Metacarpal shaft fractures

INTRODUCTION — Metacarpal fractures are common. They account for up to 50 percent of all hand fractures [1-3]. Fractures of the metacarpal shaft are usually the result of direct or indirect trauma, but fatigue fractures can occur in athletes or as occupational injuries due to repetitive stress. The biomechanics, diagnosis, and treatment of stress fractures are presented separately. (See "Overview of stress fractures".)

This topic will review issues related to metacarpal shaft fractures. A general overview of metacarpal fractures and discussions of other common hand and wrist injuries are presented separately. (See "Overview of metacarpal fractures" and "Scaphoid fractures" and "Proximal phalanx fractures" and "Middle phalanx fractures" and "Distal phalanx fractures" and "Distal radius fractures in adults" and "Overview of carpal fractures" and "Evaluation of the adult with acute wrist pain".)

CLINICAL ANATOMY — The heads of the metacarpals are bulbous and "cam" shaped, thereby permitting adduction, abduction, flexion, extension and passive rotation of the fingers. The collateral ligaments join the metacarpal to the proximal phalanx and are taut in flexion, while having some laxity in extension (figure 1 and figure 2 and figure 3). The functional importance of this configuration is that the metacarpal phalangeal (MCP) joints should be immobilized in flexion to prevent shortening of the collateral ligaments and subsequent loss of motion.

FRACTURE PATTERNS AND MECHANISM OF INJURY — Metacarpal shaft fractures occur in three basic patterns: transverse, oblique, and comminuted.

●Transverse fractures are caused by a direct blow. These fractures are typically pulled into apex dorsal angulation by the forces of the interosseous muscles (figure 4 and figure 5 and figure 6) and extrinsic flexor tendons exerted on the metacarpal shaft.

●Oblique fractures are caused by torsional forces. These fractures usually do not angulate but instead tend to shorten and rotate, and are relatively unstable. As with any metacarpal fracture, rotational malalignment is not tolerated. However, simple shortening (up to 5 mm) with no associated angulation or rotation is acceptable. (See 'Indications for surgical referral' below.)

●Comminuted fractures are typically caused by trauma involving substantial impact, such as a crush injury. These fractures are often associated with significant soft tissue injury and require hand surgery or orthopedic consultation.

CLINICAL PRESENTATION AND EXAMINATION — Patients with metacarpal shaft fractures describe a history of recent hand trauma and complain of pain along the dorsum of the hand. They are typically unable or unwilling to flex the metacarpal phalangeal (MCP) joint. Metacarpal shaft fractures are more common on the ulnar side of the hand and occur most frequently in the metacarpal of the little finger [4,5]. Punching injuries often account for shaft fractures of the ring finger metacarpal shaft [6].

Examination reveals bony tenderness along the affected metacarpal and often a palpable deformity and dorsal swelling. Other specific findings associated with metacarpal shaft fractures are described immediately below. (See 'Assessment of hand alignment and function' below.)

The trauma that causes a metacarpal shaft fracture or the fractured bone itself can cause breaks in the skin, which predispose to infection. The skin in the area of the fracture should be carefully examined. Lacerations through the skin may be associated with tendon lacerations and any exposed tendon should be examined over its full range of motion. This may not be possible until pain is well controlled. A basic neurovascular examination of the hand, including capillary refill and sensory and motor function should be performed.

Assessment of hand alignment and function

Extensor apparatus — Metacarpal shaft fractures can impair finger extension or damage other structures involved in finger extension. Thus, the extensor apparatus should be evaluated. In an angulated metacarpal shaft fracture, efforts to extend the finger may result in hyperextension at the MCP joint with flexion at the proximal interphalangeal (PIP) joint (so-called "pseudo-clawing").

Angulation — Deformity secondary to apex dorsal angulation is frequently apparent with metacarpal shaft fractures either through observation or gentle palpation, but is appropriately assessed using a lateral radiograph. (See 'Diagnostic imaging' below.)

