Metacarpal Fractures


Background

Trauma to the hand is exceedingly common, not infrequently resulting in metacarpal and phalangeal fractures and dislocations. [12Most of these injuries can be managed nonoperatively with immobilization or controlled mobilization. For certain intra-articular fractures, displaced and angulated fractures, unstable fracture patterns, combined or open injuries, as well as irreducible and unstable dislocations, surgical intervention may be required for restoration of function and appearance.

Most metacarpal fractures occur in the active and working population, particularly adolescents and young adults. In the United States, upper-extremity injuries result in over 16 million days off of work and a further 90 million days of restricted activity. Lost revenue and costs exceed 10 billion dollars. [34]

This article reviews metacarpal fractures and dislocations in the hand. Injury to the thumb metacarpals is also discussed in Bennett FractureRolando Fracture, and Thumb Reconstruction.

For patient education resources, see the First Aid and Injuries Center, as well as Broken HandBroken Finger, and Finger Dislocation.

Anatomy

Patterns of injuries result from the unique anatomy of the hand. Metacarpals are long tubular bones with an intrinsic longitudinal arch and a collective transverse arch. Bones are concave on the palmar surface and are joined proximally and distally by ligamentous attachments.

The second and third metacarpals are fixed rigidly at their bases, whereas the fourth and fifth carpometacarpal (CMC) joints are capable of at least 15° and 25° of motion, respectively. The thumb CMC saddle joint is highly mobile, and its unique motion and injury patterns are addressed more fully elsewhere (see Bennett Fracture and Rolando Fracture).

The CMC joints of the second and third metacarpals are very stable, and there is very little relative motion at these joints. The sawtooth articular arrangement combined and the strong dorsal and palmar CMC ligaments and metacarpal ligaments form very strong and relatively immobile joint capsules.

These joints are further stabilized by extensor carpi radialis longus and brevis tendon insertions on the bases of the second and third metacarpals, respectively. The insertion of the flexor carpi radialis at the base of the second metacarpal contributes as well. The articulation with the hamate and the fourth and fifth metatarsal bases allows for much freer movement, but the CMC and metacarpal ligaments are still very strong.

The insertion of the extensor carpi ulnaris (ECU) on the dorsal aspect of the ulnar fifth metacarpal base often provides a deforming force in fractures of the fifth metacarpal. Articular fractures of the base of the fifth metacarpal often occur between the metacarpal ligament insertions and the insertion of the ECU, resulting in proximal and dorsal migration of the fractured metacarpal due to the unopposed tendon action (often called "reverse Bennett fracture" due to its similarity to the injury in the thumb).

The metacarpophalangeal (MCP) joints are multiaxial condyloid joints capable of flexion, extension, and some lateral motion and circumduction. The cam-shape of the metacarpal heads leads to relaxation of the collateral ligaments in extension, permitting adduction and abduction of the finger. With about 70° of MCP joint flexion, the collateral ligaments become taut, stabilizing the finger for power pinch and grip.

Increased tension in the collateral ligaments with MCP flexion can be helpful in stabilizing the metacarpal head during reduction of a metacarpal neck fracture. MCP joints are routinely immobilized in at least 70° of flexion to maintain maximum stretch of these ligaments, thus lessening postimmobilization stiffness.

The volar plate is a cartilaginous structure on the palmar aspect of each MCP joint, which limits extension of the joint. The volar plate is thicker at its insertions on the proximal phalanges and weaker at the proximal metacarpal origin. Volar plates are interconnected through deep transverse intermetacarpal ligaments, which provide additional volar stability.

Pathophysiology

Metacarpal base injuries

CMC joints, especially the central joints, are quite stable. The metacarpal bases are held in position by dorsal and palmar CMC ligaments, as well as by interosseous ligaments. [3]

CMC dislocations may occur with or without fracture. Avulsion (chip) fractures of the metacarpal base, or fractures involving the dorsal carpus, frequently accompany CMC dislocations. A CMC dislocation should signal the examiner to look for either a fracture or dislocation of the adjacent joints. Disruption of the strong ligaments stabilizing the central CMC joints signifies high-force transmission; in these cases, the examiner must maintain an even higher level of suspicion for other injuries.

Fracture-dislocation of the fifth metacarpal base is a common intra-articular injury and has been dubbed the reverse Bennett fracture. A direct blow to the ulnar border of the hand tends to cause an extra-articular fifth metacarpal base fracture. Axial load more often results in an intra-articular or reverse Bennett fracture.

