Interventions Involving the Bone, Soft Tissues, and Joints

12 Interventions Involving the Bone, Soft Tissues, and Joints

Despite the introduction and technical improvement of sectional imaging (CT and MRI), direct arthrography is still an important tool in the diagnosis of musculoskeletal disorders. It should always be combined with CT or MRI to maximize diagnostic information.

Advantages of direct arthrography (in combination with sectional imaging)

• The injected fluid distends the joint and so allows better assessment of articular structures.

• Visualization of contrast imbibition or leakage provides increased sensitivity for tears involving ligaments, menisci, or disks.

• High image contrast between cartilage and joint interior improves the assessment of cartilaginous lesions.

In addition, direct arthrography may be augmented by the diagnostic and/or therapeutic injection of a local anesthetic and/or an anti-inflammatory steroid. Analysis of aspirated joint fluid, prior to the contrast injection, can also contribute to obtaining a diagnosis (septic arthritis, crystal arthropathy, etc.).

Note

Following appropriate informed consent, direct arthrography must be performed under strictly aseptic conditions.

12.1.2 Contraindications

• Infected soft tissue along the access path.

• Pathologic clotting profile (INR > 1.5, PTT [partial thromboplastin time] > 50 seconds, platelet count < 50 000/µL), anticoagulation therapy.

12.1.3 Technique

The injection for direct arthrography is usually performed under imaging guidance using ultrasound or fluoroscopy ( Figs. 12.1 and 12.2). This ensures that the contrast agent is accurately injected into the joint. In addition, functional images and/or dynamic studies can be obtained under an image intensifier before or after the injection. Arthrography is also possible under CT or MRI control or by using anatomical landmarks for guidance (“blind technique”).

The following contrast medium dilutions are recommended to achieve optimum image contrast:

• Image intensifier/CT: Iodine-containing contrast medium, diluted 1: 1 with normal saline or local anesthetic.

• MRI: Gadolinium-based contrast agent, dilution 1: 200.

The reader should refer to the specialized literature for the exact technique of intra-articular injections of individual joints.

12.1.4 Complications

• Septic arthritis: This risk is minimal when a consistent sterile method of working is adopted (~ 1/20 000 arthrographies).

• Allergic reactions: These are extremely rare after intraarticular drug administration.

• Localized pain and limitation of motion: These depend on the amount of injected fluid and are reversible; local cooling and rest may be indicated.

• Extra- or intra-articular hemorrhage: Knowledge of vascular anatomy and attention to contraindications regarding coagulation (Chapter 12.1.2) help to minimize this risk.

12.2 Biopsy

12.2.1 Indications

Any biopsy of the musculoskeletal system requires a precise indication in consultation with the responsible clinician and an experienced pathologist. The main indications are:

• Histological examination of a (solitary) suspicious finding for metastasis.

• Confirmation, exclusion, and subtyping of (solitary or oligo-ostotic) plasmacytoma and malignant lymphoma.

• Differentiation between tumor-related and osteoporotic fracture.

• Confirmation of infection and its classification.

• Classification of primary bone and soft tissue tumors.

Lesions that have been unequivocally classified with imaging, especially those that can be identified as “leave-me-alone” lesions, need no histological clarification.

If the finding relates to a primary bone or a soft tissue tumor, then the following conditions should be fulfilled prior to biopsy:

• Establishing the indication (especially the question whether an open biopsy is an alternative) is best accomplished after consultation in a multidisciplinary tumor conference.

• The pathologist should be experienced in bone and soft tissue tumors.

12.2.2 Contraindications

• Bleeding risk (INR > 1.5, PTT > 50 seconds, platelet count < 50 000/µL).

• Hypervascularized lesion in the immediate vicinity of the spinal cord.

• Infected access path to a noninfected lesion.

• Unfavorable location (e.g., atlas, odontoid process).

Fig. 12.1 Bicompartmental arthrogram of the wrist performed under fluoroscopic guidance. DRUJ, distal radioulnar joint.

12.2.3 Technique

The biopsy access route should be agreed upon in consultation with the operating surgeon in order to protect uninvolved compartments and neurovascular bundles for subsequent curative surgery.