Rotational alignment — Rotational deformity often accompanies oblique metacarpal shaft fractures. Rotational alignment should be assessed with the MCP joint in flexion. The rotational alignment of the metacarpals can be assessed in two ways:

●In a semi-clenched fist (flexion to 90 degrees at the MCP and PIP joints), fingers in normal alignment point toward the scaphoid pole and lines drawn through the middle of each finger's long axis converge just past the wrist, although not necessarily to a single point (picture 1A-B).

●With the MCP joint flexed 90 degrees and the PIP and distal interphalangeal (DIP) joints in full extension, the plane of the fingernails should be aligned, and can be compared with the contralateral side (picture 2).

DIAGNOSTIC IMAGING

Plain radiographs — The standard three views of the hand (anteroposterior [AP], lateral, and oblique) are generally adequate for evaluating metacarpal shaft fractures using plain radiographs.

Angulation is determined using the lateral view by measuring the angle between the axes of the two fracture fragments (image 2C). Acceptable angulation for metacarpal shaft fractures is less than or equal to 10 degrees for the index and middle finger, 20 degrees for the ring finger, and 30 degrees for the little finger respectively [5,7]. Up to seven degrees of extensor lag and eight percent of grip strength are lost with every two mm of metacarpal shortening [4].

Less angulation is acceptable in metacarpal shaft fractures relative to metacarpal neck fractures because angulated shaft fractures tend to have greater associated deformity, more functional problems, and a higher risk of "pseudo-clawing." Fractures of the border metacarpals (index and little finger) are inherently less stable than fractures of the middle and ring finger metacarpals because they only have one adjacent metacarpal and transverse metacarpal ligament to provide stability.

Bone shortening is determined radiographically, typically by measuring the overlap of the distal and proximal fracture fragments on the lateral and AP radiographs. Oblique fractures are more prone to shorten and rotate (image 1). This is particularly true for long oblique fractures, particularly those where the fracture length is greater than two times the bone diameter. Transverse fractures (particularly isolated middle and ring finger metacarpal shaft fractures) are generally stable (image 2A-E and image 3 and image 4).

Bone callus from fracture healing may not appear until four to six weeks from the start of treatment. (See 'Follow-up care' below.)

Musculoskeletal ultrasound — Ultrasound is well suited for investigating fractures in linear areas of bone such as the diaphyseal and metaphyseal regions of the metacarpals.

Musculoskeletal ultrasound (MSK US) examination of the hand is best performed with the patient seated and the hand resting on an examination table. Examination of the dorsum is performed first, followed by the volar side. A high-frequency transducer of at least 10 mHz is typically used. A small footprint (hockey stick) linear probe (picture 3) makes examination of the hand and metacarpals easier. MSK US examination of the hand and metacarpals involves a standard two-position examination (longitudinal [ie, sagittal] (picture 4) and transverse views). Initially, the probe is placed on the dorsum of the hand at the distal metacarpophalangeal (MCP) joint and then moved proximally. Images are obtained in the longitudinal and transverse planes. This allows for evaluation of potential joint involvement of a metacarpal fracture. The cortex of each potentially injured metacarpal is examined carefully for any discontinuity in the hyperechoic surface consistent with a fracture (image 5). Cortical discontinuities as small as 1 mm can be identified with high-resolution transducers and may enable visualization of fractures that would be missed with standard radiographs [8]. Occasionally, hematoma, edema, or ligamentous disruption may be seen.

Studies of MSK US report sensitivities of 90 to 91 percent and specificities of 97 to 98 percent for hand fractures [9,10]. However, while ultrasound can be effective for diagnosing metacarpal fractures, plain radiographs may still be needed to determine angulation and rotation.

DIAGNOSIS — Fractures of the metacarpal shaft are diagnosed by plain radiograph. Clinicians should suspect such injuries in patients who have sustained direct or indirect trauma to the hand, and show signs of pain, swelling, and focal tenderness at the dorsum of the hand.

DIFFERENTIAL DIAGNOSIS — Diagnosis of a metatarsal shaft fracture is straightforward using plain radiographs. Thus, issues related to the differential diagnosis have to do primarily with other possible associated injuries sustained from the inciting trauma, including tendon lacerations, bone contusions, nerve injury, and other soft-tissue damage. The assessment of a possible tendon laceration is described above. (See 'Clinical presentation and examination' above.)

