INTRODUCTION — A mallet finger injury is the most common closed tendon injury of the finger. The injury occurs most often in the workplace or during contact or ball-handling sports. It is most common in young to middle-aged males, which may reflect their higher rates of participation in such sports .
The diagnosis and management of mallet finger injuries will be reviewed here. Other finger injuries are discussed elsewhere. (See "Distal phalanx fractures" and "Flexor tendon injury of the distal interphalangeal joint (jersey finger)".)
ANATOMY — Traumatic disruption of the terminal slip of the extensor tendon at the distal interphalangeal (DIP) joint is commonly referred to as a mallet finger (or, less often, as a baseball or drop finger) (figure 1 and figure 2). The terminal slip is formed by the convergence of the extensor lateral bands and inserts on the distal phalanx. It is primarily responsible for extension of the DIP joint. A zone of relative avascularity just proximal to the extensor tendon insertion predisposes the tendon to injury at this site. A more detailed discussion of finger anatomy is found separately. (See "Finger and thumb anatomy".)
MECHANISM OF INJURY — Mallet finger occurs most commonly during collision sports (such as American football and rugby) and ball-handling sports (such as basketball and baseball). The injury is usually caused by a direct blow to the tip of the finger, such as when a ball strikes the fingertip or the fingertip strikes a rigid surface (figure 3). The axial load from the blow causes sudden, forceful flexion of the distal phalanx. This flexion damages the extensor tendon where it attaches to the proximal portion of the distal phalanx. Less frequently, a mallet finger may occur as a result of dorsal lacerations or crushing mechanisms.
With mallet finger injuries, the tendon may be partially torn, completely ruptured, or associated with an avulsion fracture of the distal phalanx. Unopposed flexion leads to a fixed flexion deformity (called extensor lag) at the DIP joint if the injury remains untreated (picture 1).
SYMPTOMS AND EXAMINATION FINDINGS — Mallet finger most often involves the middle finger and, next most often, the ring finger . Patients with a mallet finger complain of pain over the dorsum of the DIP joint. Swelling, ecchymosis, and deformity may be present, especially if there is an avulsion fracture. The most characteristic feature is an inability to extend the DIP joint fully, resulting in a flexed DIP at rest (picture 1).
When evaluating DIP motion, it is important to isolate the function of the extensor tendon by holding the proximal interphalangeal (PIP) joint in full extension (picture 2). This minimizes the contribution of the central slip to DIP extension. With the PIP joint stabilized, test active extension at the DIP joint. The patient with a mallet finger will be unable to extend the distal phalanx actively, but the joint usually can be extended passively.
The degree of DIP angulation often reflects the severity of the tendon disruption. With full tears, there is greater than 30 degrees of extensor lag, and the DIP joint cannot be extended. Partial tears exhibit 5 to 20 degrees of extensor lag along with weak active extension. The development of extensor lag may be delayed by a few hours to a few days after the injury . This delay may contribute to an inaccurate diagnosis at the patient's initial presentation. Inability to fully extend the DIP joint passively suggests bony or soft tissue entrapment and the need for surgical referral [2,3]. (See 'Indications for referral' below.)
As part of the complete examination of an injured digit, the clinician should assess the finger's neurovascular function and inspect the soft tissue for lacerations. The lateral stability of the DIP joint should be evaluated by placing a radial and then ulnar stress on the joint. Comparison with the corresponding finger of the opposite hand can help to determine if laxity is present, which suggests a collateral ligament injury.
DIAGNOSTIC IMAGING — Imaging should be performed on all mallet finger deformities to evaluate for fractures of the distal phalanx and for alignment abnormalities. Radiographs should include anteroposterior (AP), lateral, and oblique views (image 1) .
Avulsion fractures and volar (palmar) subluxation of the distal phalanx are best seen on a true lateral view (image 2). Mallet finger injuries involving fractures of the base of the distal phalanx can be characterized according to the presence or absence of subluxation and the degree of involvement of the articular surface in the DIP fracture .
Clinicians skilled in the use of musculoskeletal ultrasound can use this tool to confirm the diagnosis of mallet finger and evaluate the extent of tendon retraction . Preliminary evidence suggests that ultrasound is an accurate method for diagnosing acute closed mallet finger .
The ultrasound examination should be performed with a high-frequency (14 mHz) L-shaped or "hockey stick" probe (picture 3). More ultrasound gel than is usual should be used to allow for better visualization of the tendon structures. Ultrasound findings for traumatic mallet finger include discontinuity of the extensor tendon with a partial or complete tear, avulsion fracture, the absence of real-time movement of the extensor tendon, and fluid around the insertion of the extensor tendon [4,6]. A retracted tendon end is seen as an irregular, hypoechoic soft tissue lesion over the shaft of the phalanx. If there is an avulsion fracture, ultrasound can reveal the bone fragment at the end of the retracted tendon and loss of substance at the base of the distal phalange .
