Letter to the editor concerning “Transforaminal endoscopic surgery for lumbar stenosis: a systematic review” (Nellensteijn et al.)

Abstract

The recently published systematic review by Nellensteijn et al. [1] has identified seven observational studies on the effectiveness of transforaminal endoscopic surgery for lumbar stenosis. The authors conclude that there is a lack of valid evidence supporting the intervention. We believe that there is more evidence in the literature than that found. Probably, this is due to the authors not including discectomy as a major key word in their search strategy (Table 1). First and foremost, there are at least three systematic reviews that provide additional data. Gibson and Waddell [2] refer to the SCIATICA-Med Trial [3, 4] and a German health technology assessment report [5] identified three RCTs and 12 case series between 1998 and 2004 focusing on endoscopically assisted minimally invasive disc surgery. None of these is duplicated in the Nellensteijn review and, most interestingly, a former review with the same title and group of authors funded by the Dutch Health Care Insurance Board, yielded 8 controlled studies and 31 cohort studies [6]. The 2010 Nellensteijn review has also omitted three key publications on the grounds of lacking focus on lumbar stenosis [7–9] and data from several observational studies focusing on foraminal treatment access [10–15]. These data should at least have been referred to when considering the potential effectiveness of transforaminal endoscopic surgery in a full text evaluation. In addition to criticisms regarding missing data, there is some doubt about whether or not the publication quality assessment criteria used by the authors are appropriate and state of the art, as there are established instruments [16, 17] for this purpose. It should also be noted that the Prisma Flow diagram is not used in the review [18], which further impairs the quality of the paper. We respectfully suggest that there should be better documentation of the study selection process with detailed reporting of reasons for inclusions and exclusions.