Hand Surgery
1st Edition

11
Intraarticular Injuries of the Metacarpophalangeal and Carpometacarpal Joints
Lisa L. Lattanza
Paul D. Choi
Training and reading in hand surgery do not prepare one for every injury and problem encountered. Although textbooks are good, the treatment of complex fractures is not effortless. Treatment often becomes a matter of opinion as to what the most important ingredient/technique is to obtain the desired result and optimal function of the digits and hand after injury. The following pages give the key ingredients for successful evaluation as well as attempt to explain the numerous accepted methods of treatment for these injuries.
METACARPOPHALANGEAL JOINT
Surgical Anatomy and Biomechanics
The metacarpophalangeal joints of the fingers allow multiplanar motion. The motions available are flexion, extension, abduction, adduction, and circumduction. This is possible because of the complex shape of the metacarpal head and its large articular surface as well as the arrangement of the soft tissue constraints. The total range of motion of the metacarpophalangeal (MCP) joint is greater than any other finger joint (1). The shape of the metacarpal head is trapezoidal in cross section, elliptical in the sagittal plane, and longer in the dorsal-volar plane than in the distal-proximal plane. The articular surface of the proximal phalanx is shallow and concave and congruent with the metacarpal head throughout range of motion (2).
The collateral ligaments have been shown to be the primary stabilizers of the MCP joint in all planes of motion (3). They originate from depressions on each side of the metacarpal head dorsal to the axis of rotation. The ligaments extend obliquely and distally and insert onto tubercles at the base of the proximal phalanx. The accessory collateral ligaments originate just volar to the collateral ligaments and insert into the volar plate. Because of their relationship to the axis of motion and the shape of the metacarpal head (wider volarly than dorsal), the collateral ligaments are more taut in flexion than extension. However, the accessory collateral ligaments with their more volar position are taut in extension and lax in flexion. The interosseous and lumbrical tendons also add to the lateral stability of the joint.
Volar stability of the joint is provided by the volar plate (4). It is loose and membranous proximally and becomes thicker and firmly attached to the proximal phalanx distally. The proximal portion forms the volar recess, which facilitates flexion of the proximal phalanx (5). The volar plate is contiguous laterally with the adjacent deep intermetacarpal ligament, which helps confer greater stability to the construct. The flexor tendons and A1 pulley are directly volar to the volar plate. The A1 pulley attaches to the volar plate.
The dorsal structures contribute less stability to the joint than the volar and lateral structures (3). The dorsal capsule is loose and somewhat thin to accommodate motion. The other dorsal structures include the extrinsic extensor tendons (extensor digitorum communis to all four digits and the extensor indicis proprius and extensor digiti minimi to the index and small finger). The extensor tendons are held in position by the sagittal bands of the extensor hood, which volarly connect with the transverse metacarpal ligament.
The neurovascular bundles course in the lumbrical canal anterior to the muscle. This position makes them vulnerable during dislocation and volar approach to an irreducible dislocation.
The MCP joint of the thumb is also a condyloid joint with similar anatomy to the MCP joint of the fingers. However, stability rather than mobility is more critical for thumb MCP joint function. The majority of the mobility of the thumb is provided by the basal joint and the interphalangeal joint. Stability of the MCP joint is necessary for pinch and grasp. There is relatively little inherent skeletal stability. The range of motion of the MCP joint of the
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thumb is more variable than any other joint because of the varying degree of curvature and shape of the metacarpal head (6). The stability is provided by the collateral ligaments, volar plate, capsule, and tendons. The amount of stability varies from one individual to another and even from one side to the other in the same individual (7).
Motion of the MCP joint of the thumb is more limited than in the fingers, especially with regard to flexion and extension. Although some abduction and adduction exist in the thumb, it is not desirable for too much motion in this plane to exist, as the thumb would lose necessary stability for pinch and grasp. Because of its unprotected position, the thumb is vulnerable to injuries that can render it unstable.
Metacarpophalangeal Joint Dislocations
Pathophysiology
Dislocations of the MCP joint are less common than proximal interphalangeal joint dislocations. Although in theory the border digits (index and small fingers) are most vulnerable to injury, the index finger is more frequently involved than the small finger (8). The thumb is also more frequently injured than the small finger (9). There is some confusing terminology in the literature. A simple dislocation is defined as being easily reducible and is referred to as a “subluxation” by some authors. A dislocation that is not reducible is referred to as a “complete dislocation” by some and a “complex dislocation” by others. It seems clearer to simply refer to the dislocation as either reducible or irreducible. Dorsal dislocations are more common than volar dislocations. Only 11 volar dislocations have been reported in the English literature (10). All but one of these was irreducible.
Dorsal dislocations occur from a forceful hyperextension injury to the MCP joint, often from a fall on an outstretched hand. The volar plate is avulsed from its attachment on the metacarpal. In a reducible dislocation, the proximal phalanx cartilage remains in contact with the dorsal articular cartilage of the metacarpal head. The volar plate is not interposed in the joint (Fig. 1A). The collateral ligament may be torn if there is a rotational component to the injury, but it also may be intact.
Irreducible dislocations occur by the same mechanism as reducible dislocations. However, the volar plate becomes interposed in the joint (Fig. 1B). Kaplan’s (11) classic article describes the pathogenesis and anatomy of the irreducible dislocation. He is largely credited with this description, although the first descriptions date back to 1855 by Malgaigne in the European literature (12) and Battle in 1888 (13) and Barnard in 1901 in the English literature (14).
In addition to the volar plate becoming entrapped in the joint, the metacarpal head can also become entrapped in the tendons and ligamentous structures as it displaces volarly. This has been described by many authors, as referenced previously. In the index finger, the flexor tendons are displaced ulnarly and the lumbrical radially. In the small finger, the common tendon of the abductor digiti minimi and flexor digiti minimi is displaced ulnarly, with the flexor tendons and lumbrical displaced radially. In both cases, the natatory ligament is displaced dorsally and the superficial transverse metacarpal ligament proximally. These structures entrap the metacarpal head on four sides (Fig. 2). This, along with the interposed volar ligament, prevents closed reduction. The neurovascular bundle is tented over the volar surface of the metacarpal head. In the index finger, it is the radial neurovascular bundle, and in the small finger, it is the ulnar bundle.
FIGURE 1. Schematic of a dorsal dislocation of a metacarpophalangeal joint. A: Simple complete. B: Complex complete.
In the volar dislocation, four different structures have been reported in the literature that can prevent closed reduction. The dorsal capsule can be avulsed from the proximal metacarpal and become interposed (15,16 and 17). The volar plate can be avulsed distally, becoming entrapped in the joint (17,18 and 19). The volar plate can be trapped with the collateral ligament or dorsal capsule (19). The junctura tendinum connecting the fourth and fifth finger extensor digitorum communis tendons can slip distal and volar to the metacarpal head, becoming trapped between the meta-carpal neck and the proximal phalanx base (10).
