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# Table 1
**Abbreviations and definitions for measurement parameters**

Measurements & calculations | Definitions of measurement parameters | Details of measurement execution |
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Length measurements
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Anterior intervertebral height (AIVH) | Distance between anterior-superior and anterior-inferior corners at vertebrae located at relevant intervertebral disc | OsiriX ´length-tool` between most anterior point at superior corner and most anterior corner at inferior corner (Figure 1: a-b) |

Posterior intervertebral height (PIVH) | Distance between posterior-superior and posterior-inferior corners at vertebrae located at relevant intervertebral disc | OsiriX ´length-tool` between most posterior point at superior corner and most posterior corner at inferior corner (Figure 1: c-d) |

Intervertebral disc length (IVDL) | Distance between anterior and posterior boundaries of intervertebral disc | OsiriX ´length-tool` between midway of AIVH and midway of PIVH (Figure 1: f-g) |

Anterior disc material length (ADML) | Distance between anterior and posterior boundaries of anterior herniated disc material | OsiriX ´length-tool` between most anterior located boundary of anterior disc material and midway of AIVH. Linear continuation of IVDL (Figure 1: e-f) |

Posterior disc material length (PDML) | Distance between anterior and posterior boundaries of posterior herniated disc material | OsiriX ´length-tool` between midway of PIVH and most posterior located boundary of posterior disc material. Linear continuation of IVDL (Figure 1: g-h) |

Antero-posterior dural sac length (ADSL) | Distance between anterior and posterior boundaries of dural sac | OsiriX ´length-tool` between most posterior located boundary of posterior disc material and most posterior located boundary of dural sac. Linear continuation of PDML (Figure 1: h-i) |

Cross-sectional area (CSA) calculations
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CSA of anterior intervertebral height (CAIH) | Sum of areas estimated by the product of length measurements of anterior intervertebral height, slice thickness, and inter-slice gap distance (Figure 2a) | Calculation of CSA using all slices for AIVH length measurements. (Additional file 2: Calculating software) |

CSA of posterior intervertebral height (CPIH) | Sum of areas estimated by product of length measurements of posterior intervertebral height, slice thickness, and interslice gap distance (Figure 2c) | Calculation of CSA using all slices for PIVH length measurements. (Additional file 2: Calculating software) |

CSA of intervertebral disc (CIVD) | Sum of areas estimated by product of length measurements of intervertebral disc, slice thickness, and interslice gap distance (Figure 2b) | Calculation of CSA using all slices for IVDL length measurements. (Additional file 2: Calculating software) |

CSA of anterior disc material (CADM) | Sum of areas estimated by product of length measurements of anterior disc material, slice thickness, and interslice gap distance | Calculation of CSA using all slices for ADML length measurements. (Additional file 2: Calculating software) |

CSA of posterior disc material (CPDM)s | Sum of areas estimated by product of length measurements of posterior disc material, slice thickness, and interslice gap distance (Figure 2d) | Calculation of CSA using all slices for PDML length measurements. (Additional file 2: Calculating software) |

CSA of dural sac (CDS) | Sum of areas estimated by product of length measurements of dural sac, slice thickness, and interslice gap distance | Calculation of CSA using all slices for ADSL length measurements. (Additional file 2: Calculating software) |

Volume measurements
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Volume of anterior disc material (VADM)s | Calculated volume of anterior disc material, from tracing of sagittal areas in all slices | OsiriX ´pencil-tool` tracing area of anterior disc material anterior of AIVH at all chosen slices. Osirix ´Compute volume…` tool for volume read-out (Figure 3: a) |

Volume of posterior disc material (VPDM)s | Calculated volume of posterior disc material, from tracing of sagittal areas in all slices | OsiriX´pencil-tool` tracing area of posterior disc material posterior of PIVH at all chosen slices. Osirix ´Compute volume…` tool for volume read-out (Figure 3: b) |