Transmission efficiency of Ilizarov external fixator orthopedic force based on coordinate transformation theory / 中国组织工程研究

BACKGROUND: The study on the mechanism of force conduction of Ilizarov bone external fixator is of great significance for clinical orthodontics of the knee varus, the knee valgus and the tibial fracture. OBJECTIVE: To explore the force conduction mechanism of Ilizarov bone external fixator and the force changes of each orthopedic force in the process of tibia correction, and to objectively evaluate the overall use effect of the external fixator. METHODS: According to the structure of the external fixator, the coordinate transformation matrix relations were established, and the mathematical transformation relationship between the holding force and the pulling tension was obtained. A special laboratory bench was set. The experiment of tibia correction was conducted. The load on the external fixator and the variation of the orthotic force were measured. The theoretical value of the tension at the broken bone is calculated and compared with the actual value of the tension measured by the six-dimensional force sensor. The curve of efficiency of force transmission during correction was obtained. RESULTS AND CONCLUSION: (1) During the correction, the structure of the Ilizarov bone external fixator resulted in the interaction and restriction of its adjustment rod and support rod. When one adjustment force increased, the other adjustment force would decrease. (2) The efficiency of force transmission was increased greatly in the early stage, and then stabilized at about 50%. The experimental results could evaluate the overall correction effect of the external fixator. (3) Theoretical calculation and experiment of the tension at the broken bone due to the loss during the force transmission process were different in the result curves, but from the experimental results, it could be indicated that the overall force change trend of the adjustment force, supporting force, the theoretical value of the tension and the actual value of the tension was basically the same, indicating the validity of the theoretical calculations and experimental results. The evaluation results can provide a reference for the optimal design of Ilizarov’s external fixation architecture and the precise control of tibial orthopedic surgery.

Biomechanical Analysis and Calculation of Lenke1A/B Type Scoliosis Correction / 医用生物力学

Objective The functional relation between the correction angle and orthopedic force of scoliosis can be derived based on the force principle of scoliosis correction. The position and size of the orthopedic force with the best effect of spinal correction can be calculated to provide a theoretical calculation method for the application of orthopedic forces on scoliosis. Methods The coordinates of the scoliosis central axis were collected based on the computed tomography (CT) data of scoliosis. The spline curve of scoliosis was fitted using the MATLAB software. The scoliosis constitutive polynomial was obtained, and then, the scoliosis Cobb angle was calculated by programming. Based on the clinical medicine and experimental data of spinal biomechanics, a curved beam model was used for the correction calculation and analysis of scoliosis. Results The function relation between the orthopedic force and angle at any positions was derived at different orthopedic forces. The comprehensive elastic modulus of the spine was 0.29 MPa, as calculated by the function relation. Conclusions The calculation and analysis provided a reliable theoretical basis for the relationship between the loading position, size, and restoration angle of the orthopedic forces during scoliosis correction. For patients with different types of scoliosis, the function relation between the orthopedic angle and orthopedic force could be optimized to obtain the optimal orthopedic force and loading position.

The effect of dental orthopedic force to implants on bone tissue before complete osseointegration / 대한치과교정학회지

The dental implants for edentulous patients have been used for more than 20 years. After the introduction of osseointegration by Branemark, the commercially pure titanium implants were accepted by most practitioners. Recently dental implants are used for orthodontic anchorages as well as prosthetic abutment. Many researchers have reported implants as a good orthodontic anchorage through basic research and clinical evaluation. But previous researches were done after the healing time for osseointegration of inserted implants. If dental implants are to be used for prosthetic abutment the healing time for osseointegration is necessary, but orthodontic forces to implants are different from bite force regarding its amount of force, duration and direction. The authors evaluated the effect of orthopedic force to implants on bone tissue before osseointegration. 48 implants were placed at 12 rabbits. 2 implants into left side and 2 implants into right side were inserted along the long axis of femur respectively. 2 weeks (2 weeks group), 4 weeks (4 weeks group) and 6 weeks (6 weeks group) after implants placement, 300g force had been applied to the implants at left side femur by Ni-Ti close coil spring for 4 weeks (experimental group) and no force applied to implants at right side femur (control group). After the force application for 4weeks, rabbits were sacrificed and microscopic evaluation was done by hematoxylin-eosin stain and Masson trichrome stain. The results were followed, 1. All implants iii experimental group remained rigid after the force application for 4 weeks. 2. More fibrous tissue between bone and implants were noticed at 2 weeks experimental group than 2 weeks control group. 3. More bone remodeling was noticed at 4weeks group than 2 weeks group and it was difficult to find out fibrous tissue between bone and implants at both experimental and control group of 4 weeks group. 4. It was hard to distinguish experimental group from control group at 6 weeks group. Therefore if initial stability can be obtained on implant insertion, it can be possible to use implants as a orthodontic anchorage before the healing time for osseointegration.

An experimental study on the effect of the mandibular retractive force on the mandibular condyle of growing young dog / 대한치과교정학회지

The purpose of this study was to evaluate the effects of the mandibular retractive force on the mandibular condyle of growing dog. The experimental animals were six mongrel dogs of two-month old. Their deciduous dentition were completed. Two of them was used as control group, and experimental group was composed of remaining four. Head band and chin cup were made of cotton tape, and hooks are fabricated on the chin cup and had band for closed coil. Mandibular retractive force was 100g/side and chin cap appliance was used for 14 hours/day during night. Experimental group were sacrificed at 2, 4, 6, 8 weeks from beginning of the experiment. Right TMJ was prepared for histologic study and left TMJ was examined grossly for disc, fossa, and condyle. The conclusions are: 1. Two-month old control animal showed active cartilaginous growth on the mandibular condyle, therefore showed thick proliferative and hypertrophic zones. Remodeling process in the condyle head was observed in which there were bone resorption on the anterior surface and bone apposition on the posterior surface. 2. Four-month old control animal showed marked reduction of hypertrophic zone but the condylar bone remodeling was more pronounced. 3. In experimental group, there are marked reduction of hypertrophic zone at 4 weeks from beginning of experiment, and hypertrophic zone disappeared at posterior-superior portion of condyle in 6-week experimental animal. 8 week experimental animal showed slight recovery of hypertrophic zone. 4. In experimental group, bone deposition was increased at anterior surface of condyle, and bone resorption was increased at posterior surface of condyle. 5. In control group, the glenoid fossa and surrounding bone showed mainly bone apposition. But experimental group showed bone resorption at anterior surface of articular eminence and increased bone apposition at posterior surface of postglenoid spine. 6. No marked traumatic change was seen but 4 weeks and 8 weeks experimental animal showed flattening of posterior surperior condylar surface. Bone marrow of condyle showed minute focal bleeding in 2 weeks and 4 weeks experimental animal, and congestion and depression of hematopoietic bone marrow during all experimental period.