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Lunate Implant



- Discussion:
    - lunate shaped spacer implant made of silicone, vitallium, acrylic, or rolled-tendon is inserted into theresulting space to prevent migration of 
           other carpal bones;
    - due to the high rate of synovitis, most surgeons are now reluctant to use lunate implants;

- Technical Considerations:
    - dorsal approach is used, the capsular structures are preserved, distal part of the 4th compartment is incised, and EDC tendons are 
          retracted ulnarly;
    - lunate is removed piecemeal;
    - tendon spacer:
           - roll the palmaris longus overr a small portion of the excised lunate (alternatively use the ECRB);
    - artificial spacer:
           - use an absorbable suture through the prosthesis and into triquetrum, and also elevates a generous portion of the dorsal 
                  retinaculum from the extensor tendons over the fourth and fifth radial canal;
           - this is left attached to the radial border and is then sutured to dorsal surface of the scaphoid and the triquetrum;
    - it is important to reconstruct the wrist ligaments & palmar joint capsule inorder to prevent displacement of the implant;

- Hazards:
    - silicone synovitis:
           - although synovitis is seen less often w/ the lunate prosthesis as compared to the scaphoid implant, the results are still unacceptably 
                  high;
           - synovitis is more prevalent in young active patients;
           - the longer the implant is left in place, the more wear debris is present;
           - removal of the implant and debridement may not necessarily improve the silicone induced pain and limitation of motion



Kienbock's disease: the role of silicone replacement arthroplasty.

Use of a hand-carved silicone-rubber spacer for advanced Kienbock's disease.

The results of treatment of synovitis of the wrist induced by particles of silicone debris.