Effect of 3D-microstructure of bioabsorbable PGA:TMC scaffolds on the growth of chondrogenic cells.

Various biomaterial scaffolds have been investigated for cartilage tissue engineering, although little attention has been paid to the effect of scaffold microstructure on tissue growth. Non-woven, fibrous, bioabsorbable scaffolds constructed from a copolymer of glycolide and trimethylene carbonate with varying levels of porosity and pore size were seeded with mesenchymal stroma cells with a chondrogenic lineage. Scaffolds and media were evaluated for both cell and extracellular matrix organization and content after up to 28 days of culture in a spinner flask.

Prevention of loosening in total hip replacements using guided bone regeneration.

The aim of this study was to prevent wear debris from reaching the interface of the acetabular cup and femoral component by using a partially occlusive expanded polytetrafluoroethylene membrane. This membrane initially acted as a physical seal, which became incorporated by bone and soft tissue, forming a secondary biologic seal, preventing loosening. An animal model was developed to test the hypothesis.

Joint resurfacing using allograft chondrocytes and synthetic biodegradable polymer scaffolds.

Cartilage implants which could potentially be used to resurface damaged joints were created using rabbit articular chondrocytes and synthetic, biodegradable polymer scaffolds. Cells were serially passaged and then cultured in vitro on fibrous polyglycolic acid (PGA) scaffolds. Cell-PGA constructs were implanted in vivo as allografts to repair 3-mm diameter, full thickness defects in the knee joints of adult rabbits, and cartilage repair was assessed histologically over 6 months.

Bone remodeling and in vivo strain analysis of intact and implanted greyhound proximal femora.

Pre- and poststudy motion and gait analyses of eight size-matched male greyhounds confirmed uniform loading of their femora. Subminiature strain gages implanted on the intact inferior and anterior aspects of the femoral neck in six greyhounds indicated in vivo strain variations among test animals. Motion and gait analyses confirmed uniform loading of femora following unilateral hemiarthroplasty with cobalt-chromium hip implants.

Composition of cell-polymer cartilage implants.

Cartilage implants for potential in vivo use for joint repair or reconstructive surgery can be created in vitro by growing chondrocytes on biodegradable polymer scaffolds. Implants 1 cm in diameter by 0.176 cm thick were made using isolated calf chondrocytes and polyglucolic acid (PGA).

Cement particles inhibit bone growth into titanium chambers implanted in the rabbit.

Particles of bone cement have been shown previously to stimulate the resorption of bone. The purpose of this study was to determine whether particles of bone cement (BC) have an adverse effect on bone ingrowth. The bone harvest chamber was implanted bilaterally in the proximal tibial metaphysis of 6 mature rabbits.

Hydroxyapatite-coated strain gauges for long-term in vivo bone strain measurements.

The aim of this study was to examine the bonding process between hydroxyapatite-coated strain gauges and bone in order to continue development of a long term in vivo strain measurement device. Two types of commercially available hydroxyapatite (HA) particles were applied to the sensing surface of uniaxial strain gauges using a polysulfone solution as an adhesive. Characterization by scanning electron microscopy and x-ray diffraction (XRD) was used to determine materials property differences between the two powders.

Neocartilage formation in vitro and in vivo using cells cultured on synthetic biodegradable polymers.

Cartilaginous implants for potential use in reconstructive or orthopedic surgery were created using chondrocytes grown on synthetic, biodegradable polymer scaffolds. Chondrocytes isolated from bovine or human articular or costal cartilage were cultured on fibrous polyglycolic acid (PGA) and porous poly(L)lactic acid (PLLA) and used in parallel in vitro and in vivo studies. Samples were taken at timed intervals for assessment of cell number and cartilage matrix (sulfated glycosaminoglycan [S-GAG], collagen).

Performance of a hydrogel composite pericardial substitute after long-term implant studies.

A novel composite patch has been tested as a pericardial substitute to reduce adhesion formation after cardiac surgery. The patch consists of poly 2-hydroxyethyl methacrylate (pHEMA) hydrogel reinforced with a polyethylene terephthalate (PET) mesh. The hydrogel-PET composite pericardial patches were implanted in canines for 6, 9, and 12 months.

Triple fluorochrome labeling of cochlear bone growth.

