Orthosis Flashcards
(37 cards)
1
Q
What is an orthosis?
A
- A device that is Externally applied or Attached to a body segment and that Faciliates or Improves function by support, correcting or compensating for a skeletal deformity or weakness
2
Q
What is the regions of the body in aaos nomenclature?
A
upper limb
- S= shoulder
- E= elbow
- W= wrist
- H= Hand
Lower limb
- H= hip
- K= knee
- A= ankle
- F=foot
Spine
- C= Cervical
- T=thoracic
- L= lumbar
- S= sacroiliac
3
Q
What is the control of the designated function of Orthoses?
A
- F- free motion allowed
-
A- assist
- application of external force to increase range or velocity of a desire motion
- R- resist movement of a external force
- S - stop -ie static unit to deter motion
- H - hold ie elimination of all motion in a prescribed plane
- L -lock- optional lock
4
Q
What are the ideal characteristics of Orthoses ?
A
- Lightweight
- Durable
- Biomechanically effective
- Cosmetically pleasing
- Easy to don and off
- Rapid provision and replacement
- Washable
- Adjustable
- Comfortable
- Free of pressure areas
5
Q
What are the functional characteristics of Orthoses?
A
- Provisional support- prevent weak muscles/ligaments being stretched- TLO to support a collapsing osteeoporosis spine
- Limitation of motion - KO to prevent hyperextension
- Correction of deformity - force affected joint into near alignment and redirect growth e.g.a- tlso- Thoracolumbarsacral orthosis
- Assistance of motion- hkafo- hipkneeanklefoot orthosis in myelomeningocele
- Miscellaneous - warmth, placebo effect
- Combination-many combine several functions e.g.KAFO for leg with polio, gives support, limits movement at the knee, may correct ankle varus and springs assist ankle dorsiflexion
6
Q
What other ways can you define the function of orthosis?
A
- Static- has no moving parts and is used to immobilise a part of the body
- Dynamic- moving parts by movement is controlled by an energy store
7
Q
What must an orthosis have for proper control?
A
- 3 points of contact to control the joint
8
Q
What are the criteria for a supportive orthosis ?
A
- Joint must be maintained in an optimium anatomical position during rest period
9
Q
What is the purpose of a corrective orthosis ?
A
- Is to impose or control a set of forces on a body part
- Each force has magnitude and direction & the resultant worked out
10
Q
What is Newton’s 3rd law of reaction?
A
- For every reaction there is an equal and opposite reaction
11
Q
What is the ground reaction force?
A
- The force exerted by the ground on the body
- it is the magnitude but opposite in direction to the force exerted on the ground by the body
- if the GRF doesn’t pass thru the centre of the joint it creates a moment on that joint
12
Q
Where is the GRF in mid-stance?
A
- Posterior to the hip
- -> hip extension moment counter balanced by the gradual tightening of the anterior hip capsule
- The GRF is anterior to the knee
- -> knee extension moment that resisted by the tight posterior knee capsule
- the GFR falls anterior to the ankle
- -> ankle dorsiflexion moment that is resisted by contraction os gastronemius soleus muscle complex
- ie in mid stance there is very little muscle activity required to maintain an up right position
13
Q
Where is the GRF in pre-swing?
A
- the force passes behind the knee
- acts as a flexor- reducing the work requirements for knee flexion
14
Q
How do orthosese function?
A
- By application of mechanical forces to the musculoskeletal system
15
Q
How can orthosis modify the system of external forces and moments across a joint?
A
-
Direct
- Control of moments about a joint
- control of translation forces across a joint
- control of axial forces across a joint
-
Static
- Control of line of action
16
Q
describe how orthosis control of moments across a joint?
A
- most common reason for prescribing orthosis
- modifying the moments about a joint may partially or totally restrict the rotational movement at the joint
- -> either a decrease in ROM about a particular axis or a limitation in number of axes about which motion may occur by
-
3 point fixation
- involves one force acting acting over the joint centre
- other 2 forces acting in oppposite direction to the first, placed proximal and distal to the joint
17
Q
describe how orthosis control of translational forces across a joint?
