The following studies have discussed reliability of the x ray marking system used by upper cervical chiropractors.

Grostic & DeBoer. Roentgenographic measurement of Atlas laterality and rotation: A retrospective pre- and post-manipulation study. JMPT 5(2) June 1982

"Under the circumstances presented in this retrospective study, these data tend to show that spinal manipulative therapy altered the position of the atlas in the postulated direction"

Aldis & Hill. Analysis of a chiropractor's data. J and Proc, Royal Soc., NSW. 112:93-99, 1979

Mathematicians statistically analyzed data obtained from an upper cervical chiropractor. Pre- and post-adjustment studies showed significant changes in both laterality and rotation.

Rochester RP. Inter- and Intra-Examiner reliability of the Upper cervical x ray marking system: A third and expanded look. Chir Res J 1994: Vol 3(1)23-31

This study concluded that all aspects of the upper cervical marking procedures are reliable.

Owens EF. Line drawing analyses of static cervical x ray used in chiropractic. JMPT 1992; 15(7);442-9.

"reliability studies exist showing that inter- and intra-examiner reliability are sufficient to measure lateral and rotational displacements of C1 to within + or - 1 degree"

Jackson BL, et al. Inter- and Intra-Examiner reliability of the Upper cervical x ray marking system: A second look. JMPT 1987

"Examination of the data suggest that the reliability (stability over time) for the practitioners is very good. The data on reliability (equivalence over experts) across the practitioners also suggests reliability is very good"