Select an appropriate orthosis for a given clinical condition based on the patient's functional and biomechanical requirements.

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Orthosis Selection: Functional and Biomechanical Framework

Selecting an orthosis requires matching the device's mechanical properties to the patient's pathology, joint stability, sensory status, activity level, and functional goals. Below is a systematic guide by body region and condition.

Core Classification Principles

Orthoses are classified by:

Stabilization type: immobilization (rigid), stabilization (semirigid), or support (flexible/soft)
Material: thermoplastics, neoprene, fabric, foam, metal
Fabrication: custom-made vs. off-the-shelf

The fundamental principle is: rigid orthoses = immobilize/rest inflamed joints; flexible/semirigid orthoses = support while preserving function during activity - Firestein & Kelley's Textbook of Rheumatology

I. Foot Orthoses

Type	Biomechanical Property	Clinical Indication
Rigid	Limits joint motion; stabilizes	Flexible deformities (pes planus, posterior tibial tendon dysfunction)
Semirigid	Support + shock absorption	Active patients; mild-to-moderate malalignment; plantar fasciitis
Soft/Accommodative	Maximum shock absorption; offloads pressure	Rigid/fixed deformities; neuropathic/diabetic foot; dysvascular or ulcerative conditions; RA/JIA foot pain

Functional orthotics (rigid/semirigid thermoplastic shells with built-in corrections) control abnormal foot motion and are used for flexible deformities - correction is the goal.

Accommodative orthotics (soft foam, cork, silicone) protect painful plantar lesions and bony prominences; used when the deformity is fixed and cannot be corrected - accommodation is the goal.

Specific indications for custom rigid orthotics include plantar fasciitis (with or without heel spur), pes cavus, hallux valgus, metatarsalgia, sesamoiditis, and rearfoot pain from RA. Most patients (70%) are heel strikers; orthotics redistribute this load across the first and fifth MTP joints. - Pfenninger & Fowler's Procedures for Primary Care

II. Ankle-Foot Orthosis (AFO)

The most commonly prescribed lower limb orthosis. Extends from below knee to foot.

Clinical Scenario	AFO Selection
Foot drop (peroneal nerve palsy, stroke)	Posterior leaf spring AFO or solid AFO; spring-assisted dorsiflexion assist
Plantar spasticity (stroke, CP, TBI)	Solid/rigid AFO; controls equinus posture
Spinal cord injury	Rigid AFO; mediolateral stability with TPE trimlines
Hindfoot fusion	AFO to absorb ground reaction force (GRF), protect fusion sites and midfoot
Active ankle motion preserved	Articulating AFO with mechanical ankle joint; allows ROM while providing mediolateral control

Trimline selection for thermoplastic elastomer (TPE) AFOs:

Full/anterior trimline = maximum mediolateral control
Posterior trimline = less control, more flexibility
Choice depends on intended function, level of control needed, limb sensation, and swelling

Key factor: the AFO's biomechanical effect on the knee joint must be considered. A rigid AFO can create a knee-extension moment (useful in quadriceps weakness) or a knee-flexion moment depending on the ankle angle set. - Miller's Review of Orthopaedics 9th Ed.

III. Knee-Ankle-Foot Orthosis (KAFO)

Used to control an unstable knee joint (mediolateral instability, quadriceps weakness, post-polio, muscular dystrophy).

Provides mediolateral stability with prescribed flexion or extension control
Knee locks of various types (drop lock, bail lock, offset knee joint) tailor the degree of stability
Knee orthoses (subset): used for knee OA (unloader braces to offload medial/lateral compartment), patellofemoral syndrome (patellar tracking braces), or ACL-deficient knee (functional hinged brace)
ACR guidelines conditionally recommend orthoses for both tibiofemoral and patellofemoral knee OA

IV. Hip-Knee-Ankle-Foot Orthosis (HKAFO)

Provides hip and pelvic stability
Rarely used by adult paraplegics due to high energy cost and cumbersome nature
Primary current use: children with upper lumbar myelomeningocele (L1-L2); reciprocating gait orthosis (RGO) designs allow ambulation using the hip-hip linkage mechanism

V. Upper Limb Orthoses

Wrist-Hand Orthosis (WHO)

Orthotic devices for rheumatic conditions: (A) rigid thermoplastic CMC orthosis; (B) neoprene hybrid CMC brace; (C) custom foot orthosis with medial arch support

Custom orthotic devices - (A) rigid forearm-based resting orthosis (thermoplastic); (B) neoprene hybrid palmar orthosis for CMC joint; (C) custom foot orthosis. From Firestein & Kelley's Textbook of Rheumatology.

Condition	Orthosis Type
RA with active inflammation	Rigid immobilization wrist/hand orthosis; promotes optimal alignment during flares
Thumb CMC OA	Rigid or hybrid CMC orthosis (ACR/EULAR recommended); longer forearm-based design for acute phase; shorter hand-based design for functional tasks
Carpal tunnel syndrome	Neutral wrist splint at 0-10° extension at night (caution: standard 30° extension splints may worsen RA patients if active wrist synovitis is present)
Cervical quadriplegia (C6-C7)	Wrist-driven hand orthosis (tenodesis splint); uses tenodesis action for grasp/release; may be motor-driven
Postoperative/reconstructive	Static, static-progressive, or dynamic WHO depending on phase

Elbow Orthoses

Condition	Orthosis
Ligament instability	Hinged-elbow orthosis (minimum stability)
Flexion/extension contracture	Dynamic spring-loaded orthosis
Lateral epicondylitis (tennis elbow)	Counterforce elbow strap (applied ~3 cm distal to lateral epicondyle)
Cubital tunnel syndrome	Long arm splint with elbow at 45° flexion

The opponens splint prepositions the thumb for pinch/grasp but impairs tactile sensation - important consideration in sensory-dependent tasks. - Miller's Review of Orthopaedics 9th Ed.