Generally, the volar radial one fourth to one third of the fifth articular base remains reduced. The remainder of the metacarpal displaces in a dorsal and ulnar direction. Displacement is caused by dynamic forces, similar to that seen with Bennett fracture of the thumb. The fifth metacarpal is the most mobile of the four ulnar CMC joints; therefore, it is prone to arthrosis from articular incongruity. [5]

Metacarpal shaft/neck fractures

Axial loading, direct blow, or torsional loading can cause metacarpal shaft fractures. Usually, the fractures are classified anatomically as transverse, oblique, or spiral. The fracture pattern often denotes the mechanism of injury, with direct or axial injury leading to transverse or oblique fractures and torsion leading to spiral fracture.

Fractures of the fifth metacarpal neck are among the most common fractures in the hand. Usually, these fractures are caused by striking a solid object with a closed fist and thus are dubbed boxer fractures, although this injury almost never occurs during boxing. Typically, a skilled fighter fractures the index metacarpal because instead of using a "roundhouse" motion, the blow comes straight from the body along the line of greatest force transmission.

Metacarpal head injuries

Fractures of the metacarpal head are rare injuries. These fractures are intra-articular and periarticular. If displaced, metacarpal head fractures usually require open reduction and internal fixation (ORIF). Direct trauma to the joint or an avulsion injury of the collateral ligaments is the typical cause. Injuries caused by direct trauma often are comminuted.

Metacarpophalangeal dislocations

Almost all MCP dislocations occur with the proximal phalanx displaced dorsally on the metacarpal head; there is no specific dorsal restraint to the MCP joint other than the joint capsule and extensor mechanism. The collateral ligaments remain intact, and the weak proximal insertion of the volar plate avulses from the metacarpal neck.

Etiology

Injury to the metacarpals is the result of either direct or indirect trauma. The nature and direction of the applied force determines the exact type of fracture or dislocation. [32 Specific injury patterns that occur from commonly seen trauma are as follows:

  • CMC injuries - Metacarpal base fractures and dislocations of the CMC joint commonly result from an axial load or other stress on the hand with the wrist flexed
  • Metacarpal shaft and neck injuries - Typically, metacarpal shaft fractures are produced by either axial loading or direct trauma, though torsional forces on the digits may also produce these injuries; 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 loading or direct trauma; avulsion fractures at the origin of the collateral ligaments are caused by forced deviation of the flexed MCP joint
  • MCP dislocations - Dorsal MCP dislocations are the most frequent dislocations, resulting from forced hyperextension of the digits

Epidemiology

Fractures of the metacarpals and phalanges constitute approximately 10% of all fractures. Metacarpal fractures account for 30-40% of all hand fractures. Fractures of the fifth metacarpal neck alone account for 10% of all fractures in the hand. The lifetime incidence of metacarpal fractures is approximately 2.5%.

Prognosis

Overall, results of treatment of metacarpal shaft and neck fractures have been very good. Nonunion is very rare, but malunion is common. [6The resultant function despite malunion usually is good, provided that there is no rotational deformity and that the previously mentioned limits of angular deformity are adhered to.

Ozer et al compared the clinical and radiographic outcomes of intramedullary nail (IMN) fixation with those of plate-screw (PS) fixation between 2004 and 2006 in 52 consecutive closed, displaced, extra-articular metacarpal fractures. [7Thirty-eight patients received IMN fixation, and 14 received PS fixation. Mean follow-up was 18 weeks in the IMN group and 19 weeks in the PS group.

The study found no significant differences in clinical outcomes between the two techniques. [7Operative time was shorter in the IMN group, but loss of reduction, penetration to the MCP joint, and secondary surgery for hardware removal were higher in the IMN group. The mean and median total active motion for the IMN group were 237º and 250º; for the PS group, 228º and 248º for the PS group. The mean DASH score was 9.47 in the IMN group and 8.07 in the PS group.

Harris et al studied the records and radiographs of 59 patients who underwent reduction of boxer's fractures using longitudinal traction and subsequent immobilization in a specially molded cast. [8On average, 80% of initial fracture angulation in the sagittal plane was corrected, and only 1º of this correction was lost at the discontinuance of casting (3-4 weeks). The authors concluded that this technique is highly effective in the treatment of boxer's fractures, with advantages over other casting techniques that include efficacy, ease, and improved patient tolerance.

