Compression Of Cartilage Research Articles

Validation of a Novel Handheld Device for Accurate Cricoid Pressure Application on a Laryngotracheal Model

BackgroundCricoid pressure, manual compression of the cricoid cartilage using 30 N of force, is a well-established technique to prevent regurgitation during airway management. However, applying and maintaining the correct force has proven difficult for providers. To address this, we developed a handheld Cricoid Pressure Device, which displays applied force in real time. This study aims to assess the device in terms of its ability to aid providers in applying the correct force. MethodsIn a single centre study, twenty five healthcare providers performed cricoid pressure for three 60-second trials on a laryngotracheal model under three conditions: 1) Standard condition with no training, 2) Post-Training condition following syringe model training, and 3) Cricoid Pressure Device condition using our novel device. The primary outcome was the proportion of providers applying pressure within the target range (30 ± 5 N) for at least 95% of the trial duration. Secondary outcomes included providers’ feedback on the usability of the device. ResultsUsing the Cricoid Pressure Device, 92% of providers applied force within the target range for the third trial, compared to 4% in the Standard condition and 8% in the Post-training condition. A logistic mixed effects model indicated that the odds of successful application using the Device were significantly higher than the Standard condition (OR = 482.7; 95% CI 67.7, 3442.5). All participants believed the device would be extremely useful in clinical practice. ConclusionThe Cricoid Pressure Device significantly improved provider’s ability to apply the target cricoid pressure to a laryngotracheal model compared to standard practice.

Histopathological and phylogenetic description of an Amazonian cnidaria microparasite Myxobolus rousseauxii n. sp. infecting the gill arches of Brachyplatystoma rousseauxii (Siluriformes)

From genus Myxobolus, cnidarians of Myxozoa class, is well known for infecting economically important fish species and, as result, relevant losses in aquaculture production can be observed. They are present in a big range of fish in its natural habitat, including the migratory Brachyplatystoma rousseauxii catfish. This study aimed is to develop an integrative characterization of a new species of Myxobolus, located in B. rousseauxii's gills. To accomplish this, 30 specimens of B. rousseauxii catfish were collected from Mosqueiro Island in Pará, Brazil; necropsied and analyzed for morphology, histology and molecular characteristics. Cysts with conjunctival capsule development made up of fibroblasts were observed at the gill arches; such proliferation caused bone tissue loss and cartilage compression. The cysts contained Myxobolus myxospores measuring 9.9 μm of length and 9.6 μm of width, whereas polar capsules were 5.4 μm long and 3.4 μm wide, with 8 to 9 coils of polar tubules. Phylogenetic analyses revealed that new species were included in a subclade alongside species from the same geographic location and infection site that infect Siluriformes fish. Morphological and molecular differences revealed that Myxobolus spp. parasite-host associations through histopathology supporting the designation of a new M. rousseauxii n. sp. species in B. rousseauxii, a commercially important fish.

Advancing our ability to quantify an individual’s habitual motion path and deviation when running

The habitual motion path theory states that exhibiting kinematic differences between running and habitual movement tasks may increase the risk of running-related injury. Staying near one’s habitual motion path when running has been shown to reduce compression of the knee joint cartilage, a proxy for decreased soft tissue loading. Previous efforts to quantify one’s habitual motion path and deviation when running have utilised just one habitual movement and one time point during the stance phase of running. The methodology advancement described in this manuscript focused on advancing habitual motion path theory research by (1) increasing the number of movements for quantifying an individual’s habitual motion path; and (2) utilising the entire stance phase when running to quantify deviations as opposed to one time point. We liken the advancements in the method described in this manuscript as with the first method we were using a ruler to assess one’s habitual motion path and deviations, and now we are using calipers; providing a more accurate understanding of an individual’s unique habitual movement and deviation when running. We also discuss future potential research avenues related to understanding running biomechanics and footwear effects that this tool will allow us to explore.

