Mallet Finger Treatment & Management

Mallet injuries, whether bony or tendinous, should have closed treatment.^{[2, 3]} This injured area is constrained tightly by adjacent unpadded skin dorsally, a tightly constrained hinge joint volarly, and the germinal matrix of the nail distally. Splinting of the distal interphalangeal joint (DIPJ) in full extension allows for healing of the injured structure and for restoration of excellent function and appearance, as shown below.^[4]

Patient education and compliance are keys to good results. Once extension splinting has been initiated, it should be maintained without even a momentary lapse for the prescribed treatment period. Tendinous injuries require 6-8 weeks of splinting, and bony injuries require 4-5 weeks. The time that is spent educating the patient regarding the necessity for nonstop protection in extension and techniques for maintaining joint extension (even when cleaning the finger and changing the splint) will be rewarded with favorable results.

The DIPJ should be immobilized in full extension so that the finger is straight. Sustained hyperextension of the DIPJ may cause ischemia to the skin over the dorsum of the joint and contribute to the development of pressure sores, as shown in the image below, which are occasionally observed as a result of tight splinting, especially in hyperextension.^[5]

Various means are available for holding the DIPJ in extension. Splinting can be isolated to the distal joint if the PIPJ is not lax and does not hyperextend. Splinting the proximal interphalangeal joint (PIPJ) in partial flexion for the first half of treatment is appropriate if the untreated finger assumes a swan-neck posture.

Small strips of aluminum with foam-rubber backing are commonly used. The foam backing should be of the closed-pore variety so that the foam does not absorb moisture. The open-pore form retains water in its interstices and harbors various microorganisms that hamper proper hygiene. Closed-pore foam aluminum strips are available from various orthopedic supply houses. The aluminum strip can be applied either dorsally or volarly. Applied dorsally, the aluminum strip requires 2 strips of tape — one around the mid portion of the middle phalanx and one around the mid portion of the distal phalanx — for the splint to achieve 3-point fixation and maintain the distal joint in an extended position.

Dorsal splinting allows the digital pulp to be partially exposed for keyboarding and other daily activities. In addition, dorsal splints are more effective at maintaining the joint in full extension. Volar splinting requires only one band of tape around the finger at the level of the distal joint to achieve 3-point fixation. As such, the volar splint and single strip of tape are slightly easier to apply and maintain, but the aluminum precludes any tactile feedback from the digital pulp for light activities.

Other rigid materials can be used for makeshift splints. A large paper clip can be padded with adhesive tape and then used as a splint. Also, some patients have improvised temporary splints with plastic disposable spoons or sections of wooden ice-cream sticks.

Premolded plastic splints are available commercially; however, they often do not fit the finger sufficiently closely to maintain the joint in full extension. These splints have the added disadvantages of entirely covering and blinding the pulp from tactile sensation and preventing evaporation of moisture from the enclosed skin.

Having witnessed the shortcomings of the various splints as noted above, the author devised a simple, custom-molded plastic splint, as shown below. This splint leaves the pulp relatively exposed for functional activities, adheres closely to the contour of the digit without the need for tape, and is of sufficiently low profile to allow for evaporation of moisture from between the splint and the skin. Blanks can be made from various thermoplastic materials that are routinely used by hand therapists or can be purchased commercially. The technique for applying this splint is demonstrated in a short video, below. (Contact George Tiemann & Co [25 Plant Ave, Hauppauge, NY, 11788; phone: 800-843-6266] to request more information or to purchase the Meals Custom Malleable Mallet Mender splint.)

Regardless of the splinting method that is used, patients should have a follow-up appointment 1 week following the initiation of splinting to ensure that the joint is being properly maintained in extension and will continue as such. An adjustment in splint size may be necessary if any surrounding edema has subsided.