A
- Translational forces arise only when there is significant shear forces acting across the joint
- achieved by 4 point fixation across joint
- can be hinged to allow rotation
- e.g. KO used to prevent translation in the transverse plane in PCL rupture
18
Q
decribe how orthosis control of axia forces across a joint?
A
- load sharing between the anatomical structures and the orthotic exoskeleton
- useful for reducing pain in arthritic joints
19
Q
decribe how orthosis control of line of action of GRF?
A
- involves modification of the point of application and line of action of the GRF during either static or dynamic weight bearing
- particulary useful in modifying abnormally high moments about a joint but also chnage alignment of a joint
- e.g. lateral heel wedge, transfer GRF from medial aspect of a varus degenerate knee to the intercondylar eminence or lateral joint line
20
Q
name the materials used in orthotics?
A
- **Thermosetting plastics **
- Thermoforming plastics
- Self generating polyurethane foam
21
Q
What are the thermosetting plastics?
A
- Polyester resins
- can be moulded into permanent shape after heating
- don’t return to original consistency even after being reheated
- Formed by pouring liquid resins into moulds, mixed with a catalyst the polymerisation reaction of resin to set in a rigid form
- often used in prosthetics cf orthotics - where greater ridigity required
22
Q
What are thermoforming plastics?
A
- these soften when heated allowing reshaping by application of pressure
- harden when cool
- they can be **reshaped many times **
- subdivided into their moulding temperatures
-
High temperature thermoplastics
- require moulding between 120-190oC
- great skill required for manufacturing
- Ideal for high stress activities
- made by heating a sheet of polyethylene or polypropylene in a hot oven.
- final product is in either vacuum formed or moulded over a positive POP cast
- made for AFO/TLSO
-
Moderate temperature thermoplastics
- require moulding temp 100-120oC
- e.g.Plastozote foam made from polyethylene of closed cell construction
- very lightweight
- after heating in a hot-air oven it can be moulded directly on the patient as it has low heat conductivity & its sufaces cool rapidly
- commonly used for custom cervical collars, pressure distribution pads
-
Low temperature thermoplastics
- require moulding 80oC
- can be moulded in water bath ot hot air oven
- ideal for acute splinting
- moulded directly to the patient with minor modifications made using a gun/hair dryer
- less rigid and less durable
- cheaper, less time and skill for fabrication
- e.g. polycaprolactone (Polyform) to which synthetic rubber can be added
23
Q
What is the self generating polyurethane foam
A
- used in “neofract” for corset and braces
- freshly prepared foam is poured into a cotton pattern and distributed evenly with a roller
- the filled pattern is allowed to harden directly over the patient
- the custom-made cast is prepared in minutes and donned and doffed by using a zip fastener.
- polyurethane foam is used to make moulded cushions for wheelchairs adn can be as a filler in KAFO’s a nd shoes
24
Q
Name the types of insoles?
A
-
Simple
- off the shelf/fabricated w cast
- provide poor surface area contact
- little mechanical control
-
Total contact insoles
- made- initally imprint of pt foot & then casting of imprint w POP.
- A thermoplastic then moulded from the positive pop cast.
- most common type foot orthosis
-
Functional/biomechanical orthoses
- corrective insoles
- foot held in corrected position when cast is taken
- insole obtained therefore acts to correct underlying foot deformity when the deformity is flexible
- fixed deformities- require accomodative insole
25
When the limits of insoles are reached what is available?
* Custom made shoes
* corrective or accommodative
26
What are the heel modifications that can be made to shoes?
* altering heels; can be..
1. **Cushioned**
* wedge of compression rubber used to absorb impact at heel strike or w rigid ankle plantarflexion by reducing the knee flexion moment
2. **Flared**
* medial to _resist_ eversion and lateral to resist inversion
3. **Wedged**
* medial to promote inversion and lateral to promote eversion
4. **extended**
* thomas heel projects anteriorly on the medial side to provide support to medial longitudinal arch
5. **Elevated**
* shoe lift to compensate for fixed equinus deformity or LLD of \> 0.65cm
27
what can modifications can soles have?
