Evaluation of the Transfemoral Bone-Implant Interface Properties Using Vibration Analysis.

Evaluating the bone-implant interface (BII) properties of osseointegrated transfemoral (TFA) implants is important for early failure detection and prescribing loads during rehabilitation. The objective of this work is to derive and validate a 1D finite element (FE) model of the Osseointegrated Prosthetic Limb (OPL) TFA system that can: (1) model its dynamic behaviour and (2) extract the BII properties. The model was validated by: (1) comparing the 1D FE formulation to the analytical and 3D FE solutions for a simplified cylinder, (2) comparing the vibration modes of the actual TFA geometry using 1D and 3D FE models, and (3) evaluating the BII properties for three extreme conditions (LOW, INTERMEDIATE, and HIGH) generated using 3D FE and experimental (where the implant was embedded, using different adhesives, in synthetic femurs) signals for additional validation. The modes predicted by the 1D FE model converged to the analytical and the 3D FE solutions for the cylinder. The 1D model also matched the 3D FE solution with a maximum frequency difference of 2.02% for the TFA geometry. Finally, the 1D model extracted the BII stiffness and the system's damping properties for the three conditions generated using the 3D FE simulations and the experimental INTERMEDIATE and HIGH signals. The agreement between the 1D FE and the 3D FE solutions for the TFA geometry indicates that the 1D model captures the system's dynamic behaviour. Distinguishing between the different BII conditions demonstrates the 1D model's potential use for the non-invasive clinical evaluation of the TFA BII properties.

The effect of simulated radiation induced fibrosis on tongue protrusion.

Radiation therapy (RT) is an important adjuvant and primary treatment modality for head and neck cancers. A severe side effect of RT is fibrosis or scarring of muscle tissues of the oral cavity including the tongue. Previous studies have demonstrated that increased radiation doses to the oral cavity structures have led to decrements in function, hypothesized to result from changes in muscle tissue properties that affect the tongue's function. To understand the complex relationship between tongue muscle fibrosis and tongue function, the current study used a virtual biomechanical model of the tongue. Fibrosis parameters including density (high, low), area (large, small) and location (946 node centres) were systematically varied in the model to test its impact on a target tongue tip motion (protrusion). The impact of fibrosis lesion parameters on three directional components of the tip (anterior-inferior, lateral-medial, and superior-inferior) were analyzed using multi linear regression models. Increases in density and area of fibrosis significantly predicted tongue protrusion movements compared to baseline. In the anterior-posterior direction, reductions in the tongue protrusion were observed. In the inferior-superior direction, the tongue height remained above baseline for the majority of cases. In the lateral-medial direction, ipsilateral deviations were observed. The location of fibrosis modulated these three main effects by either amplifying the observed effect or minimizing it. The findings support the hypothesis that changes in muscle tissue properties because of fibrosis impact tongue function. Increases in density and area of fibrosis impact key muscles in the target motion. The range of modulating effects of the lesion location (i.e., either amplifying or minimizing certain impact patterns) highlights the intricacy of tongue anatomy/soft tissue biomechanics and may suggest that lesions in any location will compromise the tongue's movement.

Inverse finite element analysis for an axisymmetric model of vertical tooth extraction.

BACKGROUND AND OBJECTIVE: Tooth extraction is a common clinical procedure with biomechanical factors that can directly influence patient outcomes. Recent development in atraumatic extraction techniques have endeavoured to improve treatment outcomes, but the characterization of extraction biomechanics is sparse. An axisymmetric inverse finite element (FE) approach is presented to represent the biomechanics of vertical atraumatic tooth extraction in an ex-vivo swine model. METHODS: Geometry and boundary conditions from the model are determined to match the extraction of swine incisors in a self-aligning ex vivo extraction experiment. Material parameters for the periodontal ligament (PDL) model are determined by solving an inverse FE problem using clusters of data obtained from 10 highly-controlled mechanical experiments. A seven-parameter visco-hyperelastic damage model, based on an Arruda-Boyce framework, is used for curve fitting. Three loading schemes were fit to obtain a common set of material parameters. RESULTS: The inverse FE results demonstrate good predictions for overall force-time curve shape, peak force, and time to peak force. The fit model parameters are sufficiently consistent across all three cases that a coefficient-averaged model was taken that compares well to all three cases. Notably, the initial modulus ,u, converged across trials to an average value of 0.472 MPa with an average viscoelastic constant g of 0.561. CONCLUSIONS: The presented model is found to have consistent parameters across loading cases. The capability of this model to represent the fundamental mechanical characteristics of the dental complex during vertical extraction loading is a significant advancement in the modelling of extraction procedures. Future work will focus on verifying the model as a predictive design tool for assessing new loading schemes in addition to investigating its applications to subject-specific problems.

