(A) Protective splinting without reduction
(B) Longitudinal finger traction with a 5-lb weight
(C) Extension of the wrist with traction at the proximal interphalangeal joint
(D) Flexion of the wrist with pressure on the proximal phalanx directed distally and volarly
(E) Open reduction and internal fixation

The correct response is Option D.

This patient has a simple dorsal subluxation or dislocation of the metacarpophalangeal joint of the index finger. The finger can be easily reduced by flexing the patient's wrist while applying pressure at the base of the proximal phalanx directed distally and volary. This relaxes the flexor tendons and allows the proximal phalanx to slide over the metacarpal head and into the properly reduced position.

Protective splinting without reduction will not correct the dislocation.

Longitudinal traction with a 5-lb weight or extension of the wrist with unweighted traction at the proximal interphalangeal joint draws the volar plate dorsally, where it may become folded between the metacarpal head and the base of the proximal phalanx, resulting in an irreducible dislocation. Additionally, because the narrow metacarpal neck is surrounded by taut lumbrical muscle and flexor tendons, further traction will tighten these structures and prevent reduction.

Open reduction is indicated for complete dorsal dislocations. It is typically performed using a volar approach but can be accomplished through a dorsal incision or combined volar and dorsal approach. The surgeon must use caution to protect the radial neurovascular bundle, which lies just beneath the skin and is positioned volar to the protruding metacarpal head.

References
1. Glickel SZ, Barron OA, Eaton RG. Dislocations and ligament injuries in digits. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;1:772-808.
2. Le TB, Hentz VR. Hand and wrist injuries in young athletes. Hand Clin. 2000;16:597-607.

PHOTO

A right-handed, 22-year-old football player sustains the dislocation shown in the radiographs above when he falls on his outstretched right hand. On examination of the hand, the condyles of the proximal phalanx are protruding through the volar flexion crease of the proximal interphalangeal joint. Following regional nerve blockade and irrigation of the joint in the emergency department, closed reduction is unsuccessful.

Which of the following structures is the most likely cause of the unsuccessful closed reduction?

(A) Cleland's ligament
(B) Cruciate pulley
(C) Flexor digital sheath
(D) Flexor digitorum profundus tendon
(E) Lateral band

The correct response is Option D.

The flexor digitorum profundus tendon is the most likely cause of the failed closed reduction. In this patient, the condyle of the proximal phalanx has ruptured through the flexor digital sheath on the ulnar side of the flexor digitorum profundus and superficialis tendons. The flexion power of these tendons foreshortens the digit, causing a sling-like entrapment around the condyles of the proximal phalanx. This constricting structure tightens as the digit is distracted distally and the flexor tendons are blocked by the condyles.

The volar plate also has been shown to prevent closed reduction of dorsal dislocations of the proximal interphalangeal (PIP) joint. However, the positioning of the proximal phalanx with regard to the middle phalanx on anteroposterior radiographs suggests that the entrapment is caused by the flexor tendons and not the volar plate. Appropriate management of this irreducible dorsal dislocation of the PIP joint involves regional blockade with sedation to loosen the tendons, thorough irrigation of the joint, and partial division of the A3 pulley, which will allow the condyles to move from beneath the flexor tendons. It is important to check the stability of the joint in all directions to ensure that the soft tissues and volar plate are not interposed within the joint. Because the joint is often unstable in extension, dorsal extension block splinting is indicated.

Cleland's ligament stabilizes the soft tissues in relation to the bony underlying structures, but does not interfere with closed reduction. Cruciate pulleys and the flexor digital sheath have not been shown to cause irreducible dislocations of the PIP joint. The lateral band typically constricts volar dislocations of the PIP joint, in which the condyles rupture between the central slip and lateral band.

References
1. Glickel SZ, Barron OA. Dislocations and ligament injuries in the digits. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;1:772-782.
2. Wray CR. Fractures and joint injuries of the hand. In: McCarthy JG, ed. Plastic Surgery. Philadelphia, Pa: WB Saunders Co; 1990;7:4617-4627.