Papers by Author: Soon Hyuck Lee

Abstract: "Osseo" refers to bone and "integration" refers to how a prosthesis can be integrated with the bone in residual limbs both arms and legs. Osseointegration(OI) was originally defined as a direct structural and functional connection between ordered living bone and the surface of a loadcarrying implant. OI could be described as the modality for stable fixation of titanium implant to bone structure. The OI has become a realized phenomenon of importance in the dental and rehabilitation sciences since recently developed dentures and artificial limbs are directly attached to human skeleton by using osseointegrated implants. Previously, a study showed that bone strain generated potential (SGP) that is an electrical potential and considered to be generated by fluid flow in bone could be used as a parameter to examine the amount of OI on bone-implant interface. Since no study was performed to understand according to the point on behavior of SGP for the boneimplant composite. In this study, we used a multi-channel measurement system and investigated SGP according to the point. Four white New Zealand rabbits underwent pure titanium implant insertion surgery to tibia after amputation. After checking full OI at the end of the 5 weeks, experimental animals were euthanized and the amputated tibia-implants were harvested. Holes of 0.5mm in diameter were made on the tissue of the tibia and electrodes of 0.16mm in diameter were inserted to the holes. Then, the instrumented bone-implant composites were placed to a servo material testing machine to apply axial compressive displacement loadings. During the compression tests, SGPs were also measured. Magnitude of SGP was found to be significantly increased near bone and implant interface for the osseointegrated bone-implant composite.

Abstract: In this study, a minimally invasive assessment using bone strain generated potential (SGP) was developed to examine the amount of osseointegration (OI) at bone-implant interface. SGP is generated by interstitial fluid flow in porous bone structure. Four experimental white New Zealand rabbits underwent pure titanium implant insertion surgery to tibia after amputation. After surgery, two animals were kept in small cages with minimal movement (Group 1). In contrast, the other rabbits were kept in a large cage that was large enough for jumping and walking (Group 2). At the end of the 5 weeks, all experimental animals were euthanized and the amputated tibia-implants were harvested. Then, a quasi-static force was applied to a bone site near the bone-implant interface for each tibia-implant specimen. Also, SGPs were measured near the interface using needle or probe electrodes. After the measurements, digital radiographs were taken to check the amount of OI for the interfaces. Full OI was observed for animals in Group 1. However, incomplete OI was found for animals in Group 2. Also, significant difference was found for mean SGP values between Group 1 and 2. The results could imply that SGP could be used as a minimally invasive assessment method to check the OI at the bone-implant interface.

Abstract: The quantitative and objective evaluation of spasticity is desirable in rehabilitation and orthopedics where subjective evaluations are mostly used. In the present study, data from a simple pendulum test are used for the evaluation of the spasticity with the help of biomechanical modeling. The spasticity of a knee joint is modeled as nonlinear feedback of muscle lengthening velocity and the muscle length. Through the optimization of the modeling error, the feedback parameters are determined. The threshold of muscle lengthening velocity in the reflex system is suggested as a severity index of the spasticity.