CLASSIFICATION — There are a number of classification systems used for mallet finger injuries based upon the severity of injury and treatment outcome. The most commonly used system is the following :
●Type 1: Closed or blunt trauma with loss of tendon continuity with or without a small avulsion fracture
●Type 2: Laceration at or proximal to the DIP joint with loss of tendon continuity
●Type 3: Deep abrasion with loss of skin, subcutaneous cover, and tendon substance
●Type 4: Mallet fracture
•4A: Transphyseal fracture in children
•4B: Hyperflexion injury with fracture involving 20 to 50 percent of the articular surface
•4C: Hyperextension injury with fracture involving over 50 percent of the articular surface, and with early or late volar subluxation of the distal phalanx
INDICATIONS FOR REFERRAL — The majority of mallet finger injuries can be managed by primary care clinicians, but more complex injuries warrant evaluation by an orthopedic or hand surgeon [2,9]. Commonly accepted indications for surgical referral include:
●Inability to achieve full passive extension of the DIP joint
●Full laceration of the extensor tendon (as determined by examination or ultrasound)
●Volar (palmar) subluxation of the distal phalanx
●Fracture involving greater than 30 percent of the joint's articular surface
An inability to passively extend the joint suggests the presence of entrapped bony or soft tissue, while volar (palmar) subluxation is associated with worse outcomes. If there is an indication for referral, the patient generally should be seen by the surgeon within 7 to 10 days.
Chronic mallet fingers that fail to improve with splinting may be suitable for surgery. Such patients should be referred to a hand surgeon. (See 'Chronic mallet finger' below.)
COMPLEX MALLET FINGER: SPLINTING OR SURGERY — Mallet fingers that involve large displaced fractures (greater than one-third of the articular surface) or joint displacement have traditionally been thought to lead to permanent deformity and were treated surgically. However, the results of some (primarily observational) studies suggest that nonsurgical treatment may be appropriate in many such cases [10-15]. Suggestive studies include the following:
●One review identified five studies (involving 174 cases) that directly compared nonsurgical with surgical treatment of both bony and soft tissue mallet finger injuries . While two of these studies reported a slight decrease in extensor lag among patients treated surgically, there were no clinically significant differences between groups.
●A randomized trial of 32 patients with bony mallet fractures involving greater than 30 percent of the joint surface without joint subluxation compared immobilization using an aluminum splint versus extension-block pinning for six weeks . At six-month follow-up, there was no difference in extensor lag or patient-reported function and pain scores. The splint group showed better flexion and active range of motion, but three of the patients developed secondary subluxation.
●A retrospective study of 46 patients with mallet finger fractures involving greater than 30 percent of the articular surface compared volar splinting with surgical extension block pinning . Patients with a high degree of subluxation were excluded. All patients had bony union at three months. Important clinical outcomes, including extensor lag, joint motion, patient satisfaction, and nail deformities, did not differ between groups.
●A retrospective study reported comparable results for 22 closed mallet finger fractures involving greater than one-third of the articular surface treated with six weeks of extension splinting or surgical correction . All patients reported minimal functional impairment, and there were no major differences in the assessed outcomes, including residual extensor lag, pain, motion, and satisfaction with finger appearance.
Patient preferences and goals should be considered when deciding whether to perform surgery. Factors to consider include the patient's ability to comply rigorously with conservative therapy, the amount of functional disability present (including the degree of extension loss), and the time since the initial injury. Surgical treatment carries the risk of infection, nail deformities, and a stiff DIP joint but may be necessary for cases that are refractory to splinting (eg, demonstrate persistent extensor lag) or involve swan-neck deformities.
Acute mallet finger
Splinting — The goal of mallet finger treatment is to maximize the function of the DIP joint while minimizing discomfort. The majority of mallet fingers are amenable to treatment with immobilization (ie, splinting), but some complex injuries warrant surgical referral. (See 'Indications for referral' above.)
The general consensus among experts is that uncomplicated mallet finger injuries without DIP joint subluxation are best treated with splinting [10,14,19]. The central slip of the proximal interphalangeal (PIP) joint prevents excessive retraction of the damaged tendon, allowing close approximation and healing of the torn tendon sections to occur with splinting .
