Focal metallic inlay resurfacing prosthesis in articular cartilage defects: short-term results of 118 patients and 2 different implants.

BACKGROUND: The goal of this study was to share our experience with two different inlay metallic implants in the treatment of knee cartilage defects and to analyze their effects on functional scores. METHODS: This retrospective study included 118 patients operated on for focal full-thickness knee cartilage lesions, who were treated with a focal metallic inlay resurfacing prosthesis. A cobalt-chromium (Co-Cr) resurfacing implant was applied to 73 patients with a knee chondral lesion, and a biosynthetic implant was applied to 45. All patients were evaluated preoperatively and postoperatively using the KOOS, VAS, and Tegner activity scores. RESULTS: The group with the Co-Cr-resurfacing implant showed a significantly greater improvement (p < 0.001) in the Tegner and VAS scores at the 2-year follow-up examination. The KOOS scores were similar in both groups. Median patient age was similar in both groups. All patients had a follow-up of at least 2 years. The preoperative and postoperative scores were compared and significant improvements (p < 0.001) were observed. The biosynthetic implant had a higher revision rate. In the univariate analysis, age and type of implant were significantly associated with revision surgery. In the multivariate Cox-regression analysis model, the type of implant was significantly associated with revision surgery. CONCLUSION: All the patients operated with the above-mentioned implants showed significant improvements in pain and activity scores. Despite the overall good clinical results, 17% of patients with a biosynthetic implant and > 6% of patients with Co-Cr-resurfacing implant required revision surgery. Age and implant type were the main risk factors associated with revision.

Outcomes of Revision Joint Arthroplasty Due to Metal Allergy and Hypersensitivity: A Systematic Review.

BACKGROUND: Lower extremity total joint arthroplasty (TJA) is one of the most successful orthopaedic procedures. However, it is estimated that as many as 10% to 20% of TJAs could fail due to various well-known causes. Furthermore, metal allergy-related complications have recently gained attention as one of the potential causes of failure when the common reasons have been excluded. Reported symptoms from metal allergy can include chronic eczema, joint effusions, joint pain, and limited range of motion. Few studies have explored the outcomes of patients undergoing revisions due to allergic complications. The aim of our study is to quantitatively evaluate the outcomes of revision joint arthroplasty due to metal allergy and hypersensitivity.

Marginal and internal fit of pre-sintered Co-Cr and zirconia 3-unit fixed dental prostheses as measured using microcomputed tomography.

STATEMENT OF PROBLEM: Limited information is available on the precision of new metal processing technologies. PURPOSE: The purpose of this in vitro study was to evaluate the marginal and internal fit of pre-sintered cobalt-chromium (Co-Cr) and zirconia 3-unit fixed dental prostheses using x-ray microcomputed tomography. MATERIAL AND METHODS: Three-unit fixed dental prostheses were prepared on metal dies (N=12) using a typodont model from the maxillary first premolar to the first molar. A standardized preparation with a 1.2-mm chamfer (360 degrees) and a 2-mm occlusal reduction was prepared on abutment teeth. The dies were scanned and divided into 2 groups to receive the fixed dental prostheses (n=6) made of pre-sintered Co-Cr and pre-sintered zirconia. Each framework was seated on its cast, and marginal and internal discrepancies were measured at 9 points, starting from the most distal point from the pontic for the maxillary first premolar and the first molar (points 1-4, mesial; point 5, occlusal; points 6-9, distal) of each abutment tooth using microcomputed tomography. The data were analyzed using the Levene test, t test, and ANOVA (α=.05). RESULTS: When overall mean discrepancy values were compared, no significant difference was observed between pre-sintered Co-Cr and pre-sintered zirconia (P=.085). Discrepancy values for points 1, 2, and 3 were significantly different for pre-sintered Co-Cr and pre-sintered zirconia, with the lowest mean values for point 1 and the highest for point 5. On the abutment tooth basis, for the maxillary first premolar and the first molar, a significant difference was found only in points 6 (P<.001) and 8 (P<.003) for both materials. When the discrepancies for the maxillary first premolar were considered for pre-sintered Co-Cr and pre-sintered zirconia, the mean values were significantly different only at points 1 (P<.001), 2 (P=.007), and 3 (P=.003) and were smaller for pre-sintered zirconia. For the tooth the first molar, a significant difference was observed at point 2 (P=.002) and point 3 (P=.008) for both materials, where the mean values were higher for pre-sintered Co-Cr than for pre-sintered zirconia. The pairwise comparison between points showed a significant difference between measurement points within each material (P<.05). The increase in values between points 1 and 5 was evident for both pre-sintered Co-Cr and pre-sintered zirconia materials. CONCLUSIONS: Three-unit fixed dental prostheses made of pre-sintered Co-Cr or zirconia showed similar marginal and internal discrepancy values, with the highest discrepancy values at the occlusal region in both the first premolar and first molar.

