(Amateur) Boxer’s Fracture

Authors: David Cisewski, MD (@dhcisewski, EM Resident Physician, Icahn SoM at Mount Sinai), Ahra Joh, MD (EM Resident Physician, Icahn SoM at Mount Sinai), and Stephen Alerhand, MD (@SAlerhand, Instructor of Emergency Medicine and Ultrasound Fellow, Icahn School of Medicine at Mount Sinai) // Edited by: Alex Koyfman, MD (@EMHighAK, EM Attending Physician, UT Southwestern Medical Center / Parkland Memorial Hospital) and Brit Long, MD (@long_brit, EM Attending Physician, SAUSHEC, USAF)

Case

A 27-year-old male presents to the ED complaining of hand pain.  He states he punched a wall in frustration after his beloved Dodgers blew Game 7 of the World Series.  Physical examination is notable for significant swelling and tenderness over the right 5th metacarpal bone and 9/10 pain with both passive and active flexion and extension of 5th finger.  He displays internal scissoring (malrotation) of 5th metacarpal with finger flexion, with capillary reflex and sensation intact along distal phalanx.  There is no evidence of skin laceration or ecchymosis and no wrist, forearm, or elbow tenderness noted.

Diagnosis: Boxer’s Fracture

What is a boxer’s fracture?

Though most commonly associated with the 5th metacarpal, a boxer’s fracture refers to the fracture of any metacarpal bone.  Metacarpal fractures make up 30-40% of all hand injuries, with fracture of the 5th metacarpal being the most common (Ashkenaze, 1992).  When making a clenched fist, the proximal phalange slides down over the metacarpal head, providing a pathway of direct contact onto the surface with any impact injury. Interestingly, the term ‘boxer’s’ fracture is a bit of a misnomer as it rarely occurs with proper punching form (more correctly, ‘amateur’ boxer’s fracture).

Common presentation includes pain, swelling, and tenderness over the dorsal surface of the hand overlying the fracture metacarpal bone.  A deformity may also be noted with possible skin break or laceration over site of injury.

Diagnose boxer’s fracture

1. Assess for malrotation: With fingers in flexed position, normal alignment can be demonstrated as near-parallel lines extending through 2nd-5th digits with convergence near the scapholunate joint. Any malrotation (or scissoring) resulting from the fractured metacarpal will be seen as movement away from these lines of convergence.   In addition, nail beds will also be misaligned in a malrotated fracture.  While metacarpal fractures can tolerate a certain degree of angulation (see next section), no degree of rotational deformity is acceptable.

2. Assess skin integrity: Any skin breakdown, particularly when involving a fight bite, require copious irrigation and decontamination. Failure to acknowledge such a wound could result in cellulitis or osteomyelitis.

3. Assess for fracture angulation – (X-ray): Optimally you want 3 radiographic views to assess for metacarpal fracture and angulation: AP, lateral, oblique.  The tradition rule of thumb (or “finger”) is that an acceptable angulation exists for each metacarpal without functional impairment, beyond which surgical referral is necessary.  This can be remembered by “10°, 20°, 30°, 40°” for acceptable angulation of the 2nd, 3rd, 4th, 5th metacarpal bone (Henry, 2006).  Note that the normal metacarpal head-to-neck angle is 15 degrees and as such, the degree of fracture angulation is the measured angle minus 15 degrees.

4. Ultrasound: Ultrasound guidance has developed increasing utility among ED detection of bone fractures. One recent study conducted by emergency medicine residents among 96 patients demonstrated 5% sensitivity and 98.3% specificity in the detection of metacarpal fractures using ultrasound guidance versus x-ray as the comparative gold standard.  Worth noting, of the three false-negative fractures identified on x-ray, each were non-displaced, non-comminuted, and not angled (Kocaoğlu, 2016). The ultrasound guided water bath technique further enhances fracture detection reducing discomfort by minimizing probe pressure on site of injury while simultaneously allowing for better resolution and image quality in the area of interest (Blaivas, 2004).  This can be accomplished by submerging the patient’s hand into a basin of water (ice water can be therapeutic for fractures) and directing the ultrasound probe over the site of injury. Best practice is to leave a few centimeters of space between the probe and skin in order to utilize the water as a contrast medium.  Further information can be found at Quick-Hit Ultrasound Probe: Water Bath for Distal Extremity Ultrasound.

