There are few studies that have compared between continuous flexion activities and extension activities of normal knees. The purpose of this study is to compare in vivo kinematic comparison of normal knees between flexion activities and extension activities. Total of 8 normal male knees were investigated. We evaluated in vivo three-dimensional kinematics using 2D/3D registration technique. We compared femoral rotation angle relative to tibia, anterior/posterior (AP) translation of medial femoral sulcus (medial side) and lateral femoral epicondyle (lateral side) onto tibial plane perpendicular to tibial functional axis between flexion activities (F groups) and extension activities (E groups). Femoral external rotation was observed with the knee bending during both groups. The external rotation angle of F group was larger than that of E group significantly from 20 to 30 degrees with flexion (p < 0.05). Regarding medial side, anterior translation was observed up to 40 degrees in F group. From 40 to 140 degrees, posterior translation was observed. In E group, anterior translation was observed from 140 to 40 degrees with extension. From 40 degrees, posterior translation was observed. From 30 to 40 degrees, F group located anterior than E group (p < 0.05). Regarding lateral side, posterior translation was observed with flexion in F group. On the other hand, anterior translation was observed with extension in E group. Regarding AP location with flexion angle, there was no significant difference between two groups. In conclusion, there were different kinematics between flexion activities and extension activities.

Purpose

This study was to investigate the effect of posterior tibial slope (PTS) on the kinematics in the cruciate-retaining total knee arthroplasty (CR-TKA) using 2- to 3- dimensional registration technique.

Aims

In Asia and the Middle-East, people often flex their knees deeply in order to perform activities of daily living. The purpose of this study was to investigate the 3D kinematics of normal knees during high-flexion activities. Our hypothesis was that the femorotibial rotation, varus-valgus angle, translations, and kinematic pathway of normal knees during high-flexion activities, varied according to activity.

We hypothesized that using the navigation system, intra-operative knee kinematics after implantation measured may predict that post-operative kinematic in activities of daily living. Our aim was to compare intra-operative knee kinematics by a computed tomography (CT)-based navigation system and post-operative by the 2- to 3-dimensional registration techniques (2D3D).

This study were performed for 8 patients (10 knees, medial osteoarthritis) who underwent primary PS TKA using CT-based navigation system. The median follow-up period from operation date to fluoroscopic surveillance date was 13 months (range 5 – 37 months). Navigation and 2D3D had a common coordinate origin for components. Medial and lateral femoral condyle anterior-posterior translation (MFT and LFT) were respectively defined as the distance of the projection of the points (which was set on the top of the posterior femoral pegs) onto the axial plane of the tibial coordinate system. Intraoperative kinematics was measured using the navigation system after final implantation and closure of the retinaculum during passive full flexion and extension imposed by the surgeon. Under fluoroscopic surveillance in the sagittal plane, each patient was asked to perform sequential deep knee flexion under both weight bearing (WB) and non-weight bearing (NWB) conditions from full extension to maximum flexion. Repeated two-way ANOVA (tasks × flexion angles) were used, and then post-hoc test (paired t-tests with Boferroni correction) were performed. The level of statistical significant difference was set at 0.05 on two-way ANOVAs and 0.05 / 3 on post-hoc paired t-tests.

Mean range of motion between femoral and tibial components were Intra-operative (Intra): 28.0 ± 9.7, NWB conditions: 120.6 ± 11.1, WB conditions: 125.1 ± 12.9°, respectively. Mean ER (+) / IR (−) from 0° to 120° were Intra-operative (Intra): 9.3 ± 10.2°, NWB conditions: 8.1 ± 8.9, WB conditions: 5.2 ± 7.0, respectively. Mean MFT /LFT from 0° to 90° were Intra; 4.4 ±14.8/ 4.2± 8.5mm, NWB; 6.2 ± 6.9 / 9.2 ± 3.1 mm, WB; 9.2 ± 3.5 / 7.4 ± 2.8 mm, respectively. Mean MFT /LFT from 90° to 120° were Intra; −4.4 ± 2.5 / −5.7 ± 2.9 mm, NWB; −5.5 ± 1.8 / −8.2 ± 0.6 mm, WB; −4.0 ± 1.9 / −5.4 ± 2.3mm, respectively. Mean ADD/ABD from 0° to 120° were Intra;-4.2 ± 3.0, NWB; −0.2 ± 2.1, WB; −0.1 ± 0.8, respectively. Repeated two-way ANOVA showed a significant all interaction on kinematic variables (p<0.05). No statistically significant difference at post-hoc test was found in ER/ IR of all tasks and MFT /LFT of Intra vs NWB and Intra vs WB from 0° to 120° (p>0.05 / 3).

