Purpose: To evaluate the current status of scientific research on the natural history of frozen shoulder as published in the literature.
Materials and methods: This systematic review was carried out on PubMed data and was guided by PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). Articles had to meet inclusion criteria. The quality of the papers was assessed using a newly developed tool, AMQPP (Assessing the Methodological Quality of Published Papers). The AMQPP score was correlated with the level of evidence rating according to the Oxford Centre for Evidence-Based Medicine. Suitable papers were divided into groups according to the shoulder condition on which they reported. This article focuses on the frozen shoulder.
Results: Seven articles on frozen shoulder met the inclusion criteria. One article was considered to have level 1 of evidence. Three articles had level 3 and the remaining 3 had level 4. Three papers assessed the natural history and the natural course of different forms of stiff shoulder. The others indirectly assessed the natural history by evaluating therapy trends. None of the articles clearly referred to the role of regression to the mean of frozen shoulder specifically.
Conclusion: Spontaneous recovery to normal levels of function is possible and standardised non-operative treatment programmes are an effective alternative to surgery in most cases. However, patients with high risk factors such as diabetes mellitus, and those who suffer chronic symptoms or bilaterally affected, would benefit from early surgery. We also concluded that AMQPP score is simple and straight forward. It works as a quick quality-checking tool which helps researchers to identify the key points in each paper and reach a decision regarding the eligibility of the paper more easily. The AMQPP score is still open for further development.