Although MRI currently represents the standard of reference for benign orthopedic disease, bone scintigraphy is still frequently used for these indications due to its cost-effectiveness and the high sensitivity to osseous lesions and complete view of the skeleton it provides. However, aside from its inability to visualize the soft-tissue structures of the joints, its major drawback is its low specificity.

SPECT/CT appears to overcome most of the diagnostic limitations of purely nuclear bone scintigraphy, by enabling precise anatomic localization of bone turnover abnormalities.

Lower back pain has a very high incidence in western populations and a vast gamut of differential diagnoses (for a review, see [14]). Disk herniation is not accessible to bone scintigraphy and can only be diagnosed by MRI. Active degenerative disease of the axial skeleton is, however, accompanied by an increase in polyphosphonate uptake and, therefore, amenable to bone scintigraphy (Fig. 2). This applies to osteochondrosis radiologically characterized by disk space narrowing, subchondral sclerosis of the vertebral bodies, osteophytes, and radiological signs of disk degeneration such as the occurrence of gas in the disk—the so-called vacuum phenomenon. More relevant to clinical management is the determination of an active facet’s level of osteoarthritis, as this diagnosis and localization helps in directing topical therapies such as a medical branch block or intraarticular instillation of corticosteroids.

Active facet joint disease can be diagnosed by SPECT/CT: Matar and coworkers reported a frequency of 65% for metabolically active facet joint disease in 72 patients referred for SPECT/CT for workup of chronic neck or back pain [15]. In their retrospective study, SPECT/CT identified potential pain generators in 92% of the study population. Makki et al. reported that 91.1% of 486 patients consecutively studied by SPECT/CT for spinal pain over 7.5 years had at least one abnormality visible using SPECT/CT potentially causing the symptoms [16]. They found a prevalence of 42.8% of subjects with increased uptake in at least one zygoapophyseal joint in their cohort. In a further large retrospective study, Lehmann and coworkers analyzed data from 212 patients referred for spinal SPECT/CT to their department over a period of roughly 4 years [17]. 191 of these subjects had been examined for workup of back pain, with suspicion of abnormal facet joint activity being the most frequent indication at 37% of the total. In 50% of the whole group, pathological uptake was described in at least one facet joint. Most noteworthy, 40% of the whole group had undergone SPECT/CT after prior MRI examinations, and 35% of the subjects referred for differential diagnosis of pain had had prior percutaneous interventions with incomplete response. As recorded on the clinical notes of the treating physician, SPECT/CT findings led to a change in clinical management in 79% of patients, impressively documenting the acceptance and utility of hybrid SPECT/CT imaging.

The evidence presented above suggests that skeletal SPECT/CT might have the potential to guide percutaneous therapy of facet joint arthritis. Additional data on the use of stand-alone SPECT point into this direction as well [18–20]. In a further publication, however, Lehmann et al. analyzed the relationship between the localization of abnormal tracer uptake in the facet joint and the joint percutaneously treated in a group of 74 patients [21]. In 70% of these subjects, site of treatment and SPECT/CT abnormality did not coincide. Furthermore, 46% of subjects had a right versus left discrepancy. This shows that the relationship between the scintigraphic abnormality and the occurrence of back pain is not as straightforward as initially expected. Type of treatment also is a variable that should receive consideration in this context: in a prospective double-blinded outcome study, Ackerman and Ahmad showed that SPECT/CT fared better in predicting pain relief after intraarticular injections of cortisone than after medial branch blocks [22]. Clearly, more evidence from further prospective—ideally, double-blinded—investigations with pain relief as outcome variable would be necessary to establish the value of SPECT/CT for planning local therapies of painful facet arthritis.

Another frequent cause of back pain, in particular in the elderly, is osteoporotic compression fracture of vertebral bodies. Within the first year of occurrence, this condition is metabolically active and can thus be visualized by bone scintigraphy. SPECT/CT may help in localization and also in differentiating them from metabolically active osteochondrosis. Vertebral osteoporotic fractures may be treated by percutaneous vertebroplasty. In a recently published prospective study of 33 consecutive patients with this condition, positive SPECT/CT images predicted clinical improvement in 91% of these subjects as induced by this minimally invasive measure [23]. Furthermore, it identified alternative causes of pain in the subgroup of nine patients for whom the therapy in question had then not been performed. Anecdotal evidence lets one surmise that SPECT/CT might also be helpful in acute spinal traumas and, in particular, in diagnosing stress fractures in bilateral pedicles of the spine, as they can occur in athletes [24].