Boxer’s Break: Metacarpal Fractures

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A 21-year-old male presents to the emergency department (ED) with pain and swelling in his left hand several hours after an injury that occurred while playing football with his friends. The patient reports that his hand was forced into the ground during a tackle. He heard a “crunching” sound and assumed he jammed his ring finger. He pulled on his finger to alleviate the pain and continued playing. On presentation, his exam is remarkable for swelling of the entire left hand with tenderness noted along the dorsal aspect of the left 4th metacarpal. There is weakness with finger flexion, but he is otherwise neurovascularly intact. His X-ray reveals an angulated metacarpal neck fracture.

Mechanism
Hand and wrist injuries account for 15-25% of ED-related musculoskeletal injuries.1 Metacarpal fractures commonly occur around the metacarpal neck as a result of direct contact of an object (or person) with a closed fist. The colloquial term “boxer’s fracture” is generally used to describe a metacarpal neck fracture of the small finger. There is also usually volar displacement of the metacarpal head due to the force vector across the metacarpophalangeal (MCP) joint during a closed-fist strike.

Diagnosis
Making the diagnosis entails a thorough history, detailed examination, and proper imaging. The patient may be hesitant to disclose the mechanism of injury if it occurred during a fight for fear of repercussion or embarrassment. Particularly if there is a dorsal laceration over the MCP joint, it is important to press the patient for a true mechanism of injury. This is because a fight bite injury significantly alters the management course, carrying the implication of surgical management and antibiotic coverage to avoid significant morbidity.

AP and oblique radiographic views of the hand should be obtained, and lateral views may help in assessing the degree of bony displacement and angulation along with any other potential injuries at the carpometacarpal joint.2

Management
Emergency department management of an uncomplicated boxer’s fractures (nondisplaced or minimally displaced, no rotational deformity, acceptable angulation) entails conservative care with immobilization. It is important to thoroughly examine for any abrasions or lacerations before attempting reduction and immobilization. In addition, patients should be treated with analgesia, ice, and elevation in the first 72 hours. Open fractures, involvement of multiple metacarpals, and fractures with neurovascular compromise require surgical consultation.3

Closed reduction is indicated if there is unacceptable angulation or rotational malalignment. This is because inappropriate recognition of metacarpal fractures with unacceptable angulation or rotational deformities may result in long term weakness in grip strength, or functional deficits related to a “scissoring” effect of a malrotated digit. Unacceptable angulation is defined as >10° in the second and third metacarpals, >20° in the fourth metacarpal, and >30° in the fifth metacarpal.4 The fourth and fifth metacarpals have an excellent capacity for remodeling and can tolerate more deformity because of their increased mobility relative to the second and third metacarpals. Additionally, the intermetacarpal ligaments and surrounding musculature make these fractures inherently more stable and more amenable to conservative treatment.

Reduction Technique
A hematoma block using 1% lidocaine without epinephrine usually provides adequate local anesthesia for reduction. However, an additional digital block can aid in both evaluation of metacarpal malrotation during finger flexion and enable the provider to perform fracture reduction, if indicated. The classically described reduction maneuver uses the 90-90 method to correct angulation.5 During this maneuver, the MCP joint is flexed to 90 degrees while a dorsally-directed force is applied to the proximal phalanx, correcting the volar angulation of the metacarpal head. This method takes advantage of the tightened collateral ligaments attached to the metacarpal head during this 90 degrees of flexion, ultimately facilitating this reduction. Next, dorsal volar pressure is applied simultaneously with axial pressure on the PIP. This technique attains the proper anatomical reduction for further immobilization by splinting.

Immobilization and Splinting
A gutter splint or cast should be used to immobilize a metacarpal fracture.6 This is often definitive management for fractures that meet acceptable radiographic parameters. A gutter splint may be modified based on the location of the injured finger. An ulnar gutter splint, also subsequently called a “boxer splint”, should be used for fourth or fifth metacarpal fractures leaving the thumb, index, and ring fingers free. A radial gutter splint should be used for second or third metacarpal fractures, with a hole for the thumb while leaving the ring and little finger free. The technique involves application of the splint from the proximal forearm to just beyond the DIP joint. Especially important for fractures with rotational deformity prior to reduction is “buddy taping” the injured digit to its neighboring digit. This provides rotational stability to the finger while in a definitive splint or cast.

Proper placement of gutter splints is technical and sometimes challenging to achieve without the help of another provider. It is critical that the hand be placed in the “intrinsic-plus” position, which is a safe position for prolonged finger immobilization and limits the degree of stiffness after casting is complete. This involves slightly extending of the wrist, placing the MCP joint between 70° and 90° of flexion and extending the PIP and DIP joints. Post-immobilization imaging is crucial for ensuring sufficient reduction and alignment.

Case Conclusion
Closed reduction using the 90-90 method was achieved with the utilization of a digital block. An ulnar gutter splint was placed and post-reduction imaging demonstrated an appropriate reduction and alignment. The patient was discharged with pain control, an arm sling for elevation, and instructions for orthopedic follow-up. He was subsequently seen in the orthopedic clinic where the fracture demonstrated maintained alignment and a cast was placed with removal scheduled in four weeks.

References

  1. Onselen EBHV, Karim RB, Hage JJ, Ritt MJPF. Prevalence and Distribution of Hand Fractures. J Hand Surg Br Eur Vol. 2003;28(5):491-495. doi:10.1016/S0266-7681(03)00103-7.
  2. Lamraski G, Monsaert A, De Maeseneer M, Haentjens P. Reliability and validity of plain radiographs to assess angulation of small finger metacarpal neck fractures: human cadaveric study. J Orthop Res Off Publ Orthop Res Soc. 2006;24(1):37-45. doi:10.1002/jor.20025.
  3. Ashkenaze DM, Ruby LK. Metacarpal fractures and dislocations. Orthop Clin North Am. 1992;23(1):19-33.
  4. Ali A, Hamman J, Mass DP. The biomechanical effects of angulated boxer’s fractures. J Hand Surg. 1999;24(4):835-844.
  5. Howes DS, Kaufman JJ. Plaster splints: techniques and indications. Am Fam Physician. 1984;30(3):215-221.
  6. Splints and Casts: Indications and Methods – American Family Physician. http://www.aafp.org/afp/2009/0901/p491.html. Accessed December 6, 2016.
Ibbad Yousuf, MS-IV

Ibbad Yousuf, MS-IV

Ibbad Yousuf, MS-IV

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R. Ian Ross, MD

R. Ian Ross, MD

Ian Ross is the 2016-2017 Chair of the EMRA Sports Medicine Division and a Sports Medicine Fellow at O'Connor Hospital in San Jose, CA.
R. Ian Ross, MD

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Albert Leung, MD

Albert Leung, MD

Albert Leung is the 2017-2018 Chair of the EMRA Sports Medicine Division and is a resident at the University of Chicago in Illinois.
Albert Leung, MD

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