At the end of treatment (4-5 wk for bony injuries and 6-8 wk for tendinous injuries), the DIPJ should be stiff in full extension. Full-time splinting in extension for an additional 2-4 weeks is advised if an extensor lag is noted. If no extension lag is present and strength against resistance can be demonstrated, the patient should begin a slow weaning of the splint over the next 1-2 weeks. At that point, the splint should be used for 2-4 more weeks at night and with activities that put the joint at risk. The patient may then resume full activity. Specific finger exercises to regain flexion are very rarely required.

Many surgeons choose to operatively treat mallet injuries that are accompanied by volar subluxation of the distal phalanx; the belief is that restoring joint alignment and the balance between flexor and extensor forces is needed to obtain an adequate functional result in these patients. In general, the joint is reduced and a transarticular Kirschner wire (K-wire) is placed. If the fracture fragment cannot be held in reasonably close approximation to its insertion site, it may be stabilized with another K-wire or a pull-out suture technique.^{[6, 7, 8, 9, 10, 11, 12]}

Occasionally, certain patients (eg, surgeons, dentists) may be unable to wear splints for the required 6-8 weeks for vocational reasons. With a digital block, a .035-inch diameter K-wire can be inserted across the joint to serve as a temporary internal splint. Although the wire may help to maintain the reduction of a bony fragment, its primary purpose is to maintain extension of the joint. It can be difficult to get a K-wire to engage in the distal phalangeal tuft for a retrograde pinning.

Another option is to insert an oblique, antegrade K-wire by starting at the mid portion of the middle phalanx and placing the K-wire obliquely into the main body of the distal phalanx. By starting on the ulnar side of the digit, the wire can be clipped off just below the surface of the skin. The K-wire stabilization should be protected with an external splint when patients are not engaged in critical portions of their occupation. The K-wire can be retrieved and extracted under local anesthesia at the end of treatment.

The most bothersome complication from closed management of a mallet finger is a dorsal pressure sore over the distal interphalangeal joint (DIPJ).^{[2, 5]} This results from excessive pressure of the splint or tape at that site and is probably potentiated by a hyperextension posture of the joint. This is not an instance in which if extension is good, hyperextension is better. Notice that the skin dorsally over the DIPJ blanches when the joint is held in a hyperextended position.^[5]

Complications from open surgical management abound. Often, the small bony fragment is more comminuted than it appears on an x-ray, or it becomes comminuted during the effort at anatomic reduction and internal fixation.^[2] Mobilization of the fragment in an effort to obtain an anatomic reduction can further devitalize the fragment and risk avascular necrosis. Infection, stiffness in extension, nail-bed damage, and chronic tenderness all are well-known problems of open treatment.^[13]

An untreated mallet finger is rarely of functional consequence unless a secondary swan-neck deformity occurs. Even in those cases, patients rarely request surgical reconstruction, choosing instead to "live with it." With this in mind, treatment of a mallet finger should not be worse than the disease. An untreated mallet finger may be of some cosmetic consequence, but a finger of improved appearance with diminished function is not a wonderful outcome.

A functionally and cosmetically normal finger can be obtained with conservative treatment, as long as the patient understands the concept of nonstop extension splinting and is compliant with the care.^[3] It may take several months following completion of splinting for local swelling and erythema to subside, but thereafter, appearance and motion are excellent.

Frequently, a faint residual extension lag is present, in the range of 5-10°, and is observable only on close scrutiny. Beware of the patient with naturally hyperextensible interphalangeal joints. Caution these patients at the outset that the best they can hope for is restoration of extension to neutral. They should not expect the degree of active hyperextension observed in their adjacent digits. This loss of complete extension is of no functional consequence and is of trivial cosmetic consequence.

Although controversy exists regarding whether management of bony mallet injuries should be closed or open, especially when the dorsal avulsion fragment is large and the substance of the distal phalanx is subluxed anteriorly, the literature supports the concept of nonoperative treatment even in these cases.

Better splints may be devised that allow more comfort and function while maintaining the affected distal joint in the necessary extension.