A Glow before Darkness: Toxicity of Glitter Particles to Marine Invertebrates.

Glitter particles are considered a model of microplastics, which are used in a wide range of products. In this study, we evaluated the toxicity of two types of glitter (green and white, with distinct chemical compositions) dispersions on the embryonic development of the sea urchins Echinometra lucunte, Arbacia lixula, and the mussel Perna perna. The Toxicity Identification and Evaluation (TIE) approach was used to identify possible chemicals related to toxicity. Glitter dispersions were prepared using 0.05% ethanol. The tested dispersions ranged from 50 to 500 mg/L. The white glitter was composed of a vinyl chloride-methyl acrylate copolymer. The effective concentrations of green glitter to 50% embryos (EC50) were 246.1 (235.8-256.4) mg/L to A. lixula, 23.0 (20.2-25.8) mg/L to P. perna and 105.9 (61.2-150.2) mg/L, whereas the EC50 of white glitter to E. lucunter was 272.2 (261.5-282.9) mg/L. The EC50 for P. perna could not be calculated; however, the lowest effect concentration was 10 mg/L-that was the lowest concentration tested. The filtered suspension of green glitter had Ag levels exceeding the legal standards for marine waters. TIE showed that metals, volatiles, and oxidant compounds contribute to toxicity. The results showed that glitter may adversely affect marine organisms; however, further studies are necessary to determine its environmental risks.

Transfer of plantar pressure from the medial to the central forefoot in patients with hallux valgus.

BACKGROUND: The aim of the study was to evaluate changes in plantar pressure distribution in feet affected by hallux valgus compared with their contralateral non-affected feet and with the feet of healthy control subjects. METHODS: Thirty-six patients with unilateral hallux valgus who were indicated for surgery and 30 healthy subjects were assessed on a pedobarographic instrumented treadmill for step length and width, mean stance phase, and plantar foot pressure distribution. Plantar pressure distribution was divided into eight regions. RESULTS: Significantly higher plantar pressures were observed in hallux valgus feet under the second and third metatarsal heads (p = .033) and the fourth and fifth toes (p < .001) than in the healthy control feet. Although decreased pressures were measured under the hallux in affected feet (197 [82-467] kPa) in contrast to the contralateral side (221 [89-514] kPa), this difference failed to reach statistical significance (p = .055). The gait parameters step width, step length, and single-limb support did not show any differences between hallux valgus and control feet. CONCLUSION: Although the literature on changes in plantar pressures in hallux valgus remains divided, our findings on transferring load from the painful medial to the central and lateral forefoot region are consistent with the development of transfer metatarsalgia in patients with hallux valgus.

Increased patellofemoral pressure after TKA: an in vitro study.

PURPOSE: Considering the discrepant results of the recent biomechanical studies, the purpose of this study was to simulate dynamic muscle-loaded knee flexion with a large number of specimens and to analyse the influence of total knee arthroplasty (TKA) without and with patellar resurfacing on the patellofemoral pressure distribution. METHODS: In 22 cadaver knee specimens, dynamic muscle-loaded knee flexion (15°-90°) was simulated with a specially developed knee simulator applying variable muscle forces on the quadriceps muscles to maintain a constant ankle force. Patellofemoral pressures were measured with flexible, pressure-sensitive sensor foils (TEKSCAN) and patellofemoral offset with an ultrasound motion-tracking system (ZEBRIS). Measurements were taken on the native knee, after total knee arthroplasty and after patellar resurfacing. Correct positioning of the patellar implant was examined radiologically. RESULTS: The maximal patellofemoral peak pressure partly increased from the native knee to the knee with TKA with intact patella (35°-90°, p < 0.012) and highly increased (twofold to threefold) after patellar resurfacing (20°-90°, p < 0.001). Concurrently, the patellofemoral contact area decreased and changed from a wide area distribution in the native knee, to a punctate area after TKA with intact patella and a line-shaped area after patellar resurfacing. Patellar resurfacing led to no increase in patellar thickness and patellofemoral offset. CONCLUSIONS: Despite correct implantation of the patellar implants and largely unchanged patellofemoral offset, a highly significant increase in pressure after patellar resurfacing was measured. Therefore, from a biomechanical point of view, the preservation of the native patella seems reasonable if there is no higher grade patellar cartilage damage.

