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bmsc orthotics > Unit 2: Lower Limb Orthotics > Flashcards

Unit 2: Lower Limb Orthotics Flashcards

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

A

Active dorsiflexion beyond plantargrade

24
Q

How does weak/absent plantarflexion commonly present

A

Excessive dorsiflexion prior to heel off

25
Q

What orthosis is commonly used for weak/absent plantarflexion

A

Floor Reaction Orthosis: very rigid construction of the ankle section helps to resist large external dorsiflexion at midstance

26
Q

How has the Floor Reaction Orthosis design been improved

A

Including an articulation in the AFO to allow some plantarflexion at heel contact, cushion heel, rocker sole

27
Q

Consequence of weak pronator muscles

A

Foot hangs in varus, danger of further supination at foot contact leading to ligamentous injury

28
Q

Consequence of weak supinators

A

Foot valgus = creates abnormally high dangerous stresses in the medial longitudinal arch

29
Q

What orthosis is used for subtalar insufficiency

A

Polypropylene AFO: only able to eliminate subtalar motion because no designs are able to mimic subtalar joint motion

30
Q

How to patients with unilateral knee extensor weakness overcome their instability

A

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
Q

What two patterns of deformity are commonly seen in UMN lesion patients

A

Equinus and equinovarus

32
Q

What orthosis is used for UMN lesion patients with equinus foot deformity

A

Polypropylene AFO

33
Q

What is a problem with using a polypropylene AFO for equinus, and how can this be overcome

A

Prevents dorsiflexion during late stance or when performing activities such as squatting
Use an orthotic articulation which permits passive dorsiflexion whilst resisting plantarflexion

34
Q

How does an AFO control ankle plantarflexion (e.g. in cerebral palsy children)

A

Moves the GRF posteriorly during mid and late stance = reduces the external knee extension moment, creates an external hip extension moment

35
Q

Give a common cause of equinovarus

A

CVA

36
Q

What orthosis is used for equinovarus

A

Polypropylene AFO: specifically shaped to emphasise the ML sites of force application

37
Q

Give the common causes of impaired structural integrity of the ankle joint

A

Trauma and arthritis

38
Q

Describe the Patellar Tendon Bearing AFO

A

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
Q

How does the PTB help to treat severely impaired structural integrity of the ankle

A

Provides an alternative skeletal loading bearing area proximal to the ankle

40
Q

How should abduction/adduction instability be corrected

A

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
Q

What is the most common cause of AP instability

A

Rupture of the ACL

42
Q

When would a KAFO be used

A

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
Q

What are the 3 categories of applications of KAFO

A

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
Q

How can patients overcome unilateral knee extensor power weakness

A

Flexing their trunk anteriorly to create a stabilising external knee extension moment
Manually pushing their thigh posteriorly

45
Q

What are the most common UMN lesions which lead to KAFO prescription

A

Cerebral palsy, head injury and adult hemiplegia (due to stroke)

46
Q

What response does the hemiplegic patient commonly adopt to achieve stance phase stability

A

Mass extensor response: ankle plantarflexion, knee extension, anterior trunk flexion
Note: these can lead to the development of a painful hyperextended knee

47
Q

Describe the 3-force KAFO used to address the mass extensor response

A

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
Q

Identify the 3 main causes of loss of structural knee integrity

A 
Trauma
Joint disease (inflammatory or degenerative) 
Failed joint replacement
49
Q

Describe the KAFO design commonly used to compensate for loss of structural knee integrity

A

KAFO with a moulded plastic quadrilaterally shaped thigh section (which creates the weight-relieving surface)

50
Q

What are HKAFO usually prescribed for

A

Congenital hip abnormalities and paraplegia

51
Q

What are the 3 categories of ambulation that a HKAFO must facilitate

A

Stand and swing through
Swivel
Reciprocating gait

52
Q

Describe the stand and swing through mechanism

A

Conventional orthosis that incorporates locking hip and knee joints. Enables patient to stand and use walking aids to achieve swing through

53
Q

Describe a swivel mechanism

A

A standing frame to which swivel mechanisms are added under each foot.
Pivoting is achieved by lateral trunk movement

54
Q

Describe a reciprocating gait mechanism e.g. the Parawalker

A

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
Q

What is unique about the Reciprocating Gait Orthosis

A

Has a cable mechanism that imposes reciprocal action upon the orthotic hip joints

bmsc orthotics (5 decks)

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