Metacarpal Fractures and Dislocations 

Updated: Jun 13, 2018
Author: James Neal Long, MD, FACS; Chief Editor: Joseph A Molnar, MD, PhD, FACS 

Overview

Background

This article covers fractures and dislocations of the metacarpals of the hand. Injury to the phalanges and the thumb metacarpal are discussed in separate articles in this journal. For excellent patient education resources, see eMedicineHealth's patient education article Broken Hand.

History of the Procedure

Trauma to the hand is common, with resultant fractures of the metacarpals and phalanges accounting for approximately 10% of all fractures. Most of these injuries are treated with splinting followed by early motion. For information on splinting hand injuries, see Medscape Reference articles Volar Splinting, Radial Gutter Splinting, Ulnar Gutter Splinting, and Sugar-Tong Forearm Splinting.

Although most metacarpal fractures can be successfully treated with closed management, certain fractures and dislocations require intervention to ensure optimal restoration of function.

Problem

The vast majority of metacarpal fractures occur in persons aged 10-40 years, with a predilection for males. These fractures typically result from trauma sustained in sports, motor vehicle accidents, or work related injuries. In the United States in 1980, 16 million upper extremity injuries resulted in 16 million days off work and an additional 90 million days of restricted activity. The comprehensive associated economic burden is estimated at 10 billion dollars in cost and lost revenue.[1]

Epidemiology

Frequency

Fracture of the metacarpals and phalanges comprises approximately 10% of all fractures. Metacarpal fractures account for 30-40% of all hand fractures; fractures of the first and fifth metacarpals are the most frequent. Fractures of the fifth metacarpal neck (boxer fractures) alone account for 10% of all fractures of the hand. Lifetime incidence of metacarpal fractures is approximately 2.5%.[2]

Etiology

Injury to the metacarpals is the result of either direct or indirect trauma. The nature and direction of the applied force determines the resultant fracture or dislocation. Specific injury patterns that occur from commonly seen trauma are as follows:

Carpometacarpal injuries

Metacarpal base fractures and dislocations of the carpometacarpal (CMC) joint commonly result from a fall or other stress on the hand with the wrist flexed.

Metacarpal shaft and neck injuries

Metacarpal shaft fractures typically are produced either by axial or rotational loading or direct trauma. Metacarpal neck fractures, the most common metacarpal fractures, usually result from striking a solid object with a clenched fist.

Metacarpal head injuries

Metacarpal head fractures are intra-articular injuries and result from axial loads or direct trauma.

Metacarpophalangeal (MCP) dislocations

MCP dislocations usually are the result of forced hyperextension of the proximal phalanx on the MCP.[3]

Pathophysiology

Metacarpal base injuries

Injuries to the metacarpal base include fractures, dislocations, or a combination of these (fracture-dislocations). The CMC joints, with the exception of the thumb, are generally stable joints, with the metacarpal bases held in position by dorsal and volar CMC ligaments. The individual metacarpal bases are also strongly bound together by interosseous ligaments. The most common injuries seen in this region of the metacarpal are impaction fractures caused by excessive axial loading, avulsion fractures from tendinous loading, and combinations of abnormal axial and tendinous loading.

Carpometacarpal dislocations and fractures

Carpometacarpal dislocations may occur with or without fracture. Commonly, either avulsion (chip) fractures of the metacarpal base, or fracture of the dorsal hamate accompanies CMC dislocations. A dislocation and fracture at the base of a single metacarpal should signal the examiner to look for fractures or dislocations of the adjacent metacarpals, as the strong interosseous ligaments at the base of the metacarpals very typically associate adjacent injury.

Fracture-dislocation of the base of the fifth metacarpal is a common intra-articular injury; dorsal and proximal fragment displacement is due to extrinsic extensor carpi ulnaris (ECU) and flexor carpi ulnaris (FCU) tone and is the corollary to the Bennett fracture of the thumb.[4] Thus, this injury has been termed the reverse Bennett fracture. The fourth and fifth metacarpals are the most mobile about the CMC interface, their bases articulating with two distinct, ridge-separated, concave facets on the hamate. While direct blows to the ulnar border of the hand tend to create extra-articular fractures of the metacarpal base, intra-articular fractures are usually the result of an axial load. The intra-articular fracture pattern usually leaves one third to one fourth of the radial articular base seated on the hamate with the remaining ulnar fragment displaced dorsally and proximally.

