Instructions for authors

General information
Acta Orthopaedica welcomes all types of original manuscripts within orthopaedic surgery and traumatology from any part of the world. Experimental studies, case reports and technical reports may also be published. Guidelines, perspectives, guest editorials, and letter to the editor may also be considered.

The submitted work must not have been published before in any language or being considered for parallel publication elsewhere. The work must have been read and approved by all authors.

Submit your manuscript
Your manuscript should be compliant with Instructions for authors before submission. Authors may provide the names and email addresses of potential reviewers. There should not be any conflicts of interest between the potential reviewers and authors. The final reviewer selection is ultimately the decision of the co-editor.

Manuscripts should be submitted online at https://www.manuscriptmanager.net/ao.

We encourage the submission of videos via a link to YouTube to summarize, supplement or enhance articles. All videos will undergo peer review. Please include the link in the manuscript.

Review process
Manuscripts of interest are sent to external expert reviewers and most often also to the Statistical Editors.

Acta Orthopaedica applies an open review process; authors’ and reviewers’ names are mutually disclosed, unless a reviewer actively chooses to be anonymous. Reviewers who agree to be named are acknowledged in the published papers.

A high standard of English with American spelling is expected. Language editing will always take place.

Administrative requirements
All documents with original data of relevance to the submitted manuscript should be stored and be retrievable on request for a minimum of 10 years. A data sharing plan should be described in the manuscript. See further information below.

Specific guidelines
Registration of your study
All randomized controlled trials (RCT) and preferably other studies as well should be registered in publicly accessible databases (for example ClinicalTrials.gov) to be considered for publication. Systematic reviews should be registered in Prospero.

Study design
Please adhere to requirements for the design you are using, i.e. a RCT, cohort study, national register study, systematic review and meta-analysis.

Reporting guidelines 
Any submitted study should adhere to a reporting guideline. Ideally, it should be followed already when planning the research project. Please check that you have used the correct one when you prepare the manuscript. Consult https://www.equator-network.org .

Manuscript guidelines
Note the following points:

a. The manuscript should be submitted as a Word file. It should be double line spaced (also the reference list), line numbered and include tables and figures at the end of the manuscript.

b. Limitations on word count:
• Manuscript should not exceed 3,300 words in total (excluding title page, figure and table legends, and references)
• Abstract - maximum 250 words
• Introduction - should not exceed 300 words
• The word counts (Total, Abstract, Introduction) should be added on the title page.

c. Extensive tables, complementary figures, and other explanatory material should be given as Supplementary data which will be available at the end of the article.

The structured manuscript
For more information on what Acta Orthopaedica expects from a research manuscript please read “Guidelines for a structured manuscript: Statistical methods and reporting in biomedical research journals”, from which the information below is retrieved. Please adhere to this article in order to facilitate manuscript handling.

Title page
Acta Orthopaedica prefers titles that are expressive rather than neutral. The title of the paper should identify value to the reader (e.g., be explicit about patients/population, interventions/exposures, and if possible, the major outcome of interest). The research design should be stated in the latter part of the title (e.g., an RCT, a prospective cohort study, etc.).

The first name, middle initial(s), and last name of each author should be given with department affiliations as well as the e-mail of the corresponding author.

Do not provide academic titles for the authors, postal addresses or phone numbers for correspondence: email address only.

Do not provide key words or “level of evidence” on title page.

Authorship: To be an author requires that you fulfil the ICMJE recommendation. A person who has been involved in the study but not fulfilling the recommendations may be mentioned in the acknowledgement.

Abstract
Maximum 250 words in a structured summary form:
• Background and purpose (the problem, motivation for the study)
• Methods
• Results
• Conclusion (strictly on the aim and corresponding to the body of the manuscript)

Mention trial registration in Abstract if the study was appropriately pre-registered.

Introduction
Introduce the topic in short, from an evidence-based point-of-view (i.e., what is already known on this topic without deselecting and omitting references that goes against the researchers’ hypothesis).
Describe the scientific background for the topic including any gaps in knowledge, and the rationale for the current study (i.e., what are the challenges to be addressed).
List aim(s) and/or key objective(s), and, when appropriate, hypothesis.

Methods
The facts given in the Methods section should be structured according to reporting guidelines suitable for the study design (for example STROBE and CONSORT, see above). Below is listed the most common subheadings:
• Study design
• Participants/patients, samples (i.e., eligibility criteria)
• Interventions/exposures (i.e., describe groups of importance for statistical testing)
• Variables and outcome measures (e.g., the primary and key secondary endpoints)
• Sample size and power considerations (i.e., informative even in a retrospective study)
• Patient and public involvement in the research (i.e., did the researchers involve patients as research partners at any/all stages?)

Statistics
Please consult the specific Statistics folder on the web site.

Ethics, registration, data sharing plan, funding, and potential conflicts of interest
Approval by an Ethics committee, when appropriate, should be stated with date of issue and registration number. Describe how participants were informed about the study, and how consent was given.
Availability of pre-registered protocol should be reported like registration number for the registration of the trial in for example ClinicalTrials.gov.
Data sharing plan: For clinical trials that began enrolling participants on or after 1 January 2019 a data sharing plan should be included. Acta Orthopaedica encourages data sharing of also other studies.
Funding should be declared.
Conflicts of interest are reported in a specific document during submission.