Evaluation of a vibration modeling technique for the in-vitro measurement of dental implant stability.

The Advanced System for Implant Stability Testing (ASIST) is a device currently being developed to noninvasively measure implant stability by estimating the mechanical stiffness of the bone-implant interface, which is reported as the ASIST Stability Coefficient (ASC). This study's purpose was to determine whether changes in density, bonding, and drilling technique affect the measured vibration of a dental implant, and whether they can be quantified as a change in the estimated BII stiffness. Stability was also measured using RFA, insertion torque (IT) and the pullout test. Bone-level tapered implants (4.1 mm diameter, 10 mm length) were inserted in polyurethane foam as an artificial bone substitute. Samples were prepared using different bone densities (20, 30, 40 PCF), drilling sequences, and superglue to simulate a bonded implant. Measurements were compared across groups at a significance level of 0.05. The ASC was able to indicate changes in each factor as a change in the interfacial stiffness. IT and pullout force values also showed comparable increases. Furthermore, the relative difference in ISQ values between experimental groups was considerably smaller than the ASC. While future work should be done using biological bone and in-vivo systems, the results of this in-vitro study suggest that modelling of the implant system with a vibration-based approach may provide a noninvasive method of assessing the mechanical stability of the implant.

Jumping into recovery: A systematic review and meta-analysis of discriminatory and responsive force plate parameters in individuals following anterior cruciate ligament reconstruction during countermovement and drop jumps.

Purpose: Comprehensive understanding of force plate parameters distinguishing individuals postprimary anterior cruciate ligament reconstruction (ACLR) from healthy controls during countermovement jumps (CMJ) and/or drop jumps (DJ) is lacking. This review addresses this gap by identifying discriminative force plate parameters and examining changes over time in individuals post-ACLR during CMJ and/or DJ. Methods: We conducted a systematic review and meta analyses following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines. Nine databases were searched from inception to March 2022. We included cross-sectional papers comparing post-ACLR with healthy controls or longitudinal studies of individuals at least 6 months postprimary ACLR while performing CMJ and/or DJ on force plates. The methodological quality was appraised using the Modified Downs and Black Checklist. Results: Thirty-three studies including 1185 (50.38%) participants post-ACLR, and 1167 (49.62%) healthy controls, were included. Data were categorised into single-leg CMJ, double-leg CMJ, single-leg DJ, and double-leg DJ. Jump height was reduced in both single (mean difference [MD] = -3.13; p < 0.01; 95% confidence interval [CI]: [-4.12, -2.15]) and double-leg (MD = -4.24; p < 0.01; 95% CI: [-5.14, -3.34]) CMJs amongst individuals with ACLR. Similarly, concentric impulse and eccentric/concentric impulse asymmetry could distinguish between ACLR (MD = 3.42; p < 0.01; 95% CI: [2.19, 4.64]) and non-ACLR (MD = 5.82; p < 0.01; 95% CI: [4.80, 6.80]) individuals. In double-leg DJs, peak vertical ground reaction forces were lower in the involved side (MD = -0.10; p = 0.03; 95% CI: [-0.18, -0.01]) but higher in the uninvolved side (MD = 0.15; p < 0.01; 95% CI: [0.10, 0.20]) when compared to controls and demonstrated significant changes between 6 months and 3 years post-ACLR. Conclusion: This study identified discriminative kinetic parameters when comparing individuals with and without ACLR and also monitored neuromuscular function post-ACLR. Due to heterogeneity, a combination of parameters may be required to better identify functional deficits post-ACLR. Level of Evidence: Level III.

Effect of adding Schroth physiotherapeutic scoliosis specific exercises to standard care in adolescents with idiopathic scoliosis on posture assessed using surface topography: A secondary analysis of a Randomized Controlled Trial (RCT).

