Extensor apparatus of hand injuries and management

1. ANATOMY OF EXTENSOR APPRATUS
OF HAND AND DEFORMITIES
CAUSED AT VARIOUS LEVELS

2. Extensor apparatus of hand
Extensor apparatus of hand includes :
1. Muscles – Extrinsic / intrinsic
2. Anatomy at the level of wrist
3. Over the dorsum of the hand
4.Over digits
 Variation in anatomy at various levels

3. Extensor apparatus of hand
EXTRINSIC
MUSCLES
PROXIMAL DISTAL
ECU,EDM,EDC
,ECRL,ECRB
APL, EPB,EPL

4. Extensor apparatus of hand
 Intrinsic muscles of hand :
 1.DI
 2.PI
 3.Lumbricles
 Intrinsic muscles contribute to formation of
extensor hood
 Nerve supply :
 DI & PI – Ulnar nerve
 lumbricles

5.  The tendons of the extensor muscles
run under the extensor retinaculum.
 They are separated into six
compartments

7. Extensor apparatus of hand
 Over the dorsum of the hand :
 Juncturae tendinae :
interconnections
between the EDC tendons

8. Extensor apparatus of hand
 Lacerations proximal to the juncturae must
be examined carefully to avoid missing a
tendon laceration.
 The presence of a junctura can provide
weak MP extension of a tendon with a
proximal laceration.
 Weak MP extension by a junctura and
interphalangeal (IP) extension by the
intrinsics lead the examining physician to
conclude incorrectly that the divided EDC
is intact.

10. EIP and EDM
 EIP and EDM tendons are independent
extensors with independent muscle
origins.
 The EIP also lacks a junctura.
 On occasion, the EDM has a junctura
from the ring EDC.

11. EIP and EDM
 These features of independent motor
control make them useful for tendon
transfers.
 The EIP and EDM are both ulnar to the
EDC tendon at the MP joint.
 This anatomic fact makes it easy to
identify the EIP or EDM for a tendon
transfer.

12. Extensor Apparatus Digits

13.  Sagittal bands : At the MCPJ, the
extensor tendon is held in position.
 A sling that arises from the volar plate of
the MCPJ and intermetacarpal
ligaments.

14. Variations in no of tendon slips
 There are variations in the number of
tendons associated with each extensor
muscle .
 This is important to remember in sorting
out extensor tendons lacerated at the wrist
level.
 the fourth compartment is known to contain
four EDC tendons and the single tendon of
the EIP. It can be confusing to find six to
eight divided tendon slips in the
compartment8 rather than the anticipated
five tendons

16. Diagnosis/patient presentation
 Diagnosis of extensor tendon injuries is
often evident.
 As a general rule : open lesions should
therefore be surgically explored to
identify the extent of the injury

17. The function of the EDC tendon should be
assessed by extension of the MP joint of
the affected digit against resistance.
 Partial lesions can be missed if the
remaining tendon is strong enough to
create some extension force .

18.  The EPB tendon inserts into the
extensor tendon apparatus of the thumb
at varying levels and may be able to
extend the IP joint of the thumb.
 If there is a questionable rupture of the
EPL tendon, it should therefore not be
tested by extension of the IP joint.

19.  Instead, the patient should be asked to
lift the thumb off the table, which will be
impossible without an intact EPL tendon

20.  Kleinert and Verdan proposed a system to
classify lesions of the extensor tendon
apparatus into eight zones according to the
level of the lesion.
 Doyle has added a ninth zone by dividing
the forearm into the distal (zone 8) and
proximal forearm (zone 9).

22.  Odd numbered zones are located over
the joints, whereas even numbered
zones are found in between (i.e., zone 1
lies over the DIPJ, zone 3 over the PIPJ,
zone 5 over MCPJ)
 In the thumb, the interphalangeal joint
(IPJ) is zone 1 and MCPJ is zone 3.

23. EXTENSOR TENDON
INJURIES
EXTENSOR
TENDON
INJURY
Acute injury
Chronic
Deformities

24. ZONE I (DISTAL INTERPHALANGEAL JOINT,
THUMB INTERPHALANGEAL JOINT)
 Disruption of the extensor tendon results in
a loss of distal phalangeal extension and a
flexed posture.
 This is called mallet finger, baseball finger,
dropped finger, or extension lag.
 The mechanism of injury is usually forced
flexion of an actively extended distal joint.

25. Injuries over the DIPJ (zone 1 injuries) have been
classified into four types by Doyle

26. Zone 2 Injuries
 Extensor tendon width is greater in zone
II than in zone I.
 The extensor mechanism has two lateral
bands, each of which can extend the
distal phalanx.
 The mechanism envelops a significant
portion of the curving middle phalanx.

27. Zone 2 Injuries
 Consequently, lacerations in this area
are often incomplete divisions of the
tendon and do not result in a mallet
deformity.
 When evaluating these injuries,
phalangeal extension should always be
tested against resistance.

28. Zone 3 Injuries
 The functions of the central tendon and
lateral bands make zone III injuries unique.
 Closed PIP joint injuries : Until the
triangular ligament fibers stretch, the lateral
bands remain dorsal to the PIP and can
extend the joint.
 The inability to completely extend the PIP
joint with the wrist and MP joints in full
flexion is evidence of a central slip
disruption.

