Interventional Techniques

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Chapter 9 Interventional Techniques

imageAdditional videos for this topic are available online at www.expertconsult.com. Examples of diagnostic elbow ultrasound reports are available online at www.expertconsult.com (see eBox 9-1 and 9-2).

Ultrasound-guided percutaneous procedures have several advantages, including real-time assessment and guidance, in which continuous visualization of a needle is possible throughout the procedure.1,2 With ultrasound guidance, a needle can be precisely placed in a target while avoiding important structures, such as nerves and blood vessels. This allows very high accuracy and low complication rate, especially compared with blind needle placement. Compared with other imaging-guided techniques like computed tomography (CT), ultrasound is especially effective when a target is superficial. In addition, procedure time is typically reduced compared with CT, and ultrasound is not limited to standard imaging planes. Other intrinsic advantages of ultrasound are not specifically related to intervention but include availability, portability, lack of ionizing radiation, and relatively low cost.

This chapter first reviews technical considerations when performing an ultrasound-guided procedure. This is followed by topics related to joint, bursal, tendon sheath, tendon, and miscellaneous procedures. Because the procedure that is completed using ultrasound guidance can vary widely (diagnostic or therapeutic injection versus aspiration), the ultrasound guidance aspect is emphasized here, rather than the efficacy of the specific procedure.3,4 Regardless of the procedure, if one can identify the target and the needle with ultrasound, and understand what structures lie in the projected needle path, ultrasound can offer an accurate and safe method for needle guidance for essentially any procedure. Knowledge of anatomy and of normal and abnormal sonographic findings is essential to accurately identify a target. Of note, the photographs in this chapter that show needle and transducer placement are for illustrative purposes only, in that sterile technique and needles were not used.

Technical Considerations

Needle Guidance Overview

When performing a percutaneous needle procedure using ultrasound guidance, there are several techniques that can be used. Generally speaking, ultrasound-guided procedures can be separated into indirect and direct approaches. With the indirect approach, ultrasound is used to identify a target and to determine the depth, and then the skin directly overlying the target is marked. The transducer is removed, and the needle is directed perpendicular to the skin into the target. This approach may work for large superficial targets but is significantly limited because the needle is never directly visualized in the target, and real-time assessment during the procedure is not possible. The direct approach is preferred over the indirect approach in that the needle is identified within the target, which ensures a much higher accuracy and lower complication rate.

There are several techniques that may be employed when using the direct approach, including needle guide or freehand techniques. The one option that is not routinely used for musculoskeletal procedures employs a needle guide that is physically attached to the ultrasound transducer. Because most musculoskeletal procedures are relatively superficial, and given the extra steps required when using a needle guide, a freehand approach is favored. When using the freehand direct approach, there are two methods to direct a needle relative to the transducer and sound beam: in plane and out of plane. With the in-plane approach, the needle is directed under the long axis of the transducer and sound beam in plane, and the entire needle, including its tip, is visible at all times during the procedure (Fig. 9-1) (Video 9-1)image. This enables real-time correction of angle and depth while the needle is advanced. The in-plane approach is the preferred method in most situations because continual visualization of the entire needle, including the needle tip and target, minimizes complications and maximizes accuracy.

With the out-of-plane approach, the needle is passed perpendicular to the transducer so that the needle passes through the plane of the sound beam (Fig. 9-2) (Video 9-2)image. The disadvantage with this approach is that only a short segment of the needle is seen where the needle passes through the sound beam plane. When using the out-of-plane approach, the needle entrance site is centered over the target, and the needle enters from the side of the transducer (see Fig. 9-12). When inserting the needle, there is some trial and error required as the needle passes through the sound beam, is retracted, and then repeatedly redirected, typically deeper, to eventually get to the target. Another disadvantage is that one cannot determine what segment of the needle is represented on the ultrasound image, the shaft or tip of the needle, because they look exactly the same as a single bright echo with reverberation artifact. Although the in-plane approach is preferred in most situations, the out-of-plane approach is favored in situations in which the target is very superficial, such as guiding a needle into small joints of the hand and foot. Regardless of the in-plane or out-of-plane approach, once the needle is seen in the target, it is critical that the transducer is turned 90 degrees to confirm accurate location of the needle tip. It is wise to become comfortable with both in-plane and out-of-plane direct methods of needle guidance.

