The document provides an overview of the anatomy and function of the forearm's extensor tendons, detailing their compartments, common injuries, and specific clinical tests for thumb and finger extension. It discusses the types of extensor tendon injuries, classifications, surgical repair techniques, and rehabilitation protocols for optimal recovery. Key complications and treatment methodologies for conditions like mallet finger and boutonniere deformity are also outlined.

1. Ismaeel Al-Saadi Hospital
Orthopedic Surgery Department

2. The forearm consists of many compartment:
- Anterior: contains flexor muscles.
- lateral: considered as part of posterior compartment which
consists of (Brachioradialis and extensor carpi radialis
Longus)
- Posterior: consists of two groups of muscles (superficial
an deep group)
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5. Notice:
- The four tendons of the extensor digitorum emerge from
under the extensor retinaculum and fan out over the
dorsum of the hand.
- Strong oblique fibrous bands connect the tendons to the
little, ring, and middle fingers.
- The tendon to the index finger is joined on its medial side
by the tendon of the extensor indicis, which is the same for
little finger.
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6. - On the posterior surface of each finger, the extensor
tendon joins the fascial expansion called the (extensor
Expansion).
- Near the proximal interphalangeal joint, the extensor
expansion splits into three parts:
- Central part, which is inserted into the base of the
middle phalanx.
- Two lateral parts, which converge to be inserted into
the base of the distal phalanx.
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13. It’s a thickening of deep fascia that stretches across the
back of the wrist and holds the long extensor tendons in
position, It converts the grooves on the posterior surface of
the distal ends of the radius and ulna into six separate
tunnels ( 6 Compartments) lined with a synovial sheath.
It’s attached medially to the pisiform bone and the hook of
the hamate and laterally to the distal end of the radius.
Extensor Retinaculum
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14. The 6 Compartments contents are (from lateral to medial):
1- abductor pollicis longus , extensor pollicis brevis
and to the medial, there is the radial artery.
2- extensor carpi radialis longus and brevis.
3- extensor pollicis longus.
4- extensor digitorum and extensor indicis above it.
5- extensor digiti minimi.
6- extensor carpi ulnaris.
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17. - Extensor tendon injuries are more frequent than flexor
tendon injuries. and are very common (61%) as they
are not protected as well as the flexor tendons due to:
- their superficial location
- and lack of overlying subcutaneous tissue.
- Extensors are particularly difficult for surgeons because of:
- their reduced size compared with the flexors
- and their lack of collagen-bundle linkage, which reduces the
grip strength available for the suture material.
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18. - Extensor digiti minimi is responsible for extension of the fifth digit. It
can be tested by asking the patient to lie their hand flat on a surface
and hyperextend the fifth digit.
- The extensor digitorum tendons extend digits two through five. The
hand can be laid flat again on a surface and the tendon of each
finger tested by having the patient hyperextend the digits against
resistance.
- Extension of the second finger is also performed by extensor
indicis, which can be tested in a similar fashion to extensor
digiti minimi.
- Extension of the first digit is controlled by two muscles, extensor
pollicis longus and brevis.
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19. - Extension of the thumb at the interphalangeal joint and the
metacarpophalangeal joint can be tested separately against
Resistance
- When checking the long extensor tendon of the thumb, the
examiner must stabilize the metacarpophalangeal joint and
must test carefully for active extension of the interphalangeal
joint and active retropulsion of the thumb toward the dorsum of
the hand, because an intact short thumb extensor can actively
extend the thumb.
- Radiographs are needed to assess any associated
fracture as they will need to be fixed before tendon and
nerve injuries during surgery
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22. - Kleinert and Verdan wrote a classification system for
extensor tendon lacerations according to the eight zones of
the hand, wrist and forearm which has been widely accepted.
- The type of injury, surgical approach, potential deformity
varies according to the zone.
- Zone I refers to the area from the DIP joint to the fingertip;
zone II encompasses the middle phalanx;
zone III refers to the PIP joint;
zone IV is over the proximal phalanx;
zone V refers to the MP joint;
zone VI encompasses the metacarpal and
zone VII is over the wrist
zone VIII refers to the forearm.01،‫نيسان‬16

