Radiological Cut-Off Values for Patient Selection in Intravertebral Cage Augmentation for Osteoporotic Vertebral Fractures: A Preliminary Study

Objective: Transpedicular intravertebral cage augmentation is a less invasive alternative to corpectomy for osteoporotic vertebral fractures (OVFs) with neurological deficits. However, because the intravertebral cage depends on the residual vertebral shell for support, objective criteria for patient selection remain undefined. This study aimed to identify preoperative cutoff values predictive of mechanical failure.Methods: Twenty-four patients who underwent transpedicular intravertebral cage insertion with posterior instrumentation for OVFs or Kümmell disease were divided into a mechanical complication (MC) group (n = 9) and a non-MC group (n = 15). Receiver operating characteristic curve analysis was performed to determine preoperative cutoff values.Results: The MC group had a lower preoperative index height (13.9 ± 4.2 mm vs. 16.5 ± 2.9 mm; p = 0.043) and a greater pelvic incidence (PI)–lumbar lordosis (LL) mismatch (33.1 ± 17.3° vs. 19.0 ± 11.7°; p = 0.026) than the non-MC group. A preoperative index height of ≤12.7 mm (area under the curve [AUC]= 0.756, specificity = 1.000, p = 0.003) and a PI–LL mismatch of ≥22.9° (AUC = 0.756, odds ratio, 12.0, p = 0.033) were significant predictors of mechanical failure. All patients with an index height of ≤12.7 mm experienced failure. The MC group achieved a greater height restoration ratio (47.4% vs. 22.7%; p = 0.017) but reached a similar postoperative height (~20 mm, p = 0.811), with a strong inverse correlation between preoperative height and restoration ratio (r = −0.804, p < 0.001). Only the MC group showed a significant loss of correction during follow-up (p = 0.020).Conclusion: A preoperative index height of ≤12.7 mm and a PI–LL mismatch of ≥22.9° may serve as preliminary thresholds indicating the biomechanical limits of intravertebral cage augmentation. In severely collapsed vertebrae, the degree of correction required may exceed what the intravertebral cage can sustain, and these patients may therefore benefit from corpectomy.