Aims

This cross-sectional study aimed to investigate the in vivo ankle kinetic alterations in patients with concomitant chronic ankle instability (CAI) and osteochondral lesion of the talus (OLT), which may offer opportunities for clinician intervention in treatment and rehabilitation.

Aims. This study aimed to analyze kinematics and kinetics of the tibiofemoral joint in healthy subjects with valgus, neutral, and varus limb alignment throughout multiple gait activities using dynamic videofluoroscopy. Methods. Five subjects with valgus, 12 with neutral, and ten with varus limb alignment were assessed during multiple complete cycles of level walking, downhill walking, and stair descent using a combination of dynamic videofluoroscopy, ground reaction force plates, and optical motion capture. Following 2D/3D registration, tibiofemoral kinematics and kinetics were compared between the three limb alignment groups. Results. No significant differences for the rotational or translational patterns between the different limb alignment groups were found for level walking, downhill walking, or stair descent. Neutral and varus aligned subjects showed a mean centre of rotation located on the medial condyle for the loaded stance phase of all three gait activities. Valgus alignment, however, resulted in a centrally located centre of rotation for level and downhill walking, but a more medial centre of rotation during stair descent. Knee adduction/abduction moments were significantly influenced by limb alignment, with an increasing knee adduction moment from valgus through neutral to varus. Conclusion. Limb alignment was not reflected in the condylar kinematics, but did significantly affect the knee adduction moment. Variations in frontal plane limb alignment seem not to be a main modulator of condylar kinematics. The presented data provide insights into the influence of anatomical parameters on tibiofemoral kinematics and kinetics towards enhancing clinical decision-making and surgical restoration of natural knee joint motion and loading. Cite this article: Bone Joint Res 2024;13(9):485–496

Objectives. This study was conducted to evaluate the cytokine-release kinetics of platelet-rich plasma (PRP) according to different activation protocols. Methods. Two manual preparation procedures (single-spin (SS) at 900 g for five minutes; double-spin (DS) at 900 g for five minutes and then 1500 g for 15 minutes) were performed for each of 14 healthy subjects. Both preparations were tested for platelet activation by one of three activation protocols: no activation, activation with calcium (Ca) only, or calcium with a low dose (50 IU per 1 ml PRP) of thrombin. Each preparation was divided into four aliquots and incubated for one hour, 24 hours, 72 hours, and seven days. The cytokine-release kinetics were evaluated by assessing PDGF, TGF, VEGF, FGF, IL-1, and MMP-9 concentrations with bead-based sandwich immunoassay. Results. The concentration of cytokine released from PRP varied over time and was influenced by various activation protocols. Ca-only activation had a significant effect on the DS PRPs (where the VEGF, FGF, and IL-1 concentrations were sustained) while Ca/thrombin activation had effects on both SS and DS PRPs (where the PDGF and VEGF concentrations were sustained and the TGF and FGF concentrations were short). The IL-1 content showed a significant increase with Ca-only or Ca/thrombin activation while these activations did not increase the MMP-9 concentration. Conclusion. The SS and DS methods differed in their effect on cytokine release, and this effect varied among the cytokines analysed. In addition, low dose of thrombin/calcium activation increased the overall cytokine release of the PRP preparations over seven days, relative to that with a calcium-only supplement or non-activation. Cite this article: Professor J. H. Oh. Cytokine-release kinetics of platelet-rich plasma according to various activation protocols. Bone Joint Res 2016;5:37–45. doi: 10.1302/2046-3758.52.2000540

