Multimodality Approach to a Stener Lesion: Radiographic, Ultrasound, Magnetic Resonance Imaging, and Surgical Correlation

Surgical Findings

Given laxity with pain at the UCL on stress testing, MRI and ultrasound findings, and continued pain and instability of the thumb with pinching and grasping during activities of daily living, the patient and orthopedic hand surgeon proceeded with surgical intervention. Preoperative examination under anesthesia confirmed significant laxity on valgus stress without a palpable endpoint (Figures 5A, 5B).

During surgery, retraction of the extensor hood revealed the completely torn and displaced UCL, entrapped dorsally and proximally to the adductor aponeurosis, characteristic of a Stener lesion. After the primary repair of the UCL, the extensor hood was seen partially retracted in a normal location superficial to the normal deep position of the repaired UCL (Figures 6A, 6B).

Discussion

Hyperabduction injuries to the thumb may rupture the UCL of the MCP joint of the thumb or cause a bony avulsion of the base of the proximal phalanx. Injury to the UCL, most often at its distal portion,^4,14,15 may result in a sprain or full-thickness tear of the ligament.

Subsequently, the ligament may remain in situ, or the proximal segment may retract proximal to the adductor aponeurosis with continued abduction of the thumb. On release of the abduction force, the proximal UCL segment is displaced dorsally and proximally by the inferior aspect of the adductor aponeurosis. The UCL becomes entrapped by the adductor aponeurosis and cannot reduce spontaneously.¹⁵ This displacement was initially described by Stener⁶ in 1962 and is referred to as a Stener lesion (Figures 1A-1C).

It is vital for the radiologist to identify a Stener lesion because a nondisplaced tear of the UCL is often treated nonsurgically, but UCL tears displaced more than 3 mm and Stener lesions usually must be operated on to avoid chronic instability, pain, and osteoarthritis.^2-5,8,12-23 Sensitivity and specificity of MRI in evaluating UCL injuries are reported to be almost 100%, with resolution of 1 mm using current surface coils.²³ There are various UCL injury patterns, including partial tears, displaced and nondisplaced complete tears, and even complex injuries, such as an incomplete tear with the torn portion retracted as a Stener lesion.²² MRI is needed to establish the extent of injury, as 90% of complete tears that are displaced at least 3 mm, and all tears with retraction proximal and superficial to the aponeurosis (true Stener lesions), failed immobilization and required surgical treatment.²³Although they vary in the literature, mean sensitivity and specificity of ultrasound in detecting UCL tears in level I studies have been reported as 76% and 81%, respectively.²⁴ When Melville and colleagues²¹ applied their ultrasound criteria—including absence of normal UCL fibers traversing the first MCP joint as well as heterogeneous masslike tissue at least partially proximal to the apex of the metacarpal lateral tubercle—they were able to distinguish displaced full-thickness tears from nondisplaced full-thickness tears with 100% accuracy. Hergan and colleagues²⁵ found that the diagnostic accuracy of MRI was superior to that of ultrasound; while MRI accuracy was perfect, 12% of patients were incorrectly diagnosed with ultrasound, with false-positive or false-negative tendon-edge displacement. In our experience, ultrasound is uniquely useful in its ability to characterize the real-time dynamic interaction of the UCL with the adductor aponeurosis. It has been observed that passive flexion of the first interphalangeal joint moves the adductor aponeurosis in isolation, allowing differentiation from the subjacent UCL.²¹ Had a partial tear been in the differential diagnosis of our patient’s Stener lesion, such a maneuver under ultrasound visualization would have solved the dilemma. In addition, ultrasound allows for comparison with the contralateral ligament at the time of examination should a diagnostic dilemma arise.

As many have reported both bony avulsion of the base of the proximal phalanx and concomitant injury to the UCL, identification of a bony avulsion does not exclude a ligamentous injury and the possibility of a Stener lesion (Figure 7).^16,19

In one study, 14% of patients with injury to the UCL sustained a concomitant bony avulsion of the UCL insertion.²³ However, presence of the avulsion fragment did not alter management, and only those fragments involving more than 20% of the articular surface were considered true fractures and treated as such.

Conclusion

A Stener lesion—retraction of a completely torn UCL becoming entrapped dorsally and proximally to the adductor insertion—can cause pain, instability, and ultimately osteoarthritis if not treated appropriately. The orthopedic surgeon should have a high index of suspicion for a Stener lesion in the appropriate clinical scenario and consider all imaging modalities for diagnosis. Likewise, it is of utmost importance for the radiologist to identify imaging findings of a Stener lesion, as physical examination alone may be limited in its ability to characterize injury severity. Both MRI and ultrasound are useful in evaluating UCL tears, and ultrasound provides the additional benefit of dynamic visualization and comparison with the contralateral side.

Am J Orthop. 2017;46(3):E195-E199. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.