The Use of CAD/CAM Cobalt-Chromium Framework to Optimize Subgingival Prosthetic Contours and Improve Esthetics: Anterior Mandibular Case Reports.

Although implant therapy in esthetically relevant areas is currently based on a prosthetically driven philosophy, anatomical and technical factors may impair ideal implant placement. In these scenarios, the clinician is frequently asked to solve the discrepancy between the implant emergence and the ideal coronal anatomy of the final restoration. This report describes how changes of the implant abutment-crown contour in specific locations may be intentionally promoted to determine improvements of the peri-implant soft tissues and overall esthetic integration. Cobalt-chromium alloys together with computer-aided design/computer-assisted manufacture technologies are critical factors in achieving this goal. Case reports for the mandibular anterior dentition demonstrated the ability to enhance biologic and esthetic results of malpositioned implants.

Comparative Study Between Cobalt Chrome and Titanium Alloy Rods for Multilevel Spinal Fusion: Proximal Junctional Kyphosis More Frequently Occurred in Patients Having Cobalt Chrome Rods.

BACKGROUND: The use of titanium alloy (Ti) rods is frequently associated with rod fracture after spinal fixation. To address this issue, cobalt chrome (CoCr) rods, which are advantageous because of their greater strength and resistance to fatigue relative to Ti rods, have been introduced. The purpose of the present study was to compare radiographic outcomes after the use of Ti versus CoCr rods in a matched cohort of patients undergoing posterior spinal fusion for treatment of spinal instability. METHODS: We retrospectively reviewed data from patients who had undergone spinal fusion involving more than 3 levels at a single institution between 2004 and 2015. Patients were matched for age, diagnosis, 3-column osteotomy, levels fused, and T score. Fifty patients with Ti rods were identified and appropriately matched to 50 consecutive patients with CoCr rods. RESULTS: The distributions of age at surgery, sex, diagnosis, 3-column osteotomy, levels fused, number of patients with previous surgical procedures, and T score did not significantly differ between the 2 groups. However, there were significant differences in length of follow-up (CoCr, 25.0 vs. Ti, 28.5 months; P < 0.001), fusion rate (CoCr, 45 [90%] vs. Ti, 33 [66%]; P = 0.004), occurrence of rod breakage (CoCr, 0 vs. T, 8 [16%]; P = 0.006), and junctional kyphosis (CoCr, 24 [46%] vs. Ti, 9 [18%]; P = 0.003). CONCLUSIONS: Our findings indicate that the use of CoCr rods is effective in ensuring stability of the posterior spinal construct and accomplishment of spinal fusion. Furthermore, our results indicate that junctional kyphosis may occur more frequently in CoCr systems than in Ti systems.

Effect of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic restorations fabricated with different CAD-CAM technologies.