Review of Thyroid Cartilage Compression of the Vertebral Artery

Thyroid cartilage compression of the Vertebral Artery (VA) has been implicated as a rare cause of Rotational Vertebral Artery Occlusion (RVAO). 10 cases have been reported in the literature. This has a higher tendency to affect males and younger patients than other forms of stroke. Patients present with multiple episodes prior to diagnosis. Radiologic studies prove crucial for confirming this condition. An aberrant VA course appears to be a necessary factor. All cases suffer from right side VA compression by the superior thyroid cornu. Conservative therapy with antiplatelet treatment is employed commonly. Most patients have definitive treatment with surgical resection of the right superior thyroid cornu. Theories proposed for these characteristics include VA dominance, structural variability in the thyroid cartilage between genders and also variable thyroid cartilage ossification. Given these findings, we propose the term “thyro-vertebral artery syndrome” for this condition.

Time-Resolved Quantification of Patellofemoral Cartilage Deformation in Response to Loading and Unloading via Dynamic MRI With Prospective Motion Correction.

In vivo cartilage deformation has been studied by static magnetic resonance imaging (MRI) with in situ loading, but knowledge about strain dynamics after load onset and release is scarce. To measure the dynamics of patellofemoral cartilage deformation and recovery in response to in situ loading and unloading by using MRI with prospective motion correction. Prospective. Ten healthy male volunteers (age: [31.4 ± 3.2] years). T1-weighted RF-spoiled 2D gradient-echo sequence with a golden angle radial acquisition scheme, augmented with prospective motion correction, at 3 T. In situ knee loading was realized with a flexion angle of approximately 40° using an MR-compatible pneumatic loading device. The loading paradigm consisted of 2 minutes of unloaded baseline followed by a 5-minute loading bout with 50% body weight and an unloading period of 38 minutes. The cartilage strain was assessed as the mean distance between patellar and femoral bone-cartilage interfaces as a percentage of the initial (pre-load) distance. Wilcoxon signed-rank tests (significance level: P < 0.05), Pearson correlation coefficient (r). The cartilage compression and recovery behavior was characterized by a viscoelastic response. The elastic compression ([-12.5 ± 3.1]%) was significantly larger than the viscous compression ([-7.6 ± 1.5]%) and the elastic recovery ([10.5 ± 2.1]%) was significantly larger than the viscous recovery ([6.1 ± 1.8]%). There was a significant residual offset strain ([-3.6 ± 2.3]%) across the cohort. A significant negative correlation between elastic compression and elastic recovery was observed (r = -0.75). The in vivo cartilage compression and recovery time course in response to loading was successfully measured via dynamic MRI with prospective motion correction. The clinical relevance of the strain characteristics needs to be assessed in larger subject and patient cohorts. 2 TECHNICAL EFFICACY: Stage 1.

Improving the Mechanical Properties and Tribological Behavior of Sulfobetaine Polyurethane Based on Hydrophobic Chains to Be Applied as Artificial Meniscus.

In the context of meniscus reconstruction in knee joints, current bulk biomaterials fail to meet the clinical demands for both excellent mechanical strength and low coefficient of friction. In this research, zwitterionic polyurethanes (PUs) with varying sulfobetaine (SB) groups were synthesized as the potential materials for artificial meniscus to investigate the relationship between the structures of SB groups and the performances of PUs. Under the saturation condition of 3 mg/mL hyaluronic acid aqueous solution, PU with long-alkyl chains and SB groups (PU-hSB4) exhibited a good tensile modulus (111.5 MPa) because the hydrophobic interaction of carbon chains was able to maintain the ordered aggregations of hard segment domains. Interestingly, hydrophobic chains in the molecular chain could also improve the tribological performance of PU-hSB4 instead of resulting from the surface roughness of samples, the components of lubricants, and the counterface of samples. A thicker and relatively stable hydration layer of noncrystal water was formed on the surface of PU-hSB4, which exhibited superior resistance to external forces compared to other PUs. Even if the hydration layer was damaged, PU-hSB4 was able to resist the compression of cartilage due to its high surface modulus, thus maintaining a similar and stable coefficient of friction (0.15-0.16) to native meniscus (0.18) and excellent wear resistance. In addition, the low cytotoxicity of PU-hSB4 further demonstrated its great potential to be applied in artificial meniscus instead.