Approach, Transducer and Needle Selection, and Ergonomics

The first step in planning an ultrasound-guided procedure (after performing a limited diagnostic ultrasound) is proper positioning of the patient. I prefer to always have the patient supine when performing any procedure, to avoid the potential for a vasovagal reaction. Next, the generalized needle approach and transducer plane are planned before marking and cleansing the skin. When performing an extremity procedure, there is often a choice between having the needle enter along the flat surface of the extremity or the curved surface. There are several benefits of having the needle enter along the curved surface, including more room to work in the space next to the extremity rather than directly over the flat surface of an extremity. Another advantage is that the puncture site can be an increased distance from the transducer (Fig. 9-3). This is helpful in that the needle can be more perpendicular to the sound beam (and therefore more conspicuous), and in addition the needle is not directly touching the transducer, which comes into play depending on the level of aseptic technique (see later discussion).

Transducer choice should also be considered at this time. In procedures of the extremities involving the elbow, wrist, hand, knee, ankle, and foot, a linear transducer greater than 10 MHz is typically used because the target is usually superficial. A high-frequency transducer provides the highest resolution, and the sound beam projecting in a linear fashion parallel to the transducer face creates an echogenic appearance of the needle (see Fig. 1-1A). A small-footprint transducer is often helpful at the distal extremities; often, a larger footprint transducer does not make contact with the full surface of the skin because of the multiple curvatures of the distal extremities and decreased thickness of soft tissues compared with more proximal joints. An offset to a small-footprint probe (often referred to as a hockey-stick design) is not required but is helpful when performing procedures of small parts because the hand holding the transducer is then away from the puncture site, improving visualization at the puncture site (see Fig. 1-1C). When performing procedures of the shoulder and hip, a curvilinear transducer is often selected (see Fig. 1-1B). The benefits of this type of transducer include a larger field of view of deeper structures and a lower frequency, improving sound beam penetration. In addition, the sound beam is emitted in a more radial fashion, which helps to improve conspicuity of a needle that is steeply angled to reach a deep target.

With regard to needle selection, I prefer a 20-gauge spinal needle (3.5 inches long) for shoulder and knee procedures, and a 22-gauge needle (either 3.5 or 1.5 inches long) for more distal procedures. Regardless of needle gauge, a stiffer needle is preferred to avoid bending of the needle. Because the goal of the direct in-plane method is to have the needle aligned with the ultrasound beam, a bent needle would not be fully visible in the ultrasound beam. A needle with a stylet may improve conspicuity at ultrasound and will ensure that the needle does not get plugged with tissue as the needle is advanced.

With regard to ergonomics, it is essential that the operator is comfortable during a procedure. I prefer to have the ultrasound monitor directly beyond the patient so that simply looking up from the procedure field will enable full view of the ultrasound image. If this cannot be achieved, the ultrasound monitor should ideally be less than 45 degrees to either side of the patient to minimize turning of the head or spine. A wall-mounted accessory monitor with an adjustable arm is very effective. I also prefer to have a stool on wheels to minimize fatigue and maximize mobility. Typically, the operator’s dominant hand should hold the needle, and the other hand should hold the transducer, although it is ideal to develop ambidextrous skills.

