To identify and qualify the evidence of published studies evaluating whether rapid maxillary expansion (RME) treatment modifies the head and cervical posture in growing patients.

Electronic database searches were conducted until January 2021 using PubMed/MEDLINE, Embase, Web of Science, Cochrane Library, and LILACS. Grey literature was explored using ClinicalTrials, OpenGrey and Google Scholar. Trials involving participants who underwent RME were included. Risk of Bias (RoB) assessment was conducted using the Cochrane tool for randomized trials and the Methodological Index for Non-randomized Studies (MINORS) for non-randomized trials. The certainty level of evidence was evaluated through the Grading of Recommendations, Assessment, Development and Evaluation tool (GRADE).

Six clinical trials were included. The RoB scores had unclear and high risks of bias. Low certainty of evidence suggested that the effects following RME include a decrease in craniocervical angulation, as well as a very low certainty of evidence for a decrease in head elevation, an increase in cervical lordosis, and an increase in the inclination of the cervical spine.

There is low and very low evidence that RME alters the head and cervical posture in growing patients. Further investigation regarding long-term effects, possible changes due to somatic growth, and clinical relevance is needed.