Penile Prostheses

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Dr. Chris Steidle - Northeast Indiana Urology

Penile Prostheses (Implants)

The concept of the penile prosthesis dates back to early times when
it was noticed that several species of animals had what was termed as
an os penis or biaculum. This is a cartilaginous support noted to
keep the penis erect. The first penile prosthesis was actually a rib
graft implanted into the corporal body.

The recent history of penile prosthesis dates back to 1950, when Dr.
Scardino implanted the first synthetic material into the penis.
Penile implants improved dramatically with subsequent work of many
investigators, and penile implant surgery has progressed to a very
high level.

The indications and contraindications for penile implant surgery
include vascular disease, diabetes, bladder or prostate cancer
surgery or for benign prostate disease, Peyronie's disease,
neurologic disease, hypogonadism, pelvic fractures and impotence
related to many medical diseases including chronic renal
disease, alcoholism, multiple sclerosis, genital trauma,
Parkinsonism, drug therapy.

Some of the relative contraindications for penile implant include a
poorly controlled diabetic, mostly because
of the patient's high susceptibility to infection and significant
symptoms of bladder outlet obstruction because a prosthesis
can cause a relative increase in the
outflow obstruction and, thereby, produce urinary retention.

When choosing a penile prosthesis, it is important to recognize
the major categories. These include:

1) rigid, semi-rigid and malleable rods, which produce varying
degrees of rigidity and

2) inflatable prostheses which include two types; a) the
multi-component inflatable prosthesis, and b) the self
contained inflatable prosthesis. The main objective is to leave the
patient with a penis that when sexual intercourse is desired it is
achieved with no complications and with a penis that satisfies both
him and his partner.

There is no single
penile prosthesis that is best for all patients. It is, therefore,
imperative that the urologist sit down and very carefully review
the risks, benefits, and drawbacks to each of the different types.

When discussing the semi rigid prosthesis, the balance
sheet includes an erection sufficient
for penetration. This is termed axial rigidity in the urologic
spectrum and means the amount of torque that can be placed
on the penis. Most of the rigid prostheses are associated with
a low mechanical failure rate because there really are no moving
parts and a fairly simplistic implantation is possible. The down side
is that
they produce an erection that may be noticeably unsightly, and
because these are the
most obstructing
of the devices can interfere with urination. Also prostate surgery if
needed in the future can
be very difficult in this situation. The rigid protheses is however
good for men with poor
hand mobility, who are
relatively elderly, or who do not wish to have the increased
risk of malfunction because there are more moving parts.

The one-piece inflatable penile prosthesis offers a compromise
between the multi-component inflatable and the semi-rigid device.
The downside to this device is that it can sometimes be difficult
to manipulate. It doesn't get as erect as the rigid and it doesn't
deflate as much as the multi-component inflatable. Additionally,
this device is very limited to the "average size penis,"
and if the patient has an extremely long penis is not an
adequate device.

The multi-component inflatable
prosthesis is what we term the "Cadillac" device.
It gives the best appearance when erect and is the softest when
deflated. It is probably the most popular and there are several major
manufacturers including
American Medical Systems and Mentor.

Several penile prostheses are no longer in
vogue and do not have a place in modern implant surgery.

The small
carrying prosthesis introduced in 1973 was available in numerous
sizes and lengths was a reasonable device, but really failed
to produce the axial rigidity necessary for intercourse and was
supplanted by better models.

The Jones Prosthesis was
a malleable rod consisting of an outer silicone
shell and silver wires and a twisted configuration that allowed
some degree of torquing and thus causes some loss of axial
rigidity. This was implanted with a trimable version to ensure
adequate sizing.
American Medical Systems introduced the malleable
prosthesis. This gives a very adequate erection, but one that
can be very unsightly. That the normal erection
is a hydraulic event was really the rationale behind the
inflatable device. It has three pieces including a reservoir to
store the fluid, cylinders, and a pump which is placed in the
scrotum. The pump transfers fluid from the reservoir into
the cylinders, thus creating erection and when one desires to
end the erection this process is reversed with a releaser deflate
valve.

Another American Medical Systems product is the controlled expansion
inflatable penile prosthesis which increases the actual
rigidity. It has reinforced non-kinking tubing, revised pump,
and a rear-tip system to allow adequate sizing. Mentor also
has an inflatable prostheses with both a two-piece and three-piece
inflatable prostheses.

The type of surgery used for the implant is generally left
to the surgeon's experience and type of device, but can include:

1) a perineal approach which is under the scrotum;
2) a penoscrotal
approach which is at the base of the penis on top of the scrotum,
3) the protheses may be placed in the penile shaft, or
4) an infrapubic
incision, which is an incision above the penis.

There are advantages
and disadvantages to each device, and the most
important part of penile prosthesis includes the proper selection
of length and diameter to fit the corpus cavernosum, general dilation
of the corporal body to avoid perforation proximally, with meticulous
attention to detail to avoid infections, including
preoperative preparation, intraoperative antibiotics, and copious
irrigation during the procedure.
Complications of the penile implant include infections, which can be
disastrous and treating an infected prosthesis
actually can exceed the cost of the original prosthetic implant.
Attempts to avoid infection include use of a surgical
bubble system to prevent particles and bacteria from getting access
to the device.

Other complications include perforation of the
corporal body which is the area where the prosthesis is held which
can cause migration of the device. Management for this includes
creating a Dacron graft to prevent migration. Perforation into the
urethra or glans penis can be disastrous and any perforation
to a potentially infected area, such as the urethra, should require
termination of the procedure.

Other problems include tubing kinks, fluid leaks, aneurysm,
dilatation of the cylinders, breakage of the wire, the Silicone
spillage, loss of rigidity to the prosthesis, erosion of the
reservoir,
spontaneous deflation, spontaneous inflation, penile curvature,
which is a variant of Peyronie's disease, pump or pump reservoir
migration, phimosis, paraphimosis, things that go along with
circumcisions.
All of these can be tremendous problems during the placement of
a penile implant.