Forearm dislocations: clinical presentation
Displacement of the forearm bones is accompanied by marked deformation and the risk of neurovascular injuries (especially to the brachial artery and ulnar nerve). Checking the pulse and sensation is strictly mandatory before and after any manipulations.
- Posterior dislocation: the olecranon projects abnormally backward, lying above the epicondylar line. The humeral epiphysis can be palpated in the cubital fossa. Frequently accompanied by a coronoid process fracture.
- Anterior dislocation: the forearm appears extended and elongated, while the arm seems shortened. The olecranon cannot be felt posteriorly (sometimes a fossa is palpable in its place). It is complicated by neurovascular disorders and triceps tendon avulsion more often than other types.
Algorithm for reduction and management of forearm dislocations
Attempts at self-reduction at the prehospital stage are inadmissible. The patient is fitted with a transport splint (extended arm for anterior dislocation, sling for posterior dislocation) and transported to the hospital for mandatory radiography.
Reduction is performed on an emergency basis under full anesthesia (general anesthesia):
- Posterior dislocation: against the background of axial traction, the surgeon presses with the thumbs on the olecranon from back to front. After reduction, a posterior plaster splint is applied (forearm flexed at an acute or right angle if blood flow is compromised). Duration of immobilization — no more than 7 days.
- Anterior dislocation: following traction, the forearm is flexed, and the articular end of the humerus is displaced anteriorly. A plaster cast is applied in the supinated position for 10–12 days.
If closed reduction fails, surgical intervention is indicated, but only in the absence of signs of ossification (which can begin as early as 2 weeks). An isolated radial head dislocation is often irreducible due to interposition of the ruptured annular ligament — surgery is required in such cases.
Perilunate (dorsal) wrist dislocation
Occurs upon falling on an outstretched hand with a hyperextended wrist. The lunate bone retains its anatomical position, whereas the entire remaining mass of the carpus is displaced dorsally.
Clinical features:
- Bayonet-like deformation of the wrist region.
- Fingers are reflexively semiflexed.
- Acute pain upon palpation of the dorsal aspect of the hand.
- Springing resistance when attempting movement.
A typical mistake is to mistake this injury for a sprain. Lateral radiographs help detect the displacement. Reduction is performed by axial traction and strong pressure on the dorsum of the hand until an audible click is produced. A plaster cast is applied in a flexed position (135–140°) for 2 weeks, after which the hand is moved into a functional position for another 2–4 weeks.
Dislocation of the lunate bone
Forms during extreme dorsal flexion: adjacent bones "squeeze" the lunate bone anteriorly, tearing the ligaments. It displaces onto the palmar surface and often rotates by 90°.
Key symptoms:
- Severe edema and depression on the dorsal aspect of the wrist joint.
- The bone itself is palpable on the palmar surface.
- Third finger extension sign: pressing on the dislocated bone causes the 3rd finger to extend (due to reduced tension on its flexor tendon).
- Complete inability of active wrist extension.
The dislocation is reduced under general or regional anesthesia: strong traction is combined with forceful extension, after which the surgeon pushes the lunate bone with a finger and abruptly brings the wrist into palmar flexion. The criterion of success is the disappearance of the deformity and free passive movements. The limb is immobilized with a plaster cast from the metacarpal heads to the upper third of the forearm.
Briefly: answers to topical questions
Which ligaments are torn in a lunate dislocation?
During a lunate dislocation, the dorsal radiolunate ligament is ruptured, as well as the ligaments connecting it to other carpal bones. Furthermore, this injury is always accompanied by a rupture of the interosseous ligaments of the proximal carpal row. Damage to the ligamentous apparatus is due to the lunate being squeezed anteriorly under the action of the capitate and radius.
What types of finger phalangeal dislocations are distinguished by the direction of displacement?
Depending on the direction of displacement, three main types of finger phalangeal dislocations in the interphalangeal joints are distinguished.
- Dorsal — occur most frequently among all injuries of this localization.
- Palmar — diagnosed significantly less often.
- Lateral — are also included in the classification by direction of displacement.
Diagnosis of these types of dislocations is based on a typical medical history, characteristic deformity, functional limitation, and radiographic data.
How is a dorsal dislocation of the thumb reduced?
Reduction of a dorsal thumb dislocation is performed via smooth, but powerful traction with a slow increase in finger hyperextension until an acute angle with the metacarpal bone is formed. This is necessary to eliminate potential interposition of the sesamoid bones. Then, the surgeon rests their thumb against the base of the proximal phalanx, striving to shift it distally, while using the other fingers to apply counter-pressure on the head of the metacarpal bone. After feeling the base of the phalanx slide onto the articular surface, the surgeon rapidly extends the distal phalanx and flexes the finger.
The rule of thumb to distinguish carpal dislocations: in a PERIlunate dislocation, the PERIphery displaces (all bones except the lunate), whereas in a LUNATE dislocation, only the lunate bone itself displaces.
Class and exam questions
Why is thermal therapy contraindicated after an elbow injury?
Any thermal therapy provokes rapid ossification of the periarticular tissues, leading to severe and irreversible contractures.
What to do if closed reduction of the lunate bone fails?
In such a situation, emergency open (surgical) reduction followed by plaster immobilization is indicated.
How to know that the reduction was successful?
Full range of passive motion is restored, the bulging of the displaced bone disappears, the patient can extend the fingers, and a click is often heard at the moment of reduction.
What else to study on this topic
- Technique of elbow arthroplasty for chronic dislocations with ossification.
- Annular ligament reconstruction for isolated radial head displacements.
- Neurological deficit due to median and ulnar nerve compression in the carpal tunnel.
- Application of distraction-compression devices for irreducible perilunate dislocations.
- Physical therapy programs in the late rehabilitation stages after wrist injuries.
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