The MediShoe (Promedics Orthopaedics Ltd, Glasgow) is a specific post-operative foot orthosis used by post-operative foot and ankle patients designed to protect fixations, wounds and maximise comfort. The use of rigid-soled shoes has been said to alter joint loading within the knee and with the popular use of the MediShoe at our centre in post operative foot and ankle surgery patients, it is important to ascertain whether this is also true. An analysis of the knee gait kinetics in healthy subjects wearing the MediShoe was carried out. Ten healthy subjects were investigated in a gait lab both during normal gait (control) and then with one shoe orthosis worn. Force plates and an optoelectronic motion capture system with retroreflective markers were used and placed on the subjects using a standardised referencing system. Three knee gait kinetic parameters were measured:- knee adduction moment; angle of action of the ground reaction force with respect to the ground in the coronal plane as well as the tibiofemoral angle. These were calculated with the Qualisys software package (Gothenburg, Sweden). A two-tailed paired t-test (95% CI) showed no significant difference between the control group and the shoe orthosis-fitted group for the knee adduction moment (p = 0.238) and insignificant changes with respect to the tibiofemoral angle (p = 0.4952) and the acting angle of the ground reaction force (p = 0.059). The MediShoe doesn't significantly alter knee gait kinetics in healthy patients. Further work, however is recommended before justifying its routine use

One of the main concerns about the currently available simulators is that the TKA is driven in a “passive way” for assessment. For the simulators for the wear assessment, the tibio-femoral relative motion is automatically made by using the knee kinematics and loading profile of a normal gait. As for the simulators for the kinematics and kinetics assessment of TKA, also the predicted loading profiles introduced from the theoretical model are applied as the input data to drive the simulator. It should be noted that the human joints are driven by the muscles' forces and external loads, and their kinematics and kinetics are the “outcome”. This being so, the knee simulator should be driven by the muscles' forces and upon these conditions the TKA performance is to be assessed. Some other concerns about the current simulations are as follows. The effects of hip joint motion are not taken into account. The upper body weight is applied along a vertical rod in such a way as a crank-slider. Furthermore, few simulators are capable of knee flexion greater than about 110°. Considering the above, we have developed a novel knee simulator which makes it possible to reproduce the active and natural knee motion to assess kinematics and kinetics of TKA. In the experiment, the custom-designed PS type TKA was attached and the simulator was operated so as to reproduce the sit-to-stand features, thereby introducing the tibio-femoral loading profiles during the motion. Figure 1 illustrates the external appearances of the simulator and a close view of the knee joint compartment. Since our simulator is composed of a multiple inverted pendulum, the knee part bears the upper body weight in a physiological way. The holder bracket is set to prevent the simulator from collapsing for security. The dimension and weight of each link were set as close as those of each segment of a normal male subject. Our simulator is driven by the wire pull mechanism which substitutes the human musculo-skeletal system of lower limb. Figure 2 shows close views of tibial tray with load cells. In Fig.2a, cell FR, FC and FL are to measure the tangential components of tibio-femoral contact force, i.e., the Anterio-Posterior force (AP force). The rest five cells are to measure the normal components of tibio-femoral contact force (normal force). As shown in Fig.2c, the tibial insert of TKA is mounted on the lid of the tibial tray box. In the experiment, a PS type TKA whose maximum flexion angle of 150° was attached to the simulator for evaluation. The simulator was operated so as to reproduce the sit-to-stand features and the data concerning about the AP force, Ft, and the normal force, Fn were recorded. Figure 3 shows the variations of knee flexion angles and knee contact forces respectively as a function of normalized time. Our knee simulator may have a potential for substituting the in vivo measurement

We have developed a novel knee simulator that reproduces the active knee motion to evaluate kinematics and joint reaction forces of TKA. There have been developed many kinds of knee simulators; Most of them are to predict TKA component wear and the others are to evaluate the kinematics and/or kinetics of TKA. The most simulators have been operated using the data of the loading and kinematics profile of the knee obtained from normal gait. Here a problem is that such variables as joint force and kinematics are the outcome caused by the application of muscles' and external forces. If so, a simulator should be operated by the muscles' and external forces so as to duplicate the in vivo condition. Other disadvantages for the current knee simulators are; a knee joint motion is made passively, the effects of the hip joint motion are not taken into account, and the maximum flexion angle is usually limited at about 100°. Considering the above, we have developed a knee simulator with the following advantages and innovative features. First, the simulator is driven by the muscles' forces and an active knee motion is made with bearing the upper body weight. As a result, the knee shows a 3D kinematics and generates the tibio-femoral contact forces. Under this condition, the TKA performance is to be assessed. Secondly, a hip joint mechanism is also incorporated into the simulator. The lower limb motion is achieved by the synergistic function between the hip and knee joints. Under this condition, a natural knee motion is to be reproduced. Thirdly, the simulator can make complete deep knee flexion up to 180°. Thus not only the conventional TKA but also a new TKA for high flexion can be attached to it for the evaluation. Figure 1 shows the structure of the simulator, in which both the hip and knee joints are moved in a synergistic fashion by the pull forces of four wires. The four wires are pulled by the four servomotors respectively and reproduce the functions of the mono-articular muscles ((1), (3)) and the bi-articular muscles ((2), (4)) through the multiple pulley system. It should be noted that weight A and B are not heavy enough for the inverted double pendulum to stand up straight. They are applied as counter weights so that each segment duplicate the each segmental weight of the human lower limb. Figure 2 shows a sequential representation of stand to sit features: (a) at standing, (b) at high flexion, and (c) at deep flexion. At a state of 130° knee flexion between (b) and (c), hamstrings wire (4) becomes shortest and then exhibits an eccentric contraction, thereby attaining deep flexion. Our knee simulator can be a useful tool for the evaluation of TKA performance and may potentially substitute the in vivo experiments

