SL LIGAMENT INJURY AND DISI Flashcards
DISI definition
Form of CID associated with dysfunction of SLIL
Results in imbalance between SL and LT ligaments
Dorsiflexion of lunate
Anatomy of the scapholunate interosseous ligament
C-shaped structure with dorsal, proximal, volar parts
Dorsal part thickest and strongest
Proximal/ membranous and volar parts thin
Role in stability and proprioception = high concentration of mechanoreceptors like ACL
Prerequisites for development of DISI and SLAC
Secondary stabilisers must be defunctioned
Secondary stabilisers:
1. Volar RSC ligament
2. DIC (scapho-trapezio-triquetral) ligament
< 10% of SL ligament injuries progress to DISI and SLAC
Aetiology of SL ligament injury
Traumatic vs. atraumatic
Traumatic = FOOSH with wrist in extension/ ulnar deviation/ carpal supination
Atraumatic
1. Inflammatory
2. Degenerative = > 50% patients over 80yrs have degenerative SLL tears
3. Infective
Watson’s test for SL instability
Dorsal pressure with thumb over scaphoid tubercle to prevent scaphoid flexion as wrist is moved from ulnar to radial deviation
Pain caused by scaphoid dislocating dorsally out of scaphoid fossa
Clunk when pressure released as scaphoid reduces
Test has low sensitivity = pain from synovitis
Test is negative in advanced stages = arthritis confers stability
2 main investigations for diagnosis of SL ligament injury
- Plain radiographs
- MRI
- low sensitivity for SL ligament tears
- dorsal coronal sections best
4 main radiographic features of SL ligament injury on PA view
- SL interval/ gap > 3mm or compare to other side
- Terry Thomas sign
- Cortical/ signet ring sign = scaphoid flexion
- Break in Gilula’s arcs
4 main radiographic features of SL ligament injury on lateral view
- SL angle > 70deg (normal = 30-60deg)
- RL angle > 15deg dorsal (normal = 0 +/- 10deg)
- CL angle > 20deg (normal = 0 +/- 15deg)
- Humpback deformity if scaphoid nonunion
Special radiographic views for SL instability
- Clenched fist view
- Dynamic (flexion-extension or radioulnar deviation) views
- Contralateral comparison views
Classification of SL ligament injury
Geissler classification = arthroscopic classification with 4 grades
Grade I = hemorrhage/ attenuation of ligament but no SL step/ gap
Grade II = hemorrhage/ attenuation of ligament with SL step but no gap
Grade III = SL gap where probe can pass through
Grade IV = SL gap where 2.7mm scope can pass through
6 stages of SL dissociation
- Stage I = pre-dynamic
- partial SL ligament injury = dorsal component intact
- secondary stabilisers intact = no malalignment - Stage II = dynamic and repairable
- repairable complete SL ligament injury
- secondary stabilisers intact = no malalignment - Stage III = dynamic and nonrepairable
- nonrepairable complete SL ligament injury
- secondary stabilisers intact = no malalignment - Stage IV = static and reducible
- complete SL ligament injury
- dysfunction of secondary stabilisers
- flexible deformity without arthritis - Stage V = static and nonreducible
- complete SL ligament injury
- dysfunction of secondary stabilisers
- fixed deformity without arthritis - Stage VI = degenerative
- complete SL ligament injury
- dysfunction of secondary stabilisers
- fixed deformity and arthritis
Indications for non-operative management of SL ligament injury
- Elderly low-demand patient
- Asymptomatic
- Partial tear
3 factors to consider with surgical management of SL ligament injury
- Acuity = repair vs. reconstruction
- Correctability = reconstruction vs. fusion
- Arthritis = excision vs. fusion vs. arthroplasty
Surgical options for SLAC wrist based on Watson stage
- Stage I = radial styloidectomy
- Stage II = scaphoid excision and 4CF/ PRC
- Stage III = scaphoid excision and 4CF/ fusion
- Stage IV = fusion
