METAL AFO Flashcards
The average midsagittal line for a normal limb will intersect what three points?
Perineum bisect, a point 15mm medial to the leg at the knee joints axis and a point 30mm medial to the medial malleolus at the ankle joint axis
A midsagittal line falling more than 15 mm medial for the knee indicates
Genu varum
A midsagittal line falling more than 30mm medial from the medial malleolus indicates
Genu valgum
A shoe attached to a metal AFO must have simultaneous
Full heel contact and forefoot contact under the metatarsal heads
The location of the mechanical ankle joint axis should be
At the distal tip of the medial malleolus
What is the relationship between the proximal edge of the calf band and then fibular neck?
They should be 20mm apart
What should be the average clearance between the apex of the lateral malleolus And the lateral mechanical ankle joint?
5mm
What is the line progression?
The direction of forward progression
What is toe out?
The angular relationship between the line off progression and the longitudinal aspect of the foot.
What is tibial torsion?
The relative external rotation of the ankle joint axis with respect to the knee joint axis
A distal perpendicular from the bisect of the ankle joint axis will allow determination of the
Presence of a fixed subtalar deformity
Why is 3mm added to the amount that the medial sidebar is anteriorly deflected to accommodate external rotation of the mechanical ankle joint axis.
Because the mechanical ankle joint diameter is greater than that of the anatomical ankle joint diameter
When using 5/8 inch (15mm)x 3/16 (5mm) inch sidebar stock, the best estimate for the length of a calf band is?
Half the maximum anatomical, calf diameter plus 37 mm (1 1/2inches)
Stirrup size is determined by measuring?
The length from one mechanical axis to the other in the uncountered condition
The midsagittal line determines alignment in?
The coronal plane
The length of a solid stirrup is the algebraic sum of
Twice the ankle joint height, twice the sole thickness, heel width, plus 6mm
The ideal clearance between the medial surface of the sidebars and the skin is
3-6 mm
Why is it generally best not to contour the sidebars in the area of the calf band?
The band can be riveted without excessive stress
Why is the calf band length greater than half the circumference of the anatomical calf?
To accommodate the padding plus half the sidebar width twice
After anterior deflection of the medial sidebar/ankle joint assembly, why are the ankle joints externally rotated?
To make the mechanical joint surface perpendicular to the ankle joint axis.
When anteriorly deflecting the medial sidebar/ankle joint assembly, what is the advantage of utilizing two contours vs one?
So that the relationship between the mechanical ankle joint and the stirrup is the same as it is laterally
The advantage of using a single contour in the medial sidebar to approximate the anatomical ankle joint axis is
Improved cosmesis, less built in stress and ease of fabrication
What is the static posture of a patients talocrural joint when wearing a standard metal AFO when the lateral sidebar is perpendicular to the ground and the shoe has a 5/8 inch heel
Plantarflexion
If a patient has a fixed subtalar varus deformity, what kind of wedge would you recommend?
A medial heel wedge
If a patient has a fixed subtalar valgus deformity, what kind of wedge would you recommend?
A lateral heel wedge
If a patient has a flexible subtalar valgus, to what side of the shoe would you attach the correction strap?
Medial
If a patient has a flexible subtalar varus, to what side of the shoe would you attach the correction strap?
Lateral
What event does a cushion heel simulate?
Plantar flexion at loading
What event does a rocker bar simulate?
Heel rise and toe off
When might a cushioned heel be used on a AFO with restrained dorsiflexion and plantar flexion?
To reduce knee flexion thrust at loading
When might a rocker bar be used?
When forefoot motion is undesirable
With what type of mechanical ankle joint adjustment might you use both a cushion heel and a rocker bar?
Restrained dorsiflexion and plantarflexion
What can be the eventual consequence of not accommodating tibial torsion in a free motion AFO?
Iatrogenic varus deformity
Why should the tongue of a stirrup be contoured before attaching to the shoe?
To prevent deformation of the shoe
Marks left by a contouring instrument should be
Removed to eliminate failure causing stress risers
