Letter to the Editor Regarding “Epidural Transforaminal Infraneural Infiltration Using Corticosteroids in Lumbar Radiculopathy” by Sampaio Júnior et al

To the Editor—We acknowledge Sampaio Júnior et al¹ for addressing a clinically relevant question concerning a procedure widely used in the management of lumbar radiculopathy but still debated in terms of effectiveness and safety.² However, several methodological limitations restrict causal inferences about the effectiveness of the intervention.

The retrospective and uncontrolled design prevents comparison with alternative treatment strategies and limits causal inference. Patients with acute lumbar radiculopathy often have a favorable prognosis, and spontaneous regression of lumbar disc herniation is well documented.^3–5 In addition, all patients were referred to physiotherapy after the procedure, representing an uncontrolled cointervention, while medication use during follow-up was neither reported nor standardized. Therefore, observed improvements may reflect the natural course of the condition, rehabilitation, medication changes, or regression to the mean rather than the infiltration itself.

The selection process also introduces a substantial risk of selection bias. Although 455 transforaminal infiltrations were reportedly performed during the study period, only 99 were included in the final analysis. The reasons for exclusion, losses to follow-up, and whether multiple infiltrations were performed in the same individuals are not reported, limiting transparency and external validity.

The description of the intervention itself is insufficiently detailed to allow adequate interpretation or replication. The authors report the use of different corticosteroids but do not specify doses, injection volumes, or criteria guiding the choice of agent, or the number of injections per patient. Key aspects of safety reporting, including predefined adverse event definitions, methods of ascertainment, surveillance procedures, and responsible assessors, are not described. Without systematic monitoring, reports of “no complications” may reflect underdetection rather than true absence of adverse events.

Baseline functional status was not prospectively assessed. The Oswestry Disability Index for the preprocedure period was retrospectively recalled by patients at the 6-month follow-up, introducing substantial risk of recall bias and compromising the validity of pre-post comparisons. Although the numeric pain rating scale was collected at 10 days, 3 months, and 6 months, only the 6-month results are presented, preventing assessment of the trajectory of pain over time. In addition, defining clinical success as complete pain relief ( score of 0) differs from recommended thresholds for clinically meaningful improvement.⁶

In the statistical analysis, the authors describe the analysis as primarily descriptive, yet inferential results are reported without specification of the statistical tests used and without presentation of effect sizes or confidence intervals. This lack of analytic transparency, together with the absence of a true baseline measurement, limits interpretation of the findings and makes it difficult to assess the precision and robustness of the reported results.

Drawing causal conclusions from observational data requires careful attention to study design. As proposed by Hernán et al, studies aiming to estimate treatment effects should ideally emulate the protocol of a hypothetical randomized trial (target trial emulation).⁷ This framework involves explicitly specifying key elements, including eligibility criteria, treatment strategies, treatment assignment, time zero (start of follow-up), outcomes, follow-up period, and the analytic approach. Adopting these principles would substantially strengthen future research in this area.