Computational assessment on the impact of collagen fiber orientation in cartilages on healthy and arthritic knee kinetics/kinematics.

BACKGROUND: The inhomogeneous distribution of collagen fiber in cartilage can substantially influence the knee kinematics. This becomes vital for understanding the mechanical response of soft tissues, and cartilage deterioration including osteoarthritis (OA). Though the conventional computational models consider geometrical heterogeneity along with fiber reinforcements in the cartilage model as material heterogeneity, the influence of fiber orientation on knee kinetics and kinematics is not fully explored. This work examines how the collagen fiber orientation in the cartilage affects the healthy (intact knee) and arthritic knee response over multiple gait activities like running and walking. METHODS: A 3D finite element knee joint model is used to compute the articular cartilage response during the gait cycle. A fiber-reinforced porous hyper elastic (FRPHE) material is used to model the soft tissue. A split-line pattern is used to implement the fiber orientation in femoral and tibial cartilage. Four distinct intact cartilage models and three OA models are simulated to assess the impact of the orientation of collagen fibers in a depth wise direction. The cartilage models with fibers oriented in parallel, perpendicular, and inclined to the articular surface are investigated for multiple knee kinematics and kinetics. FINDINGS: The comparison of models with fiber orientation parallel to articulating surface for walking and running gait has the highest elastic stress and fluid pressure compared with inclined and perpendicular fiber-oriented models. Also, the maximum contact pressure is observed to be higher in the case of intact models during the walking cycle than for OA models. In contrast, the maximum contact pressure is higher during running in OA models than in intact models. Additionally, parallel-oriented models produce higher maximum stresses and fluid pressure for walking and running gait than proximal-distal-oriented models. Interestingly, during the walking cycle, the maximum contact pressure with intact models is approximately three times higher than on OA models. In contrast, the OA models exhibit higher contact pressure during the running cycle. INTERPRETATION: Overall, the study indicates that collagen orientation is crucial for tissue responsiveness. This investigation provides insights into the development of tailored implants.

An assessment of bone marrow mesenchymal stem cell and human articular cartilage derived chondroprogenitor cocultures vs. monocultures.

BACKGROUND: Cell based therapy in cartilage repair predominantly involves the use of chondrocytes and mesenchymal stromal cells (MSC). Co-culture systems, due to their probable synergistic effect on enhancement of functional chondrogenesis and reduction in terminal differentiation have also been attempted. Chondroprogenitors, derived from articular cartilage and regarded as MSCs, have recently garnered interest for consideration in cartilage regeneration to overcome limitations associated with use of conventional cell types. The aim of this study was to assess whetherco-culturing bone marrow (BM)-MSCs and chondroprogenitors at different ratios would yield superior results in terms of surface marker expression, gene expression and chondrogenic potential. METHODS: Human BM-MSCs and chondroprogenitors obtained from three osteoarthritic knee joints and subjected to monolayer expansion and pellet cultures (10,000 cells/cm2) as five test groups containing either monocultures or co-cultures (MSC: chondroprogenitors) at three different ratios (75:25, 50:50 and 25:75) were utilized. RESULTS: Data analysis revealed that all groups exhibited a high expression of CD166, CD29 and CD49e. With regard to gene expression, high expression of SOX9, Aggrecan and Collagen type I; a moderate expression of Collagen type X and RUNX2; with a low expression of Collagen type II was seen. Analysis of pellet culture revealed that chondroprogenitor monoculture and chondroprogenitor dominant coculture, exhibited a subjectively larger pellet size with higher deposition of Collagen type II and glycosaminoglycan. CONCLUSION: In conclusion, this study is suggestive of chondroprogenitor monoculture superiority over MSCs, either in isolation or in a coculture system and proposes further analysis of chondroprogenitors for cartilage repair.

Assessment of Native Human Articular Cartilage: A Biomechanical Protocol.