Differences in knee joint kinematics and forces after posterior cruciate retaining and stabilized total knee arthroplasty.

BACKGROUND: Posterior cruciate ligament (PCL) retaining (CR) and -sacrificing (PS) total knee arthroplasties (TKA) are widely-used to treat osteoarthritis of the knee joint. The PS design substitutes the function of the PCL with a cam-spine mechanism which may produce adverse changes to joint kinematics and kinetics. METHODS: CR- and PS-TKA were performed on 11 human knee specimens. Joint kinematics were measured with a dynamic knee simulator and motion tracking equipment. In-situ loads of the PCL and cam-spine were measured with a robotic force sensor system. Partial weight bearing flexions were simulated and external forces were applied. RESULTS: The PS-TKA rotated significantly less throughout the whole flexion range compared to the CR-TKA. Femoral roll back was greater in the PS-TKA; however, this was not correlated with lower quadriceps forces. Application of external loads produced significantly different in-situ force profiles between the TKA systems. CONCLUSIONS: Our data demonstrate that the PS-design significantly alters kinematics of the knee joint. Our data also suggest the cam-spine mechanism may have little influence on high flexion kinematics (such as femoral rollback) with most of the load burden shared by supporting implant and soft-tissue structures.

Dissipated energy as a method to characterize the cartilage damage in large animal joints: an in vitro testing model.

Several quantitative methods for the in vitro characterization of cartilage quality are available. However, only a few of these methods allow surgical cartilage manipulations and the subsequent analysis of the friction properties of complete joints. This study introduces an alternative approach to the characterization of the friction properties of entire joint surfaces using the dissipated energy during motion of the joint surfaces. Seven sheep wrist joints obtained post mortem were proximally and distally fixed to a material testing machine. With the exception of the carpometacarpal articulation surface, all joint articulations were fixed with 'Kirschner' wires. Three cartilage defects were simulated with a surgically introduced groove (16 mm(2), 32 mm(2), 300 mm(2)) and compared to intact cartilage without an artificial defect. The mean dissipated energy per cycle was calculated from the hysteresis curve during ten torsional motion cycles (±10°) under constant axial preload (100-900 N). A significant increase in dissipated energy was observed with increasing cartilage defect size and axial load (p<0.001). At lower load levels, the intact and 16 mm(2) defect showed a similar dissipated energy (p>0.073), while all other defect conditions were significantly different (p=0.015). All defect sizes were significantly different (p=0.049) at 900 N axial load. We conclude that the method introduced here could be an alternative for the study of cartilage damage, and further applications based on the principles of this method could be developed for the evaluation of different cartilage treatments.

Gender differences in tibio-femoral kinematics and quadriceps muscle force during weight-bearing knee flexion in vitro.

PURPOSE: Females have a higher risk in terms of anterior cruciate ligament injuries during sports than males. Reasons for this fact may be different anatomy and muscle recruitment patterns leading to less protection for the cruciate- and collateral-ligaments. This in vitro study aims to evaluate gender differences in knee joint kinematics and muscle force during weight-bearing knee flexions. METHODS: Thirty-four human knee specimens (17 females/17 males) were mounted on a dynamic knee simulator. Weight-bearing single-leg knee flexions were performed with different amounts of simulated body weight (BW). Gender-specific kinematics was measured with an ultrasonic motion capture system and different loading conditions were examined. RESULTS: Knee joint kinematics did not show significant differences regarding anteroposterior and medial-lateral movement as well as tibial varus-valgus and internal-external rotation. This applied to all simulated amounts of BW. Simulating 100 N BW in contrast to AF50 led to a significant higher quadriceps overall force in female knees from 45° to 85° of flexion in contrast to BW 50 N. In these female specimens, the quadriceps overall force was about 20 % higher than in male knees being constant in higher flexion angles. CONCLUSIONS: It is indicated by our results that in a squatting movement females compared with males produce higher muscle forces, suggesting an increased demand for muscular stabilization, whereas tibio-femoral kinematics was similar for both genders.

Biomechanical measurement system for measuring frictional properties of synovial joint after cartilage injury / 中国组织工程研究

10.3969/j.issn.2095-4344.2013.26.012

The influence of asymmetric quadriceps loading on patellar tracking--an in vitro study.

