Forearm instability

Bahaa Kornah - Al-Azhar UN. - Cairo EGYPT
Dr. Bahaa Ali Kornah
Prof.. Of Orthopedic
Al-Azhar University
Cairo - Egypt
‫وبركاته‬ ‫هللا‬ ‫ورحمة‬ ‫عليكم‬ ‫السالم‬

Bahaa Ali Kornah-Al-Azhar Un. Cairo -EGYPT

FOREARM INSTABILITY
Dr. Bahaa Ali Kornah
Prof.. Of Orthopedic
Al-Azhar University
Cairo - Egypt

Learning Objectives
Definition of longitudinal forearm instability
Injury patterns
Anatomy of the interosseous membrane
Structures involved lead to instability
Diagnosis of longitudinal forearm instability
Treatment options for forearm instability

Definition
• Forearm instability is a complex problem
resulting from traumatic disruption of
the forearm stabilizers:
1. the radial head,
2. the interosseous membrane, and
3. the triangular fibrocartilage complex

Anatomy and Biomechanics of
Forearm Stabilizers

STRUCTURE of PROXIMAL (superior) RADIO-
ULNAR JOINT
• Articulating surface:-
Radial notch of ulna
Annular ligament
Head of radius
Capitulum of humerus.

• RADIAL NOTCH OF ULNA:
Location:- lateral aspect of proximal ulna, directly
below the Trochlear notch.
The surface of radial notch is concave and covered
with Articular cartilage.
• ANNULAR LIGAMENT:
circular in shape (Ring).
Attachment:- anterior and posterior edges of the
notch. The ligament is lined with Articular cartilage,
which is continous with the cartilage lining of the
radial notch.
 The annular ligament encircles the Rim of the radial
head, which is also covered with articular cartilage.
 Mechanoreceptors are evenly distributed throughout
the ligament.

ARTICULATIONS
•PROXIMAL RADIO-ULANR
ARTICULATION:
Bones >>>>>Head of radius and radial
notch of the ulna.
Soft tissues >>>> Annular ligament (The
head of radius is attached to the radial notch of the ulna )
•DISTAL RADIO-ULANR ARTICULATION:
Bones >>>>> Head of ulna and ulna
notch of radius.
Soft tissues >>>> triangular fibrocartilage
complex (TFCC) The Head of the ulna attached to the ulna
notch of radius and Articular disc.

LIGAMENTS
• PROXIMAL RADIO-ULNAR
JOINT:
1. Annular ligament
2. Quadrate ligament
3. Oblique cord.
• DISTAL RADIO-ULNAR JOINT:
1. Dorsal radio-ulnar ligament
2. Palmar radio-ulnar ligament
3. Interosseous membrane.

LIGAMENTS of PROXIMAL RADIO-ULNAR
JOINT
• ANNULAR LIGAMENT:
Strong band
The inner surface of the ligament
covered with head of Radius and
cartilage.
ATTACHMENT- proximally attached to
anterior margin of the radial notch.
Distally attached to posterior margin of
the radial notch.
The proximal border of the annular
ligament blends with the joint capsule.
Lateral aspect is reinforced by fibers
from the Lateral collateral ligament.

• QUADRATE LIGAMENT:
ATTACHMENT- extends from the inferior
edge of the radial notch of the ulna to
neck of the radius.
It reinforces the inferior aspect of the joint
capsule.
FUNCTION:
It helps maintain the radial head in
apposition to the radial notch.
It limits spin of the radial head in supination
and pronation.

• OBLIQUE CORD:
It flat facial band on the ventral
forearm.
ATTACHMENT- inferior to the
radial notch of the ulna to just
below the radial tuberosity.
FUNCTION:
Functional signification is not clear.
It may assist in preventing
separation of the radius and ulna.

