An antioxidant stabilized, chemically cross-linked UHMWPE with superior toughness.

Chemical cross-linking of ultrahigh molecular weight polyethylene (UHMWPE) using an organic peroxide followed by high temperature melting results in a large increase in toughness accompanied by a decrease in cross-link density, which, surprisingly does not compromise the wear resistance. We compared the mechanical properties and wear behavior of a vitamin E blended, chemically cross-linked and high temperature melted UHMWPE produced by ram extrusion (PRX HTM) to those measured with the clinically available 100-kGy irradiated and melted UHMWPE (CISM 100). We also assessed the local biocompatibility of PRX-HTM in rabbit subcutaneous pouch and osteochondral defect models.

Residual Byproducts of Peroxide Crosslinked Vitamin E-Blended Ultrahigh Molecular Weight Polyethylene.

Background: Wear resistance of ultrahigh molecular weight polyethylene (UHMWPE) is improved via ionizing radiation crosslinking and subsequent high temperature melting for improved toughness. Our group has previously reported that crosslinking can also be achieved chemically using organic peroxides. However, volatile peroxide byproducts are generated during consolidation.

Effects of vitamin E-diffused highly cross-linked UHMWPE particles on inflammation, apoptosis and immune response against S. aureus.

Particle-induced osteolysis and periprosthetic joint infection (PJI) are closely associated with periprosthetic tissue immune function. The objective of this study was to determine the effects of polyethylene particles on inflammation and response against S. aureus.

Chondrogenesis by bone marrow-derived mesenchymal stem cells grown in chondrocyte-conditioned medium for auricular reconstruction.

Bone marrow-derived mesenchymal stem cells (BMSCs) can be obtained by minimally invasive means and would be a favourable source for cell-based cartilage regeneration. However, controlling the differentiation of the BMSCs towards the desired chondrogenic pathway has been a challenge hampering their application. The major aim of the present study was to determine if conditioned medium collected from cultured auricular chondrocytes could promote chondrogenic differentiation of BMSCs.

Articular cartilage generation applying PEG-LA-DM/PEGDM copolymer hydrogels.

Background: Injuries to the human native cartilage tissue are particularly problematic because cartilage has little to no ability to heal or regenerate itself. Employing a tissue engineering strategy that combines suitable cell sources and biomimetic hydrogels could be a promising alternative to achieve cartilage regeneration. However, the weak mechanical properties may be the major drawback to use fully degradable hydrogels.

Ear-Shaped Stable Auricular Cartilage Engineered from Extensively Expanded Chondrocytes in an Immunocompetent Experimental Animal Model.

Advancement of engineered ear in clinical practice is limited by several challenges. The complex, largely unsupported, three-dimensional auricular neocartilage structure is difficult to maintain. Neocartilage formation is challenging in an immunocompetent host due to active inflammatory and immunological responses.

Biological reaction to polyethylene particles in a murine calvarial model is highly influenced by age.

Particle-induced osteolysis is driven by multiple factors including bone metabolism, inflammation, and age. The objective of this study was to determine the influence of age on polyethylene (PE) particle-induced osteolysis in a murine calvarial model comparing 2-month-old (young) versus 24-month-old (old) mice. After PE particle implantation, calvaria were assessed at days (D) 3, D7, D14, and D21 via chemoluminescent imaging for inflammation (L-012 probe).

Conditions for seeding and promoting neo-auricular cartilage formation in a fibrous collagen scaffold.

Background: Carved autologous costal cartilage and porous polyethylene implants (Medpor) are the most common approaches for total ear reconstruction, but these approaches may have inconsistent cosmetic outcomes, a high risk of extrusion, or other surgical complications. Engineering ear cartilage to emulate native auricular tissue is an appealing approach, but often the cell-seeded scaffolds are susceptible to shrinkage and architectural changes when placed in vivo. The aim of this study was to assess the most favorable conditions for in vitro pre-culture of cell-seeded type I collagen scaffolds prior to in vivo implantation.

Osteochondral defect repair using a polyvinyl alcohol-polyacrylic acid (PVA-PAAc) hydrogel.

Poly(vinyl alcohol) (PVA) hydrogels can be candidates for articular cartilage repair due to their high water content. We synthesized a PVA-poly(acrylic acid) (PAAc) hydrogel formulation and determined its ability to function as a treatment option for condylar osteochondral (OC) defects in a New Zealand white rabbit (NZWR) model for 12 weeks and 24 weeks. In addition to hydrogel OC implants, tensile bar-shaped hydrogels were also implanted subcutaneously to evaluate changes in mechanical properties as a function of in vivo duration.

Vitamin E-diffused highly cross-linked UHMWPE particles induce less osteolysis compared to highly cross-linked virgin UHMWPE particles in vivo.

Recent in vitro findings suggest that UHMWPE wear particles containing vitamin E (VE) may have reduced biologic activity and decreased osteolytic potential. We hypothesized that particles from VE-stabilized, radiation cross-linked UHMWPE would cause less osteolysis in a murine calvarial bone model when compared to virgin gamma irradiated cross-linked UHMWPE. Groups received equal amount of particulate debris overlaying the calvarium for 10 days.

Ovine model for auricular reconstruction: porous polyethylene implants.

Objectives: We developed a large animal model for auricular reconstruction with engineered cartilage frameworks and evaluated the performance of porous polyethylene auricular implants in this model.

Methods: Eighteen high-density porous polyethylene auricular frameworks were implanted subcutaneously in the infra-auricular areas of 9 sheep. The implants were harvested 17 weeks later for gross and histologic examination.

