Laboratory Studies
No laboratory tests are necessary for the diagnosis of gamekeeper's (skier's) thumb. In cases where surgical intervention is required, routine preoperative laboratory workup is indicated.
Imaging Studies
Standard radiography
Before any manipulation of the thumb, obtain standard anteroposterior (AP), lateral, and oblique radiographs to exclude metacarpal fractures and gamekeeper's fractures (see the images below).
Nondisplaced avulsion fractures that are associated with rupture of the insertion point of the ulnar collateral ligament (UCL) are not contraindications for manipulation. If these fractures were not displaced at the time of injury and greatest stress, they are stable enough for the manipulation of stress testing.
Gamekeeper's fractures should not be manipulated, especially those that involve more than 30% of the joint surface and those that are malrotated and/or displaced. Such fractures are indications for surgical intervention.
The finding of 3 mm of volar subluxation of the phalanx on the metacarpal is suggestive of complete UCL rupture and instability. Radial deviation of more than 40° in extension and more than 20° in flexion also indicates instability.
Stress radiography
Radiographs obtained with the thumb in the flexed and extended positions and with valgus stress at the MCP joint (see the image below) can help the physician to determine the degree of instability of partial tears of the UCL. [17]
Ultrasonography
Ultrasonography (US) has been found to be effective for evaluating the collateral ligaments of the MCP and IP joints and identifying injuries such as gamekeeper's thumb. [18, 19]
In a French study, Gherissi et al evaluated echography (ultrasonography) to diagnose Stener lesions in 25 gamekeeper's thumbs from March 2005 to March 2007. [2] They found that US is useful in identifying Stener lesion in the emergency department (ED) because it is available, cheap, noninvasive, and dynamic. US was ultrasonographer-dependent and ultrasonogram-dependent. The author's study revealed the advantage of using US with tissue harmonic imaging.
Magnetic resonance imaging
In a 2015 study of 43 UCL injuries, Milner et al described the use of magnetic resonance imaging (MRI) to assess the degree of UCL displacement and thereby help create a four-type classification to facilitate determination of which UCL injuries require surgical treatment. [20] They found that type 1 (partial or minimally displaced) and type 2 (< 3 mm displaced) tears typically healed by immobilization alone, whereas 90% of type 3 (>3 mm displaced) tears failed immobilization and required surgery, as did 100% of type 4 (Stener) tears.
Procedures
The patient often has considerable pain in the thumb, and stressing the MCP joint leads to guarding and misleading findings on examination. The thumb is best examined under local anesthesia, which can be administered in the ED or in the office setting (see the images below). Often, administration of 2-3 mL of 1% lidocaine into the MCP joint of the thumb is sufficient to relieve the pain and relax the patient's guarding.
If more anesthesia is required, perform a metacarpal or digital block. Some authors recommend the use of an ulnar or median nerve block to negate the effects of the intrinsic muscles. If the injection into the joint relieves the pain, no further anesthesia is necessary.
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Anteroposterior radiograph displaying gamekeeper's fracture.
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Lateral radiograph displaying gamekeeper's fracture.
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Radiograph displaying stress test of torn ulnar collateral ligament.
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Stress testing of metacarpophalangeal joint of thumb in flexion.
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Stress testing of metacarpophalangeal joint of thumb in extension.
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Anterior view of hand in thumb spica splint.
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Lateral view of hand in thumb spica splint.