BACKGROUND: Adolescent idiopathic scoliosis (AIS) is a three-dimensional structural asymmetry of the spine and trunk affecting 2-4% of adolescents. Standard treatment is observation, bracing, and surgery for small, moderate, and large curves, respectively. Schroth exercises aim to correct posture and reduce curve progression. PURPOSE: This study aimed to determine the effect of Schroth exercises added to the standard care compared to standard care alone on torso asymmetry in AIS. METHODS: In a randomized controlled trial (NCT01610908), 124 participants with AIS (age: 10-18, Cobb: 10°-45°, Risser: ≤3) were randomly assigned to the control (Standard care only) or Schroth (Standard care + Schroth treatment) group. Schroth treatment consisted of 1-hour weekly supervised sessions and 30-45 minutes of daily home exercises for six months. The control group received Schroth exercises in the last six months of the 1-year monitoring period. Markerless 3D surface topography assessed torso asymmetry measured by maximum deviation (MaxDev) and root mean square (RMS). Intention to treat linear mixed effects model analysis was compared to the per protocol analysis. RESULTS: In the intention to treat analysis, the Schroth group (n = 63) had significantly larger decreased RMS (-1.2 mm, 95%CI [-1.5,-0.9]mm, p = 0.012) and MaxDev (-1.9mm, 95%CI [-2.4,-1.5]mm, p = 0.025) measurements compared to controls (n = 57) after six months of intervention. In the per protocol analysis (Schroth n = 39, control n = 36), the Schroth group also had a significantly larger decrease compared to the control in both the RMS (-1.0mm, 95%CI [-1.9, -0.2]mm, p = 0.013) and MaxDev measurements (-2.0mm, 95%CI [-3.3,-0.5]mm, p = 0.037). For the control group, both the intention to treat and per protocol analysis showed no difference in RMS and MaxDev in the last six months of Schroth intervention (p>0.5). CONCLUSION: Schroth Exercise treatment added to standard care (observation or bracing) reduced asymmetry measurements in AIS. As expected, a greater effect was observed for participants who followed the prescribed exercise treatment per protocol.

Biomechanical Comparison of Distal Radioulnar Joint Reconstruction Graft Preparation Techniques.

Background Graft preparation techniques for the Adams-Berger distal radioulnar joint (DRUJ) reconstruction vary among surgeons with insufficient evidence to support any specific technique. Questions/Purposes We compared survival with cyclic loading, absolute elongation, elongation rate, and modes of failure of four graft preparation techniques. Methods Fifteen porcine extensor tendons were divided into three equal groups: tendon only; tendon augmented along its full length with nonlocking 2-0 FiberLoop suture spaced at 6 mm intervals; and tendon with suture at 12 mm intervals. Suture only was also tested. Samples were woven through custom radius- and ulna-simulating jigs mounted on a mechanical testing machine. Samples underwent a staircase cyclic loading protocol and were then inspected visually for the mode of failure. Survival with cyclic loading, absolute elongation, and elongation rate was compared. Results Average survival with cyclic loading of suture-augmented tendon was significantly higher than tendon only. All tendon groups had significantly higher survival compared with suture only. Absolute elongation was subject to variability due to initial nonlinear elongation behavior of samples. The elongation rate was significantly lower with suture compared with all tendon groups. Modes of failure included rupture of the tendon and/or suture at the simulated graft-bone interface and elongation of the entire construct without rupture. Conclusions In this biomechanical study, augmentation of porcine tendons with suture spaced at either 6 or 12 mm for DRUJ reconstruction significantly increased survival to a staircase cyclic loading protocol Clinical Relevance For the Adams-Berger reconstruction, tendon grafts augmented along their entire length by nonabsorbable braided suture are biomechanically superior to tendon alone.

Algorithmically designed flaps in tongue reconstruction: a feasibility analysis.

PURPOSE: Despite the significance and complexity of tongue reconstruction surgery, a digital tool for flap design is currently lacking. This study investigates the effectiveness of employing inverse finite element method (IFEM) for meticulously designing the geometric characteristics of harvested tissue (free flap) for tongue reconstruction. METHODS: In the case of an artificially simulated hemiglossectomy, IFEM algorithm was applied for algorithmic flap design. The method's effectiveness was evaluated by assessing flap deformation in a simplified virtual reconstruction, focusing on parameters such as stress, strain, and thickness. RESULTS: The IFEM algorithm successfully generated an optimal flap design for the intended surgical removal. Analysis of the flap's overall surface area, deformation characteristics, and safety margins demonstrated the feasibility of the deformation. Notably, the stress and thickness assessments suggested that the flap's tension post-surgery would not adversely affect the mobility of the reconstructed tongue, suggesting a positive outcome for functional recovery. CONCLUSION: The IFEM demonstrates significant potential as a tool for precise free flap design in tongue reconstruction surgeries. Its application could lead to improved surgical accuracy and better quality of life for patients undergoing such procedures.

