Table 1 Listing of nonrandomized studies described as randomized controlled trials and locations of study design descriptions within each manuscript

Singh et al. [4]

Study design/setting: “This study was a nonrandomized, nonblinded prospective review.”

Patient selection: “We performed a retrospective analysis of…”

Kulkarni et al. [5]

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Materials and methods: “The patients were given the option to decide between MI-TLIF and O-TLIF, the cost of the procedure was a single major deciding factor.”

Discussion: “First, it is a nonrandomized study as the patients were given an option to choose the procedure. A randomized study will provide more convincing, evidence-based results.”

Lee et al. [6]

Study design: “Prospective observational cohort study.”

Materials and methods: “The patients were not pre-selected for either group; the type of operation undertaken was based on surgeon’s and patient’s preferences.”

Discussion: “Firstly, it is an observational cohort comparison study and not a randomized controlled trial…”

Seng et al. [7]

Study design: “Retrospective analysis of prospectively collected data.”

Materials and methods: “This was a matched-pair analysis of patients with prospectively collected data…”

Materials and methods: “The patients were not randomized to the type of surgical procedure, and the decision to perform MIS or open TLIF was surgeon dependent.”

Discussion: “First this is a matched-pair analysis and not a randomized prospective study. The patients were not randomized to the type of surgery, and the decision to perform open or MIS TLIF was surgeon dependent.”

Wang et al. [8]

Study design: “This is a prospective single-center nonrandomized control clinical study…”

Discussion: “There are several limitations in the present study. A randomized controlled trial should be considered to provide convincible evidence-based conclusions in the future.”