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letter to the editor
Response to: Randomized controlled trial of vertebroplasty versus kyphoplasty in the treatment of vertebral compression fractures
  1. Douglas P Beall
  1. Correspondence to Dr Douglas P Beall, Clinical Radiology of Oklahoma, Musculoskeletal Imaging and Interventional, 610 NW 14th Street, Oklahoma City, Oklahoma 73103, USA; db{at}

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I read with interest the manuscript “Randomized controlled trial of vertebroplasty versus kyphoplasty in the treatment of vertebral compression fractures” published in the Journal of NeuroInterventional Surgery.1 Although the authors make some valid scientific points in the article, the study has significant shortcomings that should be recognized.

One of the critical issues with this paper is the lack of inclusion of the statistical power calculations necessary to prove or disprove the null hypothesis. The authors use pain and function (Roland–Morris Disability Questionnaire) as primary endpoints for comparing vertebroplasty (VP) and kyphoplasty (KP). The formula described here is typical for calculating sample size in each group. If the desired power is 80% and the level of statistical significance is 1.96, we can use the value of 1–2.5 as a statistical difference threshold in pain after treatment according to the largest VP versus KP manuscript published to date along with other standard references of measurement.2–4 If the standard method of calculation for each group is used to detect a standard difference in pain there would need to be a minimum of 512 patients in each group—that is, 1024 patients in total. The KAVIAR study calculated that a total of 1234 patients would be necessary to determine an 8.7% difference in their primary endpoint—subsequent radiographic fractures. This patient …

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