Utility of single photon emission computed tomography/computed tomography imaging in evaluation of chronic low back pain.

INTRODUCTION: Abnormal morphologic findings in imaging were thought to explain the etiology of low back pain (LBP). However, it is now known that variety of morphologic abnormalities is noted even in asymptomatic individuals. Single photon emission computed tomography/computed tomography (SPECT/CT) could be used to differentiate incidental findings from clinically significant findings.

OBJECTIVE: This study was performed to define the SPECT/CT patterns in patients with LBP and to correlate these with clinical and magnetic resonance imaging (MRI) findings.

MATERIALS AND METHODS: Thirty adult patients with LBP of duration 3 months or more were prospectively evaluated in this study. Patients with known or suspected malignancy, trauma or infectious processes were excluded. A detailed history of sensory and motor symptoms and neurologic examination was performed. All the patients were subjected to MRI and bone scintigraphy with hybrid SPECT/CT of the lumbo-sacral spine within 1 month of each other. The patients were classified into those with and without neurologic symptoms, activity limitation. The findings of clinical examination and imaging were compared. MRI and SPECT/CT findings were also compared.

RESULTS: Thirty patients (18 men and 12 women; mean age 38 years; range 17-64 years) were eligible for the study. Clinically, 14 of 30 (46%) had neurologic signs and or symptoms. Six of the 30 patients (20%) had positive straight leg raising test (SLRT). Twenty-two of the 30 patients (73%) had SPECT abnormality. Most frequent SPECT/CT abnormality was tracer uptake in the anterior part of vertebral body with osteophytes/sclerotic changes. Significant positive agreement was noted between this finding and MRI evidence of degenerative disc disease. Only 13% of patients had more than one abnormality in SPECT. All 30 patients had MRI abnormalities. The most frequent abnormality was degenerative disc disease and facet joint arthropathy. MRI showed single intervertebral disc abnormality in 36% of the patients and more than one intervertebral disc abnormality in remaining 64% patients. Fifteen of the 30 patients had facet joint arthropathy. 60% of these patients had involvement of more than one level facet joints while 38% had associated inter vertebral disc disease. 83% of the patients with positive SLRT had SPECT and MRI abnormalities. 100% of patients with neurologic symptoms had SPECT and MRI abnormalities.

CONCLUSION: Addition of hybrid SPECT/CT data will help differentiate incidental from significant MRI abnormalities as all patients with LBP have MRI abnormalities and most have MRI abnormalities at multiple sites. Tracer uptake in the anterior part of the vertebral body represents degenerative disc disease. MRI is sensitive and SPECT/CT is specific for facet joint arthropathy. Both investigations are best used complementary to each other.