INTRODUCTION
Modern orthotic devices play a vital role in the field of
orthopaedic and
neurological rehabilitation. They are given to improve function,
restrict or
enforce motion, or increase support to a part of the body, like
the spine or
lower limbs. 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.
DEFINITION
An orthosis is a mechanical device fitted to the body to
maintain it in an
anatomical or functional position.
GENERAL
PRINCIPLES OF ORTHOSIS
• Use of forces:
Orthoses utilize forces to limit or assist movements, for
example
– Rigid material spanning a joint prevents motion, e.g.
posterior tube
splint.
– A spring in a joint is stressed by one motion and then recoils
to assist
the opposite desired motion e.g. leaf spring orthosis.
• Sensation: An orthotic device often covers skin areas and
decreases sensory
feedback. Proprioception should be preserved where possible.
• Correcting a mobile
deformity: A flexible deformity may be
corrected by an
orthosis, like the one given in genu recurvatum or mobile
scoliosis. The
corrective force must be balanced by proximal and distal counter
forces
(three point force systems).
• Fixed deformity: If a fixed deformity is accommodated by an
orthosis, it will
prevent the progression of the deformity.
• Adjustability: Orthotic adjustability is indicated for children
to
accommodate their growth and for patients with progressive or
resolving
disorders.
• Maintenance and
cleaning: The orthosis should be
simple to maintain and
clean
• Application: The design should be simple for easy donning and
doffing.
The more complicated the gadget the less likely it is to be
accepted for
permanent use.
• Limitation of
movement: Limiting motion to reduce
pain, e.g. knee brace
• Gravity: Gravity plays an important role in upper limb
orthosis, especially
in those joints where the heaviest movement masses are present.
For
example, a Rolyan shoulder cuff can be used in hemiplegia to
prevent
subluxation of the shoulder, which is the largest joint prone
for the
deleterious effects of gravity.
• Comfort: The orthosis should be easy to wear and
comfortable to use. This
is possible if the forces meant for correction are distributed
over the largest
area possible.
• Utility: The orthosis must be useful and serve a real
purpose. If one hand
is functional and normal, an upper extremity orthosis for the
affected side
may not be used as most activities of daily living can be
performed with
the good hand.
• Cosmesis: Cosmesis is important especially in the hand. A
functional but
unsightly orthosis is often rejected if the patient values
appearance over
function.
• Duration: Use only as indicated and for as long as
necessary.
• Appropriateness: It should allow joint movement wherever
appropriate.
Principle
of Jordan
The basic mechanical principle of orthotic correction is the “Three point
system of Jordan.” This system applies corrective or assistive
forces, which
are implemented at the surface of the orthosis through the skin
and are
transmitted to the underlying soft tissues and bones.
To remain stable, the body has to have one point of pressure
opposed by two
equal points of counter pressure in such a way that F1 = F2 + F3.
The corrective force is directed toward the angular or deformed
area to be
corrected, and other two counter forces are applied distal and
proximal to the
corrective force. The greater the distance between the force and
the counter
forces, the less the counter force required.
BIOMECHANICS
OF ORTHOSIS
There are four different ways in which an orthosis may modify
the system
of external forces and moments acting across a joint.
• Control of rotational moments across a joint
• Control of translational forces around a joint
• Control of axial forces around a joint
• Control of line of action of ground reaction force. This
involves modifying
the point of application and line of action of the ground
reaction force
during static or dynamic weight bearing.
The first three are termed as “Direct” in that the orthosis
actually surrounds
the joint being influenced. The fourth may be termed “Indirect” as the orthosis
modifies the external force system acting beyond its physical
boundaries.
Factors affecting tissue response to the orthosis:
• Extrinsic Factors:
– Pressure
– Shear
– Interface with the microenvironment.
• Intrinsic Factors:
– Tissue mechanics—the compressibility of the soft tissues
influences their
susceptibility to the breakdown process; the more compressible
the tissues
the more likely it is that blood vessels will be occluded.
– Load transmission across the interface between the orthosis
and the
tissues.
The
Patient-Orthosis Interface
The patient-orthosis interface may be defined as the junction
between the body
tissues and orthosis. This is the support surface through which
forces are
transmitted.
When force is applied through an interface there will be some
deformation
of both surfaces, depending on their relative thickness, the
relative shapes of
the underlying rigid structures and the level of the applied
force. This leads
to a progressive breakdown of that tissue and, in the case of
paraplegia with
loss of sensation and the shift reflex; this is the basis for
the formation of a
pressure sore.
CLASSIFICATION
According
to Function
Supportive: It stabilizes the joints and supports the body in
its anatomical
position, e.g. calipers, gaiters.
Functional: It stabilizes the joint and also makes up for a
lost function, e.g.
foot drop splint in common peroneal nerve palsy or dynamic
cock-up splints
in wrist drop.
Corrective: To correct deformities, e.g. club foot boot in
congenital talipes
equinovarus.
Protective: To protect a part of the body during its healing,
e.g. rigid four postcollar
for fracture cervical vertebrae.
Prevent substitution of function: In a full length caliper, substitution of hip
flexors by abductors or adductors of hip and other similar trick
movements
are prevented.
