INTRODUCTION — Metacarpal fractures account for 30 to 40 percent of all hand fractures. These fractures are usually the result of direct 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".)
Splinting is used in the initial immobilization of, and often is the definitive treatment for, metacarpal fractures. A detailed description of the techniques for applying splints is presented separately. (See "Basic techniques for splinting of musculoskeletal injuries".)
This topic will provide an overview of the classification, anatomy, examination, and general management principles of metacarpal fractures. More detailed discussions of specific fractures are presented separately. (See "Metacarpal shaft fractures" and "Metacarpal neck fractures" and "First (thumb) metacarpal fractures" and "Metacarpal base fractures" and "Metacarpal head fractures".)
Overview — Metacarpal fractures are classified anatomically. Fractures of the second, third, fourth, and fifth metacarpals are subdivided into those affecting the metacarpal head, neck, shaft, or base. Due to the unique biomechanics and anatomy of the thumb, fractures of the first metacarpal are classified separately. (See "First (thumb) metacarpal fractures".)
Metacarpal fractures are further described by the degree of displacement, angulation, shortening, rotation, and by the fracture type (transverse, oblique, spiral, comminuted, impacted, or avulsion (figure 1)). The metacarpal neck and shaft are the most common sites for fractures of the second through fifth metacarpals, while the first (thumb) metacarpal is usually fractured at the base. A more detailed discussion of how fractures are categorized and how to describe radiographs of fractures is provided separately. (See "General principles of fracture management: Bone healing and fracture description", section on 'Fracture description'.)
Fracture locations — Issues related to the different locations of metacarpal fractures are discussed separately in the appropriate topic reviews:
ANATOMY — The metacarpals are cortical bones with a concave volar (palmar) surface that is typically 20 percent thicker than the dorsal cortex (figure 2). Proximally, they articulate with the distal carpal row at the carpometacarpal (CMC) joints and with each other at the intermetacarpal joints. Distally, the metacarpals join the proximal phalanx of each finger at the metacarpophalangeal (MCP) joint.
The metacarpals are the key skeletal elements forming the two transverse arches of the hand (at the CMC joint and at the metacarpal heads) and the longitudinal arch through its dorsally convex surface (figure 3). The metacarpals are bound proximally by the palmar and dorsal metacarpal ligaments and distally by the superficial and deep transverse metacarpal ligaments. Collateral ligaments of the MCP joints also provide some degree of stability distally.
The "cam" shape of the metacarpal head changes the support afforded by the collateral ligaments based upon the degree of flexion occurring at the MCP joint. The ligaments relax in extension (allowing lateral motion of the digit) but are taut in flexion (figure 4).
The dorsal and volar interosseous muscles originate from the metacarpal shafts and insert onto the proximal phalanges, thereby functioning as flexors of the MCP joint (figure 5). In metacarpal neck and shaft fractures, the force exerted by these interosseous muscles tends to cause apex dorsal angulation of the fracture (image 6). The common palmar digital arteries and nerves run parallel with the distal portion of each metacarpal. They are rarely injured except in significantly displaced metacarpal head or neck fractures.
The second and third metacarpals are essentially fixed at the CMC joints, providing an anchor for the ligamentous, bony, and muscular attachments of the hand. The fourth and fifth metacarpals have progressively more mobility at the CMC joint. This increased mobility is important for a cupping action of the hand. The thumb is the most mobile of the metacarpals, enabling a unique ability to function in opposition as a pincer.
EXAMINATION — The initial examination of the patient with a suspected metacarpal fracture should include a focused assessment of the following:
●Neurovascular integrity of hand and affected digits
Deformity — The injured metacarpal is examined for displacement and dorsal angulation (figure 6). Hyperextension of the metacarpophalangeal (MCP) joint with flexion of the proximal interphalangeal (PIP) joint at rest or with attempted extension of the finger is referred to as "pseudo-clawing" (figure 7).
Malrotation — The rotational alignment of the metacarpals can be assessed in two ways:
●With a semi-clenched fist (flexion to 90 degrees at the MCP and PIP joints), normal alignment will show convergence of the digits but not necessarily to a single point (picture 1A-B).
●Have the patient flex the MCP joint 90 degrees with 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).
Thorough assessment for malrotation is crucial to the management of metacarpal fractures. Even a few degrees of malrotation will cause clinically significant malalignment and functional deficits. Surgical referral for reduction and possible fixation is necessary if any malrotation is noted [1,2].
Skin integrity — The skin is inspected for evidence of any of the following:
●Puncture wounds, particularly those suggesting bites (picture 3) or with evidence of secondary infection
●Protrusion of bone fragments indicative of a compound fracture
Lacerations or puncture wounds require copious irrigation. If the injuries are suspected to extend deep to the skin, further evaluation is necessary to determine whether tendons have been disrupted or the joint capsule penetrated. If there are injuries to these structures, surgical consultation is necessary. Open management rather than primary closure of the skin wounds is appropriate for lacerations or puncture wounds of the skin that are due to human bites or to bone fragments in the case of a compound fracture. (See "Minor wound evaluation and preparation for closure".)
