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Scapholunate Instability

- Discussion: 
    - anatomy and ligamentous contraints:
           - ligaments of the wrist
           - SL interosseous ligament
    - SLD is most common and most significant ligament injury of wrist; (carpal instability);
    - risk factors: ulna minus configuation, slope of radial articular surface, and lunotriquetral coalition;

    - spectrum of injury: (increasing severity)
          - ref: Association of lesions of the scapholunate interval with arthroscopic grading of scapholunate instability via the geissler classification.
          - dynamic scapholunate instability
                 - no radiographic evidence of malalignment is present (ie dynamic deformity);
                 - diagnosis is established by dorsal S-L tenderness and positive shift test; 
                 - ref: The Role of the Flexor Carpi Radialis Muscle in Scapholunate Instability 
          - rotatory subluxation of scaphoid: 
          - scapholunate dissociation (SLD):
                 - SL ligament tear may lead to rotational dislocation of scaphoid allowing proximal pole to displace posteriorly & distal pole
                           to displace anteriorly;
                 - scaphoid inherently tends to palmar flex because of its oblique position and the loading applied thru (STT) joint;
                 - because scaphoid lacks  proximal of ligament, it will rotate around radiocaptitate ligament leading to dorsal rotary
                           subluxation of the proximal pole;
          - dorsal intercalated segment instability: (DISI)
          - scapholunate advanced collapse:
    - mechanism of injury:
          - mechanism is similar is similar to that of scaphoid frx w/ stress loading of extended carpus, except it is usually in ulnar rather
                 than radial deviation;
          - w/ a severe hyperextension injury of the wrist, there is tear of scapholunate interosseous ligament;
          - further loading causes tear of (in succession);
                 - radiocapitate ligaments;
                 - radiotriquetral ligaments;
                 - dorsal radiocarpal ligaments;
                 - lunate follows triquetrium into extension, & DISI deformity results; 

    - associated injuries:
          - simultaneous radial styloid frx is relatively common w/ carpal dislocation;
          - always consider non-displaced scaphoid frx;
    - diff dx:
          - scaphoid impaction syndrome (SIS);
          - occult ganglion cyst;
          - posterior interosseous nerve neuroma;
          - ulnar translocation:
          - physiologic scapholunate separation such as lunotriquetral coalition (compare to other hand);
          - perilunate dislocation (which has be reduced and splinted)
          - references:
                 - Is this scapholunate joint and its ligament abnormal? 
                 - Wide scapholunate joint space in lunotriquetral coalition: a normal variant?
                 - Coincident rupture of the scapholunate and lunotriquetral ligaments without perilunate dislocation: pathomechanics and management.

- Radiographic Findings: in Scapholunate Dislocation:
    - Traction radiography for the diagnosis of scapholunate ligament tears.

- Exam for Scapholunate Instability 

- Non Operative Treatment:
    - non operative treatment can only be recommended for dynamic scapholunate instability;
           - suggested measures include: activity modification, NSAIDS, and wrist splinting;
    - references:
           - Chronic asymptomatic contralateral wrist scapholunate dissociation.
           - Obvious radiographic scapholunate dissociation: X-ray the other wrist.

- Treatment Options for Acute Tears:

    - manipulation & closed pinning:
            - may correct a fresh scapholunate dissociation;
            - flex & ulnar deviate the wrist to produce lunate reduction & flexion; 
            - consider retrograde insertion of K wire thru scaphoid and out radial side of wrist, pulling K wire out radially, and then
                      advancing K wire into ulna;
            - be aware that K wire insertion may displace lunate;
            - K wire should be inserted into distal cortex of lunate, but midcarpal joint should be left free to absorb small movements;
            - scaphoid should be pinned similarly if not perfectly reduced to lunate;
                    - reduction of scaphoid is achieved w/ thumb pressure dorsally over proximal pole;
                    - avoid distraction using slow insertion under flouroscopy;
            - screw fixation:
                    - Reduction and Maintenance of Scapholunate Dissociation Using the TwinFix Screw
                    - The use of temporary screw augmentation for the treatment of scapholunate injuries.
                    - Chronic scapholunate instability treated with temporary screw fixation.
                    - Scapholunate Temporary Screw Fixation for the Treatment of Chronic Scapholunate Instability
                    - Treatment of Scaholunate Instability with Internal Screw fixation

    - acute ligament repiar: 
    - dynamic reconstruction:
            - Dynamic Repair of Scapholunate Dissociation With Dorsal Extensor Carpi Radialis Longus Tenodesis  
    - Brunelli Tenodesis :
            - Distal Tunnel Placement Improves Scaphoid Flexion With the Brunelli Tenodesis Procedure for Scapholunate Dissociation

