ORTHOTIC SYSTEMS

Ankle-Foot Orthoses (AFOs)

ORTHOTIC PRINCIPLES

An Orthosis is an external device with specialized functions that acts upon the musculo-skeletal system.

Orthotics is the field of study concerned with the design, fabrication and application of such devices

Description

ORTHOTIC PRINCIPLES

Orthoses are described or referred to by the joints or regions they encompass

The major joints (Hip, Knee, Ankle, etc.) are combined in various ways along with the ending Orthosis to designate a particular orthosis

Commonly the first letters of the joint names are combined to form acronyms (KAFO, AFO,KO, etc.)

Terminology

ORTHOTIC PRINCIPLES

Substitution and/or enhancement of motor function

Control of joint alignment in sagittal and frontal planes

Immobilization and protection of affected areas

Functions

ORTHOTIC PRINCIPLES

3-point force systems Reduction in

unwanted angular rotation

Stabilization about a joint, bone or skeletal segment

ORTHOTIC PRINCIPLES

3-point force systems Reduction in

unwanted angular rotation

Stabilization about a joint, bone or skeletal segment

ORTHOTIC PRINCIPLES

Lever systems and rotation Momentum

generated by push-off of contralateral limb

Forward motion generated by rotation of lever system

Heel Lever

Toe LeverCenter of Gravity (Body Weight)

CG

Axis of rotation

ORTHOTIC PRINCIPLES

Lever systems and rotation Momentum

generated by push-off of contralateral limb

Forward motion generated by rotation of lever system

CG

ORTHOTIC PRINCIPLES

Lever systems and rotation Momentum

generated by push-off of contralateral limb

Forward motion generated by rotation of lever system

Axis of rotation

ORTHOTIC PRINCIPLES

Lever systems and rotation Momentum

generated by push-off of contralateral limb

Forward motion generated by rotation of lever system

Axis of rotation

ORTHOTIC PRINCIPLES Lever systems and

rotation Momentum

diminished by resistance of ipsilateral forefoot

Backward motion generated by rotation of lever system

Center of Gravity (Body Weight)

CG

Axis of rotation

ORTHOTIC PRINCIPLES Lever systems and

rotation Momentum

diminished by resistance of ipsilateral forefoot

Backward motion generated by rotation of lever system Axis of

rotation

ORTHOTIC PRINCIPLES Lever systems and

rotation Momentum

diminished by resistance of ipsilateral forefoot

Backward motion generated by rotation of lever system Axis of

rotation

ORTHOTIC SYSTEMS

Ankle-Foot Orthoses (AFOs) Indications

Substitute for/enhance weak or absent dorsi/plantar flexors

Stabilize foot/ankle in coronal and sagittal planes

Provide some knee stability in sagittal plane

Ankle-Foot Orthoses (AFOs)

Metal Plastic

Metal AFO

Indications Wide fluctuaton

in edema At-risk foot

(absent or diminished sensation w/edema, visual inpairment, etc.)

Metal AFO

Uprights Aluminum -

lightweight Stainless Steel -

strong

Metal AFO

Stirrups Solid - stability Split – shoe

change

Metal AFO

Ankle Joints Free Motion

Metal AFO

Ankle Joints Dorsi-flexion

Assist

Metal AFO

Ankle Joints Double-action

Metal AFO

Auxillary Controls Varus/Valgus

Control Strap Controls varus

or valgus of rearfoot during weight-bearing

Metal AFO

Auxillary Controls Laminated

Footplate

Metal AFO

Auxillary Controls Pre-tibial Shell

Fitting Criteria for Metal AFOs Height

Top of calf no less than 1 1/8” below fibular head

Width (A) – Calf band is of

sufficient width to control tibia in frontal plane yet not cause undue pressure

(B) – Uprights follow contours of M&L calf outline with >1/4” clearance from skin

(C) – Ankle joints are spaced>3/8” & 1/4” from M&L malleoli, respectively

A

B

C

Metal AFO Considerations If the orthosis is articulated then insure that the orthotic

ankle joint axis is aligned with the anatomical ankle joints

Plantar and/or dorsiflexion stops should be adjusted equally within medial and lateral ankle joints

Uprights should be situated mid-line on M&L sides of lower leg; calf band should be deep enough to allow this

If patient supplies own shoes insure that they fit well before attaching orthosis

Check skin integrity (esp. at calf band, ankle joints and shoe) after 1/2 hr. of use. If there are no problems resume use, checking every 4 hours for the first few days

Plastic AFOs (PAFOs)

Plastic AFOs (PAFOs)

Solid One-piece with no separate components;

rigidity determined by thickness and shape

Articulated Incorporates ankle joints and other

components to allow controlled ROM

Plastic AFOs (PAFOs)

Solid Rigid

Plastic AFOs (PAFOs)

Solid Posterior

Leafspring (PLS)

Solid PAFOs

Thickness Typically

between 1/8” & 1/4”

Angle Û dorsiflexion =

Û knee flexion Û plantarflexion

= Û knee extension

Solid PAFOs Material

Polyproplyene for strength

Co-Polymer for flexibility

Cross-sectional shape determines rigidity

Flexible Solid

Articulated Plastic AFOs

Ankle Joints

Articulated Plastic AFOs

Free or limited motion

Variable motion

Articulated Plastic AFOs

Free or limited motion

DF Assist Neutral

Tamarack

Articulated Plastic AFOs

Free or limited motion

Oklahoma

Articulated Plastic AFOs

Variable Motion

Friddle VM

Articulated Plastic AFOs

Variable Motion Camber Angle

Plastic AFOs

Auxiliary Components

Plastic AFOs

Auxiliary components Posterior ROM

Components

Plantar StopDorsi-Assist

Plastic AFOs

Auxiliary components Compcore

Reinforces plastic in stress-sensitive areas

Plastic AFOs

Auxiliary components Pre-tibial shell

Enhances knee extension

PTB modifications can reduce weight bearing below

Plastic AFOs

Auxiliary components Anterior shell

Best for immobilization of foot/ankle

Plastic AFOs

Varus/valgus modifications Creates effective

3-point system to control varus/valgus

Plastic AFOs

Molded footplate Adds foot control Facilitates use of

metal AFO ankle joints

Fitting criteria for Plastic AFOs Trim Lines

Around proximal calf area shell is closely contoured

Side trim line placement determined by use although a + 3/16” gap between the orthosis and the skin is desirable to accommodate volume fluctuation

Along the foot the medial and lateral walls are high enough to control any pronation/supination

The medial and lateral distal edges terminate just proximal to the 1st and 5th metatarsal heads, respectively

Fitting criteria for Plastic AFOs Height - Top of AFO is > 1 1/8” below fibula

head Width - Proximal calf area is of sufficient

width to control tibia in frontal plane yet not cause undue pressure

Since heel height influences function of orthosis type of footwear should be determined prior to fabrication

Athletic footwear w/removable insoles and velcro straps instead of laces is preferred

Patients w/vision and/or sensory impairment require close monitoring to insure skin integrity