It is also important to evaluate the metacarpals in the transverse plane for step-offs. This is completed by visualizing a horizontal arc upon which the cortex of each metacarpal abuts (see dotted arc in image c and d).  As compared to the abutment of the normal metacarpal in image (c), you can see that the fractured metacarpal is displaced from the horizontal arc in image (d) (i.e., “step-off”).

Consulting orthopedics

Though many seasoned physicians see no need to consult orthopedic surgery for diagnosis and treatment of a boxer’s fracture, there is certain core content that should be ready should you decide to call:

• Which finger and where (head, neck, shaft)
• Mechanism of injury, time since injury occurred
• External exam findings – malrotation, overlying bruising or laceration, finger shortening (in comparison to opposite hand), tenderness at wrist/forearm/elbow, motor examination, neurovascular intact in affected extremity
• Imaging – Ultrasound findings, excessive angulation on radiography

Note: Not all metacarpal fractures can be treated with immobilization in the emergency room.  Open fractures, metacarpal head fractures, fractures with malrotation, and multiple fractures may require an open reduction with internal fixation.  When in doubt, call orthopedics!

Treatment of Boxer’s Fracture

Analgesia – Though traditional analgesics such as high-dose aspirin, ketorolac, or opioids provide relief through systemic distribution and central sensitization of pain receptors, nerve blocks with localized lidocaine provide equal pain relief without the systemic side effects (Ünlüer, 2016).

Ulnar nerve block – Much of the pain associated with the 5th metacarpal is localized to the ulnar distribution (see images).  Thus, a nerve block at either the ulnar head or olecranon can offer substantial relief (Ünlüer, 2016).

Ulnar nerve block at the ulnar head (wrist):

1. Collect Equipment:

• 10cc syringe with a 27 gauge needle
• Blunt fill needle (to draw up anesthetic)
• Local anesthetic (Lidocaine or Bupivacaine)
• Antiseptic (Chlorhexidine, Betadine)
• Sterile gloves
• Linear high-frequency ultrasound transducer

2. Identify landmarks – The flexor carpi ulnaris and ulnar head can be used as external markers to direct a linear ultrasound transducer, identifying the ulnar nerve and artery. The ulnar nerve will appear as a hyperechoic bundle with hypoechoic fascicles within it. Its appearance has often been described as a “honeycomb” (see image). The ulnar nerve will be located ulnar to the ulnar artery.

Ulnar nerve landmarks: Image 1 shows flexor carpi ulnaris located medial to the ulnar nerve target image 2 is an ultrasound guided view (linear probe) of the ulnar nerve located ulnar (medial) to ulnar artery.

3. Inject analgesic – Insert 27-gauge needle in space between flexor carpi ulnaris and ulnar head approximately 2cm (one thumbnail length) from wrist crease. Pull back to aspirate and ensure not in vessel before injecting 3-4cc lidocaine. It is best to first inject slightly underneath the nerve. That way, if redirection of the needle is needed to provide more circumferential anesthesia around the nerve, the nerve will have already been pushed more superficial (and not deep) by the initial aliquot of anesthesia.

4. Record procedure – As with any procedure or medication administering, it is important to document your work. This includes the type of procedure, type of anesthetic used, and the amount of anesthetic used in the chart. Consider using a surgical marker to label the location of needle insertion on the patient’s skin with the time of block and your initials.

Reduction metacarpal bone

90-90 method: Flex the MCP, PIP, and DIP joints to 90 degrees (see image).  Grip the finger such that such that the grip allows for simultaneous axial traction and downward volar force onto the fracture metacarpal (see image).  Maintain steady force until a satisfactory reduction and realignment is appreciated.

