Long-term Mechanical Reliability Research Articles

Long-Term Mechanical Circulatory Support System Reliability Recommendation by the National Clinical Trial Initiative Subcommittee

The Long-Term Mechanical Circulatory Support (MCS) System Reliability Recommendation was published in the American Society for Artificial Internal Organs (ASAIO) Journal and the Annals of Thoracic Surgery in 1998. At that time, it was stated that the document would be periodically reviewed to assess its timeliness and appropriateness within 5 years. Given the wealth of clinical experience in MCS systems, a new recommendation has been drafted by consensus of a group of representatives from the medical community, academia, industry, and government. The new recommendation describes a reliability test methodology and provides detailed reliability recommendations. In addition, the new recommendation provides additional information and clinical data in appendices that are intended to assist the reliability test engineer in the development of a reliability test that is expected to give improved predictions of clinical reliability compared with past test methods. The appendices are available for download at the ASAIO journal web site at www.asaiojournal.com.

First American experience with the Terumo DuraHeart™ left ventricular assist system

Since the first implantation of a left ventricular assist system (LVAS) 45 years ago, LVAS therapy has emerged as a viable option for the treatment of advanced heart failure. The current generation of LVASs in clinical evaluation has design features enabling longer and more reliable support durations. We describe the operating characteristics of the DuraHeart LVAS (Terumo Heart, Inc., Ann Arbor, MI). The DuraHeart LVAS is a magnetically-levitated centrifugal pump that began a FDA-approved clinical trial for evaluation of bridge to transplant indication in July of 2008. Magnetic levitation of the spinning-pump impeller is hypothesized to improve long-term mechanical reliability and biological compatibility of the pump. Other design features make the DuraHeart LVAS particularly suited for implantation without cardiopulmonary bypass (CPB). A description of the implant procedure for the first six American implants of the DuraHeart LVAS both on-CPB and off-CPB, including CPB techniques employed, are discussed. While it is still very early in the DuraHeart LVAS experience, the initial outcomes of the first six patient implants would suggest that the device is a safe and effective LVAS.

Outcomes and Satisfaction Rates for the Redesigned 2-Piece Penile Prosthesis

We evaluated long-term viability, quality of life and satisfaction with the redesigned 2 piece Ambicor inflatable penile prosthesis. This device underwent revision of the rear tip extender and reinforcement of the pump tubing connection to decrease fluid leak failure in 1998. In this retrospective analysis we evaluated 146 men with erectile dysfunction at 2 centers who underwent device implantation between June 1999 and October 2004 with the redesigned prosthesis. Patient information forms were completed, including patient history, surgical information and revision data. Patients were mailed a modified Erectile Dysfunction Inventory of Treatment Satisfaction questionnaire, a modified Erectile Dysfunction Inventory of Treatment Satisfaction Partner survey and a questionnaire regarding pertinent inflatable penile prosthesis questions. A total of 146 men with a mean age of 58.7 years (range 25 to 78) were evaluated after inflatable penile prosthesis placement. Time from implant to followup was 3 to 73 months (mean 38). Only 1 device (0.7%) was removed due to infection. One implant (0.7%) was replaced due to fluid loss and 1 (0.7%) was revised due to improper sizing. Kaplan-Meier life table analysis indicated that the percent of patients free from reoperation was 99.2% at 12 months, 99.2% at 36 months and 91% at 48 months or greater. Of the 101 subjects completing the survey the average patient used the prosthesis 5 times monthly and 88.9% reported continued use. Of the patients 91% said that it was easy to use and 95% had little to no trouble learning to use it, while 84% stated that the inflatable penile prosthesis provided good to excellent rigidity for coitus. Overall patient and partner satisfaction was 85% and 76%, respectively. Of the patients 86% said that they would recommend the prosthesis to friends or if need be undergo the procedure again. The redesigned Ambicor 2-piece penile prosthesis appears to be safe and effective. It is associated with a low rate of revision as well as high patient and partner satisfaction.

