A lower limb orthosis is an external device applied or attached to a lower body segment to improve function by controlling motion, providing support through stabilizing gait, reducing pain through transferring load to another area, correcting flexible deformities, and preventing progression of fixed deformities.
Orthosis (or orthotic device) is the medical term for what most people would refer to as a brace or splint.
Orthoses generally are named by the body regions that they involve, as demonstrated by the following abbreviations:
v AFO : - Ankle-Foot Orthosis.
v KAFO : - Knee-Ankle-Foot Orthosis.
v HKAFO : - Hip-Knee-Ankle-Foot Orthosis.
v THKAFO : - Trunk-Hip-Knee-Ankle-Foot Orthosis.
Locomotion and gait
The total mass of the body can be considered concentrated at one point, called the center of gravity.
The center of mass is located in the midline, just anterior to the second sacral [S-2] vertebra while the individual is standing and walking. The center of mass changes with the configuration and function of the body.
The line of gravity is a line passing through the center of gravity to the center of the earth. This line -
(1) arises from the supporting surface between the ball and heel of the foot, then
(2) passes in front of the ankle and knee joints and slightly behind the hip joint to the center of gravity, then
(3) passes through the lumbosacral junction and behind the lumbar vertebral bodies to intersect the spine at the thoracolumbar junction, then
(4) continues in front of the thoracic vertebral bodies and through the cervicothoracic junction, and, lastly,
(5) travels behind the cervical vertebral bodies to the occipitocervical junction.
When the center of gravity does not fall through the area of support, it is unstable at that moment.
Gait cycle is defined as the activity that occurs between the initial contact of one extremity and the subsequent initial contact of the same extremity.
During a single gait cycle, each extremity passes through 1 stance phase and 1 swing phase.
o Stance phase occupies over 60% of the gait cycle during walking at average velocity. Stance phase includes initial contact, loading response, midstance, terminal stance, and preswing.
o Swing phase includes initial swing, mid swing, and terminal swing.
The average total displacement of the center of gravity in the vertical and lateral directions is less than 2 inches in normal gait.
The increase in displacement of the center of gravity increases the amount of energy for walking.
The purpose of using an orthosis is to enhance normal movement and to decrease abnormal posture and tone.
Lower extremity orthoses can be used to correct abnormal gait patterns and to increase the efficiency of walking.
Lower extremity orthotics
An orthosis is classified as a static or dynamic device.
A static orthosis is rigid and is used to support the weakened or paralyzed body parts in a particular position.
A dynamic orthosis is used to facilitate body motion to allow optimal function. In all orthotic devices, 3 points of pressure are needed for proper control of a joint.
A lower limb orthosis should be used only for specific management of a selected disorder. The orthotic joints should be aligned at the approximate anatomic joints.
Most orthoses use a 3-point system to ensure proper positioning of the lower limb inside the orthosis.
The orthosis selected should be simple, lightweight, strong, durable, and cosmetically acceptable.
Considerations for orthotic prescription should include the 3-point pressure control system, static or dynamic stabilization, flexible material, and tissue tolerance to compression and shear force.
An orthosis can be constructed from metal, plastic, leather, synthetic fabrics, or any combination.
Plastic materials, such as thermosetting materials and thermoplastics, are the materials most commonly used in the orthotic industry.
- Thermosetting materials can be molded into permanent shape after heating. They do not return to their original consistency even after being reheated. Thermoplastic materials soften when heated and harden when cooled.
- Low-temperature thermoplastics can be fabricated easily and rapidly with hot water or hot air and scissors, but they are used mainly in low stress activities.
- High-temperature (polypropylene) thermoplastics require higher temperature (150°C) to mold, but they are ideal for high stress activities.
- Leather, such as cattle hide, is used for shoe construction because it conducts heat and absorbs water well.
- Rubber has tough resiliency and shock-absorbing qualities.
- Rubber is used for padding in body jackets and limb orthoses.
- Metals, such as stainless steel and aluminum alloys, are adjustable, but they are heavy and not cosmetically pleasing.
