Minor Care Series: Finger Tendon Injuries

Although it is common to diagnose finger fractures in the emergency department with reasonable reliability via a hand X-ray, it is much easier to overlook tendon and ligament injuries in patients that present with finger/hand pain, especially in those with range of motion limited by pain. This post serves to explore a few of the more common tendon/ligament injuries that we encounter in the emergency department: Mallet Finger and Jersey Finger.


Mallet Finger

 Figure 1. Mechanism of injury of mallet finger [1]

Figure 1. Mechanism of injury of mallet finger [1]

Traumatic disruption of the terminal slip of the extensor tendon at the Distal Interphalangeal (DIP) joint (Figure 1), known as “mallet finger,” occurs frequently in athletes that participate in contact sports, or ball handling sports, such as basketball.  The injury occurs when a force exerted on the dorsal aspect of the distal phalanx forces the finger into exaggerated flexion.  This causes the terminal portion of the extensor tendon to partially or completely rupture. This particular injury is also commonly associated with an avulsion fracture of proximal aspect of the distal phalanx depending on the force of traumatic insult [2].

 Image 1. Middle Finger DIP in Unopposed Flexion due to Mallet Finger injury [3]

Image 1. Middle Finger DIP in Unopposed Flexion due to Mallet Finger injury [3]

In the emergency department, the patient will usually present with swelling/erythema overlying the dorsal aspect of the DIP with the affected finger in unopposed flexion at the distal phalanx due to loss of function of the terminal portion of the extensor tendon (Image 1). The degree of flexion of the distal phalanx depends on the degree of injury as complete rupture of the extensor tendon results in greater than 30 degrees of flexion whereas partial tears can result in 5 to 20 degrees of flexion. It is important to isolate the DIP when evaluating these patients by holding the Proximal Interphalangeal (PIP) in extension and instructing the patient to range the distal phalanx for full evaluation of injury. Although active range of motion is usually compromised in these patients, physicians should be able to passively extend the finger with full range of motion. Lack of passive extension may be indicative of soft tissue or bony entrapment and would require urgent surgical referral [4].

After physical examination, it is important to obtain a finger X-ray to determine if an avulsion fracture is present and the degree of displacement of the fracture. When no fracture is present or if there is an avulsion fracture that is closed and non-displaced, the affected finger can be splinted (volar or dorsal) with the distal phalanx in full extension with free movement of the PIP joint. This splint is typically worn for 6-8 weeks with flexion exercises of the DIP being introduced approximately 6 weeks post-injury. When a closed avulsion fracture of the distal phalanx is present with volar subluxation, the patient should be referred to a surgeon to determine if the patient requires surgical intervention. A recent systematic review performed by Lin and Samora in 2018 determined that surgical vs. non-surgical intervention had no difference in the rate of complications and overall clinical outcome [5]. Open fractures or complete lacerations of the tendon also warrant a surgical consult to determine optimum therapy for the patient.


Jersey Finger

 Figure 2. Location of Injury in Jersey Finger [6]

Figure 2. Location of Injury in Jersey Finger [6]

Rupture of the flexor digitorum profundus from its attachment at the distal phalanx (Figure 2), or “Jersey Finger,” frequently occurs in football or flag football when an athlete hyperextends the distal phalanx at the DIP joint while flexing the proximal phalanx at the PIP and Metacarpal Phalageal (MCP) joints when grabbing a jersey. In approximately 75% of jersey finger cases, the ring finger (4th digit) is affected; this has been hypothesized to happen due to increased protrusion of the ring finger during grip by approximately 5mm in roughly 90% of the population [7, 8].

In the emergency department, patients affected by jersey finger usually present with edema and pain overlying the volar aspect of the DIP and distal phalanx as seen in image 2  On physical exam, with isolation of the distal phalanx by holding proximal phalanx in extension, the patient will not be able to actively flex the distal phalanx. Another way to test function of distal phalanx flexion is to instruct the patient to make a fist; if the patient’s distal phalanx of the affected finger protrudes in the palm of their hand, the concern for jersey finger should increase.

 Image 2. Volar Edema of Distal Phalanx observed in Jersey Finger [9]

Image 2. Volar Edema of Distal Phalanx observed in Jersey Finger [9]

After physical examination, a three-view finger X-ray (AP, Lateral, Oblique) should be obtained to evaluate for avulsion fractures. In the absence of fractures with unclear certainty of tendon injury/rupture, outpatient providers may opt to pursue an MRI of the hand to further ascertain the presence of injury in the flexor digitorum profundus.