Evaluation
The history is usually that of a fall on the volar surface of the outstretched hand with hyperextension of the MCP joints in dorsal dislocations. Ironically, the simple or reducible dorsal dislocation causes more of a visible deformity than the irreducible dislocation. In the reducible dislocation, the proximal phalanx is perched in a hyperextended
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position on the metacarpal head with reciprocal flexion of the proximal interphalangeal joint. In contrast, with the irreducible dorsal dislocation, the proximal phalanx lies on the dorsal surface of the metacarpal shaft in a bayonet position. Clinically, the deformity appears less severe. If the index or small finger is dislocated, it deviates toward the midline. There can be dimpling on the volar surface of the skin. The metacarpal head is palpable and prominent in the palm. Active or passive MCP motion is impossible.
FIGURE 2. A: Diagram illustrating an entrapped fifth metacarpal head. B: Diagram illustrating an entrapped second metacarpal head. MP, metacarpophalangeal.
In the much more uncommon volar dislocation, pain and swelling are seen at the MCP joint. The patient may retain the ability to flex the MCP joint, but there is an extensor lag. A depression can be seen dorsally between the metacarpal head and the base of the proximal phalanx (10).
Radiographs confirm the diagnosis (Fig. 3). An anteroposterior, lateral, and oblique view should be obtained. The anteroposterior radiograph shows widening of the joint space secondary to the interposed volar plate (20). If a sesamoid is seen within the joint, this is pathognomonic of volar plate entrapment and therefore an irreducible dislocation (21,22 and 23). The lateral view shows the proximal phalanx lying dorsal or volar to the metacarpal. However, sometimes overlapping of the digits on the lateral view may obscure the dislocation. In these instances, it may be best seen on an oblique view. Always look carefully for concomitant fractures of the base of the proximal phalanx and metacarpal head, which have approximately 50% incidence with a dislocation (24).
Nonoperative Treatment
Unlike most other types of dislocations, simple distraction of the joint as a reduction maneuver not only does not reduce the dislocation, but it can also convert a reducible dislocation to an irreducible dislocation. The reduction should be attempted by someone with experience treating this problem. Even in experienced hands, many MCP joint dislocations still require open reduction. An atraumatic reduction is the goal. As with any attempted closed reduction of a joint, adequate anesthesia is key. The first step in reducing a dorsal dislocation is to flex the wrist and the proximal interphalangeal joint to relax the flexors of the digits. The MCP joint is then hyperextended to 90 degrees (accentuate the deformity). Pressure is applied to the dorsal surface of the proximal phalanx against the MCP joint while the proximal phalanx is carefully brought into flexion (Fig. 4). If this fails, this means that either the volar plate is interposed in the joint or that the metacarpal head is buttonholed through the volar structures as previously described. An open reduction must be done.
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FIGURE 3. Radiograph of a dorsal metacarpophalangeal joint dislocation of the index and middle finger.
Dorsal dislocations in the thumb are treated in the same manner. In a report by Takami et al. (25), eight out of nine dislocations of the thumb MCP joint were successfully treated closed. They propose, as does Ruby (26), that because there is no deep transverse metacarpal ligament in the thumb holding the volar plate dorsally, closed reduction is often possible. In irreducible dislocations, it is the volar plate or flexor tendon that blocks the reduction.
Although it is reasonable to attempt a closed reduction of a volar MCP dislocation, there are no reported cases in the literature to date of a successful closed reduction (2). The reduction maneuver is similar to that for a dorsal dislocation except that the MCP joint is flexed and pressure is applied to the volar surface of the proximal phalanx as it is brought into extension. If this fails, proceed with an open reduction.
FIGURE 4. Illustration of correct and safe metacarpophalangeal joint dislocation reduction maneuver.
Surgical Management
There is still disagreement in the literature regarding the best approach for the irreducible dorsal dislocation. The volar approach to open reduction was advocated in 1957 by Kaplan (11). Since Farabeuf’s description in 1876, many others have also advocated the dorsal approach (27,28,29 and 30). They believe that there is less risk of injury to the neurovascular bundle and that the structure blocking the dislocation is the volar plate, which can be easily and safely removed from the joint through this approach. Others report up to a 50% incidence of associated metacarpal head fractures, which are more readily treated from a dorsal approach (31). There are probably an equal number of practitioners who advocate the volar approach (5,32,33,34,35 and 36). The main argument is that it is not just the volar plate that can block reduction of the joint. As previously described, the tendons and ligamentous structures can also trap the metacarpal head volarly, and these structures cannot be reduced through a dorsal approach. Eaton (37) described a technique for atraumatically reducing the joint by dividing the A1 pulley, which then releases tension on the flexor tendon portion of the “noose,” allowing the volar plate and joint to reduce. In a clinical and cadaver study by Barry et al. (38), they also found the volar plate to be the main obstacle to reduction. However, they did advocate the volar approach for experienced hand surgeons so that the anatomy of the volar plate could be restored, preventing the theoretical risk of instability. They recommended the safer dorsal approach for the “occasional hand surgeon” to minimize the possibility of damage to the neurovascular bundle.
Authors’ Preferred Method of Treatment
In treating a dorsal MCP joint dislocation, a closed reduction with adequate anesthesia is always attempted first. If the reduction is successful, the stability of the joint is assessed while the hand is still anesthetized. The patient is placed in a dorsal extension block splint at 30 degrees of MCP joint flexion. Active range of motion within the patient’s stable range is begun the next day, with gradual allowance of full range of motion between the second and third week. The splint is discontinued between the third and fourth week depending on stability and patient compliance.
If closed reduction is unsuccessful, an open reduction is done through a volar approach. As with most procedures in hand surgery, it is preferable to identify and protect the neurovascular structures rather than to avoid them. A transverse incision is made between the proximal and distal palmar creases. It is extended across the width of the joint. It is imperative that the incision be made very carefully. Once the skin incision is made, the neurovascular bundle is identified
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lying tented over the metacarpal head (Fig. 5). It is carefully dissected free and protected. The superficial palmar fascia is now divided. An atraumatic reduction can now be accomplished by completely releasing the A1 pulley, which has been displaced dorsally with the flexor tendons and volar plate. Once the A1 pulley is incised, the tension is released and the volar plate and metacarpal head can be reduced. Careful inspection for concomitant fractures and osteochondral lesion is undertaken. If the joint is unstable, the volar plate is repaired. Stability of the joint through its full range of motion is tested to direct postoperative rehabilitation.
FIGURE 5. Index finger metacarpophalangeal joint dislocation. Volar approach to the joint showing the digital nerve lying tented over the metacarpal head.
The patient is placed in a dorsal extension block splint in approximately 30 degrees of flexion to protect the volar plate repair and prevent redislocation. Active range of motion and gentle active assistive range of motion from full flexion to 30 degrees’ flexion are begun within the first postoperative week and continued for 2 weeks. Between postoperative weeks 2 to 4, a removable dorsal extension block splint at 10 degrees of flexion is used, and exercises are continued. During weeks 4 to 6, the splint is worn only for protection, and the patient is out of the splint the majority of the time. The splint is discontinued at 6 weeks.
