<i>In vitro</i> testing of silicone rubber heart‐valve poppets for lipid absorption

Carmen, Raleigh; Kahn, Paul W.

doi:10.1002/jbm.820020406

Cited by 47 publications

(9 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In addition, silicone devices have been shown to fail in longterm implants, particularly in flex-fatigue applications such as finger joints2' and heart valve poppets. 22 The mechanism of in vivo degradation is not clear. Chan et al23 studied the exchange of Si-0 groups with P-0 groups that are found in some nucleic acids and phosphates.…”

Section: Discussionmentioning

confidence: 99%

Materials and design concepts for an intervertebral disc spacer. I. Fiber‐reinforced composite design

Langrana

Parsons²,

Lee³

et al. 1994

J of Applied Biomaterials

View full text Add to dashboard Cite

The intervertebral disc is a complex joint anatomically and functionally. It may be displaced or damaged due to trauma or a disease process. To alleviate this condition, it may be necessary to remove the involved disc surgically and fuse the two adjacent vertebrae. Fusion is one option; however, replacing the damaged disc (or part thereof) with a suitable synthetic equivalent to allow near normal joint motion is more desirable. Unfortunately, the complex mechanical properties of the lumbar disc cannot be duplicated with homogeneous synthetic materials (polymers). To overcome this fundamental problem we have developed rational designs utilizing biocompatible thermoplastic elastomers of various stiffnesses (durometers) with and without fiber reinforcements. Our design consisted of three components analogous to the natural end plates, annulus, and nucleus. In this study only the fiber-reinforced design is considered. The variables examined in the present study included orientation of the fiber layers, number of fiber layers, and order of the reinforcing layers. The results of mechanical testing of the fiber reinforced disc spacer indicate that the range of compressive and torsional properties can be achieved. The results further demonstrate that properly developed, this design results in properties similar to the natural disc. Designs developed provided adequate compression and compression torsion properties for a synthetic spine disc spacer.

show abstract

Section: Discussionmentioning

confidence: 99%

Materials and design concepts for an intervertebral disc spacer. I. Fiber‐reinforced composite design

Langrana

Parsons²,

Lee³

et al. 1994

J of Applied Biomaterials

View full text Add to dashboard Cite

show abstract

“…In the case of silicone rubber balls used as mitral-valve poppets some changes can occur, namely discoloration, weight gain, swelling, wear and splitting in a small percentage [2,3]. The probable reason for all these changes is lipid absorption [2,3], particularly as Carmen and Kahn [4,5] have duplicated the effect in vitro. Conceivably such absorption could contribute to mechanical failure, as chemical deterioration of the surface is known to be a prime initiator of stress corrosion and corrosion fatigue failures of polymers [ 6 ] .…”

Section: Introductionmentioning

confidence: 97%

Environmental fatigue testing of silastic finger joint prostheses

Weightman

Simon

Rose

et al. 1972

J. Biomed. Mater. Res.

View full text Add to dashboard Cite

SummaryHeat vulcanized silicone elastomer (Silastic-Dow) has been in clinical use as a prosthetic replacement material for over a decade. When subjected to operating stress in body fluids, as in cardiac poppet-valves, failure has occurred. Fractures of silastic finger-joint prosthesis have also been experienced.Chemical and fractographic analyses of such failed finger-joint prostheses raise the suspicion of fatigue failure. Severe discoloration of the implant at the point of maximal stress concentration, the presence of significant amounts of triglyceride and cholesterol on the fractured prostheses, and the pattern of fracture markings indicate that fracture was due to a combination of chemical surface deterioration and stress concentration, Study of the method of surgical insertion of these prostheses suggests failure to completely excise the volar plate and other palmar joint structures could create a s t e p off and sufficiently increase the stress in the bending element of the device to cause fracture. In vitro cyclic testing a t 37°C in serum failed to cause fracture of these devices after 10 million cycles, but did produce gradual discoloration of the entire prosthesis which began and was most noticeable at the point of bending. Although the prostheses adsorb lipid, which may produce surface deterioration, it is anticipated that properly inserted, the service life of these devices should be more than adequate for full clinical application.

show abstract

“…Therefore, it is likely that the epileptogen in these cases was not DMPSO itselfbut a pyrolysis product of DMPSO which was extracted from the overcured membrane during perfusion. Indeed, it has been demonstrated that the extractable content of DMPSO rubber increases as it is overcured (Carmen and Kahn, 1969), although the byproducts formed by such overcuring have not been characterized.…”

Section: Discussionmentioning

confidence: 99%

Electroencephalographic seizures during cardiopulmonary bypass

Stockard

Calanchini

Bickford

et al. 1974

Journal of Neurology, Neurosurgery & Psychiatry

View full text Add to dashboard Cite

SYNOPSIS Eleven cardiac operations are reported in which there was electroencephalographic and/or clinical evidence of seizure activity during cardiopulmonary bypass (CPB). In four patients seizure activity appeared after acute episodes of cerebral ischaemia resulting from either hypotension or pump-generated emboli occurring at the beginning of CPB, or from air embolism occurring at the end of CPB when the myocardium was closed and defibrillated. In the remaining seven patients the seizures appeared to result from the synergistic action of a toxic substance in the perfusate with pre-existing or CPB-induced alterations in cerebral physiology.While numerous reports have appeared over the last 15 years documenting the depression of electrocortical activity which frequently accompanies cardiopulmonary bypass (CPB) (Theye et al., 1957;Silverstein et al., 1960;Lorenz and Hehrlein, 1970), excitatory or epileptiform electroencephalographic (EEG) activity associated with CPB has rarely been observed. The lack of data on epileptic phenomena during CPB may partly reflect the relative infrequency with which the intraoperative EEG is recorded and the use of neuromuscular blocking agents during CPB which would mask any clinical manifestations of seizures. Although probably very rare, seizure activity during CPB is of clinical importance inasmuch as it represents a potentially fatal complication of open-heart surgery. The dangers of having a violent motor seizure during a critical portion of the surgical procedure are obvious. Even if complete neuromuscular blockade is present at the time that electrical seizure activity initially develops, the later unmasking of motor convulsions as the muscle relaxants wear off could pose an unallowable circulatory stress (Storm van Leeuwen et al., 1961). The possibilities of progression to status epilepticus (Seamans et al., 1968;Radvanyi et al., 1970) or of 'consumption anoxia' of the cerebral cortex resulting from the greatly increased oxygen demands of the discharging neurones (Davies and 181 Remond, 1947;Meyer and Waltz, 1961) further suggest the desirability of controlling even a purely electrographic seizure during CPB.The present study investigates the electroencephalographic and clinical circumstances of a number of epileptic seizures occurring during extracorporeal circulation in an attempt to elucidate underlying mechanisms and appropriate therapy of these phenomena and their possible relevance to clinical epilepsy. METHODEleven electrographic seizures during CPB are reported which occurred in a combined series of 280 patients undergoing cardiac surgery with CPB at our hospitals between 1965 and

show abstract

In vitro testing of silicone rubber heart‐valve poppets for lipid absorption

Cited by 47 publications

References 2 publications

Materials and design concepts for an intervertebral disc spacer. I. Fiber‐reinforced composite design

Materials and design concepts for an intervertebral disc spacer. I. Fiber‐reinforced composite design

Environmental fatigue testing of silastic finger joint prostheses

Electroencephalographic seizures during cardiopulmonary bypass

Contact Info

Product

Resources

About