Profile of Users:

The study of medical records and production data regarding inflatable penile implants suggests common problems for the currently available implants derived from the early-seventies designs. For practical purposes, the difficulties encountered during early clinical trials remain and corrective measures have not been successful. User of the devices have a collective history of short term and long term problems. This is greatly exacerbated by the emerging profile of typical users. They include a large proportion of patients with extensive and repeated medical procedures for tumor resection, lower limb circulatory disorders and urological problems including component replacements in connection with failure of penile implants and other devices for urinary dysfunction. Increasingly, the devices currently implanted replace a prior device which failed or for which the user suffered major sequelae.

Erectile dysfunction, sometimes secondary to other serious conditions, allows the inclusion of more difficult classes of potential candidates. This population is enriched with particularly vulnerable individuals, some of whom have histories of spinal cord trauma, diabetes, congenital anomalies, radiotherapy, immunity suppression treatments and chemotherapeutic anti-tumor agents. Another sub-population includes individuals subjected to abdominal trauma and peripheral vascular surgery procedures such as aorta-femoral or femoro-popliteal bypass for replacement of damaged or occluded arteries and related procedures for salvage of limbs affected by thromboembolic anomalies.

The implantation of a complex penile prosthesis system in individuals impaired by prior surgeries for systemic disorders and cancer, constitutes major supplemental trauma with above average risk. The comparatively advanced age of many candidates attracts further complications such as infection and poor healing. In summary, the primary candidates for penile implants are amongst the most unsuitable individuals for surgery in the perineal/urinary tract area. The direct linkage between the penile vasculature and the circulatory system adds another complexity and greatly magnifies the risks associated with penile implants.

Commercial Aspects:

Inflatable penile prostheses are assemblies of hollow parts filled with aqueous fluids and pump-like components which allow movement of these fluids. The fluids are used to produce hydraulic pressure in inflatable components within the penis and thus simulate erectile function. Items of this kind are normally sold as arrays of separate parts which are modified and assemble extemporaneously. Such items are presently made by at least two domestic manufacturers and possibly as many as five worldwide. All items are derived basically from a common technological ancestor. The principal participants are American Medical Systems (AMS), the Mentor Corporation and McGhan/Inamed.

Because of resurgent commercial activity in penile implant use in the late- eighties and the release of new products with very limited prior studies, many patients have participated, perhaps unknowingly, in unsanctioned clinical studies in the sense that they received modified products that may be deemed investigational in some quarters. This may have significantly contributed to morbidity.

Historical Background - Malleable Penile Implants:

Penile prostheses are intended to simulate artificial rigidity of the penis without requiring an increase in local changes in the blood pressure which would otherwise be required to achieve a conventional erection. The original approaches are based on comparatively old concepts which deviate markedly from the normal anatomic principles which would apply to male erectile function. The first commercially produced devices were the outcome of prototypes investigated by urologists Small and Carrion. Clinical use began in the sixties and relied on simple implantable stiffening components inserted in the penis. Significant usage of such devices took place in the seventies. The items consisted of semi-rigid, rod-like objects which could be manipulated and set thus imparting significant rigidity for sexual function. They were mostly manufactured of elastomeric coating materials with malleable or segmented articulated cores. Outwardly they resembled plastic cylinders stiffened by semi-flexible metallic or plastic elements at the center which imparted rigidity and allowed alterations of position.

The items were meant to be inserted into existing cylindrical spaces in the penis and would be surgically implanted deeply within the perineal area. Such devices would remain in the set position until displaced manually. Being semi-articulated structural elements, they would lock the penis in the last set position. Accordingly, the penis would be bent upward or downward to simulate an erect or a flaccid condition. This type of product was comparatively simple, had low intrinsic risk other than tissue trauma and core failure leading to dysfunction. They enjoyed limited popularity and several models remain available at present. Some users perceive the systems as artificial and inconvenient.

The intrinsic rigidity of the object has been associated with long term problems, specifically trauma to tissue at both the distal and the proximal end of the rods. Other problems are the result of proximity of the rods against large vessels and vulnerable penile tissue. Morbidity results primarily from chronic friction and trauma as opposed to frank failure of the rods or their accessories.