It is necessary to mention the dorsal approach for surgeons who may not feel comfortable with the volar approach. A longitudinal incision gently curved over the MCP joint is made. The extensor tendon and joint capsule are split longitudinally and retracted. The volar plate is then visible. The volar plate is incised longitudinally, allowing it to fall to the sides as the previously described reduction maneuver is applied (Fig. 6). Rehabilitation is the same as for the volar approach.
Volar dislocations are approached through a dorsal incision, allowing access and reduction of the structures blocking the reduction.
FIGURE 6. Dorsal approach to a metacarpophalangeal joint dislocation. The entrapped volar plate is incised longitudinally, allowing reduction of the joint.
Complications
Many of the complications of this injury can be reduced or avoided by proper prompt diagnosis and appropriate treatment. The main complication of this injury is joint stiffness secondary to soft tissue trauma at the time of dislocation. This is best treated by early supervised therapy for active and passive range of motion as described. Patients may continue to show improvement in range of motion even 6 months after injury. Occasionally, joint contracture release or tenolysis may be necessary. Many complications, such as stiffness and nerve injury, are secondary to failure to recognize the injury and delaying treatment, improper surgical technique, or delayed or inappropriate rehabilitation.
Late complications of degenerative arthritis and osteonecrosis cannot be avoided and should be treated as they arise. Digital nerve damage can be a complication that again is best avoided by proper surgical technique and understanding of the pathomechanics of the injury. In skeletally immature patients with this injury, premature closure of the physis is a possibility and should be discussed with the parents and patient.
Metacarpophalangeal Joint Fractures
Pathophysiology
Metacarpal and phalangeal fractures are the most common upper extremity fracture (39). According to Diao (40), the
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incidence of intraarticular metacarpal head and base fractures is 4% to 5% of all metacarpal injuries.
FIGURE 7. The three types of intraarticular fractures of the base of the proximal phalanx. A: Collateral ligament avulsion fracture. B: Compression fracture. C: Vertical shaft fracture.
Intraarticular fractures of the MCP joint involve either the metacarpal head or base of the proximal phalanx by definition. According to Jupiter and Belsky (27), intraarticular fractures of the base of the proximal phalanx are one of three types: avulsion fractures of the collateral ligaments, compression fractures, or vertical shaft fractures that extend into the joint (Fig. 7). Avulsion fractures are most commonly seen at the thumb ulnar collateral ligament, followed by the index and small finger. The mechanism of injury is a lateral displacement often incurred during athletic activities. Compression fractures are generally from an axial load. Vertical fractures can result from axial loads, torsion, or direct trauma. Whatever the mechanism or type of fracture, the goals are the same: restoration of a congruent joint surface and stabilization of the fracture.
Intraarticular fractures involving the metacarpal head are uncommon, as stated previously. In a retrospective multicenter study by McElfresh and Dobyns (41), 103 metacarpal head fractures were reported. They found that the second metacarpal was most commonly injured, followed by the fifth. The least commonly injured was the thumb. They classified these injuries into 10 groups based on anatomic involvement. The groups were epiphyseal injuries, collateral ligament avulsion fractures, osteochondral fractures, comminuted fractures, metacarpal neck fractures with intraarticular extension, loss of substance fractures (usually open), occult fractures leading to avascular necrosis, and three types of two-part fractures (coronal, transverse, and sagittal). As with base of proximal phalanx fractures, the goals are restoring joint congruency and stable fixation of the fracture to allow early motion. The difficulty comes in determining how much displacement is acceptable and which fractures are unstable. As best stated by Swanson (42), “hand fractures can be complicated by deformity from no treatment, stiffness from overtreatment, and both deformity and stiffness from poor treatment.” There are no prospective studies that determine how much displacement is acceptable before function is compromised. What is generally accepted in the literature is less than 1 mm of displacement of the articular surface (43,44).
Evaluation
The evaluation begins with a careful history and physical examination. On examination, there may be very little evidence other than pain that indicates the type of injury. There may be rotational or angular deformity of the digit as well. Careful radiographic examination is essential in making the appropriate diagnosis and planning treatment. Standard anteroposterior, lateral, and oblique radiographs of the hand should be obtained. Two other special views can be helpful in evaluating the MCP joint. The Brewerton view is obtained by flexing the MCP joints 65 degrees with the dorsum of the fingers lying flat on the x-ray plate and the tube angled 15 degrees in an ulnar-to-radial direction (44). This particular view can be helpful in showing fractures that may not be readily visible on the other views. A skyline view may be helpful in visualizing the articular surface of the metacarpal head after a clenched-fist injury (45). This is obtained by having the patient make a fist, and the beam is then directed parallel to the dorsal shaft of the proximal phalanx toward the metacarpal head.
For fractures that are difficult to assess on plain radiograph, a tomographic image, such as a computed tomography scan, may give more information about displacement and number of fracture fragments. With proximal phalanx avulsion fractures, stress views may help determine stability of the fracture fragment.
Nonoperative Treatment
Intraarticular base of proximal phalanx fractures and intraarticular metacarpal head fractures that are nondisplaced and stable can be treated by splinting. If there is more than 1 mm of displacement, open reduction should be undertaken in most circumstances. Some also believe that if more than 25% of the joint surface is involved, it should be stabilized with internal fixation (44). Once it has been established that the injury is stable, the fracture should be immobilized in a splint in the safe position (Fig. 8). The MCP joints should be flexed 60 to 70 degrees to prevent shortening of the collateral ligaments and subsequent loss of MCP joint flexion. The interphalangeal joints should be extended. Radiographs should be repeated on a weekly basis to ensure that the fracture remains nondisplaced. Immobilization should be continued for 3 to 4
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weeks. This is followed by use of a protective splint for activities that is removed for range-of-motion exercises and light daily activities for an additional 2 weeks. Hand therapy commences at 3 to 4 weeks postinjury. Proximal phalanx avulsion fractures can be treated by buddy taping to the adjacent finger for 4 weeks. They should be tested for ligament stability once bony healing has occurred. It may be prudent to continue to protect the digit with buddy taping for athletic activity for an additional 2 to 4 weeks.
FIGURE 8. Safe position for immobilizing the hand. Metacarpophalangeal (MP) joints flexed 60 to 70 degrees, interphalangeal (IP) joints extended.
Operative Treatment
Intraarticular fractures of the metacarpal head or base of the proximal phalanx that are displaced require operative fixation. Fractures of the base of the proximal phalanx are discussed first.
These fractures can be approached through either a dorsal or volar incision depending on fracture location and surgeon preference. For proximal phalanx avulsion fractures, there is support in the literature for either approach. Jupiter and Sheppard (46) have advocated a dorsal approach between the extensor tendon and the sagittal band. They then hold the fragment reduced with a tension band technique using a 26- or 28-gauge monofilament stainless steel wire. A hole is drilled dorsal to palmar with a 0.035-in. Kirschner wire in the intact proximal phalanx 1 cm distal to the avulsion fracture. The wire is then passed around the fracture fragment and ligament and then through the drill hole and tightened in a figure-of-eight fashion (Fig. 9). If there is more of a vertical shear component to the avulsion fracture, a Kirschner wire and/or interfragmentary screw should be added as well.