Computational and experimental characterizations of the spatiotemporal activity and functional role of TGF-β in the synovial joint

TGF-β is a prominent anabolic signaling molecule associated with synovial joint health. Recent work has uncovered mechanochemical mechanisms that activate the latent form of TGF-β (LTGF-β) in the synovial joint—synovial fluid (SF) shearing or cartilage compression—pointing to mechanobiological phenomena, whereby enhanced TGF-β activity occurs during joint stimulation. Here, we implement computational and experimental models to better understand the role of mechanochemical-activated TGF-β (aTGF-β) in regulating the functional biosynthetic activities of synovial joint tissues. Reaction-diffusion models describe the pronounced role of extracellular chemical reactions—load-induced activation, reversible ECM-binding, and cell-mediated internalization—in modulating the spatiotemporal distribution of aTGF-β in joint tissues. Of note, aTGF-β from SF shearing predominantly acts on cells in peripheral tissue regions (superficial zone [SZ] chondrocytes and synoviocytes) and aTGF-β from cartilage compression acts on chondrocytes through all cartilage layers. Further, ECM reversible binding sites in cartilage act to modulate the temporal delivery of aTGF-β to cells, creating a dynamic where short durations of joint activity give rise to extended periods of aTGF-β exposure at moderated doses. Ex vivo tissue models were subsequently utilized to characterize the influence of physiologic aTGF-β activity regimens in regulating functional biosynthetic activities. Physiologic exposure regimens of aTGF-β in SF induce strong 4-fold to 9-fold enhancements in the secretion rate of the synovial biolubricant, PRG4, from SZ cartilage and synovium explants. Further, aTGF-β inhibition in cartilage over 1-month culture leads to a pronounced loss of GAG content (30–35% decrease) and tissue softening (60–65% EY reduction). Overall, this work advances a novel perspective on the regulation of TGF-β in the synovial joint and its role in maintaining synovial joint health.

A novel assessment of dynamic mechanical properties in different articular cartilage layers

Human articular cartilage, a nonlinear, viscoelastic solid-liquid biphasic tissue, has different mechanical properties and undertakes different functions in different layer. The compression deformation and fatigue damage mechanism of each layer of cartilage is also different when in injury. Compression properties of cartilage can predict cartilage integrity and the likelihood of osteoarthritis. Therefore, the confined and unconfined compression of cartilage is taken to systematically study the dynamic mechanical properties of each layer and reveal the relationship between the dynamic mechanical properties of each cartilage layer and the function of the corresponding cartilage layer. Under confined and unconfined compression conditions, the larger the cyclic loading rate, the greater the deformation rate of each layer. In addition, under the same cyclic loading rate, the superficial layer had the highest deformation rate, followed by the middle layer and the deep layer, which indicates that the deep layer mainly assumes the compression load. Furthermore, under the same loading displacement, the loading stress of cartilage and the deformation rate of each layer in confined compression were greater than those in unconfined compression. Simultaneously, with the increase in the number of loading cycles, the deformation rate in different layers increased first and then stabilized.

Release of Matrix-Bound Growth Factors; the role of increase in Sodium Concentration with Cartilage Compression.

Release of Matrix-Bound Growth Factors; the role of increase in Sodium Concentration with Cartilage Compression.

Non-Surgical Correction of Congenital Ear Anomalies: A Critical Assessment of Caretaker Burdens and Aesthetic Outcomes.

Congenital ear anomalies result from cartilage and skin compression in utero. They can be corrected in infancy before the cartilage hardens and loses its malleability. Caretaker burden of ear molding and its impact on esthetic outcomes has not been studied. Demographic and procedural variables were retrospectively collected for infants who underwent ear molding. Parents were surveyed regarding their experience, caretaker burden, and esthetic outcome. Outside physicians were provided with pre- and post-treatment photographs and asked to rate outcomes. A Likert scale was developed for responses and converted to a numeric score from 1 to 5 with 5 as the most desirable. Seventy-four patients comprising 121 ears were included. Mean age at treatment was 20.1±21.4 days with treatment duration of 21.1±7.7 days. Parental participation in the survey was 70.1%. Questions that queried parents' experiences revealed a "very positive" experience with minor burden related to bathing and cleaning (Mean Likert Score 4.1, Range 1-5). Favorable parent-reported outcomes were obtained regarding anticipated social distress (4.28, 1-5), satisfaction with results (4.27, 1-5), and perception of final appearance (4.18, 1-5). Physician assessments of esthetic outcomes were slightly lower, but favorable between "somewhat effective" and "very effective" (3.46, 1-5). Earlier treatment trended favorably, but did not reach significance. Ear malformations had higher parent-reported satisfaction than ear deformations (4.75±0.46 vs 4.21±1.25, p=0.025). Despite the additional obligation for new parents, infant ear molding is rated low in terms of caretaker burden. Esthetic outcomes are excellent as assessed by parents and physicians. However, caretakers reported higher esthetic outcomes than physician evaluations. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