- Metals can be used for joint components, metal uprights, sprints, and bearings.
Shoes and Foot Orthotics
Shoes are the important foundation of the lower limb orthosis. Shoes are used to protect and warm the feet, transfer body weight while walking, and reduce pressure or pain through redistributing weight.
Shoes should be comfortable and properly fitted. They should be at least 1 cm longer than the longest toe and correspond to the shape of the feet.
The shoe can be divided into lower and upper parts.
The lower parts consist of the sole, shank, ball, toe spring, and heel.
The upper parts include the quarter, heel counter, vamp, toe box, tongue, and throat.
Parts of the shoe
- Outer and inner soles are separated by compressible filler. Both of them are made preferably of leather for breathability.
- The ball is the widest part of the sole and corresponds to the area of the metatarsal heads.
- The shank area is from the anterior border of the heel to the ball. A steel piece may be used to reinforce the shank area.
- The toe spring is the space between the anterior sole and the floor.
- Leather with rubber on the plantar surface commonly is used for the heel.
- A spring heel is one-eighth inch high.
- An Oxford heel is three quarters to 1 inch high.
- A military heel is 1 and one quarter inches high.
- A Cuban heel is 1 and a half inches high.
- The heel counter is the posterior portion of the upper part between the quarters. This structure is used to reinforce the quarters and support the calcaneus. The heel counter can increase the posterior stability of the shoe.
- The upper is the portion of the shoe above the sole.
- The vamp is the anterior section.
- The quarters are the posterior section.
- The throat is the base of the tongue.
- The tongue is a piece attached to the vamp.
- The toe box is the reinforcement of the vamp to protect the shoe from trauma.
A properly fitted shoe should have adequate room for the foot to expand while the patient is bearing weight.
The shoe should be at least 1 cm longer than the longest toe, and the widest part also should correspond to the widest part of the foot.
Shoes can be modified to reduce pressure on sensitive areas by redistributing weight toward pain-free areas.
External shoe modifications
- Heel modifications
- A cushioned heel - A wedge of compressible rubber is inserted into the heel to absorb impact at heel strike. This cushion often is used with a rigid ankle to reduce the knee flexion moment by allowing for more rapid ankle plantar flexion.
- A heel flare - A medial flare is used to resist inversion, and a lateral flare is used to resist eversion. Both flares are used to provide heel stability.
- A heel wedge - A medial wedge is used to promote inversion, and a lateral wedge is used to promote eversion. The heel counter should be strong enough to prevent the hindfoot from sliding down the incline created by the wedge.
- Extended heel - The Thomas heel projects anteriorly on the medial side to provide support to the medial longitudinal arch. The reverse Thomas heel projects anteriorly on the lateral side to provide stability to the lateral longitudinal arch.
- Heel elevation - A shoe lift is used to compensate for fixed equinus deformity or for any leg-length discrepancy of more than one quarter of an inch.
- Sole modifications
- Rocker bar - This is a convex structure placed posterior to the metatarsal head. The rocker bar is used to shift the rollover point from metatarsal head to metatarsal shaft to avoid irritation of ulcers along the metatarsal head in patients with diabetes mellitus (DM).
- Metatarsal bar - This is a bar with a flat surface placed posterior to the metatarsal head. The metatarsal bar is used to relieve the pressure from the metatarsal heads.
- Sole wedge - A medial wedge is used to promote supination, and a lateral wedge is used to provide pronation.
- Sole flare - A medial flare is used to resist inversion, and a lateral flare is used to resist eversion. Both flares promote great stability.
- Steel bar - The steel bar is placed between the inner sole and outer sole. This bar is used to reduce forefoot motion to reduce the stress from phalanges and metatarsals.
- Combination of sole and heel modifications - If heel elevation is more than half an inch, a sole elevation should be added to avoid equinus posture.
Internal shoe modifications
- Heel modifications
- Heel cushion relief - This soft pad with excavation is placed under the painful point of the heel.