Alternatively, Kuhn et al. (47) described a volar approach through the A1 pulley with fixation by two Kirschner wires (Fig. 10). They cite the volar location of the fracture fragment and difficulty reaching the fragment through a dorsal approach as reasons for recommending this approach. With very comminuted or small avulsion fractures, fixation of the ligament and small fragment with minisuture anchors is a good alternative to direct bony fixation.
Vertical shaft fractures can sometimes be reduced closed and fixed with percutaneous Kirschner wires. This is preferable to open reduction if a good reduction can be achieved. If closed reduction cannot be obtained, open reduction and
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fixation with interfragmentary screws is the method of choice.
FIGURE 9. Technique for tension band wiring of proximal phalanx avulsion fractures as described by Jupiter and Sheppard. A: Avulsion fracture of a metacarpophalangeal joint, with the collateral ligament dissociated from the proximal phalanx via the fracture. B: Through a dorsal approach, a drill hole is established in the proximal phalanx just distal to the fracture line, through which a hypodermic needle is advanced. C: A small surgical wire is passed through the drill channel in the proximal phalanx using the hypodermic needle, crossed as a figure-of-eight, and passed through the collateral ligament at its attachment to the avulsion fragment. D: With the avulsion fragment reduced to the proximal phalanx, the tension band wire is tightened, and the free end is buried in an adjacent drill hole in the proximal phalanx.
FIGURE 10. Volar approach to proximal phalanx avulsion fracture through the A1 pulley.
Compression fractures do not reduce by closed manipulation. Open reduction and careful disimpaction of the fragment are necessary. There is then a void of bone distal to the joint surface that is now in a reduced position. This void should be filled with cancellous bone graft to support the joint surface and keep it from settling back into its original position before reduction. Either allograft or autograft can be appropriate depending on the circumstances. Fixation can be challenging, as it is not desirable to overcompress the articular surface, which can happen with placement of interfragmentary screws (Fig. 11). It may be necessary to use a combination of Kirschner wires and screws or even a minicondylar plate if there is not too much comminution.
In cases of very comminuted fractures, external fixation after closed or open reduction may be the best option. It is even possible to use small hinged fixators (designed for proximal interphalangeal joints) (Smith & Nephew, Memphis, TN) on the border digits for distraction and early range of motion of MCP joint fractures.
Metacarpal head fractures that are displaced or unstable require open reduction and fixation to restore anatomic alignment and allow early mobility. Treatment of these fractures is individualized depending on the fracture pattern. Soft tissue attached to the fragments should be left in place to decrease the risk of devascularization. Large fracture fragments can be fixed with screws. Both Herbert screws and Mini-Acutrak (Acumed, Hillsboro, OR) screws can be sunk beneath the cartilage surfaces to allow stable fixation of larger osteochondral fragments. Fixation with Kirschner wires should be a last resort, as they do not usually provide stable enough fixation for early mobility. Kumar and Satku (48) have described a technique whereby the joint space is described as a “potential” space and by reducing the osteochondral fragment and repairing the capsular rent the fragment is “trapped” and held in place without the need for fixation. Very comminuted fractures present a challenge. Two operative treatment alternatives include external fixation and traction splinting.
FIGURE 11. Technique of bone grafting base of proximal phalanx compression fractures to avoid displacement with screw placement.
Open fractures should be thoroughly irrigated. A clean surgical bed and adequate soft tissue coverage must be available to allow internal fixation. It may be necessary to delay definitive fixation or use alternative methods such as an external fixator.
Authors’ Preferred Treatment
Nondisplaced fractures of the metacarpophalangeal joint are treated in a splint for 3 to 4 weeks, followed by hand therapy and range of motion. A removable splint is used for an additional 2 to 3 weeks to protect the injury from more strenuous activity but allow range of motion and light daily activities without the splint. Buddy taping is the preferred method of treatment for avulsion fractures of the base of the proximal phalanx.
Displaced intraarticular fractures of the base of the proximal phalanx are generally approached through a dorsal
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incision. Preoperative computed tomography scan is not routine but is obtained if there is difficulty determining fracture pattern, displacement, or amount of comminution on routine radiographs. A curvilinear incision is made over the MCP joint. The interval is between the extensor tendon and the sagittal band, which is tagged for later repair. The joint capsule is then opened, and the fracture is identified and reduced with as little soft tissue stripping as possible. The next step depends on the size of the fracture fragment. If the fracture fragment is large enough to be fixed with any type of screw, this is the first preference. For smaller pieces, the previously described tension band technique with 26- or 28-gauge wire is used. In the case of very small or comminuted fragments, one or two minisuture anchors are used to secure the ligament and any small bit of bone. Direct visualization of the joint surface and intraoperative fluoroscopy are used to confirm the reduction. The patient is placed in a splint for a week to allow the incision to heal. A removable protective splint is then fabricated. The splint is removed for range-of-motion exercises and bathing. This splint is used for an additional 3 to 4 weeks until healing has occurred. The patient is protected with buddy splinting for athletic activity for an additional 4 weeks.
Vertical fractures that can be reduced by closed manipulation are then pinned percutaneously. If open reduction is required, interfragmentary screws are used to hold the reduction. The approach is generally dorsal, but if it is a border digit with a sagittal split, a midaxial incision may give better exposure. One caution is to make sure that the most distal screw is not too close to the apex of the fracture, as it can cause a longitudinal split in the fragment, making fixation much more difficult.
The key to fixing compression fractures is restoring the joint surface to as close to normal as possible and supporting the reduction with adequate bone graft. If screw fixation is possible, this is desirable to allow early motion. Care must be taken to not overcompress the joint surface. Often screw fixation is not possible. Under these circumstances, external fixation works quite well to support the joint surface for 2 to 3 weeks until enough healing has occurred to allow protected motion. With border digits, a hinged fixator is preferable to allow early motion. The most important point is to make sure that the axis of rotation is centered on the joint.
The authors have used the hinged fixator (Smith & Nephew) for intraarticular MCP joint fractures with good success. This can be done only on the small finger, index finger, or thumb. All three patients regained full range of motion and maintained anatomic alignment of the joint surface. In one case, a compression fracture was present that required elevation of the depressed joint surface and bone grafting (Fig. 12). The fixator allowed stable, early range of motion for a good end result.