Introduction. A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). As a closed chain exercise, it has great value in rehabilitation and muscle strengthening of hip and knee. During DS, the hip flexion angle approximates the functional range of hip motion risking femoroacetabular impingement in some morphologies. In-vivo HJRF measurements have been limited to instrumented implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). On the other hand, total hip arthroplasty is being increasingly performed in a younger and higher demanding patient population. These patients clearly have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since measurements of HJRF with instrumented prostheses in healthy subjects would be ethically unfeasible, this study aims to report a personalised numerical solution based on inverse dynamics to calculate realistic in-silico HJRF values during DS. Material and methods. Thirty-five healthy males (18–25 years old) were prospectively recruited for motion and morphological analysis. DS motion capture (MoCap) acquisitions and MRI scans with gait lab marker positions were obtained. The AnyBody Modelling System (v6.1.1) was used to implement a novel personalisation workflow of the AnyMoCap template model. Bone geometries, semi-automatically segmented from MRI, and corresponding markers were incorporated into the template human model by an automated procedure. A state of-the-art TLEM 2.0 dataset, included in the Anybody Managed Model Repository (v2.0), was used in the template model. The subject-specific MoCap trials were processed to compute kinematics of DS, muscle and joint reaction forces in the entire body. Resulting hip joint loads were compared with in-vivo data from OrthoLoad dataset. Additionally, hip and knee joint angles were computed. Results. An average HJRF of 274%BW (251.5 – 297.9%BW; 95% confidence interval) was calculated at the peak of DS. The HJRF on the pelvis was directed superior, medial and posterior throughout the DS. Peak knee and hip flexion angles were 112° (108.1° – 116.5°) and 107° (104.6° – 109.4°) on average. Discussion and conclusions. A comprehensive approach to construct an accurate personalised musculoskeletal model from subject-specific MoCap data, bone geometries, and palpatory landmarks was presented. Consistently higher HJR forces during DS in young adults were demonstrated as opposed to the Orthoload dataset. Similarly, knee and hip flexion angles were much higher, which could cause the increase in HJRF. It can be concluded that DS kinetics in young adults differ from the typical total hip arthroplasty population. These models will enable further in-silico joint biomechanics studies, and could serve the purpose of a virtual test bed for implant design

INTRODUCTION

Multiple video fluoroscopic analyses have been performed to determine the in vivo kinematic patterns of total knee arthroplasty (TKA) and non implanted knees. Unfortunately, many of these studies were not correlated with bearing surface forces and possible failure modes that could be detected with a sound sensor. Therefore, the objective of the present study was to conduct a comparative analysis of the kinematic data derived for all subjects having a TKA who were analyzed over the past seventeen years at our laboratory and to determine how these patterns correlate with bearing surface forces and joint sound.

Introduction:

This study evaluates the impact of radii-related differences in posterior cruciate ligament retaining (PCR) primary total knee arthroplasty (TKA) prosthetic designs on knee biomechanics during level walking 1-year after surgery. The multi-radius (MR) design creates at least two instantaneous flexion axes by changing the radius of curvature of the femoral component throughout the arc of knee motion. The femoral component of the single-radius (SR) design has only one radius and therefore a fixed axis.

INTRODUCTION. While computational models have been used for many years to contribute to pre-clinical, design phase iterations of total knee replacement implants, the analysis time required has limited the real-time use as required for other applications, such as in patient-specific surgical alignment in the operating room. In this environment, the impact of variation in ligament balance and implant alignment on estimated joint mechanics must be available instantaneously. As neural networks (NN) have shown the ability to appropriately represent dynamic systems, the objective of this preliminary study was to evaluate deep learning to represent the joint level kinetic and kinematic results from a validated finite element lower limb model with varied surgical alignment. METHODS. External hip and ankle boundary conditions were created for a previously-developed finite element lower limb model [1] for step down (SD), deep knee bend (DKB) and gait to best reproduce in-vivo loading conditions as measured on patients with the Innex knee (. orthoload.com. ) (Figure1). These boundary conditions were subsequently used as inputs for the model with a current fixed-bearing total knee replacement to estimate implant-specific kinetics and kinematics during activities of daily living. Implant alignments were varied, including variation of the hip-knee-ankle angle-±3°, the frontal plane joint line −7° to +5°, internal-external femoral rotation ±3°, and the tibial posterior slope 5° and 0°. Through varying these parameters a total of 2464 simulations were completed. A NN was created utilizing the NN toolbox in MATLAB. Sequence data inputs were produced from the alignment and the external boundary conditions for each activity cycle. Sequence outputs for the model were the 6 degree of freedom kinetics and kinematics, totaling 12 outputs. All data was normalized across the entire data set. Ten percent of the simulation runs were removed at random from the training set to be used for validation, leaving 2220 simulations for training and 244 for validation. A nine-layer bi-long short-term memory (LSTM) NN was created to take advantage of bi-LSTM layers ability to learn from past and future data. Training on the network was undertaken using an RMSprop solver until the root mean square error (RMSE) stopped reducing. Evaluation of NN quality was determined by the RMSE of the validation set. RESULTS. The trained NN was able to effectively estimate the validation data. Average RMSE over the kinetics of the validation data set was 140.7N/N∗m while the average RMSE over the kinematics of the validation data set was 4.47mm/deg (Figure 2,3–DKB, Gait shown). It is noted the error may be skewed by the larger magnitude kinetics and kinematics in the DKB activity as the average RMSE for just SD and gait was 85.9N/N∗m and 2.8mm/deg for the kinetics and kinematics, respectively. DISCUSSION. The accuracy of the generated NN indicates its potential for use in real-time modeling, and further work will explore additional changes in post-operative soft-tissue balance as well as scaling to patient-specific geometry

