Perilunate Injuries

Courtesy Dr Jefferey Yao, Dr Ashok Shyam, Ortho TV

Basic Wrist Ligament Anatomy

• Wrist ligaments act as static stabilizers that guide and constrain motion of the carpus.
• Wrist ligaments are classified into two main groups:

Intrinsic Ligaments

• Located entirely within the carpal bones.
• Connect adjacent carpal bones.
• Example:
  • Scapholunate ligament
  • Lunotriquetral ligament

Extrinsic Ligaments

• Connect carpal bones to the radius or ulna.
• Cross either:
  • Radiocarpal joint
  • Midcarpal joint

 

Concept of Carpal Instability

• Malalignment does not necessarily equal instability.
• Some individuals (e.g., ligamentous laxity) may show radiographic malalignment but remain asymptomatic.

 

True Carpal Instability

Defined as:

• Abnormal load transfer across the carpal joint
• Abnormal motion between carpal bones
• Associated pain and functional impairment

 

Classification of Carpal Instability (Mayfield Concept)

Carpal instability is classified as:

1. Carpal Instability Dissociative (CID)

• Instability within a carpal row
• Example:
  • Scapholunate dissociation

2. Carpal Instability Non-Dissociative (CIND)

• Instability between proximal and distal carpal rows

3. Carpal Instability Complex (CIC)

• Combination of CID and CIND
• Seen in perilunate dislocations

 

Perilunate Injuries

• Represent a spectrum of carpal instability injuries.
• Usually occur due to high-energy trauma.

Common Mechanisms

• Motorcycle accidents
• Falls from height
• Falls from ladders or scaffolds

Mechanism of Injury

• Forceful wrist hyperextension
• Ulnar deviation
• Carpal supination

 

Mayfield Classification of Perilunate Instability

Describes progressive ligament injury around the lunate.

Stage I

• Scapholunate ligament rupture
• In greater arc injuries:
  • Scaphoid fracture

 

Stage II

• Injury progresses through capitolunate joint
• May include:
  • Capitate dislocation
  • Capitate fracture

 

Stage III

• Additional injury to:
  • Lunotriquetral ligament
• Lunate remains in the lunate fossa

 

Stage IV

• Complete lunate dislocation
• Lunate displaced volarly into the carpal tunnel

 

Types of Perilunate Injuries

Lesser Arc Injuries

• Pure ligamentous injuries
• No associated fractures

Greater Arc Injuries

• Include fractures of carpal bones
• Examples:
  • Scaphoid
  • Capitate
  • Triquetrum
  • Radial styloid

 

Radiographic Diagnosis

Perilunate injuries are commonly missed on wrist X-rays.

PA View Findings

• Loss of Gilula’s arcs
• Triangular-shaped lunate (instead of trapezoidal)
• Known as the “piece-of-pie sign.”

Lateral View Findings

• Volar displacement of lunate
• Known as the “spilled teacup sign.”

 

Reverse Perilunate Injury

• Injury progression begins ulnar side first.
• Starts with lunotriquetral ligament rupture.
• Progresses counterclockwise toward the scapholunate side.

 

Initial Management

1. Median Nerve Assessment

• Median nerve compression is common due to lunate displacement into the carpal tunnel.

 

2. Closed Reduction (Emergency)

Performed under adequate sedation.

Reduction steps:

• Apply longitudinal traction
• Hyperextend wrist
• Stabilize lunate with thumb
• Gradually bring wrist into flexion
• Capitate reduces back into alignment with lunate

 

Definitive Treatment

Most cases require early surgical stabilization.

Options

Arthroscopic Management

• Reduction
• Percutaneous pinning
• Capsular repair

Advantages:

• Less soft tissue disruption
• Preservation of blood supply
• Less scar formation
• Allows evaluation of associated injuries

 

Open Reduction and Internal Fixation

Approaches include:

Dorsal Approach

• Access to dorsal scapholunate ligament
• Most important stabilizing component

Volar Approach

• Access to:
  • Volar lunotriquetral ligament
  • Volar capsule
• Allows median nerve decompression

Combined Dorsal + Volar Approach

• Used for severe or complex injuries

 

Arthroscopic Ligament Repair

Example technique:

• Arthroscopic capsuloligamentous repair
• Sutures passed through ligament
• Tied externally
• Knot pushed back into joint

Advantages:

• Minimally invasive
• Good stabilization of scapholunate interval

 

Treatment of Advanced Perilunate Injuries

Stage III or IV Injuries

Often treated with:

• Open reduction
• Ligament repair using suture anchors
• Temporary fixation with K-wires or screws

 

Temporary Screw Fixation

Alternative to K-wire fixation.

Advantages:

• Allows early wrist mobilization
• Screws typically removed after ~3 months

 

Perilunate Fracture Dislocations (Greater Arc Injuries)

Examples include:

Trans-Scaphoid Perilunate Dislocation

Treatment:

• Scaphoid fixation (screw)
• Ligament stabilization

 

Trans-Capitate Perilunate Dislocation

Treatment:

• Capitate fixation
• Carpal stabilization

 

Trans-Radial Styloid Perilunate Injury

Treatment:

• Radial styloid fixation
• Carpal realignment

 

Complications

Early Complications

Missed Diagnosis

• One of the most common complications

Median Neuropathy

• Often improves after reduction
• Persistent symptoms ? urgent carpal tunnel release

 

Avascular Necrosis (AVN)

May affect:

• Scaphoid
• Lunate

However:

• True AVN is relatively uncommon if ligaments remain attached.

 

Late Complications

Carpal Instability

• Persistent ligament injury may lead to:
  • Scapholunate instability
  • Chronic carpal instability

 

Post-traumatic Arthritis

• Occurs in >50% of patients long term.

 

Salvage Procedures

Used for chronic or missed injuries.

Options include:

• Proximal row carpectomy
• Limited wrist fusion
• Total wrist arthrodesis

 

Key Points

• Perilunate injuries are high-energy wrist injuries.
• They are frequently missed on initial radiographs.
• Diagnosis requires careful evaluation of:
  • Gilula’s lines
  • Lunate alignment
• Early management includes:
  • Urgent closed reduction
  • Median nerve assessment
• Early surgical stabilization is usually required.
• Delay beyond 3 months often necessitates salvage procedures.