General Technical Considerations

Therapeutic injections into axial extraspinal joints are performed on an outpatient basis in the fluoroscopic suite. Radiological guidance first consists in opacifying the joint space prior to the therapeutic injection to check for the accurate intraarticular needle placement. The patient is placed in the supine (or, if necessary, prone) position to avoid or to reduce the effects of vagal discomfort. Prescription of a sedative treatment just before the procedure is usually not necessary. However, as for any radiological invasive procedure, it is necessary to inform and reassure the patient. The skin is prepped with an iodine solution. Further procedure varies according to the superficial (acromioclavicular and sternoclavicular joints) or deep (pubic sym-physis, costovertebral joint, and transversosacral neoarthrosis) situation of the joint. For superficial joint puncture, skin anesthesia is not always required: actually, the direct puncture of the joint is not more painful than the puncture for skin anesthesia. A 20-gauge, 9-cm needle may be used as for appendicular joints. This type of needle is flexible enough to be curved after having entered the joint, so that further contrast medium injection may be controlled safely under fluoroscopic monitoring. It also allows easy aspiration of fluid from the joints. However, due to the superficial location of these joints, a short intradermic-type (25 gauge, 16 mm) needle may also be used, avoiding any risk of injury to the underlying soft tissues. In addition, this type of needle is too thin to allow release of contrast medium from the syringe if the needle is not correctly inserted within the joint cavity. After removal of the needle, gentle compression and massage of the skin at the puncture site help avoid fluid extravasation.

For deep joint puncture, anesthesia of the skin and underlying soft tissues is appropriate, as well as the use of a 20-gauge, 9-cm needle.

Prior to contrast medium injection, aspiration of joint fluid is recommended. Joint effusion would actually dilute the active principle and potentially reduce its effectiveness. It would also lead to deterioration of the image quality of the arthrogram—even if the joint opacification is not requested for diagnostic purposes, a rudimentary arthrogram (one or two films) should be obtained in every case, at least for legal purposes. If present, joint fluid must be inspected immediately to rule out the possibility of unexpected infection, which would contraindicate a planned steroid injection. The injection of a small amount (1-2 mL) of contrast medium is followed under fluoroscopic control. Additional contrast material may be injected for diagnostic purposes. However, joint distension may be responsible for extravasation and may thus compromise the efficiency of the therapeutic injection. To avoid excessive extravasation of the

FIGURE 1 Arthrography during acromioclavicular joint therapeutic injection. Arthrography as the first step prior to steroid injection (A). Attenuated opacification of the joint after injection of the steroid (B).

steroid after removal of the needle, the finger is released periodically from the plunger to verify that no injected material returns into the syringe. At least two radiographs are taken. The first radiograph demonstrates the correct opacification of the joint, and the second one shows the dilution of the contrast material by the injected therapeutic fluid (Fig. 1) and the absence of extravasation through the site of joint puncture.

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