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Purpose This study aimed to clarify the natural knee kinematics provided by bicruciate-retaining total knee arthroplasty (BCR-TKA) compared with those of unicompartmental knee arthroplasty (UKA) and normal knees. Methods Volunteers and patients who had undergone UKA and BCR-TKA with anatomical articular surface performed squatting motion under fluoroscopy. To estimate the knee’s spatial position and orientation, a two-dimensional/three-dimensional registration technique was used. The rotation angle and anteroposterior translation of the medial and lateral sides of the femur relative to the tibia in each flexion angle were directly evaluated using the same local coordinate system and their differences amongst the three groups were analysed using two-way analysis of variance and Bonferroni post hoc pairwise comparison. Results From 0° to 10° of flexion, the femoral external rotation angle of BCR-TKA knees was significantly greater than that of normal and UKA knees and the medial side of BCR-TKA knees was significantly more anteriorly located than that of normal and UKA knees. From 40° to 50° of flexion, the medial side of UKA knees was significantly more posteriorly located than that of normal and BCR-TKA knees. From 30° to 120° of flexion, the lateral side of BCR-TKA knees was significantly more anteriorly located than that of normal and UKA knees. Conclusion The in vivo kinematics of BCR-TKA knees reproduces those of normal knees to a lower extent than those of UKA knees. Thus, BCR-TKA with anatomical articular surface reproduces in vivo kinematics of normal knees to a lower extent than UKA. Level of evidence III.

This study analyzed 31 patients with symptomatic osteoarthritic knees scheduled to undergo knee arthroplasty or high tibial osteotomy and demonstrated shape variations in their proximal tibia using an average three-dimensional (3D) bone model. Preoperative computed tomography of the affected knees was reconstructed as 3D bone models using a triangle mesh of surface layers. The initial case was defined as the template, and the other models were reconstructed into homologous models with the same number of mesh vertices as that in the template. The corresponding mesh vertices of the other models were averaged to evaluate the spatial position on the particular mesh vertex of the template. This was applied to all the mesh vertices of the template to generate the average 3D model. To quantify the variation in surface geometry, average minimum distance from the average bone model to 31 models was recorded. The medial proximal tibial cortex (1.63 mm) revealed lesser variation compared to the tibial tuberosity (2.50 mm) and lateral cortex (2.38 mm), ( p  = 0.004 and p  = 0.020, respectively). The medial tibial plateau (1.46 mm) revealed larger variation compared to the lateral tibial plateau (1.16 mm) ( p  = 0.044). Understanding 3D geometry could help in development of implants for arthroplasty and knee osteotomy.

We analyzed the effects of bicruciate-retaining total knee arthroplasty (BCR-TKA) on knee kinematics and cruciate ligament forces. Patients (N = 15) with osteoarthritis (OA) and an intact anterior cruciate ligament (ACL) underwent magnetic resonance imaging and single-plane fluoroscopy to measure tibiofemoral kinematics during two deep knee bend activities before and after BCR-TKA: (1) weight-bearing squat; (2) non-weight-bearing cross-legged sitting. Forces in ligament bundles were calculated using VivoSim. The dynamic range of varus-valgus angulation decreased from 3.9 ± 4.4° preoperatively to 2.2 ± 2.7° postoperatively. Preoperatively, the medial femoral condyle translated anteriorly from 10° to 50° of flexion, and posteriorly beyond 50° of flexion. Postoperatively, the medial and lateral femoral condyles translated posteriorly throughout flexion in a medial pivot pattern. ACL forces were high in extension and decreased with flexion pre- and postoperatively. PCL forces increased with flexion preoperatively and did not change significantly postoperatively. Preoperatively, ACL forces correlated with anteroposterior translation of the femoral condyles. Postoperatively, PCL forces correlated with anteroposterior translation of the lateral femoral condyle. BCR-TKA altered knee kinematics during high flexion activity which correlated significantly with changes in cruciate ligament forces.

