Bruce R. Gilbert, M.D.,Ph.D.
Clinical Assistant Professor of Surgery (Urology)
in SURGERY OF MALE INFERTILITY
edited by Marc Goldstein,M.D.
I - Introduction
Microsurgical instrumentation extends the surgeon's ability to handle small
structures atraumatically and to allow precise alignment of these structures.
Therefore, microsurgical equipment and instrumentation has always been a compromise
between the engineer's ability to satisfy the surgeon's needs and the availability
of technology to accomplish this goal. It was in 1922, that Dr. Nylen of the
University of Stockholm first used a low powered monocular microscope for surgery.
The addition of a slit lamp with an added light source and a support stand created
the first binocular operating microscope. Naturally this microscope was cumbersome
and difficult to use, and for the next 3 decades surgeon's continued to use
magnifying spectacles and loupes. It was not until the 1950's that engineering
advancements allowed introduction of a surgical microscope. The first operating
microscopes provided coaxial illumination, stereo observation, focusing and
magnification changes at one working distance. They also provided a stable and
maneuverable suspension over the surgical field. These advancements brought
about the rapid spread of the surgical microscope from Otology into other medical
disciplines, including Ophthalmology, Neurosurgery as well as plastic and reconstructive
surgery. These advancements also resulted in the development of an operating
microscope that provided a wide, stable and brightly illuminated field for microsurgery
(Figure 1).
In 1964, Ota performed the first successful extracorporeal repair of renal vessels
with the assistance of an operating microscope. Since that time, urologic applications
of microsurgery have included ureteral anastomoses, hypospadias repair, penile
revascularization, penile venous ligation, testicular autotransplantation, microsurgical
varicocele ligation, vasotomy/vasogram, vasovasostomy and vasoepididymostomy
together with creation of alloplastic spermatoceles and epididymal sperm aspiration(1).
With improvement in optical magnification, has come the need for the development
of instruments that differ markedly from those used by traditional surgeons.
These instruments must be produced with precise tolerances and be able to transduce
the relatively gross movements of the operating surgeon into the smooth, well-defined
and precise control as viewed through the operating microscope. This has also
required development of suture material and needles capable of atraumatically
approximating tissues.
In this chapter, we discuss microsurgical equipment and instrumentation, beginning
with an overview of the basic physics of optical magnification and then discussing
the state-of-the-art in loupes, operating microscopes and documentation systems.
This will be followed by an overview of microsurgical instrumentation and the
microsurgical suture material available today.
II Optical Magnification and Documentation Systems
A. The optical advantage - Physics/Physiology of optical magnification.
For any microsurgical application the optical magnification system must provide:
1. enlarged upright and non-reversed images of the operating field;
2. undistorted three dimensional images with good contrast and high resolution;
3. sufficient working distance between the surgical field and the microscope
body for the surgeon to work comfortably;
4. true color reproduction for precise detail recognition;
5. homogenous reflection free illumination;
6. ease of rotation around the axis of observation;
The basic components of the optical system of an operating microscope are shown
in Figure 2. This consists of the front lens or objective, a magnification
changer, the binocular tubes and eyepieces and the illumination source.
1. The objective lens - normally used in microsurgery, has a focal length
("f"), which ranges from 150-400 mm usually in steps of 25mm. This
distance is identical to the working distance (the distance from the objective
lens to the surgical field). The choice of the working distance oftentimes relates
to the height and build of the surgeon, as well as the size of the microscope
and design of the binocular tube. If the working distance is too short, the
surgeon has difficult manipulating instruments between the operating field and
the objective, a longer working distance forces the surgeon to tilt the microscope
or to work in an awkward position.
2. The magnification changer - Surgical microscopes are usually equipped
with one of two different types of magnification changers(2). The first, which
is the stepped or manual system, is based on the Galilean telescope. The Galilean
system consists of a convergent objective and a divergent eyepiece aligned in
opposition to each other.
In a three step system, one Galilean telescope system, (two lenses), is placed
in the path of the observation beam on a cylinder or turret. In order to change
the magnification factor, this cylinder rotates, changing the relative position
of the two lenses. A free passage position, (no lenses), with a magnification
factor of 1 is located between the lenses. Thus, this system provides two magnification
factors plus the free passage position, the "three steps". The five
step magnification changer includes an additional telescope system and two more
sets of lenses, providing four magnification factors and one free passage position.