Most experts immobilize the DIP joint in full extension or slight hyperextension (5 to 15 degrees) while allowing full range of motion of the PIP joint. Clinical experience and the results of one cadaveric study that assessed the biomechanics of mallet finger injuries support this approach [21,22]. Mallet finger injuries with displaced fracture fragments are not likely to maintain fracture reduction and should be referred. Mallet finger fractures involving greater than 30 percent of the articular surface or with associated joint subluxation should be splinted. In such cases, referral to discuss the relative risks and benefits of nonoperative versus surgical treatment is appropriate.
An aluminum splint can be applied to either the palmar or dorsal surface of the middle and distal phalanx (picture 4). If possible, the splint should be bent slightly to stabilize the DIP joint in 5 to 10 degrees of hyperextension. Hyperextension may be limited initially by swelling or skin tightness. A Stack splint may be used, provided the splint is sufficiently tight to prevent any DIP flexion (picture 5). Custom-made perforated splints similar to Stack splints can be made for fingers that are difficult to fit, and they provide better aeration. An Abouna splint or metal ring splints are generally not used because of patient discomfort.
Care should be taken to avoid direct, sustained pressure from the splint on the area of the DIP joint. Excessive pressure or hyperextension can cause skin necrosis. The Kleinert modified dorsal splint attempts to avoid this complication by removing the middle third of the foam padding from the splint, thereby eliminating all direct pressure at the injury site (picture 6 and picture 7) .
In some instances, a swan-neck deformity (indicating involvement of the central slip) accompanies a mallet finger injury. A swan-neck deformity appears as a hyperextended PIP joint and a flexed DIP joint (figure 4). In such cases, both the DIP and the PIP joints should be immobilized in full extension . Most cases heal well with splinting .
A systematic review identified only four randomized or quasi-randomized placebo-controlled trials, involving a total of 278 patients, that compared treatments for mallet finger . One trial included in the review found no difference in outcomes or complications between fractures treated with splinting versus surgery using wire fixation. Another trial involving anchor suture fixation reported similar results .
To assess if PIP immobilization in flexion allows better approximation of the torn terminal slip, a randomized trial of 44 patients compared immobilization of the DIP only for six weeks with a two-step orthosis treatment . Patients in the intervention (two-step orthosis) group were immobilized in a custom splint with the PIP in 30 degrees of flexion and the DIP in extension for three weeks. They were then switched to a DIP splint for an additional three weeks. At 16 weeks, there was less extensor lag in the two-step orthosis group but no difference in overall pain and function.
Splint selection — Several types of splints can be used to treat mallet finger effectively. We suggest selecting a splint based upon patient comfort in order to maximize compliance, provided the splint is sturdy and ensures adequate immobilization and proper positioning. Proper splint placement and related matters are discussed above. (See 'Splinting' above.)
Two systematic reviews found insufficient evidence to determine the best method for splinting a mallet finger, and the results of two subsequent randomized trials are consistent with this conclusion [10,25]. However, several trials note important differences in outcome depending on the method of immobilization. One review found fewer skin complications with custom orthoses versus prefabricated orthoses but no differences in treatment success, failure, or extensor lag . A randomized trial involving 116 mallet fingers reported that patients with custom-made splints had fewer treatment failures compared with those with Stack splints . In a similar randomized trial involving 64 patients, no significant difference in extensor lag was found among three treatment groups, but patients immobilized in a custom thermoplastic splint experienced no treatment failures while nearly one-fourth of patients immobilized in either a Stack splint or dorsal splint did .
Conversely, several trials have reported that splint type does not affect outcome. A randomized trial involving 60 patients reported that aluminum splints fit better and caused fewer skin-related complications than Stack splints, but both splints were equally effective for enabling tendon healing . Another randomized trial of 77 patients reported no significant difference in extensor lag or complications based upon the type of splint selected . A small study compared casting (QuickCast) with a removable thermoplastic splint and found while cast immobilization led to less edema and improved extensor lag, there were no statistically significant differences in outcome .
Follow-up — DIP joint extension splinting is performed for six to eight weeks. The DIP joint must be maintained in full extension throughout the entire period, including during sleep. Adherence to this instruction is essential. The most common reason for treatment failure is noncompliance. Whenever the splint is removed (eg, to clean the finger or change the splint), the patient must support the distal fingertip in full extension at all times. Should DIP joint extension be lost at any point during the initial treatment period, the treatment clock is reset and an additional six weeks of splinting must be performed. The patient should be seen every one to two weeks to check on compliance and complications.
After six to eight weeks of continuous extension splinting with the DIP joint maintained in full extension, the joint is re-examined and active extension assessed. If the patient is able to achieve full extension, an additional two to four weeks of nighttime splinting is performed.
Splinting should be maintained for all athletic events for another six weeks. If necessary, the foam padding of the aluminum splint may be removed and the aluminum secured directly to the dorsum of the finger to allow the returning athlete to fit the finger into a glove . Active range-of-motion exercises are encouraged in these patients to minimize DIP stiffness.
