Scapholunate Instability: Evidence-based Management

Courtesy: Dr. Ahlam Arnaout, MD, Paris France

Introduction

• Scapholunate instability (SLI) is one of the most common causes of carpal instability.
• Despite extensive research, no universally accepted optimal treatment exists.
• Understanding of scapholunate pathology has evolved significantly over time.

 

Historical Concepts of Scapholunate Instability

Early Understanding

• Initial focus was on scapholunate interosseous ligament (SLIL) injury.
• SLIL described as having three parts:
  • Dorsal portion – strongest, main stabilizer.
  • Volar portion – weaker with elastic properties.
  • Intermediate portion – fibrocartilaginous, minimal biomechanical role.

Traditional Biomechanical Progression

Untreated SLIL injury leads to:

• Scapholunate dissociation
• Dorsal Intercalated Segment Instability (DISI)
• Scapholunate Advanced Collapse (SLAC wrist arthritis)

 

Early Surgical Management

Direct Ligament Repair

Techniques included:

• Open reduction and repair
• Transosseous sutures
• Anchor fixation

Limitations

• Large open approaches
• Disruption of vascularity
• Anchor loosening or intra-articular migration
• Poor long-term outcomes

 

Tendon Reconstruction Techniques

Developed to replace ligament function.

Common techniques included:

• Three-Ligament Tenodesis (Garcia-Elias technique)
• Brunelli procedure
• Dorsal capsulodesis

Indications

• Irreparable SL ligament tears
• Reducible scapholunate gap
• No degenerative arthritis

Outcomes

• Good pain relief
• Variable functional recovery
• Limited reliability in long-term stability

 

Limitations of Tendon Reconstruction

Major questions raised:

• Can a tendon truly function as a ligament?
• Will it develop proprioceptive mechanoreceptors?
• Can it withstand complex wrist biomechanical forces?

These concerns prompted rethinking of scapholunate biomechanics.

 

 

 

Modern Understanding: Scapholunate Complex

Key Concept

Stability depends on the Scapholunate Complex, not just the SL ligament.

This complex includes:

Intrinsic Structures

• Scapholunate interosseous ligament

Extrinsic Ligaments

• Dorsal intercarpal ligament (DIC)
• Dorsal capsulo-scapholunate septum (DCSS)
• Radioscaphocapitate ligament
• Long radiolunate ligament
• Short radiolunate ligament
• Scaphotrapeziotrapezoid ligament

 

Dorsal Capsulo-Scapholunate Septum (DCSS)

Anatomy

• Connects:
  • Dorsal capsule
  • Dorsal SL ligament
  • Dorsal intercarpal ligament

Functional Role

• Provides secondary stabilization
• Contains:
  • Blood supply
  • Proprioceptive receptors

Clinical Significance

• DCSS injury can cause dynamic scapholunate instability, even with intact SL ligament.

 

Role of Dorsal Intercarpal Ligament (DIC)

Anatomy

• Runs from triquetrum to scaphoid/trapezium region.

Key Function

• Major stabilizer of the scapholunate complex.

Biomechanical Findings

• Sectioning DIC ? significant SL instability
• Particularly important portion:

Dorsal scaphotriquetral ligament

 

Role of Proprioception

Research (Hagert et al.) highlights:

• Wrist stability involves sensorimotor control
• Mechanoreceptors exist in:
  • DCSS
  • Dorsal capsule
  • Extrinsic ligaments

Important Dynamic Stabilizers

• Flexor carpi radialis (FCR)
• Forearm muscle reflex loops
• Posterior interosseous nerve input

 

Modern Classification Systems

Arthroscopic Classification (Gold Standard)

Geissler Classification

Four stages based on arthroscopic instability.

EWAS Classification

Stages 0–4

Stages represent:

• Dynamic instability
• Partial ligament injury
• Complete ligament disruption
• Static instability

 

Current Philosophy of Treatment

Modern concept:

Treat Scapholunate Instability – not just SL ligament tears.