Metacarpal head fractures are approached in much the same way. Most of the time, a dorsal approach provides good visualization and access for fixation. However, on occasion, if there is a volar proximal fragment, it may be easier to approach this through a volar Bruner incision with opening of the A1 pulley and volar plate for exposure. This provides safe, direct access to the volar fragment. It is the authors’ preference to use Mini-Acutrak or Herbert screws for fixation, as there is no head on the screw and it therefore can be buried beneath the cartilage surface (Fig. 13). Care must be taken to put in a shorter screw than what is drilled so that in placing the screw the fracture is not distracted. A derotation wire should be placed before putting in the screw so the fracture does not malreduce as the screw is advanced.
FIGURE 12. Use of the hinged fixator (Smith & Nephew) for fixation of a compression fracture of the base of the proximal phalanx that required a bone graft buttress.
Complications
The most common complication after intraarticular fracture is joint stiffness. Prevention is much easier than treatment. However, in some instances, early range of motion is not possible, and this contributes to the development of joint stiffness. If therapy has been maximized and the joint is congruent, then tenolysis, capsulectomy, and release of the collateral ligaments may be necessary to improve motion.
Avascular necrosis of the metacarpal head and growth arrest in the skeletally immature can also be seen after these types of fractures.
CARPOMETACARPAL JOINT
Surgical Anatomy and Biomechanics
The carpometacarpal (CMC) joints of the fingers form a stable transverse arch and allow relatively little motion. The
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index and long CMC joints are the least mobile because of the tight congruent bone articulations and abundant soft tissue constraints. In particular, the base of the long meta-carpal serves as the “keystone” of the distal transverse arch, as it articulates with the capitate and adjacent metacarpals and is supported by the sturdy volar and dorsal ligaments. Only minimal flexion and extension (less than 1- to 3-degree arc) are available.
FIGURE 13. Use of a Herbert screw for fixation of a displaced metacarpal head fracture. Posterior radiographs of a displaced intraarticular metacarpal head fracture before (A) and after (B) reduction and fixation with a Herbert screw.
The ring and small CMC joints, on the other hand, provide more motion. Multiplanar motion is available, including flexion, extension, abduction, adduction, and circumduction. Again, mobility is determined by the shape and congruency of the articulating bones as well as by the soft tissue supports. The modified saddle-shaped articulation of the distal hamate and fewer ligamentous constraints allow up to a 10- to 15-degree flexion–extension arc by the ring metacarpal and 15 to 30 degrees of flexion–extension by the small metacarpal, with rotation and abduction–adduction in this joint as well (49,50).
FIGURE 14. Stabilizing structures of the thumb carpometacarpal joint.
Stability is imparted by the dorsal capsular ligaments, volar ligaments, interosseous ligaments, and, more distally, the deep transverse intermetacarpal ligaments. The extensor carpi ulnaris (which inserts on the dorsoulnar portion), flexor carpi ulnaris (via the pisometacarpal ligament), and hypothenar muscles act as dynamic stabilizing elements of the small CMC joint. The index and long CMC joints are served similarly by the flexor/extensor carpi radialis longus tendons (which insert into the index metacarpal base) and extensor carpi radialis brevis (which inserts into the long metacarpal base), respectively.
The CMC joint of the thumb is a biconcave saddle joint, which allows multiplanar motion, including flexion–extension, abduction–adduction, and pronation–supination. Stability is provided not by the bony architecture but mostly by the surrounding ligaments: volar beak, dorsal oblique, intermetacarpal, and dorsoradial (Fig. 14). The volar beak ligament (also known as the volar oblique, anterior oblique, and palmar oblique ligament) is believed to be the major stabilizing ligament. In preventing dorsal subluxation of the CMC joint, the volar beak ligament also plays an important role in key functional activities such as pinch.
Carpometacarpal Joint Dislocations
Pathophysiology
Dislocations of the CMC joint are uncommon injuries and are present in less than 1% of hand injuries (51). Again, the border digits (index and small fingers) are most vulnerable to injury. In isolated CMC dislocations, the small finger is
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most frequently involved. In multiple dislocations, all combinations can occur but again include the small finger in the majority of cases. Dislocations of the thumb CMC joint are rare and less common than injuries to the fingers. Dislocations are commonly in the dorsal direction, although volar dislocations also occur. Of note, the inherent stability of the CMC joints and the surrounding ligamentous supports make pure dislocations of the CMC joint much less common than CMC fracture dislocations.
Isolated dorsal dislocations usually occur from an axial compressive force to the dorsum of the metacarpal head, resulting in an axial compressive and flexion moment to the metacarpal. As the head toggles volarly, the base is driven out dorsally, leading to disruption of the abundant stabilizing ligaments. Dorsal dislocations of the thumb occur by a similar mechanism—i.e., axial compressive force to the flexed metacarpal head. Strauch et al. demonstrated in a cadaveric study that the dorsoradial ligament ruptures and the volar beak ligament detaches from the base of the thumb metacarpal in complete dislocations of the thumb CMC (52). Multiple dislocations usually require a greater amount of force and are associated with high-energy trauma, often motorcycle accidents.
Evaluation
The history is usually that of a high-energy trauma—e.g., from motor vehicle and motorcycle accidents and falls. Isolated dislocations can also occur from a direct blow to the dorsum or palm of the hand or from hitting someone or something with a clenched fist. The diagnosis of CMC dislocations requires a high index of suspicion. The high-energy nature of the injury usually results in trauma to other organ systems, which can lead to delays in diagnosis. In addition, extensive soft tissue damage and swelling can obscure subtle deformities. Tenderness and swelling at the CMC joints, however, should alert the clinician. Physical findings also may include prominence of the metacarpal head and/or base, deviation, and malrotation of the involved digits. Meticulous neurovascular examination is necessary given the close proximity of important nerves and vessels.
Radiographs once again are confirmatory. Initial radiographs should include anteroposterior, lateral, and oblique views. The anteroposterior radiograph demonstrates loss of the normal parallel joint lines and overlapping of the base of the dislocated metacarpals on the carpals. Careful inspection of the lateral radiograph should demonstrate the direction of dislocation. Given the superimposition of the adjacent CMC joints on the lateral view, the oblique radiograph may assist in determining the direction of dislocation. Additional 30-degree oblique radiographs with the forearm both supinated and pronated allow closer inspection of the index and small CMC joints, respectively. A true lateral radiograph of the thumb CMC joint is mandatory for complete evaluation of the thumb. The palmar surface of the hand is placed flat on the film plate, the hand and wrist are pronated 20 degrees, and the x-ray beam is angled 15 degrees distally (Fig. 15) (53). If a diagnosis of dislocation is still in doubt, fluoroscopy or fluoroscan imaging may also be extremely useful to view the involved CMC joint in multiple planes. Fracture dislocations of the CMC joint are more common; therefore, a close look is crucial to rule out concomitant fractures of the meta-carpal and carpal bones.
FIGURE 15. Technique for obtaining a true lateral radiograph of the thumb carpometacarpal joint.
