Radiography and photogrammetry-based methods of assessing cervical spine posture in the sagittal plane: A systematic review with meta-analysis.

Background: There are numerous radiography and photogrammetry-based methods of assessing the cervical spine posture in the sagittal plane. The choice of instrument should be based on scientific parameters such as validity and reliability, thus avoiding restrictions to the applicability of the instrument.

Research Question: What radiography and photogrammetry-based methods used to assess the cervical spine posture in the sagittal plane are valid and/or reliable?

Methods: Systematic searches were conducted following Meta-analysis of Observational Studies in Epidemiology guidelines. Methodological quality was assessed according to the Brink & Louw appraisal tool.

Results: Twenty-one studies were included in the qualitative analysis. Twenty different methods of calculating cervical spine posture in the sagittal plane were found. Two studies included validation measures, 16 studies assessed inter-rater reliability, and 17 studies assessed intra-rater reliability. Fourteen studies were included for the quantitative analysis. The meta-analysis shows that the cervical arrow and cervical lordosis photogrammetry-based methods present very high intra-rater reliability. In radiography, the meta-analysis also showed that the Cobb method (inferior C2 - inferior C7), Cobb method (middle C1 - inferior C7), absolute rotation angle, and Gore angle (C2-C7) present very high inter-rater reliability, and the Cobb method (inferior C2 - inferior C7) and absolute rotation angle present very high intra-rater reliability.

Significance: This systematic review presents an overview of the methods used to assess cervical spine posture and the respective information on validity and reliability. This panorama facilitates the choice of method when conducting radiography or photogrammetry-based assessment of the cervical spine in the sagittal plane. In addition, it shows the need for new studies that investigate the accuracy and precision of these methods for their possible use in larger studies.