OBJECTIVES: Recapitulating the mechanical properties of articular cartilage (AC) is vital to facilitate the clinical translation of cartilage tissue engineering. Prior to evaluation of tissue-engineered constructs, it is fundamental to investigate the biomechanical properties of native AC under sudden, prolonged, and cyclic loads in a practical manner. However, previous studies have typically reported only the response of native AC to one or other of these loading regimes. We therefore developed a streamlined testing protocol to characterize the elastic and viscoelastic properties of human knee AC, generating values for several important parameters from the same sample. DESIGN: Human AC was harvested from macroscopically normal regions of distal femoral condyles of patients (n = 3) undergoing total knee arthroplasty. Indentation and unconfined compression tests were conducted under physiological conditions (temperature 37 °C and pH 7.4) and testing parameters (strain rates and loading frequency) to assess elastic and viscoelastic parameters. RESULTS: The biomechanical properties obtained were as follows: Poisson ratio (0.4 ± 0.1), instantaneous modulus (52.14 ± 9.47 MPa) at a loading rate of 1 mm/s, Young's modulus (1.03 ± 0.48 MPa), equilibrium modulus (7.48 ± 4.42 MPa), compressive modulus (10.60 ± 3.62 MPa), dynamic modulus (7.71 ± 4.62 MPa) at 1 Hz and loss factor (0.11 ± 0.02). CONCLUSIONS: The measurements fell within the range of reported values for human knee AC biomechanics. To the authors' knowledge this study is the first to report such a range of biomechanical properties for human distal femoral AC. This protocol may facilitate the assessment of tissue-engineered composites for their functionality and biomechanical similarity to native AC prior to clinical trials.

Articular cartilage repair using autologous collagen-induced chondrogenesis (ACIC): a pragmatic and cost-effective enhancement of a traditional technique.

PURPOSE: The autologous collagen-induced chondrogenesis technique is described, and the results of a 6-year follow-up clinical study using this technique are presented. METHODS: 30 patients with International Cartilage Repair Society (ICRS) Grade III/IVa symptomatic chondral defects of the knee treated with enhanced microdrilling using atelocollagen were prospectively examined in this clinical series. The median age of the patients was 39.0 years (range 19-61 years). Patients were followed up to 72 months. Clinical evaluation was performed using functional knee scores and radiologically. Both quantitative and qualitative assessments were performed. RESULTS: Statistically significant and clinically relevant improvement was observed in 2 years and was sustained for the 6 years of the study observation. At 6 years, the mean Lysholm score was 79.7 (SD 6.8) compared to 52.6 (SD 10.7) pre-operatively (p < 0.05). The symptomatic Knee Injury and Osteoarthritis Outcome Score (KOOS) improved from 68.3 (SD 11.4) to 90.2 (SD 4.3) (p < 0.05). The subjective International Knee Documentation Committee (IKDC) also showed improvement from 39.1 (SD 4.1) to 81.6 (SD 7.8) (p < 0.05). The calculated T2* relaxation times were 26.0 (SD 4.2) seconds and 30.3 (SD 6.2) seconds for the repair tissue and native cartilage, respectively. The average magnetic resonance observation of cartilage repair tissue (MOCART) score was 78.5 (SD 9.6) for all lesions. CONCLUSION: The enhanced microdrilling using atelocollagen is an enhancement of the traditional microfracture method using an off-the-shelf product. When used to treat moderate to severe chondral lesions, this enhancement produces hyaline-like cartilage with a corresponding improvement in symptoms. LEVEL OF EVIDENCE: IV.

Biomechanical assessment of the stability of osteochondral grafts implanted in porcine and bovine femoral condyles.

