Instrumentation



Instrumentation


RICHARD D. FERKEL



Arthroscopy of the ankle evolved from the principles of knee arthroscopy, and initially the instrumentation used for the knee was applied to the ankle. As expertise and experience with ankle arthroscopy increased, it became apparent that special, smaller instruments were necessary to visualize the ankle and foot joint entirely and operate through a smaller space. In addition, because of the architecture of the ankle and foot joint, the diminished working area, and the tightness of the joints, some form of distraction became necessary. Since 1990, instrumentation for the ankle and foot has significantly improved as an “extremity or small-joint” system has evolved. The dynamic nature of arthroscopy necessitates constant improvements that will continue to allow this field to grow.


IRRIGATION

Different fluids can be used for arthroscopic irrigation during ankle and foot arthroscopy. Lactated Ringer’s is the most commonly used fluid because it is physiologically compatible with articular cartilage and is rapidly reabsorbed if extravasated from the joint.1 Glycine and normal saline can also be used, and an experimental fluid, Synovisol (Baxter), was developed to use with or without electrosurgery and has the appropriate pH and osmolality for the intra-articular structures2, 3 (Table 3-1). Today, lactated Ringer’s is used in the ankle, except that glycine or sorbitol is preferred when electrosurgery or RF (radiofrequency) is needed. Glycine or sorbitol should be washed out of the joint with lactated Ringer’s prior to wound closure.


Gravity

Inflow can be accomplished by gravity or by the use of an arthroscopic pumping device. Gravity inflow is usually adequate when the fluid is introduced through a separate cannula, but may be inadequate if the fluid is introduced through the arthroscope sheath because the flow volume and rate may not be high enough (i.e., using a 1.9-mm arthroscope with a 2.2-mm sheath or with a 2.7-mm arthroscope with a 2.9-mm sheath) to keep up with the evacuation provided by suction instruments such as a shaver system or 2.5-mm suction punch. Using gravity inflow through a dedicated inflow cannula with a 3-mm inner diameter (ID) at a bag height of 3 feet above the joint, a flow rate of 750 mL/min is produced (Fig. 3-1A). In contrast, when using the same cannula and gravity height as above, but with a 2.7-mm arthroscope in the cannula, the flow rate is reduced to 75 mL/min. Using a wider cannula (3.7 mm ID) with the same 2.7-mm arthroscope produces a much higher rate of 500 mL/min (Fig. 3-1B). For comparison, a dedicated 4.5-mm inflow cannula with no scope yields 924 mL/min; a 4-mm arthroscope with a standard 4.5-mm diagnostic (high-flow) cannula yields 110 mL/min. A 4.0-mm arthroscope with a 4.5-mm operative cannula and irrigation extender yields 67 mL/min.








Table 3-1. Arthroscopic Solutions










































Approximate PH


Approximate MOSM/L


Compatibility with Electrosurgery


Tissue Toxicity


Synovisol


5.0


282


Nonconductive


Minimal


Ringer lactate


6.5


273


Conductive


Moderate


0.9% Saline


5.5


308


Conductive


Moderate


Glycine


6.0


200


Nonconductive


Minimal


Water


6.8


2


Nonconductive


Severe


From Esch JC, Baker CL Jr. Arthroscopic surgery: the shoulder and elbow. Philadelphia, PA: JB Lippincott, 1993:38.



Preferred Method

We prefer to inflow through a dedicated 2.9-mm cannula with an infusion adapter (Christmas tree) using a separate portal. It connects to the fluid tubing by a “Christmas tree” (Fig. 3-2A, B).


Arthroscopy Pumps

Several types of arthroscopy fluid management systems are available. They operate through the use of a pumping device or gas to pressurize an irrigating fluid into the joint. All systems
have regulating devices to prevent over- or underdistention, but each works by a different mechanism (Fig. 3-3A, B).






FIGURE 3-1. Inflow rates. (A) Using a cannula with a 3-mm interior diameter, at a 22-18.bag height of 3 feet above the joint, a flow rate of 750 mL/min is produced. (B) Using a cannula with a 3.7-mm interior diameter, with a 2.7-mm scope inside, yields a flow of 500 mL/min at the same bag height. (Illustration by Susan Brust.)