- Heel wedge - A medial heel wedge can rotate the hindfoot into inversion. A lateral heel wedge can evert the hindfoot to avoid pressure on the cuboid.
- Sole modifications
- Metatarsal pad - This domed pad is designed to reduce the stress from metatarsal heads by transferring the load to metatarsal shafts in metatarsalgia.
- Inner sole excavation - A soft pad filled with compressible material is placed under 1 or more metatarsal heads.
- Scaphoid pad - This type of pad extends from one half inch posterior to the first metatarsal head to the anterior tubercle of the calcaneus. The apex of the scaphoid pad is between the talonavicular joint and the navicular tuberosity. The scaphoid pad is used for medial arch support.
- Toe crest - A crescent-shaped pad is placed behind the second through fourth phalanges. The toe crest fills the void under the proximal phalanges and reduces the stress.
The foot orthosis extends from the posterior border of the foot to a point just posterior to the metatarsal heads.
This device is used to accommodate the abnormal foot to help restore more normalized lower limb biomechanics.
Orthotic inserts include the following:
- UCBL (University of California at Berkeley Laboratory) insert - This insert is made of rigid plastic fabricated over a cast of the foot held in maximal manual correction. The UCBL encompasses the heel and midfoot, and it has rigid medial, lateral, and posterior walls.
- Heel cup - The heel cup is a rigid plastic insert that covers the plantar surface of the heel and extends posteriorly, medially, and laterally up the side of the heel. The heel cup is used to prevent lateral calcaneal shift in the flexible flat foot.
- Sesamoid insert - This addition to an orthosis is an insert amounting to three quarters of an inch with an extension under the hallux to transfer pressure off the short first metatarsal head and onto its shaft.
In a randomized clinical trial, a Canadian study investigated the effectiveness of custom-made orthoses versus that of prefabricated ones, with both types tested over a 4-week period in patients with lower extremity musculoskeletal pain.
The report’s authors determined that although both types of orthoses brought immediate improvement in economy of gait, only the custom-made orthoses enabled patients to maintain such improvement over the entire 4-week period.
An ankle-foot orthosis (AFO) is commonly prescribed for weakness or paralysis of ankle dorsiflexion, plantar flexion, inversion, and eversion.
AFOs are used to prevent or correct deformities and reduce weight bearing.
The position of the ankle indirectly affects the stability of the knee with ankle plantar flexion providing a knee extension force and ankle dorsiflexion providing a knee flexion force.
An AFO has been shown to reduce the energy cost of ambulation in a wide variety of conditions, such as spastic diplegia due to cerebral palsy, lower motor neuron weakness of poliomyelitis, and spastic hemiplegia in cerebral infarction.
Thermoplastic AFOs - These devices are plastic molded AFOs, consisting of the following 3 parts:
(1) A shoe insert,
(2) A calf shell, and
(3) A calf strap attached proximally
The rigidity depends on the thickness and composition of the plastic, as well as the trim line and shape.
Thermoplastic AFOs are contraindicated in cases of fluctuating edema and insensation.
- Posterior leaf spring (PLS) - The PLS is the most common form of AFO with a narrow calf shell and a narrow ankle trim line behind the malleoli. The PLS is used for compensating for weak ankle dorsiflexors by resisting ankle plantar flexion at heel strike and during swing phase with no mediolateral control.
- Spiral AFO - This AFO consists of a shoe insert, a spiral that starts medially, passes around the leg posteriorly, then passes anteriorly to terminate at the medial tibial flare where a calf band is attached. The spiral AFO allows for rotation in the transverse plane while controlling ankle dorsiflexion and plantar flexion, as well as eversion and inversion.
- Hemispiral AFO - This AFO consists of a shoe insert with a spiral starting on the lateral side of the shoe insert, passing up the posterior leg, and terminating at the medial tibial flare where the calf band is attached. This design is used for achieving better control of equinovarus than the spiral AFO can.
- Solid AFO - The solid AFO has a wider calf shell with trim line anterior to the malleoli. This AFO prevents ankle dorsiflexion and plantar flexion, as well as varus and valgus deviation.