The Conditions of these tasks were different from each others. Our study demonstrated that intra-operative kinematics could predict post-operative kinematics.

The purpose of this study is to investigate the three-dimensional (3D) kinematics of normal knees in deep knee-bending motions like squatting and kneeling.

Material & Methods: We investigated the in vivo kinematics of 4 Japanese healthy male volunteers (8 normal knees in squatting, 7 normal knees in kneeling). Each sequential motion was performed under fluoroscopic surveillance in the sagittal plane. Femorotibial motion was analyzed using 2D/3D registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femur and tibia from single-view fluoroscopic images. We evaluated the femoral rotation relative to the tibia and anteroposterior (AP) translation of the femoral sulcus and lateral epicondyle on the plane perpendicular to the tibial mechanical axis. Student's t test was used to analyze differences in the absolute value of axial rotation and AP translation of the femoral sulcus and lateral epicondyle during squatting and kneeling. Values of P < 0.05 were considered statistically significant.

During squatting, knees were gradually flexed from −2.8 ± 1.3° to 145.5 ± 5.1° on average. Knees were gradually flexed from 100.8 ± 3.9° to 155.6 ± 3.2° on average during kneeling. Femurs during squatting displayed sharp external rotation relative to the tibia from 0° to 30° of flexion and it reached 12.5 ± 3.3° on average. From 30° to 130° of flexion, the femoral external rotation showed gradually, and it reached 19.1 ± 7.3° on average. From 130° to 140° of flexion, it was observed additionally, and reached 22.4 ± 6.1° on average. All kneeling knees displayed femoral external rotation relative to the tibia sharply from 100° to 150° of flexion, and it reached 20.7 ± 7.5° on average. From 100° to 120° of flexion, the femoral external rotation during squatting was larger than that during kneeling significantly. From 120° to 140° of flexion, there was no significant difference between squatting and kneeling. The sulcus during squatting moved 4.1 ± 4.8 mm anterior from 0° to 60° of flexion. From 60° of flexion it moved 13.6 ± 13.4 mm posterior. The sulcus during kneeling was not indicated significant movement with the knee flexion. The lateral epicondyle during squatting moved 39.4 ± 7.7 mm posterior from 0° to 140° of flexion. The lateral epicondyle during kneeling moved 22.0 ± 5.4 mm posterior movement from 100° to 150° of flexion. In AP translation of the sulcus from 100° to 140° of flexion, there was no significant difference between squatting and kneeling. However in that of the lateral epicondyle, squatting groups moved posterior significantly.

Even if they were same deep knee-bending, the kinematics were different because of the differences of daily motions. The results in this study demonstrated that in vivo kinematics of deep knee-bending were different between squatting and kneeling.

Introduction

Posterior cruciate ligament (PCL) preservation in total knee arthroplasty (TKA) is adovocated on the grounds that it provides better restoration of knee joint kinematics as opposed to PCL sacrifice. Mobile-bearing (MB) total knee prostheses have been in the market for a long time, but the PFC-Sigma Rotating Platform (RP) prosthesis (DePuy Orthopaedics, Inc, Warsaw, Ind) has been introduced in the market since 2000. Since, little is known about the in vivo kinematics of MB prostheses especially with cruciate retaining (CR). The objective of this study is to investigate the in vivo kinematics of MB RP-CR total knee arthroplasty during weight-bearing deep knee bending motion.