Other commonly seen base fractures include the Bennett and Rolando patterns; each of these is classically described for the first metacarpal.[4, 5] Both may develop as fracture dislocations of the first metacarpal because of extrinsic and intrinsic muscular forces acting on the fragments. While the Rolando fracture, a tripartite intra-articular T or Y pattern, was described for the first metacarpal, it has, by convention, become commonly used for this pattern seen involving other metacarpal bases. The Roberts radiographic view is especially helpful in fully assessing the first metacarpal base.

Metacarpal shaft/neck fractures

Axial loading, direct blow, or torsional loading can cause metacarpal shaft fractures. These fractures are appropriately described by location, fracture pattern, and displacement. Transverse, oblique, and spiral are the accepted terms used to describe the patterns most commonly seen. Importantly, fracture pattern can often ascribe a mechanism of injury. Direct blows often result in a transverse pattern, while axial and torsional loads typically form oblique and spiral fractures, respectively.[6]

Fractures of the metacarpal neck are among the most frequent fractures of the hand; in these fractures, the fifth metacarpal is most likely to be fractured. Such fractures are usually caused by striking a solid object with a closed fist and have been commonly named boxer fractures.

Metacarpal head injuries

Fractures of the metacarpal head are rare injuries. These fractures are intra-articular and, if displaced, usually require open reduction and internal fixation (ORIF). The etiology is usually direct trauma to the joint or an avulsion injury of the collateral ligaments. Injuries caused by direct trauma are often comminuted. Penetration into the metacarpophalangeal joint by teeth or other objects is a common cause of injury to the articular surface of the metacarpal head. These contaminated penetrating injuries carry a special risk of destructive joint sepsis if not recognized. The Brewerton view radiograph can help in revealing occult fractures and joint surface injuries.

MCP dislocations

Almost all MCP dislocations occur with the proximal phalanx displaced dorsally on the metacarpal head. No specific dorsal restraint spans the joint other than the relatively diaphanous dorsal joint capsule and extensor mechanism. The collateral ligaments usually remain intact, and the weaker proximal insertion of the volar plate avulses from the metacarpal chin. Simple dislocations can be reduced without operative intervention under local anesthesia or a combination of local anesthesia and sedation by wrist flexion and application of dorsal pressure at the base of the proximal phalanx; however, some special exceptions are worthy to note.

Volar plate or, in the case of the thumb, sesamoid, interposition into the MCP may prevent reduction. Index and small finger MCP dislocation reductions, in particular, may be inhibited by MCP entrapment of lumbrical and flexor tendons. Dislocations that cannot be easily reduced by closed means are termed "complex" and warrant open reduction. Moreover, inappropriate MCP hyperextension attempts at closed reduction may lead to sesamoid or soft tissue interposition into the MCP joint, thereby converting simple dislocations to complex.

Presentation

Injuries to the metacarpal base

Most fractures of the metacarpal base are impaction fractures, often associated with other injuries. These fractures are rare and often go undiagnosed. Diagnosis, while directed by clinical examination, is usually confirmed with radiography. Point tenderness or visible deformity may provide the earliest clinical indicator of injury. Later signs include edema and ecchymoses.

Beyond obtaining a good history of events from the patient, the most useful clinical examination in the context of metacarpal base fractures is inspection. Taking particular note of mechanism, along with position of external lacerations, abrasions, and contusions, can help guide the examination. Specific areas of injury can be difficult to isolate by more directed means because of patient pain and swelling. The author has found it extremely helpful, in cogent patients who may have closed fractures, to ask them to point, with one finger only, to the area of maximal tenderness. Radiographs are required in suspected injury. The author prefers hand position and alignment (P/A), lateral, oblique, clenched fist (augmenting any base fragment lucency and highlighting intermetacarpal base ligamentous instability) and Roberts (first metacarpal base) views.

Fractures of the metacarpal shaft and neck

Problems associated with metacarpal fractures of the shaft and neck relate primarily to foreshortening, rotation, and angulation. Of these, malrotation is the most functionally important, as a minor rotational deformity can cause the fingers to overlap or "scissor" when the hand is closed. This malrotation can result in a weakened grip and a constant annoyance for the patient. Inspection for loss of knuckle prominence and the presence of scissoring often lead to an accurate focus prior to radiographic review. High energy and penetrating trauma may result in comminution, bone loss, or both; specialized surgical considerations include a possible need for bone grafting or specialized means of fixation. The fourth and fifth metacarpals are the most commonly fractured. Radiography of suspected injury is required. The author prefers hand P/A, lateral, and oblique views to fully assess these injuries.

