Growth inhibition of cultured smooth muscle cells by corrosion products of 316 L stainless steel wire.

The potential cytotoxicity on vascular smooth muscle cells of corrosion products from 316 L stainless steel, one of most popular biomaterials of intravascular stents, has not been highlighted. In this investigation, 316 L stainless steel wires were corroded in Dulbecco's modified eagle's medium with applied constant electrochemical breakdown voltage, and the supernatant and precipitates of corrosion products were prepared as culture media. The effects of different concentrations of corrosion products on the growth of rat aortic smooth muscle cells were conducted with the [3H]-thymidine uptake test and cell cycle sorter. Both the supernatant and precipitates of corrosion products were toxic to the primary culture of smooth muscle cells. The growth inhibition was correlated well with the increased nickel ions in the corrosion products when nickel concentration was above 11.7 ppm. The corrosion products also changed cell morphology and induced cell necrosis. The cell growth inhibition occurred at the G0/G1 to S transition phase. Similar to our recent study of nitinol stent wire, the present investigation also demonstrated the cytotoxicity of corrosion products of 316 L stainless steel stent wire on smooth muscle cells, which might affect the poststenting vascular response.

Biomechanical evaluation of anterior cervical spine stabilization.

STUDY DESIGN: An in vitro biomechanical study. OBJECTIVES: To simulate a severe compressive flexion injury for determination of the relative stability of different anterior instrumentation systems in a porcine model and to validate this model in human cadaveric specimens. SUMMARY OF BACKGROUND DATA: Anterior plate fixation is useful for high-grade mechanical insufficiency of the cervical spine and may prevent the need for a second procedure. METHODS: The cervical spines of 45 porcine and 12 cadaveric specimens were subjected to nondestructive flexion, lateral bending, and torsional testing on a modified universal testing machine. A corpectomy was performed with release of the posterior ligamentous structures. The specimens were stabilized with one of three anterior plate constructs. The nondestructive testing was repeated to evaluate structural stability (stiffness and neutral zone). Finally, destructive testing examined failure moment, energy to failure, and mechanism of failure. RESULTS: The instrumented specimens had flexural and lateral bending and torsional stiffness values that were similar to or greater than those of their paired intact specimens. The cervical spine locking plate had a significantly higher flexural stiffness ratio (plated:intact), torsional stiffness ratio, lower flexural neutral zone ratio, higher failure moment, and higher energy to failure than did the Caspar plate. CONCLUSIONS: The cervical spine locking plate is theoretically safer than the Caspar system because the posterior vertebral body cortex is not breached by the fixation screws, and the screws are less likely to back out anteriorly and irritate the esophagus. According to these results, the cervical spine locking plate system is biomechanically equivalent to and in some cases more stable than the Caspar system for fixation of a severe compressive flexion injury.

Crosslinking characteristics of porcine tendons: effects of fixation with glutaraldehyde or epoxy.

Anterior cruciate ligament (ACL) injuries, if left untreated, often produce significant disability in the athletically active population. Currently, autogenous tissue is the most commonly used substitute for ACL reconstruction because its immunogenicity is virtually nonexistent. However, the functional amount of autogenous tissue available for transplantation is limited. Additionally, this transplantation procedure may create a defect at the donor site, which can result in functional disability. To address these concerns, a prototype xenograft ligament prosthesis, epoxy-fixed porcine Achilles tendon, was developed. This study was intended to investigate the crosslinking characteristics of the epoxy-fixed porcine tendon. The fresh and glutaraldehyde-fixed porcine Achilles tendons were used as controls. Fresh porcine Achilles tendons procured from a slaughterhouse were used to fabricate the ligament prostheses. A 4% epoxy (ethylene glycol diglycidyl ether) solution or a 0.625% glutaraldehyde solution was employed to fix the porcine tendons. Samples of each group were taken out at various elapsed fixation periods. The crosslinking characteristics- denaturation temperature, moisture content, and fixation index-of each sample were then determined. In the study, it was learned that the crosslinking rate for the glutaraldehyde fixation was faster than that for the epoxy fixation. While the denaturation temperatures and the fixation indices for both studied groups were higher than for the fresh one, the denaturation temperature of the glutaraldehyde-fixed tendon was relatively higher than its epoxy-fixed counterpart. However, the fixation index and the moisture content for both studied groups were comparable. Also, it was noted that the epoxy-fixed tendon appeared more natural as compared to its glutaraldehyde-fixed counterpart. The implications of these findings for the epoxy-fixed tendon in the clinical ACL reconstruction require further investigation.

