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

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.

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.

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).

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.