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24. Extensor Tendon Suture Methods:
– For more distal injuries (zones 1-4) the tendon is flat:
Figure of 8 repair or mattress suture repair
–As the caliber thickens (zones 5-8):
Core suture method
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25. - Rockwell et al Explained that treatment of tendon injuries is
dependent on the location and type of injury. Repair should
take place very soon after the injury especially within the first 2
weeks.
- Extensor tendon repair techniques are not as complicated
as flexor tendon repairs, this is due to the:
- extensor tendon being smaller with a relatively flat
cross section.
- its collagen is longitudinally orientated with little or
no cross-linking.
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26. - Exploration of the wound will often occur with the patient
awake (local or regional anaesthetic),
- but more complex injuries would be explored whilst the
patient is asleep (general anaesthetic).
- The surgeon will apply a tourniquet to the limb to prevent
bleeding, which makes the operation much easier.
- It is likely that the wound will be made larger by the
surgeon to enable a thorough inspection of the structures in
the vicinity as well as to retrieve tendon ends that tend to
spring apart when cut.
- The hand/wrist is almost always protected by a splint to
prevent the tendon repair being over-stretched
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29. - Zone I injury often referred to as mallet finger is when
there is disruption to the extensor tendon over the distal
interphalangeal joint causing a flexion deformity of the distal
interphalangeal joint.
- It’s caused by Forceful flexion of the distal interphalangeal
joint in an extended digit, results in rupture of the extensor
tendon or avulsion from its insertion at the distal phalanx.
- When left untreated, hyperextension of the proximal
interphalangeal joint may develop due to the retraction of the
central band causing a swan neck deformity.
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32. Mallet fingers are classified into 4 types:
Type 1: Closed with or without avulsion fracture
Type 2: Laceration at or proximal to the distal interphalangeal
joint with loss of tendon continuity
Type 3: Deep abrasion with loss of skin, subcutaneous
cover, and tendon substance
Type 4: A- Transepiphyseal plate fracture in children.
B- hyperflexion injury with fracture of the articular
surface of 20 to 50 percent.
C- hyperextension injury with fracture of the articular
surface usually greater than 50 percent and with
early or late palmar subluxation of the distal phalanx.
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33. - Closed mallet fingers, which is type I fractures should be
treated with an immobilisation splint in extension or slight
hyperextension for 6 to 8 weeks and at night only for 1 additional
week.
- After 8 weeks the fingers should be examined again and if active
extension is present splinting can be reduced to high-risk times such
as sleeping, manual work or athletic performance.
- Type II required simple suture through the tendon alone or a roll
type suture (tenodermodesis technique) incorporating the tendon
and skin in the same suture and then splinting for 6-8 weeks.
- Type III fractures include loss of tendon substance which requires
immediate soft tissue coverage and primary grafting or
reconstruction with free tendon graft.
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34. - Type IV-A are best treated with closed reduction followed by
splinting and are the most likely fracture in children.
- Type IV-B is usually treated by splinting for 6 weeks with 2 weeks
of night splinting yields good results.
- Type IV-C with palmar subluxation of the distal phalanx is surgically
managed with open reduction and internal fixation using a Kirschner
wire and sometimes a pull-out wire or suture.
A splint for 6 weeks is then used after which the Kirschner wire is
removed and motion started.
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35. - Repair the extensor tendon with 4-0 monofilament nylon or 4-0
monofilament wire as a pull-out roll stitch.
- Close the skin with interrupted 5-0 nylon. As an alternative,
use 4-0 nylon as a dermotenodermal suture.
- The sutures are removed at 10 to 14 days.
The Kirschner wire is removed after 4 to 6 weeks.
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40. - Zone II injures or middle phalanx injuries are usually as a
result of laceration or crush injuries rather than avulsion like
zone I.
- If there is extensor lag on examination then exploration and
repair is needed, whereas if there active extension with only a
degree of weakness than splinting can be used for 3-4 weeks.
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41. - According to experimental work by Newport et al. and
Newport and Williams, the Kleinert modification of the Bunnell
suture and the modified Kessler sutures were stronger than a
figure-of-eight or mattress suture for repair of extensor tendons
in zone II.
- Injuries greater than 50% of the tendon should be repaired
with a fashion-of eight suture or similar fashion.
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45. - Known as Boutonniere Deformity is caused by disruption
of the central slip at the proximal interphalangeal joint.
- The boutonniere deformity usually occurs 10-14 days
after the first injury.
- Closed deformities require splinting for 4-6 weeks of the
PIP joint in extension with the DIP joint and wrist joints left
free.
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49. - Surgery should be considered for closed fractures when:
1- displaced avulsion fractures at the base of the middle
Phalanx.
2- axial and lateral instability of the PIPJ associated
with loss of active or passive extension of the joint.
3- failed non-operative treatment.
- The central tendon is repaired by a modified Bunnell or Kessler
technique. These techniques have been shown to be the strongest
and most biomechanically advantageous for extensor repair .
- The suture should secure the tendon to the middle phalanx with or
without the bony fragment.
- Kirschener wire fixation of the proximal interphalangeal joint is
maintained for 10 to 14 days, followed by an extension splint until
union.
- For open injuries, surgical repair might not be required if splinting is
used as the tendon may come together.01،‫نيسان‬16