DISTAL(inferior) RADIO-ULNAR JOINT
•Articular surface:
Ulnar notch of the
radius
Articular disc
Head of ulna

• ULNAR NOTCH OF RADIUS:
Location:- distal end of the radius along
the interosseus border.
Ulnar notch is larger than the ulnar head.
• ARTICULAR DISC:
It also called Triangular fibrocartilage
(because of its triangular shape).
Attachment:-
Base- distal edge of the ulnar notch of the
radius.
Apex- 2 attachment. One is to Fovea on the
ulnar head and another one is base of the
ulnar styloid process.
FUNCTION- it provide stability for the
inferior radio-ulnar joint.

LIGAMENTS of DISTAL RADIO-ULNAR
LIGAMENT
• PALMAR AND DORSAL RADIO-ULNAR LIGAMENTS:
It attached to ulnar fovea and base of ulnar
styloid process.
• INTEROSSEOUS MEMBRANE:
It is strong, thick, ligamentous, or tendinous
structure.
The fibers run obliquely from the radius to the
ulna.
It attached to interosseous border of the radius
and ulna.
FUNCTION:
Maintains space between the radius and ulnar
during forearm rotation.
Provides stabilization at both the Proximal and
Distal radio-ulnar joint.
It maintains transverse stability of the forearm
during compressive load transfer from hand to
elbow.

The interosseous
membrane is composed of 5
ligaments:-
**Central band (key portion
to be reconstructed in case
of injury)-
**Accessory band-
**Distal oblique bundle-
**Proximal oblique cord-
**Dorsal oblique accessory
cord

MUSCLES
• :
PRONATION
1. Pronator teres
2. Pronator
qudratus.
• SUPINATION:
1. Biceps
2. supinator

PRONATORS of SUPERIOR and INFERIOR
RADIO-ULNAR JOINT
Pronators teres:
•Origin:- medial epicondyle (common flexor tendon)
of humerus and coronoid process of ulna.
•Insertion:-middle of lateral surface of radius just
below supinator muscle.
•Nerve supply:- median nerve
•Action :- pronation of forearm. And Weak flexor of
elbow

Pronator quadratus:
• Origin:- distal quadrater of ulna (anterior surface)
and lower part of ulna.
• Insertion:- distal quadrater of radius lower
border of anterior surfaces.
• Nerve supply:- median nerve
• Action:- pronation.
• Function:- distal radio-ulnar joint stabilization.

SUPINATORS of SUPERIOR and INFERIOR
RADIO-ULNAR JOINT
Supinator:
•Origin:-
1. lateral epicondyle of humerus,
2. supinator crest of ulna, radial
collateral ligament, annular ligament
of radius.
•Insertion:- inserted into upper part of
lateral surface of
radius.
•Nerve supply:- radial nerve
•Action:- supination.

The ‘forearm unit’
• Forearm as a single functional
unit
• Comprises
1. the radius and ulna and
2. their bony and soft tissue
interactions, namely the
• proximal radio-ulnar joint
(PRUJ),
• DRUJ and theBahaa Kornah - Al-Azhar UN. - Cairo EGYPT

The function 'forearm unit’
Maintain structural stability of the radius
relative to the ulna and prevent
divergence,
Transfer load from the distal radius at the
wrist to the proximal ulna at the elbow
and
Provide attachment for the muscles
traversing the hand, wrist and elbow.

 THE RADIAL HEAD IS THE PRIMARY contributor to
longitudinal forearm stability.
 Secondary stabilizers are the triangular
fibrocartilage complex (TFCC) and the interosseous
membrane (IOM),
• .

Three mechanical principles
underpin normal forearm
function.
• Primary axial stabilizer of the forearm is the
radial head
• Secondary stabilizers are the IOM and the
ligaments around the DRUJ and PRUJ.
• The third principle is that the IOM is solely
responsible for transfer of load between the
wrist and elbow.

