Improved mechanical long-term reliability of hip resurfacing prostheses by using silicon nitride.

Although ceramic prostheses have been successfully used in conventional total hip arthroplasty (THA) for many decades, ceramic materials have not yet been applied for hip resurfacing (HR) surgeries. The objective of this study is to investigate the mechanical reliability of silicon nitride as a new ceramic material in HR prostheses. A finite element analysis (FEA) was performed to study the effects of two different designs of prostheses on the stress distribution in the femur-neck area. A metallic (cobalt-chromium-alloy) Birmingham hip resurfacing (BHR) prosthesis and our newly designed ceramic (silicon nitride) HR prosthesis were hereby compared. The stresses induced by physiologically loading the femur bone with an implant were calculated and compared with the corresponding stresses for the healthy, intact femur bone. Here, we found stress distributions in the femur bone with the implanted silicon nitride HR prosthesis which were similar to those of healthy, intact femur bone. The lifetime predictions showed that silicon nitride is indeed mechanically reliable and, thus, is ideal for HR prostheses. Moreover, we conclude that the FEA and corresponded post-processing can help us to evaluate a new ceramic material and a specific new implant design with respect to the mechanical reliability before clinical application.

Deferred urgency carotid artery stenting in symptomatic patients: clinical lessons and biomarker patterns from a prospective registry.

INTRODUCTION: The aim of this prospective observational registry was to study the outcome of symptomatic patients presenting with recent TIA or minor stroke and severe carotid stenosis, submitted to early percutaneous treatment by stenting. A secondary aim was to evaluate the biological activity of the symptomatic carotid plaques by serial serum and urinary markers (PAPP-A, hs-CRP, MMP-2/MMP-9, IL-6/IL-8, TNF alpha, CD40L) measured by enzyme-linked immunosorbent assay before and after treatment. METHODS: From May 2005 to June 2006, 57 patients were enrolled in this prospective registry. All patients underwent carotid stenting using a concentric filter for cerebral protection. The procedure was performed within 24-48hrs of the last attack in patients with TIA (n=24, 42%) and between 14 and 30 days in patients with stroke (n=33, 58%). RESULTS: Successful stent implantation was achieved in all cases (100%). Adverse events at 1 month were 1 death (1.7%) and 2 TIAs (3.5%). Some of the vulnerability markers, in particular those reflecting an active systemic inflammatory process of the plaque (PAPP-A, hs-CR, and IL-6), were significantly elevated at the time of enrolment, increased after stenting and decreased after 30 days. CONCLUSION: Deferred CAS is feasible and safe in selected patients with symptomatic carotid stenosis. This preliminary study in a limited series of patients with unstable carotid plaques revealed that endovascular treatment has a satisfactory outcome considering the very high risk profile of the patient population. The evaluation of some biomarkers suggested an inflammatory role in the process of an unstable carotid plaque generating an acute cerebral event.

Direct coronary stenting versus stenting with balloon pre-dilation: incidence of enzyme release and follow-up results of a multicentre, prospective, randomized study. The CK and Troponin I Estimation in direct STenting (CK TEST) trial.

AIM: The aim of this study was to assess the safety of direct coronary stenting, its influence on costs, duration of the procedure, radiation exposure, clinical outcome and the incidence of periprocedural myocardial damage as assessed by enzyme release determination. METHODS: We randomized 103 patients (109 lesions) to direct stent implant or stent implant following balloon predilatation. Patients with heavily calcified lesions, bifurcations, total occlusions, left main lesions and very tortuous vessels were excluded. Three samples of blood were drawn; before, 12 and 24 h after the procedure and total CK, CK MB mass and troponin I determination was carried out in a single centralized laboratory. RESULTS: Direct stenting was successful in 62/62 lesions (100%). No single loss or embolization of the stent occurred. All stents in the group with predilatation were effectively deployed. The immediate post procedure angiographic results were similar with both techniques. Contrast media consumption and procedural time were significantly lower in direct stenting (150+/-82 cc and 30+/-13 min) than in pre-dilated stenting (184+/-85 cc and 36+/-14 min) (P=0.04 and P=0.036 respectively) while fluoroscopy time was similar (9.1+/-12 vs 9.19+/-15 min, P=0.97). The incidence of enzyme release was similar in the groups with only three non Q MI all in the pre-dilated group (P=0.149). Any elevation of CK MB and troponin I occurred in 7% of direct stent vs 12% of pre-dilated group (P=0.66), isolated troponin I elevation in 21% of both groups. Major adverse cardiac events during hospitalization were 0 in direct and 3 in pre-dilated stenting (P=0.66), but there were no significant differences at follow-up at 1, 6 and 12 months between the 2 groups (target lesion revascularization at 12 months 11 vs 14% in the 2 groups respectively). CONCLUSION: Direct stenting is as safe as pre-dilated stenting in selected coronary lesions. Acute results and myocardial damage as assessed by enzyme release determination are similar, but procedural costs (as measured by resource consumption) and duration of the procedure are lower in direct stenting. Overall success rate and mid-term clinical outcome are similar with both techniques.