Suspected hand infections require immediate intervention and surgical consultation. If there are signs of soft tissue infection, wound cultures should be obtained prior to initiating antibiotic therapy. Blood cultures are obtained for febrile or septic patients. Broad spectrum antibiotic coverage is necessary for a hand infection from human oral flora. Although the use of prophylactic antibiotics is of unproven benefit for human bites generally, broad spectrum antibiotics appear to be beneficial with hand bites. Tetanus prophylaxis should be administered as appropriate. If medicolegal considerations warrant, photographs of the injury may be taken with the patient's permission. (See "Human bites: Evaluation and management" and "Overview of hand infections".)
Neurovascular integrity — Damage to neurovascular structures is unusual with isolated metacarpal fractures unless there is substantial displacement or the fracture is in proximity to the motor branch of the ulnar nerve as it courses near the base of the fourth and fifth metacarpals (figure 8). It is appropriate to test skin sensation, intrinsic muscle function (abduction and adduction of the fingers), and capillary refill to determine the integrity of the nerves and arterial supply to the affected fingers.
MANAGEMENT — Major goals in the management of metacarpal fractures include restoring function and mobility, and maintaining proper bony alignment [3-6].The following fundamentals of care apply to all metacarpal fractures; details pertaining to the management of specific metacarpal fracture types are presented separately [7-10]. (See "General principles of acute fracture management".)
●Immobilize the fracture to reduce pain and minimize further tissue injury, particularly of neural and vascular structures.
Because substantial soft tissue swelling can occur, initial immobilization is generally achieved by applying a removable plaster or fiberglass splint. An example may be seen in the following photograph (picture 4).
For nondisplaced, well-aligned, extra-articular fractures, the splint may serve as definitive treatment. In other cases, the splint will later be removed to allow reduction and possibly fixation, or will need to be replaced with a better fitting splint or short arm cast [11,12].
●Apply ice acutely to minimize swelling.
●Maintain the injured hand above the level of the heart to reduce swelling and pain.
●Give appropriate analgesics.
Most patients get adequate pain relief from immobilization of their hand, ice, and over-the-counter analgesics such as acetaminophen or ibuprofen. Opioid analgesics are occasionally needed to control pain during the first three to five days. Patients requesting opiates beyond this time should be reevaluated for irritation from a poorly fitting splint, a missed secondary injury, or a fracture complication. (See "General principles of acute fracture management", section on 'Pain management' and "General principles of fracture management: Early and late complications".)
●Maintain the mobility of unaffected joints [3-5].
Patients with displaced metacarpal fractures awaiting urgent surgical intervention should be managed with splinting, ice, and appropriate analgesics sufficient to control pain.
Further management of metacarpal fractures varies with the anatomic location of the fracture and the extent of injury. (See 'Fracture locations' above.)
COMPLICATIONS — Common complications associated with metacarpal fractures may include joint stiffness, malunion, nonunion, and arthrosis. The risk of these complications can be minimized with appropriate early range of motion exercises (strict immobilization >4 weeks is rarely indicated), careful evaluation to ensure there is no malrotation (malunion is most often the result of angular or rotational deformities), and identification and appropriate treatment of concomitant soft tissue injuries and infection (common causes of nonunion and arthrosis) [1,3,4].
While the majority of metacarpal fractures can be managed successfully nonoperatively, in certain cases (particularly with athletes eager for rapid return to sport), surgery may be appropriate [2,3,13-15].
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:
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".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Fractures (The Basics)" and "Patient education: How to care for your cast (The Basics)" and "Patient education: How to care for your child's cast (The Basics)")
●Beyond the Basics topic (see "Patient education: Cast and splint care (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Metacarpal fractures account for 30 to 40 percent of all hand fractures. These fractures are usually the result of direct trauma, but fatigue fractures can occur in athletes or as occupational injuries due to repetitive stress.
●Metacarpal fractures are classified based upon their anatomy. Fractures of the second (index finger), third (middle finger), fourth (ring finger), and fifth (little finger) metacarpals are subdivided into those affecting the head, neck, shaft, or base of the bone. Due to the unique biomechanics and anatomy of the thumb, fractures of the first (thumb) metacarpal are classified differently. The diagnosis and management of each metacarpal fracture type is discussed in detail separately. (See "Metacarpal head fractures" and "Metacarpal neck fractures" and "Metacarpal shaft fractures" and "Metacarpal base fractures" and "First (thumb) metacarpal fractures" and 'Anatomy' above.)
●The initial examination of a potential metacarpal injury includes an assessment for gross deformity, skin integrity, neurovascular integrity, and malrotation. (See 'Examination' above.)
●The initial management of metacarpal fractures consists of immobilization to reduce pain and minimize further injury, icing to minimize swelling, and analgesia. Over-the-counter analgesic medications are typically sufficient. Ensuring the mobility of unaffected joints and minimizing the immobilization of involved joints help to ensure full motion and function once the fracture has healed. (See 'Management' above.)
●Common complications associated with metacarpal fractures may include joint stiffness, malunion, nonunion, and arthrosis. (See 'Complications' above.)
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