Injuries to the metacarpal head

Pain, swelling, and loss of motion, often accompanied by soft tissue trauma, are the key clinical indicators of injury to the MCP joint. Crepitus or joint locking may be present on attempted ranging with intra-articular injuries. The Brewerton view radiograph can be quite helpful in assessing these injuries without the delays typically associated with obtaining tomograms.

MCP dislocations

MCP dislocations are identified by local pain and positional deformity and can be confirmed by plain lateral radiographs.

Indications

Most injuries to the metacarpal are managed with closed reduction and external splint immobilization. Indications for operative treatment include failure to achieve or maintain acceptable reduction, open fractures, multiple fractures in the hand, complex injuries, displaced intra-articular injuries, and fractures with serious soft tissue injury requiring a stable skeletal support. Specific indications are described below.

Fractures and dislocations of the metacarpal base

Impaction fractures of the metacarpal bases that are not significantly displaced can be treated with splinting, followed by early mobilization.

CMC fracture-dislocations usually are unstable. Although historically these fractures were treated with closed reduction and immobilization, frequently with good results, current literature supports closed reduction and pin fixation as closed management leads to residual pain and weakness of grip.

Fracture-dislocations of the metacarpal in which the dorsal portion of the hamate is fractured and displaced should be treated with ORIF.

Open reduction with pin fixation is often required with multiple CMC joint injuries, especially when there is a large hamate fracture or the dislocation is irreducible.

Fractures of the metacarpal shaft

Metacarpal shaft fractures tend to angulate apex dorsally, with the head displaced volarly. This is due to the tendency of axial forces to focus energy on the concave volar cortex of the metacarpal shaft, coupled with the volar dominant tone of the intrinsic musculature as a deforming force during and after impact. Foreshortening is also a product of intrinsic muscular force and is illustratively seen when oblique fractures slide at the fracture line. Only a small amount of angulation (< 10°) is acceptable in the second and third metacarpals because of their limited CMC motion. The fourth and fifth finger metacarpals are much more mobile, and volar angulations of 30° and 40° can be accepted, respectively. The more proximal the fracture, the more amplified the effect of angulation; thus, the more proximal the fracture, the less angulation should be tolerated by the treating physician.

Indications for surgery include open fractures, unstable fractures, nonreducible fractures, multiple fractures (inherently unstable patterns), or fractures that represent early malunion from poor anatomic alignment.

Fractures of the metacarpal neck

Metacarpal neck fractures usually can be managed closed without operative intervention. Although the degree of angulation acceptable is controversial, higher degrees of angulation can be accepted with little or no functional deficits in fractures of the neck, especially in the fourth and fifth digits.

Patients should be informed of the cosmetic change to the appearance of the hand, but overall good function is the rule rather than an exception with closed treatment.

Fractures and dislocations of the metacarpal head

Metacarpal head fractures are intra-articular. Displacement of a metacarpal head fracture should be treated with ORIF to ensure a stable, anatomic reduction and allow for early motion. Simple dislocations are best treated by wrist flexion and dorsal application of pressure to the P1 base. Inappropriate MCP hyperextension to recreate the position of injury should be avoided in order to prevent the creation of complex from simple dislocations. Complex nonreducible dislocations require operative reduction.

Relevant Anatomy

Common patterns of injury to the hand result both from recurring etiologic patterns and the unique anatomy of the hand. See the images below.

Metacarpophalangeal ligaments. Metacarpophalangeal ligaments.
Metacarpophalangeal musculoskeletal structure. Metacarpophalangeal musculoskeletal structure.

The metacarpals are long, tubular bones with an intrinsic axial and a collective transverse arch. The bones have a volar arc when viewed from their lateral aspect and have a oblong, closed "V" shape viewed cross-sectionally with relatively thicker volar cortices. They are joined proximally and distally by ligamentous attachments. The second and third metacarpals are fixed rigidly in their CMC seats, while the fourth and fifth metacarpals are capable of 15° and 25° of motion at their respective CMC rests. The thumb is highly mobile, and its unique motion and injury patterns are addressed in a separate chapter. The arc of motion at the MCP joints ranges from 85-105°.

The cam-shape of the metacarpal heads leads to relaxation of the collateral ligaments in extension, permitting adduction and abduction of the fingers. With flexion of the MCP joints, the collateral ligament becomes taut and acts to stabilize the fingers for power pinch and grip. Increased tension in the collateral ligaments with MCP flexion can be used by the clinician to stabilize the metacarpal head while reducing a metacarpal neck fracture and then to maintain stability through immobilization.

