Background Thoracic kyphosis is reported to increase with ageing. However, this relationship has not been systematically investigated. Peoples’ kyphosis often exceeds 40°, but 40° is the widely accepted cut-off and threshold for normality. Consequently, patients may be misclassified. Accurate restoration of kyphosis is important to avoid complications following spinal surgery. Therefore, specific reference values are needed. The objective of the review is to explore the relationship between thoracic kyphosis and age, provide normative values of kyphosis for different age groups and investigate the influence of gender and ethnicity. Methods Two reviewers independently conducted a literature search, including seven databases and the Spine Journal, from inception to April 2020. Quantitative observational studies on healthy adults (18 years of age or older) with no known pathologies, and measuring kyphosis with Cobb’s method, a flexicurve, or a kyphometer, were included. Study selection, data extraction, and study quality assessment (AQUA tool) were performed independently by two reviewers. The authors were contacted if clarifications were necessary. Correlation analysis and inferential statistics were performed (Microsoft Excel). The results are presented narratively. A modified GRADE was used for evidence quality assessment. Results Thirty-four studies (24 moderate-quality, 10 high-quality) were included (n = 7633). A positive moderate correlation between kyphosis and age was found (Spearman 0.52, p < 0.05, T5-T12). Peoples’ kyphosis resulted greater than 40° in 65% of the cases, and it was significantly smaller in individuals younger than 40 years old (x < 40) than in those older than 60 years old (x > 60) 75% of the time (p < 0.05). No differences between genders were found, although a greater kyphosis angle was observed in North Americans and Europeans. Conclusion Kyphosis increases with ageing, varying significantly between x < 40 and x > 60. Furthermore, kyphosis appears to be influenced by ethnicity, but not gender. Peoples’ thoracic sagittal curvature frequently exceeds 40°. Trial registration The review protocol was devised following the PRISMA-P Guidelines, and it was registered on PROSPERO (CRD42020175058) before study commencement.

Introduction Adolescent idiopathic scoliosis (AIS) is a three-dimensional rotational change in the normal shape of the spine which affects children aged 10 to 18 years. Both the condition and its management can have significant impact on functional ability. Currently, expected restriction in spinal motion is experience based, rather than evidence based, and discussions to inform patient expectations pre-operatively can be difficult. The aim of this review is to evaluate the evidence pertaining to measurement of spinal motion and whether this is altered following surgery, dependent on the anatomical level of surgical fixation in AIS.  Methods/analysis This protocol is reported in line with both PRISMA-P and informed by the COSMIN methodology. Electronic databases will be searched using a two-stage search strategy. The first stage will identify and evaluate the methods used to assess spinal motion. The second stage aims to evaluate the change in spinal motion using these methods based on anatomical level of fixation following surgery along with the measurement properties of those methods, to include the validity, reliability and responsiveness of the methods. Two reviewers will independently screen the search results against eligibility criteria, extract the data and assess the quality of the included studies. Any disputes between the reviewers will be resolved with a third independent reviewer. Data may be pooled where possible; however, this is not expected. The overall strength of the body of evidence will then be assessed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) approach. Patient and public involvement Patients and members of the public will not be consulted in the production of this review, although the review was conceived based on the experiences of the authors when managing this patient population and a need to address patient expectations in pre-operative planning. Ethics, dissemination and data availability No ethical approval required. The final review will be submitted to peer-reviewed journals for publication and disseminated publicly. The datasets used and/or analysed in this review will be available from the corresponding author on reasonable request.  Systematic review registration PROSPERO registration number. CRD42021282264.