VI. Spine Orthoses

Cervical Spine

Orthosis	Immobilization Level	Indication
Soft collar	Minimal	Sprains, strains, transient process fractures; activity reminder; transitional weaning
Philadelphia collar (foam)	Moderate	Stable fractures; good for hygiene
Miami J collar (rigid plastic)	Moderate-high	Stable cervical fractures; popular due to comfort and demonstrated rigidity
Cervicothoracic orthosis (CTO) (Minerva, Yale, SOMI)	High	Fractures at cervicothoracic junction; restricts ~79-87% sagittal motion, 75-77% axial rotation
Halo-vest	Maximum	Unstable cervical fractures (e.g., odontoid type II, C1 ring fracture)

Cervical orthoses use three-point pressure (occiput/mandible proximally; clavicle/sternal notch anteroinferiorly; upper thoracic spinous processes posteriorly). They decrease - but do not eliminate - motion. Complications with prolonged collar use include pressure ulcers (up to 38% in severe TBI), dysphagia, aspiration risk, and raised intracranial pressure. - Rockwood & Green's Fractures in Adults 10th Ed.

Thoracolumbar Spine

Orthoses achieve control through three-point pressure mechanisms and by increasing intra-abdominal/body cavity pressure
Lever arm length determines the extent of motion limitation
TLSO (thoracolumbar sacral orthosis): used for thoracolumbar fractures, scoliosis (Milwaukee brace, Boston brace), and postsurgical stabilization
LSO (lumbar sacral orthosis): used for mechanical back pain, lumbar fractures, and post-discectomy support

VII. Pediatric Orthoses

Condition	Orthosis	Mechanism
Developmental dysplasia of the hip (DDH)	Pavlik harness	Maintains hip in flexion-abduction; allows dynamic motion; mainstay treatment in infants
Perthes disease	Dynamic containment orthoses (Scottish Rite, Atlanta brace)	Maintains femoral head within acetabulum during revascularization
Scoliosis (10-45°, skeletally immature)	Boston/Milwaukee TLSO	Three-point correction; worn 16-23 hrs/day; reduces curve progression
Myelomeningocele (L1-L2)	HKAFO with reciprocating gait mechanism	Enables upright ambulation using hip extension-flexion coupling

VIII. Fracture Braces

Situation	Device
Isolated tibia-fibula fractures	Fracture brace (functional bracing - Sarmiento principle)
Simple foot/ankle fractures, ankle sprains	Prefabricated fracture orthosis / walking boot
Simple hand injuries	Prefabricated hand orthosis

Decision Framework Summary

Step 1: What is the primary goal?
  ├─ REST / immobilize inflamed joint → Rigid orthosis
  ├─ SUPPORT unstable joint during function → Semirigid/hinged orthosis
  ├─ ACCOMMODATE fixed deformity / protect tissue → Soft/accommodative orthosis
  ├─ CORRECT flexible deformity → Functional orthosis (rigid/semirigid with posting)
  └─ ASSIST weak muscle / substitute movement → Dynamic/tenodesis orthosis

Step 2: Check patient-specific factors
  - Sensory status (neuropathy → soft/accommodative)
  - Vascular status (SSc, PVD → avoid compressive rigid devices)
  - Active inflammation vs. mechanical instability
  - Comorbidities (swelling, skin integrity)
  - Functional demands (ADLs vs. ambulation vs. sport)

Step 3: Select material
  - Rigid thermoplastic → maximum correction/immobilization
  - Semirigid TPE → moderate control + comfort
  - Neoprene/fabric → light support, proprioception, warmth
  - Soft foam/silicone → accommodative, offloading

Key Evidence Points

Moderate-to-strong evidence supports orthoses for hand/thumb and knee OA (ACR guidelines conditionally recommend CMC orthoses for thumb OA and unloader braces for knee OA) - Firestein & Kelley's Rheumatology
Conditional evidence for rigid/compressive orthoses in RA (wrist, finger, knee, ankle, foot) - EULAR/ACR guidelines
Contraindicated in SSc: devices aimed at reducing finger contractures may impair peripheral vascular perfusion
In RA, standard carpal tunnel splints (30° wrist extension) may worsen median nerve compression if active wrist synovitis is present - prescribe at neutral (0°) instead

Sources:

Miller's Review of Orthopaedics, 9th Edition (Foot Orthoses, AFO, KAFO, HKAFO, Spine/Elbow/Wrist Orthoses)
Firestein & Kelley's Textbook of Rheumatology, 2-Volume Set (Rheumatic conditions, OA/RA/inflammatory orthoses)
Rockwood and Green's Fractures in Adults, 10th Ed. 2025 (Cervical/cervicothoracic orthoses)
Pfenninger & Fowler's Procedures for Primary Care, 3rd Ed. (Functional vs. accommodative foot orthotics)

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