Long-Term Mechanical Reliability of AMS 700CX™/CXM Inflatable Penile Prosthesis

We determined the long-term mechanical reliability of the AMS 700CX/CXM inflatable penile prosthesis in men with organic erectile dysfunction. A total of 455 consecutive patients underwent implantation of an AMS 700CX/CXM inflatable penile prosthesis between April 1986 and July 2004. Using telephone interviews and mailed questionnaires we obtained followup on 380 of 455 patients (83%). Data were obtained with regard to 2 end points, including overall failure and mechanical failure caused by any malfunctioning component. Followup was 0.49 to 231 months (median 91.5). Ten-year Kaplan-Meier estimates of overall and mechanical survival were 74.9% (95% CI 69.2 to 81.1) and 81.3% (95% CI 75.7 to 87.3), respectively. To our knowledge this is the longest followup of any inflatable penile prosthesis showing overall and mechanical survival by Kaplan-Meier estimates.

AMS Three–Piece Inflatable Implants for Erectile Dysfunction: A Long–Term Multi–Institutional Study in 200 Consecutive Patients

Objectives: The aim of this study was to assess the longterm mechanical reliability of AMS (American Medical Systems) three–piece inflatable implants and their impact on patient–partner satisfaction in 200 consecutive patients with erectile dysfunction who underwent surgery in five different institutions.Methods: Patient charts included in the study were collected and extensively assessed to record pre– and intraoperative data and postoperative complications. All patients and 120 partners were then seen often in the office at a mean follow–up of 59 months (range 6–130) and they were extensively questioned about function of the device and its impact on the couple’s sexual life.Results: At the long–term follow–up, 185 patients (92.5%) were still engaging in sexual intercourse with a mean frequency of 1.7/week. Patients and partners reported prosthetic erections as excellent, satisfactory or poor in 96 (48%), 100 (50%) and 4 (2%) cases, and in 20 (17%), 80 (66%) and 20 (17%) cases, respectively. Postoperative sexual activity was considered excellent, satisfactory or poor by 140 (70%), 44 (22%) and 16 (8%) patients and by 34 (28%), 81 (68%) and 5 (4%) partners, respectively. Reasons for patients’ complaints included postoperative penile shortening in 60 (30%) cases and poor glandular engorgement in 40 (20%) cases. Partners’ main complaint was unnaturalness of the prosthetic erection, a factor reported by 30 (25%) subjects. Complications requiring surgical exploration included infection in 12 patients (6%) and mechanical failure in 8 patients (4%). Kaplan–Meier estimates demonstrated significantly decreased mechanical survival for the Ultrex type of cylinders compared to the CX type of cylinders.Conclusions: AMS three–piece inflatable implants provide an overall patient and partner satisfaction rate of 92 and 96%, respectively. However, postoperative penile shortening and poor glandular engorgement were the causes of some complaints among the patient population as well as the unnaturalness of prosthetic erection among female partners. In the long–term, mechanically speaking, CX cylinders seem to be more reliable than the Ultrex ones.

Long-Term Mechanical Reliability of Multicomponent Inflatable Penile Prosthesis: Comparison of Device Survival

Long-Term Mechanical Reliability of Multicomponent Inflatable Penile Prosthesis: Comparison of Device Survival

Long-Term Mechanical Reliability of Multicomponent Inflatable Penile Prosthesis

Long-Term Mechanical Reliability of Multicomponent Inflatable Penile Prosthesis

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and The Society of Thoracic Surgeons: Long-term mechanical circulatory support system reliability recommendation

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.

Long-term mechanical reliability of multicomponent inflatable penile prosthesis: comparison of device survival

Objectives. To determine the mechanical reliability of multicomponent inflatable penile prosthesis, comparing five different types of devices, as well as the two-piece versus three-piece as a group. Methods. We followed 83 patients with two-piece and 283 patients with three-piece inflatable penile prostheses for a mean time of 66 months. At a cutoff of 63 months, mechanical complication rates were reviewed and statistically analyzed. Results. Thirty-one device-related complications occurred, and all were secondary to fluid leakage. The Mentor Alpha-1 prosthesis was significantly better than the Mentor Mark-II in terms of mechanical reliability ( P = 0.01). A trend was noted toward the AMS 700 Ultrex inflatable penile prosthesis having fewer mechanical complications than the Mentor Mark-II ( P = 0.06). In addition, a trend toward all three-piece prostheses being more mechanically reliable than the two-piece was noted ( P = 0.08). The Mentor Alpha-1 device had a higher cumulative proportional survival (0.957) than all other devices (0.842 for AMS 700 Ultrex, 0.839 for AMS 700 CX, 0.783 for Mentor GFS, and 0.750 for Mentor Mark-II). Conclusions. As a group, a trend was noted toward the three-piece prosthesis having better mechanical reliability than the two-piece prosthesis. Comparisons between the individual types of prostheses showed that the Mentor Alpha-1 device was significantly more mechanically reliable than the Mentor Mark-II device, and a trend was noted toward the AMS 700 Ultrex device having fewer mechanical complications than the Mentor Mark-II. The Mentor Alpha-1 prosthesis had the highest cumulative proportional survival.

