Another Angry Adolescent Another Boxer’s Fracture? Brendan J. Kilbane, MD Abstract: Hand injuries are a common chief complaint in the pediatric population presenting for emergency care. Adolescents, in particular, often present with trauma to their hands after punching objects. The most frequent result of this action is a fracture to one or more of their metacarpals, also known as a boxer’s fracture. However, we present a case with this common mechanism that resulted in an uncommon injury, carpometacarpal joint dislocations. Key Words: carpometacarpal joint, dislocation, hand injury (Pediatr Emer Care 2014;30: 558–560)

CASE A 16-year-old boy presented 1 hour after punching the floor during an argument with his mother. The patient reported that he felt pain immediately, followed by a tingling sensation on his right ring and little fingers as well as on the lateral aspect of his hand. He denied any other injuries or pain. He had a medical history of asthma and oppositional defiant disorder. On examination, he had marked edema of the entire dorsal aspect of his hand with a small abrasion above his fifth metacarpophalangeal joint. There was marked tenderness to palpation over his fourth and fifth metacarpals, but he had no pain on palpation of either the fourth or fifth digits. He had limited flexion and extension of those digits and was not cooperative to strength testing secondary to pain. Sensation to the fourth and fifth digits was intact, but he stated that it “felt different,” and he had normal capillary refill to all digits and an intact radial pulse. A 3 view x-ray was obtained of his right hand was obtained and initially read as “Negative for fracture or dislocation with a short 5th metacarpal” (Fig. 1). On the basis of the degree of pain and edema on examination, the films were reviewed with radiology, and it was decided that the patient had a dorsal dislocation of his fourth and fifth metacarpals at the joints. The hand service was consulted and elected to perform a closed reduction at the bedside, using finger traps for traction and a moderate amount of direct force to the carpometacarpal (CMC) joints. After the procedure, the joint was felt to be stable during range-of-motion exercises, and the patient reported reduced pain and a return of normal sensation to his fourth and fifth digits. The hand was then placed in an ulnar-gutter splint with 30 degrees of flexion, and x-rays were obtained, which demonstrated return to anatomic position of the fourth and fifth metacarpals (Fig. 2). The patient was discharged with a plan for follow-up in 2 weeks, but he missed the appointment and was lost to follow-up. The hand is one of the sites most commonly injured in children and adolescents, with 1 study estimating that more than 2000 From the Rainbow Babies & Children’s Hospital, Division of Pediatric Emergency Medicine, Case Western Reserve University School of Medicine, Cleveland, OH. Disclosure: The author declares no conflict of interest. Reprints: Brendan J. Kilbane, MD, Rainbow Babies & Children’s Hospital, Division of Pediatric Emergency Medicine, Case Western Reserve University School of Medicine, 11100 Euclid Ave, COR 6097, Cleveland, OH 44106 (e‐mail: [email protected]). Copyright © 2014 by Lippincott Williams & Wilkins ISSN: 0749-5161


pediatric patients are seen with hand injuries each day in US emergency departments.1,2 The hand’s injury pattern tends to change as the patient ages, with younger children experiencing crush injuries that result in distal finger trauma, whereas adolescents experience lacerations and fractures due to sports or recreational activities.2,3 One injury that clearly fits this pattern of increasing in frequency with increasing patient age is a fracture to one or more of the lateral metacarpals.4 Our case, however, serves as an example that not every punch results in a boxer’s fracture. Our patient presented with a mechanism that is all too common among adolescents; however, the final diagnosis of CMC joint dislocations was anything but typical. A review of the literature found no reports of isolated fourth and fifth CMC joint dislocations in the pediatric population, although there are case reports of dislocations of the thumb alone,5 of dislocations to all 4 CMC joints,6,7 and of a single CMC joint dislocation with an associated metacarpal fracture.8 Expanding the review to include the adult population, CMC dislocations continue to occur infrequently, with 1 study reporting that they account for approximately only 1% of injuries to the hand and the wrist.9 One reason for the rarity of this injury is the unique anatomy of the CMC joints, which results in a high degree of stability. The metacarpals articulate with each other and the distal row of the carpal bones to form gliding joints. These joints are strengthened by the intermetacarpal and CMC ligaments, as well as the wrist flexor and extensor ligaments. However, the hamate bone, which provides the base for the fourth and fifth metacarpals, has a shallow surface. Although this shape allows those 2 metacarpals to have a small range of motion that assists with the gripping action of the hand, it also makes these 2 joints less stable and at increased risk for dislocation.10,11 Most CMC dislocations, with or without associated fractures, occur in the dorsal direction. These injuries result primarily from 2 mechanisms: either a direct axial load to the head of the metacarpals that spreads down the length of the bones while the wrist is in mild flexion (throwing a punch) or a direct force to the palmar/volar surface of the hand that results in a lever effect being transmitted to the metacarpals (holding a handlebar during a motorcycle crash).12 The diagnosis of a CMC dislocation in patients of any age is at high risk for being missed, with 1 adult study documenting that 9 of 31 cases were initially diagnosed incorrectly.13 A second study found that 15 of 21 injuries were incorrectly diagnosed on initial presentation to the emergency department. Of note, in 5 of these 15 cases, the diagnosis was also missed by the consultant orthopedic surgeon.14 This information is particularly concerning for the acute care physician because making the diagnosis accurately on the initial presentation is crucial, as timely reduction and close observation are critical to ensuring recovery of full grip strength. A review of the literature reveals several recommendations to assist the clinician in making this uncommon diagnosis. One study suggested comparing the long axis measurement between the second and fifth metacarpals, with dislocations having an almost 30-degree difference.15 Another source describes the importance of the expected symmetry between the base of the metacarpal and the surface of the corresponding carpal bone, as seen on the anteroposterior x-ray. It calls the resultant parallel lines Pediatric Emergency Care • Volume 30, Number 8, August 2014

