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Surgical Treatment of Scaphoid Frx

- Discussion:
    - primary internal fixation is treatment of choice for unstable scaphoid frxs;
    - frx treated by primary internal fixation, avg time for return to work is 3.7 wks w/ union rate, 97 %;
            - this compares very favorably with conservative treatment;
    - indications for surgery:
            - main indication is an unstable scaphoid frx as seen on x-ray or CT scan;
            - displacment > 1 mm;
            - radiolunate angle > 15 degrees;
            - scapholunate > 60 degrees;
    - implants:
            - Herbert Screw
            - 3.5 mm Cannulated Screw Insertion:
            - relative fixation strength: (from Toby, et al (1997));
                  - volar comminution of the scaphoid is a major risk factor for hardware failure;
                  - AO screw, Acutrak screw, and the Herbert-Whipple screw have superior reistance to cyclic bending loads compared to the Herbert screw;
                   - A comparison of fixation screws for the scaphoid during application of cyclical bending loads.             
                   - Anthropometry of the Human Scaphoid 
    - preoperative considerations:
            - note that a dorsal humpback malunion is possible even with surgical fixation, and that even w/ small degrees of malunion will result in a significant loss of wrist extension;
            - fracture is exposed using an anterior approach;
            - w/ dislocation of the midcarpal joint, an attempt should be made to reduce this by closed manipulation before draping;
            - if dislocation is unstable, or if there are signs of median nerve compression, a more extensive exposure is used:
            - in complex frx-dislocations, it may be necessary to make dorsal as well as a volar approach to the carpus;
            - flexor retinaculum is completely divided and the midcarpal joint approached through the floor of the carpal tunnel;
    - outcomes of surgical treatment of scaphoid fracture

- Incision and Exposure:    
    - tubercle of scaphoid is palpated distal to lower visible or palpable end of FCR;
    - skin incision is centered over scaphoid tubercle and curved distally into thenar base;
           - made proximally from tubercle for 3 cm, between tendon of FCR medially & radial artery laterally;
    - incision is carried down between tendon of FCR & radial artery;
           - radial artery & its palmar branch are on radial side of FCR;
           - median nerve & its palmar branch are on ulnar side of the tendon;
    - scaphoid is then approached thru separate longitudinal incision in capsule on radial side of FRC tendon;
           - some surgeons prefer to longitudinally incise thru the dorsal bed of the FCR sheath;
           - w/ acute frx, expect hemarthrosis in both the radiocarpal and the distal scaphoid joints, making the use of a fine sucker essential;
           - distal scaphoid is exposed by making a transverse incision at the STT joint;
    - alternate incision:
           - may be indicate for extreme humpback deformities or radio-scaphoid impingement;
           - consider using the interval between the radial artery and first extensor compartment (on the volar side) and the EPL (on the dorsal side);
    - key to exposing the scaphoid lies in dorsiflexion of wrist and axial traction on the thumb;
           - this will expose the proximal pole of scaphoid, which is site of most cases of nonunion;
    - avoid dividing the the radioscaphoid capitate ligament;
           - preservation of the radioscaphoid ligament maintains the proximal pole of the scaphoid in a reduced position in the fossa of the distal part of the radius;
                    - w/ division of the radioscaphoid ligament is divided, the proximal pole may translate in a volar direction, complicating the reduction;


- Debridment:
    - in cases of non-union use curets or highspeed burr to debride the non union site of fibrous tissue, while taking care not to damage the outer cortical shell;
    - alternatively consider using a 3 mm oscillating saw inorder to cut the scaphoid back to bleeding bone;
- Reduction:
    - consider using dental picks to manipulate the frx fragments into reduction;
    - K wires can be inserted perpendicular to the frx fragments inorder to "joystick" them into  reduction, but this may cause further comminution;
    - in cases of scaphoid humback deformity the lunate should be reduced before correcting the scaphoid deformity;
           - the lunate should be reduced back to a neutral position by pinning it to the radius;
           - note that even a small humpback deformity will leave the patient with restricted dorsiflexion;
    - if the reduction is difficult, articular border of the scaphoid with the capitate can be used as a "mold" inorder to realign the fractured scaphoid;

- Guide Wire Insertion:
    - the key to proper guide wire insertion is good visualization of the scaphoid;
    - insert a freer elevator along the proximal-radial aspect of the scaphoid (into the radial-carpal joint), inorder to allow a lateral view of the scaphoid;
    - in many cases, the guide wire will be inserted too volarly and is not directed adequately to the distal-ulnar tip of the scaphoid;
    - consider using a rongeur to remove a small portion of the non articulating portion of the trapezium inorder to allow a more dorsal insertion of the guide wire;
          -  A Comparison of 2 Methods for Scaphoid Central Screw Placement From a Volar Approach
    - stabilizing guide wire:
          - place a guide wire along the radial border of the scaphoid to control rotation;
          - once this guide wire is in place, wrist can be ulnarly deviated to better expose the scaphoid body for wire insertion down the central third of proximal pole;
          - Trumble, et al (1996), left the second stabilizing K wire in place for 6-8 weeks postop;
    - cannulated screw guide wire:
          - as pointed out by Trumble, et al (1996), the key to a successful result is placement of the guide wire in the central third of the proximal pole of the scaphoid;
          - these authors emphasized that the guide wire needs to be placed in the central third of the proximal scaphoid on both PA, lateral, and oblique radiographs;
          - Non-union of the scaphoid. Treatment with cannulated screws compared with treatment with Herbert screws.
          - Pronated Oblique View in Assessing Proximal Scaphoid Articular Cannulated Screw Penetration 



- Wound Closure:
     - when performing a volar approach, radioscaphocapitate ligament and palmar radiolunate-triquetral ligament must be partially or totally divided;
            - see ligaments of the wrist;
            - if inadequately repaired, the natural tendency of the lunate to extend and the scaphoid to flex under axial compression may lead to a DISI deformity;

- Post Op Care:
    - even w/ ORIF many recommend that immobilization be continued in short thumb-spica cast until there is evidence of frx union;
    - note that with cannulated screw fixation, average time to union is about 4 months

Dorsal approach to scaphoid nonunion.

Corticocancellous grafting and an AO/ASIF lag screw for nonunion of the scaphoid. A retrospective analysis.

Corrective osteotomy for scaphoid malunion: technique and long-term follow-up evaluation.

The Herbert screw for scaphoid fractures. A multicentre study.

Scaphoid fractures: dorsal versus volar approach.

Operative management of pediatric scaphoid fracture nonunion.

Central screw placement in percutaneous screw scaphoid fixation: a cadaveric comparison of proximal and distal techniques.