STATEMENT OF PROBLEM: The use of computer-aided design and computer-aided manufacturing (CAD-CAM) for metal-ceramic restorations has increased with advances in the technology. However, little is known about the marginal and internal adaptation of restorations fabricated using laser sintering (LS) and soft milling (SM). Moreover, the effects of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic restorations fabricated with LS and SM is also unknown. PURPOSE: The purpose of this in vitro study was to investigate the effects of repeated ceramic firings on the marginal and internal adaptation of metal-ceramic copings fabricated using the lost wax (LW), LS, and SM techniques. MATERIAL AND METHODS: Ten LW, 10 LS, and 10 SM cobalt-chromium (Co-Cr) copings were fabricated for an artificial tooth (Frasaco GmbH). After the application of veneering ceramic (VITA VMK Master; VITA Zahnfabrik), the marginal and internal discrepancies of these copings were measured with a silicone indicator paste and a stereomicroscope at ×100 magnification after the first, second, and third clinical simulated ceramic firing cycles. Repeated measures 2-way ANOVA and the Fisher LSD post hoc test were used to evaluate differences in marginal and internal discrepancies (α=.05). RESULTS: Neither fabrication protocol nor repeated ceramic firings had any statistically significant effect on internal discrepancy values (P>.05). Marginal discrepancy values were also statistically unaffected by repeated ceramic firings (P>.05); however, the fabrication protocol had a significant effect on marginal discrepancy values (P<.001), with LW resulting in higher marginal discrepancy values than LS or SM (P<.05). Marginal discrepancy values did not vary between LS and SM (P>.05). CONCLUSIONS: All groups demonstrated clinically acceptable marginal adaptation after repeated ceramic firing cycles; however, the LS and SM groups demonstrated better marginal adaptation than that of LW group and may be appropriate clinical alternatives to LW.

Fretting and Corrosion in Modular Shoulder Arthroplasty: A Retrieval Analysis.

Tribocorrosion in taper junctions of retrieved anatomic shoulder arthroplasty implants was evaluated. A comparison of the tribocorrosion between cobalt-chromium and titanium alloy stems was conducted and the observations were correlated with the individual's clinical data. Adverse effects caused by metal debris and subsequent elevated serum metal ion levels are frequently reported in total hip arthroplasty. In total shoulder arthroplasty, to date only a small number of retrieval analyses are available and even fewer address the issue of tribocorrosion at the taper junctions. A total of 36 retrieved hemiarthroplasties and total shoulder arthroplasties were assessed using the modified Goldberg score. The prevalence of fretting and corrosion was confirmed in this cohort. Titanium stems seem to be more susceptible to damage caused by tribocorrosion than cobalt-chromium stems. Furthermore, stemless designs offered less tribocorrosion at the taper junction than stemmed designs. A weak correlation between time to revision and increased levels of tribocorrosion was seen. Whether or not tribocorrosion can lead to adverse clinical reactions and causes failure of shoulder arthroplasties remains to be examined.

In vitro evaluation of marginal, axial, and occlusal discrepancies in metal ceramic restorations produced with new technologies.

STATEMENT OF PROBLEM: Marginal and axial discrepancies of metal ceramic restorations are key to their long-term success. Little information is available for metal ceramic restorations fabricated with soft metal milling and laser sintering technologies. PURPOSE: The purpose of this in vitro study was to compare the marginal, axial, and occlusal discrepancies in single-unit metal ceramic restorations fabricated with new production techniques with those in a single-unit restoration fabricated using a conventional technique. MATERIAL AND METHODS: After the artificial tooth was prepared, impressions were made, and 40 dies were obtained. Dies were randomly divided into 4 groups (n=10). Cobalt-chromium (Co-Cr) cast (C), hard metal milled (HM), laser sintered (LS), and soft metal milled (SM) copings were fabricated. Marginal, axial, and occlusal discrepancies of these copings were measured using the silicone replica technique before and after the application of veneering ceramic. Data were analyzed with repeated measurements 2-way ANOVAs and Bonferroni post hoc tests (α=.05). RESULTS: Significant differences were found in the increase of marginal discrepancy after the application of veneering ceramic in the LS group (P=.016). However, no significant differences in marginal discrepancy were found whether veneering ceramic was applied to copings before or after in the other groups (P>.05). With regard to marginal and occlusal discrepancies, significant differences were found among the production techniques (P<.001 and P<.05, respectively). No significant differences in axial discrepancies were found among the groups (P>.05). CONCLUSION: This in vitro study showed that metal ceramic restorations produced with HM and newly introduced SM techniques exhibited better marginal adaptations than those produced with the LS or C technique.

Use of Supplemental Short Pre-Contoured Accessory Rods and Cobalt Chrome Alloy Posterior Rods Reduces Primary Rod Strain and Range of Motion Across the Pedicle Subtraction Osteotomy Level: An In Vitro Biomechanical Study.

