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Barge glue a piece of quarter-inch Bocklite on the existing pad of an RTC plate. |
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Heat and form a piece of half-inch Durafoam on the distal end of the cast to create a half-inch distal end pad. |
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Mark a posterior line on distal pad and extend that line on the inside of the pad (preferably with a pencil mark so that it can be erased at a later time). Sand an even circumference on the proximal edge of the pad and lightly sand the outside of the pad so that Solka-Floc or microballoon will bond to the pad and create a longer-lasting hold. |
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 Insert a collar on the pipe of the cast and install cast in the vertical jig. Use double-face tape to attach the inside of your distal pad to distal surface of cast. Find midlines on lateral and posterior sides of the cast and mark with a pencil. Also mark the posterior and lateral sides of the RTC plate to achieve an anterior and lateral shift of cast in relation to the RTC plate for proper stability. We use a half-inch anterior shift of socket and one-quarter inch lateral shift of socket in relation to the plate. This may vary according to the type of foot being used in the temporary prosthesis. (See figure 1.)
Once the anterior and lateral positions are found, microballoon or Solka- Floc the pad to the RTC plate as the cast sets in the vertical jig, making sure not to leave large voids where air could collect and make the bond weak. |
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• After bond has set, place a pencil mark on the cast directly above the mark on the pad. Fill in with more microballoon or Solka- Floc in voided areas as shown. (See figure 2.) |
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After this sets, place attached pad and plate on a sander and sand off excess bond. Sand perimeter to a smooth, even contour, taking into account any bulbous areas. This should result in a smooth, conical surface with a thin taper at the proximal surface and a contoured blend towards the distal end of plate. (See figure 3.) |
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Now use two-sided tape to adhere this pad back on the distal end of the cast in vertical jig recapturing the alignment by realigning the pencil marks. |
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Remove cast from the vertical jig and install upright in the laminating jig. |
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• Fill in four distal holes of the RTC plate with silicone grease. While doing this, wet a PVA cap and, when pliable enough (approximately 15 minutes), pull over the distal plate of cast down to approximately the posterior seat area. Let this dry and then trim excess PVA to approximately one inch below the distal end of cast. Pull a wet PVA bag over the cap (use three-in-one oil or a similar lubricant) to facilitate a nice, even pull of bag over cap. Apply one foot of vacuum and, using an acetone rag, wipe off excess oil from outer surface of PVA bag and cap. (See figure 4.) |
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Using a stretch tape, lay tape across holes of RTC plate on all four positions and then two vertically. Make sure that excess tape doesn’t extend over sides of distal cap and plate. |
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Use some type of flame burner and heat a nail or awl to semiglowing stage and burn holes through four hole areas. Then apply four screws (socket head cap screw size M6x10 thread) into plate holes. |
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Hex area of screws should then be filled in with silicone putty so they can be accessed more easily after lamination. |
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Every shop has its own layup, but the following is what is recommended in this technique:
• two ½ oz. Dacron sewn bags (this will benefit the practitioner in case he has to sand and relieve any inner socket areas of socket for patient at final fitting or in the future). (See figure 5.)
• 3-4” nyglass stockinette
• one fiberglass braid p 3-4” nyglass stockinette
• Outer PVA bag |
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Then laminate making sure there are no air bubbles and resin coverage is uniform. |
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Sand distal end of laminated socket just enough to expose the four screw heads at the distal end of the socket. |
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Remove distal screws. |
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Cast cut proximal socket and pull or break out plaster from socket lamination. |
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Remove RTC pad. |
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Drill a 1/8” hole through center of pad and plate on RTC side, to allow air to be evacuated out of the socket. |
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Set a four-hole male pyramid adapter against distal side of laminated socket to pencil mark the center of adapter hole unto distal socket. |
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Drill a one-eighth-inch hole through center of distal socket followed by 10/32 tap. |
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Screw a straight stainless steel barb (supplied with the Otto Bock 4R136 valve kit) into the recently tapped hole making sure not to strip it. Place a short length of vacuum tubing on the end of the barb (approximately two to three inches in length.) |
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Insert the RTC plate and pad combination back into the socket making sure the holes line up properly. |
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Place prosthesis in a limb maker’s vise, so that the distal end is at a 45 degree angle with the floor. |
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Mix epoxy and apply to distal end of socket making sure to cover the area that will be used by the fourhole male pyramid. |
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Place the four-hole male adapter on the distal end of socket and begin attaching the plate with RTC screws making sure that the pad and plate do not shift inside the socket. |
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After the epoxy sets (approximately 15 minutes), apply the Otto Bock plastic suction valve to the tubing extended out of the distal hole of adapter. Also place a rubber band around this valve to avoid clicking of valve against the socket after assembly during patient walking. |
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Level the foot and attach tube clamps with proper tube for height of patient. |
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Assemble socket onto top tube clamp with height and inspect overall prosthesis for finish. |
