Ethical approval and patient consent are not required because this is a systematic review and meta-analysis of previously published studies. The systematic review and meta-analysis are conducted and reported in adherence to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) [21, 22].
Search strategy and study selection
Two investigators have independently searched the following databases (inception to April 2020): PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases. The electronic search strategy is conducted using the following keywords: gabapentin, and arthroscopy. We also check the reference lists of the screened full-text studies to identify other potentially eligible trials.
The inclusive selection criteria are as follows: (i) study design is RCT; (ii) population are patients undergo arthroscopy; (iii) intervention treatments are pregabalin versus placebo.
Data extraction and outcome measures
We have extracted the following information: author, number of patients, age, female, body weight, duration of surgery and detail methods in each group etc. Data have been extracted independently by two investigators, and discrepancies are resolved by consensus. We also contact the corresponding author to obtain the data when necessary.
The primary outcomes are pain scores at 6 h and 24 h. Secondary outcomes include analgesic consumption, dizziness, nausea and vomiting.
Quality assessment in individual studies
Methodological quality of the included studies is independently evaluated using the modified Jadad scale [23]. There are 3 items for Jadad scale: randomization (0-2 points), blinding (0-2 points), dropouts and withdrawals (0-1 points). The score of Jadad Scale varies from 0 to 5 points. An article with Jadad score≤2 is considered to be of low quality. If the Jadad score≥3, the study is thought to be of high quality [24].
Statistical analysis
We estimate the standard mean difference (Std. MD) with 95% confidence interval (CI) for continuous outcomes (pain scores at 6 h and 24 h, analgesic consumption) and odd ratio (OR) with 95% CIs for dichotomous outcomes (dizziness, nausea and vomiting). The random-effects model is used regardless of heterogeneity. Heterogeneity is reported using the I2 statistic, and I2 > 50% indicates significant heterogeneity [22, 25]. Whenever significant heterogeneity is present, we search for potential sources of heterogeneity via omitting one study in turn for the meta-analysis or performing subgroup analysis. All statistical analyses are performed using Review Manager Version 5.3 (The Cochrane Collaboration, Software Update, Oxford, UK).