Mallet Finger

Mallet Finger

Figure 41-22 Divisions of type I mallet injury showing avulsion without (A) and with (B) bone fragment. Type IV mallet injury: Transepiphyseal (C); hyperflexion with fragment involving 20% to 50% of the articular surface (D); and hyperextension injury with 50% or greater articular surface, and often volar subluxation (E). (From Hastings, Rettig, Strickland: Management of Extra-articular Fractures of the Phalanges and Metacarpals. Philadelphia, Elsevier, 1992.)

Disruption of the terminal extensor tendon at its insertion on the distal phalanx is one of the most common tendon injuries in sports. It is known as mallet finger, drop finger, or baseball finger. This is especially common in softball, baseball, and basketball and in football receivers.1 The injury usually occurs when a ball or other object hits the tip of the finger resulting in a flexion force while the extensor is actively contracting. The mallet deformity also may result from a direct blow to the dorsum of the DIP joint or secondary to a hyperextension force at this joint.69

Anatomically the lateral bands merge and intertwine to form one tendon just distal to the dorsal tubercle of the proximal portion of the MP. This tendon forms a wide structure that inserts into the dorsal base of the distal phalanx, attaching to the dorsal part of the capsule and anterior ridge distal to the articular cartilage.70

McCue and Wooten71 classify mallet finger pathology into five types: (1) tendon stretching, (2) tendon rupture, (3) rupture with avulsion fragment, (4) large fracture fragment, and (5) epi-physeal fracture. An alternate classification is by Doyle,72 with four main types. Type I is a classic hyperflexion injury in which the tendon is avulsed or stretched, which may be accompanied by a small fragment of bone being avulsed from the base of the distal phalanx. Type II involves laceration in which the tendon is divided. Type III is quite rare and involves an abrasion with loss of skin and subcutaneous and tendinous tissue over the DIP joint. Type IV is a mallet fracture, which can be subdivided into

(1) transepiphyseal, (2) hyperflexion injury with a fragment involving 20% to 50% of the articular surface, and (3) hyperextension injury in which the fragment involves 50% or more of the articular cartilage (Fig. 41-22). The hyperextension type is frequently accompanied by volar subluxation of the joint.

Mallet finger is readily detected on physical examination by the flexion posture of the DIP joint and the inability to actively extend the joint. Stability of the DIP joint should also be tested to evaluate possible involvement of the collateral ligaments, although this is rare. A true lateral radiograph is mandatory to determine the presence or absence of a fracture fragment and whether subluxation of the joint exists.

Most authors agree that treatment of closed injuries with or without fracture primarily involves simple splinting of the DIP joint in full extension (Fig. 41-23). The splint should maintain the DIP joint in full extension, allowing free PIP motion. The extensor mechanism is moderately lax at the MP, PIP, and DIP joints when the DIP joint is in extension. Allowing ROM at the PIP joint level minimizes stiffness of this joint and permits more normal use of the hand during treatment.

Splints may be applied to the volar or dorsal aspects of the joint and should remain in place continuously for a minimum of

Figure 41-22 Divisions of type I mallet injury showing avulsion without (A) and with (B) bone fragment. Type IV mallet injury: Transepiphyseal (C); hyperflexion with fragment involving 20% to 50% of the articular surface (D); and hyperextension injury with 50% or greater articular surface, and often volar subluxation (E). (From Hastings, Rettig, Strickland: Management of Extra-articular Fractures of the Phalanges and Metacarpals. Philadelphia, Elsevier, 1992.)

6 to 8 weeks. Excellent results have been reported using these methods. McFarlane and Hampole73 have reported satisfactory results using a splinting program in mallet cases that presented as late as 3 months after injury.

In certain cases in which wearing a splint is not practical, such as in the health care professional, a single longitudinal K wire may be placed percutaneously across the DIP joint to maintain extension and allow continued function. This technique has limited application and is not usually recommended in the athlete. Continued participation in most sports is allowed during treatment of mallet finger as long as the finger is splinted appropriately. Injuries to the throwing hand of a baseball pitcher or football quarterback may result in some time loss from sport, although figure-eight taping to prevent full flexion may be employed.

Transepiphyseal fractures must be reduced anatomically and satisfactorily stable reduction may be maintained by external

Figure 41-23 The Orthoplast splint maintains the distal interphalangeal joint in full extension and allows motion at the proximal interphalangeal joint.

splinting. If significant instability is present, soft-tissue interposition is frequently present and open reduction internal fixation using a longitudinal K wire is indicated. The K wire may be continued for 4 weeks, and then protection for sports is indicated for an additional 4 weeks.71

Conflict of opinion exists as to the treatment of hyperextension injuries in which a considerable size fracture fragment is present with volar subluxation of the joint. Lange and Engber74 and Crawford75 recommend open treatment when subluxation exists to restore joint congruity. They recommend placement of a transepiphyseal pin and fixation of the dorsal fragment with K wires or pull-out suture or wire. Dorsal extension block fixation technique has recently been proposed by Hofmeister et al76 as another alternative of internal fixation. Wehbe and Schneider,77 on the other hand, recommend closed treatment of mallet injuries including cases in which subluxation is present. They maintain that satisfactory remodeling occurs so that DIP joint function is adequate.

Chronic mallet injuries, if left untreated, may progress to a flexion deformity at the DIP joint and hyperextension deformity at the PIP joint (swan neck lesion). Delayed treatment of chronic mallet injury depends on the severity of the deformity and symptomatology and is beyond the scope of this chapter.

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