LOWER LIMB ORTHOSIS

INTRODUCTION

Lower limb orthotic devices play a vital role in the field of orthopaedic and

neurological rehabilitation for the use of locomotion. They are given to improve function,

 restrict or enforce motion, or increase support to a part of the body during standing 

and walking. In India, where several adults suffer from the long term effects

of childhood poliomyelitis, orthotics are an integral part of the life of persons

with disability.

MATERIAL AND FABRICATION FOR LOWER LIMB ORTHOSIS

A wide variety of materials have been used to fabricate orthotic appliances,

among them metals like steel, aluminium and alloys, rubber, leather and

canvas. Some of them used more often recently are plastics and synthetic

fabrics.

 

Considerations while Selecting the Material

• Strength

• Durability

• Flexibility

• Weight

• Should accommodate a simple and inconspicuous design

• Comfort

• Cosmesis

• Distribution of forces over sufficiently large surface area

• Material which can be accurately contoured and padded to the body.

 

Metal: Traditional orthotic devices are made of metal while leather is used

for straps.

Plastics: They are lighter and close fitting and provide a fairly broader

distribution of forces than the metal orthosis. They are usually lined internally

with thin padding.

 

They are of two types:

• Thermo setting

• Thermo plastics

 

Thermo Setting: Plastics designed to be set after heating will not return to fit

their original consistency if reheated, but they will soften.

Thermo Plastics: Thermo plastics are plastics that are heated and moulded

to the patient. They have a capacity to return to their original shape when

dipped again in hot water. Polypropylene is more commonly used than thermo

setting plastics to make orthosis, sometimes combined with other plastics. Its

unique advantage is that it provides a close fit by heating and moulding to

the part of the patient’s body that needs orthotic fitting.

Combination of Plastic and Metal: Usually aluminium and stainless steel

uprights may be needed for heavy individuals. Lighter combinations of plastic

and metal are used for those with medium build to reduce the weight of the

orthosis.

Carbon – Graphite: It offers strength and low weight with increased durability.

 

CALIPERS

Calipers are orthosis fitted to the lower limb. They may be

• Foot orthosis (FO)

• Ankle Foot orthosis (AFO)

• Knee Ankle Foot orthosis (KAFO)

• Hip Knee Ankle Foot orthosis (HKAFO).

 

Considerations While Prescribing Calipers

Orthoses need to be prescribed, just like drugs. The specifications would

include the nature and number of joints, the positioning of the straps and

suspensions and accessory attachments to the shoe or boot. The reason for

prescribing it must be explained to the patient, else there will be rejection. It

would be good to check out the following, before delivering the orthoses.

The stability of the hip and knee should be good before deciding how high

the caliper should be. This can only be done after doing a muscle power

grading, paying special attention to the hip abductors extensors and knee

extensors. Alignment is checked whether the ankle joint is over the medial

malleoli, the knee joint over the prominence of medial femoral condyle and

the hip joint permits a patient to sit upright at 90°. The caliper should be

functional throughout all phases of gait and the static and dynamic alignment.

 

FOOT ORTHOSES (FO)

The essential difference between a shoe and a boot is that a boot covers the

malleoli, while a shoe does not. The foot orthoses is nothing but a boot that

has components like supports and wedges to manage different foot symptoms

and deformities. These modifications are made of various materials like rubber,

foam or leather.

The FO can be divided into a lower part and an upper part.

Components of the Lower Part

Sole: It is the part of the shoe in contact with the ground. The inner part of

the sole against which the foot rests is the insole. Bars straps and wedges,

which are common attachments to the foot orthoses get their leverage and

attachments through the sole and exert their forces (Fig 7.4).

Ball: Widest part of the sole that is located in the region of the metatarsal heads.

Shank: Is the narrowest part of the sole between the heel and ball. The uprights

of the AFO attach themselves to a stirrup at the shank region.

Toe Spring: It is the space between the outer sole and the floor, which helps

to produce a rocker effect during toe off phase of the gait cycle.

Heel: is the posterior part of the sole, which corresponds to the heel of the

foot. Since it is the portion where most of the body weight is taken it needs

to be resilient and thicker so that it can prevent shoe components from “wearing

out” and shift weight to the fore foot.

 

Upper Part (Also Called Shoe Upper) Components

Quarter: This is the posterior portion of the shoe upper. A high quarter is

referred as a “high top” and is used by runners and footballers for greater

sensory feedback, and to prevent retrocalcaneal pain.