- AFO with flange - This AFO has an extension (flange) that projects from the calf shell medially for maximum valgus control and laterally for maximum varus control.
- Hinged AFO - The adjustable ankle hinges can be set to the desired range of ankle dorsiflexion or plantar flexion.
- Tone-reducing AFO (TRAFO) - The broad footplate is used to provide support around most of the foot, extending distally under the toes and up over the foot medially and laterally to maintain the subtalar joint in normal alignment. The TRAFO is indicated for patients with spastic hemiplegia.
Metal and metal-plastic AFOs
This type of AFO consists of a shoe or foot attachment, ankle joint, 2 metal uprights (medial and lateral), with a calf band (application of force) connected proximally.
The stirrup anchors the uprights to the shoes between the sole and the heel. The caliper is a round tube placed in the heel of the shoe, which connects to the uprights and also allows for easy detachability of the uprights.
A molded shoe insert is another alternative to fit the stirrup into the shoe, which also allows maximum control of the foot and aligns the anatomic and mechanical ankles.
Ankle joints - The mechanical ankle joints can control or assist ankle dorsiflexion or plantar flexion by means of stops (pins) or assists (springs). The mechanical ankle joint also controls mediolateral stability. Knee extension moment is promoted by ankle plantar flexion, and knee flexion moment is promoted by ankle dorsiflexion.
v Free motion ankle joint - The stirrup has a completely circular top, which allows free ankle motion and provides only mediolateral stability.
v Plantar flexion ankle joint stop - This ankle joint stop is produced by a pin inserted in the posterior channel of the ankle joint or by flattening the posterior lip of the stirrup's circular stop. The plantar flexion stop has a posterior angulation at the top of the stirrup that restricts plantar flexion but allows unlimited dorsiflexion and promotes knee flexion moment. This design is used in patients with weakness of dorsiflexion during swing phase and flexible pes equinus.
v Dorsiflexion ankle joint stop - The stirrup has a pin inserted in the anterior channel of the ankle joint or by flattening the anterior lip of the stirrup's circular stop. The dorsiflexion stop has an anterior angulation at the top of the stirrup that restricts dorsiflexion but allows unlimited plantar flexion and promotes a knee extension moment in the meantime. This design is used in patients with weakness of plantar flexion during late stance.
v Limited motion ankle joint stop - This ankle joint stop has anterior and posterior angulations at the top of the stirrup with restricted dorsiflexion and plantar flexion ankle motion. The limited motion ankle joint stop has a pin in the anterior and the posterior channel, and it is used in ankle weakness affecting all muscle groups.
v Dorsiflexion assist spring joint - This joint has a coil spring in the posterior channel and helps to aid dorsiflexion during swing phase.
v Varus or valgus correction straps (T-straps) - A T-strap attached medially and circling the ankle until buckling on the outside of the lateral upright is used for valgus correction. A T-strap attached laterally and buckling around the medial upright is used for varus correction.
Knee-Ankle-Foot Orthotics and Knee Orthotics
Knee-ankle-foot orthotics (KAFOs) consists of an AFO with metal uprights, a mechanical knee joint, and 2 thigh bands.
KAFO can be used in quadriceps paralysis or weakness to maintain knee stability and control flexible genu valgum or varum.
KAFO also is used to limit the weight bearing of the thigh, leg, and foot with quadrilateral or ischial containment brim.
A KAFO is more difficult to don and doff than an AFO, so it is not recommended for patients who have moderate-to-severe cognitive dysfunction.
- KAFO - This orthosis can be made of metal-leather and metal-plastic or plastic and plastic-metal. The metal design includes double upright metal KAFO (most common), single upright metal KAFO (lateral upright only), and Scott-Craig metal KAFO. The plastic designs are indicated for closer fit and maximum control of the foot, including supracondylar plastic KAFO, supracondylar plastic-metal KAFO, and plastic shells with metal uprights KAFO.
- A double upright metal KAFO is an AFO with 2 metal uprights extending proximally to the thigh to control knee motion and alignment. This orthosis consists of a mechanical knee joint and 2 thigh bands between 2 uprights.
