Mallet finger

Mallet Finger
Muhammad Abdelghani

Finger extensor mechanism anatomy
Lateral view Dorsal view
DIP = distal interphalangeal joint
MCP = metacarpophalangeal joint
ORL = oblique retinacular ligament
PIP = proximal interphalangeal joint
TRL = transverse retinacular ligament.

Anatomy
• The extrinsic extensor tendon:
– Originates in the forearm.
– Courses over the MCP joint.
– Has an indirect attachment to
the proximal phalanx.
• The primary extensor force across
the MCP joint is transmitted
through the sagittal band
connections to the volar plate.
– The tendon trifurcates over the
proximal phalanx.

Anatomy
• Central slip:
– The central continuation of
the extensor tendon.
– Attaches to the dorsal base
of middle phalanx.
– Exerts an extensor force
across the PIP joint.

Anatomy
• Interossei and lumbricals:
– Provide the intrinsic contribution
to extensor mechanism.
– Form a lateral band on each side
of the digit, passing volar to the
MCP joint.
– The lateral bands join with the
lateral slips of the extrinsic
extensor tendon at the level of
PIP joint to form the conjoined
lateral bands.
– The two conjoined lateral bands
then converge dorsally and insert
at the base of the distal phalanx
as the terminal extensor tendon.

Anatomy
• The other components of the extensor
apparatus stabilize the extensor hood and
coordinate joint movement.

Anatomy
• Triangular Ligament:
– A thin tissue connecting the
conjoined lateral bands over the
middle phalanx.
– Prevents separation and volar
migration of the lateral bands when
the PIP joint is flexed.

Anatomy
• Transverse Retinacular Ligaments:
– Originate from each side of the PIP joint volar
plate.
– Insert dorsally into the adjacent conjoined
lateral band.
– Stabilize and limit dorsal migration of the
lateral bands during PIP joint extension.

Anatomy
• Oblique Retinacular Ligaments:
– Arise from the flexor tendon sheath and volar
aspect of the proximal phalanx.
– Course distally to insert onto the dorsal base
of the distal phalanx with the terminal
extensor tendon, thus linking and coordinating
PIP and DIP joint motion.

Mallet Finger
• An injury that
involves disruption of
the extensor
mechanism at the
level of the distal
interphalangeal (DIP)
joint.

Alternative Names
• Baseball finger
• Drop finger

Epidemiology
• Usually occurs in work environment or
during sports participation.
• Most frequently involved digits: long, ring,
and small fingers of the dominant hand.
• Age and Sex:
– Often seen in young to middle-aged males.
– Women with this injury tend to be older.

Genetic Predisposition
• Most mallet fingers are caused by a traumatic
event.
• However, Jones and Peterson found an
unusually high incidence in a three-generation
family, with 85% of the lesions developing
spontaneously or after minimal trauma.
• The authors proposed a possible genetic
predisposition toward mallet finger deformity in
certain individuals.

Mechanism of Injury
• Most common
mechanism:
– Sudden forced flexion of
the extended fingertip.
– This results in either:
• stretching or tearing of
extensor tendon substance
or
• avulsion of tendon insertion
from the dorsum of distal
phalanx, with or without a
fragment of bone.

Mechanism of Injury
• Less frequent mechanism:
– Forced hyperextension of the DIP joint.
– This causes fracture at the dorsal base of the
distal phalanx.
• Open injuries are caused by a laceration,
crush, or deep abrasion.

Pathoanatomy
• A well-balanced system exists
between intrinsic and extrinsic
tendons, and between flexion and
extension forces across each finger
interphalangeal (IP) joint.

Pathoanatomy
• Any injury causing a flexion or extension
deformity in one IP joint can lead to tendon
imbalance, creating an opposite deformity in the
adjacent IP joint.
– At DIP joint: FDP flexion force is counterbalanced by
the terminal extensor tendon.
– At PIP joint: flexion forces of the FDP and FDS
tendons are counterbalanced by the extension forces
of the conjoined lateral bands and the central slip of
extensor apparatus.

Balance between flexion and extension
forces at the finger joints
The single dots represent the axes of flexion-extension
at each joint.
The double dots represent the areas of action of the
corresponding tendons at each joint.

Pathoanatomy
• With a mallet injury, the delicate balance
between flexion and extension forces is
disrupted.
• The following sequence of events occurs:
– Discontinuity of the terminal extensor tendon
– Migration of extensor apparatus proximally
– Increased extensor tone at PIP relative to DIP joint.
– Early or late swan neck deformity (hyperextension
of PIP joint with concomitant flexion of DIP joint) can
occur.

