CARPOMETACARPAL AND METACARPOPHALANGEAL INJURIES
OTHER THAN FRACTURE
The thumb acts
as a very mobile post that opposes the actions of the index, middle, ring, and
small fingers. The stability of the thumb is therefore very important in hand
function.
Injury To Ulnar Collateral Ligament Of The Thumb
In the metacarpophalangeal joint of the thumb, injury
to the ulnar collateral ligament destroys joint stability and impairs the
ability to pinch. Known as the game-keeper thumb, this injury is a common
consequence of skiing, motor vehicle, and occupational accidents.
Any injury to the ulnar side of the
metacarpophalangeal joint of the thumb must be evaluated with a stress test to
determine the integrity of the ulnar collateral ligament. The stress test
should be performed using digital block anesthesia. If the test shows joint
instability, the ulnar collateral ligament should be repaired surgically.
Surgical examination often reveals the adductor tendon
aponeurosis interposed between the torn ends of the ulnar collateral ligament;
this condition, called the Stener lesion, prevents healing. A tear in the
substance of the ligament itself is repaired with interrupted sutures. If the
ligament is avulsed from the bone, repair with a pull-out wire or bone suture
anchor is needed. Avulsion of a bone fragment together with the ligament
requires reduction of the fragment and fixation with a small screw, a pull-out
wire, or Kirschner wires.
To ensure stability, a Kirschner wire is sometimes
placed across the joint to relieve the tension on the repaired ligament. After
ligament repair, the thumb is immobilized in a cast for at least 4 weeks. The
patient can begin guarded activity at 4 weeks, after the cast and pin are removed. Early anatomic repair of gamekeeper
thumb produces quite satisfactory results.
Dislocation Of Carpometacarpal Joint
This thumb injury can also be quite disabling. Because
of the configuration of the carpometacarpal joint, dislocations are inherently unstable. Although reduction of the
carpometacarpal dislocation is easy, maintaining the reduction in a plaster
cast is very difficult. Therefore, in most carpometacarpal dislocations, the
reduction must be pinned to ensure stability. The pin is placed across the
joint and maintained for 4 to 6 weeks to allow the joint capsule to heal. Chronic, undiagnosed,
or recurrent dislocations of the carpometacarpal joint of the thumb can be treated either with ligament
reconstruction, using the flexor carpi radialis tendon, or with arthrodesis of
the carpo- metacarpal joint.
Dislocation of the carpometacarpal joint is also
common in the small finger and lesser in the ring finger and is usually due to
a punch against a wall in a fit of anger. Because there is significant mobility
in the ring and small finger carpometacarpal joint, it remains unstable unless
reduced and it often requires temporary pinning. There is also a high incidence
of fracture of either the base of the metacarpal or the dorsal articular
surface of the hamate that requires open reduction and internal fixation to
restore the articular surface.
Dislocation Of Metacarpophalangeal Joint
Dorsal dislocation of the metacarpal phalangeal joint
occurs more commonly in the thumb than the lesser fingers, and the direction of
dislocation is defined by the direction of the distal bone. These can be
difficult to reduce owing to the interposition of the volar plate, which makes
closed reduction difficult at times. Open reduction in the thumb is often
easily achieved from a dorsal incision, and then the volar plate that is
reduced to the palmar position scars back down in place after immobilization of
the joint in 30 degrees of flexion. If unstable, this joint can be held with a
pin across the metacarpophalangeal joint for 4 weeks. A palmar approach to the metacarpophalangeal joint allows for
direct repair of the volar plate to the volar neck of the metacarpal with a
bone anchor.
In the lesser fingers, closed reduction becomes a
challenge not only because the volar plate is trapped but also because the
flexor tendons wrap around one side of the metacarpal neck and the lumbrical
muscle around the opposite
side and any kind of traction tightens this “noose,” preventing reduction of
the palmarly displaced metacarpal head. Both dorsal and volar approaches have
been described to open reduce this dislocation. More uncommonly, palmar
dislocations of the thumb and lesser fingers do occur and operative reduction
is usually required.