Successful creation of tissue-engineered autologous auricular cartilage in an immunocompetent large animal model.

Tissue-engineered cartilage has historically been an attractive alternative treatment option for auricular reconstruction. However, the ability to reliably generate autologous auricular neocartilage in an immunocompetent preclinical model should first be established. The objectives of this study were to demonstrate engineered autologous auricular cartilage in the immunologically aggressive subcutaneous environment of an immunocompetent animal model, and to determine the impact of in vitro culture duration of chondrocyte-seeded constructs on the quality of neocartilage maturation in vivo.

Sesamoidectomy for hallux sesamoid fractures.

Background: Hallux sesamoid fractures are challenging to treat. Symptomatic nonunion is a common problem after nonoperative treatment. Surgical fixation of the fracture can result in successful union, but is technically challenging and can be associated with prolonged return to activities (RTA).

Properties of cartilage engineered from elderly human chondrocytes for articular surface repair.

Numerous studies on engineering cartilage utilizing chondrocytes from juvenile animal sources have been reported. However, there are many unknown aspects of engineering cartilage using human chondrocytes-especially from middle-aged or elderly adults-which are critical for clinical application of tissue engineering in the field of orthopedic surgery. The primary aim of this study was to engineer neocartilage tissue from 50-60-year-old human chondrocytes in comparison to engineered cartilage made from juvenile swine chondrocytes (JSCs).

The tissue-engineered auricle: past, present, and future.

The reconstruction, repair, and regeneration of the external auricular framework continue to be one of the greatest challenges in the field of tissue engineering. To replace like with like, we should emulate the native structure and composition of auricular cartilage by combining a suitable chondrogenic cell source with an appropriate scaffold under optimal in vitro and in vivo conditions. Due to the fact that a suitable and reliable substitute for auricular cartilage has yet to be engineered, hand-carved autologous costal cartilage grafts and ear-shaped porous polyethylene implants are the current treatment modalities for auricular reconstruction.

Implant-assisted meniscal repair in vivo using a chondrocyte-seeded flexible PLGA scaffold.

A cell-based engineered construct can be used for healing of intractable meniscal lesions. Our aims were to assess the culture conditions (static versus dynamic oscillation) and the healing capacity of the chondrocyte-seeded flexible implants in a heterotopic mouse model. Swine articular chondrocytes were labeled with PKH 26 or DiI dye and seeded onto a flexible PLGA scaffold using dynamic oscillating conditions for 24 h.

Chondrogenic priming adipose-mesenchymal stem cells for cartilage tissue regeneration.

Purpose: Chondrocytes lose their ability to produce cartilaginous matrix during multiplication in culture through repeated passages, resulting in inferior tissue phenotype. To overcome the limited amount of primary chondrocytes, we aimed to determine the optimal culture condition for in vitro/in vivo cartilage regeneration using human adipose-derived mesenchymal stem cells (AMSCs).

Methods: To evaluate the effects exerted by the chondrocytic culture condition on AMSC, we utilized chondrocyte conditioned medium (CM) and/or co-culture methods to prime and differentiate AMSCs.

Engineering ear constructs with a composite scaffold to maintain dimensions.

Engineered cartilage composed of a patient's own cells can become a feasible option for auricular reconstruction. However, distortion and shrinkage of ear-shaped constructs during scaffold degradation and neocartilage maturation in vivo have hindered the field. Scaffolds made of synthetic polymers often generate degradation products that cause an inflammatory reaction and negatively affect neocartilage formation in vivo.

Porous poly(vinyl alcohol)-hydrogel matrix-engineered biosynthetic cartilage.

The objective of this study was to fabricate hydrogel matrix-engineered biosynthetic cartilage using a porous poly(vinyl alcohol) hydrogel (PVA-H) and articular chondrocytes. Chondrocytes were suspended in fibrin gel (FG) or saline carriers and injected into porous PVA-H discs and three-layered constructs (PVA-H between devitalized cartilage). After implantation in nude mice, PVA discs were explanted at 6 weeks and subjected to creep testing for a 20 h period.

Injectable and photopolymerizable tissue-engineered auricular cartilage using poly(ethylene glycol) dimethacrylate copolymer hydrogels.

In this study we investigated the histological, biochemical, and integrative features of the neocartilage using swine auricular chondrocytes photoencapsulated into two poly(ethylene glycol) dimethacrylate (PEGDM) copolymer hydrogels of a different degradation profile: degradable (PEG-4,5LA-DM) and nondegradable (PEGDM) macromers in molar ratios of 60:40 and 70:30. Integration of the engineered tissue with existing native cartilage was examined using an articular cartilaginous ring model. Experimental group samples (total n=96) were implanted subcutaneously into nude mice and harvested at 6, 12, and 18 weeks.

Porous poly(vinyl alcohol)-alginate gel hybrid construct for neocartilage formation using human nasoseptal cells.

Background: Limited options exist for the restoration of craniofacial cartilage. Autologous tissue or porous polyethylene is currently used for nasal and auricular reconstruction. Both options are associated with drawbacks, including donor site morbidity and implant extrusion.

Poloxamer 188 protects against ischemia-reperfusion injury in a murine hind-limb model.

Background: Ischemia-reperfusion injury can activate pathways generating reactive oxygen species, which can injure cells by creating holes in the cell membranes. Copolymer surfactants such as poloxamer 188 are capable of sealing defects in cell membranes. The authors postulated that a single-dose administration of poloxamer 188 would decrease skeletal myocyte injury and mortality following ischemia-reperfusion injury.