Upper Limb Hands Radiography and Pathology

DP Hand Radiographic Positioning and Image Critique

• Center Point (CP): The central ray is directed at the head of the $3^{\text{rd}}$ metacarpal.

• Field of View (FOV): The image must include the entire hand, skin margins, all distal phalanges, metacarpals, carpal bones, and at least $1"$ of the distal radius and ulna.

• Angulation Assessment:

  • To confirm correct angulation, the Interphalangeal joints (IP) and Metacarpophalangeal joints (MCP) must appear open.

  • The shafts of the bones should not appear foreshortened.

  • This indicates the patient placed the palmar aspect of the hand flat against the image detector (IM) with no flexion of the fingers.

• Angulation Errors (Flexed Fingers):

  • If the patient flexes their fingers and lifts the palm off the detector, the distal and middle phalanges will appear foreshortened.

  • The IP and MCP joints will appear closed.

  • The distal, middle, and proximal phalanges of each finger will superimpose on each other.

• Rotation Assessment:

  • Correct positioning requires equal concavity on both sides of each phalanx.

  • There should be no overlap between the metacarpals or the phalanges.

  • This confirms the hand is flat on the detector and not tilted or rotated to either side.

• Rotation Errors (Hand Rotated):

  • If the hand is rotated (e.g., to the left with the thumb lifted off the detector), the phalanges and metacarpals will show unequal concavity, where one side appears straight while the other appears curved.

  • While there may be no overlap of fingers, the concavity difference confirms rotation.

Oblique Hand Radiographic Positioning and Image Critique

• Center Point (CP): The central ray is directed at the head of the $3^{\text{rd}}$ metacarpal.

• Field of View (FOV): Inclusion of skin margins, distal phalanges, all metacarpals, carpal bones, and $1"$ of the distal radius and ulna.

• Angulation Assessment:

  • There should be no foreshortening of the shafts of the phalanges or metacarpals.

  • Note that the IP and MCP joints will typically appear closed due to the rotational position, which is expected.

  • The fingers must remain parallel to the detector while the hand is rotated.

• Angulation Errors (Fingers Angled Toward Detector):

  • If the finger is angled toward the detector, significant foreshortening occurs. For example, the distal and middle phalanx of the $2^{\text{nd}}$ phalange may be so foreshortened that the distal phalanx is barely visible.

• Rotation Assessment:

  • The hand should be rolled externally by exactly $30^{\circ}$.

  • The metacarpals and phalanges should display concavity on the palmar aspect.

  • The heads of the $3^{\text{rd}}$ to $5^{\text{th}}$ metacarpals should show slight superimposition.

  • The shafts of the $3^{\text{rd}}$ to $5^{\text{th}}$ metacarpals must not be superimposed.

• Rotation Errors:

  • Over-rolled: If the hand is rolled more than $30^{\circ}$, the heads of the $2^{\text{nd}}$ through $5^{\text{th}}$ metacarpals become superimposed, and the shafts of the $3^{\text{rd}}$ to $5^{\text{th}}$ metacarpals almost completely superimpose.

  • Rolled Internally (Wrong Way): Rolling the hand $30^{\circ}$ internally (thumb flat against detector) results in the $5^{\text{th}}$ metacarpal being free from superimposition while other areas are incorrectly oriented.

Lateral Hand Radiographic Positioning and Image Critique

• Center Point (CP): Directed at the head of the $2^{\text{nd}}$ metacarpal. The CP is often displaced medially to ensure the full thumb is included in the FOV.

• Field of View (FOV): Entire hand including phalanges, metacarpals, carpal bones, and $1"$ of the distal radius and ulna.

• Angulation Assessment:

  • MCP and phalangeal joint spaces must be open.

  • Shafts of the bones should not be foreshortened.

  • The lunate carpal bone must appear crescent-shaped on the image.

  • Fingers should be parallel to the detector with the lateral aspect of the hand against the IM.

• Rotation Assessment:

  • The hand is rolled externally by $90^{\circ}$.

  • There should be superimposition of the metacarpal shafts.

  • Phalanx heads should not show double borders.

  • The thumb should appear in a DP (dorsopalmar) orientation with equal concavities of the phalanx.

• Fan Lateral Alternate View:

  • The lateral is taken with the fingers splayed (stretched apart).

  • This view is specifically used to assess individual fingers in a lateral profile and is frequent in cases of Osteoarthritis (OA).

ABCS Assessment Framework for Hand Trauma

• Alignment (A):

  • Joint spaces and the alignment of neighboring bones must be assessed.

  • The distal, middle, and proximal phalanges should sit centrally on their respective metacarpals.

  • Dislocation is identified if a phalanx is displaced laterally or otherwise off-center.

• Bones (B):

  • Evaluate for even translucency and consistent trabecular patterns.

  • Look for breaks in the cortical outline or lucent black lines that indicate fractures.

• Clinical Indications (C):

  • Aligned clinical history with image findings. For example, a patient who punched a wall and has swelling at the base of the little finger warrants a high suspicion of a Boxer's fracture.

• Soft Tissue (S):

  • Assess for soft tissue swelling, which can indicate a subtle fracture or a ligament/soft tissue injury even if a fracture line is not immediately obvious.

Pathologies and Clinical Conditions of the Hand

• Osteoarthritis (OA):

  • This is a common degenerative joint disease prevalent in geriatric patients.

  • Radiographic signs include narrowing of joint spaces, subchondral sclerosis (thickened bone around joints), and osteophytosis (bone spurs and lipping).

• Bennett Fracture:

  • An intra-articular two-piece fracture occurring at the base of the thumb.

  • It is typically caused by forced abduction of the $1^{\text{st}}$ metacarpal.

• Boxer’s Fracture:

  • A fracture located at the neck of the $5^{\text{th}}$ metacarpal.

  • Usually caused by impaction (e.g., a closed fist hitting a solid surface).

  • The fracture line is often transverse but can be spiral. This is typically easier to visualize on an oblique image than a DP image.

• Giant Cell Tumor: Identified as a mass that may be tracked over time (e.g., follow-ups at $12$ months and $24$ months).

• Lupus: A condition affecting the joints of the hand characterized by systemic involvement.

• Polydactyly: A congenital condition involving extra digits. For example, a case in a $2.5\text{-year-old}$ presented with an extra finger and a CT confirmed ulna duplication (two ulnas and no radius).

• Traumatic Amputation: Serious injury, such as those caused by fireworks blasts, resulting in the loss of digits.

Radiographic Artifacts and Development

• Artifacts: Objects that can interfere with the diagnostic quality of the image include:

  • Gloves or rings.

  • Nails (fingernails or metallic nails from trauma).

  • IV lines.

  • Orthopedic hardware, such as ORIF (Open Reduction Internal Fixation) pins or plates from a previous $5^{\text{th}}$ metacarpal fracture.

• Pediatric Development: The hand structure changes significantly through maturation, as seen in radiographic comparisons of a $9\text{-month-old}$, $5\text{-year-old}$, and $9\text{-year-old}$.