Response to "Letter to the Editor Regarding "Streamlining the MRI-Derived Vertebral Bone Quality Score for Preoperative Osteoporosis and Osteopenia Screening".

We thank the authors for their thoughtful and constructive comments on our simplified MRI-derived vertebral bone quality score using L1/L2 measurements VBQL1/2. We agree with the authors that multicenter studies incorporating heterogeneous scanners and acquisition protocols are necessary before absolute VBQ cutoff values can be broadly applied. Our study was designed to assess whether VBQ measurement could be simplified from L1-4 to L1/L2 without compromising performance, rather than to establish a universal threshold. VBQL1/2 showed excellent agreement with VBQL1-4 and comparable discrimination for osteoporosis and impaired bone quality. We therefore consider VBQ an opportunistic pre-screening tool rather than a substitute for DXA or quantitative CT. Given the high burden of undiagnosed or untreated osteoporosis in lumbar fusion patients and the limitations of general-population screening criteria, spine-specific strategies may benefit from combining clinical risk factors with opportunistic imaging biomarkers. Ongoing work on inter-scanner reliability and automated MRI analysis may facilitate the larger multicenter validation studies required to validate or refute the clinical utility of VBQ.