The initial PubMed search yielded 328 citations. Fifteen additional records were identified through the electronic search of other electronic databases, while 5 records were found through a manual search of relevant bibliographies. After duplicates were removed, 341 titles and abstracts were screened for suitability. Most studies (n = 187) were excluded based on the information provided in the title and abstract. One-hundred and fifty-four (n = 154) articles were ultimately retrieved for full-text review. After applying the eligibility criteria, 122 articles were excluded, leaving a final 32 primary studies [17,18,19,20, 30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57] for analysis, as summarised in the PRISMA flowchart (Fig. 1).

Preferred reporting items for systematic reviews and meta-analyses (PRISMA) flowchart

There were only two comparative studies of Mq against the Ilizarov technique [39, 54]. In addition, one report comprised of tibial and femoral infected NUs. The only available data pertaining to tibial NUs were used in the pooled analysis [39]. The remaining articles included single-intervention cohorts of either the Ilizarov method (n = 22) [30,31,32,33,34,35,36,37,38, 40, 42,43,44,45,46,47,48,49,50,51, 53, 56] or the Mq technique (n = 8) [17,18,19,20, 41, 52, 55, 57].

All 32 primary studies comprised of a total population of 1136 patients. The primary studies with single-intervention cohorts included 1085 patients, of whom 865 patients had been treated with the Ilizarov method and the remaining 215 with the Mq technique. The two comparative studies comprised of 51 patients [39, 54]. Twenty-six patients had been treated with DO, while the remaining 25 with the Mq IMT technique. The baseline and demographic characteristics, follow-up details, and sources of clinical diversity of all primary studies are depicted in Tables 1 and 2.

With regards to LoE, there were 2 RCTs (Level I) [43, 54], 5 prospective cohort studies (Level II) [32, 45, 47, 48, 53] 7 retrospective comparative studies (Level III) [17, 31, 39, 40, 46, 49, 50] and 18 retrospective cohort studies (Level IV) [18,19,20, 30, 33,34,35,36,37,38, 41, 42, 44, 51, 52, 55,56,57] (Table 3). The overall risk of bias of both randomised prospective trials [43, 54] was high, according to the RoB2 tool (Table 3). The MINORS score across all primary studies averaged 11 points (median score = 10), ranging from 7 to 20 points. The wide range of scores was undoubtedly due to the design of each primary study (excluding methodological quality), as the studies containing a comparator group received an additional rating (Table 3).

For the meta-analysis of studies directly comparing Mq against Ilizarov, assessment of publication bias was not possible due to the limited number of component studies (n = 2) [39, 54]. For the single-cohort meta-analyses, we generated respective funnel plots for all primary outcomes of interest. The distribution of data-points was symmetrical across the vertical line corresponding to the pooled effect estimate and within the confines of the inverse funnel plot (Fig. 2). In addition, the calculations of Egger’s test and the Begg’s rank test yielded p-values well-above the significance level, indicating that publication bias was unlikely.

Funnel plots demonstrating union rates and infection elimination rates between the Ilizarov and Masquelet groups

Only two studies attempted a direct comparison of Ilizarov against Mq for the management of infected tibial NUs, including 51 patients [39, 54]; one of these studies was a retrospective comparative study reporting on 26 patients (13 patients treated with the DO method and the remaining 13 patients with the Mq technique) [39], while the other study was a RCT including 25 patients (13 of them treated with the DO method and the remaining 12 with the Mq technique) [