Development and validation of a novel ankle joint musculoskeletal model.

An improved understanding of contact mechanics in the ankle joint is paramount for implant design and ankle disorder treatment. However, existing models generally simplify the ankle joint as a revolute joint that cannot predict contact characteristics. The current study aimed to develop a novel musculoskeletal ankle joint model that can predict contact in the ankle joint, together with muscle and joint reaction forces. We modelled the ankle joint as a multi-axial joint and simulated contact mechanics between the tibia, fibula and talus bones in OpenSim. The developed model was validated with results from experimental studies through passive stiffness and contact. Through this, we found a similar ankle moment-rotation relationship and contact pattern between our study and experimental studies. Next, the musculoskeletal ankle joint model was incorporated into a lower body model to simulate gait. The ankle joint contact characteristics, kinematics, and muscle forces were predicted and compared to the literature. Our results revealed a comparable peak contact force and the same muscle activation patterns in four major muscles. Good agreement was also found in ankle dorsi/plantar-flexion and inversion/eversion. Thus, the developed model was able to accurately model the ankle joint and can be used to predict contact characteristics in gait.

An analytical model to measure dental implant stability with the Advanced System for Implant Stability Testing (ASIST).

A non-invasive method of quantitatively assessing dental implant stability is important to monitor its long-term health. The Advanced System for Implant Stability Testing (ASIST) is a noninvasive technique that couples the impact technique with a linear vibration model of the implant system, such that the measured signal can be used to determine a matching analytical response. The purpose of this study was to evaluate the ASIST technique by comparing stability estimates obtained from artificial implant installations with various abutments. Two Straumann dental implants were installed in four densities of uniform polyurethane foam, and the stability of each installation was measured using different healing abutments and artificial dental crowns. With the ASIST, values for the estimated interfacial stiffness increased with foam density and did not significantly change with abutment type for a specific sample. This provides evidence that the analytical model is representative of the physical system. Current methods, such as resonance frequency analysis, interpret the interface stiffness based on a single frequency measurement. With the ASIST, the measured signal provides information about the first and second modes of vibration of the implant system, both of which are influenced by the properties of the corresponding abutment. The consideration of both modes allows the technique to reliably measure the interfacial stiffness independently of the system components. As a result, the ASIST technique may provide an improved non-invasive method of measuring the stability of dental implants.

A novel method for simulating ex vivo tooth extractions under varying applied loads.

BACKGROUND: Tooth extraction is a common surgical procedure where the invasiveness of the surgery can affect the nature of the dentoalveolar remodelling which follows. However, there is very little biomechanical data relating the loading applied during tooth extraction to the outcomes of the procedure. The purpose of this pilot study is to present a novel ex vivo experimental method for measuring tooth extraction mechanics and to explore preliminary metrics for predicting extraction success. METHODS: A custom experimental apparatus was developed in-house to extract central incisors from ex vivo swine mandible samples. Twenty-five (n = 25) incisors were extracted at different rates in displacement- and force-control, along with an intermittent ramp-hold scheme for a total of five schemes. Peak forces and extraction success were recorded for each test. Video analysis assisted in determining the instantaneous stiffnesses of the dental complex during continuous extractions, which were compared using the K-means clustering algorithm. FINDINGS: Tooth extraction forces ranged from 102 N to 309 N, with higher-rate tests tending towards higher peak forces (141 N - 308 N) than the lower-rate tests (102 N-204 N) for displacement- and force-controlled schemes. The K-means algorithm clearly identified load rates among tests, indicating that higher-rate loading increased system stiffness relative to the lower-rate tests. INTERPRETATION: The developed experimental method demonstrated a desirable degree of control. The preliminary results suggest the influence of load rate on the mechanical response of the dental complex and extraction outcome. Future work will further investigate the biomechanics of tooth extraction and relate them to tissue damage to improve future tooth extraction procedures.

Comparison of wear on articular cartilage by titanium alloy, ultra-high-molecular-weight polyethylene, and carbon fibre reinforced polyether-ether-ketone: A pilot study.

