The phalanges and the metacarpals are the most commonly fractured bones in the body.8 Injuries about the distal interphalangeal joint are the most common fractures in the hand.20 Significant dysfunction causing pain, deformity, and stiffness can result in difficulties with activities of daily living and lost time from the workplace.5
The normal and abnormal anatomy of fractures of the distal interphalangeal joint have been outlined by Schneider21; the biomechanics by Brand et al3 and Eaton.7 The distal interphalangeal joint is a stable joint with strong collateral ligaments on either side. The dorsum is stabilized by the extensor tendon and the palmar surface by the flexor profundus insertion. The axis of rotation enjoys a relatively constant center of motion. Because the lever arm of the distal phalanx is short, dislocations are rare.7 The thick posterior portion of the collateral ligament not only stabilizes the joint, but also prevents significant flexion deformity beyond 45 °24 after avulsion of the terminal tendon of the extensor mechanism.
Intraarticular fractures of the distal phalanx occur in 3 primary forms: avulsion of the terminal tendon (mallet finger); avulsion of the flexor digitorum profundus (jersey finger); and in the skeletally immature, an epiphyseal injury, either a Salter-Harris Type I or Type II injury in the prepubescent child (although technically not intraarticular) or a Salter-Harris Type III injury in the adolescent.30
Mallet fingers typically occur after an axial load being applied to the finger, as by a baseball striking the end of a finger, hence the term baseball finger. A classification of mallet finger has been provided by Lange and Engber11 noting that although most are secondary to a sudden flexion of the distal interphalangeal joint, some may be secondary to hyperextension (Fig 1). Doyle6 further classifies mallet finger. Type I: closed or blunt trauma with loss of tendon continuity with or without a small avulsion fracture; Type II: laceration at or proximal to the distal interphalangeal joint with loss of tendon continuity; Type III: deep abrasion with loss of skin, subcutaneous cover, and tendon substance; and Type IV: (A) transepiphyseal plate fracture in children; (B) hyperflexion injury with fracture of articular surface of 20% to 50%; and (C) hyperextension injury with fracture of the articular surface usually greater than 50% and with early or late volar subluxation of the distal phalanx. These latter types often have a large dorsal fragment and an unstable joint that requires operative stabilization. Schneider21 noted that the concept of a hyperextension mallet was actually first described by Böhler1 and Lee.13 Although controversial, Bowers2 and Wehbé and Schneider29 would treat this injury nonoperatively.
Mallet finger injuries occur in 2 forms, soft tissue avulsion and fracture. A soft tissue avulsion can be treated with splinting or casting in a reduced position (Fig 2). This is accomplished by extending the distal interphalangeal joint fully. The joint is hyperextended until blanching of the dorsal skin is noted. When this occurs, the joint is flexed to neutral or until healthy skin color returns. Within 1 week, the splint is changed and the dorsal skin is examined. The patient is taught how to change his or her splint without allowing the distal interphalangeal joint to flex. This usually is done by resting the finger on the edge of a table or other solid structure to maintain full extension while an Alumafoam® (coNco Medical Company, Bridgeport, CT) splint is applied to the dorsum of the finger. Alternatively, a Stack (DePuy, Warsaw, IN) type splint may be slid beneath the finger, again avoiding flexion. The patient is advised that if the finger bends at the distal interphalangeal joint, the 8- to 12-week splinting program must begin again. Between 8 and 10 weeks, when pain is gone and the finger can be held in full active extension, the patient wears the splint at work and at night for 1 week, followed the next week by wearing the splint only at work. If the distal interphalangeal joint begins to droop, the splint is worn at all times for an additional month. The patient is explicitly instructed that the distal interphalangeal joint must not flex at any time during treatment. The authors find this technique works well, except in certain patients in whom the small finger is without flexor digitorium profundus tendon function. These individuals need distal interphalangeal flexion for finger function and are often left with an extensor lag at the distal interphalangeal joint. This is true of noncompliant patients as well, but in these individuals a mallet finger or secondary swan neck deformity is preferable to the complications of mallet finger surgery.28
The second type of mallet finger is a bony avulsion of the terminal extensor tendon. A variable amount of bone and articular surface separates from the phalanx. This may result in subluxation of the remainder of the joint if more than 30% to 40% of the articular surface is involved. An attempt at closed reduction is always warranted.29 If reduction leaves significant displacement, joint incongruity or subluxation, then open reduction and internal fixation should be considered. Closed reduction and percutaneous pinning is also a treatment option provided that the joint is reducible. Operative treatment is through a dorsal H or Y incision. Several techniques have been described, including fixation with a Kirschner wire (K wire),16 tension band wire,10 intramedullary wire,4 external fixator,31 or small lag screw.17 Some authors have recommended releasing the collateral ligament for better joint visualization to ensure anatomic reduction.26 Hamas et al9 recommended dividing the extensor tendon for better exposure.
