flexion angle in six degrees of freedom. Moreover, the tibiofemoral and patellofemoral motion and joint reaction forces can be continuously measured. Assuming that muscular force is mainly generated with a quadriceps femoris muscle, the similar force vector is produced by two motors. The custom-designed posterior stabilized type total knee prosthesis which can be flexed to 180° has been inserted in the bone model and used for the evaluation. As a result, it was confirmed that this simulator was able to measure the motion and joint reaction force of the knee with high repetition accuracy. The experimental results showed the same tendency with those in the previously performed cadaveric experiment until 120° flexion. Hereafter, cadaver knee can be used for the evaluation of the knee prosthesis using the proposed simulator with high accuracy.

Keywords

Deep Knee Flexion, Knee Simulator, Passive Motion, Total Knee Prosthesis, Joint Reaction Force

Paper information

Yasuju TAKANO, Masaru UENO, Kazuo KIGUCHI, Syuya IDE, Masaaki MAWATARI and Takao HOTOKEBUCH, “Development of a Passive Knee Motion Simulator to Evaluate Deep Knee Flexion of Total Knee Prosthesis”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 4 (2009), pp.562-575 . doi:10.1299/jbse.4.562

A new simulation method was developed that considered a tumor as a solid body and therapeutic response as deformation of the tumor using mechanical analogy. As radiation exposure to the tumor was related to the external force to the solid body, the geometrical change of the tumor could be estimated from fundamental equations in solid mechanics. A change in tumor volume was calculated using finite element (FE) method. The FE models were constructed from CT images of patients before the radiotherapy. The initial radiotherapeutic parameters of tumor radioresistance and repopulation rate were determined based on a linear-quadratic model and then revised by the comparison with actual tumor volume change. Three patients with uterine cervix carcinoma were applied in this method. Simulation results well showed tendencies of tumor volume changes with radiotherapy. In addition, this method could provide the appropriate value of radiotherapeutic parameters for individual case. In conclusion, our approach could calculate three-dimensional tumor deformation during the course of radiotherapy and will provide useful information for more effective treatment.

Keywords

Mechanical Analogy, Radiotherapy, Linear-Quadratic Model, Tumor Deformation, Finite Element Analysis

Paper information

Seishin TAKAO, Shigeru TADANO, Hiroshi TAGUCHI and Hiroki SHIRATO, “Computer Simulation of Radiotherapy for Malignant Tumor”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 4 (2009), pp.576-588 . doi:10.1299/jbse.4.576

Accelerated ageing was conducted on UHMWPE with and without vitamin E (D, L-α tocopherol, VE). Wear performance was investigated using a knee simulator and wear debris was analysed. Aged UHMWPE with VE showed significantly lower wear volume than that of aged virgin UHMWPE and showed approximately similar wear volume as non-aged virgin UHMWPE. There were no significant differences among the materials as far as shape factor of the debris is concerned.

Keywords

Medical Engineering, Biomaterials, Material Testing, Wear, Bearing, UHMWPE, Vitamin E, Artificial Joint, Wear Debris, Accelerated Ageing

Paper information

Satoshi TERAMURA, Hideyuki SAKODA, Tomohiro TERAO, Kunihiko FUJIWARA, Kosuke KAWAI and Naohide TOMITA, “Reduction of Wear Volume from Accelerated Aged UHMWPE Knee Components by the Addition of Vitamin E”, Journal of Biomechanical Science and Engineering, Vol. 4, No. 4 (2009), pp.589-596 . doi:10.1299/jbse.4.589