MALLET FINGER

The classic "mallet finger" injury involves the forced flexion of the distal interphalangeal (DIP) joint while the finger is in active extension and results from the disruption in continuity of the extensor tendon over the DIP joint. There are four types of mallet finger injuries, including open and closed forms, and treatment depends on the patient’s age, mechanism of injury, duration of the deformity, associated fractures and presence of osteoarthritis. Chronic mallet finger may lead to swan neck deformity.^1-4  Note mallet finger injuries that are associated with a fracture are reviewed in the diagnostic guide:  Finger Distal Phalanx Fractures - Mallet Finger Fracture section.

Related Anatomy

• Distal phalanx
• DIP joint
• DIP joint collateral ligaments
• DIP joint volar plate
• Terminal extensor tendon
• Intrinsic muscles and lateral bands
• Oblique retinacular ligament

Incidence and Related Conditions

• About 10 new cases per 100,000 per year
• Most common in middle age; more common in men than in women (3:2)
• Most commonly affected digits are the long, ring and small fingers of the dominant hand

Differential Diagnosis

• DIP joint dislocation
• DIP joint fracture/dislocation
• Jersey finger
• Mallet Finger Fracture
• DIP volar plate avulsion fracture

A 60 year old right handed female hit her right ring finger against the bed post while making her bed.  She felt a snapping sensation at the the time of impact. Later, she noted inability to straighten her finger tip.  Pain and swelling around the DIP joint developed during the next 36 hours. Patient was seen at a walk-in clinic where the X-ray was negative. The patient was splinted and referred to a hand surgeon for further care.

RECOMMENDED HAND SURGEON THERAPY ORDERS

• Edema control
• Patient education on prevention
• DIP mild hyperextension splinting for prolonged conservative management.
• Isolated active range of motion exercises, blocking and reverse blocking exercises for PIP
• Post-operative Massage with bacitracin until 48 hours after suture removal, then switch to vitamin E cream
• Tendon gliding exercises when allowed
• Begin strengthening exercises at 10-12 weeks after splinting has been discontinued
• Scar conformer splinting if scar is hypertrophic if applicable
• Progressive PROM stretches when applicable
• Strengthening if needed

REVIEW OF THERAPIST COSERVATIVE INTERVENTIONS FOR MALLET FINGER (ZONE 1 EXTENSOR TENDON INJURY)

Therapy for non-operative patient to include:

Full time splinting of DIP for 6-10 weeks in slight hyperextension or full extension if hyperextension is unobtainable (splinting for 6 weeks and then check for a lag.  If no extension lag at DIP presents, you may order part time splint use and full night time splint use for an additional 4 weeks.  If a slight extension lag persists, resume full time DIP splint use for an additional 4 weeks (total 10 weeks of splinting, day and night).  Night extension splinting can be maintained for a total of 3-4 months if necessary to counterbalance flexion postures during the day.

• Prefab, alumo-foam, or custom splint fabrication by an Occupational Therapist or Physical Therapist / Hand Therapist.  Custom splints may provide more proper fit and comfort, to immobilize DIP, but allow full PIP AROM. (see image below images with finger based splints)
• Patient should return 1x per week for splint checks and skin checks by therapist or surgeon, until week 6.
• Full AROM is initiated during week 1 to encourage PIP and MCP joint gliding.
• At week 6, Gentle AROM for DIP glide within reported pain free range and gradually progress through the next 2-4 weeks. (limit full composite flexion to prevent early overstretching)
• At week 8, initiate Tendon Gliding and Blocking exercises to encourage composite AROM within reported pain free range.

if no lag is present at DIP, otherwise, delay AROM exercises until 10 weeks at DIP. (see image below)

• Encourage towel wringing exercises with warm water to full functional use.
• Take breaks, ice x 10 minutes intermittently throughout the day.
• At 8-10 weeks, gentle PRE’s may be initiated.

REVIEW OF POST OPERATIVE BONY MALLET FINGER REPAIR

Early hand therapist assistance and intervention:

• At week 1, dressing assessment and changing with oil embedded dressings to keep the surgical site and pin site clean and dry.  Check skin for signs of infection and educate patient.
• Edema control – encourage elevation, encourage early gentle finger ROM, watch for RSD/CRPS signs.
• At week 1, referral to an Occupational Therapist or Physical Therapist / Hand Therapist for protective splinting.  Custom splint fabrication may provide the best pin protection from getting banged.
• At week 1, initiate full AROM for the PIP and MCP.
• Very light compressive sleeves for fingers and/or hand.  Be aware of the tourniquet effect causing distal edema accumulation and restricted blood flow to the surgical site.
• Patient education – teach signs of infection, avoid maceration of surgical site, encourage a smoke free recovery, avoid excessive exercise to minimize scarring.
• At week 6, initiate gentle differential tendon glide of the FDS and FDP. Introduce tendon gliding exercises a few times per day to minimize stiffness from the splinting, with intermittent splinting as depicted in the conservative management section.
• At week 7, introduce gentle blocking exercises to improve both PIP and DIP flexion and reverse blocking exercises to improved finger PIP extension (see image)
• At week 8, progress to full unrestricted AROM of fingers, thumb and wrist while encouraging opposition to all fingers as well.
• At week 8-10, initiate light strengthening as tolerated with no pain above a reported 2/10 as they progress (gripper, putty, clips).

