Purpose. To compare and analyze the long term follow up clinical & radiological result after utilization of fixed-type & rotating-type implant for high flex both total knee replacement. Subject & Method. This paper targeted 45 patients, 90 cases that got high flex both total knee replacement with utilization of fixed-type implant(LPS-flex. ®). & rotating-type implant(P.F.C. ®. Sigma RP-F) for 1 patient by 1 operator(C.C.H) in our hospital from 2005.01 to 2006.11. Preoperative diagnoses were degenerative arthritis (43 patients, 86 cases), rheumatic arthritis (2 patients, 4 cases), mean age at the operation was 66.4 years old(54∼78), 3 men, 42 women, mean follow up period was 110.8months(97∼120). We compared and estimated Hospital for Special Surgery(HSS) score and Knee Society Score(KSS), Western Ontario and MacMaster Universities Osteoarthritis(WOMAC) score and mean range of motion of knee joint at pre-operation and last follow up for functional & clinical evaluation. And we compared and estimated change of femorotibial angle and radiolucency through erect AP & lateral x-ray at pre-, post-operation and last follow up using American Knee Society Roentgen Graphic Evaluation for radiological evaluation. Result. On the result of clinical and functional evaluation, it showed improving outcome in both group(fixed-type implant, rotating-type implant), and there was no statistically significant difference. Mean HSS score was increased from 43.0, 37.1(pre-operation) to 93.2, 92.1(last follow-up), mean KSS score was increased from 37.1, 37.2(pre-operation) to 88.8, 87.6(last follow-up), WOMAC score was also increased from 104.8, 104.4(pre-operation) to 126.1, 128.4(last follow-up). Mean joint range of motion was increased from 104.8, 104.4(pre-operation) to 126.1, 128.4(last follow-up), but there was no significant difference between 2 groups. The change of femorotibial angle was corrected from average introversion 8.2°(pre-operation) to extroversion 4.8°(post-operation) in fixed-type implant group, and average introversion 8.3°(pre-operation) to extroversion 4.8°(post-operation) in rotating-type implant group, and there was no significant difference between 2 groups. And in all cases, there was no change of radiolucency, loosening of implant, or osteolysis at the last follow-up. Conclusion. It showed good functional, clinical and radiological result on long term follow-up in both groups that got both total knee replacement with utilization of fixed-type implant and rotating-type implant for 1 patient, and there was no statistically significant difference between 2 groups. As a result, it is considered that the selection of implant will be up to the condition of patient and experience of operator and so on

Unicompartmental knee arthroplasty (UKA) is often considered to be attractive alternate surgical technique to total knee arthroplasty (TKA) and high tibial osteotomy (HTO), in particular young patients. In addition, it is recently reported that preservation of joint line in UKA is crucial factor for positive long-term outcome, especially in revision case for UKA. However, the role of this joint line has neither been invested nor is it consciously bothered during surgical implantation. Validated finite element (FE) analysis was introduced in this study to investigate the effects of maximum contact stress on polyethylene (PE) insert and maximum compressive stress in opposite compartments for joint line in fixed-type UKA. As suggested by Weber et al., FE model for joint line was developed by means of determination of the angle between the pre-operative joint line and the reference line from lateral cortical is of the femur. Based on the method above, joint lines were modeled in −3, −2, −1, 0, +1, +2, and +3 mm cases and these seven FE models were compared and analyzed (Fig. 1). All implant components were modeled as linear elastic isotropic materials. However, the model was considered to have plastic characteristics of PE insert. FE analysis was performed using high kinematics displacement and rotation inputs, which were based on the kinematics of the natural knee. ISO standards were used for axial load and flexion (Fig. 2). The FE model was subjected to validation based on cadaveric experimental data available in the literature by Sohn et al. and from previous cadaveric tests conducted by current investigators. The maximum contact stress was found at around 43 % of the gait cycle in 0 mm case. There were no difference between ± 1 and 0 mm cases, but maximum contact stress on PE insert becomes greater in ± 3 mm cases. The maximum compressive stress of the lateral meniscus in 0 mm case occurred at 62 % of the gait cycle. There were no difference in positive joint line cases in maximum compressive stress, however maximum compressive stress of the lateral meniscus becomes greater in - 3 mm cases. This study emphasized the importance of joint line preservation after implantation of UKA. It would be critical to determine the joint line in UKA surgery in future based on the result showing that there has been no remarkable difference in stress but changed rapidly from the position beyond the joint line. In future study, it would be valuable study to compare between joint lines of fixed- and mobile-type UKA