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Letter to the editor concerning “Does pelvic incidence tell us the risk of proximal junctional kyphosis in adult spinal deformity surgery?” by Buyuk AF, et al. (Eur Spine J [2022]: https://doi.org/10.1007/s00586-022–07214-x)

Dear Editor,

I read with great appreciation the study “Does pelvic incidence tell us the risk of proximal junctional kyphosis in adult spinal deformity surgery?” [1]. The authors aimed to investigate the relationship between pelvic incidence (PI) and proximal junctional kyphosis (PJK) in patients treated surgically for adult spinal deformity (ASD) with fusion from thoracolumbar junction to sacrum. The paper has an elegant rationale and I am sure that will generate new research; however, some methodological fragile reduce the applicability of these results; thus, through a letter to the Editor, my objective is to contribute with the Buyuk et al., and the European Spine Journal.

First of all, we do not know whether the authors used effect size for sample size (how will scientists reproduce this research?). Second, the study presented Minimum Clinically Important Differences (MCID) for Visual analog scale pain and Oswestry Disability Index; however, there is no description of the Standard Error of Estimate (SEM) for the measured differences—this limits the clinical application (how a doctor will know if the MCIDs are not random/systematic errors?).

Third, the authors used Student's t tests for normally distributed variables and Mann–Whitney test for independent samples for continuous variables that were abnormally distributed; however, the tables do not have this information in legends (and tables should be self-explanatory to facilitate clinical interpretability). Fourth, the study did not make a Bonferroni’s correction in the outcome comparisons [2], and besides, it did not add the effect size to the p value—the results of this study are RELEVANT A LOT! However, in surgery, we need to look beyond statistical significance (i.e., we need to analyze clinical relevance); do you agree?

References

  1. Buyuk AF, Dawson JM, Yakel S et al (2022) Does pelvic incidence tell us the risk of proximal junctional kyphosis in adult spinal deformity surgery? Eur Spine J. https://doi.org/10.1007/s00586-022-07214-x

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  2. Curtin F, Schulz P (1998) Multiple correlations and Bonferroni’s correction. Biol Psychiatry 44:775–777. https://doi.org/10.1016/S0006-3223(98)00043-2

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AP-S was involved in conceptualization, data curation, formal analysis, investigation, methodology, project administration, resources, supervision, validation, visualization and writing, review and editing.

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Correspondence to André Pontes-Silva.

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Pontes-Silva, A. Letter to the editor concerning “Does pelvic incidence tell us the risk of proximal junctional kyphosis in adult spinal deformity surgery?” by Buyuk AF, et al. (Eur Spine J [2022]: https://doi.org/10.1007/s00586-022–07214-x). Eur Spine J (2022). https://doi.org/10.1007/s00586-022-07283-y

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