50. - known as proximal phalanx injuries, usually involve the broad
extensor mechanism, it’s diagnosed usually by inspection.
- Splinting the PIPJ in extension for 3-4 weeks without repair as
shown to have the same outcome as repairing it with nonabsorbale
sutures.
- However, if the laceration is complete, surgical primary repair
should be performed followed by 6 weeks of splinting in extension.
- In the first 3 weeks volar positioning should be used with passive
extension allowed.
At week 4 gentle active extension is introduced but no passive
flexion at this time.
In the last two weeks active flexion is introduced and graded
resisted exercises are implemented.01،‫نيسان‬16

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52. - Injuries in zone V are nearly always open.
- It should be repaired with the modified Bunnell repair
technique because this technique has been shown to be the
best repair method.
- The saggital bands should be repaired in a simple or
mattress fashion to prevent lateral migration of the extensor
digtorum communis tendon and subsequent
metacarpophalangeal extension loss.
- Splinting of the wrist in 30-45 degrees of extension and the
metacarpophalangeal joint in 20-30 degrees of flexion is
performed with the proximal interphalangeal joint free.
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54. - It occurs most commonly in the long finger.
- The dislocation usually occurs as a result of a tear in the
proximal radial portion of the shroud ligament (sagittal bands)
and the more proximal fascia, as the finger is suddenly extended
against a force, as in a flicking or thumping motion.
- If seen within the first few days, this dislocation can be treated
effectively with splinting of the metacarpophalangeal joint and
wrist in extension for about 3 to 4 weeks, followed by 3 to 4
weeks of removable splinting or buddy taping to the adjacent
finger on the radial side in the case of ulnar displacement.
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58. - The tendons in this area are close to the thin subcutaneous
tissue. Injuries in this zone are situated in the dorsal hand and may
not always result in loss of the extension at the
metacarpophalangeal joint.
- Surgical repair is needed with stronger core type sutures and then
splinting should be placed in extension for 4-6 weeks.
- If the extensor digitorum communis is involved, all fingers should
be splinted but if the proprius tendon is solely involved, only the
affected finger need be splinted with the wrist.
- As the tendons in this area are larger, stronger core suture should
be used.
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60. - In the dorsal forearm, many tendons are likely to be
lacerated, including the muscletendious junction and tendon
bellies.
- Thumb and wrist extension should be repaired first.
- Multiple figure of eight sutures should be used to repair
the muscle bellies.
- Static immobilisation of the wrist in 45 degrees of extension
and metacarpophalangeal joints in 15-20 degrees should be
maintained for 4-5 weeks
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61. - Mallet injuries are uncommon in the thumb because the
terminal extensor tendon is thicker on the thumb.
- Open injuries most surgeons would recommend primary
repair with splinting for 6 weeks. For closed injuries
splinting for 6 weeks (8 weeks: Campbells) without surgical
repair is a suitable alternative but surgical repair is also used.
- Extensor pollicis brevis is rare to be solely lacerated, so
its repair is debatable because extension of the
metacarpophalangeal joint is possible with an intact extensor
pollicis longus.
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62. - Splinting is usually for 3 to 4 weeks, with the thumb
metacarpophalangeal joint in full extension and wrist in 40
degrees of extension with slight radial deviation.
- For injuries in zone VI and VII the abductor pollicis longus
retracts when divided and therefore requires to be released for
successful repair.
- Splinting is then needed for 4-5 weeks with the wrist in radial
deviation and the thumb in maximal abduction.
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63. - The ultimate aim of any rehabilitation is to obtain healing
with minimal gapping and prevent adhesions.
- complications include:
- tendon rupture
- adhesion formation requiring tenolysis.
- extension lad
- loss of flexion and decreased grip strength
- deformities
- infection
- Early mobilisation rehabilitation programes can be in
two categories:
(1) early active mobilisation
(2) early controlled mobilization using a dynamic splint which
has been found to decrease adhesions and subsequent
contractures.
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