The goal of this study was to identify the effect of mismatches in the subchondral bone surface at the native:graft interface on cartilage tissue deformation in human patellar osteochondral allografts (OCA). Hypothesis: large mismatches in the subchondral bone surface will result in higher stresses in the overlying and surrounding cartilage, potentially increasing the risk of graft failure. Nano-CT scans of ten 16mm diameter cadaveric patellar OCA transplants were used to develop simplified and 3D finite element (FE) models to quantify the effect of mismatches in the subchondral bone surface. The simplified model consisted of a cylindrical plug with a 16 mm diameter (graft) and a washer with a 16 mm inner diameter and 36 mm outer diameter (surrounding native cartilage). The thickness of the graft cartilage was varied from 0.33x the thickness of native cartilage (proud graft subchondral bone) to 3x the thickness of native cartilage (sunken graft subchondral bone; Fig. 1). The thickness of the native cartilage was set to 2 mm. The surface of the cartilage in the graft was matched to the surrounding native cartilage. A 1 MPa pressure was applied to the fixed patellar cartilage surface. Scans were segmented using Dragonfly and meshed using HyperMesh. FE simulations were conducted in Abaqus 2019. The simplified model demonstrated that a high stress region occurred in the cartilage at the sharp bony edge between the graft and native subchondral bone, localized to the region with thinner cartilage. A 20% increase in applied pressure occurs up to 50μm away from the graft edge (primarily in the graft cartilage) for grafts with proud subchondral bone but varies little based on the graft cartilage thickness. For grafts with sunken subchondral bone, the size of the high stress region decreases as the difference between graft cartilage and native cartilage thickness decreases (Fig. 2-4), with a 200 μm high stress region occurring when graft cartilage was 3x thicker than native cartilage (i.e., greater graft cartilage thickness produces larger areas of stress in the surrounding native cartilage). The 3D models reproduced the key features demonstrated in the simplified model. Larger differences between native and graft cartilage thickness cause larger high stress regions. Differences between the 3D and simplified models are caused by heterogeneous cartilage surface curvature and thickness. Simplified and 3D FE analysis confirmed our hypothesis that greater cartilage thickness mismatches resulted in higher cartilage stresses for sunken subchondral bone. Unexpectedly, cartilage stresses were independent of the cartilage thickness mismatch for proud subchondral bone. These FE findings did not account for tissue remodeling, patient variability in tissue mechanical properties, or complex tissue loading. In vivo experiments with full-thickness strain measurements should be conducted to confirm these findings. Mismatches in the subchondral bone can therefore produce stress increases large enough to cause local chondrocyte death near the subchondral surface. These stress increases can be reduced by (a) reducing the difference in thickness between graft and native cartilage or (b) using a graft with cartilage that is thinner than the native cartilage. For any figures or tables, please contact the authors directly

This study investigated confocal laser scanning microscopy (CLSM) as a novel method of imaging of chondrocytes on a collagen membrane used for articular cartilage repair. Cell viability and the effects of surgery on the cells were assessed. Cell images were acquired under four conditions: 1, Pre-operative 2, After handling 3, Heavily grasped with forceps 4, Cut around the edge. Live and dead cell stains were used. Images were obtained for cell counting and morphology. Mean cell density was 1.12–1.68 ± 0.22 × 10. 6. cells/cm. 2. in specimens without significant trauma (n=25 images), this decreased to 0.253 × 10. 6. cells/cm. 2. in the specimens that had been grasped with forceps (p <0.001) (5 images). Cell viability on delivery grade membrane was 86.8±2.1%. The viability dropped to 76.3 ± 1.6% after handling and 35.1 ± 1.7% after crushing with forceps. Where the membrane was cut with scissors, there was a band of cell death where the viability dropped to 17.3 ± 2.0% compared to 73.4 ± 1.9% in the adjacent area (p <0.001). Higher magnification revealed cells did not have the rounded appearance of chondrocytes. CLSM can quantify and image the fine morphology of cells on a MACI membrane. Careful handling of the membrane is essential to minimise chondrocyte death during surgery