Osteochondral grafts are used clinically to repair cartilage and bone defects and to restore the congruent articulating surfaces of the knee joint following cartilage damage or injury. The clinical success of such osteochondral grafts is heavily reliant on the biomechanical and tribological properties of the surgical repair; however, a limited number of studies have investigated these factors. The aim of this study was to evaluate the influence of graft harvesting and implantation technique as well as bone properties on the primary stability of press-fit implanted osteochondral grafts using a series of uniaxial experimental push-in and push-out tests. Animal (porcine and bovine) knees were used to deliver models of different bone properties (elastic modulus and yield stress). The study showed the graft harvesting method using either a chisel or drill-aided trephine to have no influence on primary graft stability; however, the preparation technique for the graft recipient site was shown to influence the force required to push the graft into the host tissue. For example, when the length of the graft was equal to the recipient site (bottomed), the graft was more stable and dilation of the recipient site was shown to reduce short-term graft stability especially in immature or less dense bone tissue. The push-out tests which compared tissue of different skeletal maturities demonstrated that the maturity of both the graft and host bone tissue to influence the stability of the graft. A higher force was required to push out more skeletally mature grafts from mature bone tissue. The study demonstrates the importance of surgical technique and bone quality/properties on the primary stability and ultimately, the success of osteochondral grafts in the knee.

Assessment of biomechanical properties of the extracellular and pericellular matrix and their interconnection throughout the course of osteoarthritis.

During osteoarthritis (OA)-triggered cartilage degeneration, the chondrocytes spatially rearrange from single to double strings, and then to small and finally big clusters. Both the extracellular matrix (ECM) and the pericellular matrix (PCM) progressively degrade in osteoarthritis, changing the overall mechanical properties of the cartilage. We investigated the mechanical properties particularly elasticity of the ECM and PCM and their interconnection as a function of chondrocyte spatial organisation. Human articular cartilage samples from 30 patients were categorised according to their cellular pattern. Elasticity of the ECM and PCM was assessed by means of atomic force microscopy (AFM). Significant decreases were observed in the elasticity of both the ECM and the PCM with each change of cellular pattern, except from single to double strings in the ECM (p = 0.072). Spatial reorganisation strongly correlated with the elasticity of the ECM (r = -0.768, p < 0.001) and of the PCM (r = -0.729, p < 0.001). The ECM/PCM ratio remained unchanged (r = -0.099, p = 0.281). This study is the first to describe and quantify the differences in the elastic moduli of the ECM in relation to the PCM on the basis of chondrocyte spatial arrangement. This study shows that the elastic changes of the ECM and the PCM occur simultaneously, unidirectionally, and to a comparable degree.

Non-Destructive Spectroscopic Assessment of High and Low Weight Bearing Articular Cartilage Correlates with Mechanical Properties.

OBJECTIVE: Autologous articular cartilage (AC) harvested for repair procedures of high weight bearing (HWB) regions of the femoral condyles is typically obtained from low weight bearing (LWB) regions, in part due to the lack of non-destructive techniques for cartilage composition assessment. Here, we demonstrate that infrared fiber optic spectroscopy can be used to non-destructively evaluate variations in compositional and mechanical properties of AC across LWB and HWB regions. DESIGN: AC plugs (N = 72) were harvested from the patellofemoral groove of juvenile bovine stifle joints, a LWB region, and femoral condyles, a HWB region. Near-infrared (NIR) and mid-infrared (MIR) fiber optic spectra were collected from plugs, and indentation tests were performed to determine the short-term and equilibrium moduli, followed by gravimetric water and biochemical analysis. RESULTS: LWB tissues had a significantly greater amount of water determined by NIR and gravimetric assay. The moduli generally increased in tissues from the patellofemoral groove to the condyles, with HWB condyle cartilage having significantly higher moduli. A greater amount of proteoglycan content was also found in HWB tissues, but no differences in collagen content. In addition, NIR-determined water correlated with short-term modulus and proteoglycan content (R = -0.40 and -0.31, respectively), and a multivariate model with NIR data was able to predict short-term modulus within 15% error. CONCLUSIONS: The properties of tissues from LWB regions differ from HWB tissues and can be determined non-destructively by infrared fiber optic spectroscopy. Clinicians may be able to use this modality to assess AC prior to harvesting osteochondral grafts for focal defect repair.

A cost-effective cell- and matrix-based minimally invasive single-stage chondroregenerative technique developed with validated vertical translation methodology.