The operating surgeon must exercise extreme caution when using an infusion pump device during arthroscopy. The disadvantages of these systems include mechanical issues, the need for specialized and expensive equipment and tubing, and the need for a team familiar with the operation of the device. Particularly in the foot and ankle, extravasation of fluid could lead to a compartment problem with subsequent disastrous results (Fig. 3-4).






FIGURE 3-2. Fluid tubing connection. (A) Christmas tree attaches to 2.9-mm cannula (without side port). (B) Separate inflow through the posterolateral portal with Christmas tree attachment in an operative patient.






FIGURE 3-3. Arthroscopic pumps. (A) The ConMed arthroscopic pump requires a separate sensor for use in the ankle. (B) The Dyonics pump (Smith and Nephew Dyonics, Inc., Andover, MA) allows inflow through the arthroscopic sheath and is connected to the suction system.


ARTHROSCOPES

Over the last 30 years, the optical qualities of arthroscopes have improved significantly. The Hopkins rod-lens system continues to provide the best picture quality. Initially, the 4.0-mm knee arthroscope was used in the ankle, but in some cases, it was too large in diameter and had too long a lever arm and too large a sheath to allow complete visualization in the ankle without increased risk of articular cartilage scuffing. Moreover, the 4.0-mm arthroscope may be too large to visualize the small spaces along the gutters and posterior aspect of the ankle and to
look into the subtalar and forefoot joints. A short 4.0-mm arthroscope was developed to accommodate the more superficial ankle joint without losing the picture clarity of the longer arthroscope (see Fig. 1-19).






FIGURE 3-4. When an arthroscopic pump device is used in ankle arthroscopy, extreme caution is needed to prevent extravasation of fluid, which can lead to compartment problems. (Copyright, Richard D. Ferkel, MD.)






FIGURE 3-5. Small-joint arthroscopes with interchangeable cannulae are helpful in ankle and foot arthroscopy. A 1.9-mm 30° oblique arthroscope is pictured on top, a 2.7-mm 30° oblique arthroscope below.


Construction and Manipulation

More recently, the rod-lens arthroscope has been produced in 1.9-mm, 2.3-mm, 2.5-mm, and 2.7-mm diameters (Fig. 3-5). These smaller arthroscopes are available in short versions (˜67 mm), having the advantages of a shorter lever arm, excellent picture quality, easy maneuverability, and interchangeable cannulae. The shaft of an arthroscope must be only 67 mm long for use in ankle and foot arthroscopy. However, as the arthroscopes have become smaller and shorter, they have become correspondingly more fragile. Today, the picture quality of the smaller arthroscopes is equivalent to that of the larger versions and is matched to the quality of the latest high-definition or ultra high-definition camera systems.


Field of View

There are two dimensions to the field of view4 (Fig. 3-6). The apparent field of view is the diameter seen at the ocular end of the arthroscope and enhanced by magnification through the video coupler device. The closeness of the arthroscope to the object influences the surgeon’s perception of the field of view. The actual field of view is a measured angle of view the arthroscope produces. This angle varies 90° to 115° for current (wide angle) 4.0-mm arthroscopes. In contrast, the 2.7-mm wide-angle arthroscope has a field of view of 75° to 90°. The term “wide-angle scope” refers to the actual angular field of view rather than the apparent field of view.


Inclination of View

The inclination of view is the angle of projection at the objective end (distal) of the arthroscope (Fig. 3-7). The 30°
view, the most practical and the most commonly used, permits excellent visualization within the ankle and foot, particularly when a wide-angle lens is used. The 70° small-joint arthroscope allows the surgeon to see around corners but requires some experience because it is used less commonly. It is particularly helpful in seeing over the medial and lateral domes of the talus, looking into the gutters and evaluating certain osteochondral lesions of the talus and tibia (Fig. 3-8).






FIGURE 3-6. The apparent field of view is determined by the closeness of the arthroscope to the object. The close-up (left) shows a smaller actual view than the more distant view (right). (Illustration by Susan Brust.)


Clarity

Most current arthroscopes have a zero-to-infinity working distance and provide a clear image whether the tissue is close to the lens of the arthroscope or further away. A focusing ring permits fine adjustment to the picture quality. Once the focus is set, rarely are adjustments necessary.