Artificial implant materials may articulate against native articular cartilage in certain clinical scenarios and the selection of an implant material that results in the least wear on articular cartilage is preferred to maintain normal joint architecture and function. This project compared the wear on porcine femoral condyles induced by articulation against porcine patellae, titanium alloy (Ti6Al4V), ultra high molecular weight polyethylene (UHMWPE), and carbon fibre reinforced polyether-ether-ketone (CFR-PEEK) through an ex vivo experimental setup. A sinusoidal compressive load of 30-160 N, representing an approximate joint pressure of 0.19-1 MPa at a frequency of 3 Hz coupled with a rotational displacement of +/- 10° at 3 Hz was used to simulate physiological joint motion. Wear was characterized via gross examination and histologically using the OARSI scoring system after 43,200 cycles. CFR-PEEK resulted in the most significant wear on articular cartilage compared to titanium alloy and UHMWPE whereas titanium alloy and UHMWPE resulted in similar levels of wear. All materials caused more wear compared to cartilage-on-cartilage testing. The wear mechanism was characterized by progressive loss of proteoglycan content in cartilage in histology samples.

A comparison of stiffness of six knee braces with application for posterolateral corner reconstructions.

Posterolateral corner knee injuries are clinically significant, and often require surgical reconstruction. The optimal knee brace following posterolateral corner reconstructions has not yet been determined via clinical nor biomechanical study. We sought to evaluate the stiffness of six types of knee braces to determine the ideal brace type for reducing varus forces, which may have clinical utility for posterolateral corner knee reconstruction rehabilitation. Six different groups of knee braces underwent mechanical testing: cruciate braces, cruciate braces with a valgus bend, medial unloaders, articulating sleeves, hinged braces, and tri-panel immobilizers. Each brace was fitted to the same fiberglass leg model and was secured to the testing apparatus. Force was applied under four-point bending to generate a varus moment about the artificial knee. The stiffness in Newtons per millimeter (N/mm) of each brace was calculated from the slope of the force-displacement curve. The cruciate brace with a valgus bend had the highest average stiffness at 192.61 N/mm (SD 28.53). The articulating sleeve was the least stiff with an average stiffness of 49.86 N/mm (SD 8.99). Stiffness of the cruciate brace was not statistically different compared to cruciate valgus (p = 0.083) or medial unloader (p = 0.098). In this experimental design, a cruciate brace with a valgus bend was shown to have the highest overall stiffness, while an articulating sleeve had the lowest stiffness. Future work will investigate whether this translates into clinical performance.

Mechanical Properties of Fresh, Frozen and Vitrified Articular Cartilage.

Osteochondral allograft transplantations are typically used to treat focal articular cartilage injuries where the damaged cartilage is replaced with fresh cadaveric donor grafts. Despite the notable success rate of this procedure, it is limited by fresh donor tissue availability which can only be stored for approximately 28 days after harvest. Vitrification, a form of cryopreservation, can extend the storage time of cartilage. Although it has shown to preserve chondrocyte viability, its effect on the mechanical properties of the tissue has not been thoroughly investigated. Therefore, in this study, the mechanical properties of fresh, frozen, and vitrified articular cartilage were evaluated through unconfined compression testing. Results showed that the peak modulus, equilibrium modulus, and relaxation time constants of the vitrified and control samples (tested one day after harvest) were similar and higher than the fresh (tested 21 days after harvest) and frozen samples. This demonstrated that vitrification does not adversely affect the mechanical properties of cartilage and can be used as an alternative to fresh allografts which are limited by storage time. The fresh samples also had inferior mechanical properties compared to the control samples suggesting that vitrified allografts could potentially improve clinical outcomes in addition to increasing donor tissue availability.

Non-hypertrophic chondrogenesis of mesenchymal stem cells through mechano-hypoxia programing.

