Utility of SPECT/CT in Non-Traumatic Osteonecrosis: Revisited with New Insights from a Prospective Diagnostic Study.

Objectives: Bone scintigraphy is a sensitive imaging method to evaluate patients with suspected osteonecrosis. We assessed the diagnostic performance of combined bone single-photon emission computed tomography/computed tomography (SPECT/CT) (CBS) in patients with known rheumatic disease or other connective tissue disorders and clinical suspicion of osteonecrosis compared to magnetic resonance imaging (MRI).

Methods: This prospective diagnostic accuracy study included 70 patients with clinical suspicion of osteonecrosis in any bone who underwent a planar triple-phase bone scan along with a regional SPECT/CT (CBS) and regional MRI. MRI was considered the standard for diagnosing the sensitivity, specificity, predictive values, and accuracy of CBS. Cohen's kappa statistic of the agreement was also calculated.

Results: The distribution of the patients based on the joint regions suspected to have osteonecrosis is as follows: 21 hip, 43 knee, and six ankle. MRI detected osteonecrosis in 30/70 patients. CBS had a sensitivity of 100% (30/70 were detected) and a specificity of 97% (2/40 were false positive). Overall, there was good agreement between the two scans regarding the diagnosis of osteonecrosis (Cohen's kappa statistic = 0.94). In addition to the suspected sites, CBS detected osteonecrosis in 19 additional asymptomatic sites in 13 patients.

Conclusion: The study has demonstrated that CBS, which includes whole-body imaging and SPECT/CT, is highly sensitive in detecting osteonecrosis with accuracy comparable to regional MRI. Its inherent whole-body imaging technique enabled the detection of multifocal osteonecrosis. It can be used as an early investigating modality after routine plain radiography to establish the diagnosis.