Results

Report results according to your prespecified aims and outcomes.

Participant flow as a figure illustrating study flow and attrition. 

Baseline characteristics as a table reporting descriptive statistics for all participants in the intention-to-infer from population (in analogy to the guidance provided for randomized trials).

Main analyses on the primary and key secondary objectives (i.e., Table[s] reporting statistical measures for each group and the difference between them [with 95% confidence intervals]).

Do not give the same data in more than one way. When summarizing the data, always include measures of variability and the number of subjects. 

Descriptive Statistics: Summarize data that are approximately normally distributed with means and standard deviations (SD). Use the form: mean (SD), not mean ± SD. In contrast, summarize data that are not normally distributed (i.e., skewed) with medians and interquartile ranges (i.e., report the points which are 25%, 50% and 75% of the distribution; not just the size of the range): Report the upper and lower boundaries (while the minimum and maximum values are optional). Examples mean (SD) 15 year (3.9), median 1.5 (IQR 0.95 to 1.95).

Inferential Statistics: When reporting estimates (e.g. Means or Proportions) per group, remember to report a measure of precision as well (e.g. Standard Errors, or Confidence Intervals). However, when reporting on differences between groups it is critical to remember that it must (almost always) be reported with 95% Confidence Intervals.

Percentages should not be used if the sample size is significantly less than 100. Give percentages with not more than 2 numerals (except 0). Identify the quantities represented in the numerator and denominator (e.g., the number of men with surgery divided by the number of men capable of surgery).

Give numbers in digits instead of words, even if n < 10 or at start of sentence (4 instead of four, and 4th instead of fourth).

Although not preferred to confidence intervals, if desired, P values should be reported as equalities when possible and to one or two decimal places (e.g., P = 0.03 or 0.22 not as inequalities: e.g., P < 0.05). We do not accept “NS” (previously erroneously used to indicate “Not Significant”); give the actual P value. If necessary, P values should be stated exactly, apart from values less than 0.001, which should be expressed as P < 0.001. Otherwise, P values should be expressed with two significant figures and up to three decimal places. Confidence intervals (usually 95%) be reported with parentheses around the upper and lower limits. Introduce (and define) 95% confidence interval as CI under "Statistics". Examples HR 4.7 (CI 4.3 to 7.3), average  52% CI (43 to 73), translation 0.04 mm (CI –0.01 to 0.01).

Discussion
Start with a statement of principal findings based on the aim/key objectives/hypothesis.

Provide a critical discussion of the results, regarding the quality of the data (selection and information bias) and adequacy of the statistical analysis (confounding bias). It should also assess the relevant literature for or against the findings. Provide a possible explanation of your results. Do not recapitulate your results or other’s results in detail.

Provide the strengths and limitations of the study, and the clinical perspective of it.

Draw conclusions strictly related to the aim/key objectives/hypotheses.

Avoid recommendation unless the manuscript is a recommendation paper.

Author contributions
Describe in short what each author did (initials).

Acknowledgments
Technical help or other assistance may be acknowledged.

References
Try to limit the numbers of references to 25. Exceptions may be for meta-analyses or review articles. Cite original studies or well-conducted meta-analyses. Cite contemporary studies, consider the relevance today if an old work is referred to.

Well established terms and classifications can be used without references given, in order to reduce the number of references.

Number the references consecutively and give their number within parenthesis in the text,

When available, DOI numbers should be added to the references.

For further details regarding references, see https://www.nlm.nih.gov/bsd/uniform_requirements.html#journals.

Tables
Each table should be self-explanatory, with an adequate title and a logical presentation of the data. Abbreviate words in the columns and explain in footnotes. Each column heading for numerical data should include the unit of measurement. Use SI units. Avoid unnecessary decimals!

Figures
A scanned picture or digital photo should usually be about 85 mm (i.e., 1000 pixels) wide with a resolution of 300 DPI (dots per inch), which gives a square picture an uncompressed file size of 4.5 MiB in color and 1 MiB in grayscale.

A black and white drawing or graph may be scanned in 800 DPI bitmap, i.e., 1 bit TIFF. The preferred format is a TIFF-file. The resolution of WEB illustrations (gif) is usually too poor. Color photos should be in CMYK colors.

Highlights, arrows, and letters may be added to digital photos but keep a clean version of the photo for the layout process. Acta Orthopaedica prefers to add these as a separate layer.
For digital graphs, use a graphics program that can export vectorized graphs as EMF, EPS, SVG or PDF files. Avoid frames around diagrams, diagrams with perspective drawing, and bar graphs or histograms (use tables).

Symbols should be consistent throughout a series of figures. Each axis should be horizontally labeled, with a description of the variable it represents. Axes should be equal in length to make the diagrams quadratic. Use sans serif letters (Arial or Helvetica). Make diagrams in color but avoid complex patterns.

Preprint publication
Uploading of your original manuscript to a non-commercial preprint server do not jeopardize consideration for publication in Acta Orthopaedica. We do not consider posting on a preprint server to be duplicate publication.