Swanson Orthotic and Prosthetic Center Swanson Orthotic and Prosthetic Center

Procedure for RapidFit™ Thermoplastic Lock Adapter Procedure For Transtibial and Transfemoral Thermoplastic Sockets with Removable RapidFit Adapter Lock Mechanism.      (RapidFit # 5012)
Swanson Regional Orthotic & Prosthetic Research Center has developed the
RapidFit Method to improve patient care for lower limb amputees.

RapidFit Overview                                     

Before you begin: Read directions completely

RapidFit # 5012 is smooth, has no undercuts and is removable
the RapidFit Adapter # 5012 and lock are removable and replaceable. 

Materials Needed: Lock, RapidFit™ Thermoplastic Lock Adapter # 5012, and Mold Sealer

Tools needed: 5mm Hex Key, 6mm Hex Key, #2 Phillips Screwdriver, Standard Screwdriver, Cast Saw

Plaster Model Preparation

  1. Take the cast over the suspension liner.
  2. Fill the cast with plaster keeping the pipe 2" from the bottom of the cast. The plaster model will have a center protrusion replicating the distal end of the suspension liner.
  3. Drill a ¼" hole straight down through the center protrusion 1 1/4" deep.
  4. Flatten the distal end of the model by removing plaster until the diameter of the distal end of the model is equal to the outer dimension of the attachment tooling. Caution: DO NOT exceed the outer dimension of the tooling, because the socket would be too short. If too much plaster was removed, add back plaster to correct.
  5. Check how the tooling is centered on distal end of the model. Any voids between the model and the tooling should be filled with plaster to create a smooth transition.
  6. Seal the plaster model using an appropriate mold sealer such as cellulose crystals dissolved in acetone.
  7. Tie a knot in the distal end of a non-stick nylon stockinette. Apply the non-stick nylon stockinette to the plaster model for a vacuum air wick. The knot should be centered on the distal end of the plaster model.
  8. Paint the distal end of the cast around the knot in the nylon with a mold sealer such as cellulose crystals dissolved in acetone. This will glue down the nylon for trimming. Let dry and trim the nylon in a circular shape slightly smaller than the lock mechanism.
  9. Fasten the attachment tooling with the four long nails provided with the RapidFit Adapter. NOTE: Using the longer nails provided in the RapidFit Adapter Kit will provide a more secure attachment.

Lock Preparation

  1. Read the lock manufacturer's directions for preparing the lock for attachment to the plaster model. Remove the lock cartridge from the lock mechanism. Install and tighten the round fabrication sleeve with a standard screwdriver. Fill in the screwdriver slot on the round fabrication sleeve with (Fillauer) fitting gel or clay putty.
  2. Attach the lock to the RapidFit Lock Adapter with the six screws. Note: the 6 x 3/8" stainless steel sheet metal screws are used with the Delrin lock bodies and the socket head cap screws are used with metal bodies. Use a #2 Phillips Screwdriver to tighten the sheet medal screws.
  3. Install the center plug with through hole and O ring on the bottom of the RapidFit Adapter and tighten. Attach the 3/8" four-hole fabrication spacer block to the bottom of the RapidFit Lock Adapter with the four 6 mm socket head cap screws. Tighten the four screws to the spacer block with a 6mm hex key.
  4. Install the eight 5 mm hex socket set screws in the RapidFit Adapter. The setscrews should protrude 3/16" for 3/16" plastic or ¼" for ¼" plastic to the mark the location for easy removal. Tighten with a 5 mm hex key.
  5. Fill any undercuts around the lock mechanism with fitting gel or clay.
  6. Install the circular foam lock block on the lock mechanism.
  7. Fasten the Lock Mechanism with the RapidFit Lock Adapter to the plaster model using the socket head cap screw provided with the lock mechanism. The Prosthetist should check and adjust the RapidFit position for correct rotation, then tighten with hex key.
  8. Install the two-inch cotton stockinette separator over the RapidFit Adapter and cut a small hole over each setscrew and push the stockinette around the setscrew until the setscrews protrudes from the stockinette. If you are fabricating a Copolymer or Polypropylene socket for your patient to wear outside of your facility with a removable RapidFit Adapter spray four 1/16" rectangular reinforcement plates with spray adhesive such as (3M Super Spray adhesive 77) and install the plates over the four sets of setscrews for socket attachment reinforcement.
  9. Vacuum form the test socket using the blister or drape methods. For drape molding with an open non-welded seam, leave the plastic on one side of the Vivak. Place the side of the Vivak with the plastic facing up in the horizontal oven during the heat process. The oven temperature will vary 355 -360 F for about 20 minutes. The side with the plastic on it will be turned toward the cast for vacuum forming and this will act as a separator. Fastener screws will be needed to secure the plastic seam if this procedure is used.

Trimming 

  1. Let the test socket cool down. Sand off the plastic on top of the lock attachment bolt and remove the bolt with a hex key.
  2. Trim out the 3/8" four-hole spacer block. Remove the four 6 mm socket head cap screws with a 6mm hex key. Remove the four-hole spacer block.
  3. Trim out and remove the test socket from the plaster model. Sand and buff the trim lines.
  4. Sand off the plastic on top of the eight 5 mm hex socket set screws and remove screws with a 5 mm hex key.
  5. Sand off the plastic covering the round fabrication sleeve and remove it with a standard screwdriver.

Assembly

  1. Remove any fitting gel or stick wax residue from the lock body and threaded attachment holes. Follow the lock manufacturer's directions to reassemble the lock.
  2. Install and tighten the eight 5 mm socket head cap head screws and stainless steel washers to secure the attachment of the RapidFit Lock Adapter to the test socket. Tighten with a 5 mm hex key to a torque setting of 12 Nm or 9 foot pounds (Fig.11). Caution, care must be taken to use the correct length socket head cap screws provided with RapidFit Adapter so that the screws tighten properly and securely. Do not substitute these socket head cap screws.
  3. Install the other endoskeletal components according to manufacturer's directions. NOTE: A set of four 6 mm x 16 mm stainless steel flat head socket screws are provided with the RapidFit Adapter. Caution, care must be taken to use the correct length flat head screws provided with the Rapidfit Adapter so that the screws tighten properly and securely. Do not substitute these flat head screws. Apply thread lock such as Loctite 242 to the four 6mm x 16 mm stainless steel flat head socket screws and tighten to a torque setting of 12 Nm or 9 foot pounds.

Filling the Test Socket

  1. Fill the locking pinhole with fitting gel or clay in order to prevent plaster from leaking into the lock mechanism. Tape over the posterior foam contour on the inside of the socket with masking tape in order to prevent the plaster from leaking into and around the lock mechanism.
  2. Mark the location of the locking pin on the model for the fabrication of the definitive socket.

RapidFit Socket Lamination 

  1. You will need a RapidFit Lamination Lock Adapter #5022 Kit for laminated sockets. Follow the RapidFit Lamination Lock Adapter directions.
 

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