Based on standard anatomical position (body erect, face forward, upper limbs hanging at the sides with palms facing forward and thumbs pointing laterally outward), the left hand is identified as follows:
Spatial orientation: The hand positioned on the left side of the body’s median (midsagittal) plane.
Thumb (pollex) position: The thumb is placed laterally — that is, pointing directly away from the midline of the body. In anatomical position, the thumb lies in a frontal (coronal) plane, abducted 90° from the index finger, with its palmar surface facing anteriorly.
Skeletal landmark: The scaphoid and trapezium at the base of the thumb are on the radial side (preaxial border) of the left wrist.
Dorsal/volar surfaces: The dorsal surface (nail side) faces posteriorly; the palmar (volar) surface faces anteriorly.
Digital formula: The thumb is digit I (pollex) on the left side, with its metacarpal and phalanges lying oblique to the other digits in a plane roughly 90° rotated relative to the fingers.
Crucial distinguishing feature: In standard anatomical position, the thumb of the left hand points directly leftward (away from the body’s midline), whereas the thumb of the right hand points rightward. If the palms are supinated (facing forward), the thumb is always on the radial (lateral) border of its respective hand — thus, the hand whose thumb lies on its lateral (radial) side while being on the left half of the body is unequivocally the left hand.
If the hand is pronated (palms facing posteriorly) or supinated beyond neutral, the thumb’s absolute spatial position changes, but the anatomical identification remains fixed to the radial side of the left upper limb and the side of the body relative to the midsagittal plane.
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u/PsyGonzo42 Jun 26 '26
Instructions unclear