Age / Sex : 31 / F

Chief complaint :

Left thumb pain after a fall onto her right hand

What is your impression?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Kang Woo Young, Chungbuk national university hospital

Discussion

Answer:  

Stener lesion

Findings:

US scan of the 1^st metacarpophalangeal joint shows a proximally lobulated nodule, which represents the retracted displaced stump of the ulnar collateral ligament. There is loss of the smooth contour of the adductor aponeurosis.  

T2 coronal image at volar aspect of 1^st metacarpophalangeal joint demonstrates a defect at the insertion of the ulnar collateral ligament at the base of the proximal phalanx. The ulnar collateral ligament remains attached at its origin at the metacarpal head, but the stump of the ulnar collateral ligament projects away from the joint at the proximal margin of the adductor aponeurosis on T2 coronal image at dorsal aspect of the joint. The retracted torn end displaces superficial to the adductor aponeurosis on the T2 axial image through the distal metacarpal head. 

Differential Diagnosis:

Discussion:

Gamekeeper’s thumb is an avulsion of the ulnar collateral ligament of the 1^st metacarpophalangeal joint, most frequently at the proximal phalanx during a forced valgus mechanism. Injury at the proximal insertion or a tear in the midsubstance of the ligament are less frequent.

MRI and Ultrasound are userful in evaluating UCL tears and ultrasound offers dynamic evaluation. It is important to distinguish:

. No retraction of the collateral ligament, the torn ends remain underneath the adductor pollicis aponeurosis.

. Retraction of the collateral ligament, the torn end lies superficial to the adductor aponeurosis (“Stener lesion”). The typical MRI appearance has been described as the “yoyo sign”.

Stener’s lesions need to be repaired surgically because of the interposition of the aponeurosis and the risk of chronic instability.

References:

Fischer. MRI-Essentials.Com: An Illustrated Atlas of Orthopedic MRI. 2^nd edition.

Stoller. Magnetic resonance imaging in orthopaedics and sports medicine. 3^rd edition.