Upper Extremity 1: Digits and Hand Anatomy

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Study Notes

Anatomy of the Digits

1st Digit (Thumb) comprises 2 phalanges: Distal Phalanx (farthest from palm) and Proximal Phalanx (closest to palm).
Phalanges separated by the interphalangeal joint (IP joint).
2nd to 5th Digits each have 3 phalanges: Distal, Middle, and Proximal Phalanx.
Each phalanx consists of three parts: Head (distal), Body (middle), and Base (proximal).
Metacarpals also possess the same three parts and are numbered 1-5 corresponding to respective digits.

Hand Structure

The hand contains 27 bones: 14 phalanges, 5 metacarpals, and 8 carpal bones.
1st Digit has 3 joints: IP Joint, MCP Joint (metacarpalphalangeal), and CMC Joint (carpometacarpal).
2nd to 5th Digits comprise 4 joints: DIP Joint, PIP Joint, MCP Joint, and CMC Joint.

Digit Radiography

Image receptor size: 10 x 12 inches; portrait orientation for upper extremity.
Standard SID: 40 inches for all upper extremity images.
Collimation: 1 inch on all sides of the digit.
Central ray should be perpendicular for all digits unless specified otherwise.
Ensure patient is seated with affected side nearest the table and elbows flexed at 90 degrees.
Use R/L markers and annotate digit number on the radiograph.

2nd - 5th Digits: PA Projection

Position the palmar surface against the image receptor (IR).
Slightly separate fingers and center the digit of interest on the IR.
Central ray is perpendicular to the PIP joint of the affected digit.
PA projection shows the affected digit clearly.

PA Projection Evaluation Criteria

Visualize entire digit from fingertip to distal metacarpal.
Ensure no overlap of soft tissue from adjacent digits.
Confirm equal concavity on both sides of phalangeal bodies to eliminate rotation.
Open IP and MCP joint spaces should be visible.

PA Oblique Projection for 2nd - 5th Digits

Place the palmar surface against the IR and slightly separate fingers.
Rotate the hand laterally 45 degrees; a sponge may be used for finger alignment.
Ensure fingers are straight to maintain open joint spaces.
Center the digit of interest on the IR with the central ray perpendicular to the PIP joint.

PA Oblique Projection Evaluation Criteria

Entire digit must be visible from fingertip to distal metacarpal.
Confirm 45-degree rotation by observing concavity on the elevated side.
No superimposition of the proximal phalanx or MCP joint by adjacent digits.
Open IP and MCP joint spaces must be present.

Lateral Projection for 2nd - 5th Digits

Ask the patient to extend the affected digit and ball up other fingers into a fist.
Position hand: lateral (radial) side for 2nd and 3rd digits, medial (ulnar) side for 4th and 5th digits to reduce OID.
Align the digit parallel with the IR and ensure it is straight in the center.
Adjust hand rotation for a true 90-degree lateral position; central ray is perpendicular to the PIP joint.

Lateral Projection Evaluation Criteria

Visualize entire digit from fingertip to distal metacarpal.
Ensure no rotation by observing concave anterior surfaces of phalanges.
No superimposition of the proximal phalanx or MCP joint by adjacent digits.
Open IP joint spaces must be evident.

1st Digit (Thumb): AP Projection

Position requires extreme medial rotation, with the posterior side of the thumb against the IR.
Bend the elbow to relieve arm pressure during imaging.

Description

This quiz covers the anatomy of the upper extremity, specifically focusing on the digits of the hand, including the thumb and other fingers. It includes details about the structure of phalanges and relevant anatomical terminology for injury description.