Stener Lesion

Diagnosis Definition

• The ulnar collateral ligament (UCL) of the thumb arises from the dorsal MC head and inserts at the base of the proximal phalanx
• Most UCL injuries occur from a fall on an abducted, outstretched thumb, producing a valgus force on the MCP joint
• Stener lesions occur in 64-88% of complete UCL tears; the distal portion of the UCL avulses from its attachment on the proximal phalanx and herniates through the adductor aponeurosis
• Because the torn end of the UCL cannot approximate the proximal phalangeal insertion, normal healing and stability cannot be achieved and surgery is required to repair the UCL

Imaging Findings

• Key MRI sequence is coronal oblique with T2 FSE
• On fluid-sensitive sequences, partial tears of the UCL demonstrate focal attenuation of the ligament with hyperintense signal partially traversing the ligament
• Complete tears are identified by hyperintense signal fully traversing the ligament or at the site of bony attachment on fluid-sensitive sequences
• MRI of a Stener lesion shows a “yo-yo on a string” appearance with the string representing the adductor aponeurosis and the yo-yo representing the balled-up and proximally retracted UCL

KEY IMAGES

Pearls

• Simply following the adductor aponeurosis proximally on the axial images provides a useful landmark for identifying displaced ligamentous tissue, which is readily seen protruding beyond the plane of the aponeurosis
• Gamekeeper’s thumb (chronic injury) and skier’s thumb (acute injury) are two similar conditions involving the UCL

References

1. Hergan K, Mittler C, Oser W. Ulnar collateral ligament: differentiation of displaced and nondisplaced tears with US and MR imaging. Radiology 1995; 194(1):65-71