Is there a role for an MRI for Gamekeeper’s Thumb Evaluation?

[mtomaino]

An injury to the thumb MP joint Ulnar collateral ligament (UCL), which is most commonly caused after a fall skiing, is typically evaluated by examination and xray, with maybe the addition of stress x-rays. A seasoned hand surgeon can usually determine if the joint is stable or not, and the classic teaching has been that the ligament will heal if the joint is stable, after 6-8 weeks of immobilization. The problem lies at the extreme, with a case of a complete tear, which can then displace so that one end of the torn ligament flips on top of a piece of tissue called the Adductor aponeurosis. This “Stener lesion” will prevent healing—so if a splint or cast is placed with the expectation that healing will occur in a couple of months, it simply won’t happen.
While MRI may be a very expensive assessment tool for a problem that more often than not can be evaluated with simple xray and expert exam---when we are wrong, there may be unnecessary delay in operative treatment. Further, the mere performance of a stress test to assess ligamentous stability may cause an otherwise nondisplaced tear to become displaced.
In this light, Milner et al recently published an interesting article in the January 2015 edition of the Journal of Hand Surgery entitled “Gamekeeper’s Thumb—a Treatment-Oriented Magnetic resonance Imaging Classification”. 43 patients with UCL tenderness and/or instability underwent MRI evaluation with a 1.0 T extremity MRI machine. Imaging results including partial tears and complete tears with varying degrees of displacement were correlated with clinical outcome, with planned surgical intervention restricted to only those with a Stener lesion (type 4 in their classification).
They showed that partial tears (type1) and tears displaced less than 3mm (type2) typically healed by immobilization alone, whereas 90% of tears displaced more than 3 mm (type 3) failed immobilization and required surgery, as did all type 4 (Stener) lesions.
Does this mean that all UCL injuries require MRI assessment? Probably not—and this would be costly. If there is clear evidence of frank instability either because of angulation on xray (see attached) or by instability on gentle stressing, then it can be assumed that either a type 3 or 4 lesion exists, and surgery is probably the best option. And, if there is only mild tenderness, then a trial of splinting is probably warranted, as a type 1 lesion would be expected to feel better after 1 month. But when a tad of instability exists---and if one prefers not to muscle a stress test so as not to induce greater tear displacement, I would likely recommend reassessment after 4 - 6 weeks of immobilization. And, at reassessment, if pain was not much better and if slight laxity still existed, then based on this study, I think an MRI would be valuable.
In the final analysis, many patients with such a thumb ligament injury would probably elect surgery at 4 weeks, with recovery by 3 months, as opposed to failing conservative care at 3 months —only then to have to embark on a 3 month recovery after surgery.