Forearm instability
• “The forearm as a ring”
concept
• Key role of
– Radial Head
– IOM
– TFCC
• Double or Multiple
injuries to the ring
common

Load transfer
Prevent radius and
ulna bowing
Role of IOM

Forearm Interossous Membrane
• Contributes 70% of forearm stability
Radius
CB
•Can be injured in association with elbow fractures
Ulna

longitudinal forearm instability
• Acute
• Chronic

Mechanism of Injury
• Longitudinal forearm instability results from a
trauma that disrupts the forearm unit.
• A fall onto the outstretched hand imparts an
axial force with resultant radial head fracture and
TFCC and IOM disruption, resulting in
1. the Essex-Lopresti injury pattern.
2. Galeazzi fractures (radial shaft fracture with associated
dislocated DRUJ) and
3. Monteggia fractures (ulna shaft fracture with associated
radial head dislocation)

Monteggia fracture-dislocation

Path mechanics of Instability
• traumatic axial load through the forearm,
• >>>> radial head fracture.
• may or may not be associated with
disruption of the TFCC and the IOM .

• A, Normal force transmission across
radius and ulna at the wrist and elbow.
The interosseous ligament (IOL) and
distal radioulnar joint (DRUJ) distribute
some of the radial load to the ulna,
which is evident from the change in
distribution of force at the wrist and
elbow. B, When the interosseous
ligament complex (ILC) and DRUJ are
disrupted, there is no transfer of load
between the radius and ulna. These
two bones act independently of each
other when force is applied.

• C, When the radiocapitellar
relationship is lost, as with a radial
head resection or fracture of the
neck or head, the ulna transmits
the entire load to the elbow. The
ILC and DRUJ become crucial in
load transfer and likely experience
stress, eventually stretching over
time. D, With injury to the IOL and
DRUJ, the radius is longitudinally
unstable and dissociated from the
ulna, allowing the radius to migrate
proximally

Diagnosis
• may not be obvious; maintain high index of
suspicion

Diagnosis
Acute longitudinal forearm instability
• A high index of suspicion
• history : axial loading injury
mechanism to the arm
• Examination of the whole
upper limb is essential.
• Concomitant bruising,
swelling or tenderness in
the elbow, forearm or wrist
may be present .
• although there is often mild
wrist tenderness with radial
head fractures .

Fingers comparative test. Clinical image of
the C-Fingers comparative test

Imaging
• Static x rays
• a radial head fracture. (comminuted or
with evidence of impaction).
• lateral elbow x ray : A loss of ‘empty
space’
• Assess wrist radiographs for evidence of
positive ulna variance, ulna styloid fracture
or DRUJ subluxation.
• Comparative contralateral wrist x rays
should be obtained.

a The ‘empty space’ sign.
b A multifragmentary radial head fracture with divergence of the
articular fragments and proximal migration

• Dynamic x rays
• Pronator grip view: A difference in
positive ulna variance may be observed;
• Axial compression test : abnormal
longitudinal motion to be a 5 mm or more
change in ulnar variance under loading.

the axial
compression test.
A distractive (a)
and
compressive (b)

• Ultrasound
• Under ultrasound (USS) the (Central band ) CB of the
IOM appears as a hyperechoic line, at least 2 cm in
length between the radius and ulna in the middle third of
the forearm and is clearly differentiated from the muscles
.
• A torn, CB looks wavy, slack and discontinuous and can
be identified with up to 96 % accuracy on USS
• Dynamic USS, the ‘muscular hernia sign’ where the
volar forearm muscles through the CB defect when
a dorsally directed pressure is applied to the volar
compartment.

• Magnetic resonance imaging
• from high signal and oedema within the
IOM, to partial tears of the IOM and
complete disruptions of the CB
• it is essential to correlate MRI with the
other clinical findings.

Intra-operative tests
• The ‘pull test’ is performed after removal of the radial head fragments and
applying longitudinal force through the forearm.
• radial ‘joystick test’ . a pronated forearm using a bone holding clamp
hold proximal radius >>>> where a laterally directed force >>>> Splaying
of the radius and ulna with lateral displacement of the radius signifies
a positive test and indicates complete disruption of the IOM
• extended supinated position, 5.5 mm of lateral displacement >>>>>IOM
disruption
• Radial axial interosseous load (RAIL) test
• .
• The DRUJ should be assessed for evidence of instability in neutral rotation,
pronation and supination and a comparison should be made with the
contralateral wrist

Diagnosis of chronic
longitudinal instability
• History of elbow and wrist, pain and dysfunction.
• Grip strength is reduced and forearm rotation, especially
pronation may be restricted or provoke pain
• History of previous axial injury and radial head fracture,
which may have been treated surgically or not.
• There may be prominence of the ulna head at the wrist
secondary to chronic proximal migration of the radius
• +ve grip and grind test indicating arthrosis of the
radiocapitellar joint.