FIGURE 3-7. The angle of inclination is 0°, 30°, or 70° relative to the arthroscope axis. The angular field-of-view cone is oriented along the axis of the angle of inclination. (From Esch JC, Baker CL Jr. Arthroscopic surgery: the shoulder and elbow. Philadelphia, PA: JB Lippincott, 1993:38.)


Arthroscopic Movement

A careful diagnostic examination is a composite of multiple images obtained by moving the arthroscope in different positions and using the arthroscope’s rotation ability and angle of inclination.


Pistoning

The forward and backward movement of the arthroscope is called “pistoning.” Pistoning allows the surgeon to move closer or further away to visualize one particular area or to obtain a panorama of a larger field.


Angulation

Angulation is a sweeping motion that moves the arthroscope in a horizontal or vertical plane. This movement can scratch the fragile articular surfaces and must be performed gently, except in the case where sapphire lenses are used in the arthroscopes. Sapphire is extremely hard optical glass that is resistant to scratching.


Rotation

Rotation is the most valuable movement in arthroscopy. Using a 30° instead of a 0° arthroscope permits a wider view of the ankle and foot joints. Rotation of the 30° arthroscope’s field of view enhances arthroscopic viewing by creating overlapping circular images. With the 70° arthroscope, rotation occurs around a central blind (see Fig. 3-8).


Cannulae

The arthroscope is introduced into the joint by means of a cannula or sheath, which should be 1 to 2 mm shorter than the arthroscope when fully engaged. The tip of the cannula is angled in a manner to accommodate the angle of the scope lens. The proximal end of the sheath should have a quick and secure connecting mechanism to accept a trochar or arthroscope. This allows easy insertion and removal of the arthroscope from the sheath during
surgery. Sheaths are available with and without side ports for fluid flow or suction (Fig. 3-9). The amount of fluid that can be introduced through the sheath depends on the size of the sheath and the pressure applied to the fluid (see Fig. 3-1).






FIGURE 3-8. Rotating the arthroscope’s field of view enhances arthroscopic viewing by creating overlapping circular images with a 30° arthroscope (center). With a 0° arthroscope (top), the field of view is unchanged with rotation. With a 70° arthroscope (bottom), rotation occurs around a central blind spot. (Illustration by Susan Brust.)

The arthroscopic sheaths should be interchangeable so that the arthroscope and instruments (shaver blades) can be easily placed through any of the portals desired without repeated instrumentation and subsequent soft tissue trauma. “Switching sticks” that are smaller in diameter than the cannulae being used should also be available and are particularly useful if the cannula comes out of the joint inadvertently or if the surgeon needs to switch from a cannula with a side port to one without. For systems without interchangeable cannulae, plastic disposable cannulae can be used to allow exchanges of instruments through a given portal. However, the small size of the foot and ankle joints does not lend itself well to the use of small disposable cannulae.







FIGURE 3-9. Arthroscopic cannulae are available in sizes 1.9 and 2.7 mm, with and without side ports.


LIGHT SOURCES/LIGHT GUIDES

An adequate light source is just as critical to the procedure as the arthroscope. Various types of lamps have been used, including incandescent, quartz, halogen, tungsten, xenon, and most recently, LED (light-emitting diode). The differences between lamps are the light temperature, the lumen output, and operational conditions. In the past, most light sources were metal halide or halogen. Xenon sources, because of their similarity to sunlight, color temperature, longevity of use, and the quick-start cycle when turned off and then on again, have been the gold standard for use in the operating room (Fig. 3-10).






FIGURE 3-10. Xenon light source box.

However, energy-saving LED (light emitting diode) technology is now replacing xenon light boxes. Xenon bulbs last ˜30 hours, while the LED lamps last ˜30,000 hours.

To transmit the light from the light source to the distal end of the arthroscope, a light guide is interfaced between the light source and the arthroscope. Light guides or cords consist of fiberoptic bundles for light transmission. Fiberoptic guides are normally very flexible and easy to manipulate in the sterile field, but damage to individual fibers can create inadequate light transmission.


DISTRACTION DEVICES

Visualization of the ankle, subtalar joint, and forefoot areas can be significantly improved by the use of a distraction device. The distractor is used to increase the space between the tibia and the talus. Without distraction, certain areas of the ankle, such as the central and posterior tibial plafond, talar dome, the posterior inferior tibiofibular ligament (PITFL), and transverse tibiofibular ligament (TTFL), are poorly seen. Distraction methods can be noninvasive or invasive.