Treatment should address:

• DCSS
• Dorsal SL ligament
• Dorsal intercarpal ligament
• Extrinsic ligament complex

 

Role of Wrist Arthroscopy

Arthroscopy is considered the gold standard because it:

• Allows dynamic evaluation
• Determines stage of instability
• Guides intraoperative treatment decision
• Minimizes soft-tissue disruption

 

Modern Surgical Options

Open Reconstruction

ANAFAB Technique

• Hybrid synthetic tendon reconstruction
• Bone tunnels through:
  • Trapezium
  • Scaphoid
  • Lunate
  • Radius

Targets:

• Dorsal SL ligament
• DCSS
• Extrinsic ligaments

Limitations:

• Large dissection
• Limited long-term data

 

Arthroscopic Reconstruction Techniques

1. PCO Box Reconstruction

• Arthroscopic-assisted technique
• Reconstructs:
  • Dorsal SL ligament
  • Volar SL ligament
  • Dorsal capsule contribution

Follow-up:

• ~48 months reported

 

2. Corella Technique

• Fully arthroscopic reconstruction
• Recreates dorsal and volar SL ligaments

Limitation:

• Does not address extrinsic ligaments (DIC)

 

3. Smiley Suture Button Technique

• Arthroscopic assisted
• Uses double suture button fixation

Reconstructs:

• DCSS
• Dorsal SL ligament
• Extrinsic stabilizers

Long-term results still pending.

 

4. Gomez Internal Brace Technique

Very promising modern approach.

Features

• Arthroscopic assisted
• No tendon graft required
• Internal brace stabilization

Three Options

Option A

For stable scaphoid and lunate

Reconstructs:

• Dorsal SL ligament
• DCSS
• Volar SL ligament

Option B

For unstable scaphoid

Reconstructs:

• Dorsal SL ligament
• DCSS
• DIC
• Volar SL ligament
• STT ligament

Option C

For advanced instability

Reconstructs:

• All intrinsic and extrinsic stabilizers
• Additional volar ligament reconstruction

 

Arthroscopic Dorsal Capsuloligamentous Repair (ADCLR)

Developed by Mathoulin.

Concept

Capsule-to-ligament repair stabilizes SL complex.

Analogy:

• Capsule acts like plate
• Ligament acts like bone

 

Indications

• Dynamic SL instability
• Partial ligament tears
• Reducible instability

 

Surgical Steps

1. Arthroscopic evaluation of SL ligament
2. Assessment of DCSS
3. Midcarpal instability testing
4. Suturing dorsal capsule to ligament remnant
5. Knot tying extra-articularly

 

 

Structures Addressed

• Dorsal SL ligament
• DCSS
• Partial support of extrinsic ligaments

 

Modified ADCLR Techniques

Variants include:

Anchor-Assisted Repair

Used when ligament remnant absent.

K-wire Assisted Reduction

For difficult SL reduction.

Large ADCLR

Targets:

• Dorsal SL ligament
• DCSS
• DIC
• Extrinsic ligament complex

 

Postoperative Protocol

• Immobilization: 6 weeks
• If K-wires used: 8 weeks
• Rehabilitation focuses on:
  • Proprioception training
  • FCR strengthening
• Avoid early stretching exercises.

 

Outcomes of ADCLR

Published data:

• 800 cases reported

• Good outcomes in:
  • Pain relief
  • Range of motion
  • Grip strength

Return to work:

• Average 9 weeks

Athletes:

• Return to sport at same level

 

Evidence-Based Treatment Algorithm (2023)

EWAS Stage 1

Dynamic instability

Treatment:

• Immobilization (6 weeks)

 

EWAS Stage 2–3

Partial instability

Treatment:

• Arthroscopic dorsal capsular repair (ADCLR)
• Arthroscopic pinning in acute cases

 

EWAS Stage 3C

Complete ligament injury

Treatment:

• Large ADCLR
• Arthroscopic reconstruction

 

EWAS Stage 4

Advanced instability

Treatment options:

• Arthroscopic reconstruction
• Open reconstruction
• Salvage procedures

 

Distal Radius Fracture with SL Widening

Current evidence suggests:

• Stage <3 instability ? treat distal radius fracture only
• SL gap may heal spontaneously

For advanced instability:

• Arthroscopic repair or stabilization may be required.

 

Key Advantages of Arthroscopic Surgery

• Minimal soft tissue damage
• Preserves vascularity
• Preserves proprioception
• Less postoperative stiffness

 

Future Directions

Ideal procedure should:

• Be arthroscopic
• Address:
  • DCSS
  • Dorsal SL ligament
  • Dorsal intercarpal ligament
• Preserve biomechanics and proprioception.

Currently:

• No single procedure satisfies all criteria.