Hand Anatomy Quiz

Hand Anatomy

• The hand consists of 27 bones: 14 phalanges (fingers and thumb), 5 metacarpals (palm), and 8 carpals (wrist)

Phalanges

• Each finger and thumb is called a digit
• Each digit contains 2 or 3 bones called phalanges (singular: phalanx)
• Phalanges are numbered 1-5, with thumb being 1 and little finger being 5
• Digits 2, 3, 4, and 5 are composed of 3 phalanges:
• Proximal (closest to the palm)
• Middle
• Distal (farthest from the palm)
• Thumb (digit 1) is composed of 2 phalanges: proximal and distal

Metacarpals

• Make up the palm of the hand
• 5 Metacarpals in each hand
• Numbered the same as the digits
• 3 parts:
  • Head - Distal round portion
  • Body (Shaft) - Long curved portion
  • Base - Expanded proximal end articulates with carpals

Carpals

• Make up the wrist
• 8 total carpals in each wrist
• All have specific names

Joints of the Hand

• 1st Digit (Thumb):
  • Interphalangeal (IP) Joint: Located between proximal and distal phalanges of the thumb
  • 1st Metacarpophalangeal (MCP) Joint: Located between proximal phalanx and 1st metacarpal
  • 1st Carpometacarpal (CMC) Joint: Located between the proximal metacarpal and the trapezium (carpal)
• 2nd - 5th Digits:
  • Distal Interphalangeal (DIP) Joint: Located between the distal and middle phalanges
  • Proximal Interphalangeal (PIP) Joint: Located between the middle and proximal phalanges
  • Metacarpophalangeal (MCP) Joint: Located between the proximal phalanx and the distal metacarpal

General Positioning Considerations

• Typically performed with patient seated sideways at the end of the table
• Tabletop height should be near shoulder height for full arm support
• 40" SID (Source Image Distance)

Trauma Patients

• X-rays can be completed with patient on stretcher

Pediatric Patients

• Patient motion is a concern
• Immobilization needed using sponges and tape
• Involve parents
• Use soothing language that a child can understand

Geriatric Applications

• Provide clear and complete instructions
• May have difficulty holding strenuous positions
• Reduce technique due to potential osteoporosis

Exposure Factors

• Lower to medium kVp (60-80)
• Short exposure time
• Small focal spot
• Correctly exposed images should reveal soft tissue margins and fine trabecular markings of all bones
• Grids not used unless body part is greater than 10cm

Collimation, Positioning, and Markers

• Collimate down without cutting off essential anatomy
• General rule regarding IR size: Select the smallest IR for the part being imaged
• Positioning rule: Always place the long axis of the part being imaged parallel to the long axis of the IR being exposed
• Correct marker should be demonstrated on each image

Clinical Indications

• Dislocation: displacement from joint
• Fractures:
  • Bennett fx: fracture through base of the first metacarpal bone, extending into the CMC joint with subluxation w/ posterior displacement
  • Boxer fx: Transverse fx that extends through the metacarpal neck – most commonly seen on 5th metacarpal
  • Skier’s thumb: sprain or tear of the ulnar collateral ligament of the thumb near the MCP joint of the hyperextended thumb (occurs from falling on outstretched arm and hand)
• Osteoarthritis: AKA degenerative joint disease (considered normal in the aging process)
• Rheumatoid Arthritis: Chronic systemic disease with inflammatory changes throughout connective tissues (3x more common in women than men)
• Osteoporosis: reduction in the quantity of bone or atrophy of skeletal tissue (occurs in postmenopausal women and elderly men)
• Foreign Objects

Positioning of the 1st Digit (Thumb)

• Routine Views:
  • AP
  • PA Oblique
  • Lateral

AP Projection - 1st Digit

• 40" SID
• No Grid
• Smallest IR available
• Arm extended in front
• Rotate arm internally to supinate thumb
• Align thumb with long axis of IR
• CR: 1st MCP joint

PA Projection - 1st Digit

• Used if patient is unable to be positioned for AP
• 40" SID
• Place hand in near-lateral position
• Rest thumb on sponge support block that is high enough to keep thumb from rotating
• CR: 1st MCP joint
• PA is not advisable because of loss of definition caused by increased OID

Evaluation Criteria for 1st Digit - AP and PA

• Entire thumb demonstrated (including first CMC joint)
• Center field at first MCP joint
• No rotation of phalanges
• Exposure factors
• PA is not advisable because of loss of definition.

