(A) Extensor indices, lumbrical muscle, and flexor digitorum profundus
(B) Flexor digitorum profundus, volar plate, and sagittal bands
(C) Lumbrical muscle, volar plate, and flexor digitorum profundus
(D) Sagittal bands, extensor indices, and lumbrical muscle
(E) Volar plate, sagittal bands, and extensor indices

Pathology of irreducible (complex) dislocations of the index metacarpophalangeal joint. The metacarpal head protrudes volarly between the lumbrical (radially) and the flexor tendons (ulnarly). The proximal phalanx and volar plate displace dorsal to the metacarpal head, and the plate is folded and impinged within the previously congruous articular surfaces. The flexor tendons remaining in the fibrous sheath attached to the volar plate are kept taut by this displacement and thus maintain the tight tendon-lumbrical encirclement around the narrow metacarpal neck. Traction applied to attempt reduction further tightens this entrapment and makes closed reduction impossible.

Reproduced with permission of Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;1:784.

The correct response is Option C.
The lumbrical muscle, volar plate, and flexor digitorum profundus tendons are most likely interfering with reduction of the index finger dislocation. Dorsal dislocations are uncommon injuries that occur as a result of forced hyperextension. The membranous proximal portion of the volar plate ruptures and becomes interposed dorsally between the base of the proximal phalanx and the dorsal metacarpal head. Reduction can be accomplished by flexing the wrist, which loosens the flexor tendons, and then applying pressure, directed distally and volarly, to the base of the proximal phalanx. In patients with complex dislocations, open reduction is required because the volar plate lies in the joint space, blocking a successful closed reduction. With dislocations of the metacarpophalangeal joint, the flexor digitorum profundus tendon lies ulnar to the joint and the lumbrical muscle lies radial to the joint. The sagittal bands and extensor indices are dorsal structures that are not involved.

References
1. Glickel SZ, Barron A, Eaton RG. 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- 808.
2. Kiefhaber TR. Phalangeal dislocations / periarticular trauma. In: Peimer CA, ed. Surgery of the Hand and Upper Extremity. New York, NY: McGraw-Hill, Inc; 1996;1:939-972.

A 17-year-old boy has tenderness over the metacarpal shafts of the ring and small finger four weeks after undergoing closed reduction of a hand injury followed by use of a hand-based splint. On physical examination, there is no rotational deformity of the involved digits. Current radiographs are shown above.

Which of the following is the most appropriate management?

(A) Repeat closed reduction followed by application of a long arm cast
(B) Closed reduction and transcutaneous fixation with Kirschner wires
(C) Closed reduction and external fixation
(D) Open reduction and lag screw fixation
(E) Open reduction and miniplate fixation

The correct response is Option E.

This 17-year-old boy has displaced, angulated transverse fractures of the metacarpal shafts of the ring and small fingers. Closed reduction of the fractures and use of a hand-based splint for four weeks has not resulted in healing. Therefore, operative treatment is the most appropriate next step. This includes exploration to debride any material surrounding the fragments and open reduction of the fractures. In addition, miniplate fixation is indicated for transverse metacarpal fractures.
Repeat closed reduction and application of a long arm cast are unlikely to result in a successful reduction or lead to fracture healing.

Closed reduction and transcutaneous fixation with Kirschner wires may have been considered at the time of injury but are not appropriate four weeks later.

Closed reduction and external fixation are indicated in patients with highly comminuted fractures with or without bone loss or fractures associated with soft-tissue loss.

Lag screw fixation is appropriate for treatment of spiral and oblique metacarpal fractures in which the length of the fracture is at least twice the diameter of the bone. This technique is advantageous because it minimizes periosteal stripping.

References
1. Freeland AE. Hand Fractures: Repair, Reconstruction, and Rehabilitation. New York, NY: Churchill Livingstone, Inc; 2000:14-65.
2. Stern PJ. Fractures of the metacarpals and phalanges. In: Green DP, Hotchkiss RN, Pederson WC, eds. Operative Hand Surgery. 4th ed. New York, NY: Churchill Livingstone, Inc; 1999;1:711-771.

A 35-year-old woman has an open fracture of the index finger metacarpal after sustaining a gunshot wound to the hand. Physical examination shows a 2.5-cm defect of the skin; radiographs show a 2-cm segmental defect of the metacarpal. The patient is to undergo single-stage reconstruction using a distally based posterior interosseous flap with vascularized bone.

Harvest of the flap with a cuff of which of the following muscles will maintain the blood supply to the bone?

(A) Extensor carpi radialis brevis
(B) Extensor carpi ulnaris
(C) Extensor digiti minimi
(D) Extensor pollicis longus
(E) Supinator

The correct response is Option D.

The vascular supply of the ulna can be maintained by harvesting the distally based posterior interosseous flap with a cuff of the extensor pollicis longus muscle. In this patient who has a 2-cm segmental defect of the metacarpal, vascularized bone from the ulna is appropriate for single-stage reconstruction. Other reconstructive options include the radius, scapula, fibula, humerus, and iliac crest. The radial forearm flap may also be harvested as an osteocutaneous flap for reconstruction of the metacarpal.

To determine the cutaneous portion of the posterior interosseous flap, a line is drawn from the lateral epicondyle of the humerus to the ulnar head with the forearm in full pronation. The cutaneous branch of the posterior interosseous nerve, which must be incorporated in the flap, lies 1 cm distal to the midpoint of this line. The posterior interosseous artery lies deep to the deep fascia, and the septum passes between the extensor carpi ulnaris and extensor digiti minimi. After the artery has been identified, the surgeon dissects distally to the supinator, taking care to identify and preserve the posterior interosseous nerve. A 5- to 7-cm segment of bone can be harvested by dissecting through of a portion of the extensor pollicis longus while leaving a cuff of muscle attached to the bone.

Although free iliac crest corticocancellous grafts can be used to reconstruct metacarpal defects, vascularized bone graft is often preferred instead if the defect is large or the soft-tissue envelope has poor quality.

The extensor carpi radialis brevis and supinator muscles do not supply perforators to the ulna.

References
1. Akin S, Ozgenel Y, Ozcan M. Osteocutaneous posterior interosseous flap for reconstruction of the metacarpal bone and soft-tissue defects in the hand. Plast Reconstr Surg. 2002;109:982.
2. Angrigiani C, Grilli D, Dominikow D, et al. Posterior interosseous reverse forearm flap: experience with 80 consecutive cases. Plast Reconstr Surg. 1993;92:285.
3. Yajima H, Tamai S, Yamauchi T, et al. Osteocutaneous radial forearm flap for hand reconstruction. J Hand Surg. 1999;24A:594.