Matrix-Bound Growth Factors are Released upon Cartilage Compression by an Aggrecan-Dependent Sodium Flux that is Lost in Osteoarthritis.

Articular cartilage is a dense extracellular matrix-rich tissue that degrades following chronic mechanical stress, resulting in osteoarthritis (OA). The tissue has low intrinsic repair especially in aged and osteoarthritic joints. Here, we describe three pro-regenerative factors; fibroblast growth factor 2 (FGF2), connective tissue growth factor, bound to transforming growth factor-beta (CTGF-TGFβ), and hepatoma-derived growth factor (HDGF), that are rapidly released from the pericellular matrix (PCM) of articular cartilage upon mechanical injury. All three growth factors bound heparan sulfate, and were displaced by exogenous NaCl. We hypothesised that sodium, sequestered within the aggrecan-rich matrix, was freed by injurious compression, thereby enhancing the bioavailability of pericellular growth factors. Indeed, growth factor release was abrogated when cartilage aggrecan was depleted by IL-1 treatment, and in severely damaged human osteoarthritic cartilage. A flux in free matrix sodium upon mechanical compression of cartilage was visualised by 23Na -MRI just below the articular surface. This corresponded to a region of reduced tissue stiffness, measured by scanning acoustic microscopy and second harmonic generation microscopy, and where Smad2/3 was phosphorylated upon cyclic compression. Our results describe a novel intrinsic repair mechanism, controlled by matrix stiffness and mediated by the free sodium concentration, in which heparan sulfate-bound growth factors are released from cartilage upon injurious load. They identify aggrecan as a depot for sequestered sodium, explaining why osteoarthritic tissue loses its ability to repair. Treatments that restore matrix sodium to allow appropriate release of growth factors upon load are predicted to enable intrinsic cartilage repair in OA.Significance StatementOsteoarthritis is the most prevalent musculoskeletal disease, affecting 250 million people worldwide.1 We identify a novel intrinsic repair response in cartilage, mediated by aggrecan-dependent sodium flux, and dependent upon matrix stiffness, which results in the release of a cocktail of pro-regenerative growth factors after injury. Loss of aggrecan in late-stage osteoarthritis prevents growth factor release and likely contributes to disease progression. Treatments that restore matrix sodium in osteoarthritis may recover the intrinsic repair response to improve disease outcome.

The mechanical properties of tibiofemoral and patellofemoral articular cartilage in compression depend on anatomical regions

Articular cartilage in knee joint can be anatomically divided into different regions: medial and lateral condyles of femur; patellar groove of femur; medial and lateral plateaus of tibia covered or uncovered by meniscus. The stress–strain curves of cartilage in uniaxially unconfined compression demonstrate strain rate dependency and exhibit distinct topographical variation among these seven regions. The femoral cartilage is stiffer than the tibial cartilage, and the cartilage in femoral groove is stiffest in the knee joint. Compared with the uncovered area, the area covered with meniscus shows the stiffer properties. To investigate the origin of differences in macroscopic mechanical properties, histological analysis of cartilage in seven regions are conducted. The differences are discussed in terms of the cartilage structure, composition content and distribution. Furthermore, the commonly used constitutive models for biological tissues, namely Fung, Ogden and Gent models, are employed to fit the experimental data, and Fung and Ogden models are found to be qualified in representing the stiffening effect of strain rate.