Fatigue Behavior of GeO2-SiO2 Glasses

AbstractThe fatigue behavior of binary oxide glasses in the germania-silica system is interesting since it influences the long-term mechanical reliability of products made of these glasses. Dynamic fatigue tests were carried out in four-point bending in 100% RH using tumble abraded rods. The fatigue data were obtained as a function of GeO2 content which ranged from 0 to 24 mole %. In addition, other physical properties of these glasses, such as the thermal expansion coefficient, were measured as a function of GeO2 content. The results of these tests and analyses are highlighted in this paper.

LONG-TERM MECHANICAL RELIABILITY OF AMS 700 SERIES INFLATABLE PENILE PROSTHESES: COMPARISON OF CX/CXM AND ULTREX CYLINDERS

Recently, we have noted an increasing incidence of revisions being performed in patients implanted with the length and girth expanding AMS 700 Ultrex* inflatable penile prosthesis. This observation prompted us to compare the long-term mechanical reliability of the AMS Ultrex inflatable penile prosthesis versus the girth-expanding AMS 700 CX* or CXM* inflatable penile prosthesis in men with organic erectile dysfunction. Using chart review, mailed questionnaires and telephone interviews, we obtained accurate followup on 111 of 142 (78.2%) patients with CX/CXM implanted between June 1986 and September 1995, and on 152 of 179 (84.9%) patients implanted with Ultrex between October 1989 and September 1995. The CX/CXM and Ultrex groups were compared with regard to 3 end points: 1) mechanical failure caused by any malfunctioning component, 2) device failure caused by any cylinder complication and 3) cylinder aneurysms/leaks. Followup ranged from 1.0 to 112.0 months for the CX/CXM group (mean 47.2 months), and 0.7 to 71.5 months for the Ultrex group (mean 34.4 months). CX/CXM versus Ultrex group comparison demonstrated 10 CX/CXM mechanical failures (9.0%) versus 26 Ultrex failures (17.1%), p = 0.001; 5 CX/CXM cylinder complications (4.5%) versus 13 Ultrex cylinder complications (8.6%), p = 0.0292; and 3 CX/CXM cylinder aneurysms/leaks (2.7%) versus 9 in the Ultrex group (5.9%), p = 0.0162. Kaplan-Meier estimates demonstrated significantly decreased mechanical survival in all 3 categories for Ultrex inflatable penile prosthesis versus CX/CXM inflatable penile prosthesis. Although Ultrex cylinders provide length and girth expansion, Ultrex cylinders exhibit an increased mechanical failure rate at shorter followup compared with CX/CXM cylinders. This increased propensity for Ultrex cylinder problems should be closely monitored.

Effects of surface hydration on the deposition of silane monolayers on silica optical fiber

A polymer coating applied to a silica optical fiber prevents mechanical damage to the fiber associated with handling. The adhesion of this coating is critical to the long-term mechanical reliability of the fiber. Typically, silane coupling agents that bond to the polymer and the silica fiber surface are mixed into the polymer before it is applied to the fiber. Self-assembled monolayers (SAMs) of octadecyltrichlorosilane (OTS) are a good model system for studying the reaction of silane coupling agents to the fiber surface. X-ray photoelectron spectroscopy (XPS) of OTS monolayers deposited on both silicon wafers, with an oxide layer, and silica glass fiber has demonstrated that incomplete monolayers form on dehydrated silica, but with partial rehydration a complete, well-ordered monolayer can be formed. These results are consistent with our previous work on flat, fused silica substrates in which the film coverage and degree of ordering were obtained from infrared spectroscopy of the monolayers. There is greater OTS coverage on a dehydrated fiber than on a dehydrated flat wafer. These results show that improved adhesion using coupling agents in fiber coatings may be obtained by exposure for several minutes of the freshly drawn fiber to water before coating. The work also shows the value of using XPS to study the surface of an optical fiber. The degree of OTS coverage and film density on a fiber can be obtained by comparing XPS measurements made after preparing SAMs in the same way on a fiber and a flat substrate.