The volar aspects of the cross-sectional metacarpal closed V shape noted earlier are the site of origin for both dorsal and volar interossei muscles. These muscles are important deforming forces in metacarpal shaft fractures and, because of their volar positioning, contribute to angulation as well as foreshortening.

Joint congruency, collateral ligaments, and volar plate each act to provide stability to the MCP. The volar plate is a cartilaginous ligament on the volar aspect of each MCP joint. Volar plates are interconnected via the deep transverse intermetacarpal ligaments, which provide additional stability. The plates are thicker at their insertions on the proximal phalanges and weaker at their metacarpal origins.

Contraindications

The treatment of metacarpal fractures has few absolute contraindications. Most are amenable to either closed versus open reduction with internal versus external fixation or cast immobilization. However, placing internal fixation, such as miniplates or screws, in either infected or clean wounds that cannot be closed primarily is inadvisable. If internal fixation in this setting is planned, any soft tissue defects should be immediately reconstituted by means of soft tissue mobilization or transposition at the time of fixation.

 

Workup

Laboratory Studies

See the list below:

  • Choose appropriate studies base on patient comorbidities as determined by the history and physical examination.

Imaging Studies

See the list below:

  • Radiographs

    • The primary means of evaluating hand injuries beyond the history and physical examination is through plain radiographs.

    • Significant injury to the hand should be assessed first with posteroanterior (PA), lateral, and oblique views.

    • The Roberts view is helpful in more fully assessing the first metacarpal base. See the image below.

      Roberts view. Roberts view.
    • The Brewerton view is helpful in detailing the anatomy of fractures and chips of the metacarpal heads. See the image below.

      Brewerton view. Brewerton view.
    • The clenched fist view can reveal ligamentous injuries at the metacarpal bases and intercarpally.

    • CMC injury

      • Fractures in this area of the hand are hard to diagnose as the radiographic evidence is often subtle, and additional rotated views may be necessary. The key to radiographic diagnosis lies in the subtle loss of joint space seen on AP projections. This is often seen as a "broken saw tooth" sign at the CMC joint. This sign may be accompanied by displacement noted on the lateral or oblique views. Tomograms may be necessary to accurately diagnose these injuries.

      • It is important to look closely for multiple injuries; the interosseous ligaments are strong, and a fracture-dislocation of one metacarpal is often accompanied by that of one or more of its neighbors. Displacement in dislocation is usually dorsal, as the dorsal ligaments are weaker.

    • Metacarpal shaft and neck injury: Usually, a diagnosis can be made by observing edema, ecchymoses, pain, and deformity at the fracture site, although swelling can mask the deformity. AP, lateral, and oblique radiographs typically will demonstrate the fracture and displacement.

    • Metacarpal head fractures: Evaluation of these injuries may require additional imaging studies, such as Brewerton view radiography, tomography, or CT scan, to evaluate for fracture and displacement.

    • MCP dislocation: MCP dislocations are readily apparent on physical examination. AP radiographs show overlap of the metacarpal head and base of the proximal phalanx. The lateral radiograph is diagnostic with the presence of dorsal displacement of the proximal phalanx.

  • CT

    • Plain tomography or CT scans can be helpful in diagnosing intra-articular injuries to determine fracture alignment and displacement.

    • These studies may be indicated to evaluate carpometacarpal fracture-dislocations or metacarpal head injuries.

Diagnostic Procedures

See the list below:

  • Traction radiographs

    • Radiographs taken in the PA and lateral dimensions while applying traction to the injured digit(s) can be helpful in evaluating injuries when there is significant comminution of the fracture. This is especially true with intra-articular injuries.

 

Treatment

Medical Therapy

Most injuries to the metacarpals can be managed nonoperatively. Management usually begins by administering sedation, local anesthesia, or both, followed by closed reduction of the fracture or dislocation. Note that, while the use of dilute epinephrine containing local anesthetics in the digits and hand has been traditionally, by rote, not recommended, a recent challenge to this maxim has shown this anesthetic combination to be safe in this body region, with the attendant benefits of prolonged anesthesia and reduced bleeding within the surgical field.[7, 6]

After satisfactory reduction, a forearm-based splint is applied and held in place by a lightly-applied compressive wrap. The goal of nonoperative management is to obtain reasonable alignment with stability, which will permit early range of motion of the fingers and wrist.

Specifics on acceptable reduction and indications for surgical management are discussed in the following section.

While most fractures and dislocations can be treated nonoperatively, closed reduction is conveniently performed in a setting where percutaneous pinning may be used, since acceptable reductions may be unstable without such fixation.