STUDY DESIGN: In vitro cadaveric biomechanical study. OBJECTIVE: To assess effects of 4-rod reconstruction, rod material, and anterior column support on motion and surface rod strain in a pedicle subtraction osteotomy model. SUMMARY OF BACKGROUND DATA: Pedicle subtraction osteotomy (PSO) can correct significant sagittal deformity of the lumbar spine; however, revision rates are high. To reduce rod strain and the incidence of rod fracture, clinical use of multi-rod construction, cobalt chrome (CoCr) alloy rods, and interbody spacers adjacent to PSO has been proposed. Investigating both motion and rod strain is necessary to determine the biomechanical efficacy of these techniques. METHODS: Five specimens (T12-S1) underwent PSO at L3 with pedicle screw stabilization at L1-S1. Pedicle subtraction was adjusted to achieve a final lordosis of 70°. Flexion-extension (FE), lateral bending, and axial rotation were applied. Linear strain gauges measured surface rod strain during FE on primary and accessory rods at PSO level. Testing evaluated (1) accessory rods (4-Rod) added at PSO level versus primary rods (2-Rod); (2) Ti versus CoCr rods; and (3) lateral interbody spacers (S) inserted adjacent to PSO. One-way and three-way analysis of variance was performed (P ≤ 0.05). RESULTS: All constructs significantly reduced FE and lateral bending motion relative to intact (P < 0.001). The main effect of accessory rods in reducing FE motion was significant (P = 0.021). Accessory and CoCr rods reduced relative surface strain on the primary rod, irrespective of construct (P < 0.001). CoCr 4-Rod + S provided the greatest reduction in strain (76% decrease; P = 0.003). CONCLUSION: Accessory and CoCr rods provided greatest reduction in motion and rod strain at PSO level. Interbody devices minimally affected motion-induced strain and might act primarily to maintain disc height. Clinicians must assess whether surface strain and motion reduction minimize the incidence of rod fracture. LEVEL OF EVIDENCE: N/A.

Implant Failure of Titanium Versus Cobalt-Chromium Growing Rods in Early-onset Scoliosis.

STUDY DESIGN: Retrospective case series of one institute database. OBJECTIVE: To investigate the differences in the metallic strength of rods used for implant failure in the dual growing rod technique and evaluate clinical outcomes. SUMMARY OF BACKGROUND DATA: The dual growing rod technique in which implanted rods extend with the growth of the spine is a useful treatment for early onset scoliosis. However, many complications, particularly those associated with rods, exist. Especially, the implant failure of growing rod focused on metallic strength is unknown. METHODS: Thirteen patients (42 lengthening surgeries) who underwent surgery by this technique at our hospital from 2007 were divided into a titanium rod plus titanium connector group (T group, n = 4, 26 lengthening surgeries) and cobalt-chromium rod plus titanium connection group (C group, n = 9, 16 lengthening surgeries). The incidence of implant failure and the site of fracture were retrospectively investigated. RESULTS: Implant failure occurred in three patients in the T group, because of rod fracture in two patients and connector fracture in one. In the C group, implant failure occurred in six patients, because of rod fracture in one patient and connector fracture in seven. Fracture occurred twice in two patients. The rod fracture rate decreased with the use of cobalt-chromium rods but the rate of connector fracture increased. We performed a stress distribution analysis using the finite element method to clarify the mechanisms underlying implant failure in both groups. Regardless of the rod type, the greater load was placed on the distal rod. However, differences in the metallic strength caused the rod to fracture when titanium rods were used and connectors (weak metallic strength) to fracture when cobalt-chromium rods were used. CONCLUSION: Rod fractures occurred more commonly with titanium rods and connector fractures with cobalt-chromium rods.

Does Metal Transfer Differ on Retrieved Ceramic and CoCr Femoral Heads?