A new technique is described which measures the extent and time course of intracochlear bone formation after cochlear implantation in an experimental animal model. A series of fluorescent histochemical markers is used to delineate the amount of intracochlear bone deposition during specified time periods.

Iron overload in Africa. Interaction between a gene and dietary iron content.

Background And Methods: In contrast to hemochromatosis, which in white populations is inherited through a gene linked to the HLA locus, iron overload in sub-Saharan Africa is believed to result solely from increased dietary iron derived from traditional home-brewed beer. To examine the hypothesis that African iron overload also involves a genetic factor, we used likelihood analysis to test for an interaction between a gene (the hypothesized iron-loading locus) and an environmental factor (increased dietary iron) that determines transferrin saturation and unsaturated iron-binding capacity. We studied 236 members of 36 African families chosen because they contained index subjects with iron overload.

Histologic, biochemical, and ion analysis of tissue and fluids retrieved during total hip arthroplasty.

Large amounts of metal and polyethylene debris and high ion readings are found in capsule and fibrous membranes of both loose titanium and cobalt-chromium stems. Prostaglandin E2, interleukin-1, and collagenase levels are elevated when compared to control values with collagenase having the highest and most consistent elevations. Synovial fluid and blood ion readings were elevated in loose cemented and cementless stems made from both materials.

Preliminary development of a hydroxyapatite-backed strain gauge.

Long-term in vivo strain sensing would provide information about deformation changes adjacent to implants during bone remodeling. Biodegradation of the cyanoacrylate adhesive commonly used to attach strain gauges to bone has generally limited in vivo strain sensing to time periods less than one month. Hydroxyapatite (HA) which has been used to attach implants to bone in vivo, was attached to strain gauges using a solvent-thinned polysulfone solution.

Alteration of retrieved implants in vitro by processing and infiltrating fluids.

Undecalcified histology has proved of immense value in the examination of the interface membrane between the prosthesis and bone. However, to provide such histological sections, dehydrating and clearing fluids as well as plastic infiltrating fluids must be used. This study investigates the possibility that some of these commonly used fluids may alter the biomaterial after removal from the body and be misinterpreted as an in vivo product.

Histological analysis of a central tarsal implant in a racing greyhound.

The hock of a greyhound containing a titanium alloy central tarsal replacement was examined histologically. The animal had raced competitively 43 times before retirement. The examination showed that the adaptation and encapsulation of the implant by the surrounding bones, together with the excellent purchase of the screw into the fourth tarsal bone, had maintained the implant in excellent position during vigorous load-bearing.

Life stress and lymphocyte alterations among patients with rheumatoid arthritis.

The relation between life stress and immune parameters was investigated for 33 female rheumatoid arthritis (RA) patients interviewed during three routine monthly clinic checkups. Life stress from major and minor events, coping efficacy, and self-reported psychological distress were assessed, and immunofluorescence of T-cells and B-cells was performed on the blood drawn during each visit. Small stressful events were positively related to the proportion of circulating B-cells, psychological distress was inversely related to proportion of circulating T-cells, and major life events were associated with lower T-helper/T-suppressor cell ratios.

Kaposi's sarcoma in Zimbabwe. II. Peripheral lymphocytes, immunoglobulin G levels and HIV antibody positivity.

Patients with Kaposi's Sarcoma (KS) were grouped according to their clinical symptoms into "indolent", "locally aggressive", "endemic generalised aggressive" and "epidemic generalised aggressive" disease. Only the patients in the epidemic generalised aggressive disease group had serum antibodies to HIV. Complete peripheral blood counts, including lymphocyte subsets, and serum IgG assays were performed on all patients before treatment was initiated.

A polymethyl methacrylate method for large specimens of mineralized bone with implants.

A simple modified polymethyl methacrylate method is described for large mineralized bone specimens with implants and bioactive materials which produces consistently good histological preservation of the interface between bone and implant. Human femoral heads, whole rabbit condyles and canine tibias and femurs containing implants consisting of hydroxyapatite, smooth polyethylene, porous polyethylene and carbon were dehydrated in ascending grades of ethanol and cleared with xylene on an automated tissue processor which alternated vacuum and pressure for 22 hr. Infiltration was done with washed polymethyl methacrylate at 4 C under vacuum for 13 days.