Nonoperative Treatment
For acute dislocations of the CMC joint, an attempt at closed reduction should be made. Again, atraumatic reduction is key. After adequate anesthesia is obtained, the first step in reducing a dorsal dislocation is longitudinal distraction. Next, accentuate the deformity by hyperextending the CMC joint. Finally, pressure is applied to the dorsum of the metacarpal base in a volar direction while the metacarpal is gradually flexed. If the reduction is anatomic and stable, these injuries can be treated with cast immobilization with the wrist in slight extension, the metacarpal joints flexed, and the interphalangeal joints extended.
Dislocations of the CMC joint, however, are frequently unstable even after relocation and cast immobilization, and so surgical intervention is often needed. Closed reduction can also fail if soft tissue such as a capsular flap is interposed. Massive soft tissue edema and delays in diagnosis may also render closed reduction impossible. Open reduction is then necessary.
Dislocations of the thumb CMC joint may at times be amenable to nonoperative treatment. Watt and Hooper observed that for dislocations that were reduced acutely and were found to be stable immediately after reduction, cast immobilization was sufficient to maintain reduction and
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prevent long-term disability in isolated dislocations of the thumb CMC joint (54). Uchida et al. reported similar success in a case report of two patients who were treated with closed reduction and cast immobilization (55). At 2-year follow-up, patients were asymptomatic, with normal range of motion and excellent grip power. There was no radiographic evidence of posttraumatic arthritis. During cast application, the CMC joint should be maintained in a position of extension and pronation to reapproximate the torn edges of the volar beak ligament.
The reduction maneuver for volar CMC dislocations is as follows: The first step again is longitudinal distraction. With the CMC joint hyperflexed, apply pressure to the volar base of the dislocated metacarpal in a dorsal direction. The metacarpal is gradually extended as the dorsal force is applied. Failure to reduce the dislocation necessitates an open reduction.
For multiple dislocations, an initial attempt at closed reduction is reasonable. However, significant soft tissue swelling makes relocation of the CMC joints difficult. The associated soft tissue injuries also predispose to subluxation and long-term instability. Surgical intervention is usually necessary.
Surgical Management
Because pure dislocations of the CMC joint are so infrequent, optimal treatment remains controversial. Treatment recommendations in the literature are based largely on case reports and small series and vary from closed reduction with cast immobilization, closed reduction with percutaneous fixation, to open reduction with internal fixation.
An anatomic and stable reduction is the goal. Residual subluxation leads to pain, muscle imbalance, a weakened grip, and, eventually, traumatic arthritis (6,56,57,58,59,60,61 and 62). Again, as mentioned previously, cast immobilization is usually inadequate to maintain reduction after closed reduction. Percutaneous Kirschner wire fixation is commonly necessary (63). Multiple alternative orientations for pin placement have been endorsed, including simple oblique fixation of the metacarpal to the corresponding carpal bone (64), longitudinal intramedullary fixation (65), and transverse fixation to the adjacent metacarpal (44). Because frequent and accurate radiographic monitoring necessitates frequent cast changes and thereby increases the potential risk of subluxation and redislocation, many authors have recommended avoiding cast immobilization and have supported the use of percutaneous fixation.
Open reduction is indicated if attempts at closed reduction fail or if there is difficulty in determining whether the joint is reduced by intraoperative radiographs, making direct visualization necessary. Delays in diagnosis, marked soft tissue swelling, and open injuries often necessitate an open reduction. Outcome studies investigating the need for open reduction in pure dislocations involving multiple CMC joints and the ring and little CMC joints are lacking. However, based on studies looking at fracture dislocations of the CMC joints, many authors recommend an open reduction and internal fixation for multiple CMC dislocations (64). Often cited reasons in the literature include the need for direct visualization to obtain absolute anatomic reduction with multiply involved joints, the avoidance of percutaneous pins in already compromised soft tissue to minimize the risk of infection, and the prevention of irritation to adjacent extensor tendons to meet the heightened need to mobilize early (64).
Exposure of the CMC joints is usually through a dorsal approach. A longitudinal, zigzag, or L-shaped incision is made over the CMC joint based on the surgeon’s preference. Care is taken to avoid injury to the dorsal sensory nerve branches and veins. The extensor tendons are retracted to visualize the injured joint. The joint can then be inspected for injury to the articular surfaces, interposed capsular soft tissue, and loose bony fragments. Appropriate débridement followed by reduction is performed. Fixation is usually with Kirschner wires. Ligament repair is usually unnecessary, although capsular closure can be performed.
Controversy also exists over the optimal treatment of thumb CMC dislocations. An anatomic and stable reduction is essential to prevent pain, decreased thumb strength, and the possibility of posttraumatic degenerative changes in the joint. Percutaneous fixation with Kirschner wires may at times be necessary to maintain the reduction. Open reduction is necessary if closed reduction fails. Some have recommended open reduction and pin fixation with repair of the dorsoradial ligament (62). The dorsoradial ligament is usually short and poorly defined, however, making direct repair of the dorsoradial ligament difficult. In these cases and sometimes even as the initial approach, the anterior oblique ligament is surgically reconstructed at the time of open reduction (6,62). A variety of reconstructions are supported by the literature; however, most favor the technique of Eaton and Littler (66,67). The thumb CMC joint is exposed through a modified Wagner incision (Fig. 16). Meticulous attention is necessary to avoid injury to the palmar cutaneous branch of the median nerve, the superficial radial artery, and branches of the dorsal sensory branch of the radial nerve.
Authors’ Preferred Method of Treatment
It is the authors’ experience that CMC joint dislocations are inherently unstable. For this reason, the preference of the authors is closed reduction and percutaneous Kirschner wire fixation. If a closed reduction can be achieved, the joint should be pinned to ensure healing in a reduced position. The dislocated metacarpal is pinned to the adjacent metacarpal as well as to the distal carpal row. If a closed reduction cannot be obtained or there is any question on the radiographs whether the joint is reduced, an open reduction
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should be performed. A dorsal L-shaped approach to the CMC joint is used. The joint is reduced under direct visualization and pinned in that reduced position.
FIGURE 16. Wagner approach to the thumb carpometacarpal joint.
The pins are cut and left under the skin for later removal. The pins are kept in place for 6 weeks. Motion of the digits is allowed at 3 to 4 weeks postoperatively. Once the pins are removed, most patients require some hand therapy to regain range of motion and strength.
Complications
Joint stiffness and pain are potential late sequelae of dislocations of the CMC joint. The main factor in joint stiffness is usually the soft tissue trauma sustained at the time of dislocation; however, inadequate rehabilitation and a delay in treatment can be contributory as well. Treatment consists of therapy for range of motion. Surgical intervention in the form of joint contracture release or tenolysis may also be necessary.
Recurrent dislocation or subluxation may also occur. If painful, a late open reduction may be reasonable. Reconstruction of the volar beak ligament has been advocated for the thumb nonarthritic CMC joint (62). In most cases, however, arthrodesis or interposition arthroplasty may be indicated depending on the joint involved and the preference of the surgeon.
The articular surfaces may be injured at the time of dislocation. As a result, pain and weakness secondary to posttraumatic arthritis are not uncommon. Treatment options include arthrodesis or interposition arthroplasty. Injury of the sensory nerves and extensor tendons may also occur during open reduction or pin placement. These are more easily treated by careful attention to detail during the initial operation than reconstruction at a later date.
