Lab 3: Plastic Hinged AFO, IMO, SMO, KOs, KAFOs Flashcards
What types of joints can be present on a HAFO?
Overlap, gillette, Gaffney, Oklahoma, insert stirrup, spring loaded dorsiflexion assist, tamarack, wafer
Describe the pros and cons of an overlap joint
Pro: inexpensive, strong, simple construction
Cons: very wide so if pt walks with a narrow BOS they can trip easily
What is a Gaffney joint?
Single-axis metal joint that is not as durable
What is an Oklahoma style joint?
Plastic joint that is designed and reinforced in a more streamlined manner
Describe how a spring loaded dorsiflexion assist joint works
Spring is compressed during pushoff phase of gait and then release at the start of swing phase
Describe a tamarack and gillette joint
Allow for a simple hinged articulation and may assist with dorsiflexion depending on style
Describe a wafer joint
Metal joints designed to be durable and adjustable for both plantarflexion and dorsiflexion. Motion assist can be incorporated.
Con: heavier and more expensive
What is the function of a plantarflexion stop?
Decrease plantarflexion when there is a lack of active dorsiflexion or control necessary for adequate swing clearance
What is the function of a check strap?
Restricts the amount of dorsiflexion or plantarflexion. Can be positioned either posteriorly or anteriorly
When is a check strap indicated?
Pt ambulates with a flexed gait pattern
Why would a HAFO be prescribed over an SAFO?
Allows for varying degrees of movement at the ankle to provide the opportunity for greater east and efficiency in functional movements
When is an HAFO indicated?
Pt has a fair amount of control at the trunk and hip and least control at the knee
When is a SAFO indicated?
Trunk, hip, and knee control is compromised but still desire to be functional in an upright position
What does IMO stand for?
Inframalleolar Orthoses
Describe the characteristics of a post
Found on the inferior surface of orthosis, made out of plastic or foam
What is the function of a post?
Hold the orthosis steady in the shoe – does not add height to orthosis
What does SMO stand for?
Supramalleolar Orthosis
How can you differentiate between an SMO and IMO?
SMOs extend above the malleoli and IMOs are trimmed below the malleoli
Describe the force system of an SMO for supination
Primary: originates laterally at the area of the talus and is directed medially
Secondary: originates medially at the calcaneus and is directed laterally
Secondary: originates medially at the 1st metatarsal head and is directed laterally
Describe the force system of an SMO to control pronation
Primary: originates medially at the area of the talus and navicular and is directed laterally
Secondary: originates laterally from the calcaneus and is directed medially
Secondary: originates laterally from the 5th metatarsal head and is directed medially
Compare the rationale for prescribing a IMO over shoe modifications
An IMO corrects with closer contact to the foot and can be more effective. Shoe modifications can accommodate changes in foot size
What motions can an SMO control?
Supination, pronation, and plantarflexion depending on the structure of the posterior superior trimline
Describe the force system to control plantarflexion in an SMO
Primary: originates superior and anterior at the calcaneal strap and is directed posterior and inferior
Secondary: originates inferior at the orthosis at the location of the metatarsal heads and is directed superior
Secondary: originates posterior from the superior trimline and is directed anterior
Does an IMO or SMO have greater control of triplanar motion?
SMO because the increased surface area coverage creates better leverage to control supination and pronation
How does the height of the posterior superior trimline of an SMO affect plantarflexion control?
The higher the trimline, the greater leverage
Why would you recommend a SMO over an IMO?
If the medial and lateral control is not adequate with an IMO or if plantarflexion control is also needed
What type of device is displayed in the image?
Supracondylar Shell KAFO or Floor Reaction Orthosis (FRO)
What motions are controlled by a FRO
Knee: Hyperextension, valgus, varus
Ankle: some plantarflexion, dorsiflexion, supination, or pronation
What does FRO stand for?
Floor Reaction Orthosis
Describe the force system to control hyperextension with a FRO
Primary: originates posterior at the posterior superior margin of the orthosis and is directed anterior
Secondary: originates anterior at the anterior superior portion of the orthosis and is directed posterior
Secondary: originates anterior at the anterior inferior portion of the orthosis and is directed posterior
Describe the force system to control valgus with a FRO
Primary: originates medially at the central medial portion of the orthosis and is directed laterally
Secondary: originates laterally at the superior lateral aspect of the orthosis and is directed medially
Secondary: originates laterally at the inferior lateral aspect of the orthosis and is directed medially
Describe the force system to control varus with a FRO
Primary: originates laterally at the central portion of the orthosis and is directed medially
Secondary: originates medially at the superior medial aspect of the orthosis and is directed laterally
Secondary: originates medially at the inferior medial aspect of the orthosis and is directed laterally
What is special about the design of a FRO?