- Treatment Options for Chronic Tears: Capsulodesis:
    - dorsal intercarpal ligament capsulodesis:
            - this technique does not tether the scaphoid to the distal radius (as does the blatt capsulodesis), the technique may
                   permit  good closure of the scapholunate gap without restricting wrist motion;
            - in the study by Slater, et al (1999), the dorsal intercarpal ligament capsulodesis reduced SLD gap formation down to 1 mm vs
                   3.7 mm using the blatt dorsal capsulodesis technique;
            - technique:
                   - 5 mm wide flap of dorsal IC ligament (triquetral-trapezoidal) is elevated off trapezoid (left attached to triquetrum);
                   - scaphoid is taken out of its flexed position (finger on the scaphoid tubercle) and the scapholunate gap is reduced;
                   - flap is then rotated down, stretched as tightly as possible, and is then attached to the distal pole of the scaphoid (about
                             3-4 mm proximal to the STT joint); 
                   - Dorsal intercarpal ligament capsulodesis for scapholunate dissociation: biomechanical analysis in a cadaver model.
    - blatt dorsal capsulodesis:
            - involves creation of a flap of wrist capsule (left attached to the radius) which is inserted onto the dorsal pole of the scaphoid;
                   - the fact that there remains a tether to the distal radius may infact be a disadvantage of this procedure;
            - can be used instead of, or in addition to, the repair of the ligament, and can be performed for chronic dynamic instability as
                   well as for chronic SLD;
            - capsulodesis keeps scaphoid from subluxating in palmar direction and corrects flexed posture of scaphoid;
            - disadvantages: fails to correct the diastasis and significantly decreases wrist ROM;
            - technique:
                   - dorsal capsular flap is left attached to radius proximally & is then subsequently inserted in distal part of the scaphoid to
                           tether distal pole dorsally;
                   - length of the dorsal capsular flap from the origin at the distal radius to the STT joint; 
    - references: 
            - Capsulodesis in reconstructive hand surgery. Dorsal capsulodesis for the unstable scaphoid and volar capsulodesis following excision of the distal ulna. 
            - Dynamic scapholunate instability: results of operative treatment with dorsal capsulodesis.  
            - Treatment of scapholunate dissociation by ligamentous repair and capsulodesis
            - Dorsal intercarpal ligament capsulodesis for chronic, static scapholunate dissociation: Clinical results 
            - Radiographic evaluation of the modified Brunelli technique versus the Blatt capsulodesis for scapholunate dissociation in a cadaver model.
            - Four-bone ligament reconstruction for treatment of chronic complete scapholunate separation
            - Long-term results of dorsal intercarpal ligament capsulodesis for the treatment of chronic scapholunate instability

    - STT fusion 
    - scapholunate fusion:
            - mentioned only to be condemned;
            - expect non union rates over 90%;
    - references:
            - Scaphocapitolunate arthrodesis
            - Scaphoid-trapezium-trapezoid fusion in the treatment of chronic scapholunate instability
            - Treatment of scapholunate dissociation. Rotatory subluxation of the scaphoid.
            - A comparison of scaphoid-trapezium-trapezoid fusion and four-bone tendon weave for scapholunate dissociation.
            - Attempted scapholunate arthrodesis for chronic scapholunate dissociation.
            - Treatment of scapholunate dissociation: preferred treatment--STT fusion vs other methods
            - Long-term follow-up of scaphoid-trapezium-trapezoid arthrodesis.
            - Evaluation of the biomechanical efficacy of limited intercarpal fusions for the treatment of scapho-lunate dissociation.

- Scapholunate Advanced Collapse (SLAC):
    - Proximal Row Carpectomy 
    - 4 Corner Fusion 
    - Wrist Fusion 
    - references 
          - Fascial implant arthroplasty for treatment of radioscaphoid degenerative disease.
          - On resection of the proximal carpal row.
          - Proximal row fusion as a solution for radiocarpal arthritis.
          - Scaphoid excision and capitolunate arthrodesis for radioscaphoid arthritis.
          - Treatment of scapholunate dissociation by ligamentous repair and capsulodesis.
          - Radio-scapho-lunate partial wrist arthrodesis following comminuted fractures of the distal radius.

Symposium--Progress in Sports Medicine: Athletic Injuries of the *Wrist.*

Dorsal intercarpal ligament capsulodesis for scapholunate dissociation: biochemical analysis in a cadaver model

Scapholunate Stabilization With Dynamic Extensor Carpi Radialis Longus Tendon Transfer

Proximal row carpectomy for scapholunate dissociation