Liporace et al studied 48 cadaver metacarpals to biomechanically assess the strength of the bicortical interfragmentary screw versus that of the traditional lag screw for oblique metacarpal fractures using one of the following four methods: 1.5-mm bicortical interfragmentary (IF) screw, 1.5-mm lag screw, 2.0-mm bicortical IF screw, and 2.0-mm lag screw. [9There was no significant difference between the fixation techniques with regard to displacement and ultimate failure strength, but there was a slight trend for a higher load to failure with the 2.0-mm IF screw and 2.0-mm lag screw.

This study supported previous clinical data showing that bicortical interfragmentary screw fixation is an effective treatment option for oblique metacarpal fractures. [9According to the authors, this technique provides an option for stabilization of small, difficult-to-control fracture fragments in metacarpal fractures.

Souer and Mudgal reviewed 19 patients with 43 closed metacarpal fractures treated by early ORIF with 2-mm plates. [10Eighteen patients recovered full range of motion (one patient was lost to follow-up). In only two metacarpals in two patients was implant removal required because of extensor irritation. Plating of multiple, closed metacarpal fractures, therefore, is a safe, reliable, and consistently reproducible treatment method, according to the authors.



History and Physical Examination

Injuries to metacarpal base

Many fractures and fracture dislocations of the metacarpal base are caused by substantial axial loads and frequently are associated with other injuries. Diagnosis usually is directed by the history and clinical examination. Tenderness, swelling, and loss of motion are common, as with any fracture or dislocation. Additionally, dorsal carpometacarpal (CMC) joint dislocations may be associated with marked swelling and sometimes a palpable stepoff. Stress of the fifth metacarpal reveals instability in cases of intra-articular fractures of that metacarpal base.

Fractures of metacarpal shaft and neck

Problems associated with metacarpal shaft fractures relate to shortening, rotation, and dorsal apex angulation. Of these, malrotation is the most critical. Minor rotational deformities can cause the fingers to overlap when the hand is made into a fist.

Rotational abnormalities are best judged clinically by comparing the injured and uninjured digits through a full range of motion (ROM). With flexion, each digit should point toward the scaphoid tuberosity. The plane of the nail should be similar between the injured digit and the contralateral corresponding finger when evaluated in an intrinsic plus position.

Like shaft fractures, metacarpal neck fractures usually are easily diagnosed by localized tenderness and swelling with loss of dorsal knuckle contour. The ring and small metacarpals are most commonly fractured.

Injuries to metacarpal head

Pain, swelling, and loss of motion are the key clinical signs of injury to the metacarpophalangeal (MCP) joint. Crepitus may be present with motion in intra-articular injuries.

Metacarpophalangeal dislocations

Dorsal dislocations are readily identified by a hyperextension posture of the digit with loss of joint flexion. Dimpling of the skin dorsally may also be observed. (See the image below.)

Complex 2nd metacarpophalangeal (MCP) dislocation Complex 2nd metacarpophalangeal (MCP) dislocation in skeletally immature patient; note position of finger and dimpling of skin on volar hand.

Plain Radiography

Plain radiography is the primary means of evaluating hand injuries beyond the history and physical examination. Any significant injury to the hand should be assessed with posteroanterior (PA), lateral, and oblique views. A 30° pronated lateral view for second and third metacarpal fractures and a 30° supinated lateral view for fourth and fifth metacarpal fractures are helpful. [1112(See the images below.)

AP radiograph of displaced 4th and 5th metacarpal AP radiograph of displaced 4th and 5th metacarpal fractures.
Lateral radiograph of displaced 4th and 5th metacaLateral radiograph of displaced 4th and 5th metacarpal fractures.
Oblique radiograph of 4th and 5th metacarpal fractOblique radiograph of 4th and 5th metacarpal fractures.
AP radiograph of 4th and 5th metacarpal fractures AP radiograph of 4th and 5th metacarpal fractures following intramedullary pinning.
Lateral radiograph of 4th and 5th metacarpals follLateral radiograph of 4th and 5th metacarpals following intramedullary pinning.

Carpometacarpal injuries

Carpometacarpal (CMC) fractures and dislocations are frequently difficult to visualize or fully characterize with standard radiographic projections. Additional oblique views, fluoroscopy, or computed tomography (CT) may be necessary. Additionally, traction radiographs can sometimes best demonstrate the bony and ligamentous injuries and their severity. This is accomplished by distracting the involved digits and obtaining multiple radiographic views.

CMC dislocation results in subtle loss of joint space as viewed on the anteroposterior (AP) projection. Often, this is seen as a broken sawtooth sign at the CMC joint. This sign may be accompanied by displacement noted on lateral or oblique views.