Heel counter: In sports shoes there is a reinforcement of the quarter posteriorly

called a heel counter which provides posterior stability to the shoe and

supports the calcaneus.

Vamp: Vamp is the anterior portion of the upper and is often reinforced with

a toe box anteriorly. In front is the tongue which protects the upper fore foot

behind the lace stays. Extra-depth shoes allow more room inside the shoe for

orthotic intervention.

Throat: This is the opening of the shoe located at base of the tongue, through

which the foot is inserted.

Toe box: It prevents the toes from suffering trauma when the person kicks as

in football. Even normally it is provided in the shoe to avoid stubbing of the

toes.

Tongue: This is the part of the vamp which extends down in front of the throat.

Stirrup: This is a piece on the outer sole in the shank region just in front of

the heel offering attachment to the metal uprights.

 

Modifications of the Orthopedic Shoe

The shoe can be modified according to the deformity, disease process or

congenital anatomical configuration of the patient to:

 Modifications to the outer sole

 

 

• Maintain the foot in anatomical position

• Treat symptoms of pain burning or fatigability.

• Prevent further deformity

• Afford cosmesis

• Provide symmetry

• Provide a better stance and gait.

 

ANKLE-FOOT ORTHOSIS (AFO) (FIG. 7.5)

Metal Ankle-foot Orthosis

The AFO is a boot to which an ankle joint is fixed through the stirrup. There

are metal uprights (medial and lateral bars) ascending up to the calf region.

The components are:

• Proximal calf band with leather straps

• Medial and lateral bars articulating with medial and lateral ankle joints

help in control of plantar and dorsiflexion.

• Stirrups anchor the uprights to the shoe.

• Other modifications to the shoe, like medial and lateral supports can also

be prescribed for the AFO concomitantly.

 

Ankle Joint

There are five types of artificial ankle joints fit to the AFO,

prescribed according to the power of the muscles controlling the ankle. They

are:

• Free ankle, given when there is normal ankle power;

• Limited ankle joint is prescribed when the muscles operating the ankle are

totally flail and have no power.

• 90° foot drop stop is when the ankle joint allows dorsiflexion but stops short

at the neutral position that is at 90 degrees. Thus it does not allow plantar

flexion. It is recommended when there is foot drop—when the dorsiflexors

are weak and plantar flexors are normal, or when the dorsiflexors are

normal or near normal and plantar flexors are spastic.

• Reverse 90° ankle joint: This is an ankle joint which allows plantar flexion

but stops short at the neutral position that is at 90 degrees. Thus it does

not allow dorsiflexion and is prescribed to prevent a calcaneus deformity.

This happens when plantar flexors are weak, while dorsiflexors are normal.

It is not commonly used.

• Fixed ankle joint: Sometimes the foot needs to be protected and weight is

taken off injured portions as in fracture calcaneus when in combination

with a weight relieving orthosis it takes the weight off the foot. It is not

very commonly used.

 Indications

Ankle-foot orthosis is prescribed for,

• Muscle weakness affecting the ankle and sub-talar joints.

• Prevention or correction of deformities of the foot and ankle.

• Reduction of inappropriate weight bearing forces.

 

Dorsiflexor Muscle Paralysis

Aim: To prevent contracture of the Achilles tendon, and to assist dorsiflexion

during heel strike a dorsiflexion assist plastic posterior leaf spring AFO can

be prescribed that can be inserted in to shoes. This facilitates the client to wear

different shoes. The rationale for this option is that the spring prevents the

foot from dragging during swing, and permits only slight plantar flexion

during early stance, thereby enabling the client to achieve a foot flat position

without undue knee flexion. Tension on the Achilles tendon counteracts any

tendency to form contracture.

 

Ankle and Foot Paralysis

This is prescribed to provide stability and reduce gait deviations during the

swing and stance phases. A polypropylene solid ankle AFO to be worn with

a shoe prevents the foot from dragging during swing; the brace rigidity also

prevents ankle dorsiflexion during midstance. Another option is to prescribe

a hinged AFO. Adjustable hinges enable the clinician to alter the range of

ankle excursion. The limited ankle joint, prescribed quite often, permits ankle

movement about a small range, usually 10°-15° of dorsi and plantar

flexion. A third option is to prescribe a metal and leather AFO with

adjustable ankle joints for plantar flexion and dorsiflexion and corrective

straps for valgus and varus deformities. This AFO provides some

mediolateral stability.