Patella resection has been the least controlled element of total knee arthroplasty (TKA). We have developed an intraoperative guide system involving a custom-made surgical template designed on the basis of a three-dimensional computer simulation incorporating computed tomography (CT) data for several years. This time we have applied this intraoperative guide system for the patella resection in TKA. We investigated the accuracy of CT-based patient-specific templating (PST) for patella resection using cadaveric knee joints in vitro.

To plan the corrective patella resection, we attempted to simulate a three-dimensional patella resection with the use of computer models of the patella. From CT images of the patella we obtained three-dimensional surface models of the patella by performing a three-dimensional surface generation of the bone cortex. After the patella resection using CT-based custom-made surgical templating instrumentation, CT scan was performed again and we compared the patella shape in three-dimensional patella bone model reconstructed from pre and after cut from CT data. We compared the accuracy of patella cut using three-dimensional patella bone model reconstructed from pre and after cut from CT data. Statistical analysis was performed using paired t test.

The difference between patella cut with CT-based custom-made surgical templating instrumentation and pre-operative planning were 0.8±1.2mm (medial side) and 0.1±1.4mm (lateral side). More than 60% resulted within 2mm from the pre-operative planning. There were significant differences both in flexion/extension, external/internal rotation and bone cut depth between CT-based custom-made surgical templating instrumentation and conventional instrument.

The results in this study demonstrated the usefulness of CT-based custom-made surgical templating instrumentation for patella resection in TKA.

Summary

The effect of the geometry of the tibial polyethylene insert was investigated in vivo loaded conditions.

Introduction

Regarding TKA, patient specific cutting guides (PSCG), which have the same fitting surface with patient's bones or cartilages and uniquely specify the resection plane by fitting guides with bones, have been developed to assist easy, low cost and accurate surgery. They have already been used clinically in Europe and the USA. However little has been reported on clinical positioning accuracy of PSCG. Generally, the methods of making PSCG can be divided into 3 methods; construct 3D bone models with Magnetic Resonance (MR) images, construct 3D bone models with Computed Tomography (CT) images, and the last is to construct 3D bone models with both MR and CT images. In the present study, PSCG were made based on 3D bone models with CT images, examined the positioning accuracy with fresh-frozen cadavers.

Background

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 Low Contact Stress total knee arthroplasty (LCS TKA) in weight bearing deep knee flexion using 2D/3D registration technique.

Background

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.

Background

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.

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.

Results: The mean range of hyper-extension was 2.1° and the mean range of flexion of 121.2°. The femoral component relative to the tibial component demonstrated 10.4° external rotation for 0–120 degrees flexion. The tibial component rotated 10.2° externally relative to the PE and the femoral component minimally rotated relative to the PE within ± 5 degrees. In upright standing position, the femoral component already rotated externally relative to the tibial component in 6.3°, and the PE also rotated on average 6.4° externally on the tibial tray. Typically the femoral component relative to the tibial component exhibited a central pivot pattern external rotation from extension to 80° knee flexion. Subsequently from 80 to 120°, bilateral condyles moved backward. In a similar fashion, the femoral component relative to the PE exhibited a central pivot pattern external rotation from extension to 70° knee flexion and subsequently bicondylar rollback from 70 to 120° knee flexion.

Discussion and Conclusion: In this study, we evaluated the in vivo motion of PE during squat motion. About this total knee prosthesis, the mobile-bearing mechanism which advantages over fixed-bearing prosthesis to reduce contact stress and keep high comformity might work well, and arc of range of motion was maintained. Furthermore, in upright standing position, the femoral component and tibial component already rotated externally relative to the PE in almost equal measure. This indicated that, self-aligning mechanism, another characteristic of the MB prosthesis might also work well.

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.