Background. Continuous post-operative infusion of local anaesthetic solutions has been implicated as the causative factor in many cases of chondrolysis. Recent in-vitro studies have shown that even a single exposure to local anaesthetic can cause apoptosis and mitochondrial dysfunction leading to chondrocyte death. Glucosamine has been shown to have a protective and reparative effect on articular cartilage. Aims. To compare the effect of a single exposure of different local anaesthetic solutions on human articular cartilage and to investigate the protective and reparative effects of Glucosamine on articular cartilage exposed to 0.5% Bupivacaine. Methods. Chondral explants (n=354) were obtained from femoral heads of hip fracture patients undergoing hemiarthroplasty. Each specimen was exposed to one of 8 test solutions for one hour. The specimens were then incubated in culture medium containing radio-labelled 35-sulphur for 16 hours. The uptake of 35-S by each specimen was measured to give an estimate of proteoglycan metabolism. Test solutions. 1. 1% Lidocaine 2. 2% Lidocaine 3. 0.25% Bupivacaine, 4. 0.5% Bupivacaine, 5. 0.5% Levo-Bupivacaine 6. Control solution of M199 culture medium. 7. To investigate its protective effect, 100 micrograms of Glucosamine was added along with 0.5% Bupivacaine 8. To investigate its reparative effect, Glucosamine was added after exposure to Bupivacaine for an hour. Results. Compared to the control solution, the inhibition of proteoglycan metabolism was 64% with 1% Lidocaine(p< 0.001), 79% with 2% Lidocaine(p< 0.001), 61% with 0.25% Bupivacaine(p< 0.001), 85% with 0.5% Bupivacaine(p< 0.001) and 77% with 0.5% Levo-Bupivacaine(p< 0.001). Adding Glucosamine reduced Bupivacaine toxicity to 43%(p< 0.001). Glucosamine marginally repaired the damage caused by Bupivacaine, with inhibition of proteoglycan metabolism at 70%(p=0.004). Conclusion. All local anaesthetic solutions were toxic to articular cartilage. The addition of Glucosamine to 0.5% Bupivacaine protected against its toxicity to articular cartilage

Introduction:. Unicompartmental knee arthroplasty (UKA) has been used in the past decades to treat progressive cartilage degeneration in a single compartment. Concern has been raised over the rate of revision procedures for polyethylene wear and osteoarthritic progression into the adjacent compartment. Few studies have examined the pathology of cartilage degeneration in the setting of UKA. This study aims to investigate the viability of knee chondrocytes introduced to high and low concentrations of orthopaedic wear debris particulate. Methods:. Normal human articular chondrocytes (nHAC-Kn) were expanded in DMEM/F12 containing 10% FBS, 1% Penicillin/Streptomycin (Pen/Strp), and 50 μg/mL ascorbic acid (Asc). 24 hours prior to the start of the experiment, cells were seeded on 96-well plates at a density of 3500 cells/cm. 2. and exposed to DMEM/F12 containing 5% FBS, 1% Pen/Strp, and 50 μg/mL Asc. Particles (equivalent circle diameter range: 0.2–7 μm) at a low dose of 100: 1 (particles: cells) and high dose 1000: 1 (particles: cells) were introduced to treatment wells (n = 6). Control wells (n = 6) contained particles with no cells. Treatment groups included high and low doses of TiAl. 6. V. 4. alloy, 316L Stainless Steel, and Co-Cr-Mo alloy. At days 1, 3, 5, and 7, cells were assayed with a 3-(4,5-Dimethylthiazol-2-yl)-2,5-dyphenyltetrazolium bromide (MTT) assay for determination of cell viability. Light microscopy was performed at each timepoint to assess change in cell morphology. Results:. All groups displayed a minor decrease in cell viability after 24 hours of exposure to particles. Similarly, a second distinct decrease in viability occurred at the day 3 timepoint. Days 5 and 7 yielded little change in cell viability. Results are displayed in Figure 1. Observations of light microscopy revealed cells may actively engulf particles over time. Images show particle concentrations at the same locations as chondrocytes with few particles present between cells. Conclusions:. Wear debris has been implicated as a contributing source to osteolysis and component loosening. A potential effect on the cellular level can ultimate lead to effects on the entire tissue and complications on the clinical level. A decrease in chondrocyte viability has been shown in response to the presence of particulate wear debris. Our results showed decreases in cell viability were most noticeable between 24 and 72 hours after introduction to particles. Chondrocyte death may contribute to progression of cartilage degeneration into healthy compartments of the knee. Continued experiments are underway further characterizing chondrocyte response to wear debris particulate with respect to protein and gene expression in an extended 7 day in vitro culture

Hyaline articular cartilage has been known to be a troublesome tissue to repair once damaged. Since the introduction of autologous chondrocyte implantation (ACI) in 1994, a renewed interest in the field of cartilage repair with new repair techniques and the hope for products that are regenerative have blossomed. This article reviews the basic science structure and function of articular cartilage, and techniques that are presently available to effect repair and their expected outcomes.