Abstract. Background. The aim of the present experimental study was to analyse vancomycin elution kinetics of nine bone fillers used in orthopaedic and trauma surgery over 42 consecutive days. Methods. Two allograft bone chips (carriers 1 and 2), a calcium-sulfate matrix (carrier 3), a hydroxyapatite/calcium-sulphate composite (carrier 4), four bone cements (carriers 5-8) and a pure tricalcium phosphate matrix (carrier 9), either already contained vancomycin, or were mixed with it following manufacturer's recommendations. Over 42 days, half of elution medium was substituted by the same amount of PBS at 9 distinct time points. Vancomycin concentration in obtained samples were measured with a kinetic microparticle immunoassay, and masses consecutively calculated. To enhance comparability between carriers analysed, vancomycin mass released related to overall mass within each probe was determined. Notably, elution kinetics of carriers 1 to 4 have been published previously. Results. All carriers initially released high vancomycin masses, followed by constant reduction later into the experiment. Mean initial vancomycin masses released after 4 hours were highest for carriers 1 (337.7 ± 76.2 mg), 9 (68.4 ± 4.9 mg), and 2 (49.0 ± 54.6 mg). From prefinal (35 days) to last measurement (42 days) carriers 2 (8.6 ± 4.8 mg), 1 (2.4 ± 1.0 mg), and 5 (0.1 ± 0.1 mg) had released highest vancomycin masses. Notably, all five bone cements tested only released a small percental amount of their total mass up to the last measurement (42 days; 2.1% – 9.3%), whilst allografts and resorbable synthetic bone fillers discarded high percental values (22.5% – 79.2%). Conclusions. Elution kinetics differ between 9 antibiotic-loaded bone fillers, with high vancomycin masses released by allografts and resorbable bone fillers over time. Transferred to clinical practice, these may be favoured over bone cements in case prolonged and high antibiotic release is warranted rather than mechanical stability

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

Hop tests are used to determine return to sports after ACL reconstruction. They mostly measure distance and symmetry but do not assess kinematics and kinetics. Recently, biomechanical evaluations have been incorporated into these functional jump tests for the better assessment of return to sport. We assessed the sagittal plane range of motion (ROM) of the knee, the deviation axis of rotation (DAOR), and the vertical ground reaction force (vGRF) normalized to body weight in nine healthy participants during the single leg (SLH) and crossover hop tests (COHT). Participants' leg lengths were measured. Jumping distances were marked in the test area as being 4/5 of the leg length. Four sensors were placed on the thighs, the legs and the feet. These body parts were handled as a single rigid body. Eight 480 Hz cameras were used to capture the movements of these rigid bodies. vGRF at landing were measured using a force plate (Bertec, Inc, USA). The ROM of the knee joint and the DAOR were obtained from kinematic data. Participants' joint kinematics metrics were similar in within-subjects statistical tests for SLH and COHT. We therefore asked whether the repeated vGRF normalized to body weight will be similar in both legs during these jumps. Joint kinematics metrics however were different in between subjects indicating the existence of a personalized jumping strategy. These hop tests can be recorded at the beginning of the training season for each individual, which can establish a comparative evaluation database for prospective lower extremity injury recovery and return to sport after ACL injury

Purpose: Dynamic MRI studies have confirmed the posterior displacement of the lateral condyle during flexion of the knee. Material and methods: We used bone morphing navigation equipment to study knee kinetics in cadaver specimens and determine the effect of ligament injury. Patellar movement was controlled with pins. Femur movement over the tibia was measured by the navigation system during knee flexion. Results: We noted external rotation of the femur during knee flexion when the tibia was maintained with the foot in the walking angle (15° with the flexion/extension plane), the femur being free to rotate. This rotation was nevertheless suppressed by constraining external rotation of the tibia. Unlocking rotation between −5° and +5° was measured between 8 and 10°. It was prolonged by greater rotation, increasing regularly with flexion to reach about 30° at 130° flexion. The computer display of the kinetics of the bony components demonstrated the posterior displacement of the lateral condyle. From 130° flexion, there was an elevation of the medial condyle which lost contact with the medial tibial plateau. Posterior displacement of the lateral condyle was confirmed by rotation of the patella in its longitudinal axis. The patella appeared to make a lateral translation movement to come in front of the lateral condyle at near complete flexion. It pulled the vastus medialis as is suggested by its movement around the anteroposterior axis. Section of the anterior cruciate ligament had little effect on the observed kinetics. It limited the unlocking rotation which did not exceed 3°. At about 110° the femoral rotation reached a plateau for about twenty degrees. The computer display illustrated the movement of the condyles showing that the movement of both was influenced by the posterior thigh soft tissue. Section of the popliteal muscle clearly lessened external rotation of the cadaveric knee. Discussion: Two types of movement can be described: – external rotation of the tibia at the end of extension due to the influence of the anterior cruciate ligament; – facultative external rotation of the femur during flexion under the control of the popliteal muscle. This is expressed during single leg stooping and could protect the patella from excessive pressure by progressively displacing the lateral condyle

