Summary Scapholunate Ligament Injury is a source of dorsoradial wrist pain with chronic injuries leading to a form of wrist instability (DISI deformity). Diagnosis is made with PA wrist radiographs showing widening of the SL joint. Diagnosis of DISI deformity can be made with lateral wrist radiographs showing a scapholunate angle > 70 degrees. Treatment of acute SL ligament injuries may be immobilization versus operative repair/reconstruction depending on degree of displacement. Chronic DISI deformities may be indicated for fusion procedures depending on degree of arthritis and patient symptoms. 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 Anatomic location ligament has 3 components that span between the scaphoid and lunate bones dorsal, proximal and volar components incomplete tears > complete tears Etiology 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 deformity may also develop secondary to distal pole of the scaphoid excision for treatment of STT arthritis DISI is a form of carpal instability dissociative Anatomy Scapholunate interosseous ligament location c-shaped structure connecting the dorsal, proximal and volar surfaces of the scaphoid and lunate bones dorsal fibers thickened (3 mm) compared to volar fibers (1 mm) and considered most important for stability biomechanics dorsal component provides the greatest constraint to translation between the scaphoid and lunate bones proximal fibers have minimal mechanical strength Overview of wrist ligaments and biomechanics 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 subluxates the scaphoid dorsally out of the scaphoid fossa of the distal radius, and a clunk is palpated when pressure is released as the scaphoid reduces back over the dorsal rim of the radius a painful clunk during this maneuver may indicate insufficiency of scapholunate ligament Imaging Radiographs recommended views AP and lateral views of the wrist additional views radial and ulnar deviation views flexion and extension views clenched fist (can exaggerate the diastasis) findings AP radiographs SL gap > 3mm with clenched fist view (Terry Thomas sign) cortical ring sign (caused by scaphoid malalignment) humpback deformity with DISI associated with an unstable scaphoid fracture scaphoid shortening Lateral radiographs dorsal tilt of lunate leads to SL angle > 70° on neutral rotation lateral capitolunate angle > 20° DISI normal carpal alignment increased SL angle Arthrography indications may be used as screening tool for arthroscopy views radiocarpal and midcarpal views always assess the contralateral wrist for comparison findings may demonstrate the presence of a tear but cannot determine the size of the tear positive finding of a tear may indicate the need for wrist arthroscopy MRI indications often overused as a screening modality for SLIL tears findings requires careful inspection of the SLIL by a dedicated radiologist to confirm diagnosis low sensitivity for tears Arthroscopy indications considered the gold standard for diagnosis Differential LT ligament injury & VISI deformity Carpal instability nondissociative (CIND) Treatment Nonoperative NSAIDS, rest +/- immobilization indications acute, undisplaced SLIL injuries chronic, asymptomatic tears technique splinting and close follow-up with repeat imaging and clinical response with acute injuries outcomes most people feel casting alone is insufficient may be effective with incomplete tears Operative scapholunate ligament repair indications acute scapholunate ligament injury without carpal malalignment chronic but reducible scapholunate ligament injuries (can peform if < 18 months from the time of injury) ligament pathoanatomy is ammenable to repair scapholunate reconstruction indications acute scapholunate ligament injury without carpal malalignment where pathoanatomy is not ammenable to repair reducible scapholunate ligament injuries > 18 months from the time of injury scaphoid ORIF vs. CRPP (+/- arthroscopic assistance) indications if pathoanatomy of SL ligament injury is a scaphoid fx than repair with ORIF vs. CRPP (+/- arthroscopic assistance) stabilization with wrist fusion (STT or SLC) indications rigid and unreducible DISI deformity DISI with severe DJD technique scaphotrapezialtrapezoidal (STT) fusion scapholunocapitate (SLC) fusion scapholunate fusion alone has highest nonunion rate 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 Disease progression (e.g. SLAC wrist) Arthritis Post-operative pain, stiffness, fatigue Reduced grip strength