Biological materials fixed with an epoxy compound: comparison of the effects with or without ionically bound heparin.

Biological materials have been used as prosthetic devices such as heart valves, vascular grafts, and pericardial patches. These biological materials have to be fixed with crosslinking reagents and sterilized subsequently before they can be implanted in humans. Recently, a new crosslinking reagent, epoxy compound, has been used to fix bioprostheses. In this fixation technique, heparin may be ionically bound on the tissue surface. It has been shown that the amount of heparin bound to the tissue surface is proportional to the quantity of protamine impregnated in the biological tissues. However, it is not known if the impregnation of protamine will affect the crosslinking density of the biological tissues. This study was designed to compare the crosslinking densities of the epoxy compound fixed biological tissues with or without heparinization. Fresh porcine aortic valves procured from a slaughter house were first impregnated in various concentrations of protamine sulfate (0, 0.5, 1.0, or 1.5%) for about 30 min. The porcine aortic valves were then crosslinked in a 4% epoxy compound solution (Denacol EX-313). The porcine samples were taken out at various elapsed fixation periods: 18, 25, 48, 72, 96, and 120 h. Finally, the crosslinked porcine aortic valves were heparinized in a 0.5% sodium heparin solution for about 1 h. The crosslinking densities of the porcine leaflet and the aortic wall of each sample were determined by measuring their shrinkage temperatures. It was revealed that the impregnation of various concentrations of protamine did not seem to significantly alter the shrinkage temperatures of the porcine leaflet and the aortic wall throughout the entire fixation process (p > 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Interim follow-up studies of innominate osteotomy for congenital dislocation of the hip.

Innominate osteotomy alone without any adjunctive procedures was performed for congenital dislocation of the hip in 30 children. A complete follow-up study of an average of four years and nine months was obtained for 20 hips in patients. These interim results were quite gratifying. Clinical and radiologic assessments by a score system of Trevor and associates revealed that 85% of the hips that had been operated upon were functionally satisfactory. There were three cases of redislocation which were classified as resulting from technical failures.

A case of malignant lymphoma, undifferentiated, Burkitt's type with high antibodies to Epstein-Barr virus.

A 5-year-4-month-old girl was admitted to Taipei Municipal Jen-Ai Hospital because of a rapidly enlarging right submandibular tumor. The diagnosis of malignant lymphoma, undifferentiated, Burkitt's type was made by distinctive histopathological features. Positive serological findings related to Epstein-Barr virus infection were disclosed. Complete remission has been achieved since the treatment with high-dose cyclophosphamide was given, and no signs of relapse have been found yet.

Tibial lengthening: a preliminary report.

A preliminary review of 9 tibial lengthenings has been made to assess the value of a modification of the Anderson operation. The procedure can be carried out in one stage and is applicable to the older child and young adult. This is important as it may be used in the late or neglected case where epiphyseal arrest has failed or was never done. Five out of 9 patients in this series were skeletally mature. Leg lengthening procedures will always entail certain hazards. Complications occurred in 7 of the 9 patients, but were recognized early and expeditiously managed, and in several instances resulted in only minor deformity. The satisfactory end results in this series are attributable to the principle of limiting tibial lengthening to no more than 10 per cent of the overall bone length, i.e. 5 cm or less. No neurovascular complications occurred. Although tibial lengthening is hazardous and can cause severe disability, the results reported here suggest that in selected cases, it is a valuable procedure for correction of leg length discrepancy.