Purpose The hypothesis of this study was that the kinematics of patients with higher patient-reported outcome measures (PROMs) differ from those of patients with lower PROMs after bicruciate-stabilized total knee arthroplasty (BCS-TKA). Methods A total of 32 patients with severe knee osteoarthritis were examined 11.2 ± 3.2 months after BCS-TKA. The patients performed squats under single fluoroscopic surveillance in the sagittal plane. To estimate the spatial position and orientation of the femoral and tibial components, a 2D-to-3D registration technique was used. This technique uses a contour-based registration algorithm, single-view fluoroscopic images and 3D computer-aided design models. Knee range of motion, varus–valgus alignment, axial rotation of the femur relative to the tibial component, anteroposterior translation of the medial and lateral femorotibial contact points, kinematic paths, and anterior and posterior post-cam engagement were measured. The patients were divided into two groups using hierarchical cluster analysis based on the 1-year postoperative Knee Injury and Osteoarthritis Outcome Score and 2011 Knee Society Score. Results The femoral component had significantly more external rotation in the low-score group than in the high-score group (5.1 ± 1.8° vs. 2.2 ± 2.7°, p  = 0.02). The high-score group had a medial pivot pattern from 0 to 20° of flexion, without significant movement from 20 to 70°, and final bicondylar rollback beyond 70°. The low-score group had a medial pivot from 0 to 70° of flexion and bicondylar rollback beyond 70°. There were no significant between-group differences in the varus–valgus angle or post-cam engagement. Conclusion The higher PROM group had smaller external rotation of the femur after BCS-TKA. Level of evidence Level III.

Purpose The effects of weight bearing (WB) on knee kinematics following mobile-bearing unicompartmental knee arthroplasty (UKA) remain unknown. The purpose of this study was to clarify the effects of WB on in vivo kinematics of mobile-bearing UKA during high knee flexion activities. Methods The kinematics of UKA were evaluated under fluoroscopy during squatting (WB) and active-assisted knee flexion (non-weight bearing, NWB). Range of motion, femoral axis rotation relative to the tibia, anteroposterior (AP) translation of the medial and lateral sides, and kinematic pathway were measured. Results There were no differences in knee flexion range and external rotation of the femur in each flexion angle between the WB conditions. The amount of femoral external rotation between minimum flexion and 60° of flexion during WB was significantly larger than that during NWB, and that between 60° and 130° of flexion during NWB was significantly larger than that during WB. There were no differences in medial AP translation of the femur in each flexion angle between the WB conditions. However, on the lateral side, posterior translation of 52.9 ± 12.7% was observed between minimum flexion and 130° of flexion during WB. During NWB, there was no significant translation between minimum flexion and 60° of flexion; beyond 60° of flexion, posterior translation was 41.6 ± 8.7%. Between 20° and 80° of flexion, the lateral side in WB was located more posteriorly than in NWB ( p  < 0.05). Conclusion Mobile-bearing UKA has good anterior stability throughout the range of knee flexion. WB status affects the in vivo kinematics following mobile-bearing UKA. Level of evidence III.

We analyzed the implantation effects on cruciate ligament force in unicompartmental knee arthroplasty (UKA) and determined whether kinematics is associated with the cruciate ligament force. We examined 16 patients (17 knees) undergoing medial UKA. Under fluoroscopy, each participant performed a deep knee bend before and after UKA. A two-dimensional/three-dimensional registration technique was employed to measure tibiofemoral kinematics. Forces in the anteromedial and posterolateral bundles of both the anterior cruciate ligament (aACL and pACL) and the anterolateral and posteromedial bundles of the posterior cruciate ligament (aPCL and pPCL) during knee flexion were analyzed pre- and post-UKA. Correlations between changes in kinematics and ligament forces post-UKA were also analyzed. Preoperatively, the aACL forces were highly correlated with anteroposterior (AP) translation of the lateral condyles (Correlation coefficient [r] = 0.59). The pPCL forces were highly correlated with the varus–valgus angulation (r =  − 0.57). However, postoperatively, the PCL forces in both bundles were highly correlated with the AP translation of the medial femoral condyle (aPCL: r = 0.62, pPCL: r = 0.60). The ACL and PCL forces of the knees post-UKA were larger than those of the knees pre-UKA. Kinematic changes were significantly correlated with the cruciate ligament force changes.