 

Spasticity

AFO’s are used in children with cerebral palsy to stabilize the foot during

heel strike and foot flat phase. A polypropylene orthosis given as a shoe insert

prevents plantar flexion, and also dragging of the toe during the swing phase.

If neglected the foot goes in for equinus contractures and may require injection

of Botox or surgery. The sidewalls of the orthosis control pes valgus or varus

during early stance.

 

Limited Weight Bearing

This is a rarer indication for the AFO, to reduce loading on the leg and foot

in conditions where the foot needs to be protected (e.g. fracture calcaneus).

There is a socket at the patellar tendon bearing area, which has a weightrelieving

brim similar to the socket in the below knee prosthesis. The heel of

the foot does not come into contact with the innersole, and a window is

provided for a finger to be introduced and confirm this. This enables the weight

to be taken higher up at the patellar tendon.

 

KNEE-ANKLE-FOOT ORTHOSIS (KAFO)

It provides stability to knee, ankle and foot.

 

Components

The components are the same as those in a metal AFO. In addition there are

uprights extended to the knee joint and lower thigh band. Thigh bands are

suspension mechanisms to which the uprights are attached. They are worn

by the patient to fasten the orthoses to the leg or thigh.

 

Knee Joints

Knee joints are provided in calipers, so that the wearer can sit down. During

walking the joint is locked in full extension for stability, but at the expense

of a good gait pattern because the person walks with a stiff knee gait.

There are three basic types of knee joints:

• Straight set knee joint: allows free flexion and prevents hyperextension. The

upper segment rotates about a single transverse axis. It is used in

combination with a drop lock to give further stability. This is the joint

usually prescribed in our country. It is cheap and easy to repair.

• The polycentric knee joint uses the double axis system to simulate the

flexion/extension movements of femur and tibia at knee joint.

• Posterior Offset Knee Joint: This is given for patients with minimal

quadriceps weakness, since it keeps the knee extended, though there is not

enough stance control. The criteria for prescribing a posterior offset knee

joint is adequate power of hip flexion and extension and the ability to

generate enough momentum to walk. The placement of the joint is just

behind the anatomical knee joint to increase knee stability when walking.

Stance Control: The ideal joint should have stability during weight bearing

and flexion during the swing phase of gait when it is non-weight bearing.

This is more energy efficient, and decreases the exaggerated movements of the

hip which is seen when the knee is locked. Some of these joints are

mechanically operated while others are powered by computerized mechanisms

controllers.

 

Knee Locks

These are locks incorporated into the knee joint, to stabilize the knee joint in

extension.

• Drop lock is a wedge shaped metal piece that is placed on the lateral upright

bar. When the knee extends it drops over the joint and locks it. This is

commonly used in our country.

• Spring loaded lock: Sometimes the patient is unable to reach the knee or

may lose balance while doing so; or might feel embarrassed to do so in

public. So a spring loaded lock may be added to the drop ring lock. It

provides automatic locking using a spring action rather than depending

on gravity to do it. This lock is easier for locking and unlocking.

• Cam lock with spring loaded cam fits into groove in full extension. It is

also easier to release and gives good stability. In the double upright bar

it provides simultaneous locking and unlocking thereby provides maximum

rigidity. It is indicated in weight bearing braces when semiautomatic

unlocking is desired.

• The ball lock provides an easy method of unlocking medial and lateral knee

joints. The patient can catch the ball on the edge of the chair to release the

lock mechanism to permit sitting. This is useful for adolescent young men

and women who are conscious about their appearance and can wear the

caliper beneath their saree or salwar kameez. The trigger lock is connected

to a switch through a cable enabling patients to unlock the knee joint at

a point higher up. It is commonly used for patients with limited balance

and dexterity.

• A dial lock may be adjusted every 6° for precise control of knee flexion.

• Plunger type lock: It is cosmetically more acceptable since it is concealed

in the knee mechanism. It is indicated in persons having hand weakness.

 

Indications

The biomechanical indications for the use of KAFO’S (and HKAFO’s) are

divided into three parts

Muscle Weakness: Weakness of the muscles of the lower limbs, mainly those

controlling the knee and hip joint (more specifically the quadriceps and hip

extensors). This will most commonly result from spinal cord damage or lower

motor neuron disease such as poliomyelitis or injury to a nerve.