The ankle joint is set in plantarflexion and supported by an appropriately height heeled shoe
What effect does the ankle position of a FRO have on the knee and hip?
Plantarflexed position shifts the GRF anterior to the knee and hip causing knee extension and hip flexion
What are disadvantages of the FRO design?
Biases the knee toward extension without extending the surface area higher than the femoral epicondyles. Pt needs to have adequate hip extensor strength to counterbalance. Can actually cause destabilizing if not properly prescribed
When is a FRO indicated?
If the pt demonstrates a crouched gait pattern
What is the proper positioning of the superior portion of a conventional KAFO?
Extends to the upper third of the thigh with 3-4” of clearance in the groin area
What is the proper positioning of the superior lateral portion of a conventional KAFO?
Below the greater trochanter
What motions are controlled in standing with KAFO and why is this unique?
Mechanism locks to control knee hyperextension, flexion, varus, and valgus.
Describe the force system to control knee hyperextension with a KAFO
Primary: originates posterior from a combination of the inferior thigh band and calf band and is directed anterior
Secondary: originates anterior from the thigh strap and is directed posterior
Secondary: originates anterior from the calf strap and is directed posterior
Describe the force system to control knee flexion with a KAFO
Primary: originates anterior from the knee pad OR a combination of the supra and infra patellar straps
Secondary: originates posterior from the superior thigh band and is directed anterior
Secondary: originates posterior at the calf band and is directed anterior
Describe the force system to control valgus with a KAFO
Primary: originates medially at the medial condylar pad and is directed laterally
Secondary: originates at the superior portion of the lateral bar and is directed medially
Secondary: originates at the inferior portion of the lateral bar and is directed medially
Describe the force system to control varus with a KAFO
Primary: originates from the lateral condylar pad and is directed medially
Secondary: originates at the superior portion of the medial bar and is directed laterally
Secondary: originates at the inferior portion of the medial bar and is directed medially
What is the function of the knee joints in a KAFO?
Designed to be locked in a stationary position to provide necessary stability for standing and ambulation
What is the most common type of joint that is used for KAFOs?
Single axis knee joint
Describe an adjustable or fan design knee joint
Allows for the knee joint to be locked even though the patient may not possess full knee extension
What are the the pros and cons of a drop lock?
Pro: inexpensive, simple in design, requires little maintenance and chance of breakdown
Con: difficult to manipulate and release when standing
What is a spring loaded pull rod?
Added to a ring or drop lock to make it easier to release when in standing. Decreased the distance the individual needs to reach down
Describe when a bale release would be attached to a pawl lock
When a dual locking mechanism is indicated both on the medial and lateral sides. It allows for simultaneous release of both locks and it triggered by pushing the bale
What is a con of a bale release attached to a pawl lock?
It extends out posteriorly and may be accidentally released by bumping into something
What are the indications for a KAFO?
Compromised motor control of the foot, ankle, knee, and hip. Possible trunk control deficits as well
What patient population will typically use a KAFO?
SCI, spina bifida, polio, post-polio syndrome. Occasionally stroke or CP
What is unique about a Craig-Scott KAFO?
The ankle set is set at 10 degrees of dorsiflexion
If the ankle component of a KAFO is set to 10 degrees of dorsiflexion, how would it affect the alignment of the knee and hip?
Knee: bias toward flexion because GRF is posterior to the knee
Hip: bias the hip toward flexion because GRF is anterior to the hip
Functionally, how would a Craig-Scott orthosis benefit a SCI patient?
A pt with little to no active hip extension is able to maintain the position by resting on the Y ligament allowing them the opportunity to maintain standing and ambulate without extending the brace past the knee
What motions are controlled with a plastic KAFO?
When locked, knee hyperextension, flexion, valgus, varus
Describe the force system to control knee hyperextension with a plastic KAFO
Primary: originates posterior from a combination of the inferior portion of the thigh shell and the superior portion of the calf shell and is directed anterior
Secondary: originates anterior from the thigh strap and is directed posterior
Secondary: originates anterior from the inferior leg strap or calcaneal strap and is directed posterior
Describe the force system to control knee flexion with a plastic KAFO
Primary: originates anteriorly from a combination of the supra and infra patellar straps and is directed posterior
Secondary: originates from the posterior portion of the thigh shell and is directed anterior
Secondary: originates posteriorly from the heel cup and is directed anterior
Describe the force system to control valgus with a plastic KAFO
Primary: combined forces originate from the inferior medial portion of the thigh shell and the superior medial portion of the AFO shell and are directed laterally
Secondary: originates laterally from the superior portion of the thigh shell and is directed medially
Secondary: originates laterally from the inferior portion of the AFO shell and is directed medially
Describe the force system to control varus with a plastic KAFO
Primary: combined forces originating from the inferior lateral portion of the thigh shell and the superior lateral portion of the AFO shell and is directed medially
Secondary: originates medially at the superior portion of the thigh shell and is directed laterally
Secondary: originates medially at the inferior portion of the AFO shell and is directed laterally
What are the benefits of a hybrid KAFO?
