Abstract
BACKGROUND CONTEXT[18F]-sodium fluoride (NaF) PET/MR is a modern diagnostic modality for imaging increased bone turnover. Its merits in detecting painful facet joint osteoarthritis in patients with lumbar back pain are unknown. PURPOSETo perform a prospective randomized controlled study investigating [18F]-NaF PET/MR for detecting painful facet joints in comparison to the standard of care (SOC), including clinical examination and conventional MRI. STUDY DESIGN/SETTINGRandomized controlled clinical study. PATIENT SAMPLEThirty-nine patients. OUTCOME MEASURESVisual analog pain scale (VAS) before and at several time points after facet joint infiltration. METHODSPatients with low back pain and suspected facet joint osteoarthritis underwent lumbar [18F]-NaF PET/MR, besides conventional MRI and clinical examination. After randomization, they either received local anesthetics/ corticosteroid infiltration of facet joints as defined by clinical examination and conventional MRI (SOC), or according to the hot spots on PET/MR. VAS was documented at 15 minutes, 1 day, 1 week and 1 month after infiltration. Thirty-nine patients underwent PET/MR before the study was stopped due to new Good Manufacturing Practice requirement and new regulations by radiation protection authorities limiting staff radiation exposure during the production of this radiotracer. RESULTSSignificant pain reduction compared to baseline was shown at every timepoint in both groups, except at 1 month after infiltration in the SOC group. Pain levels did not differ between SOC (n=17) and PET/MR patients (n=12) before infiltration and at 15 minutes, 1 day, 1 week and 1 month after infiltration. No significant correlation was detected between the sum of the PET/MR activity and the initial pain scores or relative reduction of pain after 15 minutes.The constructed study groups of patients with infiltration of all facet joints being PET/MR-positive (n=18) had significantly less pain after 1 months than patients with infiltration in PET/MR-negative facet joints (n=11) (VAS: 4 [0, 9] vs. 7 [2, 10], p=.046). CONCLUSIONSThere is no correlation of pain to NaF activity nor a relevant superiority of [18F]-NaF PET/MR for identification of painful facet joints compared to the standard of care.
Highlights
Facet joint osteoarthritis is a frequent finding in patients with chronic low back pain, leading to selective treatment, such as facet joint infiltrations with local anesthetics and corticosteroids [1]
In the standard of care (SOC) group, the facet joints to be infiltrated had already been selected at the initial consultation based on the clinical examination and morphological signs of facet joint arthropathy on conventional MRI without knowledge of PET/MR results
17 patients could be recruited for the SOC group and 12 patients for the PET/MR group for the primary group analysis, revealing no significant differences in age, gender and initial pain score between both groups (Table 2)
Summary
Facet joint osteoarthritis is a frequent finding in patients with chronic low back pain, leading to selective treatment, such as facet joint infiltrations with local anesthetics and corticosteroids [1]. Improved imaging modalities that more reliably detect painful facet joints may result in more appropriate utilization of facet joint injections Hybrid imaging techniques such as SPECT/CT, PET/CT and PET/MR are promising diagnostic modalities since they combine anatomical with functional information. Up to date, there are no randomized controlled studies comparing [18F]-NaF PET/MR with conventional modalities such as MRI combined with clinical examination to detect painful facet joints. In the SOC group, the facet joints to be infiltrated had already been selected at the initial consultation based on the clinical examination and morphological signs of facet joint arthropathy on conventional MRI without knowledge of PET/MR results. All patients were injected with a standardized dose of 1.5 MBq per kg body weight (max. 100 MBq) of [18F]-NaF
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