AUTHORS' PREFERRED TECHNIQUE
Open treatment requires extensive dissection. If certain principles are followed, the fracture may be safely exposed and internally stabilized. An H shaped incision is made with the longitudinal limbs at the midlateral axis of the distal interphalangeal joint.23 This enhances exposure of the fracture and helps preserve blood supply to the dorsal skin. The fracture must be irrigated of debris and hematoma, and then reduced by visualizing the dorsal cortex of the distal phalanx. The extensor tendon should be left intact. If the fragment is large enough to extend beneath the nail bed, the mallet needs to be gently mobilized and retracted with a small periosteal elevator to protect the germinal matrix. Once the fragment is proven reducible, a 0.028 inch K wire is passed retrograde. In cases where the fracture is large, the fragment is reduced and the joint may be held with 1 K wire (kabob technique).14 If the fragment is small, a second K wire is passed directly through the fragment, across the fracture, and into the distal phalanx, holding the fragment reduced. The transarticular pin then is driven from distal to proximal across the joint. It is important that the wire be small in proportion to the fracture fragment to avoid comminution. In the thumb, a 0.35 inch K wire may be appropriate (Fig 3).
The wound is irrigated and closed loosely with 5.0 nylon suture leaving the K wires (here in a finger 0.28 inch wires are used) protruding dorsally and distally (Fig 4). A forearm based splint is converted to a smaller Alumafoam® splint after 1 week allowing proximal interphalangeal joint motion. A splint across the wrist is important early to minimize forces at the distal interphalangeal joint and for comfort. After 6 weeks, when fracture tenderness is gone, the transarticular wire is removed and gentle active distal interphalangeal joint motion is begun. The remaining K wire across the fracture is removed 2 weeks later. The finger is splinted for an additional 4 weeks with a dorsal Alumafoam® or Stack splint, which should be worn at work to prevent reinjury.
Results are good providing that the joint space is anatomic. There is absence of the dorsal prominence that develops when mallet fingers are treated closed. Distal interphalangeal joint flexion may be limited. Surgical reduction techniques are demanding and complications are common,28 including infection, loss of reduction, nail bed abnormalities, and loss of reduction or failure to attain an anatomic reduction.
Given the risks and the demanding nature of the procedure, open treatment should only be considered for patients with joint subluxation and/or in whom near normal function of the distal interphalangeal joint is particularly important, for example, musicians (vocational or avocational).
Closed treatment of mallet fractures may result in a lack of full extension at the distal interphalangeal joint, a more noticeable bump at the site of fracture healing, or even swan neck deformity. Many patients would accept this and function extremely well rather than undergo surgery. Splinting for mallet fractures is the same as for mallet finger although mallet fractures may heal after approximately 6 weeks and therefore the splint may be discontinued sooner.
One final type of mallet finger involves fractures through the physis. This may involve complete displacement of the epiphysis itself, as described by Seymour22 and recently by Schneider,21 or fracture with resultant posture of mallet finger where the epiphysis remains located and the metaphysis is displaced by the pull of the flexor insertion.18 Complete separation of the epiphysis represents a Salter I or II fracture, as does the clinical situation when the epiphysis remains in place, articulating with the middle phalanx, and the metaphysis displaces. Either way the finger will have a typical mallet finger appearance. Often these injuries are open with the potential for nail bed deformity (Fig 5). Treatment usually is accomplished with closed reduction and splinting; however, if the fracture is unstable, K wire fixation may be considered. In the preadolescent, a Salter III fracture may occur when the terminal tendon avulses a segment of the epiphysis. Treatment principles apply as they do in the adult with open treatment of the fracture. When a subungal hematoma is present, DaCruz et al5 noted a high incidence of nail bed deformity by a factor of 4. If nail bed injury is obvious, repair with loupe magnification and 6-0 chromic is recommended. Otherwise, the nail should be left in place as a splint.
AVULSION OF THE PROFUNDUS
Palmar avulsions of the distal phalanx have been categorized by Leddy and Packer12 into 3 varieties. They are caused by forceful passive extension while the flexor digitorum profundus muscle is contracting. A common example is in football when the flexed finger is caught in a jersey while the athlete is attempting to make a tackle, hence the term jersey finger. The defender's finger is being volitionally flexed, while the offensive player's jersey is forcibly extending the defender's finger as he attempts to escape the tackle. The 3 types are as follows: Type I in which the tendon retracts into the palm with or without a bony fragment. Damage to the vascularity of the tendon is severe, both vincula are ruptured. Repair, therefore, should be early because results after 7 to 10 days are difficult owing to contracture. Fortunately this injury is rare. Type II is the most common. The tendon retracts to the proximal interphalangeal joint and the long vinculum remains intact. As in Type I, Type II injuries may have a small bony avulsion; however, they tend to yield better results than Type I injuries. Because the tendon is held out to length, repair can be delayed as long as 3 months without compromising results. Type III injuries involve a large bony fragment. Because of the fragment's size the tendon retracts only to the A4 pulley and both vincula are intact. Rarely, the flexor tendon can be avulsed from the fracture fragment complicating repair.19 This situation has been described and separately classified by Smith25 and Robins and Dobyns19 as Type IIIA. Repair is difficult in both instances and should be performed as soon as possible.