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

Sex hormones play important roles in the regulation of the proliferation, maturation and death of chondrocytes in the epiphyseal growth plate. We have investigated the effects of male castration on the cell kinetics of chondrocytes as defined by the numbers of proliferating and dying cells. The growth plates of normal rabbits and animals castrated at eight weeks of age were obtained at 10, 15, 20 and 25 weeks of age. Our study suggested that castration led to an increase in apoptosis and a decrease in the proliferation of chondrocytes in the growth plate. In addition, the number of chondrocytes in the castrated rabbits was less than that of normal animals of the same age

Background. The doses of local rhBMP-2 in commercially available materials are high with known drawbacks such as inflammation and premature bone resorption. The latter can be prevented by adding bisphosphonates like zoledronic acid (ZA) but systemic ZA has side effects and patient adherence to treatment is low. In a recent study, we have shown that local co-delivery of rhBMP-2 and ZA via a calcium sulphate/hydroxyapatite (CS-HA) biomaterial can be used to regenerate both cortical and trabecular bone in a rat model of metaphyseal bone defect. Even low doses of local ZA in the biomaterial showed promising results and increased bone formation within the defect compared to the controls. A step before clinical translation of the local treatment regimen is to evaluate the in-vivo release kinetics of these additives and thus in this study, we aimed to investigate the in-vivo pharmacokinetics of rhBMP-2 and ZA from the CS-HA biomaterial in a rat abdominal muscle pouch model over a period of 4-weeks. Methods. In-vivo release kinetics of 125I labeled rhBMP-2 and 14C labeled ZA was performed using an abdominal muscle pouch model in rats (n=6). Both rhBMP-2 and ZA were labeled commercially with a radiochemical purity of >95%. The detection of 125I -rhBMP-2 release was performed by implanting pellets of the CS-HA biomaterial containing 125I -rhBMP-2 and ZA and the same animals followed over a period of 4-weeks (day 1, 3, 7, 14, 21& 28) using SPECT imaging. Similarly, the 14C-ZA was detected by implanting CS-HA pellets containing rhBMP-2 and 14C-ZA. Release was detected via scintillation counting and at each time point (Day 1, 7, 14& 28) 6-animals were sacrificed. Results. BMP Release. The CS-HA biomaterial retained 95±11% after 3-days, 88±12% after a week, 66±9% after 2 weeks, 51±5% after 3 weeks and 43±7% of 125I labeled rhBMP-2 after 4-weeks in-vivo (SPECT-CT). ZA Release. The CS-HA biomaterial retained 89±14% after a week, 84±8% after 2 weeks, 83±9% after 3 weeks and 77±3% of 14C labeled ZA after 4 weeks of in-vivo implantation. Discussion. Improved carriers and better knowledge of the release might improve the effect of bone active drugs in orthopedics. Our previous study shows that an off-the-shelf ceramic biomaterial combined with ZA alone or with both rhBMP-2 and ZA can be used to regenerate bone with potential for clinical translational. This study demonstrates long-term co-delivery of both rhBMP-2 and ZA in-vivo via the biomaterial. Constant availability of rhBMP-2 over a long period of time can give osteoinductive properties to the material while presence of local ZA prevents premature bone loss. The pharmacokinetic release pattern differs from what we have reported in vitro with less BMP and more ZA being released in vivo during the first 4 weeks. We speculate that rapid protein passivation of the ceramic material slows the release of BMP and partly preventing the ZA binding to apatite

