This protocol paper is generated following the PRISMA-P guidelines. A completed copy of the PRISMA-P checklist is provided (Additional file 1).
Eligibility criteria:
Study inclusion will be conducted based on the eligibility criteria outlined in the following Population-Intervention-Comparator-Outcomes-Study design (PICOS) criteria.
Population:
All adult patients ≥ 16 years of age with chronic pain located to the coccyx are considered eligible for inclusion.
Interventions:
Interventions of interest are those of any conservative, interventional or surgical nature described in any eligible paper. The interventions of interest are not further specified, due to the risk of excluding novel treatments not widely investigated. Papers excluded as case reports will be noted and commented in the discussion section if these concern an intervention of a newer date, not otherwise addressed in the papers included for data analysis.
Comparator:
The authors argue that a comparator is not applicable due to the nature of this study. This is due to the sequential nature of the treatment options for coccydynia. Steroid blocks are typically not applied without prior attempts at conservative treatment, just as surgical intervention is not performed without prior attempts of interventional treatment.
Outcomes:
Outcomes of interest are patient-reported outcome measures, including measures of pain (e.g. VAS-score), quality of life (e.g. EQ-5D), disability (e.g. ODI), work absenteeism, complications to intervention and patient-reported bettering.
Study type:
Studies to be included are any original peer-reviewed literature of randomized control trials, cohort studies or case-series available in full text, both retrospective and prospective, containing more than five patients with coccydynia. Reviews, meta-analyses, opinions and commentaries are excluded, as well as studies involving less than six patients with coccydynia, which will be classified and excluded as case reports.
Language:
Papers in the English, Danish, Norwegian, Swedish, Serbian, Croatian, Bosnian and Spanish language are included.
Exclusion:
Studies that do not meet the eligibility criteria outlined through PICOS are to be excluded, counting animal studies and studies addressing evaluation of technical equipment, studies including patients of less than 16 years of age, studies without treatment outcome (e.g. studies of etiology), studies of acute coccydynia or those with coccydynia reported with a duration less than two months and studies solely concerning secondary coccydynia as a complication to another condition (mimics of coccydynia, e.g. cancer-derived pain and infectious-derived pain).
Secondary coccydynia also includes pain derived from previous surgery in the ano-rectal area. This includes prior coccygectomy, surgery for pilonidal cysts, ano-rectal surgery, as well as any other surgical intervention in the area. This is due to the risk of developing granulation tissue, adhesions, chronic inflammation and possibly a change in elasticity of the tissue surrounding the os coccygis, which, over the course of time, can lead to secondary coccydynia.
Information sources:
A systematic literature search will be conducted in EMBASE.com, PubMed.com, Scopus and Web of Science bibliographic databases from their inception to January 17th 2020, alongside a search for published studies and Epubs ahead of print in journals with relevance to spine surgery, such as Spine, EuroSpine, European Spine Journal, Global Spine Journal, the Spine Journal, International Orthopedics and Journal of Bone and Joint Surgery.
Furthermore, reference-lists and citations of included studies will be searched in order to identify other relevant papers. Finally, a cohort of non-published data from DaneSpine[10] will be included in the review.
The search will be conducted using index-words related to the coccyx and coccydynia. Examples of such are attached (Additional file 2). An experienced librarian, affiliated to the Faculty of Health at Aarhus University, will be consulted for guidance in designing the search.
Screening:
Papers will be screened using both EndNote- and Covidence software for duplicates, following a screening using Covidence software including or excluding papers according to their eligibility outlined through PICOS.
The screening will be done by two authors independently, involving a third author in case of disagreement. Addressing possible inclusion bias, a pilot test of 50 papers will be conducted. Papers will primarily be excluded based on title and abstract only, followed by a full text screening. In cases where initial screening cannot be performed due to the abstract not being available, the full text will be obtained. In order to do full text screening, a thorough search for available full texts will be conducted, should a paper not already be accessible through the reference managing tool.
Risk of bias evaluation:
To assess quality and bias, two authors (MMJ and SM) will independently evaluate all eligible papers, followed by an attainment of consensus, using Covidence software. Cochrane Risk of Bias Tool will be used to assess for the presence and extent of bias in Randomized Clinical Trials (RCTs). As this systematic review will also include observational studies, each study will be scored using Strengthening the Reporting of Observational studies in Epidemiology (STROBE) checklist.
Data extraction:
Data extraction will be performed using the data extraction form within Covidence. Extraction will be done independently in duplicate by two authors (MMJ and SM), including a third author in case of disagreement, and compared when completed.
Data synthesis:
The included studies will be divided into groups based on treatment strategy in order to perform meta-analysis. Data from RCTs will be evaluated separately using RevMan if treatment strategies can be pooled. Data from Observational studies will be analyzed using weighted pool averages, if the amount of studies included for each treatment strategy is adequate. In case of inadequate data for meta-analysis, or if data is not suited for meta-analysis, a qualitative estimation will be made, by summarizing the study findings. In the case of several eligible studies on a given treatment option, a study will be included in data synthesis corresponding to the applicability of its reported outcome measure.
The primary outcome measure for comparing and evaluating the efficacy of the different treatment options are validated pain-scores, e.g. VAS-score at last follow-up compared to baseline. In studies that report a qualitative measure of outcome, i.e. “improved”, “no change”, “worse”, the authors will record the proportion of patients reporting each outcome for each study by consensus; considering that some studies may use a different terminology, i.e. “better”,” unchanged”, worse. Secondary outcome measures are measures of disability, e.g. Oswestry Disability Index (ODI), quality of life, e.g. EuroQol-5-Domain (EQ-5D), work absenteeism, complications to the treatment and patient-reported effect of treatment.
If any relevant data is missing, the respective authors of the study will be contacted, concerning assessment of the data. If data is inaccessible or insufficient, an estimate will be conducted.