Table 1.
Model Parameter Estimates
| Parameter | Estimate | Source |
|---|---|---|
| Quarterly probability of VBT revision | 0.77%a (equivalent to a cumulative 2-year revision probability of 6.02%) | NCT02897453, Hoernschemeyer et al35,39 |
| Quarterly probability of spinal fusion revision (patients with spinal fusion index or revision procedure in previous quarter), Quarterly probability of spinal fusion revision (patients without spinal fusion index or revision procedure in previous quarter) | 0.22%b, 1.69%b (equivalent to a 2-year cumulative revision probability of 3.2%) | Ahmed et al40 |
| Quarterly probability of requiring spinal fusion index procedure for patients in the VBT treatment group (with VBT revision in previous quarter), Quarterly probability of requiring spinal fusion index procedure for patients in the VBT treatment group (without VBT revision in previous quarter) | 1.18%a, 0.19%a (equivalent to a 2-year cumulative probability of spinal fusion following VBT index procedure of 2.5%) | NCT02897453, Hoernschemeyer et al35,39 |
| Preoperative utilities (VBT and spinal fusion) | 0.783 | Aghdasi et al 2020, using SRS-22r to EQ-5D mapping algorithm from Wong et al43,51 |
| Postoperative VBT utility | 0.925 | NCT02897453, using SRS-22r to EQ-5D mapping algorithm from Wong et al39,51 |
| Postoperative spinal fusion utility | 0.875 | Aghdasi et al 2020, using SRS-22r to EQ-5D mapping algorithm from Wong et al43,51 |
| Index VBT cost | $79,231c | See Supplementary Table 3 VBT index procedure cost calculations |
| Index spinal fusion, fusion revision cost (assumed equal in base case) | $45,816d | See Supplementary Table 1 fusion index procedure cost calculations |
| Non-device costs, all procedures | $28,616e | See Supplementary Table 3 VBT index procedure cost calculations |
| Fusion device costs | $17,200 | An independent survey of spinal surgeons in the US; value also aligns with existing fusion costing studies44–47 |
| Index VBT device costs | $50,615c | See Supplementary Table 3 VBT index procedure cost calculations |
| VBT revision device costs | $8,804f | See Supplementary Table 3 VBT index procedure cost calculations |
Notes: aSee Supplementary Table 4. bSee Supplementary Table 2. cSee Supplementary Table 3. dSee Supplementary Table 1. eCalculated by subtracting spinal fusion device costs from index spinal fusion procedure costs, non-device costs assumed same for all procedures. fCalculated assuming requirement of 1 cord in 50% of revisions, and 2 anchors in 50% of revisions.
Abbreviations: EQ-5D, EuroQol 5-Dimension; SRS-22r, Scoliosis Research Society Outcomes 22-Item Questionnaire; VBT, anterior vertebral body tethering.