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Microscale strain mapping demonstrates the importance of interface slope in the mechanics of cartilage repair.

ABSTRACT: Achieving lateral integration of articular cartilage repair tissue with surrounding native cartilage remains a clinical challenge. Histological and bulk mechanical studies have identified extracellular matrix components that correlate with superior failure strength, but it is unclear how local changes in geometry and composition at the repair interface affect tissue strains under physiologic loading. Here, we investigated the effects of local compositional and interface geometry on lateral cartilage repair integration by coupling microscale Raman spectroscopy and confocal elastography to measure tissue strains under compressive and shear loading. Histological integration assessments did not have significant relationships with interface strains under compressive loading (p > 0.083) and only the perimeter attachment score was trending towards statistical significance with the |E_xy| strain tensor under shear loading (p = 0.050). Interface slope had a stronger correlation with local tissue strains under compressive and shear loading compared to compositional measures of GAG, collagen, or proteins (compressive loading |E_yy| tensor: R² = 0.400 (interface slope), 0.005 (GAG), 0.024 (collagen), and 0.012 (protein); shear loading |E_xy| tensor: R² = 0.457 (interface slope), 0.003 (GAG), 0.006 (collagen), and 0.000 (total protein)). These data support surgical publications detailing the need for vertical walls when debriding chondral defects. Current histological integration assessments and local compositional measures were insufficient for identifying the variation in interface strains under compressive and shear loading. Thus, our data points to the importance of controlling interface geometry at the time of surgery, which has implications for cartilage repair integration and long-term healing.

SUBMITTER: Irwin RM

PROVIDER: S-EPMC7808171 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundQuantification of dynamic biomechanical strain in articular cartilage in vivo; in situ using noninvasive MRI techniques is desirable and may potentially be used to assess joint pathology.PurposeTo demonstrate the use of static mechanical loading and continuous 3D-MRI acquisition of the human knee joint in vivo to measure the strain in the tibiofemoral articular cartilage.Study typeProspective.SubjectsFive healthy human volunteers (four women, one man; age 25.6?±?1.7) underwent MRI at rest, under static mechanical loading condition, and during recovery.Field strength/sequenceA field strength of 3T was used. The sequence used was 3D-continuous golden angle radial sparse parallel (GRASP) MRI and compressed sensing (CS) reconstruction.AssessmentTibiofemoral cartilage deformation maps under loading and during recovery were calculated using an optical flow algorithm. The corresponding Lagrangian strain was calculated in the articular cartilage.Statistical testsRange of displacement and strain in each subject, and the resulting mean and standard deviation, were calculated.ResultsDuring the loading condition, the cartilage displacement in the direction of loading ranged from a minimum of -673.6?±?121.9 ?m to a maximum of 726.5?±?169.5 ?m. Corresponding strain ranged from a minimum of -7.0?±?4.2% to a maximum of 5.4?±?1.6%. During the recovery condition, the cartilage displacement in the same direction reduced to a minimum of -613.0?±?129.5 ?m and a maximum of 555.7?±?311.4 ?m. The corresponding strain range reduced to a minimum of -1.6?±?7.5% to a maximum of 4.2?±?2.6%.Data conclusionThis study shows the feasibility of using static mechanical loading with continuous GRASP-MRI acquisition to measure the strain in the articular cartilage. By measuring strain during the loading and recovery phases, dynamic strain information in the articular cartilage might be able to be investigated.Level of evidence2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:426-434.

Project description:The efficacy and safety of BST-CarGel, a chitosan-based medical device for cartilage repair, was compared with microfracture alone at 1 year during a multicenter randomized controlled trial (RCT) in the knee. The quality of repair tissue of osteochondral biopsies collected from a subset of patients was compared using blinded histological assessments.The international RCT evaluated repair tissue quantity and quality by 3-dimensional quantitative magnetic resonance imaging as co-primary endpoints at 12 months. At an average of 13 months posttreatment, 21/41 BST-CarGel and 17/39 microfracture patients underwent elective second look arthroscopies as a tertiary endpoint, during which ICRS (International Cartilage Repair Society) macroscopic scoring was carried out, and osteochondral biopsies were collected. Stained histological sections were evaluated by blinded readers using ICRS I and II histological scoring systems. Collagen organization was evaluated using a polarized light microscopy score.BST-CarGel treatment resulted in significantly better ICRS macroscopic scores (P = 0.0002) compared with microfracture alone, indicating better filling, integration, and tissue appearance. Histologically, BST-CarGel resulted in a significant improvement of structural parameters-Surface Architecture (P = 0.007) and Surface/Superficial Assessment (P = 0.042)-as well as cellular parameters-Cell Viability (P = 0.006) and Cell Distribution (P = 0.032). No histological parameters were significantly better for the microfracture group. BST-CarGel treatment also resulted in a more organized repair tissue with collagen stratification more similar to native hyaline cartilage, as measured by polarized light microscopy scoring (P = 0.0003).Multiple and independent analyses in this biopsy substudy demonstrated that BST-CarGel treatment results in improved structural and cellular characteristics of repair tissue at 1 year posttreatment compared with microfracture alone, supporting previously reported results by quantitative magnetic resonance imaging.

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Microscale strain mapping demonstrates the importance of interface slope in the mechanics of cartilage repair.

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