Cartilage tissue engineering aims to generate functional replacements to treat cartilage defects from damage and osteoarthritis. Human bone marrow-derived mesenchymal stem cells (hBM-MSC) are a promising cell source for making cartilage, but current differentiation protocols require the supplementation of growth factors like TGF-ß1 or -ß3. This can lead to undesirable hypertrophic differentiation of hBM-MSC that progress to bone. We have found previously that exposing engineered human meniscus tissues to physiologically relevant conditions of the knee (mechanical loading and hypoxia; hence, mechano-hypoxia conditioning) increased the gene expression of hyaline cartilage markers, SOX9 and COL2A1, inhibited hypertrophic marker COL10A1, and promoted bulk mechanical property development. Adding further to this protocol, we hypothesize that combined mechano-hypoxia conditioning with TGF-ß3 growth factor withdrawal will promote stable, non-hypertrophic chondrogenesis of hBM-MSC embedded in an HA-hydrogel. We found that the combined treatment upregulated many cartilage matrix- and development-related markers while suppressing many hypertrophic- and bone development-related markers. Tissue level assessments with biochemical assays, immunofluorescence, and histochemical staining confirmed the gene expression data. Further, mechanical property development in the dynamic compression treatment shows promise toward generating functional engineered cartilage through more optimized and longer culture conditions. In summary, this study introduced a novel protocol to differentiate hBM-MSC into stable, cartilage-forming cells.

Quantifying Asymmetry and Performance of Lower Limb Mechanical Muscle Function in Varsity Athletes-Using Non-Countermovement Jumps.

ABSTRACT: Stadnyk, M, Sepehri, M, Cook, M, Adeeb, S, and Westover, L. Quantifying asymmetry and performance of lower limb mechanical muscle function in varsity athletes-using non-countermovement jumps. J Strength Cond Res 37(1): 98-106, 2023-The ability to automatically quantify jump performance and lower limb muscle function in athletes would be beneficial for both training and rehabilitation purposes. Countermovement jumps (CMJs) and non-CMJs (NCMJs) are simple, quick, and require relatively inexpensive equipment to effectively and reliably monitor lower limb function. In a previous study, CMJ characteristics were assessed across different varsity sports. This study is a follow-up study to incorporate NCMJs into assessing jump characteristics of the same sports and investigate the additional information provided by the complementary jump type. The main objective of this study was to look at a means of quantifying the lower limb mechanical muscle function automatically to provide information for rehabilitation and performance purposes in athletes of specific sports. Male and female varsity athletes from 4 different sports completed 5 trials of an NCMJ on dual force plates. An analysis program was developed using Wolfram Mathematica to analyze force-time jump data. Various parameters of interest were generated, including peak force, force-time curve shape classification, jump phase lengths, phase-specific kinetic impulse, asymmetry index, takeoff velocity, jump height, phase-specific center of mass displacements, and reactive strength index modified. Results obtained indicate that similar jump characteristics to the CMJ study can be quantified, which can be used for performance enhancement or injury rehabilitation. Additional data found, such as the ability of an athlete to hold a steady squat during an NCMJ, could also be meaningful in aiding trainers to design programs tailored for athletes.

Compressive mechanical properties of vitrified porcine menisci are superior to frozen and similar to fresh porcine menisci.

The common practice of freezing meniscal allograft tissue is limited due to the formation of damaging ice crystals. Vitrification, which eliminates the formation of damaging ice crystals, may allow the mechanical properties of meniscal allograft tissue to be maintained during storage and long-term preservation. The primary objective of this study was to investigate the differences between fresh, frozen, and vitrified porcine lateral menisci examining compressive mechanical properties in the axial direction. Unconfined compressive stress-relaxation testing was conducted to quantify the mechanical properties of fresh, frozen and vitrified porcine lateral menisci. The compressive mechanical properties investigated were peak and equilibrium stress, secant, instantaneous and equilibrium modulus, percent stress-relaxation, and relaxation time constants from three-term Prony series. Frozen menisci exhibited inferior compressive mechanical properties in comparison with fresh menisci (significant differences in peak and equilibrium stress, and secant, instantaneous and equilibrium modulus) and vitrified menisci (significant differences in peak stress, and secant and instantaneous modulus). Interestingly, fresh and vitrified menisci exhibited comparable compressive mechanical properties (stress, modulus and relaxation parameters). These findings are significant because (1) vitrification was successful in maintaining mechanical properties at values similar to fresh menisci, (2) compressive mechanical properties of fresh menisci were characterized providing a baseline for future research, and (3) freezing affected mechanical properties confirming that freezing should be used with caution in future investigations of meniscal mechanical properties. Vitrification was superior to freezing for preserving compressive mechanical properties of menisci which is an important advance for vitrification as a preservation option for meniscal allograft transplantation.

Mechanical Unloading of Engineered Human Meniscus Models Under Simulated Microgravity: A Transcriptomic Study.