* **Rocker bars**
* **convex structure placed posterior to MT head** shifting **rollover point from head to shaft**
* used for ulcers over MT in DM- see pic
* **Metatarsal bars**
* bar with flat surface placed posterior to MT head to relive pressure on heads
* **Wedges**
* medial to promote supination
* lateral to promote pronate
* **Flares**
* medial to resist eversion
* lateral to resist inversion
28
What modifications can be made to internal shoe heel modifications?
* **Cushion relief**
* soft pad with excavation placed under the painful point of the heel
* **Cups**
* rigid plastic inserts covering the plantar surface of the heel and extending posteriorly, medially and laterally to prevent lateral calcaneal shift in the flexible flat foot
* **Universty of Berkley labortatory insert**
* rigid prefabricated over a cast of the foot hled in max manual correction and encompassing the heel,midfoot with rigid posterior, medial and lateral walls. Used to control hindfoot valgus and midfoot pronation
29
Describe the internal modifications for insoles?
* **Metatarsal pads**
* domed pads designed to reduce stress from MT heads by transferring load to MT shafts in metatarsalgia
* **Inner sole excarvations**
* soft pad filled with compressed material placed under MT heads
* **Arch supports**
* medial arch support extending form half inch posterior to first MT head to anterior tubercle of the os calcis
30
what is the benefits of ankle foot orthosis?
* Used to **prevent or correct deformities** and **reduce weight bearing**
* Shown to **reduce the energy costs of ambulation** in wide variety of conditions- spastic diplegic cerebral palsy and lower motor weakness of poliomyelitis
31
What do plastic AFO consist of?
* Shoe inserts
* calf shell
* heel retaining strap
* calf strap attached more proximally
32
Can you name some AFO examples?
* **Posterior leaf spring**
* narrow calf shell adn narrow ankle behind malleloi to allow some flexibility
* used to compensate for weak ankle DF 9 prevents excessive equinus during heel strike or foot drop during swing
* **Solid AFO**
* wider calf shell with trim ant to malleoli
* prevents ankle DF/PF/varus/valgus
* **HInged AFO**
* adjustable ankle hinges used to desired range of DF/PF.
* prevents PF but allow DF during stance phase of gait
* **Ground reaction force**
* made with solid ankle at neutral. upper portion straps around ant tibia proximally to provide strong ground reaction support for pt weak triceps surae. Prevents knee hyperextension by creating a flexion moment at the knee
* **Dynamic AFO/ tone reducing afo**
* borad foot plate provides suppost sround most of foot, extending distally under the toes adn up over the medial and lateral aspect of the foot in order to maintain the subtalar joint in normal alignment
* in CP pts able to reduce tone in muscle groups above the brace so reduce tone and improve function- inhibition casting
33
what do metal and metal and plastic afo consist of?
* Shoe or foot attachment, ankle joint and 2 upright metal and lateral with a calf band connected proximally
* the mechanical ankle can control or assist ankle DF or PF by means of stop ( pins) or assist ) spring)
34
what do knee ankle foot orthosis consist of?
* AFO with metal uprights
* mechanical knee joint
* 2 thigh bands
* used in quads paralysis or weakness to maintain knee stability and control genu valgum or varum
* manufactured from metal - double upright metal KAFO most common
35
What does a trunk, hip knee ankle foot orthosis consist of?
* Spinal orthosis in addition to a HKAFO ( a hip joint andpevic band in addition to KAFO)
36
Name some paediatric orthoses?
* Denis brown spint - congential talipes equinovarus
* Pavlik harness for DDH
37
What are the complications of orthosis?
* **Psychosocial **
* **Physical**
* **compression phenoma**
* tight orthosis encircle limbs-\> compression of nerves/arteries/veins-\> pain/parathesia/imparied distal circulation and oedema
* **Heat and water retention**
* leading to maceration of skin, impaired wound healing, skin infection
* **Pt-orthosis interfacial effects**
* interface is defined as the junction between the body tissue and the orthosis and/or the support surface thru which forces transmitted
* -\> tissue necrosis/skin breakdown
* extrinisc over bony landmarks or due to intrinsic pt factors- paralysis, insensate, pvd
* reduce
* by **contouring** - prevent orthosis falling to the ground
* **good mechanical design-** leverage to reduce the amount of force exterted on the ground
* **adequate padding and large contact areas over which forces can ac**t