Individuals with multi-compartment knee osteoarthritis (KOA) frequently experience challenges in activities of daily living (ADL) such as stair ambulation. The Levitation “Tri-Compartment Offloader” (TCO) knee brace was designed to reduce pain in individuals with multicompartment KOA. This brace uses novel spring technology to reduce tibiofemoral and patellofemoral forces via reduced quadriceps forces. Information on brace utility during stair ambulation is limited. This study evaluated the effect of the TCO during stair descent in patients with multicompartment KOA by assessing knee flexion moments (KFM), quadriceps activity and pain. Nine participants (6 male, age 61.4±8.1 yrs; BMI 30.4±4.0 kg/m2) were tested following informed consent. Participants had medial tibiofemoral and patellofemoral OA (Kellgren-Lawrence grades two to four) diagnosed by an orthopaedic surgeon. Joint kinetics and muscle activity were evaluated during stair descent to compare three bracing conditions: 1) without brace (OFF); 2) brace in low power (LOW); and 3) brace in high power (HIGH). The brace spring engages from 60° to 120° and 15° to 120° knee flexion in LOW and HIGH, respectively. Individual brace size and fit were adjusted by a trained researcher. Participants performed three trials of step-over-step stair descent for each bracing condition. Three-dimensional kinematics were acquired using an 8-camera motion capture system. Forty-one spherical reflective markers were attached to the skin (on each leg and pelvis segment) and 8 markers on the brace. Ground reaction forces and surface EMG from the vastus medialis (VM) and vastus lateralis (VL) were collected for the braced leg. Participants rated knee pain intensity performing the task following each bracing condition on a 10cm Visual Analog Scale ranging from “no pain” (0) to “worst imaginable pain” (100). Resultant brace and knee flexion angles and KFM were analysed during stair contact for the braced leg. The brace moment was determined using brace torque-angle curves and was subtracted from the calculated KFM. Resultant moments were normalized to bodyweight and height. Peak KFMs were calculated for the loading response (Peak1) and push-off (Peak2) phases of support. EMG signals were normalized and analysed during stair contact using wavelet analysis. Signal intensities were summed across wavelets and time to determine muscle power. Results were averaged across all 3 trials for each participant. Paired T-tests were used to determine differences between bracing conditions with a Bonferroni adjustment for multiple comparisons (α=0.025). Peak KFM was significantly lower compared to OFF with the brace worn in HIGH during the push-off phase (p Table 1: Average peak knee flexion moments, quadriceps muscle power and knee pain during stair descent in 3 brace conditions (n=9). Quadriceps activity, knee flexion moments and pain were significantly reduced with TCO brace wear during stair descent in KOA patients. These findings suggest that the TCO assists the quadriceps to reduce KFM and knee pain during stair descent. This is the first biomechanical evidence to support use of the TCO to reduce pain during an ADL that produces especially high knee forces and flexion moments. For any figures or tables, please contact the authors directly

Purpose. The purpose of this study was to clarify the relationship between the laxity of surrounding soft tissue and artificial joint kinetics during knee articulation, where total knee arthroplasty had been performed using ceramic LFA artificial knee joints (LFA-TKA below) from Japan Medical Materials (JMM). Materials Methods. The subjects of the study were 47 knees in 40 LFA-TKA recipients whose cooperation could be obtained. The CR type joint (posterior cruciate retention design) was used in 33 knees in 27 recipients and the PS type joint (posterior cruciate stabilizer design) was used in 14 knees in 13 recipients. OA patients received 30 CR type and 8 PS type joints while RA patients received 3 CR type and 6 PS type joints. For analysis of post surgery knee joint kinetics, using digital fluoroscopy, lateral images were taken of knee motion from a loaded squat position to the erect standing position. Using Knee Motion® software the imaging data was evaluated for 1) femoral rollback, 2) tibial axial rotation patterns, and 3) pivot center position, from analysis of lateral and medial condylar translation (femoral components) at the point of contact with the tibial insert, starting from the extended position. Subsequent imaging under medial-lateral and posteroanterior stress was performed to measure the medial-lateral dihedral angle changes and posteroanterior movement, and the relationship of those factors to the dynamic patterns was evaluated. Results. No definite tendency was noted in Rollback of the CR type femoral components and no relationship to the laxity of surrounding soft tissue was found. For PS type joints both medial and lateral movement (average±standard deviation) was 5.4±8.0 and 16.0±3.7 respectively so that significant rollback was noted when flexed past 120°. As for tibial axial rotation patterns, of CR type joints 48% rotated outward and 52% rotated inward while of the PS type joints 33% rotated outward and 67% rotated inward, such that no definite tendency was determined. As for the pivot center, among CR type joints 27% were medial, 42% were lateral and 33% were other, and among PS type joints 78% were medial, 14% lateral and 8% other, with large individual differences but no definite tendency. Stress imaging showed significantly greater medial-lateral dihedral angles for CR type joints, and equal posteroanterior movement for both CR and PS joints, but no clear relationship was found between the laxity of surrounding soft tissue and the kinetics of artificial knee joints. Discussion. Knees with degenerative and rheumatoid arthritis that do not exhibit normal kinetics prior to surgery are not uncommon. Then since the ACL must be sacrificed in the TKA process, knee area soft tissue balance is not uniform between cases. The possibility is suggested that artificial knee joint kinetics are influenced more significantly by factors other than the design of the implant. Conclusion. While rollback was verified with PS type LFA-TKA, there were such large individual differences for both PS and CR cases that normal knee kinetics were not reproducible

