Gamekeeper Thumb Workup
- Author: Michael A Secko, IV, MD; Chief Editor: Trevor John Mills, MD, MPH more...
No laboratory tests are necessary for making the diagnosis. Routine preoperative laboratory workup may be required for those cases requiring surgical intervention.
Posteroanterior (PA), lateral, and possibly oblique radiographs of the thumb are indicated in patients with a suspected gamekeeper's thumb to identify any avulsion fracture at the base of the proximal phalanx.
Findings on plain films are usually normal in the absence of an avulsion fracture. Degenerative joint changes may be seen years later after the initial insult or with chronic injury.
Displaced avulsion fractures or any fracture involving 25% or more of the MCP joint surface requires surgical treatment and should not be manipulated.
Anteroposterior (AP) view: The presence of an avulsion fracture at the base of the proximal phalanx, or less frequently, at the metacarpal head, is suggestive of ligamentous rupture. The persistence of a radially subluxed MCP joint suggests an interposed rupture of the UCL.
Lateral view (see image below): A volar subluxation of the MCP joint suggests a tear involving the dorsal capsule and the volar plate indicating probable UCL rupture and instability.
Stress radiographs (+/- local anesthesia)
If the diagnosis of gamekeeper thumb is suspected and radiographs show no fracture, comparative radiographs should be obtained in forced valgus. Administration of local anesthesia may be required for proper manipulation. The forced valgus maneuver, which uses a stress test to cause joint tilt, is crucial in making an accurate diagnosis and deciding on the most appropriate therapeutic approach. Researchers report on a method that allows the patient’s thumbs to be compared, under the same force application conditions, on a single radiograph, thereby reducing the patient’s and the examiner’s exposure to x-rays. According to the authors, the technique is well tolerated by the patient and anesthesia for the thumb is usually not necessary.
Radiographs of the MCP join in flexion; extension and lateral stress are useful in grading the severity of MCP joint instability, especially of partial tears of the UCL. As mentioned earlier, greater than 35° of angulation suggests a complete tear.
Other imaging modalities
Arthrography may visualize Stener lesions, but it is an invasive technique, and results are difficult to interpret.
MRI or MR arthrography may be helpful in cases of suspected gamekeeper's thumb by accurately depicting the osseous and soft tissue structures about the MCP joint, including the UCL and surrounding ligaments and tendons. MRI may be impractical and cost prohibitive.
In patients treated surgically, MR imaging resulted in identifying UCL tears with 96% sensitivity and 95% specificity.
Ultrasonography has been shown to be highly accurate in diagnosing Stener lesions. In a study of patients treated surgically, ultrasonography had a sensitivity of 83%, specificity 75%, and a positive predictive value of 94%.
For the emergency physician, carrying out these highly specific tests may not be practical. Standard radiographs and adequate physical examination should be enough to determine those cases that necessitate surgical repair.
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