Ulnohumeral joint static cartilage compression is affected by radial head implant size

IntroductionRadiocapitellar joint arthroplasty is a commonly performed procedure, which often leads to early failure or instability. Few studies assess the effect of radiocapitellar joint arthroplasty on the ulnohumeral joint. We hypothesized that static forces of contact (compressing cartilage, or cartilage relaxation contact force) would reveal the effect of varying radial head implant size and elbow position on the ulnohumeral joint. MethodsA minimally–invasive method of measuring cartilage relaxation contact force was utilized in 10 fresh-frozen human cadaveric specimens that did not require significant dissection or intraarticular sensor placement. Specimens were rigidly fixed in various positions of elbow flexion and forearm pronosupination with increasing radial head implant lengths. Uniaxial distracting forces were applied and displacement was repeatedly measured with resultant best-fit polynomial curves to determine inflections corresponding to the force required to overcome static cartilage relaxation as in previous work. FindingsBaseline mean (intra-cadaver) cartilage relaxation contact force was 11.8 N (standard error of the mean = 0.3) at 90° of elbow flexion and neutral rotation. There was little variation within specimens (Intraclass correlation coefficient > 0.94). Cartilage relaxation contact force increased at the ulnohumeral joint with radial head implant overstuffing (> 4 mm, P < 0.05) and elbow flexion (120°, P < 0.001). Pronosupination altered cartilage relaxation contact force in an implant-length independent manner (P < 0.05). InterpretationRadiocapitellar joint arthroplasty implant length and elbow joint position independently contribute to increased cartilage relaxation contact force at the ulnohumeral joint. This further supports attempts at anatomic reconstruction of the radiocapitellar joint to prevent pathologic ulnohumeral joint loading.

GASTROINTESTINAL TUBE INSERTION TECHNIQUES IN CRITICAL PATIENTS: SCOPING REVIEW

ABSTRACT Objective to map the production of knowledge about the different techniques of gastrointestinal tube insertion in critically ill and/or coma patients. Method scope review carried out in December 2020 in ten data sources, following the assumptions established by the Joanna Briggs Institute (2020) and the PRISMA-ScR protocol. Results 25 studies were selected and analyzed, identifying as the main techniques for insertion of gastrointestinal tube in critically ill and/or coma patients: techniques without the aid of instrumentals, such as head flexion, lateral neck pressure, tube freezing, measurement with corrected formula of the tip of the ear-lobe tip-xiphoid process, Sellick´s maneuver, cricoid cartilage compression, SORT maneuver and gastric insufflation. In addition to techniques with the aid of instruments, such as the use of laryngoscopes and video laryngoscopes. It is noteworthy that, in order to facilitate insertion, the use of ultrasound examination, radiological, endoscopic and fluoroscopy were also identified. Conclusions the evidence analyzed reveals that there is no specific gastrointestinal tube insertion technique for universally accepted critically ill patients.

Fractures of the Tibial Plafond: Does the Presence or Absence of a Fibular Fracture Predict Future Morbidity?

Category:Trauma; AnkleIntroduction/Purpose:Surgical management pilon fractures continue to be a challenge for orthopedic surgeons. Despite a staged protocol, anatomic reduction, and stable fixation, many patients will require secondary procedures including ankle arthrodesis to treat painful post-traumatic arthritis. Some investigators have correlated the absorbed energy at the time of the injury with the natural history of the pilon fracture despite the quality of the surgical reconstruction. We hypothesize that the presence of an intact fibula in association with an OTA Type C pilon fracture may be a marker for a strict axial compression mechanism resulting in more severe cartilage compression and a poor late outcome. No studies to date have correlated the presence of an intact fibula to pilon fracture outcomes.Methods:An IRB approved 7-year retrospective study was performed at three Level I Trauma Centers. Inclusion criteria included all adult patients (>=18) with isolated OTA type B or C pilon fractures from 2008 through 2014. All patients were treated in a staged fashion with initial external fixation by fellowship-trained orthopedic traumatologists. The primary outcome measurement was ankle arthrodesis. Secondary measurements included infection. Binary logistic regression models were used to evaluate the prognostic factors of arthrodesis and infection.Results:A total of 239 patients met inclusion criteria for analysis: 33-patients (13.81%) had open injuries, 155 (64.85%) had a C type pilon fracture and 157 fractures (65.69%) presented with an associated fibula fracture. Only 12 patients (5.02%) progressed to ankle arthrodesis. The incidence of fusion in the intact fibula group was 5 (6.10%) similar to that of 7 (4.46%) of patients with an associated fibula fracture. It was found that OTA Type C pilon fractures (OR (95% CI): 6.34 (0.80, 49.98), p=0.08), intact fibulas (OR (95% CI): 1.39 (0.43, 4.53), p=0.58), and open injuries (OR (95% CI): 2.19 (0.56, 8.55), p=0.26) were more likely to result in eventual arthrodesis compared to OTA Type B pilon fractures, fractured fibulas, and closed injuries, respectively.Conclusion:The results of this study suggest an adverse relationship for closed complex pilon fractures with an intact fibula. This was especially pronounced in C type injuries in comparison to type B injuries with a 6.34 odds ratio of subsequent fusion. The data approached statistical significance and may have clinical relevance in the decision making and patient counselling for managing these fractures. Pilon fractures historically have had poor outcomes and a higher rate of secondary surgeries which was surprisingly low in our current study. Further study needs to determine if this observation correlates with improved patient outcomes.