29.  Immediately after a central tendon
disruption, the lateral bands, if uninjured,
can remain in a dorsal location and
continue to extend the PIP joint.
 Over time, the triangular ligament may
stretch and the lateral bands shift in a volar
direction. The head of the proximal phalanx
"buttonholes" through the extensor
mechanism, creating the boutonnière
deformity.

30. ZONE IV (PROXIMAL PHALANX, THUMB
METACARPAL)
 The zone IV extensor mechanism is
broad and extends around the sides of
the proximal phalanx .
 A complete tendon division is
uncommon in this location.
 Partial lacerations (<50% of the tendon)
do not require tendon sutures.

31. ZONE IV (PROXIMAL PHALANX, THUMB
METACARPAL)
 Subtotal lacerations (>50% of the
tendon) and complete divisions :
 When evaluating these injuries,
phalangeal extension should always be
tested against resistance.

32. Zone 5 Injuries
 A central tendon laceration can easily be
missed
 The intact portion of the extensor can
provide some MP joint extension, and
the intrinsics extend the IP joints.
 The tendon's continuity is examined by
asking the patient to extend the MP joint
against resistance.

33.  The radial and ulnar sagittal bands centralize
the central tendon over the MP joint by their
attachments to the volar plate.
 A laceration or blunt trauma can disrupt one of
the bands and allow central tendon
subluxation into the contralateral web space.
 The patient complains of a snapping sensation
with MP flexion. On examination, central
tendon subluxation off the metacarpal head is
evident with MP joint flexion.

34. ZONE VI (METACARPAL)
 extensor tendon division in zone VI can
initially be a subtle diagnosis
 Complete laceration of an EDC tendon
in zone 6 may not result in an extensor
lag at the MCPJ because of the
juncturae tendinae that interconnect the
EDC tendons.

35.  It is advisable, therefore, to surgically
explore lacerations on the dorsum of the
hand.
 MP joint extension is checked against
resistance

36. Zone 7 Injuries
 Zone VII injuries occur beneath the
dorsal retinaculum.
 Tendon repair in this area usually
requires opening a portion of the
retinaculum.

37. Zone 8 Injuries
 Lacerations in zones VIII and IX can
divide a combination of tendon, muscle,
and motor nerves
 location of the laceration and the
resultant motor deficit are compared
with the site of motor innervation. This
helps distinguish a motor nerve injury
from a tendon laceration.

38.  The motor branches to the ECRL and ECRB are
proximal to the supinator muscle. Consequently, a
laceration in the distal half of the forearm, with loss
of a wrist extensor, is a musculotendinous rather
than a motor nerve injury.
 Motor branches to the hand extensors occur in two
forearm groups, a proximal-superficial group and a
distal-deep group. The proximal-superficial group
consists of the ECRB, ECRL, EDC, EDM, and
ECU muscles. They originate and receive motor
branches near the lateral epicondyle of the
humerus.

39.  The distal-deep group consists of the
EIP, AbPL, EPB, and EPL. They
originate in the distal half of the forearm,
close to the skeletal plane.
Consequently, a proximal forearm
laceration with loss of distal group
function is probably a motor nerve injury
rather than a tendon division

40. CHRONIC EXTENSOR
TENDON
PROBLEMS Swan neck deformity (SND)
 PIPJ : Synovitis at the PIPJ can cause attenuation of
the volar plate and TRL, which allows dorsal
translation of the lateral band, as well as destruction
of the flexor digitorum superficialis insertion.
 This allows hyperextension of the PIPJ, which in turn
results in increased tension in the flexor digitorum
profundus tendon, as well as loss of tension in the
lateral bands, resulting in DIPJ flexion.
 Over time, adhesions develop and convert this into a
fixed deformity.

41. Swan neck deformity
 MCPJ - Synovitis at the MCPJ can lead
to weakening of the insertion of the long
extensors into the base of the proximal
phalanx, causing the force to be
transmited to the base of the middle
phalanx, resulting in PIPJ
hyperextension.

42. Swan neck deformity
 DIPJ - Rupture of the terminal extensor
tendon, which can occur following
trauma or due to synovitis, allows
proximal migration and relaxation of the
lateral bands.
 Extensor power is then concentrated on
the central slip, resulting in PIPJ
hyperextension and SND as the volar
restraints weaken over time

43. Swan neck deformity
 Wrist - Synovitis at the wrist can result in
carpal collapse, carpal supination, and
ulnar translation. Carpal collapse causes
relative lengthening of both long flexors
and extensors, allowing the intrinsic
muscles to overpower their action and
cause MCPJ flexion and PIPJ extension,
which in time can lead to an SND

44. Swan neck deformity

45. Boutonniere Defonnities
 Boutonniere deformities are
characterized by a flexion deformity of
the PIPJ, with reciprocal extension at
the MCPJ and DIPJ.
 Boutonniere deformities develop due to
pathology at the PIPJ alone, unlike SND

46. Boutonniere Defonnities
 The central slip becomes dysfunctional
 Triangular ligament stretches and allows
the lateral bands to sublux in a volar
direction, maintaining persistent PIPJ
flexion.
 The ruptured central slip also allows the
force from the lumbricals and
interosseous muscles to be transmitted
directly to the distal phalanx, resulting in
DIPJ extension

47. Boutonniere Defonnities

48. THANK YOU