Introduction The morbidity and significant health economic impact associated with the chondral lesion has led to a large number of strategies for therapeutic neochondrogenesis. The challenge has been to develop techniques that are cost effective single-stage procedures with minimal surgical trauma that have undergone rigorous preclinical scrutiny and robust reproducible assessment of effectiveness. A biological repair requires the generation of a cellular and matrix composite with appropriate signalling for chondrogenic differentiation. Methods and results A technique was developed that allowed chondrogenic primary (uncultured) cells from bone marrow aspirate concentrate, combined with a composite hydrophilic and fibrillar matrix to be applied arthroscopically to a site of a chondral lesion. The construct was tested in vitro and in animal experiments before clinical trials. Clinical trials involved 60 patients in a prospective study. Symptomatic International Cartilage Repair Society grade 3 and 4a lesions were mapped and treated. Pre- and postoperative clinical assessments showed statistically significant improved outcomes; Lysholm Knee Scoring Scale (mean 52.8 to > 76.4; P < 0.05) International Knee Documentation Committee (mean 39 to > 79 P < 0.05) and Knee injury and Osteoarthritis Outcome Score (64.5 to >89.2 P < 0.05). Postoperative magnetic resonance imaging was evaluated morphologically (magnetic resonance observation of cartilage repair tissue, average MOCART score 72) and qualitatively; the regenerate was comparable to native cartilage. Conclusions This technique is effective, affordable, requires no complex tools and delivers a single-stage treatment that is potentially accessible to any centre capable of performing arthroscopic surgery. Good clinical results were found to be sustained at five years of follow-up with a regenerate that appears hyaline like using multiple magnetic resonance measures.

MRI Cartilage Assessment of the Subtalar and Midtarsal Joints During a Transcontinental Ultramarathon - New Insights into Human Locomotion.

MR measurements can be accurately performed during 4486 km of running, opening a window into in vivo assessment of hindfoot articular cartilage under extreme ultra-endurance loading. This observational cross-sectional study included 22 randomized participants of TransEurope FootRace between Italy and the North Cape, which was accompanied by a trailer-mounted 1.5T MRI scanner over 9 weeks. Four follow up MR examinations of subtalar and midtarsal joints were performed. Statistics of cartilage T2* and thickness were obtained. Nearly all observed joints showed an initial significant mean T2* increase of 20.9% and 26.3% for the left and right side, followed by a relative decrease of 28.5% and 16.0% during the second half, respectively. It could be demonstrated that mobile MRI field studies allow in vivo functional tissue observations under extreme loading. Elevated T2* values recovered during the second half of the ultramarathon supported the evidence that this response is a physiological adaptive mechanism of chondrocyte function via upregulation of de novo synthesis of proteoglycans and collagen. These changes occurred in a distinct asymmetric pattern leaving a "biochemical signature" of articular cartilage that allows in vivo insight into joint loading. In conclusion, the normal articular cartilage of the hindfoot is resilient and adaptive, leaving extreme endurance activities up to limitless human ambition.

Assessment of T2 Relaxation Times for Normal Canine Knee Articular Cartilage by T2 Mapping Using 1.5-T Magnetic Resonance Imaging.

Objectives This study aims to assess and compare the T2 relaxation times for articular cartilage of normal canine stifle joints in four regions by T2 mapping using a 1.5-T magnetic resonance imaging (MRI). Methods In vivo prospective study: 20 hindlimbs (left and right) from 10 normal healthy beagle dogs (n = 20). The region of interest (ROI) was subdivided into medial and lateral condyles of femoral cartilage (MF and LF, respectively) and medial and lateral condyles of tibial cartilage (MT and LT, respectively). The T2 relaxation times were assessed in regions where the cartilage thickness was greater than 0.5 mm. Results The median maximum cartilage thickness (mm) of the four ROI were 0.7 (range: 0.9-0.6), 0.6 (range: 0.7-0.5), 0.7 (range: 0.9-0.5) and 0.6 (range: 0.8-0.5) at MF, LF, MT and LT, respectively. The errors in the measurement (%) of the four ROI were 64.3 (range: 50.0-75.0), 75.0 (range: 64.3-90.0), 64.3 (range: 20.0-90.0) and 75.0 (range: 56.3-90.0) at MF, LF, MT and LT, respectively. The median T2 relaxation times (ms) for the articular cartilage of the four ROI were 70.2 (range: 57.9-87.9), 57.5 (range: 46.8-66.9), 65.0 (range: 52.0-92.0) and 57.0 (range: 49.0-66.2) at MF, LF, MT and LT, respectively. The inter-observer correlation coefficient (ICC, 2.1) for the T2 relaxation times of MF was 0.644. Clinical Significance This study offers useful information on T2 relaxation times for articular cartilage of the stifle joint using a 1.5-T MRI in normal dogs.