Flexibility in brace length, can be worn under clothes, is more cosmetically acceptable, lightweight
What does KO stand for?
Knee Orthoses
What are the three categories of KOs?
Flexible, semi-rigid, rigid
What is the function of a flexible KO?
Compress tissue to minimize edema and keep the joint and soft tissue warm, proprioceptive feedback
What is the general function of a semi-rigid KO?
Check or limit movement
What is the general function of a rigid KO?
3-point pressure system to control or restrict motion
What motions are controlled with an elastic knee orthosis?
No motions
What are indications for a flexible KO?
OA, edema, minor knee sprains
What type of orthosis is an Elastic KO with M-L Supports?
Semi-rigid
What motions does an Elastic KO with M-L Supports control?
No true control, does limit some valgus and varus
What is the purpose of a Elastic KO with M-L Supports?
Same as a flexible KO. Compression, heat to area, reduce edema, proprioception.
When is a Elastic KO with M-L supports indicated?
OA, edema, minor knee sprains
What type of orthotic is a knee immobilizer?
Semi-rigid
Describe the optimal positioning for a knee immobilizer
Extend superiorly to the upper third of the thigh, extend inferior to 1-1.5” above the malleoli, and anterior cut out over the patella
Does a knee immobilizer control motion?
Provide tactile input to increase kinesthetic awareness leading to decreased knee movement. No motions are truly controlled because there are no three point pressure systems
What is the function of a knee immobilizer?
Decrease movement at the knee following surgery or trauma. Can also be used to assist upright postural control where there is weakness at the knee following a stroke
What are conditions that may be indicated for a knee immobilizer?
TKR, acute knee trauma, weakness at the knee secondary to stroke, MS, Guillian Barre
What is the advantage of a knee immobilizer over an elastic KO?
Longer leverage and vertical bars provide greater support
What type of orthosis is an adjustable knee immobilizer?
Semi-rigid
Does an adjustable knee immobilizer control motion?
Technically no because it is a semi-rigid design with no three point pressure systems. Provides tactile cues to decrease motion
What would you need to add to an adjustable knee immobilizer in order to allow it to control motion?
Bands
What are the indications for an adjustable knee immobilizer?
Acutely for post operative or traumatic rehab
Why is the adjustable knee immobilizer beneficial compared to an elastic KO with or without M-L support?
It is more restrictive because of the increased length and rigid construction even though it does not contain horizontal bands
What type of orthosis is a resting splint?
Rigid
What motions are controlled with a resting splint?
All motions due to total contact between the orthosis and the knee
Extension, flexion, varus, valgus
How is knee flexion controlled with a resting splint?
Primary: originates anteriorly from a combination from the supra and infra patellar straps and is directed posteriorly
Secondary: originates posteriorly at the superior margins of the orthosis and is directed anterior
Secondary: originates posteriorly at the inferior margins of the orthosis and is directed anteriorly
How is hyperextension controlled with a resting splint?
Primary: originates at the posterior medial portion of the orthosis and is directed anterior
Secondary: originates at the anterior superior portion of the orthosis and is directed posterior
Secondary: originates at the anterior inferior portion of the orthosis and is directed posterior
How is valgus controlled with a resting splint?
Primary: originates from the central portion of the medial orthosis and is directed laterally
Secondary: originates from the superior lateral aspect of the orthosis and is directed medially
Secondary: originates from the inferior lateral aspect of the orthosis and is directed medially
How is varus controlled with a resting splint?
Primary: originates from the central portion of the lateral aspect of the orthosis and is directed medially
Secondary: originates medially at the superior aspect of the orthosis and is directed laterally
Secondary: originates medially at the inferior aspect of the orthosis and is directed laterally
What is the function of a resting splint?
Maintain or increase knee ROM. Can be used only at night as an attempt to gain ROM while not restricting function during the day
What conditions are indicated for a resting splint?
Pathologies that involve knee flexion contractures. Stroke, CP, MS, MD, ALS, scleroderma, TBI
What movements are controlled with a Swedish Knee Cage?
Hyperextension
Describe the force system to control hyperextension with a Swedish Knee Cage
Primary: originates posterior at the popliteal strap and is directed anterior
Secondary: originates anterior at the thigh strap and is directed posterior
Secondary: originates anterior at the leg strap and is directed posterior
Does a Swedish Knee Cage control varus or valgus?
