Discogenic pain in lumbar vertebra : is quantitative assessment of the osteochondral endplates by simultaneous 18F-NaF PET/MRI helpful?

Aims: Discogenic pain due to intervertebral disc (IVD) degeneration contributes substantially towards low back pain (LBP). This study aims to develop novel and non-invasive diagnostic tools by directly comparing the quantitative results of the normal and degenerated osteochondral endplates obtained using simultaneous ¹⁸F-NaF PET/MRI.

Methods: We prospectively enrolled 22 participants with chronic lower back pain from August 2022 to November 2023. We classified all 110 lumbar IVDs (L1/2-L5/S1 in 22 people) into 75 normal IVDs and 35 degenerative IVDs. The T2 relaxation times in the cartilaginous endplate on MRI (T2rt-CEP-MR) and normalized subchondral bone on positron emission tomography (PET) images (SUVmax-SB-PET) of all 110 lumbar IVDs were recorded. To analyze the relationship between the cartilaginous endplate and neighbouring subchondral bone, we employed Pearson correlation coefficient and generalized estimating equation (GEE) models to examine the T2rt-CEP-MR and SUVmax-SB-PET results in normal and degenerative IVDs.

Results: We observed lower T2rt-CEP-MR in the middle location of the disc (p = 0.003) and higher SUVmax-SB-PET in the anterior, middle, and posterior locations of the disc (p = 0.030, p = 0.006, and p < 0.001, respectively) in degenerative IVDs. Regarding the association between the T2rt-CEP-MR of discs and the SUVmax-SB-PET of the neighbouring subchondral bone, we observed a significant correlation (r = 0.211 to 0.328, p < 0.001) in all locations of normal IVDs. Additionally, a significant correlation was observed in the anterior and middle locations of the degenerative IVDs, and a marginally significant correlation was observed in the posterior region of the degenerative IVDs (r = 0.159, p = 0.060).

Conclusion: Simultaneous ¹⁸F-NaF PET/MRI is a novel and reliable technique for evaluating the osteochondral endplate. The differences in quantitative results could help clinicians to establish an impression of discogenic pain. A spatial relationship exists between the biochemical changes within discs and subchondral bone metabolism.