Assessing closely for other additional injuries is important. Because significant force is required to disrupt the strong CMC ligaments, fracture-dislocation of one CMC joint is often accompanied by an injury to one or more of its neighbors.

Metacarpal head fractures

Evaluation of these injuries may require additional imaging studies. Specifically, tomograms or CT scans may be necessary to visualize the fracture and degree of articular displacement.

The Brewerton view (metacarpophalangeal [MCP] joint flexed 65° with the dorsum of the proximal phalanx flat against the radiograph cassette and the beam angled 15° ulnar to radial) profiles the collateral recesses and is helpful for collateral ligament avulsion fractures.

Metacarpophalangeal dislocations

Most commonly, lateral radiographs reveal the dorsal displacement of the proximal phalanx. In more severe and complex dislocations, there may also coexist a metacarpal head fracture.

Metacarpal Fractures Treatment & Management


Approach Considerations

Most metacarpal injuries are managed by closed reduction and immobilization or sometimes controlled mobilization utilizing a dorsal block splint. Indications for operative treatment include the following:

  • Failure to achieve or maintain acceptable reduction using closed techniques
  • Open fractures
  • Multiple hand fractures
  • Complex injuries
  • Displaced intra-articular fractures
  • Fractures with severe soft-tissue loss requiring a stable skeleton

No absolute contraindications exist for treatment of metacarpal injuries. Almost all injuries are amenable to either immobilization or closed or open reduction, with or without fixation.

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 stainless-steel wires. When subjected to saline bath, PGA rods lose stability within 4 weeks.

New techniques and equipment may make these implants more cost-effective, and their use precludes the need for implant removal at a second operation. Further development of low-profile implants may allow more rigid fixation for certain problem fractures, thereby minimizing postoperative stiffness and perhaps diminishing the need for metal removal.

Approaches to specific injuries

Fractures and dislocations of metacarpal base

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

Carpometacarpal (CMC) dislocations and fracture-dislocations, especially when multiple, are unstable injuries. In the past, these fractures were managed by closed reduction and external immobilization, which frequently lead to grip weakness and residual pain. The current literature supports closed reduction, if joint congruity can be obtained, but with the addition of internal fixation.

Displaced fracture-dislocations of the fourth and fifth metacarpals, which are accompanied by fracture of the dorsal hamate, require open reduction and internal fixation (ORIF). Reverse Bennett fractures frequently need Kirschner-wire (K-wire) stabilization to counteract the deforming forces. If little articular incongruity is present, this may be a closed procedure.

Fractures of metacarpal shaft

Metacarpal shaft fractures tend to angulate apex dorsal with the head displaced palmarly due to the deforming pull of the interossei muscles. Only small amounts of angulation (≤10°) are acceptable in the second and third metacarpals. The fourth and fifth finger metacarpals are much more mobile, and angulation of 20° and 30°, respectively, can be accepted. The more proximal the fracture, the more pronounced the deformity and the less angulation that can be accepted. Any malrotation is an indication for surgical intervention. Shortening from 3-4 mm is well tolerated.

In addition to fractures that cannot be reduced and stabilized closed, fractures such as open fractures, multiple fractures, and malreduced subacute fractures are best addressed surgically.

Fractures of metacarpal neck

Metacarpal neck fractures rarely require surgery. Although the acceptable degree of angulation is controversial, as much as 50-60° of angulation can be tolerated with little or no functional deficit. This level of angulation is especially true for boxer's fractures of the fifth metacarpal neck. Despite overall good functional results, this degree of angulation alters dorsal knuckle contour and may result in a tender palmar mass with heavy gripping. Though quite unusual, fracture rotation is an indication for surgical intervention.

Fractures and dislocations of metacarpal head

Except for some collateral ligament avulsion fractures, metacarpal head fractures are intra-articular and, if displaced, should be treated with ORIF, the goal being anatomic reduction and early mobilization.

Medical Therapy

Treatment of metacarpal fractures and dislocations is primarily nonoperative. [131415Management usually consists of sedation or local anesthesia, followed by closed reduction of the fracture or dislocation. A forearm-based splint is then applied and held in place with a loose compressive wrap. The goals of nonoperative management are to obtain alignment and stability and to begin motion of the fingers and wrist as soon as possible.