The motorized or zoom system allows a continuous change of magnification without
any blackout. Two motorized lens systems move simultaneously along a linear
path that coincides with the optical beams and paths. The relative position
of the lenses in the linear path determines the magnification factor. The range
of magnification factors from highest to lowest depends on the microscope type
and is either 1:4 or 1:5.
The advantage of the step system is that is requires a minimum of space and
thus permits the overall height of the microscope to be kept small, and in turn,
allows the working distance to be maximized. The motorized zoom system has a
major disadvantage that as the zoom range increases, the construction height
of the instrument also increases, therefore decreasing the useable working distance.
3. Binocular tubes consist of a lens and prism system in each observation
beam path. The lens accepts the image from the magnification changer,
and the prism shifts the image to make it upright in order to accommodate the
observer's own eyes. Binocular tubes have focal lengths, ("f"), because
the lens of the tube acts like the objective in a telescope. Wide field binocular
tubes have a focal length of 170 mm (f=170). Binocular tubes are straight, inclined
or not inclinable. Straight tubes are parallel to the microscope access and
are used in procedures where the microscope body is tilted, such as ear surgery.
Inclined tubes are set at a 45 degree fixed angle to the axis of the microscope
and are used when the microscope remains in a vertical position, such as most
urologic procedures. Inclinable tubes are adjustable to any angle to the microscope
axis and are useful where freedom in positioning is a requirement.
4. Eyepieces - eyepieces magnify the image from the binocular tube lens
and determine the size of the field of view (by means of a field stop). Magnification
factor and the size of the field stop in millimeters is engraved on all wide
angle eyepieces. Eyepieces provide diopter adjustment so that eye glass wearers
can correct for refractive errors and work without glasses. In addition, most
manufacturers of operating microscopes provide an optical design whereby the
distance between the eyepiece and eyes is greater than 20 mm. This is termed
a high-eyepoint eyepiece (Figure 3). High-eyepoint eyepieces
can be used by eyeglass wearers, without any decrease in the field of view.
5. Magnification size of the field of view, illumination of the object, depth
of field - Magnification can be calculated by the formula given below, where
fb=focal length of the binocular tube fo=focal length of the objective, me=magnification
of the eyepiece, mf=magnification factor of the magnification changer.
Total magnification = M= { ( fb / fo ) x me } x mf
for example, with 10x eyepieces, binoculars of 170mm, an objective lens of f=200mm
and a magnification factor of 1.2, the total magnification would be:
Total magnification =M= { (170mm/200mm) x 10 } x 1.2 = 10.2 x
For wide field eyepieces the field of view (Fview) is given by the formulas:
(Fview) = 220/M
The ratio between the focal length of the binocular tube and the focal length
of the objective, not only determines the working distance and the total magnification
as given above, but also the size of the field of view, the illumination of
the object and the depth of field. The greater the focal length of the objective,
the smaller the magnification M and thus the greater will be both the visual
field and depth of field. However, the magnification obtainable and the illumination
of the object will be decreased. Conversely, the shorter the focal length of
the objective, the greater the magnification and thus the smaller will be the
both the available visual field and depth of field, however, there will be a
greater maximum magnification obtainable. Illumination in the object however,
decreases with magnification.
Lighting of the surgical field is an issue that involves both technical as well
as physiologic problems(3). Both of these problems are related to the size of
the operating field that needs to be illuminated together with the heat produced
by the illuminating source. The larger the size and the brighter the operating
field, the greater the intensity of the light source that is required and therefore
the greater the heat that needs to be dissipated. Placement of this power source
near the operating field, would require a ventilation system that would interfere
with sterility in the operating room. Therefore, fiberoptic cables have been
employed to deliver illumination to the operative field from a distant light
projector. Even this solution though is not perfect. This "cold light,"
is actually only slightly cooler than the same quantity of directly transmitted
light and therefore, attention needs to be directed towards heating of tissue
and it's drying out. Attempts to replace glass fibers by fluid conductors have
not yet been able to eliminate this problem. Repeated irrigation is advisable
in these cases.
Dual headed microscope - In order to have an assistant help during an
operation, it is necessary to provide another binocular tube for use by the
assistant for "face-to-face" urologic procedures. These are usually
positioned 180 degrees apart from each other, and through the use of an optical
beam splitter, allow use of both binocular tubes simultaneously, permitting
both surgeons to see the object in equal stereopsis and with equal brightness
and equal magnification.