Introduction. Bicruciate-retaining (BiCR) total knee replacements (TKRs) were designed to improve implant performance; however, functional advantages during daily activity have yet to be demonstrated. Although level walking is a common way to analyze functionality, it has been shown to be a weak test for identifying gait abnormalities related to ACL pathologies. The goal of this study is to set up a functional motion analysis test that will examine the effects of the ACL in TKR patients by comparing knee kinematics, kinetics, and muscle activation patterns during level and downhill walking for patients with posterior-cruciate retaining (PCR) and BiCR TKRs. Methods. Motion and electromyography (EMG) data were collected simultaneously for 12 subjects (4/8 m/f, 64±11 years, 31.3±7.3 BMI, 6/6 right/left) with BiCR TKRs and 15 subjects (6/9 m/f, 67±7 years, 30.5±5.1 BMI, 4/11 right/left) with PCR TKRs during level and downhill walking using the point cluster marker set. Surface electrodes were placed on the vastus medialis obliquus (VMO), rectus femoris (RF), biceps femoris (BF), and semitendinosus (ST) muscles. EMG data are reported as percent relative voluntary contraction (%RVC), normalizing the signal during downhill walking to the mean maximum EMG value during level walking. Results. For level walking, there were no significant differences between groups in knee kinematics, kinetics, and EMG patterns. During downhill walking, subjects with BiCR implants showed significantly lower peak muscle activity in the VMO (73.9 ± 49.1%RVC for BiCR vs. 113 ± 24.0%RVC for PCR; p=0.045) and RF (96.0 ± 25.7%RVC for BiCR vs. 128 ± 28.6%RVC for PCR; p=0.018). There was also a trending higher knee peak flexion moment for the BiCR subjects (2.0 ± 0.6% BW*HT vs. 1.5 ± 0.6% BW*HT, p = .076), as well as significantly more knee flexion at heel strike (5.1 ± 4.7 degrees vs. 1.8 ± 2.8 degrees, p = 0.044) compared with the PCR group. Discussion. Retention of the ACL led to altered muscle recruitment during downhill walking in BiCR subjects compared with PCR subjects. In BiCR subjects, quadriceps activity was reduced during downhill walking compared to level walking. PCR subjects on average did not show this reduction, possibly in compensation for decreased knee stability. While there were only a few significant kinematic/kinetic differences, it appears that BiCR TKRs may offer some neuromuscular benefits during more strenuous tasks like downhill walking. In conclusion, level and downhill walking knee kinematics and kinetics together with the corresponding quadriceps and hamstrings EMG signals begin to build an overall picture of implant functionality during motion analysis testing

Introduction. Total hip arthroplasty (THA) is the most effective treatment modality for severe arthritis of the hip. Patients report excellent clinical and functional outcomes following THA, including subjective improvement in gait mechanics. However, few studies in the literature have outlined the impact of THA, as well as surgical approach, on gait kinetics and kinematics. Purpose. The purpose of this study was to determine the impact of surgical approach for THA on quantitative gait analysis. Methods. Thirty patients undergoing THA for primary osteoarthritis of the hip were assigned to one of three surgical approaches (10 anterior, 10 posterior, and 10 lateral). A single surgeon performed each individual approach. Each patient received standardized implants at the time of surgery (cementless stem and acetabular component, cobalt chrome femoral head, highly cross-linked liner). Patients underwent 3D gait analysis pre-operatively, and at 6- and 12-weeks following the procedure. At each time point, temporal gait parameters, kinetics, and kinematics were compared. Statistical analysis was performed using one-way analysis of variance. Results. All three groups were similar with respect to age (p=0.27), body mass index (p=0.16), and the Charlson Comorbidity Index (p=0.66). Temporal parameters including step length, stride length, gait velocity, and percent stance and swing phase were similar between the groups at all time points. The lateral cohort had higher pelvic tilt during stance on the affected leg than the anterior cohort at 6-weeks (p=0.033). Affected leg ipsilateral trunk lean during stance was higher in the lateral group at 6-weeks (p=0.006) and 12-weeks (p=0.037) compared to the other cohorts. The anterior and posterior groups demonstrated an increased external rotation moment at 6-weeks (p=0.001) and 12-weeks (p=0.005) compared to the lateral group. Discussion. Although temporal parameters were similar across all groups, some differences in gait kinematics and kinetics exist following THA using different surgical approaches. However, the clinical relevance based on the small magnitude of the differences remains in question