Repair is type specific. In Type I injuries the repair consists of a volar Bruner incision over the palm proximal to the level of the A1 pulley. At this point the flexor tendon is identified and a soft rubber catheter, usually an 8 or 10 French, is attached to the end of the tendon. A separate incision is made obliquely over the distal phalanx and the distal interphalangeal joint exposing the avulsion site. The soft rubber catheter is inserted proximally through the flexor tendon sheath and taken out distally beyond the A4 pulley. A Bunnell suture is placed into the tendon and attached to the bone through the distal phalanx via a pullout wire or prolene suture. Care must be taken at all times to avoid damaging the germinal matrix with the Keith needles (Ethicon J & J Co, Somerville, NJ) and pullout suture. The pins and suture should be coming out through the nail bed beyond the lunula. If there is enough tissue around the insertion site, direct repair with a 4-0 nonreactive suture such as Merselene should be placed around the pullout suture in the tendon to reenforce the repair.
Type II injuries usually retract back to the A2 pulley, with the long vinculum still intact. To find its location, direct pressure over the flexor tendon sheath is applied until the patient feels pain. In some instances, a small lump is palpable at the level of the end of the tendon. A volar Bruner incision is made at this area and a transverse incision just distal to the A2 pulley is made in the tendon sheath. The tendon is delivered through this opening and once again advanced under the retinacular system using a small red rubber catheter. Tendon repair is the same as in Type I injuries with a pullout suture or wire.
Type III injuries involve a large bony fragment. This does not retract beyond the A4 pulley because of the size of the bony fragment. A Bruner incision is made over the distal interphalangeal joint where the tendon and bony fragment are found. The fibrous tissue and clot found in the fracture site is removed. The bony fragment is reduced and if necessary a portion of a collateral ligament released to aid direct visualization of the reduction. The bone is fixed with either a pullout wire, K wires, or a screw. If one is to use a screw, the bony fragment needs to be at least 2 ½ times the size of the diameter of the screw. Radiographs are taken intraoperatively to ensure anatomic alignment of the joint.
Type IIIA injury is a rare variant of Type III. As in Type III a large bone fragment avulses from the distal phalanx. In addition to this, the flexor tendon tears from the avulsed piece of bone. Again direct pressure over the flexor tendon sheath should help locate the proximal extent of the tendon. Repair consists of first reducing and fixing the fracture fragment as described in Type III injuries. Then the flexor tendon is repaired to this fracture fragment with a pullout suture as described in Type I or Type II lesions. Under ideal circumstances, it may be possible to hold both the flexor tendon and fracture fragment with the same pullout suture.
Postoperative treatment is that of a flexor tendon laceration in Zone 1, however, in instances of fracture, motion can be started earlier because of the more rapid healing of bone.
INTRAARTICULAR FRACTURES OF THE MIDDLE PHALANX AT THE DISTAL INTERPHALANGEAL JOINT
Fractures of the middle phalanx involving the distal interphalangeal joint have been classified by London.15 Grade 1 injury is described as an undisplayed unicondylar fracture. This injury tends to be stable. Treatment includes protective splinting for 2 to 3 weeks followed by nonresistive range of motion exercises until fully healed. It is important to follow these injuries closely radiographically because they may displace. Grade 2 injuries involve a displaced intercondylar fracture. Open reduction and internal fixation should be performed. Occasionally, closed reduction and percutaneous pinning may be possible. Generally, however, open reduction through a dorsal incision and fracture fixation with 1 or 2 small (0.35 inch or 0.28 inch) K wires or a minifragment lag screw should be performed. The authors prefer K wires to minimize risks of comminution of the fracture,27 allowing motion in 3 to 4 weeks. Grade 3 injuries are bicondylar or comminuted fractures of the middle phalanx (Fig 6). They result from direct trauma and may have significant soft tissue damage. According to Schneider,21 they often cannot be anatomically reduced. The fragments are very small and do not lend themselves easily to fixation. Rarely a bicondylar fracture can be aligned with 0.028 inch K wires, but stability is marginal at best. Splinting is discontinued in 4 to 6 weeks. If the resultant joint is stiff or painful, fusion is an option.
As with mallet fractures, closed reduction should be attempted. If ankylosis develops but is not painful and if proximal interphalangeal motion is normal or near normal (0 °-90 ° or better), finger function should be satisfactory.
Industrial and power equipment injuries remain a common cause of open injuries to the distal interphalangeal joint. The most severe injury is complete amputation. Replantation may be indicated, usually with primary distal interphalangeal arthrodesis. In complex fracture dislocations of the distal interphalangeal joint with extensive soft tissue injury, a careful assessment of available viable tissue is important. Often a severely damaged finger can be salvaged successfully. Other times, amputation or reconstruction with a cross finger or thenar flap may be considered. Irrigation and debridement usually can be performed with the patient under local anesthesia, followed by percutaneous pinning of fractures and general alignment of the finger tip in cases of severe bone loss. Fusion may be performed at a later date using bone graft if necessary. Herbert screw fixation is ideal for larger fingers. When bone fragments are small, intraosseous wire fixation may be considered.
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