BACKGROUND: In patients with anterior knee pain and patellar instability, a specific training of the quadriceps muscle - especially the vastus medialis - is often recommended, although the practicability is discussed controversially and the proof of a measurable clinical effect is difficult. Therefore, this in vitro study investigates the influence of asymmetric muscle loading on the motion of the human patella. METHODS: Seven human knee specimens were tested in a specially developed knee simulator. During simulated weight-bearing knee flexion, the kinematics of tibia, femur and patella were measured using an ultrasound motion capture system. The quadriceps forces were controlled to achieve a constant ankle force over the whole flexion range which is assumed to represent almost physiological loading. Three different force distributions of the quadriceps were tested - a central, equally distributed load as well as mainly lateral and medial loads. RESULTS: A significant influence of different quadriceps force distributions was found for patellar tilt around a proximodistal axis (up to 1.7°) and patellar rotation around an anteroposterior axis (up to 3.8°) with respect to the femur. Interestingly, the patellar mediolateral shift was influenced only marginally (<1.5mm). CONCLUSIONS: Specific muscle training might help patients with patellofemoral pain and cartilage damage by a slight modification of the kinematics, but we could show that even highly asymmetric quadriceps loads only led to a small alteration of the mediolateral shift in case of a physiologic anatomy of the trochlear groove.

Differences in tibiofemoral kinematics between the unloaded robotic passive path and a weightbearing knee simulator.

Cadaveric in vitro studies are essential to test hypotheses concerning surgical manipulations in the same individual. Robotic technologies as well as different knee-models have been developed to get an in-depth comprehension of knee joint kinematics. The purpose of this study was to compare utilization of these different established principles.Ten human cadaveric knee specimens were used to measure the kinematics during a weight-bearing flexion in a 6-degrees-of-freedom knee simulator. While flexing the knee, joint quadriceps muscle forces were dynamically simulated to reach a vertical ground reaction force of 100N. Fourteen knee specimens were mounted in 6-degrees-of-freedom robotic manipulator with a universal force sensor. The unloaded flexing motion of each specimen was measured by finding positions for each degree of flexion where all forces are minimal (passive path). The kinematic data of the knee-simulator and the robot concerning internal-external rotation, anterior-posterior translation, varus-valgus motion, and medial-lateral translation was examined.For all investigated degrees of freedom the kinematics of the robotic passive path differed from the loaded kinematics in the knee simulator.Simulated bodyweight as well as the examination method used has a substantial influence on joint kinematics during flexion which has to be considered when interpreting biomechanical studies as well as clinical tests.

Biomechanical proof of barbed sutures for the efficacy of laparoscopic pyeloplasty.

BACKGROUND AND PURPOSE: The gold standard for management of adult ureteropelvic junction obstruction is laparoscopic dismembered pyeloplasty (LPP), described by Anderson-Hynes, with reduced postoperative complications, early patient release, and favorable results. LPP, however, necessitates a high level of surgical expertise, especially with regard to reanastomosis. Knotless self-anchoring barbed sutures have also been introduced into aesthetic surgery and wound closure. We compared a self-retaining suture (SRS) Quill(®) (Angiotech, Canada) with a standard monofilament suture to further investigate their biomechanical and urodynamic aspects. MATERIALS AND METHODS: We analyzed breaking strength and stiffness between SRS 4.0, 3.0, and polydioxanone suture (PDS(®)) 4.0 (Ethicon, Germany) using a biomechanical testing unit. Urodynamic evaluations were performed in the porcine upper urinary tract, closing a longitudinal incision either with SRS 4.0 (without knots) or with PDS 4.0 (five knots each end). Suture line shortening, suture time, tightness, and intrapelvic pressure were measured. RESULTS: SRS 4.0 breaks at a mean of 11.57 N (standard deviation [SD]=1.25, stiffness 172.8 N/mm(2), SD=10.84), SRS 3.0 at 16.01 N (1.81), and PDS 4.0 at 18.41 N (0.75, 128.9 N/mm(2), 7.45). SRS 4.0 results in a suture line shortening from mean 3.08 to 2.26 mm (-26.6%) while PDS 4.0 shortens from 3.05 to 1.81 mm (-40.7%). The maximum intrapelvic pressure demonstrated no difference, and leakage was seen in 50% of the cases. Suture time was significantly decreased with SRS use (SRS 4.0 277 s and PDS 4.0 364 s). CONCLUSION: SRS offers immediate tissue adaption with reduced suture line shortening and equal tightness compared with nonbarbed material in vitro. Knotless suturing using SRS is time efficient and appears to be an excellent material for LPP.

