The Reliability of Biomechanical Mensuration Methods of the Sagittal Cervical Spine in Radiography Used in Clinical Practice: A Systematic Review of the Literature.

Background: The biomedical literature assessing the reliability of mensuration of sagittal cervical spine alignment in radiographs has not been systematically evaluated. This review aims to systematically identify and assess reliability studies on biomechanical assessments of the sagittal cervical spine used in clinical practice. Methods: The study design was registered with PROSPERO (CRD42023402990). Funding was obtained from Chiropractic BioPhysics (CBP) Non-Profit (Eagle, ID, USA). Inclusion criteria involved studies in English with: human subjects, radiography of the sagittal cervical spine, and reliability analysis of biomechanical mensuration of the sagittal cervical spine. Exclusion criteria involved studies with: geometric modeling, animals, cadavers, phantom mannequins, and non-radiographic studies. PubMed, CINAHL, AltHealthWatch, and Web of Science databases were searched from inception through to 24 January 2023. The quality appraisal tool for studies of diagnostic reliability (QAREL) assessed bias risk. Results: We followed the synthesis without meta-analysis (SWiM) according to systematic review guidelines. Scrutiny of the inclusion criteria yielded 51 articles. The results were limited due to the heterogeneity of various mensuration methods (Cobb, posterior tangent, translation measures, etc.) and the incorporation of both manual and digital measured assessments. Other sources of heterogeneity included the quality and type of images used, whether digital or plain film radiographs were used, and the differences in statistical analysis and reporting (ICCs or Pearson correlation coefficients, Cohen's kappa agreement, or Bland-Altman plots). Still, the preponderance of evidence found good-to-excellent reliability. Conclusions: This SROL discovered good-to-excellent intra-examiner reliability for the following biomechanical mensuration methods: intersegmental rotation angles, the thoracic inlet angle, the T1 slope, the C2-C7 posterior tangent method for total cervical lordosis, and the Cobb C2-C7 method for total cervical lordosis. Likewise, using these criteria, we identified good-to-excellent inter-examiner reliability for the following biomechanical mensuration methods: intersegmental rotation angles, the thoracic inlet angle, the T1 slope, translation using the sagittal vertical axis of C2-C7, the C2-C7 posterior tangent method for total cervical lordosis, and the Cobb C2-C7 method for total cervical lordosis.