- PA view:
- common finding is small frag from ulnar base of proximal phalanx;
- Lateral view:
- may show volar subluxation of proximal phalanx that would indicate
that there is a tear involving the dorsal capsule &
EPB;
- more than 3 mm of subluxation indicates gross instability;
- volar subluxations are common in chronic injuries and are due to
gradual and progressive attenuation of the dorsal capsule;
- Stress Extension View:
- accessory collateral ligament normally tightens in extension, where as proper
ligament loosens;
- joint is initially tested in extension because it minimizes risk of grade 1 or 2
ligament injury being misinterpreted as a grade 3 lesion;
- minimally displaced gamekeeper's fractures should not be stressed tested;
- generally a local anesthetic block is required inorder for patient to cooperate
w/ stress testing;
- generally, proper collateral ligament will tear before accessory ligament, and
therefore, MP joints that are unstable in extension will often be unstable
in flexion (ie there are tears of both ligaments);
- abduction > 35-40 deg is abnormal & indicates complete injury;
- alternatively, a difference in joint stability of more than 15 deg as compared
to the uninjured side, represents instability;
- Stress Flexion Views:
- in flexion, the proper collateral ligament normally tightens;
- joint that opens up < 20-25 deg (compared to opposite thumb) most likely
has incomplete injury;
- alternatively, a difference in joint stability of more than 15 deg as compared
to the uninjured side, represents instability;
---------------------------------------
Gamekeeper's thumb. Evaluation by arthrography and stress roentgenography.
Injuries of the ulnar collateral ligament of the thumb metacarpophalangeal
joint. Biomechanical and prospective clinical studies on the usefulness of
valgus stress testing.
Assessing ulnar instability of the MP joint of the thumb.
AK Palmer, DS Louis.
J Hand Surg. 3-A. 1978. 542-546.