When Applicable:

• Scar management, scar massage with vitamin E oil / thick vitamin E cream in light circular motions with moderate pressure, 3-4 minutes twice daily.
• Education the patient to limit strengthening tasks, lifting and heavy use until 9-10 weeks post-op
• Encourage finger food tasks, in hand manipulation and coin stacking, and palm scratch exercises to optimize AROM and function. (when wound is fully healed)
• DIP blocking splint may be required to encourage differential glide of the FDP
• Encourage towel wringing exercises for incorporating fingers and wrist into HEP and functional re-integration.
• When available, find a Certified Hand Therapist to provide splinting

*Wound healing may be prolonged in diabetic patients and smokers

• Skin maceration or marginal skin necrosis
• Recurrent or persistent extension lag 
• Permanent nail deformities
• Transient infections along Kirschner and pull-out steel wires 
• Rarely osteomyelitis of septic DIP joint

• Satisfactory results in 80-95% of cases 32 months after splinting

• Acute traumatic swan-neck deformities must be carefully examined to determine if the deformity is secondary to a mallet finger injury or secondary to a PIP joint volar plate injury or both.
• All potential mallet finger injuries should be X rayed (AP, Lateral & Oblique views) to rule out a mallet fracture and to determine the size and displacement of the fracture fragment.
• Effective splinting of mallet finger injuries requires a reliable conscientious and cooperative patient. Splinting 24 hours per day should continue for six weeks and be followed by 2-6 weeks at night. Protecting the finger with tape during the day for vigorous activity after continuous splinting is advisable.
• Patients must avoid "trying out" active DIP joint extension to avoid disrupting the healing of the terminal extensor tendon during splinting.
• When splinting the DIP joint in extension, avoid excessive hyperextension that causes blanching of the dorsal skin at the DIP joint.
• The PIP joint does not need to be immobilized when splinting a mallet finger or mallet fracture.
• Splinting the DIP joint in neutral extension with a K-wire, left under the pulp skin can be useful if the patient must do activities like surgery. Gas sterilizable thin custom tube splints that should be used under surgical gloves to protect the K-wire from bending.
• Alternating splint types and position on the DIP joint can help to minimize the skin problems associated with prolonged splinting.
• The initial mallet finger extension lag can vary from 5 to 85 degrees. Remember a small amount of extension lag can progress if mallet finger is not splinted.
• Late presentation is not a contraindication to splint treatment.
• Successful splinting outcome for mallet injuries can be expected for most patients, but poor results can occur secondary to poor cooperation and inadequate immobilization.
• Lacerations that cut the terminal extensor tendon can also cause a mallet deformity. These injuries should also be considered an open joint because the capsule and extensor tendon are confluent at the level of the distal DIP joint. These injuries require acute surgical repair.
• There is no agreement on the indications for the surgical treatment of closed soft tissue mallet finger injuries
• Surgical repair of the terminal extensor tendon is frequently unsuccessful because of the thin nature of the tendon and shredding of the injured tendon that can cause sutures to pull out.
• Any surgical procedures should be done with care to avoid damaging the germinal matrix which begins just distal to the insertion of the terminal tendon.
• Surgical repair of the mallet fracture is considered if the dorsal fracture fragment represents 20-30% of the articular surface of the distal phalanx and the joint appears unstable. Surgical repair is indicated if the large distal phalanx fracture fragment is subluxed volar to the head of the middle phalanx.
• Chronic supple mallet fingers with PIP joint hyperextension and DIP extension lags can be treated with the Fowler central slip release technique but the precise procedural details described by Bowers and Hurst must be followed.
• Chronic neglected mallet fractures with large interarticular fragments may require DIP joint arthrodesis.
• In children a transepiphyseal plate fracture (Seymour Fracture) can mimicked a mallet finger injury.

Cited Articles

1. Altan E, Alp NB, Baser R, Yalçın L. Soft-Tissue Mallet Injuries: A Comparison of Early and Delayed Treatment. J Hand Surg Am 2014;39(10):1982-5. PMID: 25194772
2. Lee HJ, Jeon IH, Kim PT, Oh CW. Tension wire fixation for mallet fracture after extension block pinning failed. Arch Orthop Trauma Surg 2014;134(5):741-6. PMID: 24622822
3. Lin JS, Samora JB. Surgical and nonsurgical management of mallet finger: a systematic review. J Hand Surg 2018; 43A(2); 146-163.
4. Suh N, Wilfe SW. Soft tissue mallet finger injuries with delayed treatment. J Hand Surg 2013; 38A: 1803-1805.
5. Bowers WH, Hurst LC. Chronic mallet finger: the use Fowler's central slip release. J Hand Surg 1978; 3A(4): 373-376.

Reviews

1. Cheung JP, Fung B, Ip WY. Review on mallet finger treatment. Hand Surg 2012;17(3):439-47. PMID: 23061962
2. Handoll HH, Vaghela MV. Interventions for treating mallet finger injuries. Cochrane Database Syst Rev2004;(3):CD004574. PMID: 15266538

Classics

1. Abouna JM, Brown H. The treatment of mallet finger. The results in a series of 148 consecutive cases and a review of the literature. Br J Surg 1968;55(9):653-67. PMID: 4877731
2. Pratt DR, Bunnell S, Howard LD Jr. Mallet finger; classification and methods of treatment. Am J Surg1957;93(4):573-8. PMID: 13403090

HAND THERAPY REFERENCES

1. Cannon, et al. (2001).  Diagnosis and Treatment Manual for Physicians and Therapists, Upper extremity Rehabilitation (4^th ed).  The Hand Rehabilitation Center of Indiana.
2. Mackin, Callahan, Skirven, Schneider, and Osterman, (2002). Rehabilitation of the Hand and Upper Extremity, 1, (5^th ed). St Louis, MO: Mosby Year Book, Inc.
3. Cooper, (2014). Fundamentals of Hand Therapy; Clinical Reasoning and Treatment Guidelines for Common Diagnoses of the Upper Extremity, (2^nd ed). Mosby, imprint of Elsevier Inc.
4. Stanley and Tribuzi. (1992).  Concepts in Hand Rehabilitation.  F. A. Davis Company