Prepping the Site

The first step in the procedure after finding the target, determining the approach, and choosing the transducer is marking the skin. This is completed before cleansing the skin and before sterile conditions. With a direct method of needle guidance, the transducer is placed over the target and the puncture site is determined. A mark is placed at the puncture site (such as an X), and a line is placed at the other end of the transducer to indicate the imaging plane (Fig. 9-4). The use of a surgical marker will help to ensure that the marks are not washed off during cleansing of the skin. If using the indirect method, an opened paperclip passed between the transducer face and the skin can be used to accurately mark the skin directly over a target (Video 9-3)image.5

With regard to sterile technique, the use of a probe cover and preparing a sterile field at the puncture site will minimize the risk of infection. Although sterile preparation of the site can take variable forms, the following represents the procedure used by this author. The operator wears sterile gloves and prepares the site with chlorhexidine solution. Sterile drapes or towels are placed around the puncture site covering the areas not washed with chlorhexidine solution. The puncture site is anesthetized with local anesthetic using a 25-gauge needle. A sterile probe cover kit is opened and placed on the sterile tray (Fig. 9-5A). The sterile operator opens the probe cover, and an assistant places nonsterile gel in the inside of the probe cover, followed by the transducer (see Fig. 9-5B to D). The operator then extends the probe cover along the transducer cable (see Fig. 9-5E) and secures the cover with sterile rubber bands (included with the probe cover) (see Fig. 9-5F). Sterile gel that is also included in the sterile probe cover kit is opened and deposited on one of the sterile drapes near the puncture site. The transducer in the cover is then dipped into the sterile gel and placed between the X and the line to reconfirm the target. The probe is removed from the site, and the procedure needle enters the skin (about 1 cm) at the puncture site. The transducer is returned to the procedure site to visualize the needle. Of note, the transducer is removed from the procedure site until the needle penetrates the skin to avoid inadvertent puncture of the transducer or transducer cover. With a sterile field placed around the procedure site, the operator can easily set the transducer down on the field while exchanging syringes, minimizing contamination.

Needle Visualization

The first critical rule when performing the in-plane method of needle guidance is that the needle should not be advanced unless it is seen in its entirety; otherwise, the procedure is essentially blind and not image guided. As stated earlier, the procedure is initiated when the needle is placed through the skin at the puncture site about 1 cm. At this point, the transducer is placed over the projected needle path, and the echogenic needle is identified. This is accomplished by translating the transducer side to side over the needle. Because the sound beam is focused, it is not uncommon to have the needle directly under the transducer but not visible on the ultrasound image. Side-to-side translation of the transducer should only be 1 mm at a time so as not to move the transducer away from the needle. It is often helpful to look down at the procedure site to ensure that the needle is indeed beneath and parallel to the transducer plane. Once again, the needle should not be advanced until seen in its entirety. Another basic concept is that the needle and transducer should not be moved at the same time. The transducer is moved to identify the needle, and the needle is then advanced (see Video 9-1). If the needle is no longer visualized during the procedure, needle advancement is stopped, and the transducer is moved as it was before, until the needle is again visualized and fully in plane. The transducer is then fixed in position as the needle is advanced again.

There are several options to improve conspicuity of the needle with ultrasound. A larger needle with a stylet may help, but a larger needle is not chosen for this reason. Some manufacturers have a coated or etched needle so that the needle becomes more echogenic (Fig. 9-6).6 This is helpful when performing a procedure that is deep where the needle angle is steep in order to get to the target. A very helpful option is to “jiggle” the needle while moving the transducer over the projected needle path (Video 9-4)image. With this maneuver, the needle is moved minimally forward and backward along the needle path, similar to needle movement with an intention tremor, which causes movement of the adjacent soft tissue and can help locate the needle. Of note, the needle in this maneuver is not advanced or moved side to side. Another option is to rotate the needle because the bevel of the needle may produce a more echogenic appearance. The most important technique to improve visualization of the needle is to have the needle as close to perpendicular to the sound beam as possible. Similar to anisotropy of tendons, a needle that is oblique to the sound beam will be less echogenic (Fig. 9-7A), whereas a needle that is perpendicular will be very echogenic with a strong reverberation artifact (see Fig. 9-1B) (Video 9-5)image. A perpendicular alignment between the sound beam and needle can be accomplished by having the puncture site farther removed from the transducer, which is possible when performing a procedure along the curvature of an extremity (see Fig. 9-3B). Another option is to move the transducer or deform the soft tissues with a heel-toe maneuver (see Fig. 9-3C). Many ultrasound machines have the ability to steer the ultrasound beam so that the insonation angle between the needle and the beam is ideally perpendicular to eliminate needle anisotropy (see Fig. 9-7B).

