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Introduction[edit | edit source]
Metacarpal fractures occur frequently among the general population and report for 40% of all hand fractures. The Fracture of the fifth metacarpal neck also known as Boxers Fracture, named after the classic mechanism of injury in which direct trauma is applied to a clenched fist or fall directly onto the hand. Boxer's fracture account for 10% of the metacarpal fractures which particularly occur in contact sports. Nearly, one-fourth of cases occur during athletic events.
Epidemiology/Etiology[edit | edit source]
Hand fractures constitute about 40% of all acute hand injuries, and they constitute about 20% of all fractures occurring below the elbow. Metacarpal fractures typically occur in patients aged 10-40 years, and men are more likely to be affected than women. Young men sustain metacarpal fractures secondary to a punching mechanism or a direct blow to the hand while geriatric females sustain these injuries secondary to a low energy fall. The incidence rate of fracture seen in association with each digit metacarpal bone increases from the radial to the ulnar side. The incidence rate of 2nd metacarpal fractures is lower than the incidence rate of 5th metacarpal fractures.
Pathophysiology[edit | edit source]
Each metacarpal bone comprises of a head located distally, neck, body, and base which is located proximally. Fractures occur as a result of axial load to a clenched fist which causes direct trauma to the metacarpal bone, commonly resulting in apex dorsal angulation due in part to the forces exerted by the pull of the interosseous muscles. These interosseous muscles originate from the metacarpal shafts and insert onto proximal phalanges, responsible for adduction and abduction of the fingers. The collateral ligaments should be taken into consideration during splinting to minimize the risk of loss of motion due to shortening of the ligaments. The ligaments are taut in flexion, and more slack in extension, therefore The MCP joints should be splinted in flexion to prevent shortening (intrinsic plus positioning) since these ligaments are taut in flexion and more slack in extension. When the arteries and nerves supplying the fingers are adjacent to the metacarpal bones are injured in severely displaced Boxer’s fractures, surgical intervention is then required.
Characteristics/Clinical Presentation[edit | edit source]
Patients with Boxer’s fractures present with complaints of dorsal hand pain, swelling, and sometimes possible deformity in the setting of one of the mechanisms typically associated with this injury involving direct trauma to the hand.
Assessment of a potential Boxer’s fracture should comprise of an examination of the entire hand with comparison to the contralateral hand and should include examination of :
- Skin: Closely inspect the skin for any breaks, especially near the metacarpal head, typically the point of impact. When a Boxer’s fracture is sustained by a blow to the face, the recipient’s tooth may cause a laceration or abrasion known as a “fight bite." This may require operative irrigation and debridement.
- Neurovascular exam: As with all suspected fractures, a neurovascular exam should test for sensation, motor function, and blood flow distal to the injury.
- Angulation: Boxer’s fractures are typically associated with apex dorsal angulation, thereby resulting in depression of the MCP joint and loss of the normal knuckle contour. With significantly angulated fractures, “pseudo-clawing” may be observed due to damage to the extensor apparatus; pseudo-clawing is a hyperextension of the MCP joint and flexion at the PIP joint. The degree of angulation is determined using plain films.
- Rotational alignment: Any degree of malrotation warrants referral to a hand surgeon and therefore assessment of rotational alignment is a crucial component of the physical exam. Alignment can be assessed by examining the hand with the MCP and PCP joints in flexion, and DIP joints extended. If lines are drawn along the digits and extended distally, normally aligned digits will show the convergence of these lines. If the line extended from the fifth finger does not converge towards the others, suspect malrotation.
- Malrotation can also be detected by examining the hand with the MCPs flexed, and PCPs and DIPs extended. The fingernails should be in line along a single plane.
Management[edit | edit source]
The treatment for a Boxer’s fracture varies based on initial presentation if the fracture is closed or open, the rotation and degree of angulation and other associated injuries.
Splinting is used for initial immobilization if the fracture is closed, not angulated, and not malrotated or otherwise displaced. A Boxer’s fracture should be immobilized with an ulnar gutter splint. Alternatively, a pre-made Galveston splint or a custom orthosis may be used.
The hand should be positioned in the intrinsic plus position for splinting: mild wrist extension, 70 to 90 degrees of flexion at MCP joint, and slight flexion at the DIP and PIP joints. Flexion of these joints is important to prevent shortening of the collateral ligaments and subsequent loss of range of motion and functional impairment.
Closed reduction is required for a Boxer’s fracture if the angulation is greater than 30 degrees. Analgesia options for the procedure include a hematoma block or an ulnar nerve block. Closed reduction of a Boxer’s fracture is accomplished by using the “90-90 method.” The MCP, DIP, and PIP joints should all be flexed to 90 degrees. The clinician should then apply volar pressure over the dorsal aspect of the fracture site while applying pressure axially to the flexed PIP joint. This axial pressure to the PIP applies dorsal force to the distal fracture fragment. The clinician should be able to feel the reduction when it has been achieved. The injury should be immobilized with an ulnar gutter splint, and post-reduction films should be taken to assess for adequate reduction The fifth metacarpal neck can tolerate angulation of up to 50-60 degrees and management may be continued non-operatively if remains within the acceptable tolerances.
Surgical referral is indicated for fractures that are open, severely comminuted, associated with neurovascular injury, and for fractures with any malrotation. Surgical referral is also appropriate for fractures with significant angulation if the initial provider is unsuccessful in achieving adequate reduction and alignment outside acceptable parameters. Surgical options include open reduction internal fixation, or closed reduction percutaneous pinning.
Radiographs should be repeated within one week to assess alignment and every two weeks until signs of clinical and radiographic healing are present which are usually seen between four to six weeks. After a short period of immobilization, the passive and active range of motion exercises should be performed to alleviate stiffness of the MCP and PIP joints. Literature supports early mobilization of these injuries rather than prolonged immobilization . If any loss of function persists after several weeks of these exercises, referral to occupational therapy is warranted.
References[edit | edit source]
- Malik S, Herron T, Rosenberg N. Fifth Metacarpal Fractures. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.
- Altizer L. Boxer's fracture. Orthop Nurs. 2006 Jul-Aug;25(4):271-3; quiz 274-5.
- Low CK, Wong HC, Low YP, Wong HP. A cadaver study of the effects of dorsal angulation and shortening of the metacarpal shaft on the extension and flexion force ratios of the index and little fingers. J Hand Surg Br. 1995 Oct;20(5):609-13.
- Burkhalter WE. Closed treatment of hand fractures. J Hand Surg Am. 1989 Mar;14(2 Pt 2):390-3.
- Statius Muller MG, Poolman RW, van Hoogstraten MJ, Steller EP. Immediate mobilization gives good results in boxer's fractures with volar angulation up to 70 degrees: a prospective randomized trial comparing immediate mobilization with cast immobilization. Arch Orthop Trauma Surg. 2003 Dec;123(10):534-7.