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bmsc orthotics > Unit 2: Lower Limb Orthotics > Flashcards

Unit 2: Lower Limb Orthotics Flashcards

(55 cards)

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1
Q

Describe an orthosis/orthotic device

A

An externally applied device used to modify the structural and functional characteristics of the neuromuscular and skeletal systems

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2
Q

What does the external force system comprise of

A

3 orthogonal forces: axial, ML and AP

3 moments acting in planes perpendicular to the force components

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3
Q

What is the internal force system

A

The action of body tissues which act to balance external forces
NOTE: the ground/foot force system, the internal force systems and the external force systems are all dependent upon one another

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4
Q

What is the orthosis/body force system

A

The system of forces generated between an orthosis and the body. Acts to resist or prevent abnormal motion, in effect modifying the internal force system

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5
Q

What is the direct action of the orthosis

A

The mechanism of an orthosis brought about by encompassing an impaired joint or body segment

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6
Q

What is the indirect action of the orthosis

A

The beneficial changes in external force system brought about at joints/segments that are not encompassed by the orthosis

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7
Q

What 2 aspects of orthosis design will affect its ability to create a desired improvement in function

A

Choice of components

Position of attachments

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8
Q

What forces must an orthosis/body force system need to resist or control directly

A

External moment acting about a joint
Normal force acting across a joint
Axial force across joint/segment
Normal force and moment acting on a body segment

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9
Q

What system must be employed by an orthosis to resist/control external moments NOT across a joint

A

Three-point force systems: aim to position the middle force as close to the joint as possible, with the other end forces as far away as possible

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10
Q

What system must be employed by an orthosis to resist/control external moments crossing a joint

A

Four-point force systems: ensure middle forces are as close to the joint as possible, with the end forces as far away as possible

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11
Q

What pressure system is used to resist both external moments and the normal force acting on a limb

A

Circumferential pressure system

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12
Q

What 4 components do all modern orthoses have

A

Interface components
Joints
Structural components
Cosmetic components

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13
Q

Give extrinsic factors that affect the response of soft tissue to its environment

A

Pressure
Shear
Microenvironment of the interface

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14
Q

Give intrinsic factors that affect the response of soft tissue to its environment

A 
Reduced sensation
Diminished attention
Paralysis
Diminished tissue turgor
Failed vasomotor reflexes
PVD
Malnutrition
Systemic disease
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15
Q

Factors that improve load transfer at the interface component

A

Large area of support, soft interface material, larger radius of curvature, contour the interface to the body shape, ensure good fit between orthosis and body

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16
Q

Name the 4 types of joint control

A

Free motion
Limited range of motion
Locked
Assistance or resistance to motion

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17
Q

Key qualities of orthotic structural components

A

Ability to withstand loads/avoid deformation, good cosmesis, lightweight inexpensive

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18
Q

Give examples of cosmetic components

A

Fillers, covers, sleeves and shells

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19
Q

What are contemporary lower limb orthoses commonly made from

A

Moulded thermoplastic shell interface components and a moulded thermoplastic foot piece

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20
Q

What are the 3 main categories of AFO application

A

Conditions which result in muscle weakness
UMN lesions
Conditions which lead to pain/instability due to loss of structural integrity

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21
Q

What problems will result from weak and absent dorsiflexion muscle control

A

Foot slap and foot drop

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22
Q

What orthosis is used to compensate for weak/absent dorsiflexion

A

Ortholen Posterior Leafspring Orthosis: joint function is achieved by the posterior strut = bends under loading for controlled plantarflexion, returns to neutral when load is relieved