Introduction: Recently several retrieval reports of PS TKA have demonstrated that the wear and deformation can occur on the anterior tibial post and the hyperextension of femorotibial components was a pivotal factor in the mechanism of anterior tibial post impingement. The objective of this study was to investigate the in vivo mechanism of anterior tibial post impingement during gait in PS TKAs.

Methods: Twenty knees with PS TKAs implanted by single surgeon were assessed in this study. The Review Board Committee of the author’s institution approved this study and informed consent was obtained from all patients. In this study ten knees implanted with Scorpio NRG PS (Stryker Orthopedics, Mahwah, NJ) and ten knees implanted with NexGen Legacy-flex fixed (Zimmer, Warsaw, IN) were examined. Each patient was asked to perform treadmill gait under fluoroscopic surveillance in the sagittal plane. Treadmill gait speed was 0.5–1.0 m/s at Patients selected comfortable speed. Patients were explicitly encouraged to fully extend their knees at heel-strike and to avoid a shuffling gait pattern. Patients used light-touch hand-support to maintain the foot position on the treadmill. In vivo 3D poses of the knee prostheses were computed using a two- to three-dimensional (2D/3D) registration technique, which uses CAD models to reproduce spatial postures of the femoral and tibial components from calibrated single-view fluoroscopic images. We evaluated range of motion and the anterior-posterior (AP) translations between femoral and tibial inserts. The anterior tibial post impingement was determined when the proximity between tibial post and femoral cam is within the 0.5mm threshold.

Results: The maximum flexion during gait was 41.9° (25°–56°) in NRG and 42.3° (23°–59°) in Legacy-flex. The minimum flexion during gait was 1.5° (−9.2° − 8.4°) in NRG and 1.8° (−13.0° − 17.0°) in Legacy-flex. The AP translations of the medial and lateral contact points in stance phase were significantly larger in Legacy-flex compared with NRG (medial ; p=0.02,lateral ; p=0.007, Mann-Whitney’s U test). Anterior tibial post impingement was recognized in four knees implanted with Legacy-flex, and in two of three knees, the knee was not hyper extended. On the other hand, no impingement was recognized in knee implanted with NRG.

Discussion: In this study, the anterior tibial post impingement occurred not only in hyper extended knee but also in slightly flexed knee in Legacy-flex. One of the reasons why the anterior tibial post impingement was recognized in Legacy-flex was the large amount of the AP translation in stance phase. Posterior translation in stance phase may be one pivotal factor in the mechanism of the anterior tibial post impingement.

Background: 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 deep knee bending under weight-bearing conditions has not been clarified. The objective of this study is to clarify the in vivo motion of MB total knee arthroplasty including PE during weight-bearing deep knee bend motion.

Patients and methods: We investigated the in vivo knee kinematics of 9 knees (9 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.

Results: The mean range of hyper-extension was 2.1° and the mean range of flexion of 121.2°. The femoral component relative to the tibial component demonstrated 13.0° external rotation for 0–120 degrees flexion. The tibial component rotated 12.1° externally relative to the PE and the femoral component minimally rotated relative to the PE within ± 5 degrees. In upright standing position, the femoral component already rotated externally relative to the tibial component in 7.8°, and the PE also rotated on average 8.2° externally on the tibial tray. Typically the femoral component relative to the tibial component exhibited a central pivot pattern external rotation from extension to 80° knee flexion. Subsequently from 80 to 120°, bilateral condyles moved backward. In a similar fashion, the femoral component relative to the PE exhibited a central pivot pattern external rotation from extension to 70° knee flexion and subsequently bicondylar rollback from 70 to 120° knee flexion.

Discussion and conclusion: In this study, we evaluated the in vivo motion of PE during deep knee bend motion under weight-bearing condition. About this total knee prosthesis, the mobile-bearing mechanism which advantages over fixed-bearing prosthesis to reduce contact stress and keep high comformity might work well, and arc of range of motion was maintained. Furthermore, in upright standing position, the femoral component and tibial component already rotated externally relative to the PE in almost equal measure. This indicated that, self-aligning mechanism, another characteristic of the MB prosthesis might also work well.