Functional in situ assessment of human articular cartilage using MRI: a whole-knee joint loading device.

The response to loading of human articular cartilage as assessed by magnetic resonance imaging (MRI) remains to be defined in relation to histology and biomechanics. Therefore, an MRI-compatible whole-knee joint loading device for the functional in situ assessment of cartilage was developed and validated in this study. A formalin-fixed human knee was scanned by computed tomography in its native configuration and digitally processed to create femoral and tibial bone models. The bone models were covered by artificial femoral and tibial articular cartilage layers in their native configuration using cartilage-mimicking polyvinyl siloxane. A standardized defect of 8 mm diameter was created within the artificial cartilage layer at the central medial femoral condyle, into which native cartilage samples of similar dimensions were placed. After describing its design and specifications, the comprehensive validation of the device was performed using a hydraulic force gauge and digital electronic pressure-sensitive sensors. Displacement-controlled quasi-static uniaxial loading to 2.5 mm [Formula: see text] and 5.0 mm [Formula: see text] of the mobile tibia versus the immobile femur resulted in forces of [Formula: see text] N [Formula: see text] and [Formula: see text] N [Formula: see text] (on the entire joint) and local pressures of [Formula: see text] MPa [Formula: see text] and [Formula: see text] MPa [Formula: see text] (at the site of the cartilage sample). Upon confirming the MRI compatibility of the set-up, the response to loading of macroscopically intact human articular cartilage samples ([Formula: see text]) was assessed on a clinical 3.0-T MR imaging system using clinical standard proton-density turbo-spin echo sequences and T2-weighted multi-spin echo sequences. Serial imaging was performed at the unloaded state [Formula: see text] and at consecutive loading positions (i.e. at [Formula: see text] and [Formula: see text]. Biomechanical unconfined compression testing (Young's modulus) and histological assessment (Mankin score) served as the standards of reference. All samples were histologically intact (Mankin score, [Formula: see text]) and biomechanically reasonably homogeneous (Young's modulus, [Formula: see text] MPa). They could be visualized in their entirety by MRI and significant decreases in sample height [[Formula: see text]: [Formula: see text] mm; [Formula: see text]: [Formula: see text] mm; [Formula: see text]: [Formula: see text] mm; [Formula: see text] (repeated-measures ANOVA)] as well as pronounced T2 signal decay indicative of tissue pressurization were found as a function of compressive loading. In conclusion, our compression device has been validated for the noninvasive response-to-loading assessment of human articular cartilage by MRI in a close-to-physiological experimental setting. Thus, in a basic research context cartilage may be functionally evaluated beyond mere static analysis and in reference to histology and biomechanics.

Ultrasonographic assessment of medial femoral cartilage deformation acutely following walking and running.

