Stener Lesion

View Key Images

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

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

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

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