To achieve 3D kinematic analysis of total knee arthroplasty (TKA), 2D/3D registration techniques, which use X-ray fluoroscopic images and computer-aided design model of the knee implants, have been applied to clinical cases. In previous feature-based registration methods, only edge contours originated from knee implants are assumed to be extracted from X-ray images before 2D/3D registration. Due to the influence of bone and bone-cement close to knee implants, however, edge detection methods extract unwanted spurious edges and noises in clinical images. Thus, time-consuming and labor-intensive manual operations are often necessary to remove the unwanted edges. It has been a serious problem for clinical applications, and there is a strong demand for development of improved method. The purpose of this study was to develop a pose estimation method to perform accurate 2D/3D registration even if spurious edges and noises exist in knee images. Our 2D/3D registration technique is based on a feature-based algorithm, and contour points from X-ray images are extracted by Gaussian Laplacian filter and zero crossing methods. The basic principle of the algorithm is that the 3D pose of a model can be determined by projecting rays from contour points in an image back to the X-ray focus and noting that all of these rays are tangential to the model surface. Therefore, 3D poses are estimated by minimizing the sum of Euclidean distances between all projected rays and the model surface. Additionally, we introduce robust statistics into the 3D pose estimation method to perform accurate 2D/3D registration even if spurious edges and noises exist in knee images. The robust estimation method employs weight functions to reduce the influence of spurious edges and noises. The weight functions are defined for each contour point, and optimization is performed after the weight functions are multiplied to a cost function.Purpose
Methods
Various postoperative evaluations using fluoroscopy have reported in vivo knee flexion kinematics under weight bearing conditions. This method has been used to investigate which design features are more important for restoring normal knee function. The objective of this study is to evaluate the kinematics of a Posterior-Stabilized TKA in weight bearing deep knee flexion using 2D/3D registration technique. We investigated the in vivo knee kinematics of 9 knees (9 patients) implanted with a Posterior Stabilized TKA (Triathlon PS, Stlyker Orthopedics, Mahwah, NJ). Under fluoroscopic surveillance, each patient did a deep knee flexion under weight-bearing condition. Femorotibial motion including tibial polyethylene insert were analyzed using 2D/3D registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components from single-view fluoroscopic images. We evaluated the knee flexion angle, femoral axial rotation, antero-posterior translation of contact points, and post-cam engagement were evaluated.Background
Patients and methods
It is widely accepted that navigation system for TKA improves precision in component alignment. Furthermore, some of the system can measure knee kinematics during surgery. On the other hand, the measurements of kinematics during surgery have limitations because of anesthesia and usage of air tourniquet. The purpose of the present study is to compare the knee kinematics during surgery using navigation system and that after surgery using 2D/3D Registration Technique. Our final goal of the study is to improve clinical outcome by performing feedback of good clinical results to operating theater by means of kinematic analysis. Kinematics of ten TKA knees for female (average age 71 years old) medial compartmental osteoarthritic knees concerning axial rotation and anterior-posterior translation were measured twice, the time during surgery and 4 weeks after surgery. During surgery, measurement was performed using CT based navigation system (Vector Vision 1.6, Brain LAB, Heimstetten, Germany). Four weeks after surgery, knee kinematics was measured again using a 2-dimensional to 3-dimensional registration technique, which used computer-assisted design models to reproduce the position of metallic implants from single-view fluoroscopic images. Surgery was performed by single surgeon using subvastus approach to eliminate the influence of approach to muscle balance. Implant using the present study was P.F.C. Sigma RP-F (DePuy, Warsaw, USA). Axial rotation in navigation and 2D/3D are 12.3+/−2.3, and 12.6+/−3.8, respectively. Axial rotations in both of the measurement have the same pattern. A-P translations also have the same pattern between measurement in navigation and that in 2D/3D technique. These results suggested that intraoperative kinematic measurement links to postoperative kinematics. Studies of correlations between kinematics and good clinical results are ongoing.
Mobile-bearing (MB) total knee prostheses have been developed to achieve lower contact stress and higher conformity compared to fixed-bearing total knee prostheses. However, little is known about the in vivo kinematics of MB prostheses especially the motion of the polyethylene insert (PE) during various daily performances. And the in vivo motion of the PE during stairs up and down has not been clarified. The objective of this study is to clarify the in vivo motion of MB total knee arthroplasty including the PE during stairs up and down. We investigated the in vivo knee kinematics of 11 knees (10 patients) implanted with PFC-Sigma RP-F (DePuy). Under fluoroscopic surveillance, each patient did stairs up and down motion. And motion between each component was analyzed using two- to three-dimensional registration technique, which used computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components, and PE (implanted with four tantalum beads intra-operatively) from single-view fluoroscopic images. We evaluated the range of motion between the femoral and tibial components during being grounded, axial rotation between the femoral component and PE, the femoral and tibial component, and the PE and tibial component during being grounded.Background
Patients and methods
We report long term outcomes of the Rotaglide mobile bearing total knee arthroplasty (RTK). Between 1995 and 1998, 61 RTK prostheses were implanted at our institution consecutively. Of 34 knees with a median duration to end of follow up of 13.0 years (range 11.4 to 14.2 years), the clinical result using Knee Society Score and radiological analysis using Knee Society Roentgenographic Sytstem was evaluated. The prosthesis had an estimated survival probability of 94.1% at 13 years. There was one case of deep infection and one case of meniscal component failure.Method
Result
Mobile-bearing (MB) total knee prostheses have been developed to achieve lower contact stress and higher conformity compared to fixed-bearing total knee prostheses. However, little is known about the in vivo kinematics of MB prostheses especially about the kinematics of polyethylene insert (PE). In vivo motion of PE during squatting still remains unclear. The objective of this study is to investigate the in vivo motion of MB total knee arthroplasty including PE during squatting. We investigated the in vivo knee kinematics of 11 knees (10 patients) implanted with Vanguard Rotationg Platform High Flex (Biomet(r)). Under fluoroscopic surveillance, each patient did a wight-bearing deep knee bending motion. Motion between each component was analyzed using two- to three-dimensional registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components, and PE (implanted with five tantalum beads intra-operatively) from single-view fluoroscopic images. We evaluated the range of motion between the femoral and tibial components, axial rotation between the femoral component and PE, the femoral and tibial component, and the PE and tibial component, and AP translation of the nearest point between the femoral and tibial component and between the femoral component and PE.Background
Patients and methods
Mobile-bearing (MB) total knee prostheses have been developed to achieve lower contact stress and higher conformity than fixed-bearing total knee prostheses. However, little is known about the in vivo kinematics of MB prostheses especially about the motion of polyethylene insert (PE). And the in vivo motion of PE during squat motion has not been clarified. The objective of this study is to clarify the in vivo motion of MB total knee arthroplasty including PE during squat motion. Patients and methods: We investigated the in vivo knee kinematics of 11 knees (10 patients) implanted with PFC-Sigma RPF (DePuy). Under fluoroscopic surveillance, each patient did a wight-bearing deep knee bending motion. And motion between each component was analyzed using two-to three-dimensional registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components, and PE (implanted with four tantalum beads intra-operatively) from single-view fluoroscopic images. We evaluated the range of motion between the femoral and tibial components, axial rotation between the femoral component and PE, the femoral and tibial component, and the PE and tibial component, and AP translation of the nearest point between the femoral and tibial component and between the femoral component and PE.