OBJECTIVE: To determine the magnitude of medial femoral cartilage deformation using ultrasonography (US) following walking and running in healthy individuals. DESIGN: Twenty-five healthy participants with no history of osteoarthritis or knee injury volunteered for this study. Medial femoral cartilage thickness was assessed using US before and after three separate 30-min loading conditions: (1) walking at a self-selected speed, (2) running at a self-selected speed, and (3) sitting on a treatment table (i.e., control). Cartilage deformation was calculated as the percent change score from pre to post loading in each loading condition. The magnitude of cartilage deformation was compared between the three loading conditions. RESULTS: There was no difference in baseline cartilage thickness between the three sessions (F1,24 = 0.18, P = 0.68). Cartilage deformation was different between the loading conditions (F1,24 = 47.54, P < 0.001). The walking (%Δ = -6.7, t24 = 6.90, P < 0.001, d = -1.92) and running (%Δ = -8.9, t24 = 8.14, P < 0.001, d = -1.85) conditions resulted in greater cartilage deformation when compared to the control condition (%Δ = +3.4). There was no difference in cartilage deformation between the running and walking conditions (t24 = 1.10, P = 0.28, d = 0.33). US measured medial femoral cartilage thickness demonstrated reliability and precision within a single session (ICC2,k = 0.966, SEM = 0.07 mm) and between additional sessions separated by seven (ICC2,k = 0.964, SEM = 0.08 mm) and 16 days (ICC2,k = 0.919, SEM = 0.11 mm). CONCLUSIONS: US demonstrated to be a reliable and sensitive imaging modality at quantifying medial femoral cartilage deformation in healthy individuals. Both walking and running conditions created greater cartilage deformation when compared to the control conditions, but no difference was observed between the walking and running conditions.

Mesenchymal stem cell therapy in the treatment of osteoarthritis: reparative pathways, safety and efficacy - a review.

Osteoarthritis is a leading cause of pain and disability across the world. With an aging population its prevalence is likely to further increase. Current accepted medical treatment strategies are aimed at symptom control rather than disease modification. Surgical options including joint replacement are not without possible significant complications. A growing interest in the area of regenerative medicine, led by an improved understanding of the role of mesenchymal stem cells in tissue homeostasis and repair, has seen recent focused efforts to explore the potential of stem cell therapies in the active management of symptomatic osteoarthritis. Encouragingly, results of pre-clinical and clinical trials have provided initial evidence of efficacy and indicated safety in the therapeutic use of mesenchymal stem cell therapies for the treatment of knee osteoarthritis. This paper explores the pathogenesis of osteoarthritis and how mesenchymal stem cells may play a role in future management strategies of this disabling condition.

The biphasic bioresorbable scaffold (Trufit(®)) in the osteochondral knee lesions: long-term clinical and MRI assessment in 30 patients.

BACKGROUND: Chondral or osteochondral defects have been reported in 60-67 % of patients in studies reporting knee arthroscopies. The surgical management of chondral and osteochondral defects (OCD's) of the articular surface of the knee joint remains a controversial topic. Osteochondral injuries can be treated with transfer cartilage procedure and with implantation of biodegradable scaffolds. For patients over 50 years old with largest osteochondral lesions, we prefer to use the biodegradable scaffold, like Trufit(®) plug (Smith & Nephew, Andover, MA). The purpose of this study is to evaluate the outcome of this series of surgical procedure with Trufit. METHODS: In our institute, the Trufit was used for the treatment of one or more focal osteochondral lesions of the femoral condyles positive MRI with or without concomitant ligamentous or meniscal pathology. We reviewed 30 patients with mean age of 60.57 years (range 32-79 years) with a clinical and imaging control at 6, 12, 24 and 48 months of follow-up. RESULTS: The clinical evaluation has shown the good outcome. The MRI conducted has shown the progressive partial integration of the scaffolds. CONCLUSIONS: The results obtained indicate a clear improvement of the clinical symptoms and slowing joint degeneration. The clinical and imaging results confirm that the Trufit constitutes a valid surgical alternative in case of focal osteochondral.

Influence of Ligament Properties on Tibiofemoral Mechanics in Walking.