Generally acceptable reduction of metacarpal fractures includes articular congruity of less than 2 mm and angulation and rotation that do not interfere with function or cause significant cosmetic deformity. Specifics on acceptable reduction and indications for surgical management are discussed below (see Surgical Therapy).

Although most fractures and dislocations can be treated nonoperatively, it may be beneficial to perform closed reduction in a setting where percutaneous pinning can be performed if the reduction cannot be maintained without some form of internal stabilization. [12161718192021]

Immobilization of most metacarpal fractures follows a few simple guidelines, including the following:

  • Fracture splints should be forearm-based and should allow for motion of the interphalangeal (IP) joints
  • Splints should extend over the dorsal and palmar aspect of the entire metacarpal being treated
  • Generally, the wrist should be placed in 20-30° of extension; the metacarpophalangeal (MCP) joints should be immobilized in 70-90° of flexion, with the dorsal aspect of the splint extending to the IP joints; and the volar aspect should end at the distal palmar crease
  • Buddy taping the fingers of the involved metacarpal can aid in maintaining rotational control
  • After a short period of immobilization, patients may be encouraged to use the fingers on the affected hand to maintain motion

Metacarpal base fractures

Fractures of the metacarpal base require reduction if there is greater than 2 mm of articular surface displacement or if there is significant angular deformity or dislocation of the CMC joint. Anesthesia for the reduction is usually accomplished by conscious sedation or regional block; local hematoma block is usually inadequate.

The reduction is accomplished using a combination of traction and direct digital pressure, usually by the physician's thumb. The wrist should be splinted in 20-30° of extension after reduction in order to decrease the deforming pull of the wrist extensors, and the MCP joints should be flexed.

Fractures through the base of the fifth metacarpal require special consideration. These fractures are often intra-articular, with the fracture line between the insertion of the strong intermetacarpal ligaments and the insertion of the extensor carpi ulnaris (ECU) tendon. The pull of the ECU becomes a deforming force, causing the fractured metacarpal to displace proximally and dorsally. This is similar to the Bennett fracture of the thumb ("reverse Bennett fracture").

Management of these fractures usually requires ORIF or closed reduction and percutaneous pinning. Minimally or nondisplaced fractures should be splinted in the same manner described for other CMC injuries.

Immobilization of reduced metacarpal base fractures or nondisplaced fractures should be continued for a minimum of 3-4 weeks. Active motion of the finger IP joints should be encouraged throughout the immobilization period.

Metacarpal shaft fractures

Most closed metacarpal shaft fractures are best treated nonoperatively. Because of the adjacent intact metacarpals and the strong intermetacarpal ligaments, isolated third and fourth metacarpal fractures are particularly stable.

The amount of acceptable angulation varies depending on the location of the fracture and the specific metacarpal involved. Less angulation can be accepted in fractures closer to the CMC joints, as the amount of deformity appears accentuated. Greater angular deformity can be accepted in the fourth and fifth metacarpals, because the greater mobility of the CMC joints compensates for this deformity. General guidelines for acceptable angulation are 10° for the second and third metacarpals, 20° for the fourth metacarpal, and 30° for the fifth metacarpal.

Reduction of displaced metacarpal shaft fractures is best accomplished by using a technique developed by Jhass. [22The fracture is anesthetized with the hematoma block. The affected finger MCP joint and the proximal IP (PIP) joints are flexed to 90°, and the fracture is reduced by applying upward pressure on the middle phalanx and downward pressure over the dorsal apex of the fracture. Flexing of the MCP joint tightens the collateral ligaments and provides a rigid lever for reduction. The finger then can be used to control or correct the rotation.

After reduction, the fracture is held via splinting or can be pinned to maintain reduction. Do not use the Jahss splinting technique (ie, the finger is kept in flexion with upward force applied across the PIP joint), because the risk of skin necrosis and flexor contracture is prohibitive. Immobilization should be limited to less than 4 weeks, as stiffness and tendon adhesion limit range of motion and lead to an unfavorable result.

Metacarpal neck fractures

Minimally angulated or displaced fractures can be managed with simple immobilization for 3-4 weeks. The degree of acceptable angulation is controversial.

Most surgeons agree that no more than 10-15° of angulation in the second and third metacarpals should be accepted without reduction. The lateral digits are more mobile at the CMC joint and function well with greater amounts of angulation of the metacarpal shaft or neck. Though some studies have shown little disability associated with fifth metacarpal neck fractures angulated as much as 70°, most surgeons advocate reduction of those fractures with more than 45° of angulation.

