D9 Postural Analysis

Topic

Postural analysis quantitatively evaluates segmental alignment and load distribution in a static posture using photogrammetry, a digital plumb line, or optoelectronic systems.

Postural analysis operationalizes postural issues: first, it measures the misalignment angles of each body segment; second, it measures the displacement of the center of mass relative to the line of gravity.

The first value recorded by postural analysis is the misalignment angle: the extent to which each body segment—head, shoulders, pelvis, knees—deviates from the axis it would follow in normal segmental alignment, measured in degrees. The greater this misalignment angle, the further the body segment moves from its ideal position.

The second value is the displacement of the center of mass relative to the line of gravity: the distance the body's center of mass shifts away from the vertical line that would pass through the base of support in a normal posture. The greater this displacement of the center of mass, the further the body moves away from a balanced weight distribution across its various points of support.

The misalignment angles and center-of-mass displacement recorded during postural analysis are precisely the values ​​that determine load distribution and stability: the greater a segment's misalignment angle, the more the body's mechanical lever arms are altered and the more the load distribution across joints changes; and the greater the displacement of the center of mass relative to the line of gravity, the lower the stability with which the body maintains its upright position.

By measuring misalignment angles and center-of-mass displacement, postural analysis converts postural issues into numerical values ​​comparable to normal segmental alignment; this allows for the quantification of how much a person's posture deviates from that normal alignment and the extent to which such deviation compromises load distribution and stability.

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