INDICATIONS FOR SURGICAL REFERRAL — Immediate surgical consultation is required for all open fractures and for all fractures with associated vascular compromise or nerve injury. In addition, early referral is needed for patients with a metacarpal fracture associated with a complete tendon laceration. It is best to discuss the case directly with the hand surgeon who will assume care to determine the timing for follow-up. (See "General principles of fracture management: Early and late complications".)

Metacarpal shaft fractures with malrotation, comminution, or shortening greater than 5 mm all warrant hand surgery consultation. If more than one metacarpal is fractured or if adequate reduction is not attained or maintained, orthopedic or hand surgery referral is indicated (picture 5). (See 'Closed reduction' below.)

Patients whose fractures involve between 2 to 5 mm of shortening may be managed on a case-by-case basis by physicians familiar with fracture management or they may be referred.

Acceptable angulation is ≤10 degrees in index and middle finger metacarpals, ≤20 degrees in ring finger metacarpals, and ≤30 degrees in little finger metacarpal shaft fractures. Long oblique fractures often cannot be reduced by closed means and may require surgical fixation. Early orthopedic referral in these cases is reasonable.

Athletes with metacarpal shaft fractures who desire a quick return to competition, particularly those involved in contact sports, should be referred for possible treatment with operative fixation.

For some displaced fractures without other complicating features, nonoperative management may lead to comparable functional outcomes. A randomized trial of displaced oblique or spiral metacarpal shaft fractures (n = 42) reported comparable or better results with conservative management compared with surgical fixation in the primary outcome (grip strength at one year) and in several secondary outcomes (eg, complications, duration of absence from work, and patient satisfaction) despite significantly worse bone shortening in the nonoperative group (5.3 mm versus 2.3 mm for surgery group) [11].

INITIAL TREATMENT — Before any attempts at reduction are made or the fracture is immobilized, any skin abrasions should be cleaned and lacerations thoroughly cleaned and irrigated. Aggressive decontamination to avoid potentially disastrous intraarticular infections is necessary if skin integrity is compromised. Prophylactic antibiotics appear to be beneficial with hand bites from humans. (See "Human bites: Evaluation and management".)

Splinting is used in the initial immobilization of, and sometimes is the definitive treatment for, metacarpal fractures [1,3,12]. A detailed description of the techniques for applying splints is presented separately. (See "Basic techniques for splinting of musculoskeletal injuries".)

Non-displaced metacarpal shaft fractures should initially be splinted using a gutter splint (picture 6) or Burkhalter-type splint (picture 7) with the wrist in approximately 20 to 30 degrees of extension, the MCPs at 70 to 90 degrees of flexion, and the PIP and DIP in slight flexion [12].

Ulnar gutter splints work well in ring and little finger metacarpal fractures, while radial gutters are effective for index and middle finger metacarpal fractures. Patients with metacarpal shaft fractures should be seen in follow-up within five days and advised to apply ice regularly and elevate the injured hand.

Fractures with an unacceptable degree of angulation require reduction. Angulation of the index and middle finger metacarpal shafts >10 degrees is unacceptable due to the lack of mobility these metacarpals have at the carpometacarpal (CMC) joints. The ring and little finger CMC joints have greater mobility and accordingly slightly more angulation is tolerated in these metacarpal shaft fractures. However, greater than 20 degrees of angulation in the ring finger metacarpal and greater than 30 degrees in the little finger metacarpal warrants reduction.

CLOSED REDUCTION — Acute reduction is indicated for significantly angulated metacarpal fractures. Reduction is also indicated if there is pseudo-clawing as evidenced by hyperextension at the MCP joint and flexion at the PIP joint with attempted extension of the finger.

There are several methods for reducing a metacarpal shaft fracture, the following is our preferred method:

Anesthesia — Anesthesia is typically achieved adequately and expediently using a hematoma block. Additional analgesia may be provided if necessary with oral or parenteral medication.

