- 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 metacarpophalangeal joint of the thumb.