Background Osteoarthritis (OA) is one of the most common joint diseases in elderly people, however, the underlying mechanism of OA pathogenesis is not completely clear. Periostin, the extracellular protein, has been shown by cDNA array analysis to be highly expressed in OA, but its function is not fully understood. The purpose of this study was to examine the expression and function of periostin in human OA. Methods Human cartilage and synovia samples were used for the analysis of periostin expression and function. The human cartilage samples were obtained from the knees of patients undergoing total knee arthroplasty as OA samples and from the femoral bone head of patients with femoral neck fracture as control samples. Quantitative RT-PCR, ELISA, and immunohistochemistry were used for analysis of periostin expression in cartilage and synovia. Human primary chondrocytes isolated from control cartilage were stimulated by periostin, and the alteration of OA related gene expression was examined using quantitative RT-PCR. Immunocytochemistry of p65 was performed for the analysis of nuclear factor kappa B (NFκB) activation. Results The periostin mRNA was significantly higher in OA cartilage than in control cartilage. Immunohistochemical analysis of periostin showed that the main positive signal was localized in chondrocytes and their periphery matrix near the erosive area, with less immunoreactivity in deeper zones. There was positive correlation between Mankin score and periostin immunoreactivity. The periostin expression was also detected in the fibrotic cartilage and tissue of subchondral bone. In cultured human chondrocytes, periostin induced the expression of interleukin (IL)-6, IL-8, matrix metalloproteinase (MMP)-1, MMP-3, MMP-13, and nitric oxide synthase-2 (NOS2) in a dose- and time-dependent manner. The activation of NFκB signaling was recognized by the nuclear translocation of p65. Periostin-induced upregulation of these genes was suppressed by NFκB inactivation in chondrocytes. Conclusion Periostin was upregulated in OA cartilage, and it may amplify inflammatory events and accelerate OA pathology.

Background The Flexible Nichidai Knee Posterior Stabilized (FNK-PS) system was designed to provide relatively high varus-valgus stabilities without the stem extensions to patients with severe knee joint disorders. This is a combination of a large tibial post and high femoral cam adapted to a PS system. The aim of our study was to analyze the in vivo two-dimensional/three-dimensional registration kinematics of the FNK PS-total knee arthroplasty (TKA) system during deep knee bending. Methods Nineteen knees from 15 total knee arthroplasty (TKA) patients who were able to squat with enough knee flexion were selected. During deep knee bending under weight bearing (WB) and non-weight bearing (NWB) conditions, we quantified range of motion, axial rotation, femoral anteroposterior translation, and post-cam engagement angle. Results The maximum-flexion was significantly different between the two conditions. The mean axial femoral external rotation was 4.8° and 6.2° under WB and NWB conditions, respectively, at 120° flexion. Anteroposterior translation based on bicondylar posterior roll-back patterns was noted with increasing knee flexion. Both the medial and lateral femoral aspects were significantly more posterior during early to mid-flexion. Initial post-cam engagement occurred significantly earlier during flexion under NWB than under WB conditions. Under WB, the timing of the post-cam engagement correlated with the maximum flexion . Conclusions The kinematics of the semi-constrained PS system reproducibly exhibited a mild external rotation with smooth posterior roll-back. This was assisted by the engagement of the large tibial post and high femoral cam during the early phase of flexion.

Evaluating WB status during normal knee flexion activities is important for optimizing surgical procedures and postoperative rehabilitation. This study aimed to clarify the effects of weight-bearing (WB) on in vivo knee kinematics and cruciate ligament forces in normal knees. Fluoroscopic imaging in the sagittal plane was used while volunteers performed squatting and active-assisted knee flexion. Tibiofemoral kinematics were measured using a two-dimensional/three-dimensional registration technique. Forces in the anterior cruciate ligament (anteromedial/posterolateral; aACL/pACL) and the posterior cruciate ligament (anterolateral/posteromedial; aPCL/pPCL) were analyzed. Anteroposterior translation (APT) of low contact points (LCPs) in WB and non-weight-bearing (NWB) conditions showed no anterior translation from extension to mid-flexion. The medial APT of LCPs in the NWB was more posterior than in WB. Medial stabilized articular surface and/or a surgical technique may help restore native knee kinematics across WB conditions.