Participant demographics and LBP characteristics
Forty (male n = 18) participants consented, aged 13–24 years, mean (SD): age 16.3 (2.7) engaged in 32 (5.3) training hours per week. Fifteen participants (37.5%) reported experiencing current LBP and 33 (82.5%) reported a history of LBP.
Presence of abnormalities in SS (Objective 1)
Seventy-five per cent of participants (males n = 15 aged 14–24, females n = 15 aged 13–20) had abnormalities in the thoracolumbar spine in SS (Table 1).
Altered disc morphology
Twenty-two participants (55%) showed evidence of DDD (Table 1). One spinal level was involved in 8 participants (36.4%), two levels in 12 participants (54.5%) and three levels in 2 participants (9%). In total, 38 discs demonstrated DDD with the majority at T11/12 (23.7%), followed by L5/S1 (18.4%) and T10/11 (15.8%), with 42.1% of six other spinal levels combined (Table 2). At the time of their imaging, 31.8% with DDD had current LBP, with 86.4% reporting a history of LBP.
Seven participants (42.5%) demonstrated VEP changes (Table 1), with T11/12 the level most frequently affected (29.2%) followed by T10/11 (22.9%) (Table 2). The most frequent abnormalities were seen at the superior and inferior aspects of T11 and the superior aspect of T12. The MRI pattern of VEP changes included oedema adjacent to the end plate and a more chronic pattern of end plate irregularity and sclerosis. A notable observation was that participants who presented with DDD also exhibited VEP changes at the T10/11 and T11/12 levels (Table 2).
Eight participants (20%) demonstrated 11 disc herniations (Table 1). Three participants had disc herniations at two levels with the majority of herniations (5/11) at the L5/S1 level. Three of these were generalised disc bulges with the other three characterised as small central protrusions. Other affected levels included T12/L1 (1/11) and L1/2 (2/11) with 3 generalised disc bulges. Two participants had L3/4 involvement (1 central disc protrusion, 1 generalised disc bulge) with 1 participant with L4/5 central disc protrusion (Table 2). None of the disc herniations involved significant nerve root compression.
Posterior element abnormalities
Table 3 shows the distribution and location of spondylolysis and spondylolisthesis.
Pars interarticularis stress reactions were seen in 9 participants (22.5%). Complete pars injuries (stress fracture) were evident in 7 participants (17.5%), all at the L5 level.
Spondylolisthesis was present in 6 participants (15%) all affecting the L5/S1 level. All 6 participants reported a history of LBP, and 2 participants reported current LBP. Bilateral L5 foraminal narrowing was documented in 3 participants.
Facet joint abnormality
Facet joint arthropathy was demonstrated in 6 participants (15%) occurring at L4/5 or L5/S1 levels. Two participants had bilateral facet joint effusions at L4/5 and L5/S1 with another having left L4/5 and bilateral L5/S1 effusions. One participant had a right L4/5 effusion, and one had a left L5/S1 facet joint cyst. Two participants with facet joint arthropathy also demonstrated DDD. One participant with L5/S1 facet joint degenerative changes also had disc height loss at T11/12, L1/2 and L5/S1 levels. One participant with a small facet joint effusion at L4/L5 and L5/S1 also demonstrated L5/S1 disc height loss.
A left L5 perineural cyst and one individual with a minor scoliosis in the mid-lumbar region were identified.
Comparison of MRI positions (Objective 2)
From 30 participants with abnormal scans, 23 had identical scans when imaged in positions of UFP and UEP, i.e. the dynamic examination did not reveal any additional findings. Seven participants demonstrated different MRI findings across imaging positions (5 females, aged 14–20 years). Only one participant had an alteration to disc morphology displaying a more prominent L5/S1 disc protrusion in UEP and less prominent in UFP.
Six participants had alterations to the posterior element abnormalities including the degree of fluid within the facet joints, spinal alignment secondary to the spondylolisthesis and the size of the pars defect. From these six, four participants had increased fluid in the facet joints in UFP. Pars injuries were clearer in two participants with one having an increase in anterolisthesis in the UFP and UEP compared to SS (Table 4).
Two other participants included one with a very small amount of fluid in the facet joint with a pars fracture that is difficult to appreciate in SS. An increase in the volume of fluid in the facet joint was seen, and the pars fracture became more clearly visible in UEP. In UFP, there was also an increase in the degree of facet joint fluid, but the pars fracture was not visible (Fig. 1a, b and c).
The other participant had DDD with loss of disc height and hydration, and a grade 1 spondylolisthesis, which clearly visualised in SS. In UFP, the degree of anterior translation was visible as a grade 2 spondylolisthesis (Fig. 2a and b).