The snapping iliopsoas tendon: new mechanisms using dynamic sonography.

Area of Science:

• Musculoskeletal imaging
• Orthopedics
• Biomechanics

Background:

• Snapping hip syndrome, characterized by an audible or palpable snapping sensation during hip movement, can be caused by various anatomical and biomechanical factors.
• The iliopsoas tendon is a common source of internal snapping hip, but the precise mechanisms have not been fully elucidated.

Purpose of the Study:

• To describe novel mechanisms of snapping iliopsoas tendon using dynamic sonography.
• To enhance the understanding of the pathophysiology of internal snapping hip.

Main Methods:

• Retrospective review of dynamic sonography video recordings from 14 patients (18 snapping iliopsoas tendons).
• Patients presented with unilateral or bilateral snapping hips.
• Dynamic imaging was performed with the transducer in a transverse oblique plane, capturing hip movement from flexion-abduction-external rotation to neutral.

Main Results:

• The most common mechanism (14/18 hips) involved the iliopsoas tendon flipping over the iliacus muscle, leading to contact with the pubic bone and an audible snap.
• Less frequent causes included flipping of bifid iliopsoas tendon heads (3/18 hips) and impingement of the iliopsoas tendon over an anterior paralabral cyst (1/18 hips).

Conclusions:

• Dynamic sonography has identified new mechanisms contributing to snapping iliopsoas tendon.
• Sudden flipping of the iliopsoas tendon over the iliacus muscle is the predominant cause of this condition.