Carpometacarpal Joint Fractures
Pathophysiology
By definition, intraarticular fractures of the CMC joint involve either the base of the metacarpal or distal carpal bone. The more mobile ring and small fingers are most frequently involved, with the small finger involved in up to 50% of cases (24). The thumb metacarpal is commonly involved as well, accounting for 25% of all metacarpal fractures (68). Intraarticular fractures involving the distal carpal bones are rare, with the literature limited to isolated case reports. Multiple joints may be involved, and all combinations have been reported. Fractures are often associated with subluxation or dislocation. If present, the direction of dislocation as in pure dislocations is usually dorsal.
According to Jupiter and Belsky, intraarticular fractures of the thumb metacarpal base are one of three types: two-part (Bennett’s), three-part (Rolando’s), and comminuted with impaction (Fig. 17) (27). Intraarticular fractures of the distal carpal bones can be subdivided into avulsion fractures, depression fractures (usually of the dorsal articular rim), and coronal split fractures.
The mechanism of injury is usually an axial compressive load transmitted along the metacarpal shaft, although direct trauma is also possible. For fractures involving the small CMC joint, the extensor carpi ulnaris, which inserts on the base of the fifth metacarpal, acts as a deforming force (Fig. 18). The deep motor branch of the ulnar nerve passes adjacent to the hook of the hamate and can be traumatized with these fractures.
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FIGURE 17. Intraarticular fractures of the base of the first meta-carpal of the thumb. A: Bennett’s. B: Rolando’s Y. B’: Rolando’s T. C: Comminuted.
FIGURE 18. A: Diagram illustrating the displacement caused by the pull of the extensor carpi ulnaris (ECU) tendon. B: Radiograph depicting the displacement (arrow).
Intraarticular fractures of the thumb CMC joint occur by a similar mechanism—an axially directed force through the partially flexed metacarpal shaft. In the two-part (Bennett’s) fracture, the volar-ulnar fragment of the thumb metacarpal base is held in anatomic position by the volar beak ligament. The remainder of the thumb metacarpal subluxates radially, proximally, and dorsally secondary to the pull of the abductor pollicis longus and adductor pollicis (Fig. 19). In the three-part fracture described by Rolando (69), the volar beak ligament maintains the volar fragment in anatomic position. The dorsal fragment is displaced by the abductor pollicis longus; the shaft is displaced by the pull of the extensor pollicis longus and adductor pollicis. The three-part fracture pattern, however, can be quite variable.
Evaluation
The history, physical examination, and radiographic evaluation are essentially the same as with CMC dislocations. Plain or computed tomography may also be useful to better delineate fractures and guide treatment planning.
Nonoperative Treatment
Treatment planning for fractures and fracture dislocations of the CMC joints of the fingers has caused much debate. The literature is sparse, and treatment recommendations in general are supported by small series, clinical impressions, and insufficient data. On the other hand, the literature for fractures and fracture dislocations of the thumb CMC joint is abundant. Nevertheless, controversy over the optimal treatment still exists.
In 1974, Petrie and Lamb (70) reported on 14 CMC fracture dislocations of the small finger metacarpal base that were treated with unrestricted mobilization. After 41/2
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years, follow-up radiographs consistently demonstrated shortening of the metacarpal, widening of the base, and joint line step-off. Despite this, only one patient reported significant pain, with eight being pain-free and five with minimal pain. The authors concluded that anatomic reduction was not necessary.
FIGURE 19. Mechanism for displacement and instability of Bennett’s fractures of the thumb.
Similarly, previous literature has supported the use of closed reduction and cast immobilization in the treatment of fractures of the thumb metacarpal base (71,72 and 73). Short-term results from these studies were satisfactory even with malunion of these fractures.
Further studies on fracture dislocations of the CMC joint, however, have demonstrated significant pain, loss of grip strength, and eventually traumatic arthritis secondary to malunion and also instability (6,56,57,58,59,60,61 and 62). The literature on two-part (Bennett’s) fractures of the thumb metacarpal base has demonstrated similar findings. Livesley (74) noted persistent subluxation at the CMC joint and symptomatic arthritis in 12 of 17 patients followed an average of 26 years after nonoperative treatment of a Bennett’s fracture. According to studies by Kjaer-Petersen et al., Timmenga et al., Oosterbos and de Boer, Thurston and Dempsey, and Gedda and Moberg, a poor reduction (usually defined by displacement of more than 1 mm) correlates to pain, a poor functional result, and a heightened risk of posttraumatic arthritis (75,76,77,78 and 79). A biomechanical study of cadaver thumb CMC joints demonstrated increased contact pressures in a simulated malunion (2-mm step-off) of a Bennett’s fracture (80). Given forces up to 120 kg across the CMC joint during pinch and grasp (81), it is not difficult to see how these abnormal contact forces can eventually lead to degenerative changes in the joint. The literature on three-part (Rolando’s) and comminuted fractures of the thumb metacarpal base is unclear. Anatomic reduction especially of the articular surface in these fractures may or may not prevent the onset of posttraumatic arthritis and late disability.
The goals of treatment are a stable and anatomic reduction. Less than 1 mm of articular step-off or gap may be tolerated. Nondisplaced intraarticular fractures of the finger CMC joints without dislocations, in particular, may successfully be treated with cast immobilization. The wrist and fingers are immobilized in the safe position with the wrist slightly extended, metacarpophalangeal joints flexed to 60 to 70 degrees, and the interphalangeal joints extended. In injuries to the thumb CMC joint, the joint should be maintained in a position of extension and pronation, with mild pressure over the dorsoradial aspect of the metacarpal base. However, thumb CMC fractures are generally unstable and require operative fixation.
Surgical Management
Although an attempt at closed reduction and cast immobilization is reasonable, the majority of fractures and fracture dislocations of the finger CMC joints require further surgical intervention. Fractures that require reduction or have concomitant dislocations are inherently unstable, particularly those of the small finger CMC joint, because of the deforming forces of the extensor and flexor carpi ulnaris. Therefore, in cases of congruent yet unstable reductions, percutaneous fixation with Kirschner wires may be necessary (63). Options for pin placement configuration include oblique fixation of the metacarpal to the adjacent carpal bone (64), longitudinal intramedullary fixation (65), and transverse fixation to the adjacent metacarpal (44).
Closed reduction can fail because of many other reasons as well, including soft tissue or bony fragment interposition, soft tissue edema, and delays in diagnosis. Whatever the reason, if closed reduction is unsuccessful, open reduction is necessary. Many authors also recommend open reduction for multiple CMC fractures (64) as well as for ring and small finger CMC fractures and fracture dislocations (Fig. 20) (51,65,82). The dorsal approach as previously described is used to expose the site of injury. Internal fixation options vary from percutaneous fixation with Kirschner wires to the use of mini plates and screws and interfragmentary screws, including the Herbert and Mini-Acutrak screws.
