ILLUSTRATIVE CASE Mallet Finger in a Toddler A Rare But Easily Missed Injury Karen E. Forward, MD, FRCPC,* Arjang Yazdani, MD, FRCSC,† and Rodrick Lim, MD, FRCPC, FAAP*‡§ Abstract: A mallet finger is a flexion deformity of a finger at the distal interphalangeal joint due to an injury of the extensor mechanism at the base of the distal phalanx. Most common in middle-aged men, injuries in the pediatric population are less common and rare in toddlers. We describe a case of missed mallet finger and its subsequent treatment in a female toddler. Key Words: mallet finger, toddler, hand injuries (Pediatr Emer Care 2017;33: e103–e104) U nlike in adult patients, where mallet finger deformities result from an injury or laceration to the extensor tendon of a digit with or without an associated fracture,1 in skeletally immature children, this injury typically occurs as a result of an avulsion fracture of the distal phalangeal epiphysis—the insertion point of a digit's extensor tendon.2 In young children, delayed diagnosis of this injury type is common,2,3 – likely because of the rarity of this injury in toddlers and the fact that functional impairment often is not immediately noted. Although this injury is rare, we describe here a case of missed mallet finger and its subsequent treatment in a female toddler. CASE A 2-year-old girl presented to the pediatric emergency department with an injury to her right small finger. She had reportedly injured her fifth finger by crushing it in a bedroom door. On her initial examination, she had some abrasions to her finger, with bruising noted over the volar aspect of her finger. A radiograph was performed and its result was reported to be normal (Fig. 1). She was treated conservatively with buddy taping and told to follow up with her family doctor. One week later, she returned to the pediatric emergency department for reassessment because her parents noted that she continued not to use her finger. On physical examination, she was unable to extend the distal interphalangeal (DIP) joint of her fifth finger (Fig. 2). Because the con- FIGURE 1. Initial radiograph. From the *Department of Paediatrics, †Division of Plastic Surgery, Department of Surgery, and ‡Division of Emergency Medicine, Department of Medicine, Schulich School of Medicine at Western University; and §Children's Health Research Institute, at the Children's Hospital at London Health Sciences Centre, London, Ontario, Canada. Disclosure: The authors declare no conflict of interest. Reprints: Rodrick Lim, MD, FRCPC, FAAP, Children's Hospital at London Health Sciences Centre, 800 Commissioners Road East, London, ON, Canada N6C 2V5 (e‐mail: Rod.Lim@lhsc.on.ca). Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. ISSN: 0749-5161 ventional splints in the pediatric emergency department were not sufficiently small, plastic surgery was consulted and a small custom splint was fashioned by an occupational therapist (Fig. 3). The toddler followed up with plastic surgery and, with persistent splinting for 6 weeks, obtained full extension once again. DISCUSSION Mallet fingers are a prevalent adult injury most commonly seen in middle-aged men or older women.4 Fingertip injuries are Pediatric Emergency Care • Volume 33, Number 10, October 2017 Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved. www.pec-online.com e103 Pediatric Emergency Care • Volume 33, Number 10, October 2017 Forward et al In terms of causation, in the very young, congenital causes for mallet finger should also be considered in the differential (eg, congenital extensor tendon deficiency)5; however, in the setting of trauma, hyperflexion is the commonest cause of mallet finger injury in the skeletally immature.6 Other potential causes include tumors (soft or bony) and “mimics” of mallet finger— such as fractures to the distal phalanx, which also may present with a “bent” DIP joint.5 Mallet fingers are described using a classification scheme (I through IV) developed by Doyle.4 Type I injuries are closed injuries to the extensor tendon that may/may not involve a small avulsion fracture. Type II and III injuries involve a laceration and are open, but type III fractures are deep. Finally, type IV fractures are subdivided into 3 groups: A, distal phalanx physeal injuries (pediatrics); B, fractures involving 20% to 50% of the articular surface (adults); and C, fractures involving greater than 50% of the articular surface (adult). Most mallet fingers to pediatric patients will therefore be classified as IV-A.4 Treatment for mallet fingers may be conservative (eg, splinting) or operative,1 and generally, surgical measures are only considered when conventional treatments fail.2 A 2004 Cochrane review looked at the efficacy of off-the-shelf aluminum splints vs custom splints in predominately adult patients and found insufficient evidence to recommend one measure over another—but stressed the importance of compliance and durability with any splint applied.7 In our toddler, whose finger was too small for an off-the-shelf splint, custom splints provided a comfortable alternative and achieved the desired results with constant daily use. FIGURE 2. Picture of the fifth digit. CONCLUSIONS Although extremely rare, mallet fingers can occur in toddlers and young children after seemingly minor trauma. They are often missed on initial presentation and are frequently but not always associated with an avulsion fracture the distal phalangeal epiphysis. It is important for the clinician to be vigilant to look for this injury because it can be easily clinically missed in the very young. Once diagnosed, they can typically be treated conservatively with a well-fitted splint for 6 to 8 weeks and close follow-up. REFERENCES 1. Schmidt B, Weinberg A, Friedrich H. The mallet finger in children and adolescents [in German]. Handchir Mikrochir Plast Chir. 2008;40:149–152. FIGURE 3. Custom splint. common in children, and a mallet finger can be seen, caused by a disruption of the extensor tendon mechanism in the region of the DIP joint in an open epiphyseal plate.2 In a 10-year review of pediatric mallet finger, the average age was 11.3 years.1 Although they are extremely rare injuries to see in the toddler age, there have been a handful of mallet finger injuries described in children as young as 1 year in the orthopedic literature.1,2 In the very young, the examination of the hand can prove to be difficult. The patients are often noncompliant, fearful, and unable to follow specific instructions. Because of the nature of this injury, it is important to be thorough in the assessment of the affected finger, because the diagnosis can be easily missed. e104 www.pec-online.com 2. Kardestuncer T, Bae DS, Waters PM. The results of tenodermodesis for severe chronic mallet finger deformity in children. J Pediatr Orthop. 2008; 28:81–85. 3. Shin EK, Bae DS. Tenodermodesis for chronic mallet finger deformities in children. Tech Hand Up Extrem Surg. 2007;11:262–265. 4. Bendre A, Hartigan B, Kalainov D. Mallet finger. J Am Acad Orthop Surg. 2005;13:336–344. 5. Ganayem M, Edelson G. Base of distal phalanx fracture in children: a mallet finger mimic. J Pediatr Orthop. 2005;25:487–489. 6. Walshaw L. Practical procedures for minor injuries: mallet splint. Accid Emerg Nurs. 2004;12:182–184. 7. Handoll HH, Vaghela MV. Interventions for treating mallet finger injuries. Cochrane Database Syst Rev. 2004:CD004574. © 2017 Wolters Kluwer Health, Inc. All rights reserved. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.