Strengthen certain groups of muscles: Tenodesis splint
Relief of pain: The lumbosacral corset supports the lower back, preventing
painful movement.
Prevent weight bearing: A weight relieving orthosis, prescribed for
conditions
like fracture calcaneum will take weight away from the injured
site to a
proximal site like the patellar tendon bearing area.
Regional
Classification
They are classified according to the anatomical area fitted with
the orthosis.
• Cervical Orthosis
• Head-Cervical Orthosis (HCO)
• Head-Cervical-Thoracic Orthosis (HCTO)
• Sacral Orthosis
• Lumbo-sacral Orthosis (LSO)
• Thoraco Lumbo-sacral Orthosis (TLSO)
• Upper Extremity Orthosis
– Shoulder and Arm Orthosis
– Elbow Orthosis
– Wrist Orthosis
– Hand Orthosis
• Lower Extremity Orthosis
– Foot Orthoses (FO)
– Ankle-Foot Orthoses (AFO)
– Knee-Ankle Foot Orthoses (KAFO)
– Hip-Knee-Ankle-Foot Orthoses (HKAFO)
Orthosis
Serving Specialized Functions
• Swedish knee cage: It is a knee orthosis that is used to control
minor or
moderate genu recurvatum.
• Pediatric orthosis:
Standing Frame: Used for a toddler with
spina bifida or
a T12 neurosegmental level lesion or a child with cerebral
palsy.
• Parapodium (Swivel
Orthosis): It is used for leg length
discrepancy and
has a wide abdominal support pad to assist in upright posture.
• Reciprocating gait
orthosis (RGO) These are bilateral hip,
knee, ankle, foot
orthosis to provide contra lateral hip extension with
ipsilateral hip flexion.
When one hip flexes, the contra lateral hip extends (Fig. 7.2).
• Twister: It is prescribed for lack of control of internal
or external rotation
or torsion of lower limb.
Orthosis
Used in Specific Conditions
Orthosis are used for hand injuries, flexors and
extensor tendon injuries
like volar and dorsal wrist splints.
Orthosis used for nerve injury:
• Radial nerve injury—a radial nerve glove is given with the wrist
held in
extended position or a wrist drop splint is given.
• Ulnar nerve injury—Splints that maintain the flexion of
metacarpophalangeal
joints and extension at interphalangeal joint with a lumbrical
bar, e.g. knuckle duster splint.
• Median nerve injury—Splint is applied to the thumb in an abducted,
opposed
position. (Opponens splint).
Orthosis used for inflammation of joints
and tendons: Static thumb spica
orthosis with the proximal interphalangeal joint kept free.
Orthosis used for burns: Splinting done to hold the part in neutral
position
and this prevents stiffening of the metacarpophalangeal joints.
Orthosis used in rheumatoid arthritis: Static three point proximal
interphalangeal orthosis for Boutonniere deformity.
Orthoses used for stroke and brain
injury: In stroke, large arm slings
are used
to prevent subluxation of the shoulder.
Contraindications
to Orthoses
• Severe deformity which cannot be accommodated in the orthosis.
• If it limits movements at other normal joints.
• Skin infections.
• When the muscle power is inadequate to perform its function
because of
the weight of the orthoses.
• Where the orthosis interferes grossly with clothing or limits
ones style of
living.
• Lack of motivation or other psychological problems.
• Very young or old patients.
Disadvantages
of Orthosis
• Lack of cosmesis: an unsightly orthosis is often the reason
for a patient
discontinuing its use.
• Muscles supporting the spine can become weak.
• Wherever segments are immobilized, we find increased movements
at ends
of these segments.
• The person becomes psychologically dependent on it.
• Reduction in bone density.
• Skin ulcerations or calluses at the patient orthoses
interface.
Physical
Assessment
A thorough assessment is imperative before prescription of an
orthosis and
will include:
• Type of paralysis and prognosis.
• Posture static and dynamic.
• Range of movement of joints.
• Muscle power; also of the hand grip especially when crutches
are needed.
• Coordination.
• Deformity.
• Sensations touch and proprioception.
• Skin condition—ulceration, abrasions, dermatitis.
• Alignment of limbs
• Gait.
– Need for assistive devices
– Duration of gait
– Deviation of gait
– Ability to rise from various types of chairs
– Ability to climb stairs and ramps.
• Dexterity—ability to manage buckles and other fasteners.
• Vision—walking safely indoors and outdoors needs good vision,
especially
in dim light.
• Spasticity.
• Limb length discrepancy.
Subjective
Assessment
• Goals—what the patient hopes to achieve with his caliper
• Complaints from the patient about the orthosis on its
performance and
appearance, and whether there is pain.
• Whether the patient has used an orthosis previously.
• Comprehension—Understanding of oral and written instructions
on how
to use the orthosis.
• Economic considerations like the funding of the treatment and
the patient’s
social environment.
THOSE ABOVE ARE
COLLECTED FROM SOME BOOKS AND WEBSITES..
(TEXTBOOK OF REHABILITATION-SUNDER.S)
THANK YOU,
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