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23
Q

What motion are no existing orthosis designs capable of providing

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A

Active dorsiflexion beyond plantargrade

24
Q

How does weak/absent plantarflexion commonly present

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A

Excessive dorsiflexion prior to heel off

25
What orthosis is commonly used for weak/absent plantarflexion
Floor Reaction Orthosis: very rigid construction of the ankle section helps to resist large external dorsiflexion at midstance
26
How has the Floor Reaction Orthosis design been improved
Including an articulation in the AFO to allow some plantarflexion at heel contact, cushion heel, rocker sole
27
Consequence of weak pronator muscles
Foot hangs in varus, danger of further supination at foot contact leading to ligamentous injury
28
Consequence of weak supinators
Foot valgus = creates abnormally high dangerous stresses in the medial longitudinal arch
29
What orthosis is used for subtalar insufficiency
Polypropylene AFO: only able to eliminate subtalar motion because no designs are able to mimic subtalar joint motion
30
How to patients with unilateral knee extensor weakness overcome their instability
Lean forwards over the affected leg = brings GRF in front of the knee joint to create a stabilising moment Note: if unable to do so, may require a Floor Reaction Orthosis
31
What two patterns of deformity are commonly seen in UMN lesion patients
Equinus and equinovarus
32
What orthosis is used for UMN lesion patients with equinus foot deformity
Polypropylene AFO
33
What is a problem with using a polypropylene AFO for equinus, and how can this be overcome
Prevents dorsiflexion during late stance or when performing activities such as squatting Use an orthotic articulation which permits passive dorsiflexion whilst resisting plantarflexion
34
How does an AFO control ankle plantarflexion (e.g. in cerebral palsy children)
Moves the GRF posteriorly during mid and late stance = reduces the external knee extension moment, creates an external hip extension moment
35
Give a common cause of equinovarus
CVA
36
What orthosis is used for equinovarus
Polypropylene AFO: specifically shaped to emphasise the ML sites of force application
37
Give the common causes of impaired structural integrity of the ankle joint
Trauma and arthritis
38
Describe the Patellar Tendon Bearing AFO
Moulded plastic design consisting of a posterior ankle-foot shell that extends to the level of the knee crease, to which a hinged anterior shell (extending from mid-patella to ankle level) is attached
39
How does the PTB help to treat severely impaired structural integrity of the ankle
Provides an alternative skeletal loading bearing area proximal to the ankle
40
How should abduction/adduction instability be corrected
3 force system that applies a medial (for valgus) or lateral (for varus) force plus a distal and proximal force on the opposite side of the affected limb. Should also include an orthotic knee joint
41
What is the most common cause of AP instability
Rupture of the ACL
42
When would a KAFO be used
When patient has functional disorder affecting both the knee and ankle Where the severity of the knee disorder and magnitude of controlling forces precludes the use of a KO Where a KO would be preferred but there are problems with suspension
43
What are the 3 categories of applications of KAFO
Conditions that result in muscle weakness UMN lesions that result in hypertonicity or spasticity Loss of structural integrity of the knee or hip joints
44
How can patients overcome unilateral knee extensor power weakness
Flexing their trunk anteriorly to create a stabilising external knee extension moment Manually pushing their thigh posteriorly
45
What are the most common UMN lesions which lead to KAFO prescription
Cerebral palsy, head injury and adult hemiplegia (due to stroke)
46
What response does the hemiplegic patient commonly adopt to achieve stance phase stability
Mass extensor response: ankle plantarflexion, knee extension, anterior trunk flexion Note: these can lead to the development of a painful hyperextended knee
47
Describe the 3-force KAFO used to address the mass extensor response
One posteriorly behind the knee, the other two anteriorly proximally and distally Also incorporate an orthotic knee joint: limits knee extension to just short of 180 degrees and permits near normal range of flexion
48
Identify the 3 main causes of loss of structural knee integrity
``` Trauma Joint disease (inflammatory or degenerative) Failed joint replacement ```
49
Describe the KAFO design commonly used to compensate for loss of structural knee integrity
KAFO with a moulded plastic quadrilaterally shaped thigh section (which creates the weight-relieving surface)
50
What are HKAFO usually prescribed for
Congenital hip abnormalities and paraplegia
51
What are the 3 categories of ambulation that a HKAFO must facilitate
Stand and swing through Swivel Reciprocating gait
52
Describe the stand and swing through mechanism
Conventional orthosis that incorporates locking hip and knee joints. Enables patient to stand and use walking aids to achieve swing through
53
Describe a swivel mechanism
A standing frame to which swivel mechanisms are added under each foot. Pivoting is achieved by lateral trunk movement
54
Describe a reciprocating gait mechanism e.g. the Parawalker
Specially designed low friction orthotic hip joint with an extremely rigid alloy orthotic structure. Rigid structure reduces the degree of lateral trunk sway needed, and the low friction hip allows the free leg to swing forwards under the action of gravity
55
What is unique about the Reciprocating Gait Orthosis
Has a cable mechanism that imposes reciprocal action upon the orthotic hip joints

bmsc orthotics (5 decks)

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