Normal Wrist

Rationale and Indications

• Allows visualization of osseous anatomy and pathology, bone contours, and joint alignment

• Is recommended for any primary evaluation of osseous wrist pathologic processes such as fractures, dislocations or malalignment, infection, and bone tumors ( eTable 13-1 ; eFigs. 13-1 to 13-5 )

Fluoroscopy

Radiographic positioning for fluoroscopy for instability is described in eTable 13-2 ( eFig. 13-6 ). (See also eFigs. 13-1, 13-2, and 13-5 .)

Advantages

• Real-time imaging; captures transient abnormalities that occur with motion

• Is inexpensive

Limitations

• Cannot evaluate ligaments directly

• Cannot evaluate tendons, muscles, and nerves

• Is insensitive to early infection or intraosseous or nondisplaced fractures

• Uses ionizing radiation

Rationale and Indications

• Intraarticular injection of iodine contrast agent allows evaluation of disrupted intrinsic and capsular ligaments ( eFig. 13-7 ).

  

• Main indication: assessment of suspected triangular fibrocartilage (TFC) and triangular fibrocartilaginous complex (TFCC) tears, scapholunate ligament (SL) tears, and lunotriquetral (LT) tears

• Is indicated when there is a contraindication to MRI, patient is claustrophobic, or when the results of MRI are indeterminate regarding SL, LT, or TFC tears

• Can be performed without delay

• Can use single-, double-, or triple-compartment injection with diluted iodinated contrast medium (dilution)

Advantages

• Is inexpensive and quick

• Has no artifacts from metal hardware

• Can identify communicating/noncommunicating defects

• Can easily assess opposite side

Limitations

• Cannot evaluate ligaments directly

• Cannot evaluate tendons, muscles, and nerves

• Is insensitive to early infection or intraosseous or nondisplaced fractures

• Uses ionizing radiation

Rationale and Indications

• Provides multiplanar direct or reconstructed images and allows surface rendering to create 3D images

• Evaluates healing, nonunion of fractures, alignment after reduction of fracture fragments and those not seen on conventional radiography, and osteolysis

• Allows evaluation of gross soft tissue pathologic processes

• Evaluates bone tumor matrix (cartilage vs. osteoid)

• Evaluates suspected abnormality found on conventional radiography, especially in areas of complex anatomy such as the carpometacarpal joints

Advantages

• Shows high resolution of osseous structures

• Has multiplanar and surface-rendering capability

• Is more readily available than MRI

• Is less expensive than MRI

• Is quick compared with MRI

• Can easily and quickly perform additional positions so as to stress the distal radioulnar joint (DRUJ)

Disadvantages

• Provides limited evaluation of soft tissues compared with MRI

• Is expensive compared with conventional radiography

• Uses ionizing radiation

• May have beam-hardening artifact especially from metal

Technical Aspects

The patient's arm should be placed prone and extended above the head. A pillow can be placed under the upper chest for improved patient comfort. Suggested parameters to use (based on Siemens machines) are listed in eTable 13-3 . When metal or a cast is present, then the parameters are adjusted to obtain the best possible image with the least amount of beam-hardening artifact. This includes changing the kV, pitch, and kernel and using an extended CT scale.

Direct scanning is performed axially ( eFig. 13-8 ) in the craniocaudal direction starting from the metacarpal bases and ending 2 cm proximal to the distal radius. If a fracture is present, then the extent of the fracture is included.

Multiplanar reformatted (MPR) images are often very useful to obtain coronal and sagittal planes as well as an oblique sagittal plane through the long axis of the scaphoid. These images are obtained with 1.0-mm-thick slices × 1.0-mm interval gap.

Rationale and Indications

Several authors have reported that CT arthrography can be advantageous. Currently, it is used to evaluate articular cartilage as well as SL, LT, and TFC tears. At our institution, CT wrist arthrography is not routinely performed.

Rationale and Indications

• Assesses soft tissue anatomy and pathology, including the intrinsic and extrinsic ligaments, neurovascular structures, and osseous pathology

Advantages

• Is multiplanar and nonionizing

Limitations

• Is expensive

• Has long imaging time

• May have artifacts from metal, motion, pulsation, chemical shift, or fat saturation

• Can be difficult for claustrophobic patients in closed magnets

Technical Aspects

Suggested parameters with a 1.5-T magnet include the arm placed prone and over the patient's head. The key is patient comfort; therefore, the elbow may be slightly flexed and the palm may be supine, prone, or lateral. Pillows can be placed under the chest to flex the shoulder slightly forward ( eTables 13-4 and 13-5 ).