Total hip arthroplasty (THA) is the most effective treatment modality for severe arthritis of the hip. Patients report excellent clinical and functional outcomes following THA, including subjective improvement in gait mechanics. However, few studies in the literature have outlined the impact of surgical approach on gait kinetics and kinematics. The purpose of this study was to determine the impact of surgical approach for THA on quantitative gait analysis. Thirty patients undergoing THA for primary osteoarthritis of the hip were assigned to one of three surgical approaches (10 anterior, 10 posterior, and 10 lateral). A single surgeon performed each individual approach. Each patient received standardised implants at the time of surgery (cementless stem and acetabular component, cobalt chrome femoral head, highly cross-linked liner). Patients underwent 3D gait analysis pre-operatively, and at 6- and 12-weeks following the procedure. At each time point, temporal gait parameters, kinetics, and kinematics were compared. Statistical analysis was performed using one-way analysis of variance. All three groups were similar with respect to age (p=0.27), body mass index (p=0.16), and the Charlson Comorbidity Index (p=0.66). Temporal parameters including step length, stride length, gait velocity, and percent stance and swing phase were similar between the groups at all time points. The lateral cohort had higher pelvic tilt during stance on the affected leg than the anterior cohort at 6-weeks (p=0.033). Affected leg ipsilateral trunk lean during stance was higher in the lateral group at 6-weeks (p=0.006) and 12-weeks (p=0.037) compared to the other cohorts. The anterior and posterior groups demonstrated an increased external rotation moment at 6-weeks (p=0.001) and 12-weeks (p=0.005) compared to the lateral group. Although temporal parameters were similar across all groups, some differences in gait kinematics and kinetics exist following THA using different surgical approaches. However, the clinical relevance based on the small magnitude of the differences remains in question

With the growing number of individuals with asymptomatic cam-type deformities, elevated alpha angles alone do not always explain clinical signs of femoroacetabular impingement (FAI). Differences in additional anatomical parameters may affect hip joint mechanics, altering the pathomechanical process resulting in symptomatic FAI. The purpose was to examine the association between anatomical hip joint parameters and kinematics and kinetics variables, during level walking. Fifty participants (m = 46, f = 4; age = 34 ± 7 years; BMI = 26 ± 4 kg/m²) underwent CT imaging and were diagnosed as either: symptomatic (15), if they showed a cam deformity and clinical signs; asymptomatic (19), if they showed a cam deformity, but no clinical signs; or control (16), if they showed no cam deformity and no clinical signs. Each participant's CT data was measured for: axial and radial alpha angles, femoral head-neck offset, femoral neck-shaft angle, medial proximal femoral angle, femoral torsion, acetabular version, and centre-edge angle. Participants performed level walking trials, which were recorded using a ten-camera motion capture system (Vicon MX-13, Oxford, UK) and two force plates (Bertec FP4060–08, Columbus, OH, USA). Peak sagittal and frontal hip joint angles, range of motion, and moments were calculated using a custom programming script (MATLAB R2015b, Natick, MA, USA). A one-way, between groups ANOVA examined differences among kinematics and kinetics variables (α = 0.05), using statistics software (IBM SPSS v.23, Armonk, NY, USA); while a stepwise multiple regression analysis examined associations between anatomical parameters and kinematics and kinetics variables. No significant differences in kinematics were observed between groups. The symptomatic group demonstrated lower peak hip abduction moments (0.12 ± 0.08 Nm/kg) than the control group (0.22 ± 0.10 Nm/kg, p = 0.01). Sagittal hip range of motion showed a moderate, negative correlation with radial alpha angle (r = −0.33, p = 0.02), while peak hip abduction moment correlated with femoral neck-shaft angle (r = 0.36, p = 0.009) and negatively with femoral torsion (r = −0.36, p = 0.009). With peak hip abduction moment in the stepwise regression analysis, femoral torsion accounted for a variance of 13.3% (F(1, 48) = 7.38; p = 0.009), while together with femoral neck-shaft angle accounted for a total variance of 20.4% (R² change = 0.07, F(2, 47) = 6.01; p = 0.047). Although elevated radial alpha angles may have limited sagittal range of motion, the cam deformity parameters did not affect joint moments. Femoral neck-shaft angle and femoral torsion were significantly associated with peak hip abduction moment, suggesting that the insertion location of the abductor affects muscle's length and its resultant force vector. A varus neck angle, combined with severe femoral torsion, may ultimately influence muscle moment arms and hip mechanics in individuals with cam FAI