• A high index of suspicion ,sign should alert
the clinician to the possibility of
longitudinal instability.
history :
Signs of early failure of radial head ORIF,
early loosening of radial head replacement
or
 capitellar erosion with proximal migration
of the radius should alert the clinician to the
possibility of longitudinal instability.

• Radiographs will usually demonstrate
positive ulnar variance
changes at the radiocapitellar joint,
malunion of the radial head or
previous surgery to the radial head.

Management of
The aims of treatment are to
• Restore and maintain the mechanics and motion of
the forearm unit,
• Restore normal load transfer between the wrist
and elbow and
• Prevent or treat the adverse sequelae of chronic
longitudinal instability.

Treatment Options
• Once the diagnosis of forearm instability
has been made, there are a number of
potential treatment options to reestablish
forearm stability and maximize functional
outcomes. These can be divided into
options for acute injuries versus chronic
forearm instability.
•

address the specific components
of the injury
• Bone
– Radial head (repair or replacement)
• Ligaments
– Repair or reconstruction

Treatment Strategies
Must be employed at the
• elbow,
• forearm and
• wrist,
• whether this is in the acute or chronic setting.

• The elbow (radial head)
• In an acute injury a radial head fracture
may be the only apparent component of
an Essex Lopresti lesion. The radial head
should always be repaired or replaced if
longitudinal instability is suspected.
• repair more challenging
• A range of radial head arthroplasty
implants metallic and pyro carbon bearing
surface options.

• Pyro carbon implants may cause less
erosion of native cartilage This may be of
value in the presence of longitudinal
instability and supraphysiological
radiocapitellar loading.
• Silastic implants should be avoided
• not resist axial loading
• associated with fracture and
• destructive synovitis

RH replaced
Important consideration
1. Correct diameter,
2. height, the implant length >> rapid capitellar
erosion
3. medial offset and
4. cervico-cephalic angle

• The wrist
• treatment of TFCC pathology or joint leveling
procedures to treat positive ulna variance.
1. Repair of the TFCC should be
considered.
2. An alternative, cross pin the radius
and ulna in the distal third of the
forearm with the DRUJ reduced.
3. Ulna shortening osteotomy for
ulnocarpal abutment

• Interosseous ligament reconstruction
• reconstruction
• it was demonstrated that IOM
reconstruction in combination with radial
head replacement was superior at
redistributing normal loads between the
wrist and elbow than radial head
replacement alone.

• Interosseous ligament reconstruction
• IOM reconstruction in both the acute and chronic clinical setting in
order to restore normal load transfer and reduce wrist and elbow
pain following longitudinal instability.
• techniques using a variety of
1. Achilles tendon allograft ,
2. flexor carpi radialis
3. palmaris longus,
4. bone patellar bone graft and
5. synthetic grafts .
1. Disadvantage insufficient tensile strength to
resist elongation under loading,

Reconstruction for
Interosseous Ligament
Disruption
Masouros PT et al J Hand Surg Eur Vol.
2020

LigamentAugmentation and Reconstruction System
(LARS)

• Salvage procedures
• Pain and dysfunction.
1. the Sauve Kapanji procedure and
2. creation of a one-bone forearm (radio-
ulnar synostosis).
3. Disadvantage do not restore a good
level of function only for pain relief.

• Salvage procedures
• The Sauve Kapanji procedure
addresses wrist pain, but by
excision of a segment of the ulna
shaft, is likely to further disrupt
load transfer and hence should
be viewed with caution for the
treatment of longitudinal
instability.