When attempting to align the needle along the long axis of the sound beam, as in the in-plane approach, it is not uncommon to identify only a short segment of the needle. This finding indicates that the transducer alignment and needle are not parallel but instead are crossing each other (Fig. 9-8). The longer the visible segment, the more the needle and sound beam are parallel. To correct this, the transducer should be turned clockwise or counterclockwise. If the segment of needle is increasing in length, the rotation is in the correct direction because the needle and sound beam become more parallel (Video 9-6)image. On the contrary, if the segment of needle becomes shorter, the transducer is being turned in the wrong direction because less of the needle is in the sound beam path.

Joint Procedures

Percutaneous joint procedures can include aspiration (for infection or crystal analysis), injection (both diagnostic and therapeutic using anesthetic agents or corticosteroids, or for the purpose of injecting contrast before magnetic resonance imaging [MRI] or CT), or less commonly synovial biopsy. Accuracy of such procedures is improved compared with blind attempt if the needle tip is directly visualized with ultrasound within the target.4 One key concept is that nearly every synovial joint in the extremity has one recess that preferentially distends with joint fluid and is visible at imaging.7 These recesses directly communicate with their respective joint articulations so that a joint procedure targets these sites rather than the joint articulations, which would potentially harm fibrocartilage and hyaline cartilage. These distinct joint recesses are assessed for joint fluid or synovial hypertrophy and are targeted for the joint procedure.

When accessing a joint recess for a procedure, the specific recess of a joint is assessed. If there is distention of the recess with fluid, that site would be the ideal target. If the recess is not distended, then the site is still targeted, although injection of a collapsed recess is more difficult. In this situation, it is important to confirm intra-articular needle placement before a diagnostic or therapeutic injection. This is accomplished with a test injection of local anesthetic. Uncommonly, if a joint does not have a prominent recess, a needle can be directly advanced into a joint articulation, such as accessing the sacroiliac joint or first carpometacarpal joint. Joint injection can be completed with almost any needle gauge, although I prefer a 20- or 22-gauge needle for stiffness. Joint aspiration should be at least 20 or 22 gauge, with 18—gauge considered if joint fluid is heterogeneous. Synovial biopsies may be completed with mechanical core biopsy guns, whereas 22-gauge needles with short throw (i.e., 1 cm) are preferred given the small sizes of the various joint recesses (Video 9-7)image. Biopsies of synovial hypertrophy tend to be reserved to evaluate for atypical infection or synovial proliferative disorders (such as pigmented villonodular synovitis); such biopsies in the setting of a systemic inflammatory arthritis often reveal nonspecific inflammation.

Shoulder

Regarding the shoulder joint, joint effusions accumulate within the biceps brachii tendon sheath because this space openly communicates with the glenohumeral joint (in the absence of biceps brachii long head tenosynovitis). Other glenohumeral joint recesses include the axillary recess, the subscapularis recess, and the posterior glenohumeral joint recess (assessed in external rotation).8 To access the glenohumeral joint, a posterior approach targeting the posterior glenohumeral recess is preferred (Fig. 9-9).3,9 The transducer is placed long axis to the infraspinatus tendon, and the needle is advanced in plane from lateral to medial (or medial to lateral) until the needle tip is located at the surface of the humeral head hyaline cartilage (see Video 9-7). The joint recess is wider more medial adjacent to the hyperechoic fibrocartilage labrum, especially with external rotation of the shoulder. The biceps brachii tendon sheath is not typically targeted for glenohumeral joint access because open communication between the biceps sheath and joint may not always be present in the setting of biceps tenosynovitis.