Age / Sex : 55 / F

Chief complaint: left 1st MCP area pain after bicycle trauma

What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

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Courtesy: Ja Yeon You, SMG-SNU Boramae medical center

Stener’s lesion

Discussion

Findings:

Plain radiograph:

A small displaced bony fragment with a focal bony defect at the proximal phalangeal base of thumb is noted, which suggests avulsion fracture.

MRI:

 On fat-saturated T2-weighted coronal images, a focal bony defect is shown at the ulnar side of proximal phalangeal base of thumb. The ulnar collateral ligament of the first MCP joint is completely torn at its distal insertion and retracted (yellow arrow). The retracted ligament is flipped superficial to the adductor pollicis aponeurosis (red arrow) consistent with a Stener’s lesion. This appearance is called as a yo-yo on a string sign. A small bony fragment is attached to the swollen avulsed ligament stump on T1-weighted image.

Diagnosis:  Stener’s lesion

Discussion:

•       Gamekeeper’s thumb or skier’ thumb

      - hyperabduction of the thumb

         à injury of the UCL of 1^st MCP joint

         à torn UCL may remain beneath the adductor aponeurosis with a mild retraction

      - missed diagnosis

         à a missing diagnosis may lead to chronic laxity and OA 

•       Stener’s lesion

- retraction and dislocation of the torn end of the ligament dorsally above the adductor aponeurosis

          à indication for surgical repair

•       Radiographic features

- abduction stress view : increase of more than 30° in the 1^st MCP joint, compared with the contralateral thumb à subluxation

•       MRI 

- nondisplaced vs. displaced torn UCL

- stener’ s lesion : “ yo-yo- on a string” pattern with the retracted and balled-up UCL representing the yo-yo and the more distal linear adductor aponeurosis representing the string

References:

1. Clavero et al. MR imaging of ligament and tendon injures of the fingers. RadioGraphics 2002; 22:237–256

2. David W. Stoller. Magnetic resonance imaging in orthopaedics and sports medicine. 3rd Ed. Lippincott Williams & Wilkins, 2007;1850-1851

3. Hinke DH et al. Ulnar collateral ligament of the thumb: MR findings in cadavers, volunteers, and patients with ligamentous injury (gamekeeper's thumb). AJR Am J Roentgenol. 1994;163(6):1431-4.