This patient presented six months after having a fall onto an outstretched hand. She felt a sharp pain in her left thumb at the time, and reported difficulties with gripping and using it since.
On examination there was some visible enlargement and localised swelling of the ulnar aspect of the metacarpophalangeal joint (MCPJ) of the left thumb. There was also localised tenderness to palpation on the joint line. Joint range was reduced to approximately 1/2 the normal range of flexion and extension,limited by pain. Radial deviation was particularly painful with valgus stress testing (See Figure 1 and 2), but there was no discernible difference between attempting to stress the proper and accessory components to the ligament.
Resisted flexion and extension was preserved. The patient had a hand x-ray , which was reported as normal. As commented by Ebrahim et al (2006) ''Integrity should be theoretically easy to confirm, however pain, swelling and concern about injury can hamper the physical examination''. Access to further dynamic diagnostics can add further information on joint and ligament condition.
Initial thoughts were focussed to the ulnar collateral ligament of the thumb, with a classic mechanism of injury and focussed pain on the ulnar aspect of the MCPJ. As in this case, the mechanism of injury is often one of hyperabduction and degrees of extension. Ulnar collateral ligament injuries are often referred to as Gamekeepers Thumb or Skiers thumb. The UCL plays a key role in the ability to grip items. Its primary function is to resist valgus stress at the MCPJ.
There are often three main types of injury to the UCL:
- Avulsion at the distal insertion, with a small fragment being displaced from the proximal phalanx.
- The UCL may tear in its substance, usually at its distal portion, without osseous injury and the ligament remaining deep to the adductor pollicis muscle.
- The proximal ruptured end can be displaced over the proximal edge of the adductor pollicis aponeurosis. Commonly called a 'Stener lesion'.
On musculoskeletal ultrasound in clinic there was no visible disruption to the extensor or flexor mechanisms. There was visible distension of the capsule and joint effusion on the ulnar aspect of the joint. There also appeared to be significant disruption to the ulnar collateral ligament, with only a few fibres remaining. You can actually see the proximal attachment of the fibres and the characteristic tissue echotexture labelled on Figure 3. There was no clear evidence of avulsion with no visible hyperechoic fragments, in keeping with the x-ray report.
A linear probe was utilised which meant it was more difficult to achieve a clear resolution and alignment. A smaller hockey stick probe would have enabled better images. Stress testing was attempted but difficult to achieve with the size of probe utilised, however a video clip of a positive stress test can be found below by my colleague Dr Peter Resteghini, Consultant Physiotherapist. Only gentle stress should be applied as further displacement can occur.
Musculoskeletal ultrasound facilitated this patients management, by highlighting the disruption to the UCL and facilitating an Orthopaedic referral without the need for further diagnostic referral. Further imaging is required to determine the extent of the injury, and the role of surgical intervention in this case.
The patient subsequently had an MRI within the Orthopaedic team and the results were as follows...
Ebrahimi et al (2006) provide a useful overview in this free text article.