Historical Background - Inflatable Penile Implants:

In the seventies, several new patents emerged. They described alternate ways of imparting rigidity to the penis. Most depended on inflatable cylinders inserted within the same cavities which had originally been used by the precedent rigid malleable devices. Most of the new systems depended in part on buildup of hydraulic fluid pressure from saline solutions or other physiologically compatible solutions stored within reservoirs implanted in the abdomen. The systems required implantable pumps, valves and tubing. They were significantly more complex and required different surgical approaches than the original malleable prostheses. The fluid handling system was more invasive and parts were scattered over the lower abdomen and the perineal area. Further complexities arose from the need to adjust and customize the devices to individual users. This required splicing of the fluid handling system. Implantation procedures added more complexities because of the requirements to pass fluid conduits from the main cylinders to the lower abdomen. The products seemed more attractive from the theoretical viewpoint. They were perceived as more ‘physiologic’. The erectile mechanism based on hydraulic pressure allowed collapse of the device when erectile function was not required.

This perceived advantage of the inflatable implants overshadowed their severe limitations and the complexity that the product entrained. It also overshadowed surgical aspects of implantation and the extreme difficulty in safe repair or removal of failed implants. Failure to recognize these aspects aided promotion and the products attracted immediate public and media attention. This led to rapid popularization of the penile implant in North America. As use increased, public and professional acceptance followed. Third party insurers and agencies responsible for health care of military personnel accepted the procedures more widely. Psychological criteria became a common basis for implantation. Dysfunction criteria were also relaxed and many users deemed to have residual erectile function were encompassed within the cohort. This led to further use of the technology in younger individuals with life expectancies that greatly exceeded the service life of the devices. Conversely, complications and functional failures of the systems which occurred in rapidly rising numbers did not receive significant publicity in the media and in the professional literature.

By the late-eighties, the inflatable penile implant nevertheless dominated the market and the malleable prostheses had become minority products. At least four major manufacturers were active in the field; they distributed competing versions of such products throughout the late-seventies and eighties. At least three manufacturers are still active worldwide.

The Risks and Their Causes:

Early penile implants of all kinds used unfamiliar materials and assembly methods. Manufacturers active in the sector were frequently newcomers and had comparatively few products. Others were organizations created as separate divisions of larger firms engaged mostly in cosmetic surgery products. The penile implants were generally of poor design, marginal manufacturing quality and surgical aspects of their implantation were not thoroughly investigated.

The combined effects of poor product quality with unfamiliar surgical procedures enhanced early failures and encouraged intrasurgical improvisation. Users of malleable implants encountered failure of the rigidity-imparting elements through material fatigue. Although functionally serious, this problem did not lead to greatly enhanced risks. Such a situation did not develop for the inflatables.

Many basic surgical problems of these more complex systems remained unresolved until the late-eighties. In the nineties, design limitations became even more obvious when manufacturers encountered raw material supply problems and modified the products to accept alternate materials and technologies. Consequently, failures, replacements and complications continued at high levels and occurred more widely than when compared to other simple health care technologies.

Following the common difficulties encountered in the eighties, users encountered new and more serious adverse reactions than individuals who received the simpler malleable devices. The more invasive inflatable products also failed in different ways. Functional complications were encountered almost from the outset and infective sequelae also rose dramatically. Contamination of the fluid pathway, pump and valve failures, egress of fluid from the connecting parts, early fatigue perforation of the pressurizable elements as well as intractable infective episodes were reported in significant numbers.

Penile prostheses using pressurized fluids as erectile media provide limited service and are subject to numerous failure modes, some of which are obvious. Others are less easily understood and are correspondingly more dangerous. The items also incorporate severe mechanical risks to the surrounding tissue such as inflammation and trauma from friction and excoriation as well as microbiological risks that relate to the stagnant aqueous fluid within the fluid system.

Whereas the obvious mechanical problems such as hydraulic failure and pump dysfunction are well documented in medical literature, the late infection risks from perforated and colonized implants are not. Most commercial versions share the same attributes and problems. They use fundamentally the same materials. The implantation procedure is comparable for most variations of these implants as well.

Problems include leakage from various points in the fluid system as a result of material fatigue, a process which affects poorly manufactured silicone-based elastomers. Specifically, the penile cylinders perforate as a result of repeated inflation and collapse. They develop creases and connecting points in the hydraulic system can leak or fail outright through improper design, incorrect coupling procedures or product defects.

