Orthopaedic Hand Trauma CH32 (1)

CHAPTER 32 Mallet Finger

Steven R. Niedermeier and Hisham M. Awan


■ ■ Mallet finger is an injury to the terminal extensor mechanism at the level of the distal interphalangeal (DIP) joint. This can be caused by either tendon rupture in zone 1 or an avulsion fracture of the distal phalanx with a fragment of bone that remains attached to the tendon. ■ ■ There are two proposed mechanisms of injury. ● ● Traumatic impaction blow ( Figure 32.1 )— the initial step involves an axial force to finger held in extension followed by either one of two steps: ◆ ◆ Extreme passive DIP joint hyper flexion , which results most commonly in a tendinous mallet finger. ◆ ◆ Extreme passive DIP joint hyper extension , which results most commonly in a bony mallet finger. ● ● Dorsal laceration— less common; sharp or crushing laceration to the dorsal DIP joint ■ ■ Mallet fingers comprise approximately 9% of all tendinous/ligamentous lesions with an incidence estimated at 5.6% of all tendinous lesions in the hand. The literature does not show any gender difference; however, high-energy injuries are seen in younger, male patients and low-energy mechanisms are seen in the elderly. ■ ■ The ulnar three fingers are the most commonly affected digits, and tendinous injuries are more common than bony avulsion injuries. ■ ■ With the loss of the terminal extensor tendon insertion, the central slip receives all of the tension; the volar plate and transverse retinac- ular ligament attenuate; the lateral bands sublux dorsally; and the proximal interphalangeal (PIP) joint may be forced into extension in chronic injures. The inability to extend the DIP joint and the PIP joint extension is referred to as a swan neck deformity of the finger ( Figure 32.2 ).



SECTION 3  | Tendon Injuries

Figure 32.1  Mechanisms of injury for mallet finger.

Extensor tendon

Collateral band

Mallet injury

Central band

Terminal tendon


FDS rupture

Lateral band

Lax volar plate

Lumbrical muscle

Transverse retinacular ligament

Interosseous muscle

Figure 32.2  Mechanism of swan neck deformity in the setting of mallet finger. FDS, flexor digitorum superficialis; FDP, flexor digitorum profundis.


■ ■ Patient’s history usually includes mechanism of injury, and the patient will usually present in the acute phase.


CHAPTER 32  | Mallet Finger

■ ■ Patients will most commonly endorse painful and/or swollen DIP joint as the primary complaint. In addition, patients will complain of an inability to extend the DIP joint. ■ ■ On examination, the patient will have a painful and swollen DIP joint with the joint held in flexion ( Figure 32.3 ). The patient will lack the ability to actively extend the tip of the finger. ● ● It can often be difficult to note a DIP joint resting in flexion because of the amount of joint swelling.The examiner can passively (hyper)extend the DIP joint and ask the patient tomaintain this position. Patients with a mallet finger will not be able to maintain extension of the fingertip. ■ ■ Plain radiographs can reveal a bony avulsion of the dorsal lip of the distal phalanx articular surface ( Figure 32.4 ). If the injury is purely tendinous, the DIP joint will appear to rest in flexion without a bony avulsion ( Figure 32.5 ). ■ ■ There are two classification systems that are used most commonly: ● ● Wehbe and Schneider —describes injury severity ( Table 32.1 ) ● ● Doyle —describes injury pattern ( Table 32.2 )


■ ■ DIP joint splinting is the most common initial treatment for either tendinous or bony mallet fingers.

Figure 32.3  Clinic photograph of mallet finger injury.


SECTION 3  | Tendon Injuries

Figure 32.4  Lateral plain radiograph of a bony mallet finger injury.

● ● If there is an open injury, the patient should receive an up-to-date tetanus booster, antibiotics, and thorough irrigation, debridement, and exploration of the wound bed under local anesthesia upon presentation.


■ ■ Nonoperative— There are many iterations of splint immobilization that are utilized for nonoperative management of mallet finger injuries. The primary goal, regardless of splint type, is to hold the DIP joint in extension to oppose the ruptured terminal extensor tendon or bony avulsion in place. ● ● Indications ◆ ◆ Acute (less than 12 weeks) soft tissue injury ◆ ◆ Nondisplaced bony mallet injury


CHAPTER 32  | Mallet Finger

Figure 32.5  Lateral plain radiograph of a tendinous mallet finger injury.