Meniscus tears in adult patients do not heal spontaneously and represent a risk factor for OA development. PDGF is well known as an enhancer of meniscal cell biosynthetic activity and also has chemotactic activity for mesenchymal cells. PDGF incorporation into scaffolds should be efficient for recruitment of cells to initiate repair in the injured meniscus. We recently developed decellularized meniscus sheet for use in the treatment of meniscus tears. The aim of this study is to examine the potential of PDGF-coated decellularized meniscus scaffold in mediating integrative healing by endogenous cell migration. Fresh bovine meniscus was chemically decellularized. Round sheets were made from the decellularized tissue. Heparin was covalently conjugated with decellularized meniscus scaffold (DMS). PDGF-BB was immobilized by binding to the heparin-conjugated DMS. In vitro, PDGF release kinetics was analyzed by ELISA. DMS was transplanted into the injured meniscus explants and cultured for 2 and 4 weeks. The numbers of migrated cells at the border between DMS and injured explant were counted on DAPI stained sections and PDGFRb expressing cells were counted after immunohistochemical staining. The newly produced ECM and collagen fiber alignment was detected by histology on Safranin-O and picrosirius red stained sections. The explants were also tested for tensile properties. PDGF release kinetics showed sustained slow release in heparin-conjugated DMS, with 11.2% release at day- 16th compared to 26.1% release from the DMS without heparin. Insertion of the PDGF-treated DMS into the meniscus tears in bovine meniscus explants led to the migration of endogenous meniscus cells to the defect zone. The migrated cells expressed PDGFRb and produced new ECM in the defect area. Safranin-O and pircrosirius red staining showed tissue integration between DMS and injured explants. Moreover, the higher concentration of PDGF promoted cell integration into the DMS. Tensile properties of injured explants treated with PDGF coated DMS were significantly higher than in DMS without PDGF. Heparin-conjugated DMS showed strong immobilization of PDGF, which was released slowly. PDGF coated DMS promoted migration of endogenous meniscus cells to the defect area and into the scaffold. New matrix was formed that bridged the space between the native meniscus and the scaffold and this was associated with improved biomechanical properties. The PDGF coated DMS is a novel, feasible and efficient approach for the treatment of meniscus tears

The vast majority of total hip replacements (THR) implanted today enable modularity by means of a tapered junction; based on the Morse taper design introduced for cutting tools in the 19. th. Century . 1. Morse-type tapers at the head-stem junction provide many benefits, key for a successful surgical outcome such as wider component selection and restoration of better biomechanics . 2. However, moving from mono-block to modular designs has not been without its issues. Fluid ingress and motion at the interface has led to a complex multifactorial degradation mechanism better known as fretting-corrosion . 3. Fretting-corrosion products created at the junction are commonly associated with adverse local tissue reactions . 4. . There is a wide variation in the taper junction of THR differing quite significantly from Morse's original design. Performance of the taper junction has been found to vary with different designs . 5,6. However, there is still a lack of common understanding of what design inputs makes a ‘good’ modular taper interface. The aim of this study was to better understand the links between implant design and fretting-corrosion initially focussing on the role of angular mismatch between male and female taper. A combination of experimental approaches with the aid of computational models to assist understanding has been adopted. A more descriptive understanding between taper design, engagement, motion and fretting-corrosion will be developed. Three different sample designs were created to represent the maximum range of possible angular mismatches seen in clinically available THR modular tapers (Matched: 0.020 ±0.002 °, Proximal: 0.127 ±0.016 °, Distal: −0.090 ±0.002 °). Head-stem components were assembled at 2 kN. Motion and fretting-corrosion at the interface was simulated under incremental uniaxial sinusoidal loading between 0.5–4 kN at 8 intervals of 600 cycles. The different types of motions at the interface was measured using a developed inductance circuit composed of four sensing coils, digital inductance converter chip (LDC1614, Texas Instruments, US) and microcontroller (myRIO, National Instruments, US). Fretting-corrosion was measured using potentiostatic electrochemical techniques with an over potential of +100 mV vs OCP (Ivium, NL). Complimentary finite element (FE) models were created in Ansys (Ansys 19.2, US). Under uniaxial loading, the ‘matched’ modular taper assemblies corroded most and allowed the greatest pistoning motion due to a seating action. ‘Distal’ and ‘proximal’ engaged modular tapers showed reduced corrosion and seating when compare to the ‘matched’ components. However the kinetics of corrosion and motion were interface dependent. It is hypothesized, and complimented by FEA analysis, that lower initial contact stress in the ‘matched’ modular tapers allows for greater subsidence and depassivation of the oxide layer and higher corrosion. ‘Matched’ modular tapers allowed less rotational and toggling motions compared to mismatched tapers, suggesting a reduced mismatch might perform better once the heads have seated over time. Future work involves tests conducted under a surgically relevant impaction force and physiological loading kinematics to develop this descriptive link between taper design, engagement and performance

Thigh-calf contact force is the force acting on posterior side of the thigh and calf during deep knee flexion. It has been reported the force is important to analyze the kinetics of a lower limb and a knee joint. Some previous researches reported the measured thigh-calf contact force, however, the values varied among the reports. Furthermore, the reports indicated that there were large variations even in a single report. One of the reports tried to find the relationship between the magnitude of thigh-calf contact force and anthropometric measurement as height, weight or perimeter of the lower limb, however, there could not found clear correlations. We considered that the cause of the variations might be the difference of the posture. At heel-rise squatting posture, we can bend or stand upright the upper body. Therefore we tried to create the equation to estimate the thigh-calf contact force by multiple regression analysis, using the anthropometric and posture parameters as explanatory variables. We performed the experiment to measure thigh-calf contact force, joint angles and anthropometric information. Test subjects were 10 healthy male. First we measured their height, weight, perimeter of the thigh and muscle mass of the legs and whole body. Muscle mass was measured by body composition meter (BC-118E, Tanita Co., Japan). Then, test subjects were asked to squat with their heels lifted and with putting the pressure distribution sensor between thigh and calf. And they bent their upper body forward and backward. The pressure sensor to be used was ConfroMat System (Nitta Co., Japan). After that, we measured the joint angles of the hip, knee and ankle, and the angle between the floor and upper body using the videos taken during the experiment. Then, we created the equation to estimate the thigh-calf contact force by linear combination of the anthropometric values and joint angles. The coefficients were settled as to minimize the average error between measured and estimated values. Results are shown in Fig.1. Forces were normalized by the body weight of the test subjects. Because the horizontal axes show the measured and vertical axis show the estimated values, the estimation is accurate when the plots are near the 45-degree line. Average error was 0.11BW by using only physical values, 0.15BW by angles and 0.06BW using both values. And the maximum error was 0.69BW, 0.43BW and 0.32BW respectively. Thus we could estimate the thigh-calf contact force by multiple regressions, using both physical parameters and angles to indicate the posture. Using the equation, we would be able to analyze the kinetics of a lower limb by physical and motion measurement. Our future work might be increasing the number of subjects to consider the appropriateness, because the test subjects of this study were very limited

