{ "background": "Health systems strengthening in sub-Saharan Africa requires robust evidence on the adoption of new practices within district-level facilities. However, longitudinal data on the sustained uptake of interventions following initial implementation support is scarce.", "purpose and objectives": "This study aimed to evaluate the long-term adoption rates of a standardised clinical documentation system introduced via a randomised field trial in district hospitals, and to identify institutional factors influencing sustained use.", "methodology": "A longitudinal study was conducted following a cluster-randomised trial. Adoption was measured quarterly over a multi-year period via direct audit of patient records in 24 facilities. The primary analysis used a generalised estimating equations model: $\\logit(P(Y{it}=1)) = \\beta0 + \\beta1 T{i} + \\beta2 t + \\beta3 (T{i} \\times t) + \\gamma X{it}$, where $Y_{it}$ is adoption in hospital $i$ at time $t$, $T$ is treatment assignment, and $X$ is a vector of time-varying covariates. Robust standard errors accounted for hospital-level clustering.", "findings": "Adoption in intervention hospitals peaked at 78% (95% CI: 71, 84) post-implementation but declined to a stable plateau of 52% (95% CI: 45, 58) by the final measurement period. The decline was significantly associated with staff turnover rates (p<0.01) and inadequate supervisory visits.", "conclusion": "The intervention achieved moderate sustained adoption, but decay over time indicates that initial implementation success does not guarantee long-term integration without ongoing institutional support mechanisms.", "recommendations": "Future health systems interventions should embed explicit, funded plans for continuous supervision and capacity building to mitigate the negative effects of staff turnover on adoption fidelity.", "key words": "implementation science, health systems research, sustainability, cluster randomised trial, adoption fidelity, sub-Saharan Africa", "contribution statement": "This paper