18F-Naf PET/CT in pseudarthrosis after anterior cervical discectomy and fusion

Abstract

BACKGROUND CONTEXTPseudarthrosis is a well-known cause of persistent or recurrent pain after anterior cervical discectomy and fusion (ACDF). Numerous radiographic criteria to determine the fusion status has been described in the literature, but their accuracies in clinical practice vary considerably and no one single method has proved superior. Fluorine-18 sodium fluoride (18F-NaF) positron emission tomography/computed tomography (PET/CT), depicting osteoblastic activity, might be useful to identify pseudarthrosis after ACDF. PURPOSETo investigate the ability of 18F-NaF PET/CT to identify pseudarthrosis after ACDF using surgical revision as the reference standard. STUDY DESIGNRetrospective observational study. PATIENTS SAMPLEA total of 30 patients consisting of 40 surgical levels. OUTCOME MEASURESFor each level, the presence or absence of intragraft uptake (InGU) and extragraft uptake (ExGU) were recorded, as well as adjacent segment uptake (ASU). CT part of the scan was rated as “fused” or “non-fused”. Results were correlated to the gold-standard of revision surgery. METHODSWe retrospectively included consecutive patients who underwent revision surgery for suspicion of symptomatic pseudarthrosis after ACDF following 18F-NaF PET/CT performed between July 2019 and march 2023. 18F-NaF PET/CT results were compared with the gold standard of surgical evaluation of the stability of the fusion material. All patients underwent a systematic CT scan to evaluate the success of revision surgery one year postoperatively. We also investigated whether some patients underwent a repeated 18F-NaF PET/CT for persistent or recurrent pain after revision surgery. RESULTSRevision surgery demonstrated pseudarthrosis in 37 levels (93%) and excluded pseudarthrosis in 3 levels (7%). In the pseudarthrosis group (n=37), InGU was observed in all levels (100%) while ExGU was present in only 10 levels (27%). Fifteen levels (41%) with confirmed pseudarthrosis were rated as “fused” on CT scan preoperatively. In the non-pseudarthrosis group (n=3), InGU was observed in two levels (67%) while ExGU was never present. Two levels (67%) were rated as “fused” on fusion CT scan. One year postoperatively, fusion was successfully achieved on CT scan in 39 levels (98%). Seven patients (consisting of eight levels) had been subsequently re-explored by 18F-NaF PET/CT for persistent or recurrent pain following revision surgery. PET/CT did not reveal any uptake (InGU or ExGU) in seven levels, rated as “fused” on follow-up CT scan. PET/CT showed InGU in the only level rated as “non-fused” on CT scan. CONCLUSIONS18F NaF PET/CT may be a useful adjunctive diagnostic tool to detect pseudarthrosis after ACDF surgery, especially in case of high clinical suspicion with standard conventional imaging not suggestive of non-union. In our cohort, all levels (100%) with confirmed pseudarthrosis on revision surgery demonstrated InGU on PET/CT, while 41% of these levels were rated as “fused” on CT scan preoperatively. 18F NaF PET/CT might also be helpful after revision surgery to rule out re-pseudarthrosis and identify the pain generator. These promising data need to be confirmed in larger prospective studies.