Noninvasive

Noninvasive techniques include manual distraction and gravity distraction, which are “uncontrolled” methods. Although these methods require no specific equipment, they are often inadequate for complete visualization and operative arthroscopy. Other noninvasive methods, such as the modified clove-hitch knot around the ankle, can be termed “semicontrolled”5 (see Figs. 1-20 and 3-11). This method is inexpensive but may be inadequate for good distraction; also, the degree of force and the duration of distraction are hard to monitor. The third type of noninvasive distraction, termed “controlled,” involves the use of prefabricated sterile straps that hook around the front of the foot and the back of the heel and are attached to an outrigger device in which a distraction force is generated (Fig. 3-12A). Countertraction is applied by a nonsterile thigh support (Fig. 3-12B, discussed later).

A fracture table can also perform this type of distraction, but it is not necessary with today’s soft tissue distraction devices. Other devices are available that allow this type of distraction while the patient’s knee is bent at 90°.

Some of these devices permit the amount of pressure and force to be monitored and maintained mechanically. Presently, this is the most common type of distraction used for foot and ankle arthroscopy.


Invasive

Invasive distractors use pins in the tibia and talus or calcaneus to provide mechanical distraction. A “controlled” system usually has a strain gauge to measure the amount of force and permit some degree of freedom within the
ankle joint (Fig. 3-13A). The disadvantages of these systems include the need to insert pins and the risk of damage to the neurovascular structures, infection, and fracture. However, they allow large amounts of distraction force to be applied across the joint in a controlled manner. In the past, a “multimode” distraction system (Acufex) was developed to allow both invasive and noninvasive distraction to be applied through the same device.6 This apparatus allowed the surgeon to start with a noninvasive technique and progress to invasive techniques only if adequate distraction and visualization were not obtained (see Fig. 3-13B). Presently, invasive distraction is rarely used.






FIGURE 3-11. Noninvasive distraction loop. (Illustration by Susan Brust.)






FIGURE 3-12. Noninvasive distraction. (A) Sterile strap around right ankle. (B) Standard setup for noninvasive distraction in the supine position. Note the thigh support surrounding the tourniquet with flexion of the hip and knee. A commercial strap provides good padding over the dorsum and the posterior aspects of the ankle and is attached to a distraction device that joins the table sterilely. (C) Intraoperative view of setup.


Preferred Method

We use a noninvasive distraction device with a disposable strap on every ankle and subtalar arthroscopy.

The patient is usually done under general anesthesia with a popliteal block. The patient is “paralyzed” to increase distraction. Maximum distraction is initially applied, and over time more distraction can be obtained. Maximum distraction is done for no more than 1 hour, and then the distractor is clicked back (or relaxed) one notch. This maneuver is also helpful to relax the anterior capsule and see the anterior distal tibia and medial and lateral gutters more easily.

In the great toe and lesser toes, noninvasive distraction is performed in a semicontrolled manner using a toe trap attached to a rope-and-pulley system. This is discussed
further in Chapter 16. Some type of distraction is required in most arthroscopy cases of the foot and ankle.






FIGURE 3-13. (A) Invasive distraction device applied to the lateral aspect of the distal tibia and calcaneus, with a strain gauge to monitor distraction force. (B) The multimode distraction unit comes in a sterilization tray. It can be used with invasive or noninvasive distraction.

Contraindications to the use of noninvasive distraction include impaired circulatory status, diabetes, certain generalized medical conditions, and ankle edema or fragile skin conditions. Invasive skeletal distraction is contraindicated with localized or generalized infection, osteopenia, open physis, ligamentous laxity, and active reflex sympathetic dystrophy and in high-performance athletes who must return to their sport quickly.


VIDEO STANDARDS AND FORMATS



Video Formats (Standard Definition)

Formats are the manner in which electronic signals produced by a camera carry their color and brightness information to an accessory device for display or manipulation. Analogs (composite, Y-C [S-VHS], RGB, and HD [HD-SDI, HD-DVI, and YPrPb]) are terms describing various video formats.

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Sep 25, 2018 | Posted by in RHEUMATOLOGY | Comments Off on Instrumentation
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