Lasers and microsurgery - The precision of a surgical laser can only
be fully exploited if precise microscopic alignment exists. The physical link
between the two is a micromanipulator. The micromanipulator is physically attached
to the microscope and thorough a series of focusing lenses is steered to the
target tissue by an integrated mirror that the surgeon controls with a hand
control ('joystick'). Laser precision is made possible by synchronous focus
(termed parfocality), between the laser beam and image path of the microscope.
Optimal performance requires that the microscope be accurately focused on the
surgical field and that the focal distance of the microscope image beam and
laser beam be equal.
B. Magnifying spectacles (loops), provides the operating surgeon a simple
and less expensive means of taking advantage of optical magnification. There
are two basic optical systems that are employed, one being the Galilei
system and the other the Kepler system(3).
The Galilei system incorporates both a positive and negative lens. The total
thickness of the construction can be kept relatively thin and an upright and
laterally correct image is produced. However, the major disadvantage is that
the visual field is a function of the front lens which must be made increasingly
larger to provide an adequate field of view. This then incurs both weight and
space problems and magnification is limited to 2.5 to 3 times. Above this magnification
factor, the spectacles become too thick and heavy and the working distance too
small. These are usually the least expensive of magnifying spectacles.
The Kepler system employs two positive lenses and since the image is therefore
inverted in the process, optical inversion is necessary. This system is commonly
used in prismatic binoculars that use a complex system of roof prisms. However,
for spectacles these would be too large to be usable. Instead, direct vision
prisms are employed. Again, as in the Galilei system, magnification is limited
by the size constraints of the loops and with the Kepler system, depth of field
is small and therefore requires steadiness of the neck during lengthy operations
resulting in rapid fatigue.
Loops also do not provide a way of changing magnification, nor the ability to
photo-video the microsurgical procedure. In addition, due to size and weight
constraints, are limited to magnification of 2-8 times, however they do provide
a relatively inexpensive means of optical magnification.
Still and Video Documentation Systems
Documentation of microsurgical procedures has become commonplace. Most optical
instrumentation has incorporated fittings to add either a still (usually 35mm)
format or video (usually VHS or super VHS) capabilities. There are several considerations
that will insure effortless and unobtrusive documentation. Due to cost considerations
these are often a "wish list" rather then requirements. Control of
the camera should be available to the surgeon as well as an assistant. Foot
controls for recording and "instant replay" are desirable. The camera
must be "par focal" as discussed earlier. Repeated visual checks while
recording insures "in focus" images. The availability of an automatic
adjustment to insure par focality would be a great time saver. Usually additional
lighting is required in part due to the beam splitter needed to divert the image
to both the optical recorder as well as the eyepieces. Therefore, irrigation
of the field should be done frequently to prevent drying of the tissue.
Microsurgical suture materials:
Microsurgical sutures are composed of a needle (Figure 4 and Figure 5)
and suture strand. The needles used for vasal anastomoses have been designed
to accommodate the specific requirements at each level of the anastomosis. For
the inner mucosal alignment a double armed 2.5cm suture is used. The point
has precision cutting edges to facilitate penetration of the tough muscularis
layers without undo drag. The blade which is the transition between the
needle point and is designed to minimized tenting of the tissues. The body
is bi-curved (950/1070) and 70 microns in diameter. The bi-curved needle simplifies
inside-out placement of sutures while providing short, deep bites and immediate
exit which reduces the risk of backwall involvement. The needle is then swaged
to a black monofilament 10-0 suture strand (Sharpoint AA-2492, Ethicon D6890).
The suture we use for the seromuscular and adventitial layer a single strand
9-0 black monofilament suture strand (5-6 cm in length; Sharpoint AA-1825, Ethicon
Vas100-4) is swaged to a 100 micron vas cutting needle(4) (Figure 6).
Microsurgical instrumentation
The choice of instruments used for microsurgery is as critical as the experience
of the microsurgeon. These instruments are often controlled by a rolling movement
provided by pressure applied between the distal phalanges of the thumb and second
or third fingers. Therefore, the surfaces of these should be designed to prevent
slip. The instrument itself should be made of a non-glare material and should
provide precise control over closure of the perfectly aligned tips. General
specifications of each of these instruments will be presented here, while more
specific recommendations will be presented in later chapters.