Arguably no because the medial and lateral bars are short with minimal leverage and not positioned optimally
What conditions are indicated for a Swedish Knee Cage?
Mild hyperextension, patients with arthritis, stroke, hypotonia
What are disadvantages of a Swedish Knee Cage?
Bulky, protrudes vertically when sitting
What type of design is a Three Way Knee Stabilizer?
Rigid
What motions are controlled with a Three Way Knee Stabilizer?
Hyperextension, varus, valgus
Describe the force system to control hyperextension with a Three Way Knee Stabilizer
Primary: originates posterior at the popliteal band and is directed anterior
Secondary: originates anterior at the anterior thigh band is directed posterior
Secondary: originates anterior at the anterior leg band and is directed posterior
Describe the force system to control valgus with a Three Way Knee Stabilizer
Primary: originates medially from a central portion of the medial bar and is directed laterally
Secondary: originates laterally from the superior portion of the lateral bar and is directed medially
Secondary: originates laterally from the inferior portion of the lateral bar and is directed medially
Describe the force system to control varus with a Three Way Knee Stabilizer
Primary: originates laterally from the central portion of the lateral bar and is directed medially
Secondary: originates medially from the superior portion of the medial bar and is directed laterally
Secondary: originates medially from the inferior portion of the medial bar and is directed laterally
What are the indications for a Three Way Knee Stabilizer?
Mild hyperextension, valgus, or varus
What pts may benefit from a Three Way Knee Stabilizer?
Arthritis, stroke, hypotonia
Why might a Three Way Knee Stabilizer be preferred over a Swedish Knee Cage?
Controls medial and lateral motion and also is more cosmetically acceptable
What motions are restricted by a Molded Plastic Solid Knee Orthosis?
Hyperextension, valgus, varus
Describe the force system to control hyperextension with a Molded Plastic Solid Knee Orthosis
Primary: originates posterior at the posterior superior margin of the brace in the popliteal area and is directed anterior
Secondary: originates anterior at the superior portion of the brace and is directed posterior
Secondary: originates anterior at the inferior portion of the brace and is directed posterior
Describe the force system to control valgus with a Molded Plastic Solid Knee Orthosis
Primary: originates medially at the central portion of the medial aspect of the brace and is directed laterally
Secondary: originates laterally from the superior border and is directed medially
Secondary: originates laterally from the inferior border and is directed medially
Describe the force system to control varus with a Molded Plastic Solid Knee Orthosis
Primary: originates laterally from the central portion of the lateral aspect of the brace and is directed medially
Secondary: originates medially from the superior border and is directed laterally
Secondary: originates medially from the inferior border and is directed laterally
When is a Three Way Knee Stabilizer indicated?
Mild to moderate hyperextension, valgus, varus
If a KO has rotary control, what design is the device?
Rigid
What are options for modifications for KOs?
Neoprene sleeves worn underneath, extensive anterior shell derotation straps, oblique bands, tibial tuberosity band with derotation cable
Describe the optimal fit for a KO with a polycentric axis?
Extends to middle third of thigh and middle third of lower leg
Does a KO with a polycentric axis control flexion?
No
Describe the force system that controls hyperextension in a KO with a polycentric axis
Primary: originates posterior from the thigh band is directed anterior
Secondary: originates anterior at the thigh strap or band is directed posterior
Secondary: originates anterior at the lower leg strap or band and is directed posterior
Describe the force system that controls valgus in a KO with a polycentric axis
Primary: originates medially from the central portion of the medial bar or condylar pad and is directed laterally
Secondary: originates laterally from the superior lateral bar and is directed medially
Secondary: originates laterally from the inferior lateral bar and is directed medially
Describe the force system that controls varus in a KO with a polycentric axis
Primary: originates laterally from the central portion of the lateral bar or condylar pad and is directed medially
Secondary: originates medially from the superior portion of the medial bar and is directed laterally
Secondary: originates medially from the inferior portion of the medial bar and is directed laterally
What type of force system controls rotation and translation at the knee?
4 point pressure system
Describe the force system that controls rotation and translation in a KO with a polycentric axis
Primary: originates anteriorly from the thigh band is directed posterior
Primary: originates posterior from the supra popliteal strap and is directed anterior
Secondary: originates anterior from the infra patellar strap and is directed posterior
Secondary: originates posterior from the leg strap and is directed anterior
What does a polycentric joint design allow for?
Flexion and extension around an instantaneous axis of rotation which closely mimics the instantaneous axis of rotation of the knee
When is a KO with a polycentric axis indicated?
Significant damage to ligamentous structure of the knee or instability where the individual will stay active. Also used for post-surgical in sub-acute or long term rebab