- A Scott-Craig orthosis consists of a cushioned heel with a T-shaped foot plate for mediolateral stability, ankle joint with anterior and posterior adjustable stops, double uprights, a pretibial band, a posterior thigh band, and knee joint with pawl locks and bail control. Hyperextension of the hip allows the center of gravity falling behind the hip joint and in front of the locked knee and ankle joints. With 10° of ankle dorsiflexion alignment, it allows a swing-to or swing-through gait with crutches. This orthosis is used for standing and ambulation in patients with paraplegia due to spinal cord injury (SCI).
- The supracondylar plastic orthosis uses immobilized ankle in slight plantar flexion to produce a knee extension moment in stance to help eliminate the need for a mechanical knee lock. This orthosis also resists genu recurvatum and provides mediolateral knee stability.
- A plastic shell and metal upright orthosis consists of a posterior leaf spring AFO with double metal uprights extending up to a plastic shell in the thigh with an intervening knee joint
- Knee joints - The mechanical knee joint can be polycentric or single axis. Polycentric is used for significant knee motion, and a single axis is more common and is used for knee stabilization. Single axis knee joints include the following:
- Free motion knee joint - This joint has unrestricted knee flexion and extension with a stop to prevent hyperextension. The free motion knee joint is used for patients with recurvatum but good strength of the quadriceps to control knee motion.
- Offset knee joint - The hinge is located posterior to the knee joint and ground reaction force; thus, it extends the knee and provides great stability during early stance phase of the gait cycle. This joint flexes the knee freely during swing phase and is contraindicated with knee or hip flexion contracture and ankle plantar flexion stop.
- Drop ring lock knee joint - The drop ring lock is the most commonly used knee lock to control knee flexion. The rings drop to unlock over the knee joint while the knee is in extension by gravity or manual assistance. This type of joint is stable, but gait is stiff without knee motion. A ball bearing on a spring can be added just above the drop lock to keep it from slipping up as the patient ambulates. Patients over 120 pounds usually feel more secure with medial and lateral drop locks.
- Pawl lock with bail release knee joint - The semicircular bail attaches to the knee joint posteriorly, and it can unlock both joints easily by pulling up the bail or backing up to sit down in a chair. A major drawback is the accidental unlocking while the patient is pulling his or her pants up or bumping into a chair.
- Adjustable knee lock joint (dial lock) - The serrated adjustable knee joint allows knee locking at different degrees of flexion. This type of knee joint is used in patients with knee flexion contractures that are improving gradually with stretching.
- Ischial weight bearing - Most individuals in a KAFO sit partially on the upper thigh band unless the cuff is brought up above the ischium.
- Knee cap and strap - The knee cap can be placed in front of the knee in the orthosis to prevent flexion of the knee. A medial strap is used for genu valgum and a lateral strap is used for genu varum. These buckles wrap around the upright in the same way as ankle straps.
A knee orthosis (KO) only provides support or control of the knee but not of the foot and ankle. The knee joint is centered over the medial femoral condyle.
If the patient does not have adequate gastrocnemius delineation so that there is a shelf for the distal end of the orthosis to rest on, the brace may slide down the leg with wear. In that case, the brace needs to extend to the sole of the foot.
A hip-knee-ankle-foot orthosis (HKAFO) consists of a hip joint and pelvic band in addition to a KAFO.
The orthotic hip joint is positioned with the patient sitting upright at 90°, while the orthotic knee joint is centered over the medial femoral condyle.
Pelvic bands complicate dressing after toileting unless the orthosis is worn under all clothing. Pelvic bands increase the energy demands for ambulation.
- Pelvic bands
- Bilateral pelvic band - This band is used more commonly with its posterior metal ends located anterior to the lateral midline of the pelvis and is interconnected by a flexible belt.
- Unilateral pelvic band - This band rarely is used because most conditions requiring a HKAFO have bilateral involvement.
