CARPAL TUNNEL | INFEROSUPERIOR PROJECTION WRIST

CARPAL TUNNEL (CANAL) - TANGENTIAL INFEROSUPERIOR PROJECTION: WRIST GAYNOR-HART METHOD

Warning:

• If patient has possible wrist trauma, do not attempt this position before routine wrist series has been completed and evaluated to rules out possible truama of distal forearm and wrist or with a carpal tunnel syndrome.

Pathology Demonstrated:

• This projection is performed most commonly to rule out abnormal calcification and bony changes in the carpal sulcus that may impinge on the medial nerve, as with carpal tunnel syndrome.
• It also visualizes fractures of the hamulus process of the hamate, pisiform, and trapezium.

Technical Factors:

• IR size - 18 x 24 cm (8 x 10 inches)
• Detail screen, tabletop
• Digital IR - use lead masking
• 64 or add up to 6kV range.

Shielding:

• Place lead shields over patient's lap to shield gonads.

Tangential (inferosuperior) carpal canal: Gaynor-Hart method.

Patient Position:

• Seat patient at end of table, with wrist and hand on cassette and palm down (pronated).

Part Position:

• Align hand wrist  with long axis of portion of IR being exposed.
• Ask patient to hyperextend wrist (dorsiflex) as far as possible by grasping the fingers with other hand and gently but firmly hyperextending the wrist until the long axis of the metacarpals and the fingers are as near vertical (90degrees to forearm) as possible (without lifting the wrist and forearm from the cassette).
• Rotate entire hand and wrist about 10degrees internally (toward radial side) to prevent superimposition of pisiform and hamate.

Central Ray:

• Angle CR 25 to 30degrees to the long axis of the hand. (the total CR angle in relationship to the IR must be increased if patient cannot hyperextend wrist as far as indicated.)
• Direct CR to a point 2 to 3 cm (1 inch) distal to the base of third metacarpal (center of palm of hand).
• Minimum SID is 40 inches (100cm).

Collimation:

• Collimate on four sides to area of interest.

Radiographic Criteria:
Structure Shown:

Tangential (inferosuperior) carpal canal: Gaynor-Hart method

• The carpals are demonstrated in a tunnel-like, arched arrangement.

Position:

• The pisiform and the hamulus process should be separated and visible in profile without superimposition.
• The rounded palmar aspect of the capitate and the scaphoid should be visualized in profile, as well as that aspect of the trapezium that articulates with the first metacarpal.

Collimation and CR:

• Collimation should be visible on four sides to area of affected wrist.
• CR and center of collimation field should be to midpoint of the carpal canal.

Exposure Criteria:

• Optimal density and contrast should visualized soft tissues and possible calcifications in carpal canal region, and outlines of superimposed carpals should be visible without overexposure of these carpals in profile. Traecular markings and bony margins should appear clear and sharp, indicating no motion.