Most MCP dislocations are easily reducible but may require open reduction if they are complex or are associated with unstable fractures.

Most MCP joint injuries should be partially immobilized with a dorsal blocking splint, which prevents movement that might permit recurrence. The splint should be devised so that a patient has unrestricted flexion in the dorsal block (which is set between 15° degrees to neutral), provided that reduction is stable within the range established. Dislocations which are unstable after dorsal blocking should be treated by fixation. Pinning unstable dislocations in reduction for no more than 3 weeks followed by active range of motion is the author's preferred method. Early mobilization is critical in preventing stiffness, and hand therapy should be instituted if range of motion does not return promptly.

Surgical Therapy

Most of these injuries are treated with external immobilization followed by early motion. Although closed management is generally acceptable, certain fractures and dislocations require operative intervention to ensure satisfactory restoration of function.[8]

CMC injuries

Usually these fractures are easy to reduce but difficult to maintain due to deforming forces. Recommended treatment is closed reduction and pin fixation to stabilize the CMC joint.

Pin placement can either transit the CMC joint or secure the reduced metacarpal to the adjacent metacarpal shaft. Patients are splinted postoperatively for 3 weeks, after which they are encouraged to begin movement. The pins should be removed at 6 weeks.[9]

Fracture-dislocations of the metacarpal in which the dorsal portion of the hamate is fractured should be treated with ORIF. Care should be taken to ensure anatomic reduction of the hamate to preserve the CMC articular rests of the mobile fourth and fifth metacarpals.

CMC dislocations are reduced by applying longitudinal traction and direct pressure over the displaced metacarpal base. These injuries are often stable after reduction and can be treated by splint immobilization alone. Unstable injuries should be stabilized by percutaneous pinning.

In cases where closed reduction cannot be achieved, open reduction followed by percutaneous pinning is recommended. Care should be taken in the surgical approach to avoid neurovascular structures. The dorsal branch of the ulnar nerve lies subcutaneously beneath the dorsal and lateral approaches to the fifth metatarsal base.

Metacarpal base fractures

Fractures of the fifth metacarpal base frequently require internal stabilization. When this pattern is nondisplaced or minimally displaced (< 1-2 mm), it can be managed nonoperatively by splinting for 4 weeks. More often, the fracture displaces because of the deforming forces of the extensor carpi ulnaris (ECU) and the flexor carpi ulnaris (FCU) via its linkage to the pisometacarpal ligament. These forces tend to displace the fragment dorsally and proximally. Although such a fracture may be easily reduced, it is usually unstable because of these forces. The author prefers closed reduction with percutaneous pin fixation.

Metacarpal shaft injuries (overview)

Most cases of closed metacarpal shaft fractures are managed nonoperatively.

Reduction of metacarpal shaft or neck fractures can be accomplished with local hematoma or wrist block anesthesia in the emergency department using 1% lidocaine with epinephrine. The fracture is then reduced using a maneuver described by Jahss in 1938.[10] To employ the Jahss maneuver, the MCP and proximal interphalangeal (PIP) joints of the affected metacarpal are flexed to 90°. The fracture is reduced by upward pressure on the head of the proximal phalanx with dorsal resistance applied to the metacarpal shaft at a point proximal to the fracture line. Flexing of the MCP joint tightens the collateral ligaments and provides a rigid lever for reduction. The proximal phalanx can then be used to control or correct malrotation. The reduction is stabilized by splinting or pinning.

Noninvasive immobilization is properly done by placement of an ulnar gutter or clamshell splint. When used, the volar portion of the splint should not extend beyond the volar MCP crease, providing metacarpal head support while allowing PIP and DIP joint motion, which can prevent stiffness. The Jahss splinting technique, whereby the finger is kept in flexion with upward force applied across the PIP joint, should not be used because the risks of skin necrosis, joint stiffness, and flexion contracture are contraindicative.[10]

Immobilization should be continued for 4-6 weeks. Immobilization should not continue longer than 6 weeks, as stiffness and tendon adhesions can limit range of motion and lead to poorer results.

Many fractures reduced and splinted have recurrent angulation due to the force of the intrinsic muscles on the fracture. For this reason, it is sound to consider undertaking such reductions in a setting where percutaneous pinning may be performed to provide more rigid stabilization.

