Inclusion Criteria:  history of a traffic accident ≥ 3-month history of axial cervical pain after the accident without radicular symptoms whiplash-associated disorder (WAD) severity of Grade II (neck complaint, decreased range of motion of neck, and point tenderness) at first hospital visit failure to respond to physical therapy and oral medication (axial cervical pain of ≥ 3 on the numeric rating scale (NRS 0-10; 0, no pain; 10, worst pain imaginable) ≥ 80% temporary pain relief following a diagnostic block with an intra-articular (IA) injection of 0.3 mL of 2% lidocaine  Exclusion Criteria:  presence of cervical spine fracture, coagulopathy, iodinated contrast allergy, rheumatic disorders, and any uncontrolled medical or psychiatric condition