What are orthoses (orthotic devices)?

What Are Orthoses?

Orthoses (plural of orthosis) are devices placed inside or outside the shoe to achieve pressure reduction, alter foot function, support joints, or accommodate deformity. 1

Core Definition and Purpose

Orthoses are external devices designed to:

• Achieve some alteration in the function of the foot when placed inside footwear 1
• Reduce mechanical stress (pressure) from specific regions of the foot or other body parts 1
• Support or protect injured body parts and control, guide, or limit motion of extremities, joints, or body segments 2

The term "orthosis" is singular, with "orthoses" being the correct plural form—not "orthotics," which is sometimes used loosely but technically incorrect. 1

Types of Orthoses

In-Shoe Orthoses

In-shoe (semi-)rigid orthoses are devices placed inside shoes that can be either prefabricated or custom-made to achieve pressure reduction or functional alteration. 1

• Prefabricated orthoses: "Off-the-shelf" flat or contoured devices made without reference to the patient's specific foot shape 1
• Custom-made orthoses: Devices built on a positive model of the patient's foot requiring in-depth assessment, multiple measurements, impressions or molds 1

Functional Categories

Orthotic devices are divided into three functional types 3:

1. Impact reduction and cushioning devices: Made from materials like nitrogen-filled rubber or thermoplastic foam 3
2. Pressure relief devices: Include relief areas or support adjacent to pressure points using adhesive felt, foam, custom innersoles, or pad combinations 3
3. Biomechanical correction devices: Reduce abnormal pressures and strains, allowing more normal foot function and relieving pressure areas through techniques like "posting" to position the subtalar joint neutrally 3

Clinical Applications

Thumb Base Osteoarthritis

Orthoses should be considered for symptom relief in thumb base OA, with long-term use (at least 3 months) advocated. 1, 4

• Custom-made thermoplast or neoprene orthoses show beneficial effects on pain and function when used for prolonged periods 1, 4
• Short-term use (less than 3 months) shows no evident improvements 1
• Well-fitted, preferably custom-made orthoses by specialized health professionals improve compliance and long-term use 1

Ankle-Foot Orthoses (AFOs)

AFOs should be used for ankle instability or dorsiflexor weakness in stroke patients, showing favorable impact on walking disability and balance. 5

• Rapidly prototyped patient-specific AFOs provide good anatomical fit while delivering comparable biomechanical function to prefabricated designs 6

Diabetic Foot Management

In-shoe orthoses play a critical role in offloading interventions to prevent and heal foot ulcers in diabetic patients, working in conjunction with specialized footwear. 1

Important Distinctions and Caveats

Orthoses provide joint stability and structural support but do not protect muscles from overstretch and may actually harm muscle function. 5

• Splinting for muscle protection can worsen symptoms through learned non-use, muscle deconditioning, and increased compensatory movement strategies 5
• Serial casting has been associated with worsening symptoms and complex regional pain syndrome in functional neurological disorders 5
• If removable splints are issued, patients must be monitored regularly and empowered to discontinue use if adverse effects occur 5

Poorly fitted or non-custom orthoses lead to poor patient compliance and reduced effectiveness, particularly in conditions requiring long-term use like thumb base OA. 4

Modern Fabrication Methods

Contemporary orthotic fabrication combines 3D laser scanning with rapid prototyping to create patient-specific devices 6:

• Digital surface data of patient anatomy is manipulated using CAD software 6
• Rapid prototyping machines fabricate the final device, potentially decreasing fabrication time and cost 6
• Custom-fit orthoses are superior to prefabricated devices for individualized comfort and function 6