Locating the Seventh Cervical Spinous Process: Development and Validation of a Multivariate Model Using Palpation and Personal Information.

OBJECTIVE: The aim of this study was to develop and validate a multivariate prediction model, guided by palpation and personal information, for locating the seventh cervical spinous process (C7SP).

METHODS: A single-blinded, cross-sectional study at a primary to tertiary health care center was conducted for model development and temporal validation. One-hundred sixty participants were prospectively included for model development (n = 80) and time-split validation stages (n = 80). The C7SP was located using the thorax-rib static method (TRSM). Participants underwent chest radiography for assessment of the inner body structure located with TRSM and using radio-opaque markers placed over the skin. Age, sex, height, body mass, body mass index, and vertex-marker distance (DV-M ) were used to predict the distance from the C7SP to the vertex (DV-C7 ). Multivariate linear regression modeling, limits of agreement plot, histogram of residues, receiver operating characteristic curves, and confusion tables were analyzed.

RESULTS: The multivariate linear prediction model for DV-C7 (in centimeters) was DV-C7 = 0.986DV-M + 0.018(mass) + 0.014(age) - 1.008. Receiver operating characteristic curves had better discrimination of DV-C7 (area under the curve = 0.661; 95% confidence interval = 0.541-0.782; P = .015) than DV-M (area under the curve = 0.480; 95% confidence interval = 0.345-0.614; P = .761), with respective cutoff points at 23.40 cm (sensitivity = 41%, specificity = 63%) and 24.75 cm (sensitivity = 69%, specificity = 52%). The C7SP was correctly located more often when using predicted DV-C7 in the validation sample than when using the TRSM in the development sample: n = 53 (66%) vs n = 32 (40%), P < .001.

CONCLUSIONS: Better accuracy was obtained when locating the C7SP by use of a multivariate model that incorporates palpation and personal information.