Classification
Acute vs. Chronic
• Acute mallet deformities = those
occurring within 4 weeks of injury.
• Chronic deformities = those presenting
later than 4 weeks from injury.

Classification
Doyle Classification

Classification
Doyle Classification
• Type I: Closed injury, with or
without a small avulsion fracture
at the dorsal base of distal
phalanx.
• Type II: open tendon injuries
caused by laceration at or around
the DIP joint.
• Type III: also open injuries; they
occur from a deep soft-tissue
abrasion with loss of skin and
tendon substance.
• Type IV: mallet fractures

Classification
Subclassifications of Type IV Injuries
• Damron & Engber:
– IVA: Distal phalanx physeal injuries in children.
– IVB: Distal phalanx fractures in adults involving 20%-
50% of the joint surface.
– IVC:
• Hyperextension injuries, resulting in a fracture fragment
>50% of the distal phalanx articular surface.
• Associated with DIP joint volar subluxation.
• Wehbé & Schneider:
– Subclassification based on fracture size and presence
or absence of DIP joint subluxation.

Clinical Evaluation
• Recognition and diagnosis of a mallet
finger are relatively straightforward.
• Patients present with pain, deformity,
and/or difficulty using the affected finger.

Clinical Evaluation
• Inspection:
– Soft tissues
– Deformity:
• Most patients develop an extensor lag
at the DIP joint immediately after injury.
• The deformity may be delayed by a few
hours or even days.
• Concurrent hyperextension of the PIP
joint (ie, swan neck posture) may be
noted with active finger extension.

Clinical Evaluation
• Palpation:
– Tenderness can be elicited in acute injuries
with palpation over the dorsal margin of DIP
joint.
• ROM:
– Measure finger MCP and PIP joint motion.

Radiographic Evaluation
• Posteroanterior, oblique, and
lateral radiographs of the digit
are recommended to assess
for bone injury and joint
alignment.

Neglected Injuries
• Neglecting mallet injury often results in
permanent stiffness and deformity at the
DIP joint level.

Treatment Options
• Non-surgical:
–Successful in most mallet injuries.
• Surgical:
–Treatment of either an acute or a
chronic mallet finger
–Salvage of failed prior treatment

Treatment Options
• Many splint configurations and surgical
techniques have been described over the
last century.
• However, the optimal treatment of each
type of mallet finger injury remains
controversial.

Definition of satisfactory outcome
(Geyman et al.)
• DIP joint exhibits a residual extensor lag
≤20°
• DIP flexion arc is ≥50°
• Patient reports minimal or no pain.

Management of Acute Mallet Finger Injuries
Nonsurgical
• Indications:
–Type I mallet injuries
– Closed mallet fractures involving less
than one third of the articular surface
with no associated DIP joint subluxation.

Nonsurgical
• Outcome:
– About 80% of closed injuries will heal with 6
(tendinous)—8 (bony) weeks of splintage with a
further 2 weeks at night.
– If the tendon does not heal within this period of time
further splintage can be successful.
– If this fails, open repair may be considered.
– Controversy exist regarding:
• style of splint
• duration of immobilization necessary for acceptable outcome

Nonsurgical
• Immobilization of both PIP and
DIP joints was previously
thought to be necessary to
relax the extensor hood and
intrinsic musculature during
terminal extensor tendon
healing.
• However, Katzman et al
demonstrated that only the DIP
joint need be immobilized in
extension to allow healing of
the mallet injury.

Nonsurgical
• Most authors currently advocate
immobilization of the DIP joint alone.
• In the presence of a swan neck
deformity, however, temporary
inclusion of the PIP joint in flexion
has been suggested.
• Combined PIP and DIP joint splinting
has not been conclusively proved to
restore tendon balance in a swan
neck deformity.

Nonsurgical
Splinting
• Numerous splints have
been devised for managing
mallet finger injuries.
• Common examples:
– The stack splint
– The perforated thermoplastic
splint
– The aluminum foam splint

Three different mallet finger splints
A, Stack splint (Stax Finger Splint, Sammons Preston Rolyan, Bolingbrook, IL)
B, Perforated thermoplastic splint (Aquaplast Splinting Material, Sammons Preston
Rolyan)
C, Aluminum foam splint

Nonsurgical
Splinting
• ‘Mexican hat’ splint:
– Incorporates a “buckle” over the DIP joint to
alleviate undue pressure on the healing
terminal extensor tendon.
• A sterilized aluminum splint secured with
sterile tape strips has been proposed to
treat mallet injuries in operating room
personnel.

