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Prosthetic Flexor Tendon Grafts

- See: Technique of Free Tendon Grafting

- Discussion:
     - prosthetic graft serves as temporary spacer around which a pseudotendon sheath forms, & provides a healthy bed in which to place tendon autograft;
     - pulleys can be reconstructed at time of insertion of prosthesis
            - two prostheses available are passive and active tendon implants;
     - typically prosthesis remains in place for at least 3 months, after which time secondary tendon grafting can be performed;
     - indications:
            - loss of pulley system
            - extensive scaring w/ in tendon bed
            - dirty graft bed
            - presence of stiff joints: ROM must be regained after silicone elastomer rod is inserted;

- Types of Implants:
    - passive implant:
         - is attached to remaining flexor tendon (pull thru technique) or bone (1.5 mm or 2.0 mm screws) and is left unattached proximally for a distance 4-6 cm proximal to the carpal tunnel and deep to the FDS;
         - passive motion will promote the development of pseudo-sheath;
                 - implant gliding motion is obtained by active finger extension and passive flexion;
                 - proximal end of the rod must be left free proximally, otherwise the rod can rupture;
         - pulley reconstruction should be performed at the same time as insertion of passive implant;
                 - once the rod has been passed thru each pulley, taken the digit thru a full range of motion;
         - determine correct rod size:
                 - usually 4 mm rod is appropriate (Wright Medical Technology, Arlington, TN)
                 - if rods are seen to bowstring, then the pulleys are too loose;
                 - if rods are seen to buckle, then the pulleys are either too tight, or they are bunching up at the proximal end;
                        - the later is addressed by cutting the rod short and by ensuring that there is a deep enough pocket to allow rod motion;


         - in order to avoid, silicone synovitis, avoid rod contact w/ foreign bodies, such as the powder found on newly opened surgical glooves;
                 - surgical glooves should be rinsed free of gloove powder prior to contact with the silicone rod;
    - acitve rod:
         - is similar to passive rod but has a Darcon silicone loop or cords proximally to attach to the proximal motor (which is usually FDP);
         - these rods are not design to function as permanent implant;
         - ruptures are known to occur at the distal attachment site;
         - best method of attachement involves suture pull thru technique;

- Pearls
    - leave the rod out until all of the pulleys have been reconstructed;
    - next secure the rod distally (sutures or screws), and subsequently pass the rod
           from distal to proximal using a tendon passer;
           - it will be necessary to make a 2 cm transverse incision in the mid-forearm in order to insert the tendon passer from proximal to distal (inorder to pull the rod distally);
    - ensure that the rod has been passed thru each reconstructed pulleys (i.e., ensure that none of the pulleys have been missed)

- Complications:
    - silicone synovitis:
           - patient may note redness, swelling, and pain;
           - once infection has been ruled out, immbolize the hand;
           - in most cases, rod removal will not be necessary


Development of a reconstituted collagen tendon prosthesis. A preliminary implantation study.