OBJECTIVE: A study was undertaken to assess the stability of leg alignment reaction to a pressure challenge and its responsiveness to an adjustive intervention.

DESIGN: Prospective, double-blind clinical trial of a diagnostic test.

SETTING: Laboratory: Center for Technique Research.

PARTICIPANTS: Forty-two chiropractic college students, faculty and staff.

INTERVENTIONS: A high-velocity, low-amplitude, short lever adjustment of a single vertebra from among C1 and T3-T7; or a sham adjustment similar to a manual diagnostic pressure test at C1, T3-T7 or T9-T10.

MAIN OUTCOME MEASURES: Leg alignment reactivity: An increase in leg alignment discrepancy (yes or no) following a metered pressure challenge to a vertebra.

RESULTS: On average, stability was poor at T3-T7 (Kappa = 0.04), moderate at C1 (K = 0.47), and fair for sham pressure tests (K = 0.30). Responsiveness: The proportion of positive baseline leg alignment reactions that responded (became negative) to sham adjustment was 95% at T3-T7 and 55% at C1. Further analysis was untenable since too few vertebrae were implicated for an adjustment.

CONCLUSIONS: For the population investigated, the majority of the responsiveness of the leg alignment diagnostic test to a rotatory adjustment appears to be a diagnostic illusion (i.e., background noise unrelated to a treatment intervention). Further research with different subject populations, regions of investigation, leg alignment measurement techniques and vertebral challenge techniques are indicated.

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