57: Open Reduction of Metacarpophalangeal Joint Dislocation

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Procedure 57 Open Reduction of Metacarpophalangeal Joint Dislocation

Douglas Sammer

Indications

Figures 57-3 and 57-9 provided courtesy of Sandeep J. Sebastin, MD.

image Irreducible (complex) metacarpophalangeal (MCP) dislocation

Examination/Imaging

Clinical Examination

image The MCP joint region will be swollen and tender.

image A neurovascular examination of the finger should be performed to document perfusion and sensory changes.

image Simple subluxation should be distinguished from a complete dislocation.

image In simple subluxation, the proximal phalanx is locked in a hyperextended position (Fig. 57-1).

image In a complete dislocation, the proximal phalanx may be less hyperextended and may even be in a bayoneted position (Fig. 57-2).

image

FIGURE 57-1

image

FIGURE 57-2

Imaging

image Obtain three-view radiographs of the hand and involved digit.

image Assess for associated fractures—a dorsal metacarpal shear fracture is not unusual (Fig. 57-3).

image Note the position of the sesamoids, which indicate the location of the volar plate.

image

FIGURE 57-3

Surgical Anatomy

image The MCP volar plate has a weaker proximal insertion and tends to avulse from the metacarpal, remaining attached to the base of the proximal phalanx.

image In a simple subluxation, the proximal phalanx is hyperextended. In this case, the volar plate remains draped over the articular surface of the metacarpal head and does not lie on the dorsal cortex of the metacarpal head (Fig. 57-4A).

image In a complete or complex dislocation, the proximal phalanx is less hyperextended and may be in a bayonet position. In this case, the volar plate is no longer draped over the metacarpal articular surface but rather lies completely dorsal to the metacarpal head (Fig. 57-4B).

image The dislocation is made complex (irreducible) not only by the volar plate but also by the flexor tendons and lumbrical, which form a noose around the metacarpal neck (Fig. 57-5).

image

FIGURE 57-4

image

FIGURE 57-5

Exposures

image A longitudinal incision is made dorsal to the MCP joint.

image In the thumb, the interval between the extensor pollicis brevis (EPB) and extensor pollicis longus (EPL) is incised.

image In the index and small fingers, the interval between the extensor digitorum communis (EDC) and the more ulnar proprius or minimi tendon is incised.

image In the long and ring fingers, the extensor tendon is split longitudinally in its midline.

image The dorsal capsule is torn, but further capsulotomy and retraction or dorsal capsulectomy may be necessary to visualize the pathology.

image The base of the proximal phalanx with attached volar plate is noted to lie on top of the metacarpal head (Fig. 57-6).

image The flexor tendon can be seen dorsal to the metacarpal head, resulting in a complex (irreducible) dislocation (Fig. 57-7).

image The sesamoids within the volar plate can be seen dorsal to the metacarpal head (see Fig. 57-7).

image

FIGURE 57-6

image

FIGURE 57-7

Pearls

Dorsal and volar exposures have been described and work equally well.

The dorsal exposure is safer because it avoids potential injury to the neurovascular bundles, which do not lie in their normal anatomic position.

Procedure

Step 1

image Closed reduction should be attempted one more time after induction of anesthesia, before opening.

image The wrist is flexed to take tension off the flexor tendons, which may be preventing reduction.

image Pressure is applied to the base of the proximal phalanx, pushing it distally and volarly, sliding it over the metacarpal head (Fig. 57-8).

image If this is unsuccessful, hyperextension may be required before applying pressure to the base of the proximal phalanx.

image If attempt at reduction under anesthesia is not successful, proceed with open reduction.

image

FIGURE 57-8

Step 1 Pitfalls

Traction should be avoided during reduction maneuvers for both simple subluxation and complex dislocation (see Fig. 57-8).

Traction simply tightens the noose in a complex dislocation.

Traction can convert a simple subluxation to a complex dislocation.

Hyperextension should be avoided during reduction maneuvers for simple subluxation because it can convert this to a complex dislocation.

Step 2

image The dislocation is exposed as described previously (see Fig. 57-6).

Step 3

image The wrist is flexed to relax the noose formed by the flexor tendons and lumbrical.

image A Freer elevator is used to push the volar plate distally and volarly, pushing it back into the joint space.

image Simultaneously, the proximal phalanx is gently pushed distally and volarly, sliding it over the metacarpal head.

image If necessary, the flexor tendon is manipulated gently with a pick-up, pushing it back around the lateral aspect of the metacarpal head and into its normal volar position.

Step 4

image Fluoroscopy is used to confirm concentric reduction of the joint.

image The split extensor tendon is repaired with horizontal mattress 4-0 absorbable sutures.

image The skin is closed with simple interrupted sutures.

image A dorsal block splint is applied, placing the MCP joint in 10 degrees of flexion.

Additional Steps

image Occasionally, reduction cannot be achieved by the previous technique.

image In this situation, the volar plate is divided longitudinally in its midline.

image The split volar plate then spreads out of the way of the metacarpal head as the joint is reduced.

image Alternatively, it can be tucked back into the joint, one side at a time, while radially and ulnarly deviating the proximal phalanx.

image If a dorsal metacarpal head shear fracture is present, it can be fixed with a K-wire or a small screw (Fig. 57-9).

image The MCP joint is usually stable after reduction, and K-wire fixation is not routinely necessary.

image

FIGURE 57-9

Postoperative Care and Expected Outcomes

image Within 3 to 5 days, the patient should begin range of motion.

image An Orthoplast dorsal block splint is fabricated to prevent MCP hyperextension, and active flexion and extension within the splint are encouraged.

image The interphalangeal joints can be left free.

image The splint is weaned and light activity allowed at 4 to 6 weeks.

image No sports or heavy use is allowed for 3 months.

image Patients tend to have very good motion and hand function, although mild residual stiffness is not uncommon.

image Posttraumatic arthritis may occur.

Evidence

Afifi AM, Medoro A, Salas C, et al. A cadaver model that investigates irreducible metacarpophalangeal joint dislocation. J Hand Surg [Am]. 2009;34:1506-1511.

The authors developed a cadaveric dorsal MCP dislocation model and then examined the anatomy of irreducible MCP dislocations. The study demonstrates that although there are multiple structures involved in irreducible dislocations, the key structure that inhibits reduction is the volar plate. (Level V evidence)

McLaughlin HL. Complex “locked” dislocation of the metacarpophalangeal joints. J Trauma. 1965;5:683-688.

This classic paper is a retrospective review of 160 MCP dislocations, 22 of which required open reduction. Proper closed reduction technique is emphasized. (Level V evidence)

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