Comparison of the Creep and Creep Rupture Performance of Two HIPed Silicon Nitride Ceramics

Measurements of the tensile creep and creep rupture behavior were used to evaluate the long‐term mechanical reliability of a commercially available and a developmental hot isostatically pressed (HIPed) silicon nitride. Measurements were conducted at 1260° and 1370°C utilizing button–head tensile specimens. The stress and temperature sensitivities of the secondary creep rates were used to estimate the stress exponent and activation energy associated with the dominant creep mechanism. The stress and temperature dependencies of creep rupture life were determined by continuing individual creep tests to specimen failure. Creep deformation in both materials was associated with cavitation at multigrain junctions. Two‐grain cavitation was also observed in the commercial material. Failure in both materials resulted from the evolution of an extensive damage zone. The failure times were uniquely related to the creep rates, suggesting that the zone growth was constrained by the bulk creep response. The fact that the creep and creep rupture behaviors of the developmental silicon nitride were significantly improved compared to those of the commercial material was attributed to the absence of cavitation along two‐grain junctions in the developmental material.

Bioceramics: From Concept to Clinic

Ceramics used for the repair and reconstruction of diseased or damaged parts of the musculo‐skeletal system, termed bioceramics, may be bioinert (alumina, zirconia), resorbable (tricalcium phosphate), bioactive (hydroxyapatite, bioactive glasses, and glass‐ceramics), or porous for tissue ingrowth (hydroxyapatite‐coated metals, alumina). Applications include replacements for hips, knees, teeth, tendons, and ligaments and repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jaw bone, spinal fusion, and bone fillers after tumor surgery. Carbon coatings are thromboresistant and are used for prosthetic heart valves. The mechanisms of tissue bonding to bioactive ceramics are beginning to be understood, which can result in the molecular design of bioceramics for interfacial bonding with hard and soft tissues. Composites are being developed with high toughness and elastic modulus match with bone. Therapeutic treatment of cancer has been achieved by localized delivery of radioactive isotopes via glass beads. Development of standard test methods for prediction of long‐term (20‐year) mechanical reliability under load is still needed.

Scanning Tunneling Microscopy of Optical Fiber Corrosion: Surface Roughness Contribution to Zero‐Stress Aging

Strength, fatigue resistance, and zero‐stress aging behavior control the long‐term mechanical reliability of optical fibers. Zero‐stress aging refers to the loss of strength of high‐strength glass fibers after exposure to some corrosive environments in the absence of stress. Understanding the effect of the chemical environment under zero stress on the subsequent fracture strength of optical fibers is important because optical fibers in service will probably encounter water and other chemical species while exposed to zero‐ or low‐stress conditions. In this work, the strength of fibers aged under zero‐stress conditions at 80°C in deionized water has been measured. Scanning tunneling microscopy was also used to measure the roughening of the fibers from corrosion at intervals during the aging. The product of the median inert strength of fibers aged for various times and the square root of the roughness depth of fibers was constant within experimental error. The results show that surface roughening contributes to zero‐stress aging in silica fibers.

Recent Advances in the Diagnosis and Management of Impotence

Recent experience with the implantation of the OmniPhase, FlexiFlate, and Hydroflex penile prostheses at our institution has shown all three to provide good axial rigidity and relatively good concealment, although the phallus tends to be much more expanded than normal with all three devices when they are in the nonfunctional position. Urologists who are familiar with penile implantation surgery will encounter no technical difficulties with the implantation of these new devices. Rather, long-term mechanical reliability will be the crucial factor that will cause implanting surgeons and their patients to shift from one prosthesis to another.