Purpose: Use of a mobile tibial plateau for total knee arthroplasty (TKA) is designed to reduce wear and improve prosthetic kinetics. The purposes of this study were: 1) to compare the kinetics of a posterior stabilised TKA implanted with a fixed plateau (FP) or a mobile plateau (MP) and, 2) to determine whether the mobile plateau improves axial rotation. Material and methods: Ten patients with a unilateral TKA (HLS) with a fixed or mobile plateau were selected for this study according to the following criteria: arthroplasty for degenerative knee disease, healthy contralateral knee, age < 80 years, pain-free prosthesis, IKS > 80/100, flexion > 90°, follow-up > 1 year. There were five patients with a fixed plateau and five patients with the same prosthesis except with a mobile plateau. Knee movement (flexion-extension, axial rotation, valgus-varus) were measured with an electromagnetic goniometer on the implanted and healthy sides. Four movements were recorded: walking, standing up sitting down, flexion-extension without loading. Amplitudes were compared with non-parameteric statistical tests between the healthy side and the implanted side and between the two types of implants. Results: The FP knees were more mobile in valgus-varus due to greater residual frontal laxity than the MP knees. This extra laxity generated excessive axial rotation on the FP during non-loaded movements. Conversely, when loaded, axial rotation of the MP knees was 10° greater (mean, p < 0.05) than for the FP knees, giving better stability in the frontal plane. This study did not demonstrate any difference in flexion between FP and MP. Patients with an MP prosthesis did not have significantly different amplitudes of the three movements for the healthy versus implanted knee. For the patients with a FP prosthesis, axial rotation and frontal plane movement was lower in the implanted knee than in the healthy knee (p< à.05). Discussion: This study devoted to the design of a single prosthesis demonstrated the usefulness of the mobile plateau for axial rotation during loaded movement. The kinetics of MP prostheses is similar to that of the healthy knee. Better axial rotation with MP prostheses during loaded movements suggests the persistence of the plateau mobility which should be confirmed with a cinematographic study

This is a prospective gait laboratory case matched cohort study of patients after total knee arthroplasty. 20 patients who had TKA with a good functional result and a follow-up superior to 2 years were compared with 20 “normal” knees. The examiners were blinded to the group. A standardized gait analysis was performed, measuring gait kinematics, kinetics and force plate recordings using Motion Analysis computer software. All patients had a single surgeon and the same brand mobile bearing platform. The kinematics parameters were identical in both groups. However the dynamic parameters showed a statistically significant difference. At terminal swing and heel strike the operated patients had a 10-degree extension deficit in their gait analysis, despite of the fact that clinically all patients had a full extension with no quadriceps lag. The coronal plane kinetics of TKA showed valgus moment in stance despite having radiological normal (180° +/−1°) mechanical axis. (p< 0,02). In the axial plane, all operated patients had an external rotation moment greater than normals. (p< 0,01). Despite good clinical ROM and quadriceps strength, the TKA demonstrated a lack of extension in early stance. This may be due to insufficient extension gap at surgery. The valgus resultant pattern poses a more challenging question:. Are we aiming for the wrong goals in the mechanical axis, or should we consider undercorrection?. Gait analysis of the TKA patients compared to normals demonstrates dynamic differences in relation with the surgical positioning of the implant

