SPECT/CT in patients with lower back pain after lumbar fusion surgery

Objectives To investigate the incremental diagnostic value of skeletal SPECT/CT over conventional nuclear medical imaging in patients with lower back pain after lumbar fusion surgery.

Methods In 39 subjects with lower back pain after lumbar fusion surgery, three-phase planar bone scans of the lumbar spine including SPECT/CT of that region had been performed after injection of Tc-99m-DPD. Planar scans, SPECT and SPECT/CT datasets were interpreted independently from each other. The findings were classified as (1) no pathological uptake in graft region (N), (2) metal loosening (ML), (3) insufficient stabilizing function (ISF) of the metal implants, (4) adjacent instability (AI), and (5) indeterminate (I) when there was pathological uptake within the graft region not fitting in any of the other four categories.

Results In 31/39 subjects, planar/SPECT disclosed 65 pathological foci of uptake within the graft region, SPECT/CT 59. 5/13 lesions classified as ML by planar/SPECT were reclassified, three as I, one as N, and another one as ISF by SPECT/CT, respectively. 14/30 foci with a planar/SPECT diagnosis of ISF were confirmed by SPECT/CT as such. 9 were recategorized as ML, 3 as N, another 3 as I, and 1 as AI. In 20 foci planar/SPECT led to the diagnosis of AI. SPECT/CT confirmed this diagnosis in 13 lesions. In 5/20 foci the diagnosis changed to N, in 1 to ML, and in 1 to ISF. 2 indeterminate lesions were detected on the planar/SPECT images. 1 of these was confirmed as such, the other 1 reclassified as ISF. 3 lesions were diagnosed by SPECT/CT only and classifed as ISF, AI, or ML, respectively. Overall rate of reclassification was 44.6% (29/65).

Conclusions Due to its significantly higher accuracy compared with planar/SPECT, SPECT/CT should be the conventional nuclear medical procedure of choice in patients with low back pain after lumbar fusion surgery