Oswestry Disability Index
To The Editor: I welcome the publication of the 5-year follow-up of the ProDisc FDA investigational device exemption (IDE) study9,10 (Zigler JE, Delamarter RB: Five-year results of the prospective, randomized, multicenter, Food and Drug Administration investigational device exemption study of the ProDisc-L total disc replacement versus circumferential arthrodesis for the treatment of single-level degenerative disc disease. Clinical article. J Neurosurg Spine 17:493–501, December 2012; Zigler JE, Glenn J, Delamarter RB: Five-year adjacent-level degenerative changes in patients with single-level disease treated using lumbar total disc replacement with ProDisc- L versus circumferential fusion. Clinical article. J Neurosurg Spine 17:504–511, December 2012). What I do not welcome is the use of the term “Oswestry Disability Index” (ODI) in relation to the outcome measure used in this study. “ODI” is used without any references at all in the paper on adjacent-level changes,10 nor are there any references in that paper to the main 5-year outcome paper, 9 which precedes it, so the reader may be forgiven for believing that the outcome measure used was a fully validated version of the ODI.