Leakage and functional failure (erectile dysfunction) are specifically mentioned in the Product Inserts; they are depicted as benign. However, the sequelae of failure through perforation of the systems are serious, insidious and not widely recognized. Even surgeons are not fluent with all of the mechanisms of injury. Loss of fluid path integrity of these systems (cylinder perforation or connector failure) is followed by ingress of proteinaceous matter and micro-organisms from biological fluids. Florid colonization of the hydraulic fluid ensue, usually without recognizable symptoms. However, when micro-organisms escape from the device, their innoculae can maintain the patient in an infective state. The closed space protects the organisms from antibiotics and attempts at testing or using the devices through inflation allows more innoculae to egress from the device thus exacerbating symptoms. As the device ages, perforations enlarge and more nutrients become available to the colonies. Eventually, the devices must be removed and surrounding tissue debrided in order to remove organisms embedded in the capsule.

Infective complications noted from records are consistent with progressive infective phenomena. They include blood-borne and urine-carried micro-organisms and retrograde renal infective processes. There is frequent involvement of the lower limbs. Biological entities involved are frequently nosocomial species which present immediate threats but which can be controlled with courses of antibiotics. Problems surrounding these dominant species are well documented but, on balance of probability, many other slower growing entities are not sought during routine cultures. Therefore they often generally escape detection.

Many records do not provide the identity of the prostheses or discuss its deployment. Analysis of the failure is rarely performed. Chronic infections involving implant sites are difficult to control and resolve. They tend to recur. The primary sites where infective phenomena were initiated are not easily uncovered after several months of delay with antibiotic treatments .

An Early Manufacturer of Commercial Penile Implants:

The American Medical Systems (AMS) corporation of Minnetonka, Minnesota was founded in the early-seventies. It was acquired in the late-seventies by Pfizer Pharmaceuticals as part of Pfizer's diversification into the medical device area. At that time, Pfizer acquired a presence in cardiac and urology implants; pre-existing corporations such as Shiley Medical as well as AMS became subsidiaries of Pfizer and remained active in these fields until their divestiture in the mid-eighties. Shiley Medical ultimately became part of Sorin, a foreign manufacturer of pacing equipment. AMS is presently an independent corporation still engaged in the manufacture of urology products such as impotence implants and urologic prosthetic systems. Their best known products are the penile implants, in particular the inflatable variants. In the eighties, adverse reactions and complications following the use of these products became more widely known and numerous lawsuits became public thus further enhancing the visibility of the parent corporation. This motivated the divestiture.

The AMS 700 System:

The most commonly used penile prostheses are variants of the basic AMS System 700. This is an array of separate parts sold as a kit, modified and assembled extemporaneously during the surgery. It requires the insertion of the two previously described cylinders within the penis as well as a fluid conveyance circuit which includes tubing and accessory components spliced together by the surgeon after selecting, assembling and cutting some of the components to the correct dimensions. Such hydraulic penile prosthetic systems can thus exist in many customized variations which make use of the same basic components arranged and implanted in different ways. The concept is amongst the oldest. It consists of two inflatable, fabric-reinforced tubular cylinders which receive fluid under moderate pressure from a pump and reservoir system implanted in the lower abdomen. The system is comparatively complex and convoluted, requiring tunneling under tissue to allow passage of reinforced tubing, specialized coupling connectors and other components of significant size which are all essential parts of the fluid conveyance loop. Absolute reliability and leak-free junctions are required to ensure long term function as well as safety. Movement from the user incidental to walking and bending cause the parts to stretch and readjust thus making the system susceptible to material fatigue, even when not used.

Fibrosis and healing in the vicinity of the parts cause remodeling of the surrounding tissue with hyperplasia. This type of tissue build-up which includes formation of pannus at points where the connectors and the tubing enter the blood path can enhance stress on the various parts. Distentions may trigger severance or decoupling of the fluid conveyance accessories. The pump and the valve(s) must be externally accessible and digitally activated; they are also subject to fibrosis, tissue remodeling and material fatigue. As the device requires significant hydraulic pressure of the working fluid, the valves and the pump have limited service life and ultimately become susceptible to retrograde flow leading to unpredictable deflation of the system towards the end of the device life cycle. This type of dysfunction, though obvious, is not easily differentiated from leakage of fluid from the system as opposed to valve failure.