Metacarpal fracture operative intervention

Open fractures require operative debridement and irrigation. Cleansing is typically followed by stabilization, using either internal or external fixation. Metacarpal neck fractures with small lacerations over the MCP joint should be assumed to be the result of a human bite (fight-bite) and should be treated by joint lavage and appropriate antibiotics. The author recommends ampicillin/sulbactam (Unasyn), followed by its oral equivalent, amoxicillin/clavulanate potassium (Augmentin), each of which has a good broad spectrum but also specifically covers Eikenella corrodens, a common and destructive oral contaminant.

Operative stabilization of fractures can be accomplished by several methods. Most fractures can be stabilized with simple Kirschner wire (K-wire) fixation. The K-wire can be placed longitudinally or transversely into the adjacent metacarpal. Longitudinal pin fixation is usually stable but requires that the pin pass through the extensor sheath and can lead to stiffness if the pins are not removed in 3-4 weeks. Transverse pin placement can provide stability without splinting and allow for earlier motion.[11]

To achieve transverse fixation, K-wires are passed transversely at 2 distinct sites, one proximal to and one distal to the fracture line. Wires are passed into the adjacent metacarpal to achieve stabilization. Using 2 wires distally prevents distal segment rotation and reangulation. Pins can be left percutaneous or cut to lie just beneath the skin. An external fixator can be used to maintain length for segmental bone losses or severe comminution or for fractures involving more than one metacarpal.[9, 12, 13]

A study by Rocchi et al indicated that antegrade percutaneous intramedullary K-wire fixation is an effective treatment for unstable, displaced metacarpal fractures. Patients in the study underwent the fixation procedure along with closed reduction. At an average 10-weeks’ follow-up, the investigators noted no statistically significant difference in average total active motion between the injured and contralateral digits. Fractures in the study steadily achieved union, and postoperative reduction loss was not significant.[14]

Metacarpal internal fixation

Internal fixation can be accomplished by several methods. Intramedullary pre-bent pins inserted into the MC head via a corticotomy in the metacarpal base have provided good results (see images below), as have percutaneously placed pins.[15] Tension band wire fixation placed on the dorsal shaft is an excellent low-profile method of fixation if no significant comminution is present. In long oblique fractures in which the fracture length is greater than 2 cortical diameters, interfragmentary lag screw fixation can be used to establish an anatomic reduction while producing compression at the fracture line and providing superior stability.

Displaced fourth and fifth metacarpal fractures, a Displaced fourth and fifth metacarpal fractures, anteroposterior view.
Fourth and fifth metacarpal fractures, oblique vie Fourth and fifth metacarpal fractures, oblique view.
Fourth and fifth metacarpal fractures after intram Fourth and fifth metacarpal fractures after intramedullary pinning, anteroposterior view.
Displaced fourth and fifth metacarpal fractures, l Displaced fourth and fifth metacarpal fractures, lateral view.
Fourth and fifth metacarpals after intramedullary Fourth and fifth metacarpals after intramedullary pinning, lateral view.

Xiong et al described the successful use of flexible, absorbable intramedullary rods for the repair of shaft fractures of the fourth and fifth metacarpals. At follow-up, an average of 4.2 months postoperatively, the investigators found that neither shortening nor angulatory or rotatory deformity had occurred in the study’s five patients. In the metacarpophalangeal joints, the subjects exhibited nearly complete active extension range of motion and an active flexion range of motion of 80.7°, while the injured hand’s grip strength was 94.0% that of the contralateral hand.[16]

Minifragment AO plates are useful for multiple metacarpal fractures in the same hand and in "combined" injuries where there is damage to the skin, tendon, and bone. In the past, miniplate fixation of metacarpal fractures has been eschewed because of concerns over hardware tenodesis. The author has found that a secure periosteal closure over miniplates and screws, along with the earlier mobilization that rigid fixation permits, has essentially eliminated this problem. In support of routine use of plates and screws are the results of biomechanical testing, which have shown that dorsal plate and screw fixation have the highest fatigue strength as well as resistance to bending and torsional forces while providing better axial rigidity.

A retrospective study by Aykut et al reported successful treatment of metacarpal fractures with open reduction and internal fixation with low-profile miniplates. The investigators found a decrease in mean angulation from 8.13° preoperatively to 3.55° postoperatively, in the posteroanterior plane. Mean grip strength, as registered on the Jamar hand dynamometer, was 41.05 kg in the fractured hands, versus 44.7 kg in the uninjured hands. The study had a mean follow-up period of 32 months.[17]

Other acceptable methods of fixation include 90/90 wiring, cerclage – tension band wiring versus figure-8 wiring placed in concert with intramedullary crossed K-wires.

