DISLOCATION OF PROXIMAL INTERPHALANGEAL
JOINT
The proximal interphalangeal joint is basically a hinge joint supported
by the architecture of the bone and by strong collateral ligaments on either
side, which are, in turn, reinforced by a strong volar ligament or plate. The
dorsal capsule of the proximal interphalangeal joint is strengthened by the
central slip of the extensor tendon and by the insertions of the lateral bands
of the extensor tendon hood. Ligament injuries of the proximal interphalangeal
joint, the most common injuries of the hand, include simple sprains of the
collateral ligament or the volar plate (most common), complete dislocations,
and the most severe injuries-fracture-dislocations.
Any injury to the proximal interphalangeal joint can
significantly affect motion and function of the finger and hand as the lesser
fingers typically work in concert together and dysfunction of one finger
hinders the remaining fingers. During the diagnostic evaluation, the examiner
must palpate specific areas for tenderness and assess the stability of the
joint both actively, as the patient flexes the finger, and, passively, as the
examiner moves the finger.
The most common dislocation of the proximal
inter-phalangeal joint, the dorsal dislocation, is often called the
coach’s finger. Frequently occurring in athletic events, the dorsal dislocation
is usually reduced by trainers or coaches shortly after injury. The uncommon volar
dislocation of the proximal interphalangeal joint is a more serious injury
because it disrupts the central slip of the extensor mechanism. Unless properly
treated by splinting with the joint in extension, volar dislocation can result
in a disabling boutonnière deformity. Rotational dislocations are rare.
A unique aspect of this type of dislocation is the appearance of the phalanges on the lateral
radiograph: the proximal phalanx is seen in an oblique plane and the middle
phalanx in a true lateral plane.
Treatment Of Dorsal And Rotational Dislocations
Although closed reduction usually produces a
satisfactory result, open reduction is occasionally required to restore the phalanges to their anatomic positions. If
there is evidence of instability after reduction, simple dorsal and rotational
dislocations of the proximal inter-phalangeal joint can be treated with
splinting for 3 weeks; if the joint is stable, early active motion with buddy
taping is prescribed for 4 to 6 weeks.
Fracture-dislocations are the most severe and
disabling injuries of the proximal interphalangeal joint. In addition to
dislocation, a fracture disrupts the volar surface of the middle phalanx,
resulting in both dorsal and volar instability. These injuries are often missed
because the dislocation reduces spontaneously and patients do not come to
medical attention and/or the fracture of the volar lip of the middle phalanx
appears quite insignificant on the radiograph to a non-hand specialist and
restricted motion is not instituted, with subsequent resultant subluxation and
joint degeneration.
Some fracture-dislocations can be treated with closed
reduction of the dislocation and use of an extension block splint. The splint
allows full flexion of the finger and a range of extension that maintains the
reduction and stability of the proximal interphalangeal joint. This method of
treatment requires close radiographic follow-up. As healing increases the
stability on the volar side, the amount of extension can be gradually increased
until the joint remains stable in full extension.
Fracture-dislocation with a large fragment from the
volar lip requires open reduction with Kirschner wire or screw fixation. Late
reconstruction of this injury involves either arthrodesis, volar plate
interposition arthroplasty, or prosthetic arthroplasty.
In all injuries of the proximal interphalangeal joint,
the patient should be informed that the joint will remain enlarged for a long
time, possibly many years, and that some loss of motion is quite common.
Treatment Of Volar Dislocations
In the more severe volar dislocation, the proximal
inter-phalangeal joint must be splinted in extension for 4 to 6 weeks to avoid creating a boutonnière deformity. A
rare injury of the proximal interphalangeal joint, fracture of the dorsal lip
of the middle phalanx results in an avulsion of the central slip of the
extensor mechanism. This injury must be treated with open reduction and, if
necessary, pin or screw fixation of the fracture fragment. Failure to recognize this injury and restore the attachment of
the central slip to the middle phalanx leads to a boutonnière deformity, with
chronic pain and instability. If boutonnière deformity develops, arthrodesis of
the proximal inter-phalangeal joint is often the only salvage procedure possible.