Introduction. A deep squat (DS) is a challenging motion at the level of the hip joint generating substantial reaction forces (HJRF). During DS, the hip flexion angle approximates the functional range of hip motion. In some hip morphologies this femoroacetabular conflict has been shown to occur as early as 80° of hip flexion. So far in-vivo HJRF measurements have been limited to instrumented hip implants in a limited number of older patients performing incomplete squats (< 50° hip flexion and < 80° knee flexion). Clearly, young adults have a different kinetical profile with hip and knee flexion ranges going well over 100 degrees. Since hip loading data on this subgroup of the population is lacking and performing invasive measurements would be unfeasible, this study aimed to report a personalised numerical model solution based on inverse dynamics to calculate realistic in silico HJRF values during DS. M&M. Fifty athletic males (18–25 years old) were prospectively recruited for motion and morphological analysis. DS motion capture (MoCap) acquisitions and MRI scans of the lower extremities 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 nonlinear morphing. Furthermore, 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 squat motion by resolving an overdeterminate kinematics problem. Inverse dynamics analyses were carried out to compute muscle and joint reaction forces in the entire body. Resulting hip joint loads were validated with measured in-vivo data from Knee bend trials in the OrthoLoad library. Additionally, anterior pelvic tilt, hip and knee joint angles were computed. Results. A preliminary set of results (20 out of 50 subjects) was analysed. The average HJRF was 3.42 times bodyweight at the peak of DS (95% confidence interval: 2.99 – 3.85%BW). Maximal hip and knee flexion angles were 113° (109.7°–116.8°) and 116° (109.4 – 123.0°) respectively. The anterior pelvic tilt demonstrated a biphasic profile with peak value of 33° (28.1° – 38.4°). Discussion. A non-invasive and highly personalised alternative for determining hip loading 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 support the increase in HJRF. We can conclude that DS hip kinetics in young adults clearly differ from the typical total hip arthroplasty population

Successful total knee arthroplasty design is related to the joint dynamics imposed by the design. This study examined the clinical and biomechanical performance of patients who received a PFC Sigma total knee implant (posterior cruciate substituting design). Radiographic, strength testing, gait pattern and clinical survey data were collected. Pre-operative and post-operative outcome measures were compared. Statistically significant differences were found on the pain, stiffness and physical function scales of the WOMAC as well as the knee and total score parameters of the Knee Society Score. Significant improvements were also seen on several gait pattern parameters. Factors such as implant design and surgical technique have been found to influence knee kinematics and kinetics thereby effecting patient function and implant survival after total knee arthroplasty. Numerous gait studies have reported a lack of normal gait pattern for TKA patients (Wilson et al., 1996; Andriacchi, 1993; Jevsevar et al., 1993). There is debate in the literature as to which design best improves patient function and implant survival, the posterior cruciate (PC) substituting or PC-retaining. The purpose of this study is to determine the clinical outcome and biomechanical performance of patients who receive PFC Sigma total knee arthroplasty. The PC substituting implant design provided significant improvements in clinical and gait outcomes at two years post-op in this patient sample. Patients experience significant pain and stiffness relief, and better functional outcomes. A cohort of eighteen total knee replacement patients were followed for two years post-operatively. Radiographic, strength testing, gait pattern and clinical survey data (SF36, WOMAC, Knee Society Score) were collected. Paired sample t-tests, repeated measures general linear modeling and principle component analyses comparing aged matched normals were conducted to evaluate pre-operative and post-operative outcomes. Statistically significant differences were found on the pain, stiffness and physical function scales of the WOMAC as well as the knee and total score parameters of the Knee Society survey. There were also significant improvements found on gait pattern parameters. Findings like these point to a need for larger population studies of patients with PC-substituting TKA. Funding: Funding for this study was provided by Depuy Orthopaedics, Inc