An implant-free double-bundle reconstruction of the anterior cruciate ligament: operative technique and influence on tibiofemoral kinematics.

BACKGROUND: Reconstruction of the anterior cruciate ligament is a standard surgical procedure in sports traumatology. The widespread replacement method using hamstring tendons has an important shortcoming namely delayed or missing bony healing in contrast to patellar tendon grafts where implant-free fixation is established by using the adjacent bone blocks. The purpose of this study was to describe a new implant-free surgical procedure using hamstring tendon grafts and to analyse the influence on tibiofemoral kinematics in vitro. METHODS: Nine human knee specimens with arthroscopically transected anterior cruciate ligaments were mounted on a dynamic knee simulator and weight-bearing muscle-loaded knee flexions were simulated while a robotic universal force sensor system was used to provide external tibial loads. Three different loading conditions were simulated including partial body weight only, an additional 50 N anterior tibial force or an additional Five Nm of internal rotational torque. After reconstruction of the anterior cruciate ligament using a tibial bone block hybrid technique these three trials were repeated. The kinematics was measured with an ultrasonic measuring system and different loading and ligament conditions were examined. Graft tunnel placement was verified by computed tomography. FINDINGS: Our fixation method achieved stability to anterior tibial drawer force whereas internal tibial rotation did not change before and after the reconstruction. Computed tomography confirmed anatomical graft and tunnel placement. INTERPRETATION: The presented operative procedure is technically feasible and leads to reproducible results concerning knee joint kinematics and graft placement.

Influence of bi- and tri-compartmental knee arthroplasty on the kinematics of the knee joint.

BACKGROUND: The cruciate ligaments are important stabilizers of the knee joint and determine joint kinematics in the natural knee and after cruciate retaining arthroplasty.No in vitro data is available to biomechanically evaluate the ability of the anterior cruciate ligament (ACL) to maintain knee joint kinematics after bicruciate-retaining bi-compartmental knee arthroplasty (BKA).Therefore, the objective of the current study was to investigate the kinematics of the natural knee joint, before and after installing bicruciate-retaining BKA and posterior cruciate retaining total knee arthroplasty. Specifically, we incorporated a dynamic knee simulator to simulate weight-bearing flexions on cadaveric knee specimen before and after surgical manipulations. METHODS: In this cadaveric study we investigated rotational and translational tibiofemoral kinematics during simulated weight-bearing flexions of the intact knee, after bi-compartmental knee arthroplasty (BKA+), after resecting the ACL in BKA (BKA-), and after posterior cruciate retaining total knee arthroplasty (TKA). RESULTS: Rotation of BKA+ is closest to the intact knee joint, whereas TKA shows significant differences from 30 to 90 degree of flexion. Within the tested flexion range (15 to 90 degree of flexion), there was no significant difference in the anterior-posterior translation among intact, BKA+, and TKA knees. Resecting the ACL in BKA leads to a significant anterior tibial translation. CONCLUSIONS: BKA with intact cruciate ligaments resembles rotation and translation of the natural knee during a simulated weight-bearing flexion. It is a suitable treatment option for medial and patellofemoral osteoarthritis with advantages in rotational characteristics compared to TKA.

The effect of different quadriceps loading patterns on tibiofemoral joint kinematics and patellofemoral contact pressure during simulated partial weight-bearing knee flexion.

PURPOSE: The purpose of this in vitro study was to investigate the influence of different quadriceps loading patterns on tibiofemoral joint kinematics and patellofemoral pressure. METHODS: A dynamic muscle-loaded knee squat was simulated on eight knee specimens with an upright knee simulator while measuring tibiofemoral joint kinematics and patellofemoral pressure distribution. The quadriceps muscle was attached to three actuators simulating the three main extensor muscles, and five different quadriceps loading patterns were tested. RESULTS: Tibial axial and varus-valgus-rotation are affected most while changing quadriceps loading patterns from lateral to medial. Higher internal tibial rotation is associated with higher medial muscle load compared to the symmetrical loading condition. Contact force, contact area and maximum peak pressure rise with increasing flexion angles. Accentuating the vastus lateralis muscle induces a significant reduction in patellofemoral contact force and a 30% diminished contact area at 90° of flexion. CONCLUSION: Strengthening the vastus medialis muscle leads to increased internal tibial rotation, thus optimizing patella tracking by lowering the Q-angle. In contrast, weakness of the vastus medialis muscle causes decreased tibial internal rotation and is associated with lower patellofemoral contact pressure and contact area. Vastus medialis exercise is advisable to improve patella tracking but may not be recommended in patients with disorders due to increased patellofemoral contact pressure.

