Pseudarthrosis after lumbar spinal fusion: the role of ¹⁸F-fluoride PET/CT.
OBJECTIVE
Painful pseudarthrosis is one of the most important indications for (revision) surgery after spinal fusion procedures. If pseudarthrosis is the source of recurrent pain it may require revision surgery. It is therefore of great clinical importance to ascertain if it is the source of such pain. The correlation between findings on conventional imaging (plain radiography and CT) and clinical well-being has been shown to be moderate. The goal of this study was to determine the possible role of (18)F-fluoride PET in patients after lumbar spinal interbody fusion by investigating the relationship between PET/CT findings and clinical function and pain.


METHODS
A cohort of 36 patients was retrospectively included in the study after (18)F-fluoride PET/CT for either persistent or recurrent low back pain (18 patients) or during routine postoperative investigation (18 patients) between 9 and 76 months and 11 and 14 months after posterior lumbar interbody fusion, respectively. Sixty minutes after intravenous injection of 156 - 263 MBq (mean 199 MBq, median 196 MBq) (18)F-fluoride, PET and CT images were acquired using an integrated PET/CT scanner, followed by a diagnostic CT scan. Two observers independently scored the images. The number of bony bridges between vertebrae was scored on the CT images to quantify interbody fusion (0, 1 or 2). Vertebral endplate and intervertebral disc space uptake were evaluated visually as well as semiquantitatively following (18)F-fluoride PET. Findings on PET and CT were correlated with clinical wellbeing as measured by validated questionnaires concerning general daily functioning (Oswestry Disability Index), pain (visual analogue scale) and general health status (EuroQol). Patients were divided into three categories based on these questionnaire scores.


RESULTS
No correlation was found between symptom severity and fusion status. However, (18)F-fluoride activity in the vertebral endplates was significantly higher in patients in the lowest Oswestry Disability Index category (i.e. with the worst clinical performance) than in patients in higher categories (p = 0.01 between categories 1 and 2 and 1 and 3). The visual analogue scale and EuroQol results were similar although less pronounced, with only SUVmax between category 1 and 2 being significantly different (p = 0.04).


CONCLUSIONS
We hypothesize that (18)F-fluoride PET/CT may be able to provide support for the diagnosis of painful pseudarthrosis and could serve as a tool to discriminate between symptomatic and asymptomatic pseudarthrosis for revision surgery, as CT defines the consolidation status and PET pinpoints the 'stress reaction' at the vertebral endplates which significantly correlates with Oswestry Disability Index score.
Department of Orthopedic Surgery, Maastricht University Medical Center, Postbox 5800, 6202 AZ, Maastricht, The Netherlands. marloes.peters@mumc.nl.
Marloes
M
Peters
Department of Orthopedic Surgery, Maastricht University Medical Center, Postbox 5800, 6202 AZ, Maastricht, The Netherlands.
Paul
P
Willems
Radiology /Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.
Rene
R
Weijers
Radiology /Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.
Roel
R
Wierts
Department of Orthopedic Surgery, Maastricht University Medical Center, Postbox 5800, 6202 AZ, Maastricht, The Netherlands.
Liesbeth
L
Jutten
Radiology /Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.
Christian
C
Urbach
Department of Orthopedic Surgery, Maastricht University Medical Center, Postbox 5800, 6202 AZ, Maastricht, The Netherlands.
Chris
C
Arts
Department of Orthopedic Surgery, Maastricht University Medical Center, Postbox 5800, 6202 AZ, Maastricht, The Netherlands.
Lodewijk
L
van Rhijn
Radiology /Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.
Boudewijn
B
Brans
D005459:Fluorides; D005462:Fluorine Radioisotopes; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D011542:Pseudarthrosis / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000209:etiology*; D012008:Recurrence; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects*; D014057:Tomography, X-Ray Computed
D005462:Fluorine Radioisotopes; D005459:Fluorides
18F-Fluoride PET/CT; Bone metabolism; Interbody fusion; Low back pain; Lumbar spine; Pseudarthrosis