Computational knee models provide a powerful platform to investigate the effects of injury and surgery on functional knee behavior. The objective of this study was to use a multibody knee model to investigate the influence of ligament properties on tibiofemoral kinematics and cartilage contact pressures in the stance phase of walking. The knee model included 14 ligament bundles and articular cartilage contact acting across the tibiofemoral and patellofemoral joints. The knee was incorporated into a lower extremity musculoskeletal model and was used to simulate knee mechanics during the stance phase of normal walking. A Monte Carlo approach was employed to assess the influence of ligament stiffness and reference strain on knee mechanics. The anterior cruciate ligament (ACL), medial collateral ligament (MCL), and posterior capsule properties exhibited significant influence on anterior tibial translation at heel strike, with the ACL acting as the primary restraint to anterior translation in mid-stance. The MCL and lateral collateral ligament (LCL) exhibited the greatest influence on tibial rotation from heel strike through mid-stance. Simulated tibial plateau contact location was dependent on the ACL, MCL, and LCL properties, while pressure magnitudes were most dependent on the ACL. A decrease in ACL stiffness or reference strain significantly increased the average contact pressure in mid-stance, with the pressure migrating posteriorly on the medial tibial plateau. These ligament-dependent shifts in tibiofemoral cartilage contact during walking are potentially relevant to consider when investigating the causes of early-onset osteoarthritis following knee ligament injury and surgical treatment.

Assessment of cartilage contact pressure and loading in the hip joint during split posture.

PURPOSE: Given the crucial role of the mechanical behavior in the degenerative process of the hip joint, analyzing the contact mechanics in the articular layers during physical activities could contribute to understanding the pathology. Indeed, the development process of hip osteoarthritis generally evolves over a long time period, and therefore analyzing the mechanical behavior of the hip joint during extreme repetitive movements will be helpful to analyze degeneration causes. The aim of the study was to investigate the link between the excessive movements and the development of hip osteoarthritis. METHODS: To individualize the analysis, we used a subject-specific and noninvasive approach based on finite element analysis and magnetic resonance imaging (MRI) data. The contact pressure distribution and loading conditions on the acetabular cartilage were assessed on eleven professional dancer subjects performing a split movement. This movement is frequently practiced (repetitive) by dancers during their daily exercises. Moreover, split postures are mostly characterized by high anatomical angles with subluxation (excessive). To ensure the motion accuracy, MRI data of the subjects were acquired in neutral and split positions performed inside the MRI scanner. Based on the reconstructed bone models from the MRI data, a motion tracking approach was used to compute the transformation between the two poses. To evaluate the contact during the split movement and to quantify the role of the labrum in the hip joint mechanics, additional simulations of two daily activities (walking and stand-up) were performed. Finally, a clinical study based on morphological and radiological analysis of the subjects was performed and validated by orthopedic surgeons and radiological experts to evaluate the proposed approach. RESULTS: The reconstructed split movement was characterized by high anatomical angles with a subluxation on the left hip. Consequently, strong deformations and pressures were observed during the simulation. The comparison of the simulation results of split posture and daily activities showed higher pressure and lower contact area during extreme movements. Moreover, the presence of labrum absorbed part of load and consequently decreased the predicted contact pressure and contact area on the acetabular cartilage. CONCLUSION: The comparison of the simulation results of the split posture and daily activities, as well as the correlation between the results of the analysis on extreme movement results and the clinical analysis performed by medical experts, strongly suggests that repetitive extreme movement could lead to early hip osteoarthritis.

Assessment of Knee Cartilage Stress Distribution and Deformation Using Motion Capture System and Wearable Sensors for Force Ratio Detection.

Knowledge about the knee cartilage deformation ratio as well as the knee cartilage stress distribution is of particular importance in clinical studies due to the fact that these represent some of the basic indicators of cartilage state and that they also provide information about joint cartilage wear so medical doctors can predict when it is necessary to perform surgery on a patient. In this research, we apply various kinds of sensors such as a system of infrared cameras and reflective markers, three-axis accelerometer, and force plate. The fluorescent marker and accelerometers are placed on the patient's hip, knee, and ankle, respectively. During a normal walk we are recording the space position of markers, acceleration, and ground reaction force by force plate. Measured data are included in the biomechanical model of the knee joint. Geometry for this model is defined from CT images. This model includes the impact of ground reaction forces, contact force between femur and tibia, patient body weight, ligaments, and muscle forces. The boundary conditions are created for the finite element method in order to noninvasively determine the cartilage stress distribution.

