Retention in pain care and research: a narrative review focused on implanted medical devices

Retention is increasingly recognized as a critical determinant of both trial validity and long-term therapeutic success in patients with implanted medical devices. This review is timely because neuromodulation research continues to expand, while concerns remain regarding attrition, incomplete follow-up, and the limited generalizability of available evidence.

Recent literature indicates that dropout in chronic pain and neuromodulation research is driven by a combination of demographic, psychological, clinical, and structural factors. Pain catastrophizing, low self-efficacy, unrealistic treatment expectations, logistical burden, and dissatisfaction with treatment allocation all contribute to nonretention. Contemporary neuromodulation trials also face additional challenges related to staged treatment pathways, crossover, implantation procedures, and prolonged follow-up, which complicate the definition, reporting, and analysis of attrition. Recent reporting initiatives further highlight persistent inconsistency in participant-flow reporting and missing-data handling in neuromodulation research.

Retention should be viewed not as a secondary logistical issue, but as a shared clinical and research responsibility. Greater emphasis on patient-centered retention strategies, transparent attrition reporting, and rigorous management of missing data is essential to strengthen trial integrity, improve interpretability of neuromodulation evidence, and support durable engagement with implanted device therapy in routine care.