Metal transfer has been observed on retrieved THA femoral heads for both CoCr and ceramic bearing materials. In vitro wear testing has shown increased wear to polyethylene acetabular liners with the presence of metal transfer. This study sought to investigate the extent of metal transfer on the bearing surface of CoCr and ceramic femoral heads and identify prevalent morphologies. Three bearing couple cohorts: M-PE (n = 50), C-PE (n = 35), and C-C (n = 15), were derived from two previously matched collections (n = 50/group) of CoCr and ceramic femoral heads. From the three cohorts, 75% of the femoral heads showed visual evidence of metal transfer. These femoral heads were analyzed using direct measurement, digital photogrammetry, and white light interferometry. Surface area coverage and curved median surface area were similar among the three cohorts. The most prevalent metal transfer patterns observed were random stripes (n = 21/75), longitudinal stripes (n = 17/75), and random patches (n = 13/75). Metal transfer arc length was shorter in the M-PE cohort. Understanding the morphology of metal transfer may be useful for more realistic recreation of metal transfer in in vitro pin-on-disk and joint simulators studies.

Avaliação da porosidade na região de conector maior de próteses parciais removíveis a grampo / Assessment of porosity in the major connector region of removable partial dentures

A presença de porosidade interna nas estruturas metálicas de próteses parciais removíveis (PPR) é um defeito que pode resultar no fracasso das peças a médio e longo prazo. Os defeitos na peça metálica podem ser identificados de forma direta, por meio da observação visual sem qualquer tipo de aparelhagem, ou de forma indireta, quando os defeitos encontram-se internos à estrutura e, portanto, faz-se necessária a avaliação através de raios-X e/ou fotodensiômetro. Assim, este trabalho propôs uma avaliação desta porosidade por meio de um método simples, conservador e de baixo custo. A radiografia foi realizada com aparelho odontológico de consultório. Avaliaram-se todas as estruturas metálicas que seriam instaladas na clínica de prótese do Curso de Odontologia da EBMSP, durante o segundo semestre do ano de 2010 ao segundo semestre do ano de 2011. Foram analisadas 103 estruturas, sendo 59 superiores e 44 inferiores. Os resultados mostraram 453 bolhas nas estruturas superiores e 30 bolhas nas inferiores. Pôde-se concluir por meio deste estudo que a área do conector maior superior está mais propensa à falha por porosidade interna, quando comparada à área dos conectores inferiores, provavelmente pela sua extensão e dificuldade no escoamento da liga metálica quando fluidificada.

The presence of internal porosity in metal structures of removable partial dentures (RPD) is a defect that medium and long term can result in the failure of parts. Defects on the metal structure can be identified directly (by visual observation without any equipment) or indirectly when the flaws are inside the structure requiring assessment through x-rays or densitometry. Therefore this paper has proposed an evaluation of porosity by means of a simple, conservative and cost-effective method. Radiograph was performed with dental office appliance. All metal structures installed in the prosthetic clinic of the School of Dentistry EBMSP, were submitted to radiographic evaluation of during the second half of 2010 to the second half of 2011. One hundred and three structures were evaluated (44 lower structures and 59 upper strcutures). The results showed 453 bubbles in the upper structures and 30 in the lower. It was concluded that the area of the connector is most susceptible to internal porosity, when compared to the lower area of the connectors, probably due to its size and the difficulty in positioning the sprue and in disposing of the alloy when fluidized

Evaluation of castable and premachined metal base abutment/implant interfaces before and after cyclical load.

PURPOSE: The purpose of this study was to compare the vertical fit of the castable abutment/implant and premachined base metal abutment/implant interface, before and after cyclic loading. MATERIALS AND METHODS: Ten UCLA abutments were distributed in 2 groups: castable and premachined with a cobalt-chromium metal base. The abutments were cast in cobalt-chromium alloy and were screwed onto implants (3.75 × 13 mm, external hexagon) with a 32 N·cm torque. The vertical gap (in micrometers) at the interface abutment/implant was evaluated by linear microscope 2 times: after torque and after cyclic load (1 million cycles, 400 N). RESULTS: The mean values of the vertical gap at the castable abutment/implant and premachined abutment/implant interfaces before and after cyclic load were 5.33 to 6.64 µm and 7.36 to 8.16 µm, respectively. The mean values of the vertical gap were statistically analyzed (ANOVA and t test, P ≤ 0.05). Vertical gap values of the castable abutment/implant interface were not significantly different from those of the premachined abutment/implant interface, before (P = 0.154) and after (P = 0.471) cyclical loading. CONCLUSION: Castable and premachined base metal abutments showed similar gaps at the implant/abutment interface, both after applying torque and after cyclic loading.