Single-Molecule Stretching Shows Glycosylation Sets Tension in the Hyaluronan-Aggrecan Bottlebrush

Large bottlebrush complexes formed from the polysaccharide hyaluronan (HA) and the proteoglycan aggrecan contribute to cartilage compression resistance and are necessary for healthy joint function. A variety of mechanical forces act on these complexes in the cartilage extracellular matrix, motivating the need for a quantitative description that links their structure and mechanical response. Studies using electron microscopy have imaged the HA-aggrecan brush but require adsorption to a surface, dramatically altering the complex from its native conformation. We use magnetic tweezers force spectroscopy to measure changes in extension and mechanical response of an HA chain as aggrecan monomers bind and form a bottlebrush. This technique directly measures changes undergone by a single complex with time and under varying solution conditions. Upon addition of aggrecan, we find a large swelling effect manifests when the HA chain is under very low external tension (i.e., stretching forces less than ∼1 pN). We use models of force-extension behavior to show that repulsion between the aggrecans induces an internal tension in the HA chain. Through reference to theories of bottlebrush polymer behavior, we demonstrate that the experimental values of internal tension are consistent with a polydisperse aggrecan population, likely caused by varying degrees of glycosylation. By enzymatically deglycosylating the aggrecan, we show that aggrecan glycosylation is the structural feature that causes HA stiffening. We then construct a simple stochastic binding model to show that variable glycosylation leads to a wide distribution of internal tensions in HA, causing variations in the mechanics at much longer length scales. Our results provide a mechanistic picture of how flexibility and size of HA and aggrecan lead to the brush architecture and mechanical properties of this important component of cartilage.

A Synthetic Hydrogel Composite with the Mechanical Behavior and Durability of Cartilage

AbstractThis article reports the first hydrogel with the strength and modulus of cartilage in both tension and compression, and the first to exhibit cartilage‐equivalent tensile fatigue strength at 100 000 cycles. These properties are achieved by infiltrating a bacterial cellulose (BC) nanofiber network with a poly(vinyl alcohol) (PVA)–poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid sodium salt) (PAMPS) double network hydrogel. The BC provides tensile strength in a manner analogous to collagen in cartilage, while the PAMPS provides a fixed negative charge and osmotic restoring force similar to the role of aggrecan in cartilage. The hydrogel has the same aggregate modulus and permeability as cartilage, resulting in the same time‐dependent deformation under confined compression. The hydrogel is not cytotoxic, has a coefficient of friction 45% lower than cartilage, and is 4.4 times more wear‐resistant than a PVA hydrogel. The properties of this hydrogel make it an excellent candidate material for replacement of damaged cartilage.

Local Strain Distribution and Increased Intracellular Ca2+ Signaling in Bovine Articular Cartilage Exposed to Compressive Strain.

