Interrater agreement and reliability of a palpation method for locating C1 transverse process in the cervical spine

Objectives

To examine the agreement and interrater reliability of a palpation method for locating the C1 transverse processes (C1TP) and the association between personal characteristics with the observed agreement.

Methods

Single-blinded, inter-rater reliability study. Ninety-nine participants (58 women, age 44 ± 10 years, body mass index 26.1 ± 4.3 kg/m², neck disability index = 8.4 ± 7.3 points) were enrolled in this study. Two raters blinded to each other's assessment performed the palpation for locating the C1TP and marked it with invisible ultra-violet ink. A research assistant measured the distance between the skin marks labeled as C1TP. The association between sex, age, body mass index, neck pain intensity and disability on the interrater agreement was verified using a point-serial correlation coefficient.

Results

Absolute and percent agreement for the right and left body sides were 90/99 (90.9 %, 95%CI 83.4 to 95.8) and 96/99 (97.0 %, 95%CI [91.4 to 99.4]), respectively. Interrater reliability was excellent for both right (Gwet's AC1 0.883, 95%CI [0.881 to 0.885]) and left body sides (Gwet's AC1 0.894, 95%CI [0.894 to 0.896]). After adjustment for multiple comparisons, no statistical evidence of correlation was observed for age, sex, body mass index, and NDI with the agreement for location of C1TP (r = −0.206 or lower, adjusted P-value = 0.328 or higher).

Conclusions

The palpatory method for the location of C1TP has excellent interrater agreement and reliability. Age, sex, body mass index, and disability show weak-to-negligible correlation with the agreement for location of C1TP.

Implication for practice

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  A palpation method should be accurate and reliable for being introduced in clinical and laboratory settings

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  This is the first study to report interrater reliability results for locating C1 and the reliability is excellent

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  The result of our study increases our confidence in recommending the location of C1 in clinical practices when performing mobility tests for C0–C1–C2, the great nerve occipital palpation, as a start landmark for suboccipital muscle palpation and when applying direct manual procedures to restore mobility in C1–C2 segments as muscle energy technique, high-velocity low amplitude (HVLA) manipulation and mobilization with movement techniques

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  These results benefit the manual therapist's education process as palpatory skills and surface anatomy are core subjects in manual therapy education, including osteopathy, despite the lack of validation of most palpation methods