Translational and rotational knee joint stability in anterior and posterior cruciate-retaining knee arthroplasty.

This study investigated passive translational and rotational stability properties of the intact knee joint, after bicruciate-retaining bi-compartmental knee arthroplasty (BKA) and after posterior cruciate retaining total knee arthroplasty (TKA). Fourteen human cadaveric knee specimens were used in this study, and a robotic manipulator with six-axis force/torque sensor was used to test the joint laxity in anterior-posterior translation, valgus-varus, and internal-external rotation. The results show the knee joint stability after bicruciate-retaining BKA is similar to that of the native knee. On the other hand, the PCL-retaining TKA results in inferior joint stability in valgus, varus, external rotation, anterior and, surprisingly, posterior directions. Our findings suggest that, provided functional ligamentous structures, bicruciate-retaining BKA is a biomechanically attractive treatment for joint degenerative disease.

The anterior cruciate ligament provides resistance to externally applied anterior tibial force but not to internal rotational torque during simulated weight-bearing flexion.

PURPOSE: We investigated knee kinematics during simulated weight-bearing flexion and determined the effect of 3 different parameters of external tibial loading on the kinematics of the anterior cruciate ligament (ACL)-intact and ACL-deficient knee. METHODS: Ten human knee specimens were mounted on a dynamic knee simulator, and weight-bearing muscle-loaded knee flexions were simulated while a robotic/universal force sensor system was used to provide external tibial loads during the motion. Three different loading conditions were simulated: partial body weight only, an additional 50 N of anterior tibial force (ATD), or an additional 5 Nm of internal rotational tibial torque (IRT). After arthroscopic transection of the ACL, these 3 trials were repeated. The kinematics were measured with an ultrasonic measuring system for 3-dimensional motion analysis, and different loading and knee conditions were examined. RESULTS: When the ACL was intact, ATD and IRT barely changed the anterior tibial translation. However, in the absence of the ACL, ATD significantly increased the anterior tibial translation by 5 mm whereas IRT did not. The application of IRT increased the internal tibial rotation of ACL-intact knees, but there was no difference in the internal rotation before and after transection of the ACL. Regardless of ACL status, the difference in the anterior tibial translation and the internal tibial rotation across different external tibial loadings was greater at lower flexion angles and gradually diminished with increasing flexion angles. CONCLUSIONS: We established an experimental protocol, incorporating a dynamic knee simulator and a robotic/universal force sensor system, to successfully measure the kinematics of the knee joint while applying external forces in weight-bearing flexion. Our findings suggest that, in muscle-loaded knee flexion, the ACL provides substantial resistance to externally applied ATD but not to IRT. CLINICAL RELEVANCE: Information from this study allows us to better understand the function of the ACL and, hence, treatment of injuries to this important stabilizing ligament.

A simple new device to examine human stance: the totter-slab.

This article describes a new measuring device to investigate balancing strategies of human stance: the totter-slab, i.e., a standing plate suspended with steel cables to hooks on a steel frame. First, we analysed the physical properties of the device by recording free oscillations under different conditions [varying amplitude, mass and centre of mass (COM) height]. This allowed us to determine the eigenfrequency f and the damping coefficient D<1 Ns/m for each trial. The trials showed that the measured damped eigenfrequency of f is approximately 0.63 Hz is barely dependent on the mass loaded. The ratio D/M is approximately 0.015 1/s is a constant almost independent of the different conditions. Furthermore, we determined the stiffnesses of the suspending cables and their suspension points to check for potential energy storage capacity of the totter-slab. We found that the totter-slab is a useful, well-defined, reliable and developable measuring device for different non-rigid-ground stance conditions. In a second part of the investigation, we compared the frequency spectra of six subjects balancing on the totter-slab with their spectra while standing quietly on a force plate fixed to the ground. The totter-slab spectra showed two distinct, dominant peak regions at approximately 0.3 and 1.1 Hz. This finding enforces the double inverted pendulum to be an adequate model particularly for balancing on the totter-slab. Compared with the firm ground condition, these two peak regions were more pronounced when balancing on the totter-slab. However, there is a variety of frequencies in the region 0.2...1.5 Hz specific for an individual subject in both balancing conditions.