Articular cartilage is exposed to compressive strain of approximately 10% under physiological loads in vivo, and intracellular Ca2+ signaling is one of the earliest responses in chondrocytes under this physical stimulation. However, it remains unknown whether compressive strain itself evokes intracellular Ca2+ signaling in chondrocytes located within each layer (from surface to deep) in an equal manner with physiological levels of strain. The purpose of this study, therefore, was to determine the distribution of local strain and increased intracellular Ca2+ signaling in layer-dependent cell populations in response to 10% compressive strain loading. For this purpose, the time course of strain was measured in each layer to calculate layer-specific deformation properties. In addition, layer-specific changes in chondrocyte intracellular Ca2+ signals were recorded over time using a fluorescent Ca2+ indicator, Fluo-3, to establish ratios of cells with increased Ca2+ signaling at each depth of cartilage under static conditions or exposed to compression. The results showed that the surface layer was compressed with a larger strain compared with other layers. Few cells with Ca2+ signaling were observed under static conditions. Percentages of responsive cells within compressed cartilage were higher than those within cartilage under static conditions. However, increased intracellular Ca2+ signals were observed in a prominent number of chondrocytes within the deep layer, but not the surface layer, of compressed cartilage. Our results suggest that at a physiological compression level, Ca2+ is upregulated, but the stimulation of Ca2+ signaling in articular cartilage is not simply defined by local deformation.

Single-Molecule Mechanical Measurements of the Hyaluronan-Aggrecan Bottlebrush

Large bottlebrush complexes formed from the polysaccharide hyaluronan (HA) and the proteoglycan aggrecan contribute to cartilage compression resistance and are necessary for healthy joint function. A variety of mechanical forces act on these complexes in the cartilage extracellular matrix, motivating the need for a quantitative description of their structure and mechanical response. Studies using electron microscopy have imaged the HA-aggrecan brush but require adsorption to a surface, dramatically altering the complex from its native conformation. We use magnetic tweezers force spectroscopy to measure changes in extension and mechanical response of an HA chain as aggrecan monomers bind and form a bottlebrush. This technique directly measures changes undergone by a single complex with time and under varying solution conditions. Upon addition of aggrecan, we find a large swelling effect manifests when the HA chain is under little to no tension (stretching forces less than ~1 pN). Theory of polymer brushes and models of side-chain-induced internal tension show our data are consistent with a polydisperse aggrecan population, attributable to varying degrees of glycosylation. Our results provide a mechanistic picture of how flexibility and size of HA and aggrecan lead to the brush architecture and mechanical properties of this important component of cartilage.

Transfer of osteochondral shell autografts to salvage femoral head impaction injuries in hip trauma patients

IntroductionFemoral head impaction defects are observed with variable severity, as a result of traumatic hip dislocations which can be caused by traffic accidents or seen in professional athletes amongst other mechanisms. Compression of the articular cartilage and the subchondral bone into the femoral head results in irregular articular surfaces influencing the outcome with predisposition to osteoarthritis, and being predictive for the need for delayed total hip replacement. This study reports the outcome after a minimum follow-up (FU) of five years in a consecutive series treated with transfer of osteochondral shell autografts in hips (TOSAH) from the head-neck junction into the defect using surgical hip dislocation. Patients and methodsBetween 06/2007 and 03/2014 a series of twelve consecutive patients (mean age: 35yrs, range 18–53; median Injury Severity Score: 12, range 9–27) sustained a traumatic posterior hip dislocation in combination with acetabular and/or Pipkin fractures and were inter alia treated using TOSAH using surgical hip dislocation. Conversion to total hip replacement (THR) during FU was noted as failure. Patients were clinically (Merle d'Aubigné score) and radiographically assessed for occurrence of osteoarthritis (OA), avascular necrosis (AVN) and/or heterotopic ossification (HO) at a minimal follow-up of five years. ResultsMean follow-up was 6.9 years (5.0–11.6). At five-year follow-up, we found a survivorship of 57.1% (95% Confidence interval {CI}, 46.7–100%). Four patients required conversion to a total hip replacement at 11, 16, 28 and 44 months respectively after the TOSAH procedure due to osteoarthritis progression. One patient required conversion to a total hip replacement 12 months after TOSAH procedure due to AVN. One patient was lost to follow-up after 2.7 years. The remaining six patients with preserved hips presented with a median Merle-d'Aubigné score of 16 points (range: 14–18) and no AVN. Two patients showed asymptomatic grade I osteoarthritis according to Tönnis at latest follow-up and three patients showed mild asymptomatic HO according to Brooker (Grade I-II). ConclusionThe presented technique can be used as a salvage procedure for severely injured hip joints and to preserve the hip joint at midterm with satisfying clinical and radiological outcomes.