Scapholunate Ligament Injury & DISI

Introduction

Scapholunate ligament is important for carpal stability
- chronic scapholunate deficiency leads to DISI (see below)
Epidemiology
- incidence
  - acute injury
    - occurs in approximately 10-30% of intra-articular distal radius fractures or carpal fractures
  - degenerative injury
    - degenerative tears in >50% of people over the age of 80 years old
- location
  - ligament has 3 components that span between the scaphoid and lunate bones
  - dorsal, proximal and volar components
  - incomplete tears > complete tears
Pathophysiology
- mechanism of injury
  - sudden impact force applied to the hand and wrist causing SLIL injury and scapholunate dissociation
  - injury occurs most commonly with wrist positioned in extension, ulnar deviation and carpal supination
- pathoanatomy
  - osseous
    - SLIL tearing will position the scaphoid in flexion and lunate extension
  - ligamentous
    - diastasis of the scapholunate complex occurs with complete SLIL tears and capsule disruption.
Associated injuries
- DISI (dorsal intercalated segmental instability)
  - scapholunate dissociation causes the scaphoid to flex palmar and the lunate to dorsiflex
  - if left untreated the DISI deformity can progress into a SLAC wrist
  - DISI is a form of carpal instability dissociative

Anatomy

Presentation

History
- acute FOOSH injury vs. degenerative rupture
  - age, nature of injury, duration since injury, degree of underlying arthritis, level of activity
Symptoms
- usually dorsal and radial-sided wrist pain
- pain increased with loading across the wrist (e.g. push up position)
- clicking or catching in the wrist
- may be associated with wrist instability or weakness
Physical exam
- inspection
  - may see swelling over the dorsal aspect of the wrist
- palpation
  - tenderness in the anatomical snuffbox or over the dorsal scapholunate interval (just distal to Lister's tubercle)
- motion
  - pain increased with extreme wrist extension and radial deviation
- provocative tests
  - Watson test
    - when deviating from ulnar to radial, pressure over volar aspect of scaphoid produces a clunk secondary to dorsal subluxation of the scaphoid over the dorsal rim of the radius
      - dorsal wrist pain or a clunk during this maneuver may indicate instability of scapholunate ligament

Imaging

Treatment

Technique

Scapholunate ligament direct repair SLIL with k-wires
- approach
  - small incision is made just distal to the radial styloid
  - care to avoid cutting the radial sensory nerve branches
- methods
  - SL joint pinning with k-wires
  - suture anchors with k-wires
  - Blatt dorsal capsulodesis
    - often added to a ligament repair and remains a viable alternative for a chronic instability when ligament repair is not feasible
- repair technique
  - place two k-wires in parallel into the scaphoid bone
  - reduce the SL joint by levering the scaphoid into extension, supination and ulnar deviation and lunate into flexion and radial deviation
  - pass the k wires into the lunate
  - confirm reduction of the SL joint under fluoroscopy
  - place patient in short arm cast
- post-operative care
  - remove k-wires in 8-10 weeks
  - no heavy labor for 4-6 months
Scapholunate ligament reconstruction
- approach
  - same as for repair
- reconstruction
  - FCR tendon transfer (direct SL joint reduction)
  - ECRB tendonosis (indirect SL joint reduction)
  - weave not recommended due to high incidence of late failure

Complications