Hydroxyapatite-coated femoral stems. Histology and histomorphometry around five components retrieved at post mortem.
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We performed a histological and histomorphometric examination in five cadaver specimens of the femoral and acetabular components and the associated tissue which had been recovered between 3.3 and 6.2 years after primary total hip arthroplasty (THA) using a proximal hydroxyapatite (HA)-coated titanium alloy implant. All had functioned well during the patients' life. All the stems were fixed in the femur and showed osseointegration of both the proximal and distal parts. The amount of residual HA was greatest in the distal metaphyseal sections, indicating that the rate of bone remodelling may be the main factor causing loss of HA. The level of activity of the patient was the only clinical factor which correlated with loss of coating. The percentage of bone-implant osseointegration was almost constant, regardless of the amount of HA residue, periprosthetic bone density or the time of implantation. HA debris was seldom observed and if present did not cause any adverse or inflammatory reaction. Partial debonding did occur in one case as a result of a polyethylene-induced inflammatory reaction. (+info)
Coating titanium implants with bioglass and with hydroxyapatite. A comparative study in sheep.
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This study compares the osteointegration of titanium implants coated with bioglass (Biovetro GSB formula) and with hydroxyapatite (HAP). Twenty-four bioglass-coated and 24 HAP-coated cylinders were implanted in the femoral diaphyses of sheep, and examined after 2, 4, 6, 8, 12, and 16 weeks. The HAP coating gave a stronger and earlier fixation to the bone than did bioglass. Bioglass formed a tissue interface which showed a macrophage reaction with little new bone formation activity. In contrast, HPA, showed intense new bone formation, with highly mineralised osseous trabeculae in the neighbourhood of the interface. (+info)
The potent platelet inhibitory effects of S-nitrosated albumin coating of artificial surfaces.
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OBJECTIVES: We studied the antithrombotic effect of coating glass, collagen and metal stent surfaces with bovine serum albumin (BSA) covalently modified to carry S-NO functional groups denoted (pS-NO-BSA). METHODS: Video-enhanced light microscopy was used to visualize canine blood platelet adhesion and aggregation in a parallel plate glass chamber. Platelet adhesion was observed for 60 min on glass, glass coated with BSA, glass coated with pS-NO-BSA, collagen I (CO) surface, CO coated with BSA and CO coated with pS-NO-BSA. We also coated Palmaz-Shatz (P-S) stents with pS-NO-BSA. Coated and uncoated stents were then immersed in porcine platelet-rich plasma for two min and the platelet cyclic GMP level was measured. In six anesthetized pigs, coated and uncoated stents were placed in the carotid arteries and [111In]-labeled platelets were circulated for 2 h. The stented arteries were then removed and placed in a gamma well counter. RESULTS: There was significantly less platelet attachment, adhesion and aggregation on the pS-NO-BSA coated surfaces compared with the BSA coated and uncoated surfaces. The pS-NO-BSA coating increased the platelet cGMP levels to 5.9+/-0.7 pmoles/10(8) platelets compared with 2.7+/-0.9 pmoles/10(8) platelets for control (p < 0.01). The average gamma ray count from [111In]-labeled platelets that attached to the coated stents was 90,000+/-42,000/min and 435,000+/-290,000/min for the uncoated stents (p < 0.01). CONCLUSIONS: The pS-NO-BSA coating of thrombogenic surfaces reduces platelet adhesion and aggregation, possibly by increasing the platelet cGMP. This inhibitory effect appears to be a consequence of the direct antiplatelet actions of NO combined with the antiadhesive properties of albumin. (+info)
A comparative study of the rifampicin binding and elution characteristics for collagen- and albumin-sealed vascular grafts.
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OBJECTIVES: To assess the rifampicin binding and elution characteristics for three protein-sealed vascular grafts. DESIGN: In vitro study. MATERIALS: Cardial and Hemashield collagen-sealed and the DeBakey/Vasculour albumin-sealed vascular grafts. METHODS: The grafts were soaked in a 60,000 mg/l solution of rifampicin at 37 degrees C for 15 min. Bound drug was eluted from the grafts at 37 degrees C and at timed intervals the concentrations of rifampicin remaining in the grafts were determined. RESULTS: Although all three grafts contained high concentrations of rifampicin immediately after soaking these rapidly fell on washing and only a small fraction of the adsorbed rifampicin was tightly bound to the grafts. Rifampicin loading of this tightly bound fraction was similar for the two collagen-sealed grafts (1.7-2.0 mg/kg) but higher for the albumin-sealed graft (16.0 mg/kg). Elution of the tightly bound fraction appeared to follow first-order kinetics with elimination half-lives of 89-141 h. The concentrations of rifampicin remaining in the grafts after eight days were above those needed to inhibit sensitive staphylococci and were 0.7 mg/kg (collagen-sealed grafts) to 3.7 mg/kg (albumin-sealed graft). CONCLUSIONS: There is broad equivalence between the rifampicin binding and elution for the two collagen-sealed grafts, but there appears to be slightly higher binding for the albumin-sealed graft. (+info)
Radiologic and histopathologic evaluation of canine artery occlusion after collagen-coated platinum microcoil delivery.