Retentiveness of metal coping luted to teeth of uremic patients undergoing hemodialysis using five different luting cements.

OBJECTIVES: This study aimed to assess the retention of metal copings luted to uremic teeth with five different luting agents. METHODS: A total of 35 sound natural molars was collected from uremic patients and randomly assigned into five groups (n=7). The teeth were prepared for metal copings using diamond tips and water coolant. Metal copings with a loop on the occlusal surface were fabricated using base metal alloy (Rexillium III). The copings were luted using Fuji I, glass ionomer (GI); Fuji Plus, resin-modified glass ionomer (RMGI); Panavia F 2.0, resin cement; Rely X Unicem, self-adhesive cement (SA); and Adhesor, zinc phosphate cement (ZPh). All specimens were incubated at 37°C for 24 hours, conditioned in artificial saliva for 7 days, and then thermocycled for 5000 cycles (5°C-55°C). The dislodging force was measured using a universal testing machine at a crosshead speed of 2 mm/min. The mode of failure of the loaded adhesive copings was evaluated. Statistical analyses were performed using one-way analysis of variance and Tukey post hoc test. RESULTS: GI and SA cements had the highest and the lowest mean retentive strength, respectively (580.90±17.3, 406.6±12.7). There was no significant difference between ZPh, SA, and resin cements. These cements were inferior to GI and RMGI cements (p<0.05), which showed statistically similar retentive strengths. CONCLUSIONS: The results of this study support the use of glass ionomer and resin-modified glass ionomer cements for luting of metal copings to uremic teeth with retentive preparations.

Real-world use of the second-generation cobalt-chromium sirolimus-eluting stents: 12-month results from the prospective multicentre FOCUS registry.

AIMS: The FOCUS registry is a prospective, multicentre, web-based programme designed to collect clinical outcome data from real-world patients receiving the second-generation cobalt-chromium sirolimus-eluting stent (CoCr-SES). METHODS AND RESULTS: From March 2009 to February 2010, a total of 5,084 patients from 83 centres who were eligible to receive CoCr-SES were enrolled in the FOCUS registry. The primary endpoint was 12-month major adverse cardiac events (MACE, defined as the composite of cardiac death, myocardial infarction [MI], and target vessel revascularisation [TVR]). One-year data were available for 5,013 (98.6%) of the 5,084 patients enrolled. The primary endpoint occurred in 174 (3.47%) of 5,013 patients, consisting of 43 (0.86%) cardiac deaths, 132 (2.63%) MI, and 46 (0.92%) TVR. According to the Academic Research Consortium definition, definite and probable stent thrombosis (ST) occurred in 0.52% (26/5,013) of patients, including 19 cases of early ST and 7 of late ST. The 12-month MACE rates were 3.73% and 2.60% for extended-use and standard-use patients, respectively (p=0.065). CONCLUSIONS: The second-generation CoCr-SES was associated with low rates of 12-month MACE and ST in a broad spectrum of patients, thereby confirming the clinical safety and efficacy of this stent in a real-world setting.

Synergy between direct coronary stenting technique and use of the novel thin strut cobalt chromium Skylor™ stent: the MACE in follow up patients treated with Skylor stent [MILES Study].

