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1 Department of Radiology, Austin Health, 145-163 Studley Rd., Heidelberg,
Victoria 3084, Australia.
2 Department of Sports Imaging, North Sydney Orthopaedic and Sports Medicine
Centre, 286 Pacific Hwy., Crows Nest, New South Wales 2065, Australia.
Received December 2, 2003;
accepted after revision February 17, 2004.
Address correspondence to R. B. Zwar.
If corticosteroid injection has been requested, all previous imaging is first reviewed to identify any relative contraindications (which include glenohumeral joint osteoarthrosis, avascular necrosis of the humeral head, and recent rotator cuff tendon rupture).
The patient is then placed for injection in a semiprone position with the affected shoulder uppermost (Fig. 1). The ipsilateral arm is placed over a bolster or pillow to maintain the semiprone position and to optimize patient comfort.
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The patient and sonographic scanner are aligned so that the radiologist holding the sonographic probe and introducing the needle has a direct view of the sonographic screen. A broadband 5-12–MHz linear array transducer is aligned in the long axis of the musculotendinous junction of the infraspinatus muscle, just inferior to the scapular spine, with the posterior glenoid rim and posterior glenohumeral joint line centered in the field of view (Fig. 2). Transducer angulation in both the elevation and imaging planes is manipulated to clearly show the contours of the posterior glenoid rim, posterior glenoid labrum, and humeral head. Some operators also find it useful to mark the chosen transducer position with indelible ink on the skin surface.
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The articular cortex of the humeral head appears as a spherically curved echogenic line. The cortical surface of the posterior glenoid rim appears as a triangular echogenic structure just medial to this line. With appropriate transducer angulation, the fibrocartilaginous posterior glenoid labrum appears as a well-defined, triangular, uniformly echogenic structure (Fig. 3).
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After skin antisepsis and local anesthetic infiltration, a 20- to 22-gauge spinal needle is aseptically introduced and directly visualized in real time as it passes obliquely from the skin surface to the glenohumeral joint within the imaging plane of the transducer (Fig. 4). Ideally, the needle tip itself should be identified as a moving reflector. The path of the needle is adjusted so that the bevel passes into the joint space immediately deep relative to the free margin of the glenoid labrum and tangential to the curvature of the humeral head.
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On passage of the needle through the substance of the infraspinatus tendon or its musculotendinous junction, the flexible needle often tends to go off course as it dissects into and along the path of the tendon fibers. This tendency can be reduced by placing the bevel of the needle tip uppermost but also often requires some adjustment to the angle of needle introduction.
Passage of the needle tip into the glenohumeral joint is generally associated with a distinct feeling of transient capsular resistance followed by the sensation of a resistance-free space (Fig. 5). The actual joint injection can then be performed. If the needle tip is correctly positioned, there should be very little or no resistance to injection. If resistance is encountered, the lumen may be embedded within or directly abutting either hyaline cartilage or fibrocartilage. To correct this problem, the radiologist should first rotate the needle tip through successive small steps in search of a resistance-free position. If this rotation proves unsuccessful, the needle tip may then be advanced or withdrawn or both very slightly before again attempting to inject without resistance at successive small steps of rotation. Nevertheless, visualization of the needle tip itself can occasionally be difficult in the obese patient. In this situation, success depends on real-time visualization of the general direction of needle passage, recognition of a typical feeling as the needle tip passes through the joint capsule, and ensuring a lack of resistance to injection and the absence of any localized fluid pooling at the posterior joint line during early injection.
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In the early stages of injection with the patient in a semiprone position, typically no fluid pooling or distention is evident on real-time scanning at the posterior glenohumeral joint recess due to the injected substance running freely into the nonvisualized dependent anterior joint recess. If injected fluid is seen pooling immediately around the needle tip or distending the extracapsular space, the needle tip is not correctly positioned within the joint and repositioning is required.
Toward the end of glenohumeral joint injection, if a sufficiently large volume of fluid has been instilled, the posterior recess of the glenohumeral joint begins to distend, and the posterior capsule displaces away from the humeral head (Fig. 6). At this time, any echogenic component of the fluid injected (e.g., corticosteroid suspension or local anesthetic containing microbubbles) may be observed as a sudden "wash" of high-level echoes around the curvature of the humeral head and deep relative to the joint capsule. Finally, a hard-copy image may be recorded with the needle tip still in position to document objectively the intraarticular nature of the injection.
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Successful therapeutic injection of the shoulder joint for capsulitis has been achieved in more than 800 patients over a period of 8 years by two of the authors. The third author has achieved successful intraarticular placement of gadolinium contrast material for MR arthrography of the shoulder joint in more than 200 patients during the past 2 years (with the subsequent diagnostic MRI confirming a correct intraarticular location of the injected contrast material).
The usual method of injecting the glenohumeral joint for diagnostic arthrography (of any form) involves the use of fluoroscopy to first guide a needle into the joint from a direct anterior approach and then confirm correct intraarticular needle placement using a small test injection of radiopaque contrast material.
Sonography offers an accurate alternative to fluoroscopy for the injection of the shoulder joint [1, 2]. Sonographic guidance avoids the use of both ionizing radiation and iodinated contrast material and is generally faster than fluoroscopically guided injection. Both anterior and posterior sonographic approaches to glenohumeral joint injection have previously been reported [1, 2]; however, in each case, the methods described have used a perpendicular path of access to the joint (i.e., a vertical rather than obliquely oriented needle path). Such techniques can reduce operator confidence by preventing the continuous real-time visualization of the needle-tip position during introduction. Confidence in using an anterior approach can also be limited by the nonvisualization of the important anatomic landmark of the anterior glenoid labrum.
Regardless of shoulder size and body habitus, the relevant anatomy of the posterior glenohumeral joint recess is consistently resolved with high-resolution broadband linear array sonographic transducers. Nevertheless, as with any other form of sonographically guided percutaneous intervention, a careful real-time technique is critical to visualization of the needle. Although not essential, the use of real-time spatial compound sonography can also help to render needle-tip visualization more conspicuous.
Shoulder joint injection using a posterior approach under sonographic guidance is well tolerated. An advantage of the semiprone position is that the patient does not readily see the approaching needle, thus helping to minimize or alleviate fear. A posterior approach avoids any inadvertent intralabral or extraarticular contrast material staining along the anterior joint margin during the process of initial test injection to confirm needle-tip position (in practice, the anterior labrum is usually of greater interest than the posterior labrum). This approach also completely avoids any potential that may exist with an anterior approach for accidental puncture or injection of the major axillary neurovascular structures. Our use of an oblique needle path, which traverses the infraspinatus muscle and courses medially from a lateral direction, also eliminates any potential for the accidental puncture or injection of either the suprascapular or the circumflex scapular neurovascular structures or both (which can occur with the posterior approach described by Cicak et al. [2]).
In conclusion, intraarticular glenohumeral joint injection can be safely, accurately, quickly, and comfortably performed under sonographic guidance using a posterior approach.
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