Chapter 13: Contrast Arthrography

Detailed Chapter Overview

Contrast arthrography is a specialized diagnostic imaging procedure involving the injection of a contrast medium into a joint space to visualize the soft tissue structures. While largely superseded by Magnetic Resonance Imaging (MRI) for many applications, arthrography remains a valuable tool for specific clinical questions, particularly when MRI is contraindicated or when dynamic, real-time evaluation of joint motion is required. This chapter provides a definitive guide to the principles, procedures, and clinical applications of contrast arthrography. A core focus is on the meticulous application of sterile technique, as the procedure is invasive and carries a risk of infection. The chapter details the different types of contrast media used—positive (iodinated), negative (air), and double-contrast combinations—and explains the diagnostic advantages of each. It provides a comprehensive survey of the joints most commonly examined, including the shoulder, knee, hip, and wrist. For each joint, the text delves into specific clinical indications, such as identifying rotator cuff tears, meniscal injuries, or ligamentous damage. The chapter gives detailed, step-by-step instructions on needle placement, contrast injection, and the subsequent radiographic series. A central theme is the importance of stressing or exercising the joint after injection to ensure adequate coating of the internal structures with contrast. For every projection, rigorous evaluation criteria are established, training the radiographer to produce a series of images that clearly delineate the soft tissue anatomy and pathology of the joint in question.

In-Depth Study Guide

General Principles and Procedures

Arthrography is the radiographic study of synovial joints and their related soft tissue structures. Because it is an invasive procedure, it must be performed under strict aseptic (sterile) conditions.

1. Purpose and Indications

• Purpose: To visualize the joint capsule, menisci, ligaments, articular cartilage, and other soft tissues that are not visible on plain radiographs.
• Common Indications: Suspected tears of the joint capsule, menisci, or ligaments; rotator cuff tears; cysts; and loose bodies within the joint.

2. Sterile Technique and Procedure

• Consent: As with any invasive procedure, informed consent must be obtained from the patient.
• Sterile Tray: A pre-packaged, sterile arthrogram tray is used, containing drapes, gauze, antiseptic solution, syringes, needles, and a connecting tube.
• Site Preparation: The skin over the joint is shaved (if necessary) and thoroughly cleansed with an antiseptic solution like Betadine or chlorhexidine. The area is then draped with sterile towels to create a sterile field.
• Local Anesthetic: A local anesthetic (e.g., lidocaine) is injected into the skin and deeper tissues to numb the area before the larger joint needle is inserted.
• Joint Aspiration: Before injecting contrast, any existing joint effusion (excess fluid) is often aspirated to prevent dilution of the contrast media and for laboratory analysis.

3. Contrast Media

The choice of contrast depends on the joint being examined and the clinical question.

• Positive Contrast (Radiopaque): A water-soluble, iodinated contrast medium is used. It appears white on a radiograph.
• Negative Contrast (Radiolucent): Room air or carbon dioxide is used. It appears black on a radiograph.
• Double-Contrast: A combination of both positive and negative contrast is used. This technique is often preferred as the air expands the joint capsule and forces the thin layer of positive contrast against the soft tissues, providing excellent detail of the structures.

Specific Joint Arthrography Procedures

Shoulder Arthrography

• Clinical Indications: Primarily performed to identify tears of the rotator cuff or glenoid labrum, as well as to investigate persistent pain or joint instability.
• Anatomy of Interest: Rotator cuff (supraspinatus, infraspinatus, teres minor, subscapularis muscles), joint capsule, and glenoid labrum.
• Needle Placement: The needle is typically inserted into the joint space from an anterior approach, just lateral to the coracoid process.
• Radiographic Routine: After contrast injection, a standard trauma shoulder series is often performed, including AP (internal and external rotation), Grashey (AP oblique), and an axillary or Scapular Y lateral. Fluoroscopic spot films may also be taken as the patient rotates their arm. A leak of contrast from the joint capsule into the subacromial bursa is a classic sign of a full-thickness rotator cuff tear.

Knee Arthrography

• Clinical Indications: To evaluate tears of the menisci (medial and lateral) and the cruciate or collateral ligaments.
• Anatomy of Interest: Medial and lateral menisci, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), and joint capsule.
• Procedure: A double-contrast study is most common. The knee is flexed to 90 degrees for needle insertion. After injection, the knee is gently exercised or "stressed" to ensure the contrast fully coats the menisci.
• Radiographic Routine:
  • AP and Lateral: Basic survey images.
  • Fluoroscopic Spot Films: The radiologist will take multiple images while stressing the knee and rotating it. The primary goal is to obtain images of each meniscus in profile. This requires rotating the leg approximately 20 degrees for each exposure, resulting in about 6 images per meniscus.
  • Stress Views: Manual stress may be applied to the knee (varus and valgus) to widen the joint space medially or laterally, assessing the integrity of the collateral ligaments. A widening of the joint space indicates a ligamentous tear.

Wrist Arthrography

• Clinical Indications: To evaluate persistent pain, limited motion, or trauma to the wrist. Primarily used to identify tears of the triangular fibrocartilage complex (TFCC) or ligamentous tears.
• Needle Placement: The injection is typically made into the radiocarpal joint on the dorsal aspect of the wrist.
• Radiographic Routine: After injection, the wrist is gently moved to distribute the contrast. A series of PA, oblique, and lateral projections are taken. Leakage of contrast from the radiocarpal joint into the distal radioulnar joint is indicative of a TFCC tear.

Hip Arthrography

• Clinical Indications: In adults, it is most often performed to detect a loose hip prosthesis or to evaluate for infection. In children, it is used to assess for congenital hip dysplasia.
• Needle Placement: Requires fluoroscopic guidance for accurate placement into the hip joint. A long spinal needle is used.
• Radiographic Routine: After injection, the hip is exercised. AP and "frog-leg" lateral projections are typically performed to assess the distribution of contrast and outline the femoral head and acetabulum.