Clock-Face Sonography of the Glenoid Labrum: A Pictorial Technical Protocol for Patients Ineligible for MRI/MR Arthrography.

This work presents a standardized 360-degree, clock-face ultrasonographic protocol for comprehensive static and dynamic assessment of the glenoid labrum. The protocol translates the arthroscopic clock-face orientation into ultrasound scanning windows, providing reproducible steps for each labral quadrant (12 to 12 o'clock) including patient positioning, transducer orientation, and dynamic maneuvers. By leveraging linear transducers with trapezoidal imaging and an optional convex transducer to bypass acoustic shadowing from the acromion and coracoid, all labral segments can be consistently visualized, while dynamic testing reveals subtle clefts, irregular margins, and medial displacement patterns. Clinically, this approach is particularly valuable for patients who cannot undergo MRI or MR arthrography (e.g., due to metallic implants, contrast allergy, claustrophobia or renal dysfunction) and in settings where MR/MRA is unavailable or impractical (sports medicine, urgent care, postoperative follow-up). The pictorial atlas and step-by-step checklists aim to support adoption in routine practice and to facilitate communication with surgeons through shared clock-face terminology. This protocol is not intended to replace MR arthrography for surgical planning; rather, when MRI/MRA cannot be performed or access is limited, it provides actionable, dynamic information that complements clinical decision-making.