Table 1 List of abnormalities and the corresponding grading systems used in this study

Pars abnormality

Ang et al. [17]

Grade 0 = normal, grade 1 = a stress reaction, grade 2a = an active incomplete fracture, grade 2b = a chronic incomplete fracture, grade 3 = active complete fracture, grade 4 = chronic complete fracture

Bone marrow edema

Sims et al. [18]

The severity is calculated from the sagittal STIR sequence. The intensity value of bone marrow at the site of edema is measured using the region of interest tool. This value is then divided by the value of normal bone marrow within the vertebral body at the same level of the pars. This is referred to as the BMO “ratio”

Disc herniation

Mysliwiec et al. [19]

Grading is dependent upon the direction and the magnitude of the disc protrusion. The grading depends on the magnitude of the distance the protrusion extends posteriorly (grading is between 1 and 3), and then follows with the mediolateral location of the protrusion (grade A–C).

Nerve root compression

Pfirrmann et al. [20]

Grade 0 = normal, grade 1 = contact, grade 2 = deviation, or grade 3 = compression

Canal stenosis

Guen et al. [21]

Grade 0 = normal, grade 1 = mild, grade 2 = moderate, grade 3 = severe

Foraminal stenosis

Park et al. [22]

Grade 0 = normal, grade 1 = mild, grade 2 = moderate, grade 3 = severe

Disc degeneration

Pfirrmann et al. [23]

Grade 0 = normal through to grade 5 = severe

Annular fissure

Yes/no answer with location (right, posterior/central or left)

“Yes” or “No”

Modic endplate changes

Modic et al. [24]

“Type 1” (decreased signal intensity on T1-weight images, increased signal intensity in T2-weighted images), “Type 2” (increased signal on T1-weighted images and a slightly hyperintense signal on T2-weighted images), or “Type 3” (decreased signal intensity on both T1- and T2-weighted images)

Schmorl’s nodes

Yes/no answer

“Yes” or “No”

Scheuermann’s disease

Yes/no answer

“Yes” or “No”

Facet joint orientation

Noren et al. [25]

(Adapted method from Noren et al.) Facet joint orientation was measured using a midsagittal line through the vertebral body and the intersecting lines passing over the endpoints of each facet (see Fig. 1).

Facet joint degeneration

Weishaupt et al. [26]

Grade 0 = normal through to grade 3 = severe

Facet synovial cyst

Yes/no answer with location (left/right and infraspinal/extraspinal)

“Yes” or “No” with “Right” or “Left”

Spondylolisthesis

Meyerding [27]

Grade 0 = no spondylolisthesis, grade 1 = 1–25% vertebral slip, grade 2 = 26–50% vertebral slip, grade 3 = 51–75% vertebral slip, grade 4 = 76–100% vertebral slip, or grade 5 = > 100% vertebral slip

Spina bifida occulta

Yes/no answer

“Yes” or “No”