A retrospective review of 13 patients with multiple CMC fracture dislocations by Garcia-Elias et al. revealed excellent functional results with no complications for the eight patients who underwent open reduction and internal fixation acutely (83). Lawlis and Gunther also reported favorable results after open reduction and internal fixation for 20 patients with fracture dislocations of the CMC joints (82). Out of the 15 patients who were treated acutely (within 2.5 weeks), 13 reported excellent results.
Additional indications for open reduction include open fracture dislocations that require wound débridement, comminuted fractures that may require cancellous bone grafting, and compression fractures that may require disimpaction. For open injuries, a thorough irrigation and débridement of the surgical bed should be performed, especially if internal fixation is entertained. The degree of comminution may make anatomic reduction impossible, so cancellous bone grafting may be necessary. In severely comminuted fractures, external fixation after closed or open reduction may instead be indicated. Compression fractures of the metacarpal base or distal carpal bone usually benefits from open disimpaction, cancellous bone grafting, and internal fixation.
Based on the success of arthrodesis in chronic unstable fracture dislocations of the CMC joint, especially the index and long fingers, some authors have recommended arthrodesis as a primary option for acute cases (84). Of five patients who underwent primary arthrodesis for acute, unstable index and long CMC fracture dislocations, Hanel reported excellent results in four patients and a good result in one. Because the index and long CMC joints are so rigid and immobile inherently, Hanel rationalized that fusion of these joints into a stable, fixed unit might be an appropriate option.
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FIGURE 20. Fracture dislocation of fourth and fifth carpometacarpal joints. A: Anteroposterior radiograph. Arrow indicates fracture dislocation. B: Lateral radiograph. Arrow indicates fracture dislocation. C,D: Postreduction anteroposterior and lateral radiographs.
Surgical intervention is usually necessary for thumb CMC fractures and fracture dislocations. Even when closed reduction is attainable, cast immobilization frequently fails, and further fixation is indicated. Two-part (Bennett’s) fractures can be treated with percutaneous Kirschner wire fixation (85,86), screw fixation, or oblique traction with a Kirschner wire and casting (87,88). Often used pin orientations include a transverse intermetacarpal pin from the radial side of the thumb metacarpal shaft to the index metacarpal and an oblique pin from the distal radial portion of the thumb metacarpal across the CMC joint into the trapezium. It is usually unnecessary to pin the Bennett’s fragment, the volar-ulnar aspect of the metacarpal base, which remains in anatomic position (Fig. 21).
If closed reduction fails, open reduction with Kirschner wire fixation (79,89,90) or interfragmentary screws (90,91,92 and 93) is necessary. External fixation has also been endorsed for fractures with associated soft tissue injury (94).
The treatment for three-part (Rolando’s) and comminuted fractures is varied as well. Treatment recommendations in the literature include closed reduction; percutaneous Kirschner wire fixation for nondisplaced fractures (86); open reduction and internal fixation with Kirschner wires, interfragmentary screws, and mini plates for displaced fractures with large fragments (90,92); and external fixation for fractures with severe comminution or associated soft tissue injury (95).
Authors’ Preferred Method of Treatment
Nondisplaced fractures of the CMC joint not associated with a dislocation can be treated in a cast or splint. The
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fracture is immobilized for 4 weeks followed by range of motion of the digits and wrist. During the immobilization period, serial radiographs should be taken for 2 weeks to make sure that the fracture does not displace.
FIGURE 21. Technique for fixation of a Bennett’s fracture. Note that there is no pin in the volar-ulnar fragment.
Displaced fractures and fractures associated with dislocations require reduction and fixation. If the reduction can be obtained by closed methods and easily confirmed by radiograph that the joint and fracture are reduced, closed reduction and pinning are acceptable. If a closed reduction cannot be obtained or confirmed by radiographs, the joint is opened through a dorsal L-shaped incision, and the fracture and joint are reduced under direct visualization and pinned. If the fracture fragments are large enough, interfragmentary screws are used. In the case of very comminuted fractures without dislocation, treatment consists of splinting or casting followed by early range of motion. If the joint becomes painful, an arthrodesis or interposition arthroplasty can be performed at a later date.
Bennett’s fractures that are easily reduced closed are pinned with two 0.045-in. Kirschner wires. Because of the previously mentioned dynamic deforming forces, even nondisplaced Bennett’s fractures should be pinned to ensure maintained reduction while the fracture heals. One pin is placed distal to the fracture from the radial border of the first metacarpal through the second metacarpal shaft. The second wire is placed from the first metacarpal across the CMC joint into the trapezium. If there is any difficulty confirming that the joint surface is reduced, the fracture is opened through a Wagner incision. The fragments are fixed with a Mini-Acutrak screw or other appropriate 2.7-mm or 2.0-mm screw depending on fragment size. The advantage to open reduction and fixation is direct visualization of the joint surface and the ability to start immediate range of motion if the fixation is rigid. Rolando’s fractures with three large fragments are amenable to mini condylar plate fixation. The more comminuted the fracture, the less successful open reduction and internal fixation will be. The goal is then indirect reduction of the joint as best as possible with either external fixation or Kirschner wire fixation of the first meta-carpal to the second metacarpal. It is recommended that, at a minimum, the preoperative radiographs be taken while distracting the CMC joint. This allows better visualization of the number of fracture fragments. One should plan to have more than one type of fixation available (mini plates and external fixation) in approaching comminuted fractures.
If rigid internal fixation is obtained, the patient begins range of motion 1 week postoperatively after the incision has healed. The fracture is protected in a thumb spica splint except for bathing and for range-of-motion exercises three times a day. Splinting is discontinued between 4 and 6 weeks postoperatively. In closed pinnings, the thumb is placed in a thumb spica cast for 4 to 6 weeks, followed by pin removal and range-of-motion exercises.
Complications
As in dislocations of the CMC joint, joint stiffness and recurrent dislocation or subluxation are also potential sequelae of fractures and fracture dislocations of the CMC joint. Diagnosis and management are similar.
Posttraumatic arthritis is a more common complication after fractures and fracture dislocations of the CMC joint. Controversy exists as to how frequently this becomes symptomatic and requires further intervention. Whether the insult arises from the initial damage to the joint at the time of injury or from malunion, pain and weakness are potential late findings. Local injection of lidocaine into the suspected joint may be a helpful diagnostic tool. Treatment varies from arthrodesis to interposition arthroplasty, again based on the joint involved and surgeon preference.
After fractures and fracture dislocations of the thumb CMC joint, malunion has been reported as the most frequent complication (96). For well-preserved articular surfaces, a closing-wedge osteotomy at the base of the thumb metacarpal has been recommended to reverse the instability resulting from a malunited two-part fracture (Bennett’s) of the thumb metacarpal base (97). An osteotomy through the old fracture site with reduction can also be performed. Arthrodesis and interposition arthroplasty are indicated as salvage procedures for long-standing instability and pain.
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