1.5-tesla as compared to 3.0-tesla MRI:

Until recently, 1.5-tesla MRI has been used as the reference standard for most clinical applications, including evaluation of the complex wrist anatomy. However, numerous limitations in visualization and assessment of small ligaments and tendons within the wrist have been reported with traditional 1.5-tesla MRI.

3.0-Tesla MRI improves signal-to-noise ratio (SNR) by approximately twofold when compared to conventional 1.5-tesla MRI. In addition, 3.0-tesla MRI increases spatial resolution by utilizing smaller slice thickness, larger matrix size and smaller field of view.

The TFCC, dorsal, and volar extrinsic and the intrinsic ligaments along with the flexor and extensor tendons compose the support network of the wrist. 3.0-Tesla MR images of these complex wrist structures, including the TFCC, intrinsic and extrinsic radiocarpal ligaments, and flexor and extensor tendons, are depicted in eFigure 13-9 .

The fine components of the TFCC are easily appreciated on high-resolution 3.0-tesla MR images. Likewise, the individual bands of intrinsic ligaments are clearly visualized because of central positioning within the wrist coil. In addition, the individual slips and the intracompartmental intertendinous separations of the flexor and extensor tendons inseparable at lower field strengths are well seen on the 3.0-tesla MRI because of improved contrast resolution.

The high SNR and high spatial resolution of 3.0-tesla MR images allow for better visualization of the volar extrinsic ligaments, even in the absence of contrast-enhanced MR arthrography. With 3.0-tesla MRI, the dorsal extrinsic ligament complex appears as thickening of the dorsal wrist capsule below the extensor compartment tendons.

Rationale and Indications

• Allows for distention of the joint to best assess the TFC and intrinsic ligaments

Technical Aspects

At our institution, a few fluoroscopic images are taken before injection ( eTable 13-6 ) for comparison with the postinjection fluoroscopic images. This includes profiling the SL, LT, and DRUJ with the wrist prone and the SL with the wrist supine with a clenched fist.

The first step is to inject the radiocarpal joint under fluoroscopic guidance ( eFig. 13-10 ), and the second step is to take the patient to the MR scanner for multisequence and multiplanar imaging. A repeatedly successful and suggested technique is to use a dorsal approach to touch the scaphoid proximal to the ridge at the scaphoid waist and then advance the needle into the radioscaphoid joint.

Using the dorsal approach to the radioscaphoid joint requires placing the wrist prone and in ulnar deviation to increase the intraarticular area of the radioscaphoid joint. First, under fluoroscopy, the skin surface is marked overlying the desired point of needle tip insertion, which is just proximal to the scaphoid ridge at its waist at the radial margin of the bone. The area should then be prepped and draped in sterile fashion. Subcutaneous anesthesia is recommended, and deeper anesthesia is optional. A 23- or 25-gauge, 1-inch needle is used to touch the scaphoid at the desired point. Then, the needle is directed toward the radioscaphoid joint and advanced 2 to 3 mm into the joint.

Sometimes the needle may be advanced too far volarly if it slips along the radial side of the scaphoid. If this occurs, then the needle must be retracted until it is in the joint.

Once intraarticular needle tip position is confirmed with contrast agent alone or mixed with the diluted 1 : 200 gadolinium, the joint is distended. The volume often is less than 5 mL, unless there are communicating defects in the intrinsic ligaments or the TFC. After the injection, the same preinjection fluoroscopic images are taken. Then the patient is taken to the scanner for imaging within 30 minutes.

Advantages

• Can assess TFC, SL, and LT ligament tears

• Shows better distention of the joint capsule to detect extrinsic ligament pathology

Limitations

• Is invasive compared with routine MRI

• Requires extra time and labor minutes per procedure

• Must coordinate availability of fluoroscopic unit with that of MR scanner

• Uses ionizing radiation

• Has potential for infection and allergy to anesthetic or contrast agent

• Use of extra-articular injection of contrast medium can make interpretation difficult

• Has risk of air bubbles being misinterpreted as loose bodies

Rationale and Indications

• Is based on bulk flow and diffusion of intravascular contrast medium into the joint. The greater the amount of synovial fluid and inflammation in the joint, the greater the enhancement.

• Consider when evaluating small joints, such as the wrist or after surgery

• Allows detailed assessment of intraarticular and extra-articular disease of a joint. Questionable pathologic processes will enhance.

Technical Aspects

Because indirect MR arthrography is not performed at our institution, more detail can be obtained from the article by Bergin and Schweitzer.