BACKGROUND: Despite significant improvements in stent platform, currently available bare-metal stents (BMS) are still associated with restenosis. Thin-strut design cobalt-chromium alloys hold the promise of improving results of BMS, especially when implanted with direct technique. We performed an observational study to appraise outcomes of the novel Skylor™ stent, stratifying outcomes according to stenting technique. METHODS AND RESULTS: We included all consecutive patients undergoing coronary stenting with Skylor™ at 2 centers between 2006 and 2009. The primary end-point was the long-term rate of major adverse cardiac events (MACE, i.e. death, myocardial infarction (MI), coronary artery bypass grafting (CABG) or target vessel revascularization (TVR)). As pre-specified analysis, we compared patients undergoing direct stenting versus those stent implantation following predilation. A total of 1020 patients were included (1292 Skylor™ stents), with procedural success obtained in 99%. Comparing patients undergoing direct stenting (66%) versus pre-dilation (34%) at 16±7 months of follow-up, MACE had occurred in, respectively, 8% versus 14% (p=0.001), with death in 1% versus 2= (p=0.380), MI in 1% versus 2% (p=0.032), CABG in 0.2% versus 2% (p=0.012), and TVR in 6% versus 9% [p=0.071]. Even at multivariable analysis with propensity adjustment, direct stenting was associated with significantly fewer MACE [hazard ratio 0.60 [0.38-0.93], p=0.024]. CONCLUSIONS: This observational study suggests the presence of a beneficial synergy between direct coronary stenting technique and use of the novel thin-strut cobalt-chromium Skylor™ stent in real-world patients undergoing PCI.

Influence of the loading frequency on the wear rate of a polyethylene-on-metal lumbar intervertebral disc replacement.

Pre-clinical wear testing of intervertebral disc prostheses is commonly carried out according to ISO 18192-1. Ten million multiaxial loading cycles are applied at a frequency of 1 Hz. At this frequency, testing takes about 4 months. Testing at higher frequencies would therefore be desirable. ISO 18192-1 also offers testing at 2 Hz; however, it says the impact on the implant material behaviour as well as on the accuracy of the test machine shall be investigated by the user. Since such data are not available so far, the aim of this study was to carry out comparative wear tests at 1 and 2 Hz. Seven Prodisc-L lumbar disc prostheses were tested. After a pre-soak period, the implants were placed in specimen cups filled with calf serum, mounted to a Spine Wear Simulator and loaded according to ISO 18192-1. Testing was carried out at a temperature of 37 ± 2 °C. Four million loading cycles were applied at 1 Hz and eight million at 2 Hz in an alternating sequence. Each time after 12 days of testing the implants were removed to measure the weight and the height of the polyethylene cores. Then, the test serum was exchanged and the implants were remounted to the testing machine. The mean wear rate was 5.6 ± 2.3 mg per million cycles at 1 Hz and 7.7 ± 1.6 mg per million cycles at 2 Hz during the first six million loading cycles (p < 0.05) and 2.0 ± 0.6 and 4.1 ± 0.7 mg per million cycles during the second six million cycles (p < 0.05). Similarly, the mean heightloss was also smaller at 1 Hz than at 2 Hz (p < 0.05) with -0.02 ± 0.02 mm versus -0.04 ± 0.02 mm per million cycles during the first half of testing and -0.01 ± 0.01 versus -0.02 ± 0.01 mm per million cycles during the second half. The accuracy of the test machine was within the limits described by ISO 18192-1 at both frequencies. The results showed that the wear rate was higher at the beginning than at the end of testing. Also, the results indicated that testing at 2 Hz increases the wear rate compared with 1 Hz in case of a polyethylene-on-metal implant design. In the absence of retrieval studies it is difficult to decide which rate results in a more physiological wear pattern. However, a loading frequency of 1 Hz is probably closer to physiology than 2 Hz since the loading amplitudes prescribed by ISO 18192-1 are high. They rather represent movements like tying shoes or standing up from a chair than walking or sitting. The authors therefore suggest testing at 1 Hz.

Detection of very early stent healing after primary angioplasty: an optical coherence tomographic observational study of chromium cobaltum and first-generation drug-eluting stents. The DETECTIVE study.

