Initial experience with 18F-sodium fluoride (NaF) PET-CT: a viable functional biomarker in symptomatic Os acromiale

Objective: Os acromiale (OA) is a failure of complete fusion of the acromial process. It is usually asymptomatic and discovered incidentally. OA can contribute to shoulder impingement symptoms and rotator cuff tears. 18F Sodium Fluoride (NaF) Positron Emission Tomography -CT (PET-CT) is an emerging and highly sensitive modality for oncological skeletal staging, and can show a variety of non-malignant uptake. We have analysed the relationship between 18F-NaF uptake in OA and associated symptoms of shoulder pain. Methods: Study population included 21 patients (mean age 60.2 ± 12 years; 13 females and 8 males) with OA who underwent PET-CT scan by injecting 2.22 MBq kg−1 of 18F-NaF. The relationship between 18F-NaF uptake and OA as a cause of pain was analysed. A 3-point grading system was used to evaluate uptake of  18F-NaF. Results: In total 27 OA (12 symptomatic and 15 asymptomatic) were enrolled. All symptomatic OA showed focal increase tracer uptake of Grade 2, while asymptomatic OA did not have significant activity Grade 0 (n = 11) and Grade 1 (n = 4). Conclusion: 18F-NaF PET-CT appears to be a useful adjunct in the assessment of symptomatic OA with its particular strength being its high negative predictive value. Advances in knowledge: 18F-NaF PET-CT may be used as an ancillary tool for identifying symptomatic OA  as a cause of shoulder pain in cases where other obvious causes of shoulder pain have been excluded.