Nonsurgical
Splinting
• Many splints, same treatment
principles:
– The digit is immobilized in full extension
or slight hyperextension across the DIP
joint.
– Avoid excessive extension because
dorsal skin vascular compromise can
occur when the joint is immobilized in >
50% of the normal range for passive DIP
joint hyperextension.

Nonsurgical
Splinting
• Instruct the patient on how to change the
splint for periodic cleaning and
examination of the skin without allowing
the DIP joint to flex.
– Continuous immobilization: 6-8 weeks.
– Nighttime splinting: 2 weeks.
• A new full-length course of immobilization
is recommended when the DIP joint is
inadvertently flexed during treatment.

Nonsurgical
Splinting
• Requirements for
successful splinting:
– Frequent physician
assessment (check films in
the splint over the first 2
weeks)
– Patient compliance

Nonsurgical
Splinting
• A small residual extensor lag and
radiographic evidence of DIP joint
osteoarthritis do not preclude a successful
treatment result.

Nonsurgical
Casting
• Infrequently used technique.
• May be beneficial in:
– Children
– patients deemed noncompliant with splint treatment
• Described by Smillie (1937) for acute mallet
finger injuries.
• Both IP joints are casted:
– PIP joint in 60° of flexion
– DIP joint in slight hyperextension
• Inclusion of PIP joint in flexion prevents a tubular
cast from inadvertently falling off the finger.

Surgical
Type I Injury
• Splinting is the treatment of choice.
• Surgical indications:
– Individuals unable to comply with a splinting
regimen
– Patients who would have difficulty performing
their jobs with an external splint (eg,
surgeons, dentists, musicians).

Surgical
Type I Injury
• To immobilize the DIP joint in
extension, a transarticular K-wire
is driven longitudinally or
obliquely across the DIP joint.
– The tip of the wire is buried in the
middle phalanx.
– The distal end is either capped or
cut beneath the skin surface.
• Post-Operatively:
– K-wire is removed after 6-8 weeks.
– This is followed by 2 weeks of
nighttime extension splinting.

Surgical
Open Injuries (Types II and III)
• Open mallet injuries require surgical
repair.
• Various surgical methods have been
described.

Surgical
• The tendon can be repaired separately from the
skin.
• However, as there is little subcutaneous tissue:
– The repair material may be superficial
– Successful results have been achieved with a mass
repair of tendon and skin.
• A K-wire through the DIP joint is useful to
stabilise the repair while the tendon heals.
• If the tendon ends are damaged a turndown of
one lateral band can be used to strengthen the
repair.
– This method may also be useful for chronic mallet
injuries.

Surgical
• Doyle:
– A combination of surgical repair and splinting
for acute tendon lacerations overlying the DIP
joint.
– A running suture is used to reapproximate
both skin and tendon, followed by application
of an extension splint.
– The suture is removed after 10-12 days.
– Splinting is continued for 6 weeks.

Surgical
• Type III mallet deformities:
– Involve loss of skin, subcutaneous tissues, and
tendon substance.
– Caused by deep abrasions, crush injuries, and
degloving accidents.
– Often difficult to treat because of exposure of both
bone and articular cartilage.
– Staged reconstructive surgery may be considered:
• Early skin coverage is followed by restoration of extensor
tendon function with insertion of a free tendon graft.
– In severe cases, DIP arthrodesis with bone shortening
or fingertip amputation may be more appropriate.

Surgical
Mallet Fracture (Type IV)
• Management strategies for the different
subtypes of mallet fractures remain
controversial.
• Treatment alternatives:
– Observation with reassurance
– Extension splinting
– Closed and open reduction with internal
fixation
– DIP joint arthrodesis.

Surgical
• A true lateral radiograph of the injured digit is valuable
for determining:
– size and displacement of fracture fragment
– presence or absence of volar subluxation of the distal phalanx.
• Closed mallet fracture injuries involving less than one
third of the articular surface and without DIP joint
subluxation can be reliably treated with extension
splinting alone.
• Wehbé & Schneider and Schneider advocated
nonsurgical management of nearly all mallet fractures,
regardless of the size or displacement of the fracture
fragment or the presence of volar subluxation of the
distal phalanx.

