Materials Used in Prosthetic and Orthotic Construction

Prosthetic and orthotic devices are built from a range of materials selected to balance strength, weight, stiffness, durability, formability and skin compatibility. They include thermoplastics that can be moulded to body contours, fibre-reinforced composites such as carbon fibre that are strong and light, metals for structural and modular components, and soft polymers and silicones used at the interface with skin. The choice of material shapes how a device feels, performs and lasts.

Definition

Materials used in prosthetic and orthotic construction are the structural, interface and biocompatible materials, including thermoplastics, fibre-reinforced composites, metals, and soft polymers and silicones, from which external assistive devices and their components are fabricated.

Scope

This topic surveys the principal material classes used in prosthetics and orthotics and the properties that drive their selection. It treats materials as a reference subject for understanding device design and is not a fabrication procedure, a product endorsement, or clinical guidance on choosing a device for an individual.

Core questions

• Which material classes are used in prosthetic and orthotic devices and for what roles?
• What properties, such as strength-to-weight ratio, stiffness, fatigue resistance and skin compatibility, govern material choice?
• How do interface materials differ from structural materials?
• How are material trade-offs balanced in device design?

Key concepts

• Biocompatibility
• Thermoplastics
• Fibre-reinforced composites (carbon fibre)
• Strength-to-weight ratio
• Stiffness and flexibility
• Fatigue and durability
• Interface materials (silicone, foams, gels)

Mechanisms

Material selection follows the functional demands of each part of a device. Structural components must carry repeated body-weight loading without failing, which favours high strength-to-weight materials such as carbon-fibre composites, titanium and aluminium alloys. Thermoplastics soften when heated and can be vacuum-formed over a cast or model, allowing custom shaping of sockets and orthoses. Materials at the skin interface, such as silicones, gels and foams, are chosen to be compliant and skin-compatible so they cushion and distribute load. Biocompatibility, fatigue resistance and the way stiffness is distributed across a structure together determine comfort, performance and service life.

Clinical relevance

Knowing the properties and trade-offs of device materials helps clinicians and engineers reason about why a device is comfortable or durable and how material choices relate to function. This entry is descriptive reference material about materials and their properties; it does not recommend specific products or guide device selection for individual patients.

Evidence & guidelines

Much of the evidence base consists of engineering and materials studies and narrative reviews rather than clinical trials. Reviews of polymer-based and additively manufactured materials describe how the field is shifting toward lighter, more customizable polymers and composites, while systematic reviews of prosthetic components note that linking material or component choices to functional outcomes is methodologically challenging.

History

Early prostheses and orthoses were made largely from wood, leather and metal. The introduction of plastics and thermoplastics in the mid-twentieth century allowed lighter, mouldable devices, and the later adoption of carbon-fibre composites brought high strength at low weight, enabling dynamic components such as energy-storing feet. Soft silicones and gels for the limb interface and, more recently, polymers tailored for additive manufacturing have continued to expand the material palette.

Seminal works

• bowker-michael-1992
• sakib-2023

Frequently asked questions

Why is carbon fibre common in prosthetics?

Carbon-fibre composites offer a high strength-to-weight ratio and can store and return elastic energy, which makes them useful for structural components and for dynamic devices such as energy-storing prosthetic feet.

Why are thermoplastics used for sockets and orthoses?

Thermoplastics soften when heated and can be moulded over a model of the body, allowing a custom-fitted shape, and they can be reheated and adjusted, which suits the iterative fitting of sockets and orthoses.