As in other fractures of the hand, no rotational deformity is acceptable, as the resultant finger overlap with grip leads to weakness and disability. Reduction of metacarpal neck fractures is accomplished by the same method as metacarpal shaft fractures (see above). Closed reduction and immobilization with splints or casts has been shown to maintain approximately 50% of the initial deformity correction.

Metacarpal head fractures

Nondisplaced fractures can be managed with splinting for 3 weeks, followed by gentle motion. Fractures in which the articular surface is displaced greater than 1-2 mm should be managed operatively. Splinting of metacarpal head fractures should incorporate the MCP joint. This can be accomplished with the ulnar gutter splint for fourth and fifth metacarpal fractures.

Metacarpophalangeal dislocations

Dorsal MCP dislocations are classified as simple or complex. Both are the result of hyperextension injuries with avulsion of the palmar plate. The distinction between the two types is the difficulty of reduction.

Simple dislocations are easy to diagnose because the MCP joint rests in 60-90° of hyperextension. In this injury, the volar plate is distracted and not interposed between the bone ends.

Reduction of simple MCP dislocations is carried out easily with local or regional anesthesia in the emergency department. The wrist and IP joints are flexed—and the finger is very gently distracted—and a volarly directed force from the dorsum brings the joint into at least 50° of flexion. One must avoid hyperextension (accentuation of the deformity) during reduction so as to not interpose the volar plate. Immediate motion can then be started in a dorsal block splint that prohibits extension beyond 30°.

MCP dislocations that are not readily reducible are characterized as complex. The reduction is prevented by either interposed soft tissue or "buttonholing" of the metacarpal head. On presentation, the MCP joint is only slightly hyperextended with the distal joints mildly flexed. The involved digit deviates toward the adjacent central digit. A prominence is present in the palm with dimpling of the skin in the area of the proximal volar crease. Dorsally, a depression is palpable proximal to the base of the proximal phalanx. The patient cannot actively flex the digit. These dislocations require operative reduction.

Surgical Therapy

Although closed management of these injuries is the rule rather than the exception, certain fractures and dislocations require operative intervention to ensure satisfactory restoration of function and cosmesis. [1617181921232425262722829]

Adequate surgical planning requires adequate preoperative assessment. A thorough neurovascular examination should be accomplished before any intervention. Obtaining adequate radiographs to view all potential injuries in advance of surgery is essential to avoid unexpected surprises. Intraoperative fluoroscopy or radiography should be used to ensure adequate reduction before the patient leaves the operating room. Additionally, joint motion should be assessed after fixation under anesthesia so that postoperative expectations can be established.

Carpometacarpal injuries

Adequate reduction of CMC fractures and dislocations usually can be obtained in a closed manner; however, reduction may be difficult to maintain because of the deforming forces discussed earlier. Pin fixation is an effective means of stabilization. In addition, reduction of articular fragments is difficult to judge in these poorly visualized joints. Depending on the specific injury and means of fixation, patients are immobilized postoperatively for 3-6 weeks. Often, motion may be initiated prior to pin removal.

Fractures of the fifth metacarpal base (reverse Bennett fractures) often require operative intervention. This fracture displaces dorsally and proximally due to the deforming pull from the ECU tendon and, to a lesser extent, the flexor carpi ulnaris (FCU) through the pisometacarpal ligament.

For fifth metacarpal fractures with large fragments, closed reduction often is easily accomplished; however, the reduction can be difficult to maintain without pin fixation. For comminuted intra-articular fractures, open reduction may be required to achieve an acceptable joint. Stable fixation can be achieved with K-wire fixation between the fifth and fourth metacarpals, which can be supplemented with an additional K-wire across the fifth CMC joint.

Fracture-dislocations of the mobile fourth and fifth metacarpals associated with displaced fractures of the dorsal hamate require ORIF. Fixation can be accomplished with either pins or mini-fragment screws.

Multiple CMC dislocations are high-energy injuries and often require ORIF. Closed reduction is first attempted using longitudinal traction and direct pressure over the displaced metacarpal bases. If satisfactory reduction is accomplished, percutaneous K-wires provide adequate stabilization. If reduction is difficult, carefully evaluate for intra-articular fragments, which are often difficult to see and may block reduction. If adequate closed reduction cannot be obtained, open reduction should be accomplished and the reduction internally fixed with either pins or screws.

Metacarpal shaft injuries

Open fractures require operative debridement and irrigation, followed by stable internal or external fixation. Metacarpal neck fractures with small lacerations over the MCP joint are assumed to be the result of a human bite (fight bite) and are treated operatively using joint lavage and appropriate antibiotics, usually penicillin or oxacillin.