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BACKGROUND AND PURPOSE: Platinum coil embolization is one of the significant advances in interventional neuroradiologic techniques that has been introduced this decade. Our purpose was to evaluate the angiographic and histologic effects of collagen-coated platinum microcoil delivery in the canine artery. METHODS: We embolized the bilateral internal maxillary arteries of 18 dogs; one uncoated and one collagen-primed coil was used in each dog. We evaluated all coils by angiography, macroscopy, and scanning electron microscopy within 30 minutes of embolization. We then studied a proportional number of coated and collagen-primed coils at either 1 or 3 days, or 1, 2, 3, 4, 8, 12, or 16 weeks postoperatively. RESULTS: Six (33%) of 18 arteries embolized with uncoated coils were occluded 30 minutes after delivery, whereas 11 (61%) of 18 arteries treated with collagen-primed coils were occluded within 30 minutes of embolization. Late occlusion (3 weeks after embolization) occurred in 2 (25%) of 8 arteries embolized with untreated coils, and 6 (75%) of 8 arteries embolized with collagen-primed coils. We calculated differences in late occlusion rates by the chi2 (chi-square) test, and found these differences were significant (P=.04). Histologic findings of arteries embolized with unprimed coils revealed endothelial cell growth was limited to the organized thrombi 4 weeks after coil delivery. In contrast, endothelial cells grew directly on the collagen-primed coils 3 days postoperatively, and coils were completely covered by endothelial cells within 2 weeks. We found an organized thrombus in the inner space of coils in angiographically occluded arteries, a finding that was not evident in angiographically patent arteries. CONCLUSION: Collagen-coated platinum coils can produce rapid and stable occlusion of embolized vessels. (+info)
Coating of extracorporeal circuit with heparin does not prevent sequestration of propofol in vitro.
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Propofol is sequestered in extracorporeal circuits, but the factors responsible for the phenomenon are mostly unknown. We have compared two extracorporeal circuits (oxygenators, reservoirs and tubings) coated with heparin with two corresponding uncoated circuits for their capacity to sequester propofol in vitro. Three experiments were conducted with each circuit. The circuit was primed with a mixture of Ringer's acetate solution and whole blood, and the study conditions (pump flow, temperature, pH) were standardized. Propofol was added to the solution to achieve a concentration of 2 micrograms ml-1. These studies were followed with concentrations of 10- and 100-fold to assess possible saturation of propofol binding. Serial samples were obtained from the circulating solution for measurement of propofol concentration. Propofol concentrations decreased to 22-32% of the initial predicted concentration of 2 micrograms ml-1 in the circuits (no significant difference between circuits). With greater concentrations, the circuits did not become saturated with propofol, even with the highest predicted concentration of 200 micrograms ml-1. We conclude that propofol was sequestered in extracorporeal circuits in vitro, irrespective of coating the circuit with heparin. (+info)
An ex vivo investigation into the bond strength of orthodontic brackets and adhesive systems.
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The aim of this study was to compare the shear bond strength of Adhesive Precoated Brackets (APC) with that of two types of uncoated bracket bases, Straight-Wire and Dyna-Lock. Two types of orthodontic adhesives were used, Transbond XT and Right-On. Three different curing times were evaluated with the APC brackets in order to find the best. Adhesive remnants on the enamel surface following debond were evaluated using the Adhesive Remnant Index (Artun and Bergland, 1984). Bond strengths ranged from 11.00 to 22.08 MPa. For both types of brackets Transbond produced a significant increase in bond strength compared to Right-On. The Dyna-Lock/Right-On combination produced the poorest results. APC brackets cured for 40 s had similar bond strengths to uncoated brackets fixed by means of Transbond. Overall, 79 per cent of specimens had less than half the tooth surface covered with adhesive following debond. Significantly more adhesive remained on tooth surfaces following debond of the Straight-Wire/Right-On group than any other bracket/adhesive combination. Bond strengths were higher with light-cured Transbond than with chemically-cured Right-On. When Transbond is used in association with APC brackets a 40-second cure time is recommended. (+info)
Polyethylene wear, osteolysis and acetabular loosening with an HA-coated hip prosthesis. A follow-up of 94 consecutive arthroplasties.
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We have followed up for a period of seven to nine years 100 consecutive arthroplasties of the hip in which an entirely HA-coated implant had been used. The clinical results were excellent and bony incorporation was extensive in all components. No stem became loose or subsided but five cups were revised because of loosening after 3.8 to 5.5 years, having functioned painlessly and shown radiological ingrowth. Revision procedures because of excessive polyethylene wear have been performed on 18 hips and are planned for six more. Two eroded metal backings with worn-through polyethylene were exchanged; six hips showed metallosis without polyethylene wear-through. There were two cases of granulomatous cysts in the groin and 66 hips had osteolysis located periarticularly, in the greater trochanter or in the acetabulum. (+info)