Data Extraction and Quality Assessment

Two authors performed the literature search, data extraction, and quality assessment independently in accordance with the inclusion criteria. Discrepancies were resolved by consensus. Extracted data included the location of the study, study design characteristics (RCTs or NRCTs), characteristics of delayed union or non-union (location and time after fracture), patient characteristics (number, age, and sex), treatments in intervention and control groups, and follow-up durations. We applied the seven domains of the Cochrane's Risk of Bias Tool to evaluate the quality of the included RCTs (32), which include criteria regarding random sequence generation, allocation concealment, blinding of participants and personnel, blinding of outcome assessors, incomplete outcome data, selective outcome reporting, and other potential threats to validity. Quality of NRCTs were evaluated with the ROBINS-I checklist (33), which were judged for confounding bias, selection bias, bias in classification of interventions, bias in deviation from intended interventions, bias due to missing data, bias in measurement of outcome, and bias in selection of the reported results.