Calculations for determining fracture fragment size, fragment
displacement, and distal interphalangeal joint subluxation.
A and B = the length of the involved bone segments at the articular surface of
the distal phalanx, C = the amount of fracture fragment displacement, D = the
distance between the midaxial lines of the middle and distal phalanges.

Surgical
• Disadvantages of surgical treatment of
mallet fractures:
– Technically demanding
– Higher complication rate than nonsurgical
management
• A dorsal prominence overlying the DIP
joint may follow nonsurgical treatment.
– This same deformity is seen in the surgically
treated patients.

Lateral radiograph of a remodeled
mallet fracture
The arrows indicate the old fracture line.
The distal interphalangeal joint remains congruent.

Surgical
• Indications for surgical intervention:
–Mallet fractures involving more than one
third of articular surface
– Fractures with associated DIP joint
subluxation

Surgical
• Techniques:
– Transarticular pinning of DIP joint ±
fracture fragment fixation
– Tension band constructs
– Compression pinning
– Extension block pinning
• All of these techniques involve
placement of at least one K-wire to
immobilize the DIP joint in
extension.

Extension
block pinning
technique
A, With the distal phalanx
extended, a K-wire is
inserted proximal to the
fractured fragment.
B, The fracture is reduced
manually by directing the
exposed end of the K-wire
distally.
C, The wire is drilled into
the head of the middle
phalanx, and a second wire
is passed retrograde
across the distal
interphalangeal joint.

Surgical
• Open vs. Closed Reduction:
– Proponents of open reduction think that associated
complications can be minimized by using meticulous
surgical technique.
– Closed reduction with percutaneous pinning has been
advocated by surgeons who are concerned about
complications with open management.
– They cite problems related to reducing the small
articular fragment, the inability to accurately assess
DIP joint congruency, and the potential for injury to
the tenuous soft-tissue envelope.

Management of Chronic Mallet Finger
Injuries
• Patients who present for treatment > 4
weeks after injury typically report pain,
dissatisfaction with the appearance of the
digit, and interference with use of the
finger for normal work and recreational
activities.
• As with acute mallet injuries, both
nonsurgical and surgical treatment
measures have been advocated.

Management of Chronic Mallet Finger Injuries
Nonsurgical
• Continuous extension splinting (10 weeks)
should be considered as an alternative to
surgery for a chronic mallet finger
deformity (Patel et al., 1986).

Nonsurgical
• Garberman et al found no differences in
outcome between patients splinted early (<2
weeks after injury) and late (>4 weeks after
injury).
• They recommended DIP joint extension splinting
for closed mallet injuries regardless of chronicity,
including fractures involving less than one third
of the joint surface.
• Brzezienski and Schneider advocated splinting
for all chronic mallet deformities resulting from
either neglect or previous failed treatment.

Surgical
• Rationale of surgery:
– Chronic mallet finger may develop pathologic
features that interfere with treatment results.
– A static contracture of the extensor
mechanism can develop over time, making it
difficult to achieve apposition of the tendon
ends with simple extension splinting.

Surgical
Surgical procedures for chronic mallet finger:
• Aims:
– to stabilize the DIP joint
– to improve active DIP joint extension.
• Examples:
– Terminal extensor tendon shortening
– Tenodermodesis
– Oblique retinacular ligament reconstruction
– Fowler’s central slip tenotomy

Surgical
• The abbreviato operation (Lind & Hansen, 1989):
– The extensor tendon is transected near the DIP joint
and repaired directly, without overlapping and without
excision of damaged tendon tissue.
– Scar contraction at the repair site is thought to correct
the flexion deformity.
– A transarticular pin is used to immobilize the DIP joint
in extension for 6 weeks.
– Timing:
• The authors recommended performing the procedure within
3 months of injury in patients with marked ligamentous laxity
to avoid progression to a swan neck deformity.
• However, the procedure is not recommended before 6
months to allow potential spontaneous correction of the
extensor lag.

Surgical
• Tenodermodesis:
– Originally described by Iselin et al.
– Used to manage chronic mallet finger
deformities in both adults and
children.
– Technique:
• An elliptical wedge of skin, tendon, and
scar tissue is resected.
• The skin and tendon are reapproximated
as a single unit with sutures.
• Similar to the abbreviato operation, a
temporary K-wire is used to maintain the
DIP joint in full extension during the
healing process.