- Pelvic girdle - The pelvic girdle is made of molded thermoplastic materials, providing a maximum degree of control in patients with bilateral involvement.
- Silesian belt - This belt has no metal or rigid band and offers mild resistance to abduction and rotation of the hip. The Silesian belt attaches to the lateral upright and encircles the pelvis.
- Hip joints and locks - The hip joint can prevent abduction and adduction as well as hip rotation.
- Single-axis hip joint with lock - This joint is the most common hip joint with flexion and extension. The single axis hip joint with lock may include an adjustable stop to control hyperextension.
- Two-position lock hip joint - This hip joint can be locked at full extension and 90° of flexion and is used for hip spasticity control in a patient who has difficulty maintaining a seated position.
- Double-axis hip joint - This hip joint has a flexion-extension axis and abduction-adduction axis to control these motions.
A trunk-hip-knee-ankle-foot orthosis (THKAFO) consists of a spinal orthosis in addition to a HKAFO for control of trunk motion and spinal alignment.
A THKAFO is indicated in patients with paraplegia and is very difficult to don and doff.
v Reciprocating gait orthosis (RGO) - An RGO consists of bilateral KAFOs with posteriorly offset locking knee joints, hip joints, and a custom-molded pelvic girdle with a thoracic extension. The hip joints are coupled with cables preventing bilateral hip flexion simultaneously. The hip extension on one side coupling hip flexion on the other side through the cables produces reciprocal walking gait pattern. The RGO combined with functional electronic stimulation (FES) can be used for 2-point or 4-point gait patterns in ambulatory paraplegic or tetraplegic (C8) patients. Using the RGO with FES can double the patient's optimum gait speed, lower blood pressure and heart rate, and increase oxygen uptake as compared with ambulating with the RGO without FES.
v Para walker - This device is a hip guidance orthosis, which consists of bilateral KAFOs with a ball-bearing hip joint and a body brace. Ambulation is performed through trunk motion transmitted to the lower extremities with hip flexion and extension via the brace. Hip flexion is restricted by a stop, and hip extension may be free or limited by a stop. The para walker is developed for patients with SCI. A study of 5 paraplegic patients found an average reduction in oxygen consumption of 27%, with 33% faster ambulatory rate compared with the RGO.
v Parapodium - This device is developed for pediatric myelodysplastic patients to allow them to stand without crutches for functional activities with their upper limbs free. The parapodium consists of a shoe clamp, aluminum uprights, a foam knee block, and back and chest panels. Hip and knee may be locked for standing and unlocked for sitting. A torque converter under the base allows side-to-side rocking to be translated into forward propulsion.
v Standing frame - This allows standing but does not permit hip and knee flexion. The standing frame is used for children to learn standing balance and achieve a swing-through gait.
Special Purpose Lower Limb Orthotics
- Weightbearing orthoses - This orthosis is designed to eliminate weight bearing through the lower extremities. Weightbearing orthoses consist of patellar-tendon–bearing orthosis (PTBO), ischial weightbearing orthosis, and patten bottom with uprights terminated in a floor pad or patten distal to the shoe.
- Fracture orthoses - This orthosis stabilizes the fracture site and promotes callus formation, while allowing weight bearing and joint movement after initial subsiding pain and edema. The bony motion at the fracture site is prevented through circumferential compression of the soft tissue. Fracture orthoses include the tibial fracture orthosis and femoral fracture orthosis.
- Angular and deformity orthoses - This orthosis is used in the pediatric population. The Denis Brown splint is for clubfoot. A frame orthosis applies corrective forces to proximal rotational deformities. A torsion shaft orthosis is used in mild scissoring gait of spastic diplegia.
- Congenital hip dislocation orthoses - These devices, such as the Pavlik harness, Ilfeld splint, and Von Rosen splint, are used to maintain the hip in flexion and abduction position to hold the femoral head within the acetabulum.
- The Scottish Rite, Toronto, and non–skeletal-bearing trilateral orthoses - These are used in Legg-Calve-Perthes disease to maintain the hip in abduction and keep the femoral head in the acetabulum.