Common injuries of the forearm

Monteggia-Fracture dislocation

Defined as fracture of the upper 1/3 of ulnar, together with dislocation of the head of radius.
The mechanism of injury is usually fall on an out-stretched hand with hyper-pronation of the forearm.
Occasionally, it can be caused by direct blow towards the back of forearm.

Clinical features

The deformity over the site of fracture (upper 1/3 of ulnar) is usually obvious.
However, the dislocated radial head can be obscured by the presence of swelling.
Pain and tenderness over the lateral aspect of elbow joint is suggestive.
It can be complicated as a radial nerve injury, causing wrist drop or injury to it's branch, the posterior interosseous nerve, causing finger drop.


Radiological features

An AP view of the elbow joint usually shows clearly the fractured upper 1/3 of ulna, and the head of radius no longer pointing towards the capitulum.
On lateral view, there are 2 types of appearance :

a) Extension type (more common) : Anterior angulation of ulna fracture + forward displacement of radial head
b) Flexion type : Posterior angulation of ulna fracture + backward displacement of radial head

Complications

1) Nerve injury
Usually caused by over-enthusiastic surgical manipulation of the dislocated radial head
However, it's a neuropraxic injury, where recovery is expected within months

2) Mal-union
Caused by imperfect reduction of the fracture, where the radial head remains dislocated.
Restricted flexion of elbow joint.
Requires open reduction and internal fixation, with excision of radial head with or without prosthetic replacement.

3) Non-union
Requires open bone grafting and internal fixation with excision of radial head.

Treatment

Close reduction is attempted first under general anesthesia.
For the next 3-4 weeks, X ray is done to check the progress of healing.
If unsatisfactory or re-displacement occurs, open reduction and internal fixation is done.

Galeazzi Fracture-dislocation

This condition is more common than it's counterpart (Monteggia FD)
Defined as fracture of the distal third of radius with dorsal displacement of distal ulna or distal radio-ulnar joint.
Mechanism of injury : Fall on out-stretched hand

Clinical features

Prominence and tenderness over the ulnar styloid process.
Piano-key sign : The distal third of radius is ballotable
Instability of the distal radio-ulnar joint can be made prominent by supination and pronation of forearm.
Can be complicated as ulnar nerve injury (resulting in Ulnar claw hand)

Radiological features

Transverse of oblique fracture of the distal third of radius.
Dorsal displacement of the distal ulna or the distal radio-ulnar joint.

Complications

Main complication is mal-union, which limits supination and pronation of the forearm.

Treatment

Close reduction is not done (unless in children), since this fracture is unstable.
Instead, open reduction and internal fixation is done.

Colles' fracture

As described by Abraham Colles, it's defined as fracture of the distal radius just above the wrist at the level of cortico-cancellous junction, with radial displacement and backwards tilt of the distal fragment.
Mechanism of injury : fall on out-stretch hand
It is the most common osteoporotic-related fracture in the upper limb.
Hence, it is common among post-menopausal women.

Patho-anatomy

The distal end of radius articulates with the carpal bones, forming the radio-carpal joint.
Similarly, it articulates with the distal end of ulna, forming the distal radio-ulnar joint.
The articular surface of distal end of radius is directed ventrally and medially.
The styloid process of radius is about 1cm distal to the ulnar styloid process.

Clinical features

Pain, swelling, deformity.
Palpation over distal radius : tenderness and irregularity.
Dinner fork deformity.
Radial styloid being leveled or situated proximal to the ulnar styloid.

Complications

1) Joint stiffness

Involving the fingers, wrist, elbow and shoulder.

2) Mal-union

Occurs usually unnoticed within the immobilisation cast.

3) Subluxation of the distal radio-ulnar joint

Resulting shortening of the radius, which made the ulnar styloid more prominent.
Hence, any movement of the wrist joint involving pronation/supination or ulnar deviation is restricted or is painful.

4) Carpal tunnel syndrome
5) Ruptured tendon of extensor policis longus
6) Sudeck's osteodystrophy

Colles' fracture is the commonest cause of this condition in the upper limb.
Characterised by pain, swelling of wrist, hand and fingers, and deformity.
There's diffuse tenderness, and the skin over it appears glazed, stretched.
Treated by physiotherapy.

Treatment

1) Undisplaced

Cast immobilisation for 6 weeks, applied below elbow towards the neck of metacarpals.
Hand is immobilised in functional position, with slight palmar flexion and ulnar deviation.

2) Displaced (with dinner fork deformity)

First, close manipulative reduction is done under anesthesia.
Ask your assistant to apply traction over the wrist joint by holding the patient's hand, and counter traction at the elbow joint.
Press over the dorsal aspect of deformity, at the same time try palmar-flexing, ulnar deviation, and pronating the hand.
After reduction, confirm that it's properly done by X ray.
Apply colles' cast.

3) Comminuted

Requires open reduction and internal fixation.

Category: Orthopedics Notes