If a significant extension lag (ie, volar angulation) persists following the initial six weeks of splinting, the splint is reapplied for up to six additional weeks . As with the initial treatment period, the DIP joint must be strictly maintained in full extension throughout the second treatment period. The joint should be reexamined every two weeks during this second treatment period. Once an acceptable outcome is achieved, a night splint is used for two to four additional weeks.
Chronic mallet finger — Chronic mallet fingers are those that go untreated for four weeks or longer. Several small case series suggest that splinting chronic mallet fingers that present within 12 weeks of the initial injury can improve outcomes [20,31,32]. All patients in these studies were treated with a Stack or aluminum splint for 6 to 10 weeks. Extensor lag following treatment averaged 10 degrees.
Treatment of chronic mallet finger consists of DIP extension splinting lasting from 8 to 20 weeks. Patients should be warned about the increased risk of deformity and other complications with delayed presentation and treatment. A successful outcome may be more likely if the injury site appears to be actively inflamed, as suggested by continued swelling, erythema, or tenderness over the DIP joint; and there are no signs of complications, such as scarring or retraction of the tendon. If conservative treatment is unsuccessful, the patient should be referred to a hand surgeon.
Chronic mallet fingers that fail to improve with splinting may be suitable for surgical repair if there is significant residual extensor lag (>30 degrees), joint subluxation, or functional limitation . Such patients should be referred to a hand surgeon.
RETURN TO WORK OR SPORT — Patients with mallet finger injuries may return to sport, provided proper hyperextension is maintained with adequate bracing. However, most contact sports are best avoided in the first six to eight weeks following injury. After the initial six to eight weeks of splinting, an additional six to eight weeks of buddy taping or splinting should be used during athletics. Clinicians must reinforce the importance of strict patient compliance with splinting and the possible long-term complications that will result from noncompliance or returning to play prematurely.
COMPLICATIONS — Compliance with treatment and length of immobilization are important determinants of overall outcome . Complications of mallet finger may result from lack of timely recognition and treatment, which may lead to chronic stiffness and deformity of the DIP joint (picture 1). Complications may also occur as a result of splinting or surgery. Nearly all patients will have a small degree of extensor lag that does not interfere with daily activities.
Most complications from splinting are minor and resolve once treatment is concluded. Such complications include allergic reactions to tape, skin maceration and ulceration, and joint pain . Skin complications can be minimized by avoiding hyperextension that causes pain or skin blanching . Joint pain can be minimized by alternating between dorsal and volar splinting during the six-week treatment period . A small, noticeable lump over the DIP joint may persist for six to eight months following splinting .
A five-year follow-up study of 31 patients treated with splinting for mallet finger found that extensor lag averaged 8 degrees, osteoarthritic changes developed in 11 patients, and a swan-neck deformity occurred in nine patients . Given the high incidence of these complications, patients should be appropriately counseled.
Surgical complications are more complex and more likely to persist. They include infection, nail plate deformity, joint incongruity, osteonecrosis, loss of reduction, hardware failure, and DIP joint deformity . Some complications require further corrective surgery.
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topics (see "Patient education: Hand pain (The Basics)" and "Patient education: Common finger injuries (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Anatomy and injury mechanism – Mallet finger injuries are the result of a partial or complete rupture of the extensor tendon's terminal insertion distal to the distal interphalangeal (DIP) joint. They are caused by forced flexion of the DIP joint. (See 'Anatomy' above and 'Mechanism of injury' above.)
●Physical examination – Examination findings in a mallet finger injury include pain and swelling over the dorsum of the DIP joint, a DIP flexor deformity, and an inability to actively extend the DIP joint (picture 1). (See 'Symptoms and examination findings' above.)
●Indications for surgical referral – Surgical referral should be obtained if the mallet finger is associated with a fracture of greater than one-third of the joint surface, the DIP joint cannot be passively extended, or there is DIP joint subluxation. (See 'Indications for referral' above.)
●Treatment – We suggest that uncomplicated mallet finger injuries be treated by maintaining the DIP joint in full extension or minimal hyperextension using an appropriate splint (Grade 2C). It is crucial that patients not allow flexion of the DIP at any time during the initial period of splinting (generally six to eight weeks). (See 'Treatment' above.)
●Follow-up and return to activity – DIP splinting is performed continuously for six to eight weeks. If no extensor lag exists at the end of this period, night splinting is then performed for two additional weeks. Heavy laborers and athletes should continue to protect the finger with a splint or buddy taping during activity for an additional six to eight weeks. (See 'Return to work or sport' above.)
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