In vitro measurement of intraarticular pressure in the ankle joint.

Ankle joint affections and injuries are common problems in sports traumatology and in the daily routine of arthroscopic surgeons. However, there is little knowledge regarding intraarticular loads. Pressures on the ankle were determined in a dynamic model on 8 cadaver specimens, applying forces to tendons of the foot over the stance phase under vertical loading. A characteristic course of loading in the tibiotalar joint with a rapid increase upon heel contact was observed. It increased gradually to reach a maximum after 70% of the stance phase, during the push-off phase. The major torque in the ankle joint is located anterolaterally. A dynamic loading curve of the ankle joint can be demonstrated. These observations explain phenomena such as the appearance of osteophytes on the anterior tibia in the case of ankle osteoarthritis and the relatively low incidence of posterior tibial edge fragments in the case of trimalleolar ankle fracture. Furthermore, the medial side of the talus is less loaded compared to the lateral side, which appears relevant to the treatment of osteochondrosis dissecans.

Simulation of force loaded knee movement in a newly developed in vitro knee simulator.

Simulating knee movement under physiological muscle loading is a prerequisite in order to improve surgical treatment and rehabilitation techniques. An apparatus is presented which can simulate five knee muscles to control a definite amount of body weight using the ankle force as the target value for the control mechanism. The influence of different amounts of simulated ankle forces upon the knee movement was investigated. The apparatus was constructed in a closed kinetic chain design similar to the so-called Oxford rig. Three quadriceps muscles and two hamstring muscles were controlled by electrical servo motors via tendon clamps in order to adjust a target value for the simulated body weight. Three fresh frozen cadaveric specimens were used to validate the apparatus and to examine the difference between loaded and unloaded knee flexion from 10 degrees to 90 degrees . In one specimen, up to 250 N simulated ankle force could be achieved for a single leg knee flexion. Among the kinematic variables, tibial rotation was influenced the most when varying the amount of simulated body weight. Although the knee kinematics changed considerably with increasing simulated bodyweight, the shapes of the kinematic profiles remained similar, indicating that qualitative clinical insights can still be elucidated with partially (but reasonably) loaded knees.

Forces in anterior cruciate ligament during simulated weight-bearing flexion with anterior and internal rotational tibial load.

This study determined in-vitro anterior cruciate ligament (ACL) force patterns and investigated the effect of external tibial loads on the ACL force patterns during simulated weight-bearing knee flexions. Nine human cadaveric knee specimens were mounted on a dynamic knee simulator, and weight-bearing knee flexions with a 100N of ground reaction force were simulated; while a robotic/universal force sensor (UFS) system was used to provide external tibial loads during the movement. Three external tibial loading conditions were simulated, including no external tibial load (termed BW only), a 50N anterior tibial force (ATF), and a 5Nm internal rotation tibial torque (ITT). The tibial and femoral kinematics was measured with an ultrasonic motion capture system. These movement paths were then accurately reproduced on a robotic testing system, and the in-situ force in the ACL was determined via the principle of superposition. The results showed that the ATF significantly increased the in-situ ACL force by up to 60% during 0-55 degrees of flexion, while the ITT did not. The magnitude of ACL forces decreased with increasing flexion angle for all loading conditions. The tibial anterior translation was not affected by the application of ATF, whereas the tibial internal rotation was significantly increased by the application of ITT. These data indicate that, in a weight-bearing knee flexion, ACL provides substantial resistance to the externally applied ATF but not to the ITT.

Innovation advances technical services.

Working in tandem with VAMED-KMB, the Vienna General Hospital in Austria has developed an innovative quality-based development model for the provision of technical services and plant maintenance. Report by Peter Csukovits, technical director of the hospital, and Otto Müller, general manager, VAMED-KMB.