Mesenchymal stem cell implantation in knee osteoarthritis: an assessment of the factors influencing clinical outcomes.

BACKGROUND: Several clinical studies have reported on cell-based treatment using mesenchymal stem cells (MSCs) for cartilage regeneration in knee osteoarthritis (OA). However, little is known about the factors that influence the clinical outcomes after surgery. PURPOSE/HYPOTHESIS: This study aimed to investigate the clinical outcomes of MSC implantation in patients with knee OA and assess the factors that are associated with clinical outcomes. The hypothesis was that factors may exist that could influence clinical outcomes. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A total of 49 patients (55 knees) were retrospectively evaluated after MSC implantation for knee OA. The inclusion criteria were patients who had an isolated full-thickness cartilage lesion and Kellgren-Lawrence OA grade 1 or 2. Clinical outcomes were measured with the International Knee Documentation Committee (IKDC) score, Tegner activity score, and patients' overall satisfaction with the surgery. Statistical analyses were performed to determine the effect of different factors on the clinical outcome. RESULTS: The mean pre- and postoperative IKDC and Tegner activity scores significantly improved from 37.7 ± 6.3 to 67.3 ± 9.5 (IKDC) and from 2.2 ± 0.7 to 3.8 ± 0.7 (Tegner) (P < .001 for both). Twenty-four patients reported their overall satisfaction with the surgery as excellent (43.6%), 17 as good (30.9%), 11 as fair (20.0%), and 3 as poor (5.5%). There were significant differences in clinical outcomes at the final follow-up among the age and lesion size groups (P < .05 for all). Multivariate analyses showed high prognostic significance related to patient age and lesion size, and scatter plots suggested a cutoff age of 60 years and a cutoff lesion size of 6.0 cm(2) for the optimum identification of poor clinical outcomes (P < .05 for both). CONCLUSION: The clinical outcomes of MSC implantation for knee OA are encouraging. Patient age and lesion size are important factors that affect clinical outcomes; thus, these may serve as a basis for preoperative surgical decisions. Cutoff points exist for the risk of clinical failure in patients older than 60 years and those with a lesion size larger than 6.0 cm(2).

The design and development of a high-throughput magneto-mechanostimulation device for cartilage tissue engineering.

To recapitulate the in vivo environment and create neo-organoids that replace lost or damaged tissue requires the engineering of devices, which provide appropriate biophysical cues. To date, bioreactors for cartilage tissue engineering have focused primarily on biomechanical stimulation. There is a significant need for improved devices for articular cartilage tissue engineering capable of simultaneously applying multiple biophysical (electrokinetic and mechanical) stimuli. We have developed a novel high-throughput magneto-mechanostimulation bioreactor, capable of applying static and time-varying magnetic fields, as well as multiple and independently adjustable mechanical loading regimens. The device consists of an array of 18 individual stations, each of which uses contactless magnetic actuation and has an integrated Hall Effect sensing system, enabling the real-time measurements of applied field, force, and construct thickness, and hence, the indirect measurement of construct mechanical properties. Validation tests showed precise measurements of thickness, within 14 µm of gold standard calliper measurements; further, applied force was measured to be within 0.04 N of desired force over a half hour dynamic loading, which was repeatable over a 3-week test period. Finally, construct material properties measured using the bioreactor were not significantly different (p=0.97) from those measured using a standard materials testing machine. We present a new method for articular cartilage-specific bioreactor design, integrating combinatorial magneto-mechanostimulation, which is very attractive from functional and cost viewpoints.

Cartilage assessment of the metacarpophalangeal joints: cadaveric study with magnetic resonance arthrography and finger traction.

We investigated the efficacy of axial traction of the fingers combined with magnetic resonance (MR) arthrography in assessing the metacarpophalangeal (MCP) joint cartilage in cadavers. Cartilage was imaged and graded before/after MR arthrography, with/without traction, then correlated with cadaveric sectioning. The application of traction with MR arthrography is a promising technique for improved visualization of the articular cartilage of the MCP joints compared with similar imaging without traction and/or without arthrography, but its true benefit requires further study.