Osteoarthritis (OA) primarily affects mechanical load-bearing joints, with the knee being the most common. The prevalence, burden and severity of knee osteoarthritis (KOA) are disproportionately higher in females, but hormonal differences alone do not explain the disproportionate incidence of KOA in females. Mechanical unloading by spaceflight microgravity has been implicated in OA development in cartilaginous tissues. However, the mechanisms and sex-dependent differences in OA-like development are not well explored. In this study, engineered meniscus constructs were generated from healthy human meniscus fibrochondrocytes (MFC) seeded onto type I collagen scaffolds and cultured under normal gravity and simulated microgravity conditions. We report the whole-genome sequences of constructs from 4 female and 4 male donors, along with the evaluation of their phenotypic characteristics. The collected data could be used as valuable resources to further explore the mechanism of KOA development in response to mechanical unloading, and to investigate the molecular basis of the observed sex differences in KOA.

Vitrified Particulated Articular Cartilage for Joint Resurfacing: A Swine Model.

BACKGROUND: The use of particulated articular cartilage for repairing cartilage defects has been well established, but its use is currently limited by the availability and short shelf life of donor cartilage. Vitrification is an ice-free cryopreservation technology at ultralow temperatures for tissue banking. An optimized vitrification protocol has been developed for particulated articular cartilage; however, the equivalency of the long-term clinical efficacy of vitrified particulated articular cartilage compared with fresh articular cartilage has not yet been determined. HYPOTHESIS: The repair effect of vitrified particulated cartilage from pigs would be equivalent to or better than that of fresh particulated cartilage stored at 4°C for 21 days. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 19 pigs were randomly divided into 3 experimental groups: fresh particulated cartilage group (n = 8), vitrified particulated cartilage group (n = 8), and negative control group (no particulated cartilage in the defect; n = 3). An additional pig was used as the initial cartilage donor for the first set of surgical procedures. Pigs were euthanized after 6 months to obtain femoral condyles, and the contralateral condyle was used as the positive (no defect) control. Samples were evaluated for gross morphology using the Outerbridge and Osteoarthritis Research Society International (OARSI) scoring systems, histology (safranin O, collagen type I/II, DAPI), and chondrocyte viability using live-dead membrane integrity staining. RESULTS: There were no infections after surgery, and all 19 pigs were followed for the duration of the study. The OARSI grades for the fresh and vitrified particulated cartilage groups were 2.44 ± 1.35 and 2.00 ± 0.80, respectively, while the negative control group was graded significantly higher at 4.83 ± 0.29. Analysis of histological and fluorescent staining demonstrated that the fresh and vitrified particulated cartilage groups had equivalent regeneration within cartilage defects, with similar cell viability and densities and expression of proteoglycans and collagen type I/II. CONCLUSION: The implantation of fresh or vitrified particulated cartilage resulted in the equivalent repair of focal cartilage defects when evaluated at 6 months after surgery. CLINICAL RELEVANCE: The vitrification of particulated cartilage is a viable option for long-term storage for cartilage tissue banking and could greatly increase the availability of donor tissue for transplantation.

Effect of vitrification on mechanical properties of porcine articular cartilage.

Articular cartilage (AC) injuries do not heal primarily and large lesions progress to degenerative osteoarthritis. Osteochondral allograft transplantation is an effective surgical treatment but is limited by the lack of donor tissue availability. Fresh allografts can be stored hypothermically up to 28-45 days after which the tissue is no longer viable for transplantation. Vitrification is a method of cryopreservation with the potential to extend the storage time of AC. A specific protocol has been demonstrated to preserve high chondrocyte viability; however, its effect on various mechanical properties of the extracellular matrix (ECM) remains unknown and is the focus of this initial study. Porcine AC was subject to a defined vitrification protocol, using fresh and frozen samples as positive and negative controls, respectively; n = 20 for all three groups. Unconfined compression testing was used to assess mechanical properties of the tissue under rapid load, stress relaxation, and equilibrium conditions. The stress relaxation time constants (modeled with a 2-term Prony series) τ1 and τ2 were significantly lower for frozen (p = 0.014, p < 0.001) and vitrified (p = 0.009, p = 0.003) tissue compared to fresh, with no differences between frozen and vitrified samples (p = 0.848 and 0.105 for τ1 and τ2, respectively). These values indicate that frozen and vitrified samples relaxed more rapidly than fresh, which may suggest altered matrix composition and permeability post-treatment. These results represent the initial study in our experimental path to evaluate differences in mechanical properties of vitrified tissues.