Oblique metacarpal fractures

Oblique fractures of the metacarpals are less stable than transverse fractures. Deforming forces tend to cause foreshortening, angulation, or both, of the metacarpal. If the fracture is not angulated, foreshortening of up to 5 mm can be accepted, with some authors accepting up to 1 cm with good results. Malrotation requires closed reduction and pinning versus open reduction and internal fixation.

Metacarpal neck fractures

Fractures that are minimally angulated or displaced can be managed with simple immobilization for 4 weeks. The degree of acceptable angulation is controversial. Most surgeons agree that no more than 10° of angulation in the second and third metacarpals should be accepted without reduction.

The ulnar 2 metacarpals are more mobile at the CMC joint and can function well with greater amounts of angulation of the metacarpal shaft or neck. Some studies have shown little disability with up to 70° of angulation at the neck, but most surgeons would agree that no more than 40° should be accepted without reduction. As in other fractures of the hand, no rotational deformity is acceptable, as the resultant finger overlap leads to weakened grip and disability.

Closed reduction and immobilization with splinting or casting have been shown to maintain approximately 50% of the initial correction of angular deformity. Use of thermoplastic braces allows comfortable use of the hand with acceptable results. Operative fixation can be achieved by closed reduction (CR) versus open reduction (OR) with percutaneous pinning (PP), external fixation (EF) or internal fixation (IF) for metacarpal shaft fractures.

Metacarpal head fractures

Nondisplaced fractures can be managed with splinting for 3 weeks followed by protected active range of motion. Noncomminuted fractures with greater than 25% of the articular surface involved and/or greater than 1 mm of articular displacement should be treated with ORIF.

Use a dorsal approach, splitting the extensor tendon to view the joint. Perform anatomic reduction under direct vision. Care must be taken during the operation to avoid stripping of soft tissues to minimize the risk of avascular necrosis of the metacarpal head. Fixation of head fractures can be accomplished with K-wires, cerclage wiring, or interfragmentary screws. Fixation should be stable enough to allow early motion.

Comminuted fractures present a major problem. K-wire and cerclage wire fixation often fail. Multiple fine wires or even resorbable braided suture placed through drill holes made with fine K-wire as a drill bit may provide better reduction and, ultimately, greater reintegration of important small bone fragments. Condylar plate fixation is bulky and anatomic fixation is very difficult, with the exception of the second and fifth metacarpals. Acceptable results can be obtained by immobilization of the MCP joint in 70° of flexion for 2 weeks, followed by aggressive therapy. Skeletal traction on transverse pinning or external fixation may be necessary to distract a comminuted joint, especially if the base of the proximal phalanx is concomitantly fractured. Distraction radiographs can be helpful in determining if this is the most appropriate method of treatment.

Silicone arthroplasty of the MCP joint may be an option in severely comminuted joint injuries. It should not be used at the second MCP joint, as the prosthesis cannot withstand the stresses of forceful pinch. Silicone arthroplasty also should not be used in cases where soft tissue coverage is inadequate or when there is excessive bone loss. More durable pyrocarbon implants may prove themselves acceptable in areas where silicone has been untenable, specifically the second MCP. The same caveats apply, including adequacy of bone stock and good soft tissue coverage.

MCP dislocations

Dorsal MCP dislocations are classified as simple or complex. Both are the result of hyperextension injuries with avulsion of the volar plate. The distinction between the two is the difficulty of reduction. Simple dislocations are easy to diagnose since the MCP joint rests in 60-90° of hyperextension.

In this injury, the volar plate is distracted and not interposed in the MCP joint. Reduction is easily carried out under local or regional anesthesia in the emergency department. The wrist is flexed, followed by application of pressure to the dorsal base of the proximal phalanx. The MCP is then brought into flexion. Immediate motion can be started in a dorsal block splint that prohibits extension beyond neutral.

Complex dislocations are difficult to reduce and usually require open reduction. They are most common in the index and small fingers. On presentation, the MCP joint is only slightly hyperextended, with dimpling of the skin in the area of the proximal volar crease in the palm. In this injury, the volar plate avulses off the distal metacarpal and becomes interposed between the volar surface of the phalanx and the dorsal surface of the metacarpal head. See the images below.

Complex second metacarpophalangeal dislocation in Complex second metacarpophalangeal dislocation in a skeletally immature patient. Note the position of the finger and dimpling of skin on volar hand.
Radiograph of the hand of the patient in Image 6. Radiograph of the hand of the patient in Image 6.
Intraoperative photo of the second metacarpophalan Intraoperative photo of the second metacarpophalangeal joint of the patient in Images 6 and 7. Note the displaced volar plate between the metacarpal head and the proximal phalanx.