Egress or leakage of the working fluid from perforations and defects in the system cause not only reduction in the maximum achievable pressure which may reflect an inability to bring the device to full erectile function but will also lead to retrograde flow of body fluids into the system. Grossly perforated or decoupled parts habitually allow ingrowth of pannus tissue occasionally causing partial or temporary restoration of the erectile function. Thus, loss of functionality, even if transient, can be a precursor sign of more severe complications. Ingress of blood and tissue into the fluid pathway inevitably leads to secondary colonization by microorganisms. A capsule forms around all parts and the space between the components and the tissue constitutes an open tract with an outlet into the blood path; it is therefore an idealized area for secondary, chronic infective phenomena. Fluid is conveyed to the two cylinders located within the penis via tubing segments interrupted by a control valve which allows elective deflation. The valve may lock; fluid release and flaccidity may no longer be easily achievable once the device is set in the erect position.

Of greatest concern are durability issues of the key prosthetic items such as the cylinders which are inserted as a pair into existing tubular spaces in the penis. These components inflate and deflate, kinking in the process as the objects fill and empty reversibly. Kinks and puckers forming within the cylinder walls lead first to porosity. Perforation with loss of pressure and leakage of the hydraulic fluid usually follows. Conversely, during low pressure which corresponds to the flaccid state, and with movement of the user, pulsatile cycles facilitate ingress of blood into the hydraulic fluid with subsequent denaturation of blood products and possible colonization. In the inflated condition, perforated cylinders may still achieve some rigidity and lock the penis in the erect position. However, decaying tissue and blood products will effuse back into the blood stream. Concurrently, the erection may not be sustained as deflation becomes more rapid with aging of the device. Thus, deflation during use can be an ambiguous symptom which may have both a dysfunctional as well as an infective risk component.

Whereas this type of product has been used for approximately twenty years with limited success, there is also significant morbidity, in particular in the late stage as leaks develop in the system and ultimately cause erectile failure and secondary systemic problems occasionally with severe intractable early infections. Early problems associated primarily with frank infective, inflammatory and ischemic problems are also widely reported. The devices have attracted concern from some parts of the medical community . Chronic tissue injury also surrounds the long term use of the devices. Such damages include mostly excoriative tissue damages from traumatic impact and friction against sensitive vascularized tissue, in some cases resulting in gross penetration of the cylinder into tissue. Bleeding, inflammation and overt infection as well as more serious problems such as frank erosion of the vascular compartments of the penile area into the urethral area with cross-flow of urine products into the blood stream, cylinder or tubing failure and dysfunction of the pump or valve are documented end-stage problems for many users.

More serious and possibly life threatening sequelae include infections and mechanical damage to the large blood vessels located in the lower abdomen. These irrigate the lower limbs and include the aorto-femoral bifurcation, a notoriously vulnerable and problem-riddled area for certain classes of individuals, specifically including diabetics. It is further noteworthy that diabetics form a significant fraction of the user cohorts as diabetes is a listed indication for impotence. In this context, engineering and anatomic issues are of particular importance.

Key parts of the prostheses, in particular the components intended to be deeply inset within the perineal area for stability, have not received the necessary attention. These components, termed "extender tips", have the ability to penetrate tissue because of their acute contact angles. They rapidly stimulate the formation of pannus and scar tissue. Secondary problems are created by inadequacies in the pump and fluid conveyance systems which may also become occluded with contractile tissue with time, possibly as a result of low grade chronic, infective processes.

The anatomic singularities of the male perineal area render the installed system prone to protected infective phenomena. The components create blind spaces, poorly irrigated interfaces between tissue and devices and open tracts. They offer a direct infective pathway to the bloodstream. Thus, the systems are ideally suited for inducing septicemic sequelae if the infective process is not controlled when noticed. From the functional point of view, the devices are poorly conceived with respect to the fluid pathway splicing system, some requiring antiquated direct ‘strangulation’ ligatures placed around tubing linked together by metal ferrules. Such ligatures penetrate the tubing and may eventually cut the tubing.

Finally, the cylinders abut directly on unprotected internal parts of the penile tissue, some of which is vascularized. Excoriation of tissue with fibrosis occurring behind the glans penis and hyperplasia of blood vessels may reduce blood flow to the point of stagnancy, ischemia is a concern especially when the devices are inflated for long periods of time. Similarly, hyperplasia of tissue and fibrosis of the area may reduce urine flow. Episodes of erosive wounds to the urinary system culminating in significant loss of blood, infective sequelae from perforation and inflammation-erosion of tissue contacting components of the devices have been encountered in large numbers. Such problems are not limited to the actual penile area but may also affect peripheral sites where pumps are inserted and where reservoirs are placed.