● ● Full-time splinting is recommended for 6 to 8 weeks to avoid gap formation. The PIP joint should be left free to avoid unnecessary joint stiffness. ● ● This is followed by 2 to 6 weeks of nighttime splinting and splinting during vigorous activities. Progressive flexion exercises can begin at 6 weeks. Table 32.1  Wehbe and Schneider Classification Types 1 No distal interphalangeal (DIP) joint subluxation 2 DIP joint subluxation 3 Epiphyseal and physeal injuries Subtypes A Less than 1/3 of the articular surface B 1/3– 2/3 of the articular surface C More than 2/3 of the articular surface


SECTION 3  | Tendon Injuries

Table 32.2  Doyle Classification Type I

Closed injury with or without small dorsal avulsion fracture

Type II Type III Type IV

Open injury (laceration)

Open injury (deep soft tissue abrasion involving skin and tendon substance)

Mallet fracture Distal phalanx physeal injury (pediatrics) Fracture involving 20–50% of the articular surface Fracture involving greater than 50% of the articular surface

● ● Most commonly used splints include ( Figure 32.6 ) ◆ ◆ Prefabricated, molded polyethylene (Stack) splint ◆ ◆ Custom, thermoplastic Stack splint ◆ ◆ Abouna splint ● ● A residual extensor lag may persist at cessation of closed treatment (although it is typically less than 10°). ■ ■ Operative —Most authors agree that the classification of the lesion is the most important indicating factor for surgical management. Patient demographics, history on presentation, time since the injury, and the degree of extension deficit are also commonly used to determine need for surgical intervention. ● ● Absolute indications ◆ ◆ Volar subluxation of the distal phalanx ◆ ◆ Inability to tolerate splinting ● ● Relative indications ◆ ◆ More than 50% of the articular surface is involved. ◆ ◆ More than a 2-mm articular gap ● ● Contraindications ◆ ◆ Simple, closed mallet finger injuries

Figure 32.6  Different splint types. A, alumifoam extension splint. B, molded plastic stack splint. C, oval-8 finger splint.


CHAPTER 32  | Mallet Finger

■ ■ Closed reduction percutaneous pinning (CRPP) versus open reduc- tion internal fixation (ORIF) ● ● CRPP— extension block pinning consists of a Kirschner wire (K-wire) through the extensor tendon dorsally and proximal to the avulsion fragment into the middle phalanx. The DIP joint is then extended, and this K-wire acts as a lever to reduce the avul- sion fragment into the distal phalanx. A transarticular K-wire is then placed in a retrograde fashion through the distal phalanx and into the middle phalanx to prevent DIP joint flexion and loss of reduction ( Figure 32.7 ). ◆ ◆ Complications— short-term stiffness, septic arthritis, improper fracture reduction, and posttraumatic osteoarthritis ◆ ◆ Postoperative care— Routinely the DIP joint is immobilized in extension for 6 to 8 weeks to allow the extensor tendon to heal before K-wire removal in clinic. This is followed by nighttime splinting in extension for an additional 2 to 4 weeks. Formal physiotherapy is often helpful to regain DIP joint range of motion and strength. ● ● ORIF— There are a myriad of different techniques that use K-wires, small screws, hook plates, sutures, tension band, etc. The main ad- vantage of this procedure is the direct access to the extensor tendon. Exposure is routinely made through a dorsal approach overlying the DIP joint.

Figure 32.7  Lateral radiograph utilizing dorsal block and transarticular closed reduction percutaneous pinning techniques.


SECTION 3  | Tendon Injuries

■ ■ Acute open mallet finger— For a purely tendinous mallet, a combina- tion of irrigation and debridement with primary tendinous repair and primary closure is indicated. If primary repair of the extensor tendon cannot be achieved, the tendon may be sutured incorporating the skin (tenodermodesis) or can be reconstructed with tendon graft in a primary or delayed fashion. The patient is then splinted in DIP joint extension postoperatively.


CRPP vs ORIF for distal phalangeal volar subluxation, inability to tolerate splinting, >50% of articular surface involved, or >2mm of articular step-off


Splinting for 6-8 wk for acute (less than 12 wk) soft tissue injury or non- displaced bony mallet injury.

2-4 wk of nighttime splinting


Mallet Injury

Primary Operative Repair



Antibiotics, irrigation/ debridement, and splinting


SUGGESTED READINGS Alla SR, Deal ND, Dempsey IJ. Current concepts: mallet finger. Hand . 2014;9:13-44. Botero SS, Hidalgo Diaz JJ, Benaida A, Collon S, Facca S, Liverneaux PA. Review of acute traumatic closed mallet finger injuries in adults. Arch Plast Surg . 2016;43:134-144. Cheung JPY, Fung B, Ip WY. Review of mallet finger treatment. Hand Surg . 2012;17(3):439-447. Wehbe MA, Schneider LH. Mallet fractures. J Bone Joint Surg Am . 1984;66(5): 658-669.

Made with FlippingBook HTML5