Slipping Rib Syndrome and the Role of Ultrasound

Introduction
Slipping Rib Syndrome (SRS), also known as Cyriax syndrome or rib-tip syndrome, is an underrecognized cause of lower chest and upper abdominal pain. It arises from hypermobility or subluxation of the costal cartilages of the false ribs (typically the eighth to tenth ribs), leading to intermittent impingement of intercostal nerves. Given its often vague presentation and similarity to gastrointestinal or musculoskeletal disorders, SRS may be misdiagnosed, resulting in prolonged patient discomfort.

Epidemiology and Pathophysiology

   Prevalence: Although exact prevalence is unknown, SRS is thought to affect predominantly women and individuals engaged in repetitive trunk movements or athletics.
    Anatomy: The false ribs (8–10) attach to the costal margin via cartilage, forming a flexible, yet potentially unstable, costal arch.
    Mechanism: Trauma, increased ligamentous laxity, or degenerative changes can allow anterior displacement (“slipping”) of rib tips beneath the adjacent cartilage, compressing the intercostal nerve.

Clinical Presentation

Symptoms:
-Sharp, intermittent pain localized to the lower rib cage or upper abdomen
-Pain exacerbated by deep breathing, trunk rotation, or palpation
-Sensations of “popping” or “clicking” at the costal margin

Physical Examination
-Positive “hooking maneuver” (pain reproduced by hooking fingers under costal margin and pulling anteriorly)
-Tenderness along the costal margin without significant inflammation

Diagnostic Challenges: SRS symptoms overlap with gallbladder disease, peptic ulceration, costochondritis, and muscular strain.
Standard radiographs and CT scans often yield normal findings because they capture static anatomy and lack dynamic assessment of costal cartilage movement.

Ultrasound: A Dynamic, First-Line Modality
Ultrasound (US) has emerged as a pivotal tool for diagnosing SRS by enabling real-time visualization of costal cartilage dynamics and nerve impingement.

Advantages of Ultrasound

Dynamic Assessment: Allows operator-directed maneuvers (e.g., Valsalva, rib mobilization) to provoke slipping and visualize subluxation.
High Resolution: Modern high-frequency linear probes (10–15 MHz) can delineate cartilage, rib margins, and adjacent soft tissues.

Noninvasive and Bedside-Ready: No radiation exposure; can be performed in clinic or point-of-care settings.
Guided Interventions: Facilitates precise local anesthetic or corticosteroid injection for both diagnostic confirmation and pain relief.

Ultrasound Technique
        Patient Positioning: Patient seated or supine with slight trunk rotation away from the side of interest to open the costal margin.
        Probe Selection and Orientation: Use a high-frequency linear transducer; orient the probe longitudinally along the anterior costal margin, then rotate transversely for cross-sectional views.
      Dynamic Maneuvers:
              Instruct the patient to inhale deeply or perform mild Valsalva.
              Apply gentle external pressure or mobilize the rib tip to provoke slipping.
              Observe real-time for abrupt change in alignment between cartilage and rib shaft.

Ultrasound Findings in SRS
      -Rib Tip Subluxation: Anterior displacement of the rib cartilage under the adjacent costal cartilage, visible as a sudden shift during dynamic testing.
      -Interchondral Space Widening: Focal separation between cartilage segments, which may close upon relaxation.
      -Nerve Impingement Signs: Localized thickening or hypoechoic change around the intercostal nerve, sometimes with hyperemia on Doppler imaging indicating reactive inflammation.
      -Soft-Tissue Edema: Hypoechoic areas adjacent to the slipping site reflecting minor edema or periarticular fluid.