Courtesy: Saurabh Agarwal, Consultant, UK

Introduction

Perilunate injuries involve disruption of the ligamentous and bony relationships between the lunate, adjacent carpal bones, and the distal radius.
These injuries represent severe wrist trauma and can lead to persistent pain, instability, and functional impairment if not recognized early.
Perilunate and lunate dislocations together account for the majority of carpal dislocations.

Carpal Alignment and Gilula Lines

Assessment of carpal alignment on a posteroanterior wrist radiograph is performed using Gilula lines.

Gilula Lines

Three smooth arcs should normally be seen:

First arc
- Formed by the proximal convex surfaces of the scaphoid, lunate, and triquetrum.
Second arc
- Formed by the distal convex surfaces of the same bones.
Third arc
- Formed by the proximal surfaces of the capitate and hamate.

Clinical Importance

Any break or irregularity in these arcs indicates possible carpal instability or fracture-dislocation.

Mechanism of Injury

Perilunate injuries usually occur following high-energy trauma.

Common causes include:

Fall on an outstretched hyperextended wrist
Motor vehicle accidents
Sports-related trauma

Pathomechanics

Force is transmitted through the extended wrist, producing progressive disruption of intercarpal ligaments and carpal alignment.

Stages of Perilunate Injury (Mayfield Classification)

The Mayfield classification describes the progressive sequence of ligament failure during wrist hyperextension injury.

Stage 1

Scapholunate ligament disruption
Results in scapholunate dissociation

Stage 2

Disruption between the capitate and lunate
Leads to lunocapitate dislocation

Stage 3

Disruption between the lunate and triquetrum
Produces perilunate dislocation, where the capitate displaces dorsally relative to the lunate.

Stage 4

Complete failure of stabilizing ligaments
The lunate dislocates volarly into the carpal tunnel

Types of Perilunate Injuries

Trans-Scaphoid Perilunate Dislocation

The most common pattern.
Characterized by:
- Fracture of the scaphoid
- Associated perilunate dislocation

Other Injury Patterns

Partial or complete lunate dislocation
Associated fractures involving:
- Scaphoid
- Triquetrum
- Capitate
Independent displacement of fractured carpal fragments may occur.

Degrees of Lunate Displacement

Lunate dislocations can be graded according to the degree of rotation and displacement.

Grade 1

Normal lunate alignment.

Grade 2

Palmar rotation of approximately ninety degrees, but still attached to the radius.

Grade 3

Further rotation with partial loss of ligament attachment.

Grade 4

Complete enucleation of the lunate, with loss of attachment to the radius.

Clinical Presentation

Symptoms

Patients typically present with:

Severe wrist pain
Swelling
Visible deformity
Reduced wrist movement

Physical Findings

Radial deviation of the wrist
Tenderness around the carpus
Volar prominence of the lunate may be palpable
Markedly restricted wrist motion

Neurological Complication

Median nerve compression may occur due to volar displacement of the lunate into the carpal tunnel.

Diagnostic Imaging

Plain Radiographs

Radiographic evaluation should include posteroanterior and lateral wrist views.

Typical Findings

Disruption of Gilula arcs
Loss of normal carpal alignment
Associated fractures

Classic Radiographic Signs

Lateral View

Spilled teacup sign
- Represents volar rotation of the lunate.

Posteroanterior View

Triangular or piece-of-pie appearance of the lunate
Capitate not aligned with the lunate fossa of the radius

Associated Fractures

Scaphoid fracture
Triquetral fracture

Advanced Imaging

Computed Tomography

Provides detailed evaluation of carpal fractures and fragment displacement.

Magnetic Resonance Imaging

Useful for assessing ligament injuries and soft tissue damage.

Treatment

Management depends on severity, timing of diagnosis, and associated injuries.

Closed Reduction

Closed reduction may be attempted in acute cases.

Principle

Restoration of normal carpal alignment without surgery.

Technique

Apply longitudinal traction to the wrist.
Gradually flex the wrist while maintaining traction.
Manipulate the carpal bones to restore normal alignment.

Indicators of Successful Reduction

Restoration of Gilula arcs
Normal scapholunate gap
Proper intercarpal alignment

Immobilization

Wrist immobilized in a cast for approximately eight to twelve weeks.

Percutaneous Pinning

Kirschner wires may be used to stabilize:
- Scapholunate joint
- Lunotriquetral joint
- Other unstable carpal relationships

This maintains alignment during ligament healing.

Surgical Management

Open Reduction and Internal Fixation

This is the preferred treatment in most cases, particularly when:

Closed reduction fails
Fractures are present
Instability persists

Surgical Goals

Restore carpal alignment
Repair injured ligaments
Fix associated fractures
Prevent long-term instability

Complications

Delayed diagnosis or inadequate treatment can result in:

Chronic carpal instability
Post-traumatic wrist arthritis
Median nerve injury
Persistent pain and reduced wrist motion

Outcomes

Functional outcome depends mainly on:

Early diagnosis
Accurate reduction
Stable fixation
Proper rehabilitation

Delayed treatment increases the risk of permanent wrist dysfunction and degenerative changes.

Key Points

Perilunate injuries represent serious wrist trauma requiring prompt recognition.
Radiographic evaluation using Gilula lines is essential for diagnosis.
The Mayfield classification describes progressive ligament injury stages.
Trans-scaphoid perilunate dislocation is the most frequent injury pattern.
Early reduction and stabilization significantly improve functional outcomes.

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