Splint and immobilize joint

Either a gutter or Burkhalter-type splint (see image) can be used to immobilize the reduced fracture (Tavassolli, 2005). Note that the collateral ligaments connecting the metacarpal bones to the proximal phalanges are taut in flexion and relaxed in extension.  In order to prevent shortening of the ligament during immobilization, it is essential to immobilize the fracture in at least 70 degrees of flexion at the metacarpophalangeal (MCP) joint (Meals, 2013).  In contrast to metacarpal neck fractures in which splint immobilization is the definitive treatment, fractures of the head, base, and shaft require follow-up in 2 to 3 days for a short arm cast once swelling has diminished.

***Always obtain post-reduction radiographic films to ensure satisfactory alignment and reduction. However, as noted in the diagnosis, confirmation of bony alignment at the bedside can be accomplished using ultrasound before sending the patient for x-ray.

Pitfalls of Boxer’s Fractures

Don’t miss a fight bite – Many patients may be hesitant to admit they were involved in an altercation, often times fearing legal repercussions. When an open laceration appears over a hand suspicious for a fighting injury, it is important to create an open dialogue with the patient.  Remind the patient of their right to confidentiality as well as the severity of a missed infection from oral flora.   When in doubt – and if suspected – it may be within your clinical acumen to simply treat the wound as a fight bite with broad spectrum antibiotics and maintaining an open wound (no stitches!)

All that swells is not broken – Before calling Ortho, make sure that there is radiographic evidence of a fracture with malrotation or excessive angulation.  Overlying contusion with swelling and tenderness or a dislocation with impaired phalange mobility can easily mimic a fracture.

Don’t forget the rest of the arm – though less likely, it is important to assess for wrist, forearm, and elbow pain.  Similar to spinal tenderness after a fall from height, we must also assess for axial load from a straight-on punch or fall.

Always show your work – Never send patient out without post-reduction films.  Continued malrotation or dislocation with splint immobilization could result in significant functional impairment.

Summary

• Boxer’s fracture can encompass any metacarpal fracture, though most commonly the 5th metacarpal.
• Traditional diagnosis involves assessment for malrotation (scissoring) and angulation as noted on radiography (“10, 20, 30, 40 degrees => 2nd, 3rd, 4th, 5th MCP”).
• Ultrasound water bath is a useful diagnostic technique that allows for minimization of discomfort and maximization of landmark visualization.
• When consulting orthopedics, be prepared for a thorough understanding of the mechanism and degree of injury as well as radiographic findings.
• An ulnar nerve block with localized lidocaine provides equal pain relief without the systemic side effects of other oral or intravenous medications.
• Reduction using the 90-90 method and splint immobilization can be done in the ED with close outpatient follow-up.
• Don’t miss fight bites or distal extremity injury.

References / Further Reading

Ashkenaze DM, Ruby LK. Metacarpal fractures and dislocations. Orthop Clin North Am 1992; 23:19.

Blaivas, Michael, et al. “Water bath evaluation technique for emergency ultrasound of painful superficial structures.” The American journal of emergency medicine 22.7 (2004): 589-593.

Davison PG, Boudreau N, Burrows R, Wilson KL, Bezuhly M. Forearm-Based Ulnar Gutter versus Hand-Based Thermoplastic Splint for Pediatric Metacarpal Neck Fractures: A Blinded, Randomized Trial. Plast Reconstr Surg. 2016;137(3):908-16.

Henry MH. Fractures and dislocations of the hand. In: Rockwood and Green’s fractures in adults, 6th edition, Bucholz RW, Heckman JD, Court-Brown C (Eds), Lippincott, Williams & Wilkins, Philadelphia 2006. P.772.

Kocaoglu S, Ozhasenekler A, Icme F, Pamukcu Gunaydin G, Sener A, Gokhan S. The role of ultrasonography in the diagnosis of metacarpal fractures. Am J Emerg Med. 2016;34(9):1868-71.

Meals C, Meals R. Hand fractures: a review of current treatment strategies. J Hand Surg Am. 2013;38(5):1021-31

Tavassoli J, Ruland RT, Hogan CJ, Cannon DL. Three cast techniques for the treatment of extra-articular metacarpal fractures. Comparison of short-term outcomes and final fracture alignments. J Bone Joint Surg Am. 2005;87(10):2196-201.

Ünlüer, EE. Ultrasound-guided Ulnar Nerve Block For Boxers Fractures. Am.J.Emerg.Med. 2016;34(8):1726.