Operative treatment of metacarpal shaft fractures varies according to the type of fracture, amount of displacement, location of fracture, and degree of soft-tissue injury.

Transverse fractures

Transverse fractures can be managed with longitudinal pins, transverse pins, crossed pins, intramedullary pinning, or tension band wiring. Longitudinal pins are placed distal to proximal, starting the pin medial or lateral to the MCP joint at the origin of the collateral ligaments and driving the pin down the shaft of the metacarpal across the fracture site. Crossed pins can be started proximally or distally, should cross near the fracture site, and should exit the far cortex.

The percutaneous pins can be cut short and left under the skin, and early motion can be instituted. The pins can be removed at 4-6 weeks or when radiographic healing has occurred.

K-wires placed transversely through the fractured metacarpal into the adjacent nonfractured metacarpal can be used to stabilize transverse fractures. Usually, two K-wires are placed distal to the fracture, with one K-wire placed in the proximal fragment.

Intramedullary (bouquet) pinning is a technique that, though sometimes technically challenging, has produced good results. Intramedullary pinning is best for fairly distal metacarpal fractures. Prebent small K-wires, with the sharp point removed, are introduced through a small corticotomy proximal to the fracture site. The fracture is reduced and the pins advanced by hand across the fracture site through the medullary canal. Usually, three or four K-wires are utilized. Early motion can be instituted, and hardware removal is not necessary.

Tension band wire fixation, with the wire crossing on the dorsal shaft of the metacarpal, provides an excellent low-profile method of fixation if no significant comminution exists. The tension band is usually secured to crossed wires after the crossed pinning technique has been accomplished to provide additional stabilization. The major disadvantage of this technique is that it is an open procedure.

Short oblique fractures

Short oblique fractures of the metacarpal are generally unstable and tend to angulate and rotate. If the fracture is not rotated, shortening of up to 4-5 mm can be accepted and the fracture treated closed.

Longitudinal pin fixation or transverse pin fixation to the adjacent metacarpal can be used to supplement closed management. Care should be used with longitudinal pin fixation, as rotatory control may not be maintained.

Small low-profile plate-and-screw fixation may be necessary to maintain rotatory control and alignment.

Long oblique or spiral fractures

Long oblique fractures, in which the length of the fracture is greater than twice the bone diameter, which cannot be reduced by closed methods, is often best treated with multiple-lag-screw fixation.

Fixation with multiple lag screws usually allows early mobilization, and if the mini screws are countersunk, the metal rarely becomes symptomatic. K-wires often provide adequate fixation as well.

Comminuted fractures

Comminuted fractures, with or without the loss, can be managed by transverse K-wire fixation or ORIF. If closed reduction of the fracture is possible, placing two K-wires transversely into the adjacent metacarpal distally and placing one K-wire transversely proximally may provide adequate stabilization to maintain reduction and allow healing.

If closed reduction of the fracture with transverse K-wires is not possible, ORIF using plate-and-screw fixation, with or without supplemental bone graft, should be accomplished. Though new generation low-profile implants have lessened the incidence of postoperative tendon adhesions, plate-and-screw fixation should be used sparingly.

Severely comminuted fractures associated with bone loss may require the use of an external fixator. External fixator frames can be constructed with K-wires and cement or acrylic and are also available in commercial sets.

Metacarpal neck fractures

The treatment of metacarpal neck fractures is very similar to that of metacarpal shaft fractures (see above). Most metacarpal neck fractures can be managed nonoperatively. Requirements for operative fixation include severe angulation not treatable by closed means, unstable rotational deformity, or significant comminution or bone loss.

Operative treatment usually is best accomplished with closed reduction and percutaneous pinning. Longitudinal pinning techniques or crossed pins are usually adequate to maintain reduction. For very unstable fractures, internal fixation can be accomplished with dorsal tension band wiring.

Metacarpal head fractures

Nondisplaced fractures can be managed with splinting for 3 weeks, followed by gentle motion. Noncomminuted fractures involving more than 10-15% of the articular surface and greater than 1-2 mm of articular displacement should be reduced by means of open technique via a dorsal approach that involves either splitting the extensor tendon or incising the sagittal band laterally to view the joint. Take care to avoid stripping soft tissues from the fracture fragments, in order to minimize the chance of devascularization.

