Chronic lower lumbar pain has been associated with elevated bone metabolic activity in the spine. Diagnosis of bone metabolic activity is currently through integrating Positron Emission Tomography (PET) with Sodium Fluoride (¹⁸F-NaF) biomarkers. It has been reported that numerous observable pathologies including lumbar fusion, disc abnormalities and scoliosis have often been associated with increased ¹⁸F-NaF uptake. The aim of this study was to identify what features of lower lumbar shape most strongly correlate with ¹⁸F-NaF uptake. Following a principal component analysis of 23 patients who presented with lumbar pain and underwent ¹⁸F-NaF PET-CT, it was revealed that three modes interpreted as (i) sacral tilt, (ii) vertebral disc spacing and (iii) spine size were the three characteristics that described 88.7% of spine shape in our study population. ¹⁸F-NaF was described by two modes including ¹⁸F-NaF intensity and spatial variation (anterior-inferior to posterior-superior). ¹⁸F-NaF was most sensitive to sacral tilt followed by vertebral disc spacing. A predictive model derived from that spine population was able to predict ¹⁸F-NaF ‘hot-spot’ locations with 85 ± 5% accuracy and with 71 ± 3% accuracy for the ¹⁸F-NaF magnitude. These results suggest that patients reporting with lower lumbar pain and who present with increased sacral tilt profiles and/or reduced disc spacing are good candidates for further ¹⁸F-NaF PET-CT imaging, evidenced by the high association between those shape profiles and ¹⁸F-NaF uptake.

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