Introduction. Optimal knee joint function obviously requires a delicate balance between the osseous anatomy and the surrounding soft tissues, which is distorted in the case of joint line elevation (JLE). Although several studies have found no correlation between JLE and outcome, others have linked JLE to inferior results. The purpose of this in vitro investigation was to evaluate the effect of JLE on tibiofemoral kinematics and collateral ligament strains. Materials and Methods. Six cadaver knees were equipped with reflective markers on femur and tibia and CT scans were made. A total knee arthroplasty (TKA) was performed preserving the native joint level. The knees were then tested in passive flexion-extension and squatting in a knee kinematics simulator while marker positions were recorded with an optical system. During squatting quadriceps forces were measured as well as tibio-femoral contact pressures. Finally, a revision TKA was performed with JLE by 4 mm. The femoral component was downsized and a thicker insert was used. The knees were again tested as before. Based on the bony landmarks identified in the CT scans and the measured trajectories of the markers, relative tibiofemoral kinematics could be calculated as well as distance changes between insertions of the collateral ligaments. Statistical tests were carried out to detect significant differences in kinematic patterns, ligaments elongation, tibiofemoral contact pressures and quadriceps forces between the primary TKA and after JLE. Results. Tibiofemoral kinematics are shown in Figure 1. For both passive flexion and squatting, tibial external rotation and adduction were similar before and after JLE. In passive flexion, JLE decreased the posterior translation of the femoral medial and lateral condyle centres, especially beyond 40 degrees of flexion. A slight 5% anterior shift of both centres was noted after JLE during squatting, but this was not significant. Strains in the collateral ligaments are shown in Figure 2. The collateral ligament lengths remained constant during passive flexion and were unaffected by elevation of the joint line. During squatting, the sMCL stretched with flexion after primary TKA and this behaviour stayed constant when the joint line was elevated. The LCL showed a similar loosening trend in both TKA configurations. Also tibiofemoral joint kinetics were not affected by JLE: quadriceps force and contact pressures all remained essentially unchanged during squatting before and after JLE. Discussion and conclusion. Although clinical observations have indicated that JLE is associated with inferior clinical results, the effects of JLE on knee biomechanics which might explain these outcomes remain relatively unknown. In this study, we specifically evaluated those effects on tibiofemoral kinematics and kinetics, as well as elongation of the collateral ligaments. As our current study did not detect any effect of JLE in tibiofemoral kinematics, kinetics, and strains of collateral ligaments in revision TKA, it is possible that these effects may be limited to or triggered at the patello-femoral joint, and more significant with higher joint line elevations than the 4-mm level tested in the current study. This hypothesis needs to be further investigated in future in-vitro and in-vivo studies

Aim. The demonstration of the in vivo bactericidal efficacy of a new bone cement with rifampicin contained in microcapsules and its intra-articular release profile. Method. Fifteen New Zealand White rabbits were employed to reproduce periprosthetic infection by intra-articular inoculation of 10. 5. CFU/mL of Staphylococcus aureus ATCC® 29213 using as a target implant a 3D printed stainless steel tibial insert. 7 days after inoculation, the first stage of the two stage exchange was carried out and at this time the animals were divided into two study groups: group C (7 rabbits) that received a spacer with gentamicin and group R (8 rabbits) that received a spacer with gentamicin and rifampicin microcapsules. Response to infection was monitored by clinical (weight and temperature), hematological (leukocyte, lymphocyte and platelet counts) and biochemical (erythrocyte sedimentation rate) analyses at the time of inoculation, at the first stage of exchange, 4 days after first stage and weekly until the fourth week when animals were euthanized. Microbiological counts were performed at the first stage of exchange and at the end of the study. Results. 14/15 animals (93.3%) developed a PJI 1 week after the inoculation. A statistically significant elevation of the leukocyte and platelet count and a decrease in the percentage of lymphocytes (p=0.0001) was found and positive microbiological cultures. Four weeks after the placement of the spacer, no bacterial growth was found in the soft tissue or bone samples of the group with rifampicin microcapsules (group R), being these differences statistically significant with p=0.01 and 0.03 respectively. The rifampicin intra-articular release kinetics showed concentrations above the staphylococcal MIC at all time points. Conclusions. The bone cement with microencapsulated rifampicin is effective in the in vivo treatment of prosthetic joint infection due to biofilm-forming S. aureus