Grasping/Dissecting Instruments
Grasping/dissecting instruments include forceps, needle holders, coagulators
and clamps. This group includes a wide array of instruments that often have
multiple uses. Length of the handle is primarily one of surgical preference.
However, the longer the handle the more tiring it is to hold for prolonged periods
of time. To limit the effect of fatigue, several manufacturers have counterbalanced
their instruments to reduce the weight of the tip of the instrument and therefore
produce less fatigue.
Forceps can have straight tips, curved tips, tapered tips and grasping
tips (Figure 7). However, they should be non-toothed (grasping forceps
may be an exemption), have precisely aligned tips, be made of a non-glare material
and have a graded closure. They are often used for grasping of tissue, dissection
and dilation of tubular structures.
Needle holders are used often for dissection around small vessels. This
is due to their finely rounded tips that protect the vessel from injury (Figure
8). When used for placement of microsutures they can be either locking or
non-locking. The locking variety allows for loading and holding of a suture
in preparation for its use. This is particularly useful for microsurgeons operating
without trained assistants. Needle holders usually have curved tips with flat
surfaces to securely grasp the suture. Their handles are rounded and are serrated
to provide a non-slip surface for precise control.
Coagulators are required to stop bleeding from the small arterioles and
allow for visualization of small structures. Only bipolar coagulation should
be used to limit coagulation to a precise structure. Unipolar coagulation produces
a wide area of coagulation due to the ground current produced (Figure 9
). A physiologic saline solution should be used during coagulation to limit
the build up of tissue debris on the bipolar tips as well as to rapidly cool
surrounding tissue to prevent injury by heat conduction. The fine tips of the
coagulator are needed for accurate coagulation and are easily damaged. These
fine tips should be checked prior to use. A backup pair should be readily available.
Clamps are used to approximate tubular structures and allow for a precise,
leak-proof and tension free anastomosis to be made. They are essentially composed
of two microvascular clamps mounted on an adjustable bar. The modification we
find most useful has small, blunted posts mounted on the concave surface of
the clamp(5). This eliminates slippage of the tissue during anastomosis (Figure
10).
Scissors
Scissors are used both for cutting of tissues and sutures as well as dissection.
When used for cutting the tips are usually pointed (Figure 11a). Care
must be taken to prevent injury to surrounding structures. A scissor used for
cutting sutures should be so identified and not used for tissue. Scissors use
for dissection should have blunted tips (Figure 11b). When used for dissection
their handles are rounded and are serrated to provide a non-slip surface for
precise control. When used for cutting a flat handled scissor provides the best
control in a single plane. Curved tips are useful when cutting fascia which
overlies delicate structures.
Accessory Items for Microsurgery
Useful options for urologic microsurgery include irrigators, operating platforms,
background materials and microsponges. Irrigators are necessary to provide
an optically clear field. The irrigating solution used is most commonly a physiological
saline (we prefer lactated ringers). This solution is drawn up into a 10 cc
syringe to which an angiocath tip 21ga or smaller is attached. At least two
of these irrigators are kept ready on the field. An operating platform
is useful when approximating tubular structures (e.g., vasovasostomy, vasoepididymostomy).
We usually use a sterile tongue depressor which has been snugly placed inside
a penrose drain of the same length. Background materials are useful in providing
a contrast between the operating platform and the tissues. We commonly use a
blue background material placed between the tongue depressor and the translucent
penrose drain which covers it. Microsponges are often made in the shape
of a triangular spear and extremely useful for absorbing fluids and removing
small clots.
Acknowledgement: The author would like to thank Mr. Peter Horenz of Carl
Zeiss, Inc., Thornwood,NY for reviewing the manuscript and his many helpful
suggestions.
REFERENCES:
1. Wagenknecht L. Microsurgery in Urology.New York: Thieme, Inc., 1985
2. Horenz P. Personal Comunication., Carl Zeiss, Inc., 1993:
3. Forster B. Optical magnification and reproduction sytems. In: Wagenknecht
L, ed. Microsurgery in Urology. New York: Thieme Inc., 1985: 2-16.
4. Gilbert BR, Goldstein M. New directions in male reproductive microsurgery.
Microsurgery 1988;9(4):281-5.
5. Goldstein M. Microspike approximator for vasovasostomy. J Urol 1985;134(1):74.