 Distal radio ulnar joint
reduction(pinning)

• INJURY PATTERNS Galeazzi fracture-dislocation
(reverse Monteggia,
• A fracture of the radial shaft, typically at the
junction of the middle and distal thirds, may
result in shortening and angulation and,
therefore, disruption of the DRUJ.
• The eponym “fracture of necessity” += surgical
treatment is typically necessary.

• INJURY PATTERNS Galeazzi fracture-dislocation
(reverse Monteggia,
ORIF +the TFCC may be repaired and/or the
forearm pinned in supination in a reduced
position.
Longitudinal forearm instability does not
occur because the central portion of the IOM
remains intact.

• Monteggia Fracture-Dislocation =
• a fracture of the proximal ulna with
associated radial head dislocation.
• DD >>> trans olecranon fracture-dislocation,
((fracture of the olecranon with dislocation of the radiocapitellar rather than the
proximal radioulnar joint)).
• 4 types
• anatomical reduction and fixation of the ulnar
fracture, +radial head reduction

operative and nonoperative
treatment

• Monteggia Fracture-Dislocation =
Failure of the radial head reduction may be
**interposed annular ligament,
**joint capsule, or
**osteochondral fragments.
• Malunion of the ulna and failure to achieve reduction
of the radial head may lead to valgus instability of
the elbow, arthritis at the Radiohumeral joint and
proximal radioulnar joint, and restricted forearm
rotation.

Essex –Lopresti injury OR
longitudinal radioulnar
dissociation

is a complex injury that includes
 fracture of the radial head
 rupture of the interosseusmembrane of the forearm

 impaired integrity of the distal radioulnar joint

 Essex –Lopresti lesion leads to instability of the
forearm
 central migration of the radius.
 restriction of the radiocarpal motion
 reduction of the grip strength and wrist pain.

• TREATMENT disruption of both the IOM and
the TFCC.
• At the wrist, the DRUJ is reduced and
stabilized by repair of the TFCC.
• for the forearm, ranging from
• observation,
• interosseous ligament repair,
• stabilization via immobilization with pinning or orthosis
fabrication, or
• ligament reconstruction or augmentation,

• joint-leveling procedure at the wrist (usually
an ulnar-shortening osteotomy), addressing
the elbow pain with a procedure at the elbow,
and often but not always, a procedure to
reconstruct the IOM of the forearm.

 Radial head replacement
TREATMENT

Essex-Lopresti Injuries
• • Radial Head
 Reconstruction-
 Replacement
• DRUJ reduction- pinning in
supination
• TFCC repair?
• IOM reconstruction ?
•
•
•
Courtesy : D.G. Sotereanos, MD

TAKING HOME MESSAGE
• Stability of the forearm is gained by osseus and soft tissue.
Rare lesion after high energy axial load
Need to address soft tissue injury
Prognosis is generally poor

• Kapandji (Physiology of joints).Birkbeck, D, Failla, J, Hoshaw,
S, Fyhrie, D, Schaffler, M. The interosseous membrane
affects load distribution in the forearm. J Hand Surg
Am. 1997, 22: 975–80
• k. Levangie and cynthia c. Norkin (Joint structure and function),
• Claes, S, Verdonk, P, Forsyth, R, Bellemans, J. The
“ligamentization” process in anterior cruciate ligament
reconstruction: what happens to the human graft? A
systematic review of the literature. Am J Sports Med. 2011,
39: 2476–83.
• Frank h. Netter. Md (Atlas of human anatomy),
• Gilroy (Atlas anatomy),
• Harley, B, Pereria, M, Werner, F, Kinney, D, Sutton,
L. Force variations in the distal radius and ulna: effect of
ulnar variance and forearm motion. J Hand Surg Am. 2015,
40: 211–6.
Refrances

Bahaa Ali kornah . Al Azhar Un. Cairo-
EGYPT
‫وبركاته‬ ‫هللا‬ ‫ورحمة‬ ‫عليكم‬ ‫السالم‬
Good Luck
and Thank
You for Your
Attention
bkornah@gmail.com
Bahaa Kornah. AlAzhar Un. Cairo EGYPT

Forearm instability

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