Preparation for a hematoma block includes cleaning the skin with an appropriate antiseptic (eg, chlorhexidine), followed by alternating injection and aspiration of 5 to 7 cc of 1 percent lidocaine without epinephrine or 0.5 percent marcaine without epinephrine.

The technique involves the initial injection of approximately half of the anesthetic directly into the fracture hematoma from the dorsal side of the hand in the area directly overlying the fracture site. The same volume of blood-anesthetic mixture that was initially injected is then withdrawn from the hematoma. Some clinicians perform repeated injections and aspirations before removing the needle to increase the distribution of anesthetic throughout the fracture site. Once this is done, a volume of blood and anesthetic equal to the initial anesthetic volume is ultimately aspirated, thereby ensuring that the fluid volume of the hematoma remains unchanged.

Performance of fracture reduction — When adequate anesthesia is obtained, the fracture is reduced using the 90-90 method. Initially, flex the MCP, PIP, and DIP joints all to 90 degrees. Next, apply direct axial pressure through the flexed PIP joint, thereby creating a dorsal force on the distal fracture fragment. Simultaneously, apply a volar-directed force over the fracture site until you feel that an anatomic reduction has been achieved. The following picture shows the technique applied to a metacarpal neck fracture, but the approach is the same for metacarpal shaft fractures (figure 7). Then immobilize with a Burkhalter or an ulnar gutter splint.

Closed reduction generally corrects angulation but typically does not restore length [13]. Post-reduction radiographs are imperative to ensure adequate reduction and alignment.

FOLLOW-UP CARE — Non-displaced metacarpal shaft fractures can be immobilized in a gutter or Burkhalter splint for a few days to allow swelling to decrease. The splint may then be exchanged for a short arm cast or a custom orthosis, which is used for the remaining period of immobilization.

Traditionally, metacarpal fractures are immobilized with the metacarpal phalangeal (MCP) joint in significant flexion (approximately 70 degrees) to prevent the loss of MCP extension following removal of the cast or splint. However, a retrospective case series suggests that this approach to immobilization may be unnecessary [14]. In this study, no difference in joint motion, grip strength, or fracture alignment was noted among 263 patients with extra-articular metacarpal fractures immobilized with the MCP joint either flexed or extended and the interphalangeal joints either immobilized or not.

Repeat radiographs are indicated within one week of placing the cast to ensure adequate fracture position. Patients should be informed that oblique fractures and metacarpal shaft fractures at the hand border (ie, involving the index or little finger metacarpal shaft) are at greatest risk for displacement.

Typically, metacarpal shaft fractures require four weeks of immobilization. After the initial week, radiographs should be obtained at one to two week intervals to ensure maintenance of alignment and to assess bony healing. Bone resorption peaks at two weeks, but callus should be present at four weeks. If adequate callus formation is absent at four weeks, an additional immobilization period is necessary with radiographic monitoring at two-week intervals. Usual healing time is on the order of six to eight weeks.

After immobilization is discontinued, a two to three week period of gentle passive and active ROM work at the MCP, PIP, and DIP joints should be initiated at home. If stiffness persists after two to three weeks, formal hand therapy (occupational therapy) is helpful to restore motion.

As for metacarpal neck fractures, custom orthoses are now widely available and can provide adequate immobilization of the fracture while allowing improved mobility of the fingers and rest of the hand. These are typically constructed by an occupational or hand therapist and should be considered in patients at high risk for developing chronic stiffness, such as elders or those with preexisting arthritis.

RETURN TO SPORT OR WORK — Athletes seeking to return to contact sports should be protected for an additional four to six weeks after immobilization with a firm and well-padded orthosis. If adequate stability is achieved with operative fixation, athletes engaged in contact sports may be allowed to return to play in some cases within two weeks, provided they use a fracture brace.

Patients requiring regular use of the affected hand for work may return to full duty when they are pain-free, the hand is non-tender, radiographic evidence of fracture healing is present, and the hand has regained functional range of motion.