 Figure 3. Depiction of VLS and VLP and their connection to vascular supply of finger [10]

Figure 3. Depiction of VLS and VLP and their connection to vascular supply of finger [10]

All cases of Jersey Finger require surgical intervention. Without surgical intervention, permanent loss of flexion at the DIP joint of the affected finger can occur. The timing for surgical intervention is determined by the Leddy and Packer classification system, as seen in Table 1 [11]. This classification system is based off both the presence of tendon retraction and the presence of a fracture. Class I and Class IV classification requires emergent surgery when compared to Class II and Class III classification due to disruption of the viniculum longus profundus and the viniculum brevis profundus which can lead to vascular compromise of the finger if not fixed immediately as seen in Figure 5.

Although location of Flexor Digitorum Profundus (FDP) retraction can sometimes be evaluated by physical exam, a more accurate measurement requires the use of MRI. Therefore, for injuries in the emergency department where an MRI is not feasible during an ED visit, it is advised to obtain prompt follow-up with a hand surgeon within a week for evaluation of injury. Patients do not require splinting at discharge as it does not contribute to improved clinical outcomes; however, a dorsal splint with 30 degrees of wrist flexion with the affected finger in 30-45 degrees of flexion at the PIP and DIP and 70 degrees of flexion at the MCP can be used for comfort [7].

 Table 1. Leddy and Packer classification system [11]

Table 1. Leddy and Packer classification system [11]


Learning Points

  • Mallet Finger: Inability to extend the DIP due to disruption of the terminal slip of the extensor tendon at the DIP joint.  Appropriate interventions in the ED include splinting the affected finger in extension and having the patient follow up with a hand surgeon.
  • Jersey Finger: Inability to flex the DIP Disruption of the FDP at the distal phalanx.  All cases will eventually require surgery.  Appropriate interventions in the ED include splinting for comfort and having the patient follow up with a hand surgeon within a week.

Authored by: Shan Modi, MD 

Edited by: Tim Murphy, MD


Resources:

  1. Mallet Finger Mechanism. Available at: https://upload.wikimedia.org/wikipedia/commons/a/a7/Mallet_finger_mechanism.png. (Accessed: 13th July 2018)
  2. Bendre, A. A., Hartigan, B. J. & Kalainov, D. M. Mallet finger. J Am Acad Orthop Surg 13, 336–344 (2005).
  3. Mallet_Finger_Injury.jpg (2663×2663). Available at: https://upload.wikimedia.org/wikipedia/commons/b/b4/Mallet_Finger_Injury.jpg. (Accessed: 13th July 2018)
  4. Lee, S. J. & Montgomery, K. Athletic hand injuries. Orthop. Clin. North Am. 33, 547–554 (2002).
  5. Lin, J. S. & Samora, J. B. Surgical and Nonsurgical Management of Mallet Finger: A Systematic Review. The Journal of Hand Surgery 43, 146–163.e2 (2018).
  6. Finger Anatomy - Gray's - Wikimedia Commons. Available at: https://commons.wikimedia.org/wiki/File:Gray416.png. (Accessed: 13th July 2018)
  7. Perron AD1, Brady WJKeats TEHersh RE. Orthopedic pitfalls in the emergency department: closed tendon injuries of the hand. Am J Emerg Med. 2001 Jan;19(1):76-80. (Accessed: 10th July 2018)
  8. Bynum, D. K. & Gilbert, J. A. Avulsion of the flexor digitorum profundus: anatomic and biomechanical considerations. J Hand Surg Am 13, 222–227 (1988).
  9. Jersey Finger. Available at: https://images.radiopaedia.org/images/5259686/9c1d473d7878d5c45d9afb4649fb55_jumbo.jpg. (Accessed: 13th July 2018)
  10. B9781437722307000010_f001-006-9781437722307.jpg (550×263). Available at: https://plasticsurgerykey.com/wp-content/uploads/2016/03/B9781437722307000010_f001-006-9781437722307.jpg. (Accessed: 13th July 2018)
  11. Leddy, J. P. & Packer, J. W. Avulsion of the profundus tendon insertion in athletes. J Hand Surg Am 2, 66–69 (1977).