OBJECTIVE: To determine the reproducibility of patient positioning on radiographically evaluated static configurations of the human pelvis.

DESIGN: Repeat anteroposterior radiography of the human pelvis was performed in vivo. Comparative examinations were performed after 1 hr in one subject pool. A second sample underwent repeat examination after a mean of 18 days.

SETTING: Outpatient private practice chiropractic clinic.

SUBJECTS: Thirty-seven relatively asymptomatic subjects participated in the experiment.

MAIN OUTCOME MEASURES: Millimetric evaluations were made for leg length inequality, right/left sacral discrepancies and right/left innominate differences. The null hypothesis was that the difference of the measurements from the two radiographs would be equal to zero. A paired t-test was used to analyze if there were any significant differences. The mean measured difference in millimeters and correlation coefficients were also determined for each variable.

RESULTS: Individual variations for several roentgenometric parameters, including leg length inequality and pelvic torsion, did not reach statistical significance (p > .05) although minor millimetric discrepancies were recorded. Correlation coefficients, in most cases, were relatively high.

CONCLUSION: A subject can be reliably positioned for repeat anteroposterior pelvic radiography for both 1 hr and 18-day intervals. The methodology described has applicability to full spine radiography when roentgenometric parameters of the pelvis are scrutinized.

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