Creating Soft Sockets and 3D Scans from Plaster Casts

For more pictures of soft socket creation, check out the gallery.

For more pictures of creating and post-processing plaster casts, check out the gallery.

For more pictures of 3D scanning, check out the gallery.

Creating a Plaster Cast

The process of creating a plaster cast begins with Petroleum jelly is applied lightly to the residual limb, and is wrapped with water-soaked plaster bandage and the plaster was allowed to set. The negative casts were removed from the limb by carefully cutting down one side with a razor, perpendicular to a series of horizontal lines drawn in skin-marking pencil. The horizontal lines were for reference to ensure the seam of the cast can be closed and aligned properly later.

Upper Left: Kyle Reeser wraps a patient’s torso and lap in a plastic drape. Upper Middle: Water-soaked plaster bandages are wrapped around the patient’s residual limb, with a piece of rubber tubing to cut along when removing the cast later. Upper Right: Kyle Reeser wraps a patient’s residual limb with water-soaked plaster bandages. Lower Left: Rajab Hamis wraps a water-soaked plaster bandage around the patient’s residual limb, with a piece of rubber tubing to cut along when removing the cast later. Lower Middle: Water-soaked plaster bandages are wrapped around the patient’s residual limb, with a piece of rubber tubing to cut along when removing the cast later. Lower Right: Cutting the cured plaster cast with a razor blade along the underlying rubber hose.

Contours and measurements taken from the patient were sketched into the inside of the plaster cast with a skin-marking pencil, followed by skirting the cast with additional plaster bandage to make the rim of the opening even. Petroleum jelly was applied lightly to the inside of the negative cast, and a liquid plaster mixture was poured in. A metal bar was positioned within the cast, now serving as a mold, for ease of handling after the plaster positive cures and is removed from the mold. The plaster positive took approximately 45 minutes to fully cure, and was removed by cutting away the negative mold that surrounded it.

Views of a negative plaster cast of a patient’s residual limb (left limb). Note the markings in skin-marking pencil (blue).

Views of a negative plaster cast being filled with liquid plaster and a metal rod, and allowed to set. The negative plaster cast ‘mold’ is later removed to reveal a positive plaster cast.

A positive plaster cast after removal from the negative plaster cast ‘mold’, with a tack indicating the height to which more plaster should be added along the bone.

Plaster (tinted slightly blue with methylene blue) is added to the positive plaster cast in post-processing.

Creating a Soft Socket

Premia Bond contact adhesive, manufactured by: Dynamic Chemicals Ltd. (Nairobi)
Suitable for bonding leather, rubber, plastic, floor tiles, ceramic, wood, Formica, glass, metal, and textiles

1. Ensure all surfaces to be bonded are free from grease [and] dust, and are dry.
2. Apply glue to both surfaces and let it dry for 8-10 minutes.
3. Bring the two surfaces together and apply pressure to ensure a firm bond.
4. With time, the bond between the surfaces will become stronger.

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Views of the completed soft socket, wrapped with PVC leather.

3D Scanning Plaster Casts and Soft Sockets

Isaac Rukundo, director of the P&O department at HVP-Gatagara, 3D scanning a plaster cast of a patient’s residual limb.

Left: A plaster cast of a patient’s residual limb. Scanning a plaster cast yields a digital model that can be used to 3D print a form-fitting soft socket. Right: A traditionally-manufactured soft socket, formed over the plaster cast from the left panel. Scanning a soft socket yields a digital model that can be used to 3D print a matching hard socket.

Notes on 3D Scanning

Left: Roberto Postelmans using a Sense 3D scanner to scan Kyle Reeser’s hand. Right: A 3D model resulting from scanning a hand. Note the material in between the fingers of the 3D scan, a deficiency in the 3D scanner’s ability to create an accurate model to track it’s registration points on the fingers.

Takeaways

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