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Pediatric Emergency Care • Volume 30, Number 8, August 2014

Carpometacarpal Joint Dislocations in Adolescents

FIGURE 1. Hand x-ray.

these surfaces make “M Lines” and suggests that either a change in the distance between the lines or a break in their symmetry should trigger concern for a dislocation.16 However, the easiest and most widely recommended technique to make this diagnosis is to obtain a true lateral x-ray, in addition to the anteroposterior and oblique views, which are often the default x-ray views obtained after hand trauma. Eleven of the 15 missed dislocations from the earlier study did not have a lateral x-ray obtained.14 For cases in which uncertainty remains after radiographs, a computed tomography scan can also be used to better demonstrate the anatomy. In addition to these techniques, the clinician should have a high index of suspicion if the patient has significant neurologic symptoms on physical examination and a “normal x-ray,” as was the case with our patient. Involvement of the deep branch of the ulnar nerve at the fifth CMC joint can result in motor or sensory symptoms, as demonstrated in the report of an adult patient who was initially diagnosed with a fifth metacarpal boxer’s fracture and did not have the dislocation of his fourth and fifth CMC joints correctly diagnosed until he presented 9 days later with continued signs of ulnar nerve entrapment.17 Because of the rarity of these injuries in pediatrics, it is recommended that a hand specialist be involved in the initial management and follow-up care. Although there are experts who support closed reduction alone, if done promptly and followed closely to ensure that the reduction does not become unstable, most references advocate surgical management, either percutaneous

pinning or open reduction, because a poor outcome will have substantial impact on the patient’s grip strength and future risk for arthritis.18,19 One large case series reviewed 100 cases of CMC dislocations, most of which involved either only the fifth or the fourth and fifth CMC joints. Of interest, more than 80% of the dislocations also involved a fracture, primarily of the metacarpal base or the corresponding carpal bone. All cases had either closed reduction with pinning or open reduction and fixation. The authors report that 81% of patients were pain-free at follow-up and had full range of motion, which they argued supports aggressive surgical management.20 Independent of initial management strategy, the importance of close follow-up should be stressed to the patients and their families, to prevent their being lost to followup with an injury that, although may appear minor because the initial swelling diminishes, can have lifelong consequences if not managed correctly. Carpometacarpal joint dislocations, although uncommon, can occur in older pediatric patients as a result of throwing a punch. These unusual injuries are at significant risk for being missed on their initial presentation. Emergency care providers should maintain a high degree of suspicion and obtain true lateral x-rays on all patients with high-risk hand injuries. Once diagnosed, a hand specialist should be closely involved in the management of these dislocations because prompt recognition and return of the joints to their anatomic position are crucial to avoiding chronic pain and preventing the loss of grip strength.

FIGURE 2. Hand x-ray after reduction. © 2014 Lippincott Williams & Wilkins

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Pediatric Emergency Care • Volume 30, Number 8, August 2014


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Another angry adolescent: another boxer's fracture?

Hand injuries are a common chief complaint in the pediatric population presenting for emergency care. Adolescents, in particular, often present with t...
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