To the Editor, We read with great interest the article by Wang et al. [1] titled "Internal fixation of distal tibiofibular syndesmotic injuries: a systematic review with meta-analysis" published on-line in July 2013 in International Orthopaedics. In this meta-analysis, Wang et al. analysed the optimal method for syndesmotic fixation. Four comparisons with traditional metallic screw were identified in terms of bioabsorbable screws, tricortical fixation method, suture-button device and nonfixation in low syndesmotic injuries. The authors concluded that patients with low syndesmotic injuries should be well assessed before fixation determination and that the indication for screw placement in such conditions needs to be further defined. Nevertheless, we have several queries to communicate with the authors.1. The authors have not focused specifically or in any detail on the issue of the completeness of the search strategy report for databases. They just described the retrieval strategy by using the keywords "syndesmosis" or "tibiofibular". We suggest that the authors provide details of the retrieval strategy. 2. The authors defined one exclusion criterion as "study subjects to be less than 20". We are wondering the reason for this exclusion criterion. Among the included studies, the minimum number of subjects was 24 by Coetzee et al. [2] and Pakarinen et al. [3]. Therefore, we suggest that exclusion criteria should be redefined by the authors. 3. We suggest that the authors evaluate the methodological quality of the included studies, which could avoid potential bias in the meta-analysis. Each included study should be independently assessed by two reviewers. Meanwhile, the authors also should clarify how to assess the quality of all included studies and detailed scores for each trial. 4. The authors used a fixed-effects model to pool data in all forest plots (Tables 2-5). However, different effects models may result in different results. Therefore, we would like to know the reason that the authors chose the fixed effects model for all analyses. In our opinion, the authors should pay attention to the I 2 , which is on behalf of heterogeneity. When I 2 was under 50 %, low heterogeneity was assumed, and the fixed-effects model could be used to pool data. Conversely, when I 2 exceeded 50 %, heterogeneity was thought to exist and the effects model should be random.Moreover, further high-quality randomised controlled trials (RCTs) based on larger sample sizes are still needed. We believe that our remarks will contribute to more accurate elaboration of the results presented by Wang et al. Conflict of interestThere is no conflict of interest and the paper has not been submitted elsewhere.

The objective of this meta-analysis by Abdallah et al. [1] was to synthesize evidence from studies that evaluated the association between body mass index and risk of surgical site infection following spine surgery. It is an interesting study. Nevertheless, we have several methodological issues, which we would like to communicate with the authors.1. Authors searched only two electronic databases (Pubmed and Embase) for studies reporting on risk of surgical site infection following spine surgery. Small number of required papers would be an important limitation of the review. We suggest at least three electronic databases should be systematically searched, such as OVID, the Cochrane Central Register, ClinicalTrials.gov and so on. 2. We suggest that the authors should evaluate the methodological quality of the selected studies, which could avoid the potential bias in the meta-analysis. Each included paper could be independently assessed by two reviewers using a standardized electronic form of predefined criteria. And, we would like to know how to solve the problems if there are discrepancies between the two authors. 3. Publication language was limited to English in the meta-analysis. Therefore, the authors should mention the potential importance of language bias in the limitations of their meta-analysis. 4. The authors used a random effect model to pool the data in all the forest plots even if the I 2 value of the heterogeneity was \50 %. As we know, different effect models may result in different results. Therefore, we would like to know the reason that the authors chose the random effect model for all analyses. 5. In the results part, the funnel plot was used to estimate publication bias and the symmetric inverse funnel distribution was obtained. However, it is not appropriate publication bias was assessed for adjusted OR, the number of studies was only six. As we know, a funnel plot should be inspected visually to assess for publication bias, in meta-analyses with sufficient number of studies ([9).Moreover, future studies based on prospective data collection are still needed to confirm the association between increased body mass index and spinal surgical site infection.Conflict of interest None.