Recently mobile-bearing total knee arthroplasty (TKA) has become more popular. However, the advantages of mobile bearing (MB) PS TKA still remain unclear especially from a kinematic point of view. The objective of this study was to investigate the difference and advantage in kinematics of mobile baring PS TKA compared with fixed bearing (FB) PS TKA. Femorotibial nearest positions for 19 subjects (20 knees), 10 knees implanted with NexGen Legacy flex (Zimmer, Warsaw, IN)with mobile bearing PS TKA, and 10 knees implanted with NexGen Legacy flex (Zimmer, Warsaw, IN)with fixed bearing PS TKA were analyzed using the sagittal plane fluoroscopic images. All the knees were implanted by a single surgeon. All the subjects performed weight bearing deep knee bending motion. We evaluated range of motion, axial rotation of the femoral component, AP translation of medial and lateral sides. The average range of motion between femoral component and tibial component was 119°±18° in MB and 122°±10 ° in FB. The axial rotation of the femoral component was 11.8°±6.2° in MB and 11.8°±4.9° in FB. There was no significant difference both in range of motion and axial rotation between MB and FB. The AP translation of MB and FB showed same patterns. They were rollback in early flexion, the lateral pivot pattern (the medial condyle moved forward significantly compared with the lesser amount of AP translation for the lateral condyle) at mid flexion, and bicondylar rollback at deep flexion. The rollback in early flexion was 3.4mm in MB and 1.8mm in FB at medial side, 4.2mm in MB and 4.8mm in FB at lateral side. There was no significant difference. The lateral pivot pattern, which moved anteriorly, was 7.8mm in MB and 7.0mm in FB at medial side, 3.0mm in MB and 2.4mm in FB at lateral side. There was no significant difference. The bicondylar rollback at deep flexion was 6.4mm in MB and 7.7mm in FB at medial side, 6.9mm in MB and 4.8mm in FB at lateral side. In four subjects, more than 12°axial rotation was observed in knees implanted with FB TKA which allows only 12°axial rotation. The results in this study demonstrate that there was no significant difference in kinematics of weight bearing deep knee bending motion between MB and FB. The advantage of MB is allowance of axial rotation which restricted until 12° in FB NexGen Legacy flex PS TKA.
The current study aimed to analyze in vivo kinematics during deep knee bending motion by subjects with fully congruent designed mobile-bearing total knee arthroplasty (TKA) allowing axial rotation and anterior/posterior (AP) gliding. Twelve subjects were implanted with Dual Bearing-Knee (DBK, slot type: Finsbury, UK) prostheses. These implants include a mobile-bearing insert that is fully congruent with the femoral component throughout flex-ion and allows axial rotation and a 4–6 mm limited AP translation. Sequential fluoroscopic images were taken in the sagittal plane during loaded knee bending motion. In vivo kinematics of knee prostheses were computed accurately using a 2D/3D registration technique, which uses computer-assisted design models to reproduce the spatial position of metallic femoral and tibial components from calibrated single-view fluoroscopic images. The average femoral component demonstrated 13.4° external axial rotation for 0° to 120° flexion. On average, the medial condyle moved anteriorly 6.2 mm for 0° to 100° flexion, then posteriorly 4.0 mm for 100° to 120° flexion. On average, the lateral condyle moved anteriorly 1.0 mm for0° to 40° flexion, then posteriorly 8.7 mm for 40° to 120° flexion. The average subject experienced a lateral pivot pattern from −5° to 60° flexion, a central pivot pattern from 60° to 100° flexion, and a rollback pattern which bilateral condyles moved backward from 100° to 120° of knee flexion. Subjects with DBK mobile-bearing TKA in some-degree reproduced femoral external rotation during increasing knee flexion and bicondylar posterior rollback during terminal flexion, due to surrounding soft tissue structures. The geometry of replaced articular surfaces and mobility of the mobile-bearing insert produced lateral-to-central pivoting motions during the flexion cycle, a phenomenon not typically observed in normal knees. Using the current technique, we characterized the unique kinematics of fully congruent designed DBK mobile-bearing knee prostheses.