Abstract:
BACKGROUND : The aim of this retrospective study was to evaluate
the accuracy of bone SPECT (single photon emission computed
tomography)/CT (computed tomography) in diagnosing
loosening of fixation material in patients with recurrent or persistent
back pain that underwent lumbar arthrodesis with pedicle
screws using surgery and clinical follow-up as gold standard
Methods A total of 48 patients (median age 49 years, range
21–81 years; 17 men) who had undergone lumbar spinal arthrodesis
were included in this retrospective analysis. SPECT/
CT results were compared to the gold standard of surgical evaluation
or clinical follow-up. Positive SPECT/CT results were
considered true positives if findings were confirmed by surgery
or if clinical and other examinations were completely consistent
with the positive SPECT/CT finding. They were considered false
positives if surgical evaluation did not find any loose pedicle
screws or if symptoms subsided with non-surgical therapy.
Negative SPECT/CT scans were considered true negatives if
symptoms either improved without surgical intervention or
remained stable over a minimum follow-up period of 6 months.
Negative SPECT/CTscanswere determined to be false negatives
if surgery was still required and loosening of material was found. RESULTS : The median length of time from primary surgery to
bone SPECT/CT referral was 29.5 months (range 12–
192 months). Median follow-up was 18 months (range 6–
57) for subjects who did not undergo surgery. Thirteen of
the 48 patients were found to be positive for loosening on
bone SPECT/CT. Surgical evaluation (8 patients) and clinical
follow-up (5 patients) showed that bone SPECT/CT correctly
predicted loosening in 9 of 13 patients, while it falsely diagnosed
loosening in 4 patients.Of 35 negative bone SPECT/CT
scans, 12 were surgically confirmed. In 18 patients, bone
SPECT/CT revealed lesions that could provide an alternative
explanation for the symptoms of pain (active facet degeneration
in 14 patients, and disc and sacroiliac osteodegeneration
in 7 patients and 1 patient, respectively). Overall sensitivity
and specificity for the detection of loosening were 100 % and
89.7 %, respectively. The positive and negative predictive
values were 69 % and 100 %, respectively. CONCLUSIONS : This retrospective analysis suggests that
bone SPECT/CT bone is a highly sensitive and specific
tool for the exclusion of screw loosening in patients who
present with recurrent low back pain after having undergone
lumbar arthrodesis. In addition, it can identify other
potential causes of recurrent low back pain in this patient
population.