In most cases analgesia and sedation is adequate for percutaneous biopsy. Usually CT is employed as the imaging modality for guiding a percutaneous biopsy where the anatomy is complex (possibly using CT fluoroscopy; Figs. 12.3 and 12.4). Depending on location and tissue contrast, the procedure may be possible with, or may necessitate, the use of ultrasound ( Fig. 12.5) or MRI guidance. The type of biopsy needle depends strongly on the nature of the lesion; a distinction is made between aspiration, cutting, and trephine biopsy needles. A combination of several types of needles is often chosen via a coaxial needle technique; for example, an aspiration needle for fluid components, a cutting biopsy needle for soft tissue components, and a trephine biopsy needle for hard bone.

Fig. 12.2 Ultrasound-guided arthrography of the hip. (a) The illustration shows the position of the puncture needle. (b) The fluid within the joint is clearly visible.

Fig. 12.3 CT-guided bone biopsy. (a) Single osteoblastic focal lesion in T10. (b) Biopsy under CT fluoroscopy. Histology confirmed metastatic breast cancer.

Direct assessment of the tissue sample by an on-site pathologist is ideal. If this is not practical, then three cores should be sampled if at all possible. It should be borne in mind when selecting the biopsy site that sclerotic components have less prospect of success than osteolytic areas, while necrotic parts should be avoided. A specimen should always be sent for microbiological examination as infection may mimic tumor and vice versa.

12.2.4 Complications

The complication rate for percutaneous biopsy depends mainly on the site and type of needle used. The literature reports complication rates as ranging between 0 and 10% of cases. Serious complications occur in less than 1% of biopsies. These include hemorrhage requiring blood transfusion, infection, neurologic deficits, pneumothorax during thoracic spine procedures, and (rarely) fractures.

12.2.5 Results

Image-guided percutaneous biopsy has several advantages over open biopsy: lower complication rate, earlier initiation of therapy after biopsy, and reduced costs. It has also been shown that the accuracy of percutaneous biopsy at 81 to 97% is comparable with that of open biopsy. The distinction between benign and malignant, taken on its own, has a success rate of approximately 98%.

12.3 Drains

12.3.1 Indications

Percutaneous drainage should be considered as a primary step for all soft tissue abscesses. However, insertion of a drain is only advocated for an abscess with a larger diameter (> 3 cm); smaller abscesses can be punctured or aspirated ( Fig. 12.6). The indication for the procedure should be established by interdisciplinary consultation.

12.3.2 Contraindications

Hemorrhage (INR > 1.5, PTT > 50 seconds, platelet count < 50 000/µL).

12.3.3 Technique

Choice of the suitable image-guided modality: CT lends itself for anatomically complex regions, while ultrasound is also suitable for easily accessible sites, possibly combined with fluoroscopy.

A distinction is made between two techniques for placing a drain:

• Trocar technique: After applying local anesthetic down to the abscess and making a trial aspiration, the drain is inserted directly into the abscess with the aid of the provided guide needle and the pointed central stylet. The approach requires a safe access route.

• Seldinger technique: The abscess is punctured under local anesthesia using an 18G needle. After a trial aspiration, a steel wire is inserted into the abscess via the 18G needle, which is then removed. The access route may be dilated over the wire before insertion of the drain ( Fig. 12.7).

Large-bore drains (for soft tissue abscesses usually 14F) should be used for viscous, purulent material; smaller-bore drains (8 to 10F) are adequate for more liquid material. More important than drain size is the ability to empty the abscess completely at the first attempt and to carefully irrigate the abscess cavity several times with sterile saline solution (irrigation volume = half of the aspiration volume). After several irrigations the aspirated irrigation fluid should be as clear as possible and of low viscosity.

The intervention is completed with the careful contrast filling of the abscess cavity using diluted contrast agent and confirmation by CT. In case of ultrasound-guided drain insertion, a fluoroscan may be used in adjunct. If there are still noncontrasted abscess areas present, then a decision should be considered regarding a further drain placement or aspiration. Securing the drain to the skin with a cutaneous suture is recommended, as is a customized plaster to avoid kinking. Do not forget to send a specimen to microbiology for culture and determination of the sensitivity of the pathogen.

Fig. 12.4 CT-guided soft tissue biopsy. (a) Marginal contrast-enhancing, space-occupying lesion (arrows) in the left psoas muscle (abscess). (b) The tip of the needle is advanced to the lesion before performing the punch biopsy.

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