Validity of surface markers placement on the cervical spine for craniocervical posture assessment

The objective of this study was to evaluate the ability of a physical therapist to place surface markers on the skin over spinous process of C2, C4, C6, and C7 by evaluating the markers positioning using radiographs. A total of 39 healthy female subjects participated. From 39 subjects, 22 had 2 radiographs taken and 17 had 1 radiograph taken. This study presents the results from the 22 subjects and from all 39 subjects together. The markers used were visible on the radiographs. The surface markers placement was tested by using percentage agreement. The criteria used were based on the direction of palpation. Only the markers placed that presented the center of the markers tip aligned to the tip of the spinous process was considered an acceptable placement. Only one level of agreement was considered. A misplaced marker was measured by its relation with the vertebra above or below. From the 22 subjects, the total percentage of agreement was 87.5%. Of the 12.5% error, 1.7% (3) occurred attempting to find C2; 4.5% (8) for C4; 3.4% (6) for C6; and 2.8% (5) for C7. From the total of 39 subjects, the total percentage of agreement was 87.8%. Of the 12.2% error 1.3% (2) occurred attempting to find C2; 2.6% (4) for C4; 3.2% (5) for C6; and 5.2% (8) for C7. Based on the results from this study, clinicians and researchers should take into account possible errors on surface markers placement on the cervical spine when measuring craniocervical posture using photographs.