This involves having the subject start from a standing position, push up onto the table and recline as straight as possible. The assessor provides a small amount of headward pressure, gently removes inversion or eversion and then reads the length difference at the heel-last line. The leg check is always monitored and checked by a second assessor. A subjective assessment is obtained by palpating bilaterally at the levels of the C1 and C2 vertebrae for pain, tenderness or spasm. Earlier work has demonstrated the reliability of this measure.
Palpation is scored as a number which consists of the sum of qualities at each site.
For example, a subject reporting pain and tenderness at C1 left and spasm at C2 right would be scored as a 3. The presence of no pain, tenderness or spasm would be scored as a zero, while having all three qualities at all four sites would be scored as a 12. The results of the palpation, leg check and x-ray analysis are recorded on a data collection sheet coded for group membership. Next, the adjustment is given. With the Sid Williams Research Instrument, the numbers from the x-ray analysis are given to the computer which determines the direction factors.