Loss to Follow-up in Randomized Controlled Trials on Elbow Pathology: A Systematic Review and Meta-Analysis.

INTRODUCTION

Loss to follow-up (LTFU) is a well-recognized source of bias in musculoskeletal research and may compromise the validity of randomized controlled trials (RCTs). Patients lost to follow-up may have different, often worse, outcomes, potentially leading to overestimation of treatment effects. Despite improved reporting guidelines, LTFU remains inconsistently reported in orthopaedic literature. This study aimed to assess the rate of LTFU in RCTs focusing on elbow pathology and to identify factors associated with LTFU.

METHODS

A systematic review was conducted according to PRISMA guidelines. PubMed, Embase, Cochrane Central, and Web of Science were searched for RCTs published between January 2020 and July 2025. Studies on elbow pathology with a minimum follow-up of six months, published in English or Dutch and in Q1 or Q2 journals, were included. Data extraction included study characteristics, follow-up-related variables, and patient characteristics. The primary outcome was the LTFU rate. Descriptive statistics and forest plots were used to explore potential associations.

RESULTS

A total of 44 RCTs including 3,012 patients were analyzed. The mean LTFU rate was 12.1% (range 0-35.6%), with follow-up durations ranging from 6 months to 2 years. No associations were found between LTFU and age, gender, type of intervention, type of pathology, traumatic vs. non-traumatic pathology, follow-up duration, study location, type of hospital, funding source, or journal ranking. A higher number of follow-up moments per month was associated with lower LTFU rates. Reporting of several variables, including factors related to trial conduct, patient characteristics, and reasons for LTFU, was often incomplete.

CONCLUSION

This systematic review found a mean LTFU rate of 12.1% in RCTs on elbow pathology, consistent with the commonly assumed 10% attrition rate. Most factors were not associated with LTFU, although more frequent follow-up was linked to fewer dropouts. Incomplete reporting remains a key limitation and should be improved to strengthen future research.

LEVEL OF EVIDENCE: Level II, Systematic Review, Research Methodology.