BACKGROUND: Lack of stent coverage appears to be associated with stent thrombosis, a problem of particular concern in patients with ST elevation myocardial infarction (STEMI). METHODS: The DETECTIVE European Multicenter Registry was set up to address the early modality of stent healing in the setting of STEMI. The Registry compared, with an early optical coherence tomography (OCT) evaluation performed at 3-7 days, the patterns of coverage and apposition of the first generation of drug-eluting stents (DESs) and cobalt chromium non-drug-eluting stents (CCSs) that were deployed in culprit lesions and in non-culprit segments. The Registry included only patients with a multi-vessel disease to allow, at 3-7 days from the first angioplasty, a deferred OCT examination and a staged intervention in another vessel. RESULTS: 28 stented lesions (15 patients) eventually entered the final OCT assessment. 13 stents were first-generation DESs, while the remaining 15 were CCSs. 18 stents (64%) were deployed at culprit STEMI lesions, and the remaining 10 (36%) were deployed at non-culprit sites. The distribution of clinical and procedural variables in DES and CCS as well as in culprit and non-culprit sites was not different. In total, 27,019 struts were analysed in 28 stents. The percentage of stent uncoverage in the overall analysis was 11.7%, while the percentage of malapposition and that of struts covered with thrombus were 4.8% and 2.2%, respectively. A low percentage of strut uncoverage was found in all the four studied subgroups: DES 12.8%, CCS 10.9%, stents deployed in culprit lesions 13.2% and stents deployed in non-culprit lesions 8.7%. CONCLUSIONS: In conclusion, our data show that in patients with STEMI, a very high percentage of stent struts is covered by an early thin rim of tissue within 7 days after stent positioning. The present data bring new insights in the mechanism and timing of strut coverage.

Influence of metal alloy and the profile of coronary stents in patients with multivessel coronary disease.

BACKGROUND: In Brazil, despite the recommendations of the Brazilian Society of Hemodynamics and Interventional Cardiology, the National Health System has not yet approved the use of drug-eluting stents. In percutaneous coronary interventions performed in the public and part of the private health care system, bare metal stents are used as the only option. Therefore, new information on bare metal stents is of great importance. The primary endpoint was to evaluate the influence of the alloy and the profile of coronary stents on late loss and restenosis rates 6 months after implantation in patients with multivessel coronary disease. METHODS: Single center, randomized and prospective study comparison of cobalt-chromium versus stainless steel stent implantation in 187 patients with multivessel coronary disease. At least one cobalt-chromium and one stainless steel stent were implanted per patient. RESULTS: Mean age of patients was 59.5 + 10.1 years with a prevalence of males (66.3%) and patients with acute coronary syndrome (56%). Baseline clinical characteristics were similar with hypertension in 146 (78%), dyslipidemia in 85 (45.5%) and diabetes in 68 (36.4%). Two hundred and twenty-nine cobalt-chromium and 284 stainless steel stents were implanted. Angiographic variables showed no statistically significant difference. Angiographic follow-up to 6 months after implantation showed similar late loss and restenosis rates. CONCLUSION: The use of two different alloys, stainless steel and cobalt-chrome stents, in the same patient and in the same vessel produced similar 6-month restenosis and late loss rates.

Long-term stability of self-assembled monolayers on electropolished L605 cobalt chromium alloy for stent applications.

Commercially available drug-eluting stents have the potential to induce inflammatory and hypersensitive adverse reactions due to their polymer coating. The use of self assembled monolayers (SAMs) as an alternate drug delivery platform for stents has recently been demonstrated. In this study, the formation and stability of phosphonic acid SAMs were investigated using the material and surface preparation commonly used to make ultra-thin stent struts-electropolished L605 Cobalt Chromium (CoCr) alloy. Methyl (⁻CH3) and carboxylic acid (⁻OOH) terminated phosphonic acid SAMs were coated on electropolished CoCr alloy using a combination of solution immersion and dip-evaporation cycle deposition methods. SAMs-coated CoCr alloy specimens were thoroughly characterized using contact angle goniometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). These characterizations suggested that uniform and well-ordered monolayers were coated on the electropolished CoCr alloy. The long-term physiological stability of monolayers was investigated in tris-buffered saline (TBS) at 37°C for up to 28 days. Contact angles, FTIR, XPS, and AFM suggested that both ⁻CH3 and ⁻COOH terminated phosphonic acid SAMs desorb from electropolished CoCr alloy surfaces in a biphasic manner. A significant desorption of ⁻CH3 and ⁻COOH terminated SAMs occurs within 1-3 days followed by a slower desorption for up to 28 days. Thus, there is a need to develop techniques that can improve the long-term stability of SAMs on electropolished CoCr alloy for stent and other biomedical applications.