Fixation of head fractures can be accomplished with K-wires, cerclage wiring, or interfragmentary screws. Ideally, fixation should be stable enough to allow early motion.

Comminuted metacarpal head fractures present a major problem. K-wire and cerclage wire techniques often fail, rigid fixation rarely is possible, and the bulk of condylar plates are problematic. For those fractures that are not amenable to internal fixation, consider external fixation, skeletal traction, or simple immobilization of the MCP joint in 70° of flexion for 2 weeks, followed by intensive therapy.

Some authors advocate immediate silicone implant arthroplasty for severely comminuted MCP joint injuries. Certainly, this prosthesis is preferred for older patients who place fewer demands on their hands and for joints other than the index MCP joint. Implant arthroplasty should not be used in cases where soft-tissue coverage is inadequate or when there is excessive bone loss. Finally, MCP joint arthroplasty is a salvage procedure and as such may be used later without disadvantage. Only in very rare and unique clinical situations should it be considered as first-line treatment.

Metacarpophalangeal dislocations

Open reduction is frequently required for complex dorsal dislocations. Like simple dislocations, these complex dislocations are most common in the index finger and the small finger (border digits).

On presentation, the MCP joint is only slightly hyperextended with the distal joints mildly flexed. The involved digit deviates toward the adjacent central digit. A prominence is present in the palm, with dimpling of the skin in the area of the proximal volar crease. Dorsally, a depression is palpable proximal to the base of the proximal phalanx. The patient cannot actively flex the digit.

In complex MCP dislocations, the volar plate avulses from the distal metacarpal and becomes interposed between the volar surface of the phalanx and the dorsal surface of the metacarpal head. In the index finger, the metacarpal head may buttonhole between the flexor tendons ulnarly and the lumbrical radially. These structures tighten around the metacarpal neck when traction is applied during attempted closed reduction.

In the small finger, the entrapping structures include the lumbricals and flexor tendons radially and the abductor and short flexor ulnarly. Also, in both digits, the collateral ligaments tighten around the narrow metacarpal neck with distraction, further preventing reduction. A single gentle attempt should be made at closed reduction. The patient's wrist and IP joints are flexed, and a dorsal-to-volar translation force is applied to the base of the proximal phalanx. Distraction is avoided or minimized.

If this attempt fails, open reduction should be performed through either a volar or a dorsal approach. Though the volar approach may provide more direct visualization of the structures preventing reduction, caution must be exercised because the neurovascular bundle is usually tented over the metacarpal head. After open reduction, internal fixation is rarely required, and early motion is instituted with the use of a dorsal extension-block splint.

Irreducible volar MCP joint dislocations are exceedingly rare. Two structures have been credited with preventing closed reduction: dorsal capsule avulsed proximally and volar plate avulsed distally. This injury should be approached dorsally to reduce the dislocation.

Postoperative Care

Most surgery on the hand is undertaken to promote function. Whenever possible, it is essential that early motion be instituted to ensure a good outcome. Delaying motion beyond 3-4 weeks can lead to arthrofibrosis and a poor functional outcome. Optimal surgical treatment should allow for near-immediate postoperative motion, and patients should be encouraged to move their fingers on a daily basis.

Complications

Complications of the treatment of CMC joint fractures and dislocations include recurrent dislocation and arthritis of the involved joint. Arthrosis is more likely to involve the relatively mobile fourth and fifth CMC joints and can best be avoided by achieving stable anatomic reduction and avoiding prolonged immobilization. Late treatment of CMC joint arthritis consists of joint fusion. Little disability is associated with this procedure.

Complications from metacarpal shaft and neck fractures are rare. The most common complication is malunion with persistent dorsal apex angulation or rotational deformity. Function is more likely to be affected if the malunion is proximal, involves either the second or the third metacarpal, and is rotatory in nature.

If excessive angulation is not corrected, the hand exhibits loss of dorsal contour, prominence of the MC head in the palm, pain with grasp, and possibly pseudoclawing of the fingers with MCP extension. A rotational malunion causes digital overlap with finger flexion. If these deformities are not corrected acutely, a metacarpal osteotomy may be required to restore anatomy and function.

MCP joint stiffness is a frequent problem following the treatment of metacarpal head fractures. This problem is minimized by achieving a stable anatomic reduction allowing early motion.

Other complications result from operative treatment. Plates and other prominent hardware frequently cause tendon adhesions and stiffness. In addition, the metal may become tender to palpation. Treatment includes hardware removal and extensor tendon tenolysis.


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