Reliability and Validity of Non-radiographic Methods of Forward Head Posture Measurement: A Systematic Review.

Forward head posture measurement can be conducted using various methods and instruments. The selection of the appropriate method requires the factors of validity and reliability to be considered. This systematic review reports on the reliability and validity of the non-radiographic methods examined for measuring forward head posture. The review identified relevant studies following a systematic search of electronic databases. The studies were assessed for quality by two independent reviewers using a critical appraisal tool. The studies' data were extracted and assessed, and the results were synthesized qualitatively using a level of evidence approach. Twenty-one studies met the eligibility criteria and were included in the review. Both reliability and validity were investigated for five studies, whereas reliability only was investigated for 17 studies. In total, 11 methods of forward head posture measurement were evaluated in the retrieved studies. The validity of the methods ranged from low to very high. The reliability of the methods ranged from moderate to excellent. The strongest levels of evidence for reliability support the use of classic photogrammetry. For validity, the evidence is not conclusive. Further studies are required to strengthen the level of evidence on the reliability and validity of the remaining methods. It is recommended that this point be addressed in future research.