PEDIATRIC CONSIDERATIONS — Metacarpal shaft fractures in children are managed in much the same way as they are in adults. One notable difference is the shorter interval for obtaining an initial follow-up radiograph due to the accelerated healing times in children. If there is any concern about maintaining fracture alignment or position, follow-up radiographs should be obtained within one week of the initial evaluation. It is also important to remember that these fractures are unusual in non-ambulatory children. Abuse should be considered in cases involving such children, particularly if the mechanism is questionable or additional fractures or other injuries are identified. (See "Physical child abuse: Diagnostic evaluation and management".)

ADDITIONAL INFORMATION — Several UpToDate topics provide additional information about fractures, including the physiology of fracture healing, how to describe radiographs of fractures to consultants, acute and definitive fracture care (including how to make a cast), and the complications associated with fractures. These topics can be accessed using the links below:

●(See "General principles of fracture management: Bone healing and fracture description".)

●(See "General principles of fracture management: Fracture patterns and description in children".)

●(See "General principles of acute fracture management".)

●(See "General principles of definitive fracture management".)

●(See "General principles of fracture management: Early and late complications".)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Fractures of the skull, face, and upper extremity in adults" and "Society guideline links: Acute pain management".)

SUMMARY AND RECOMMENDATIONS

●Anatomy and injury mechanisms – Metacarpal shaft fractures occur in three patterns: transverse, oblique, and comminuted. (See 'Clinical anatomy' above and 'Fracture patterns and mechanism of injury' above.)

●Clinical presentation and physical examination – Patients typically describe a history of hand trauma and complain of pain along the dorsum of the hand. They are typically unable or unwilling to flex the metacarpal phalangeal (MCP) joint. Shaft fractures occur most frequently in the metacarpal of the little finger. Punching injuries often account for fractures of the ring finger metacarpal shaft. Examination reveals bony tenderness along the affected metacarpal and often a palpable deformity and swelling. (See 'Clinical presentation and examination' above.)

●Assessment of alignment and function – The function of the extensor apparatus, fracture angulation, and rotational alignment (picture 1B) must be assessed. Metacarpal shaft fractures can impair finger extension and result in "pseudo-clawing" (hyperextension at the MCP joint with flexion at the proximal interphalangeal (PIP) joint). (See 'Assessment of hand alignment and function' above.)

●Diagnostic imaging, acceptable angulation, and stability – The standard three views of the hand (anteroposterior [AP], lateral, and oblique) are generally adequate for evaluating metacarpal shaft fractures with plain radiographs. Less angulation is tolerated in metacarpal shaft compared with metacarpal neck fractures. Acceptable fracture angulation is as follows:

•≤10 degrees in second and third (index and middle finger) metacarpals

•≤20 degrees in fourth (ring finger) metacarpals

•≤30 degrees in fifth (little finger) metacarpal shaft fractures

Second and fifth metacarpal shaft fractures and all oblique fractures are less stable than other metacarpal fractures. Oblique fractures tend to shorten and rotate while second and fifth metacarpal shaft fractures often angulate and displace. (See 'Assessment of hand alignment and function' above and 'Diagnostic imaging' above.)

●Indications for surgical referral – Fractures associated with "pseudo-clawing," malrotation, comminution, or shortening >5 mm warrant consultation with an orthopedist or hand surgeon. If more than one metacarpal is fractured or if adequate reduction is not attained or maintained, surgical referral is indicated. Referral is also reasonable for athletes with metacarpal shaft fractures who desire a quick return to competition. (See 'Indications for surgical referral' above.)

●Need for fracture reduction – Acute reduction is indicated if there is evidence of pseudo-clawing and for any significantly angulated metacarpal fractures. (See 'Initial treatment' above and 'Closed reduction' above.)

●Fracture immobilization – Gutter splinting or casting or Burkhalter-type splinting provides adequate immobilization. Less bulky custom orthoses are widely used. They provide necessary fracture immobilization while allowing improved mobility and function in adjacent hand structures, which reduces the risk of chronic joint stiffness (eg, in older adults). (See 'Initial treatment' above.)

●Follow-up care – A follow-up schedule is provided in the text. Early repeat radiographs (within one week) are obtained in children if there is any concern about maintaining fracture alignment or position. (See 'Follow-up care' above.)