Tenodermodesis Procedure
In the tenodermodesis
procedure, a 3- to 4-
mm elliptical wedge of
skin, subcutaneous
tissue, and tendon/scar
is resected.
A, The full-thickness
defect is repaired with
nonabsorbable sutures.
B, Before securing the
sutures, the distal
interphalangeal joint is
immobilized in
extension with a
Kirschner wire.

Surgical
• Spiral Oblique Retinacular Ligament Reconstruction:
– Originally reported by Thompson et al; later modified by
Kleinman and Petersen.
– Addresses the imbalance of flexion and extension forces
contributing to a chronic mallet deformity.
– Restores the dynamic tenodesis effect of the oblique retinacular
ligaments in coordinating PIP and DIP joint extension.
– A free tendon graft is harvested and secured distally to the
dorsal base of distal phalanx.
– The graft is passed volarward in a spiral fashion around the
radial aspect of the middle phalanx and is secured proximally to
the ulnar side of the flexor tendon sheath at the level of the
proximal phalanx or directly to bone.
– The PIP and DIP joints are temporarily immobilized with K-wires
before initiating finger motion exercises.

Spiral oblique retinacular ligament reconstruction
A, Lateral view. The tendon graft is secured to the dorsum of the distal phalanx with a
pullout suture or wire. The graft is passed along the radial border of the middle phalanx,
deep to the neurovascular bundle and volar to the flexor tendon sheath.
B, Volar view. The graft is then sutured to the ulnar edge of the flexor tendon sheath at
the level of the proximal phalanx.

Surgical
• Fowler’s Central Slip Tenotomy:
– Aim: To correct for increased extensor tone at the PIP
joint resulting from retraction of the extensor
apparatus.
– Timing:
• The operation should be delayed until at least 3 months after
injury to allow restoration of terminal extensor tendon
continuity by scar tissue (Houpt et al, 1993).
– To prevent boutonnière deformity, the triangular
ligament bridging the two conjoined lateral bands
must be preserved when cutting the extensor
mechanism.
– Unlike the other corrective procedures, active finger
motion is permitted immediately after surgery.

Dorsal (A) and lateral (B) views of
Fowler’s central slip tenotomy. The
central slip is transected immediately
proximal to its insertion on the base of
the middle phalanx. The lateral bands
and triangular ligament are preserved.

Surgical
• DIP Joint Arthrodesis:
– Indications: Salvage procedure for patients with
painful mallet finger injuries secondary to arthritis,
deformity, infection, and/or failed prior surgery.
– Can be effectively performed with K-wires, tension
band wiring, or IM screw fixation.
– Position of fusion: between neutral and 10° of flexion.
– Advantages of arthrodesis:
• Reliable pain relief
• Early PIP joint finger motion

Posteroanterior (A)
and lateral (B)
radiographs of a DIP
joint arthrodesis.
Fixation was achieved
with a headless
differential-pitch
compression screw.

Complications
• Complication rates:
– In digits treated with extension splinting: 45%
– In digits treated surgically: 53%.

Complications
• Complications associated with splinting:
– Most are transient.
– Most resolve with adjustment of the splint or
after completion of treatment.
– Complications include:
• Skin maceration and ulceration
• Tape allergy
• Transverse nail plate grooves
• Splint-related pain

Complications
• Complications associated with surgical
treatment:
– 76% are long-term complications.
– Reported problems include:
• Infection
• Nail plate deformity
• Joint incongruity
• Hardware failure
• DIP joint prominence
• DIP joint deformity

Mallet Thumb
• Unlike mallet finger, avulsion of
the extensor pollicis longus
(EPL) tendon at its distal
insertion (mallet thumb) is rare.
• Although the recommended
treatment for closed mallet
finger is conservative, some
authors proposed operative
treatment for mallet thumb.

References
• Bendre AA, Hartigan BJ, Kalainov DM: Mallet
Finger. J Am Acad Orthop Surg 2005;13:336-
344
• Dean BJF, Little C: Fractures of the
metacarpals and phalanges. Orthopaedics &
Trauma 2011; 25(1):43-56
• De Smet L, van Ransbeeck H: Mallet Thumb.
Acta Orthopædica Belgica 2003; 69(1): 77-78
• Rust PA, Eckersley R: Twenty questions on
tendon injuries in the hand. Current
Orthopaedics (2008) 22, 17–24

Mallet finger

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