PA Oblique Projection - 1st Digit

• 40" SID
• Smallest IR Size available
• No Grid
• Abduct thumb slightly with palmar surface of hand in contact with IR (this naturally places thumb in 45˚ oblique)
• CR: 1st MCP joint

Evaluation Criteria for 1st Digit - PA Oblique

• Entire thumb demonstrated
• Joints partially open as in 45° oblique
• Center of field at first MCP joint
• Exposure factors

Lateral Projection - 1st Digit

• 40" SID
• Smallest IR Size
• No Grid
• Start with hand pronated and thumb abducted
• Fingers slightly arched
• Medial rotate hand slightly till thumb is in true lateral position
• CR: 1st MCP joint

Evaluation Criteria for 1st Digit - Lateral

• Entire thumb demonstrated
• Center of field at first MCP joint
• No rotation from lateral evident
• Exposure factors

Positioning of Fingers/Digits 2-5

• Routine Views:
  • PA
  • PA Oblique
  • Lateral

PA Projection - Fingers 2-5

• 40" SID
• No Grid
• Smallest IR available
• Pronate hand with fingers extended
• Center and align long axis of affected finger with long axis of IR
• CR perpendicular to IR directed at PIP joint
• Recommended collimation: Collimate on four sides to area of affected finger and distal aspect of metacarpal

Evaluation Criteria for PA Projection - Fingers 2-5

• Entire finger and minimum ⅓ of MCP demonstrated
• Center field at PIP joint
• No rotation of phalanges
• Exposure factors

PA Oblique Projection - 2-5th Digits

• 40" SID
• No Grid
• With fingers extended rotate hand laterally 45˚ - 3rd – 5th digit (separate fingers and carefully position the finger being examined against a block)
• CR: PIP Joint
• 2nd digit: Rotate medially 45˚- other fingers flexed to prevent superimposition.

Evaluation Criteria for PA Oblique Projection - 2-5th Digits

• Entire phalanx and MCP joint demonstrated
• IP and MCP joints open
• Center field at PIP
• Exposure factors

Lateral Projection - 2-5th Digits

• 40" SID
• No Grid
• CR: PIP Joint
• Lateromedial (3-5th digit): Place hand in lateral position (thumb side up) with finger to be examined fully extended, flex unaffected fingers, finger is parallel to IR
• Mediolateral (2nd digit): Rotate hand medially till thumb side is down and second digit is touching IR, flex unaffected fingers
• Use a radiolucent sponge to support the hand as needed

Evaluation Criteria for Lateral Projections - 2-5th Digits

• Entire phalanx and MCP joint demonstrated
• Center field at PIP
• True lateral position
• Digit parallel to IR
• Exposure factors

Positioning of the Hand

• Routine Views:
  • PA
  • PA Oblique
  • Lateral “Fan

PA Projection - Hand

• 40" SID
• No Grid
• Pronate hand with palmar surface on IR
• Spread fingers slightly
• CR: 3rd MCP Joint

Evaluation Criteria for PA Projection - Hand

• Entire hand and carpals demonstrated
• Center of field at third MCP joint
• No rotation of phalanges or metacarpals
• Exposure factors

PA Oblique Projection - Hand

• 40" SID
• No Grid
• Pronate hand on IR
• Rotate entire hand and wrist laterally 45˚ with digits parallel to IR (support with a radiolucent sponge if necessary)
• Separate all digits
• CR: 3rd MCP Joint
• Only allow thumb & fingertips to touch the IR if digits are not of interest
• This position is used to open up the carpal joints for better visualization.

Test your knowledge on the anatomy of the hand with this quiz. Explore the structure of the phalanges, metacarpals, and carpals, as well as the different joints involved. Ideal for students studying human anatomy or biology.