The Validation of Musculoskeletal Model During Isokinetic Exercise at Knee Joint: An Experimental and Simulation Study / 대한정형외과연구학회지

PURPOSE: This study validated the musculoskeletal model of the human lower extremity by comparative study between calculated muscle parameters through simulation using modified hill-type model and measured muscle parameters through isokinetic exercise. The relationship between muscle forces and moments participated in motion was quantified from the results of simulation. MATERIALS AND METHODS: For simulation of isokinetic motion, a three-dimensional anatomical knee model was constructed using gait analysis. The EMG-force model was used to determine muscle activation level exciting muscles. The modified Hill-type model was used to calculate individual muscle force and moment in dynamic analysis. This method was validated by comparing analytical data with experimental data. RESULTS: The results showed that there was a significant correlation between calculated torques from simulation and measured torque from isokinetic motion experiments (R=0.97). We also found that muscle forces and moments during knee flexion and extension have nonlinearly proportional or inversely proportional relationship, since lower extremity muscles were simultaneously involved in flexion/extension motion and inner/outer rotation. CONCLUSION: We concluded that the simulation by using musculoskeletal model may be a useful mean to predict and recover musculoskeletal-related diseases, and analyze complicated experiment such as clash condition.

The Effect of a Chitosan Coating of Dental Implant on the shock Absorption under Impact Test

With the object of providing a temporary artificial periodonal ligament-like membrane around the dental implant, 10 Branemark type implants were coated with commercially available chitosan(Fluka Co., Buchs, Switzerland) which has a molecular weight of 70,000 and 80% deacetylation degree. Once this bioactive hydrophillic polymer(chitosan) contacts with blood or wound fluids, it becomes swollen and penetrates into the adjacent cancellous bone. Thus the interface between implant and surrounding bone is completely filled with chitosan. This tight junction in early healing phase enhances primary stability. The chitosan coated dental implants were implanted into the fresh patella bones from porcine knees, since the thickness of cortical bone is relatively even and their cancellous structure is homogenous. To test the shock absorbing effect, 1mm delta-rogette strain gage was installed behind the implant. The results showed 1. the principal strain peak value directed to the impact of coated implant was 0.064 0.018(p<0.05) and that of uncoated implant was 0.095(0.032 p<0.05). 2. the peak time delay of coated implant was 0.056sec(0.011 p<0.05) and that of uncoated implant was 0.024sec(0.009 p<0.05). It can be reasoned from this results that the chitosan coating has a shock absorbing effect comparable with a temporary artificial periodontal ligament.

A Study on the Optimal Culture Condition and Biomechanical Properties of In Vitro Tissue Engineered Cartilage Using a Fibrin Glue Scaffold

The purpose of this study was to examine the feasibility of using fibrin glue polymer designed to produce tissue-engineered cartilage by in vitro culture and to determine the optimal fibrinogen and chondrocyte concentrations required to generate cartilage and to evaluate the biomechanical properties of the generated cartilages. The most favorable fibrinogen and chondrocyte concentrations were determined by measuring the volume and weight gains, evaluating the histologic changes and measuring the biomechanical properties after construction of 12 different chondrocyte-fibrin glue constructs. The results are as follows. 1. The fibrin glues without chondrocytes degraded during 8 weeks of culture period. 2. The construct gains more weight in those with higher chondrocyte and fibrinogen concentration. 3. Histologic analysis of the generated cartilage showed nearly homogeneous cartilage when using 80 mg/cc fibrinogen and 4 x 10(7) chondrocyte/cc at 8 weeks in vitro culture. 4. The compressive modulus is higher in constructs with higher fibrinogen concentration and is 35.4 -36.8% of the normal joint cartilage. 5. The yield stress is higher in constructs with higher fibrinogen concentration and is 11% of the normal joint cartilage. This study demonstrates that fibrin glue is a suitable polymer for generation of cartilage by in vitro culture method. The construct with 80 mg/cc fibrinogen and 4 x 10(7) chondrocyte/cc yields the best quality of cartilage at 8 weeks when analyzed by weight and volume changes, histology and biomechanical properties. The compressive modulus and yield stress of the generated cartilage are lower than those of normal joint cartilage, and may still be adequate for the purpose of craniofacial reconstruction which seeks more pliant cartilage not requiring weight bearing strength.

Estimation of Young's Modulus and Apparent Density of Human Trabecular Bone by Spherical Indentatin Test and CT / 대한정형외과연구학회지

We intended to evaluate the Young's modulus of trabecular bone and apparent density from Computed Tomography(CT) and Spherical Indentation test and to quantify relation ship between them. The distal femurs(31 age, male, left and right) were prepared for exprimentatin and were embedded with repect to anatomical orientation. Then the specimens were scnned at 1 mm intervals on GE9800 CT scanner and the Hounsfield Units(HU, or CT number) were extracted from each CT image. After scanning, the bones were sectioned with diamond saw, producing 8 mm cubes of trabecular bone(72 eachs) from the metaphyseal region of both distal femur. The cubes were mechanically tested in inferior-superior(IS), anteriorposterior(AP), and medial-lateral(ML) direction with custom-made device, Spherical Indentatin Tester. After testing, the real apparent density of specimens were measured. The results of this study showed that the IS modulus was singificantly greater than both the AP and ML modulus and the AP modulus was also greater than ML modulus significantly(p<0.01). A linear relation ship between HU and real apparent density was found to be significant(R2=0.68) and significant power relationship between the apparent density and the tangent moduli(either by CT or physical measures) was also found.