INTRODUCTION

Femur is one of the bones in humans that exhibit ethnic, racial, and gender difference. Several basic and clinical studies were conducted to explore these variations. Clinical anthropological studies have dealt with the compatibility of femoral prostheses and osteosythesis and materials with the femur. If there is a misalignment between the Total Knee Arthroplasy (TKA) femoral comportment installation position, Range of Motion (ROM) failure and several problems may arise. The aim of this study was to evaluate anterior bowing of the Japanese femur and to assess the adequacy of TKA femoral comportment installation position.

Aims

Recently, total knee arthroplasty (TKA) has been generalized as an operation that achieves excellent clinical results. However, younger and Asian patients require even greater implant longevity and functional performance. We hypothesized a novel posterior cruciate-retaining TKA design that restores the anatomical jointline in both sagittal and coronal planes, maintains the femoral posterior condylar offset, and provides low contact stress would provide enhanced patient function with the potential for greater implant longevity.

Medial pivot total knee arthroplasty is designed to permit posterior rolling and sliding of the lateral femoral condyle around a stable medial femoral condyle. The purpose of the current study was to analyze the weight-bearing kinematics of medial pivot TKA’s with three different treatments of the posterior cruciate ligament: PCL resected, PCL partially released and PCL retained, to determine if the PCL status had a significant effect on tibiofemoral translations or rotations in a medial pivot TKA design.

In vivo kinematics were determined for 17 clinically successful total knee arthroplasties during a stair-climbing activity using lateral fluoroscopy and shape matching techniques.

All three groups showed similar medial pivot motions. PCL retained knees showed significantly greater tibial internal rotation than PCL resected knees for flexion of 30° and greater. Rotation of the PCL released knees was midway between PCL resected and PCL retained knees

Regardless of PCL treatment, patients with medial pivot total knee arthroplasties had medial pivot motion patterns during stair climbing activities. This study showed a clear and intuitive trend in motions with PCL-treatment, such that knees with partially released PCL’s had kinematics midway between those where the PCL was either fully maintained or fully resected.

Introduction: Fibroin sponge is purified silk protein from which high-strength gel sponge can be produced. The purified fibroin sponge causes no immune response. This study evaluates unique performances of the fibroin sponge for articular-cartilage regeneration, and mechanical properties of regenerated cartilage were also measured.

Methods: Refined silk yarn was dissolved in 9M lithium bromide aqueous solutions, and was frozen in −20& #8451 freezer for 12 hours. Hydrogel sponge was formed under the room temperature. Articular cartilage slices were taken from the proximal humerus, distal femur and proximal tibia of 4-week-old Japanese white rabbits. The cartilage slices cut into small pieces and were digested with 0.25% trypsin in DMEM containing antibiotics for 30 min at 37& #8451. After rinsing with Tyrode’s balanced solution and centrifuging at 180 G for 5 min, the chondrocytes were isolated with 0.25% collagenase for 8 h at 37& #8451. These cells were harvested and inoculated into the fibroin sponge. The constructs of the chondrocytes and the fibroin sponge were cultured in DMEM containing 10& #65285 FCS and 50mL L-ascorbate for 4weeks. Indentation test and dynamic visco-elastic measurement were carried out for these constructs.

Results and discussion: Cell density of the inoculated chondrocytes was increased to about five times as much as initial volume. This regenerated tissue was intensely stained with safranin-O fast green and showed a meta-chromatic reaction. This also stained positively with immunostain for type & #8545 collagen, but negatively with immunostain for type & #8544 collagen. Mechanical tests showed that time constants of compressive creep and E’ values were increased with cultivation days, and the peak value and frequency of tan& #948 shifted to a lower amount. The change in dynamic visco-elastic properties of the regenerated cartilage is caused by synthesis of extracellular matrix.

The role of the posterior cruciate ligament (PCL) after total knee arthroplasty has been controversial. Previous studies have reported that function of the preserved PCL after TKA was questionable and that it was difficult to determine the appropriate PCL tension to reproduce rollback. However, several in vivo studies have reported that prosthesis geometry directly affects knee kinematics, making it difficult to determine which factors most influence knee kinematics. The purpose of this two-center, two surgeons study was to evaluate knee kinematics of a single design of CR TKA. A total of 23 TKAs were studied fluoroscopically during a single-limb step-up/down maneuver. The average patient age at the time of TKA, knee score (HSS/KSS) and ROM were 70.6 years, 91.1 points and 116.9 degrees respectively. All patients had a PCL-retaining prosthesis of the same design using an unconstrained “flat” tibial insert. TKAs were performed by one surgeon at each hospital (Group 1:13 knees, Group 2: 10 knees). Both groups of knees exhibited ‘screw-home’ type axial rotations from 20° of flexion to full extension. In Group 1, rollback occurred early in the flexion range and was maintained until 80° of flexion. In Group 2, the lateral condyle exhibited rollback in early flexion, but both condyles translated forward as flexion increased to 80°. Medial and lateral contact were more posterior in Group 1 over most of the range of motion (p< 0.05). Although femoral rollback has been infrequently observed in similar studies of PCL retaining arthroplasties, our two-center, two surgeon data suggest that rollback can be achieved using this unconstrained prosthesis with PCL retention. However, there were consistent and statistically significant differences in the knee kinematics exhibited by the two groups of patients.