Purpose: A significant increase in serum cobalt level has been reported after metal-on-metal total hip arthroplasty with wide individual variability related to activity level, mechanical conditions of the implant, and urinary elimination of cobalt. We studied serum cobalt levels over time to further analyse these factors. Material and methods: The Metazul® prosthesis was implanted in 119 patients (72 men and 47 women, 12 bilateral implantations) (131 implants). We selected 50 patients (27 men and 23 women, mean age 53 years) who had two blood samples after the procedure allowing an assessment of the serum cobalt kinetics. Other chromium-cobalt implants, vitamin B12 intake, renal failure, or haematological disorders were recorded. An activity questionnaire was filled out by the patients at the time of the blood sample. Samples were drawn with a special kit to avoid metal contamination. The detection limit was 1 nmol/L (0.06 μg/L) with direct electrothermic atomic spectrometric absorption. Results: In the overall series, serum cobalt level was 44 nmol/L for a physiological level in a control population of 4.28 nmol/L. The difference was significant (p < 0.0001) between the levels observed before surgery and after 18 months implantation. There was no significant correlation with the indication for arthroplasty, presence of dislocation or subdislocation, functional outcome or radiographic findings. Activity level the week before sampling did not influence the results. For the 50 cases evaluated longitudinally, four groups of patients could be identified. The first group (29 patients) had a serum cobalt level below 50 nmol/L over the entire study period. The second group (nine patients) had a level greater than 50 nmol/L followed by a decline ending with a final level below 50 nmol/L. In the third group (six patients) serum cobalt was greater than 50 nmol/L with no trend to a decline. In the fourth group (six patients) the cobalt levels were very high (greater than 150 nmol/L). Discussion: The six patients in the fourth group were very particular. There were three patients with secondary bilateral implants with a late peak in serum cobalt, one with an impingement on the acetabular rim, one with renal failure, and one who had a very high level of physical activity. The first group had what appears to be a favourable course, similar to the second group where a stabilisation phenomenon could be operating. An explanation in the third group is difficult but could involve a third segment abrasion phenomenon. Conclusion: Longitudinal analysis of serum cobalt levels provides more information than point measures in patients with metal-on-metal arthroplasties. Intercurrent mechanical phenomena can be detected; unexpected behaviour of the metal-on-metal junction can be suspected in certain patients

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

Purpose: The position of the patella after implantation of a total knee arthroplasty is generally determined by static measurements on the femoropatellar 30° flexion view or on a computed tomography (CT) scan in full extension. We studied the kinetics of the patellar implant between 0° and 90° on dynamic CT scans to determine the influence of torsion of the femoral and tibial components on the patellar course. Material and methods: Twenty patients with titanium total knee arthroplasties implanted in 1991 and 1992 underwent a dynamic CT study preoperatively and during the year following prosthesis implantation. An Imatron machine was used to obtain dynamic slices during knee flexion from 0° to 90°. The patient was installed in the prone position. Slice thickness was 8 mm for images centred on the lower end of the femur. Ten 50 ms images were obtained during flexion from 0° to 90°. The technique used preoperatively and postoperatively enabled study of transversal translation and tilt of the patella. Results: The orientation of the patellar transversal bony axis remained closely parallel to the flexion axis of the knee (i.e. the epicondylar axis) both preoperatively and postoperatively, irrespective of the orientation of the femoral and tibial components. Between 0° and 90° flexion, the prosthetic patella exhibited a translation movement laterally to medially during the first degrees of flexion then medially to laterally during the last degrees of flexion. The transversal displacement of the patellar insert was less pronounced when the femoral component was placed in external rotation from the epicondylar axis. For femoral implants in internal rotation (mean 5°), the translation of the patellar insert was a mean 1.5 mm between extension and flexion. This translation was only a mean 1 cm for implants in external rotation (mean 5°). Contact between the patellar prosthetic component and the femoral prosthetic component were more harmonious when the femoral implant was placed in external rotation. Torsion of the tibial implant did not appear to have an impact on the transversal course of the patella in this series. Discussion, conclusion: Rotation of the femoral component influenced the relationship between the patella and the femoral component in flexion-extension movements. However, torsion of the femoral component had little effect on the position of the patella itself. The patellar remained schematically parallel to the epicondylar axis, maintaining an orientation close to that observed preoperatively. The torsion of the femoral implant is the element that modifies its position under the patella and by consequence the relations between the patella and the femoral trochleae. These modifications are more pronounced when the knee is in extension than when the knee is in 90° flexion, excepting for the lift-off phenomenon observed at 90° flexion which is related to the trapezoidal femorotibial resection spaces

Introduction

The human wrist is a highly complex joint, offering extensive motion across various planes. This study investigates scapholunate ligament (SLL) injuries’ impact on wrist stability and arthritis risks using cadaveric experiments and the finite element (FE) method. It aims to validate experimental findings with FE analysis results.

Objective

The objective of this study was to evaluate the rotation and translation of each joint in the hindfoot and compare the load response in healthy feet with that in stage II posterior tibial tendon dysfunction (PTTD) flatfoot by analysing the reconstructive three-dimensional (3D) computed tomography (CT) image data during simulated weight-bearing.