The metacarpal head seats between the flexor tendon and the lumbrical. These tendons tighten around the metacarpal neck when traction is applied while attempting closed reduction. A single, gentle effort at closed reduction may be attempted. The patient's wrist and IP joints are flexed, and an attempt is made to push the base of the proximal phalanx back into place. If this fails, open reduction through either a volar or dorsal approach should be performed. Caution is necessary with the volar approach, as the neurovascular bundle is usually tented over the metacarpal head. The A1 pulley is usually released, the volar plate removed from the joint, and the metacarpal head is reduced by pushing the base of the proximal phalanx distally. Early motion is instituted with use of a dorsally based extension-blocking splint.

Intraoperative Details

The author prefers open reduction done under tourniquet control. Percutaneous pinning can be done variably with or without the use of tourniquet. Inflation pressure should be selected to approximately 125 mm Hg above the patient's maximum systolic pressure. This setting usually minimizes tourniquet bleed-through. Rather than exceed tourniquet pressures of 300 mm Hg, the author prefers intraoperative blood pressure reduction. Higher pressures increase the risk of intimal injury to the brachial artery and should be avoided when possible. For each 30 minutes of time under tourniquet, 5 minutes of reperfusion time should be allowed before reinflation. A maximum of 2 hours of continuous inflation is permitted, after which a minimum of 20 minutes of reperfusion time is required prior to re-exsanguination.

Follow-up

Mockford et al conducted a review of a series of 16 male patients with 20 displaced transverse midshaft fractures of the second, third, and fourth metacarpal bones. The fractures were treated by antegrade intramedullary Kirschner wiring; a single, prebent, 1.6-mm Kirschner wire was inserted into the medullary canal through the metacarpal base across the fracture into the metacarpal head with the proximal wire protruding percutaneously. Early mobilization was started after stabilization. In this series, all fractures had united by an average time of 5.4 weeks, with 1 delayed union. Mean angular deformities were 4.05 degrees (range, 0-11 degrees) in the coronal plane and 0.75 degrees (range, 0-9 degrees) in the sagittal plane. Two patients developed a pin-site infection. All patients returned to normal activities by 8 weeks and to employment by 6 weeks.[18]

Complications

The primary complication of CMC injury is early arthritis of the joint. This can best be avoided by achieving an anatomic reduction and avoiding prolonged immobilization. Late treatment of CMC joint arthritis consists of fusion of the second through fourth joints and either fusion or interposition arthroplasty for the first and fifth CMC joints.

Complications from metacarpal shaft and neck fractures are rare. The most common complication is malunion, which does not usually limit function. If excessive angulation is not corrected, the hand exhibits loss of dorsal contour, prominence of the MC head can be appreciated in the palm, pain with grasp may be present, and pseudoclawing of the fingers may occur with MCP extension. Rotational deformities are more disabling, as the fingers cross when flexed, thus requiring more accurate reduction. If these deformities are not corrected acutely, a metacarpal rotational osteotomy may be required to eliminate scissoring and restore function.

Other complications can result from operative treatment. Tendinous adhesions from ORIF can be treated with hardware removal, tenolysis, and therapy. Tendinous adhesions from tendon transfixation with percutaneous K-wire and prolonged immobilization can usually be treated with tenolysis and therapy.

The most common complication of metacarpal head fractures is stiffness of the MCP joint followed by development of arthritis. Achieving adequate stability when performing ORIF is important to allow for early motion and prevent scarring about the joint with resultant limitations in motion.

Outcome and Prognosis

Overall, the result of treatment of metacarpal shaft and neck fractures has been good. Nonunion is rare but malunion is common. The resultant function despite malunion is typically good, provided that no rotational deformity exists and that the advised limits of angular deformity are respected.

Future and Controversies

New bioresorbable implants are being used more frequently for fixation of fractures. Biomechanical testing of polyglycolic acid (PGA) and poly (L-lactic acid) (PLLA) plates compare favorably in rigidity to titanium but are inferior in torsional testing. Self-reinforced PGA rods used in place of K-wires for intramedullary fixation have an initial bending stiffness of only 60% of the traditional stainless steel wires. When subjected to saline bath, PGA rods totally lose stability at 4 weeks.

As research into bioresorbable implants continues the new techniques and equipment derived may make these implants more cost-effective. Despite their disadvantages, their use precludes the need for implant removal at a second operation.