Power production in the terminal stance phase is essential for propelling the body forward during walking and is generated primarily by ankle plantarflexion. Osteoarthritis (OA) of the ankle restricts joint range of motion and is expected to reduce power production at that ankle. This loss of power may be compensated for by unaffected joints on both the ipsilateral and contralateral limbs resulting in overloading of the asymptomatic joints. Total ankle arthroplasty (TAA) has been shown to reduce pain and has the potential to restore range of motion and therefore increase ankle joint power, which could reduce overloading of the unaffected joints and increase walking speed. The purpose of this study was to test the hypothesis that ankle OA causes a loss of power in the affected ankle, compensatory power changes in unaffected lower limb joints, and that TAA will increase ankle power in the repaired ankle and reduce compensatory changes in other joints. One hundred and eighty-three patients (86 men, 97 women with average ages 64.1 and 62.4 years respectively) requiring surgical intervention for ankle OA were prospectively enrolled. Implant selection of either a fixed (INBONE or Salto Talaris) or mobile (STAR) bearing implant was based on surgeon preference. Three-dimensional kinematics and kinetics were collected prior to surgery and one year post-operatively during self-selected speed level walking using an eight-camera motion capture system and a series of force platforms. Subject walking speed and lower extremity joint power during the last third of stance at the ankle, knee, and hip were calculated bilaterally and compared before and after surgical intervention across the entire group and by implant type (fixed vs. mobile), and gender using a series of ANOVAs (JMP SAS, Cary, NC), with statistical significance defined as p < 0 .05. There were no gender differences in age, walking speed, or joint power. All patients increased walking as a result of surgery (0.87 m/s±0.26 prior to surgery and 1.13 m/s±0.24 after surgery, p < 0 .001) and increased total limb power. Normalized to total power (which accounts for changes in speed and distribution of power production across joints), prior to surgery the affected ankle contributed 19%±10% of total power while the unaffected ankle contributed 42%±12% (P < 0 .001). After surgery, the affected ankle increased to 25%±9% of total power and the unaffected ankle decreased to 38%±9% of total (P < 0.001). Other joints showed no significant power changes following surgery. Fixed bearing implants provide greater surgical ankle power improvement (61% versus 29% increase, p < 0 .002). Much of that change was due to the fact that those that received fixed-bearing implants had significantly lower walking speed and power before surgery. Ankle OA reduced ankle power production, which was partially compensated for by the unaffected ankle. TAA increases walking speed and power at the affected ankle while lowering power production on the unaffected side. The modifications in power production could lead to increased physical activity and reduced overloading of asymptomatic joints

Introduction. Preservation of the anterior cruciate ligament (ACL), along with the posterior cruciate ligament, is believed to improve functional outcomes in total knee replacement (TKR). The purpose of this study was to examine gait differences and muscle activation levels between ACL sacrificing (ACL-S) and bicruciate retaining (BCR) TKR subjects during level walking, downhill walking, and stair climbing. Methods. Ten ACL-S (Vanguard CR) (69±8 yrs, 28.7±4.7 kg/m2) and eleven BCR (Vanguard XP, Zimmer-Biomet) (63±11 yrs, 31.0±7.6 kg/m2) subjects participated in this IRB approved study. Except for the condition of the ACL, both TKR designs were similar. Subjects were tested 8–14 months post-op in a motion analysis lab using a point cluster marker set and surface electrodes applied to the Vastus Medialis Oblique (VMO), Rectus Femoris (RF), Biceps Femoris (BF) and Semitendinosus (ST). 3D motion and force data and electromyography (EMG) data were collected simultaneously. Subjects were instructed to walk at a comfortable walking speed across a walkway, down a 12.5% downhill slope, and up a staircase. Five trials per activity were collected. Knee kinematics and kinetics were analyzed using BioMove (Stanford, Stanford, CA). The EMG dataset underwent full-wave rectification and was smoothed using a 300ms RMS window. Gait cycle was time normalized to 100%; relative voluntary contraction (RVC) was calculated by dividing the average activation during downhill walking by the maximum EMG value during level walking and multiplying by 100%. Results. There were no significant kinematic or kinetic differences between implant groups for level walking (p≥0.19). Both groups walked at 1.1 m/s on average during level and approximately 0.1 m/s slower during downhill walking, with no differences in speed (p= 0.91 and 0.77, respectively). For both ACL-S and BCR groups, gait changes from level to downhill walking were similar. For downhill walking, ACL-S subjects were significantly more variable (p<0.001) over the gait cycle for all measured kinematics and kinetics. During both downhill walking and stair climbing, the ACL-S group showed an external peak abduction moment (Fig. 1) significantly greater than that of the BCR group (p=0.05, 0.01). Also during stair climbing, ACL-S subjects showed trending higher peak knee adduction moments (p=0.14) and a more pronounced internal/external rotation pattern (Fig. 2) than BCR subjects. Since no peak kinematic/kinetic differences between groups during level walking exist, the mean maximum muscle activation from level walking was used for RVC normalization for other activities. On average, BCR subjects had lower maximum RVCs during downhill walking than the ACL-S subjects. Effect sizes were large for RF (d=0.94), ST (d=0.88), and VMO (d=1.21), the latter being borderline significant (p=0.05). Discussion. Previous studies on the natural knee have established that the ACL contains mechanoreceptors that improve stability of the knee joint. In this study, BCR subjects show less variable gait measures than subjects with traditional posterior cruciate retaining (ACL-S) TKR, possibly indicating more controlled contact kinematics. In addition, EMG results suggest lower muscle co-contraction during downhill walking, also implying greater knee stability in the BCR group. These results are preliminary and more subjects are needed for definite conclusions