Upper Motor Neuron Lesions: Upper motor neuron lesions impair locomotor

function through loss of the normal control of the lower limb muscles. There

is an extensor synergy in the lower limb, which is used by the hemiplegic to

achieve stance stability. The orthotic device must additionally incorporate knee

joints, which limit hyperextension.

Loss of Structural Integrity: This is due to injuries to the main ligaments of

the knee and joint disease, either due to inflammatory (septic arthritis) or

degenerative (osteoarthritis) processes.

Genu Varus/Valgum: Damage to the medial joint compartment with resultant

varus instability, will result in a concentration of the joint force on the

damaged condyle. In addition the increased knee adduction moment will result

in increased tension on the lateral collateral ligament. Conversely there can

be damage to the lateral joint compartment with a concentration of pressure

on that side of the joint, resulting in abduction movement and stress on the

medial collateral ligament.

The orthotic device will need to incorporate knee joints which resist

abduction or adduction but which permit a normal range of flexion-extension.

It is recommended to prescribe a single upright KAFO with free knee and ankle

joints. The upright may be on the medial or lateral side of the leg, depending

on whether it is genu varus/valgum to be controlled.

Problem in Load Bearing: This form of structural impairment may be a

consequence of either a joint or bony defect such as failure of a hip or knee

joint replacement or a delayed or non-union of a femoral fracture. The orthotic

prescription is a “weight-relieving” knee-ankle-foot orthosis (explained earlier).

Knee Braces: Knee braces are prescribed in severe osteoarthritis of the knee,

to provide stability to the knee joint. They come with bilateral uprights and

knee joints, and usually extend from mid thigh to mid calf.

 

HIP-KNEE-ANKLE-FOOT ORTHOSIS (HKAFO)

The HKAFO is an extension of the KAFO. In addition to the KAFO there is

an attached hip joint which allows hip flexion and extension only. The

suspension is with a pelvic band, which is a padded rigid steel band extending

posteriorly and laterally, which fits between iliac crest and greater trochanter

and which is used to control rotational movement at the hip joint. In the front

it is fastened with a soft Velcro or buckle strap fastener. On the lateral side

it is connected by a lateral upright, or bar to a normal KAFO and on the medial

side the upright stops short of the ischial region. Movement at the hip is with

an uniaxial hip joint with a drop lock, which is locked during walking. In

conditions where weight relief from the lower part of the body is needed, the

body weight is taken away from the foot or leg and transmitted from ischial

seat through metal uprights to the ground.

HKAFO provides improved posture, and balance during standing and a

better controlled forward leg swing in patients with weak hip muscles.

However it is difficult wear and remove, and permits only limited step length.

There is also an increase in lumbar spine movements to compensate for limited

hip motion.

Uses

The HKAFO is prescribed whenever the muscles controlling the hip and its

stability are strained or weak. Of course muscles controlling the knee and ankle

may also be weak, and there may be tendency to varus or valgus of the ankle

which can be accommodated in the orthosis. The prescription of the HKAFO

must also take into consideration the problems at the knee and ankle.

 

Hip Rotation Control

Abnormal rotation at the hip, seen in some children with cerebral palsy is

not resolved by a general HKAFO, but by using:

• Pelvic bands with hip joints

• Spreader bars

• Silesian bandages.

Single-axis hip joints attached to pelvic bands are quite common but are

heavy and it is difficult donning and doffing them. Spreader bars lock both

legs but this restricts the leg from taking a step though each leg prevents the

other’s rotation. Silesian bands are bands that begin laterally posterior and

superior to the greater trochanter, encircle the pelvis on the normal side

between the greater trochanter and the iliac crest and attach anteriorly to

achieve some hip rotation control. It reduces gait deviation, particularly toeingin

that is attributable to faulty hip control. Hip rotation control straps are

prescribed and for preventing internal rotation, the client wears a waist belt.

Tied to the posterior aspect of the belt in the midline are two straps, each

having its distal attachment on each of the uprights of the HKAFO. The

bilateral hip joints control frontal and transverse plane motion.

THOSE ABOVE ARE COLLECTED FROM SOME BOOKS AND WEBSITES..

(TEXTBOOK OF REHABILITATION-SUNDER.S)

THANK YOU,

 SRIKUMARAN PHYSIOTHERAPY CLINIC & FITNESS CENTER