Pathology Specific Orthoses:
Posterior Tibialis Dysfunction
(Adult Acquired Flatfoot)
Adult Acquired Flatfoot Pathology
Steroid use
Steroid injection
Rheumatoid arthritis
Chronic synovitis
Obesity
Avulsion
Adult Acquired Flatfoot
Focus of Intervention
Primary need is to address the abnormal
STJ axis position and resultant deformity
Stages of adult acquired flatfoot need to be
addressed with more aggressive
biomechanical intervention
Address with components related to
moment arms and axis location
Foot Orthoses
UCBL in-shoe device provided superior
restoration of both arch and hind foot
kinematics.
Imhauser, Foot Ankle Intl, 1999
Joint Physics
Subtalar Joint and it’s Axis
Concepts of Controlling the Hyper-pronated
STJ with Functional Foot Orthoses
Determination of STJ Axis Position
Orthotic Prescriptions for Controlling the
Hyper-pronated STJ
Linear Forces are Converted to
Rotational Forces
Moment of Force
M = F x D
M = Moment
F = Magnitude of Force
D = Distance (lever arm)
Physics
Lever Arm (Moment Arm)
The perpendicular distance from the line
of application of force to the joint axis
To Increase Moment
Increase Magnitude of Force
Increase Lever Arm
Joint Physics
Subtalar Joint and it’s Axis
Concepts of Controlling the Hyper-pronated
STJ with Functional Foot Orthoses
Determination of STJ Axis Position
Orthotic Prescriptions for Controlling the
Hyper-pronated STJ
STJA Position Manter, Root, et. al.
16 degrees from sagittal
42 degrees from transverse
STJA Position Exits Through Talar Head
Represents an
Average Only
STJA Deviation
Lateral Deviation
Medial Deviation
Subtalar Joint Axis Neutral STJ
Pronated STJ STJA Adducts with the Talus
“Medially Deviated Subtalar Joint
Axis”
Forces (Torques) Act Around
the Subtalar Joint Axis
Internal Torques
Muscle
External Torques Ground Reactive Forces
Orthotic Reactive Forces
STJA Deviation Changes the Length of the Lever Arm
Kirby, K. Rotational Equilibrium around the STJ axis.
JAPMA, 1987
To control STJ pronation, a FFO must act to
convert the GRF into an Orthotic Reactive Force
(ORF) which acts farther medial to the STJA
Standard Functional Foot Orthosis Effect On:
Normal STJA
Slight Supination Moment
Medially Deviated STJA
Large Pronation Moment
To control the Pes Planus type foot, you
must increase the ORF on the limited area
available medial to the subtalar joint axis
The Orthotic Prescription
Material
Size - Width and Heel Cup Depth
Positive Castwork
Posts
Top Cover
Forefoot Extensions
Special Additions
Material Selection: Enough Rigidity to Resist Deformation
Polypropylene: Vacuum Formed
Graphite / Fiberglass
EVA / Cork and Leather
Increased Width / Heel Cup Depth
Increased Surface Area Medial to STJA Longer Supination Lever Arm
Increased Supination Moment / Decreased Pronation Moment
x 22
x
Varus Wedge Effects: Change Position of Orthotic Force on Heel
Varus Wedge Effect
Increase Lever Arm Medial
to STJA
Increase Supination Moment
Medial Heel Skive (Kirby)
Inverted Techniques
Mildly Inverted
Highly Inverted (Blake)
Medial Heel Skive Technique Positive Cast Modification
Allows Varus Wedge Effect Without Jamming of
Medial Column
Increases Supination Moment Across STJA
Kirby, K. The Medial Heel Skive Technique. JAPMA, April 1991,
Shifts Center of
ORF Medial
Adds Varus
Wedge to Heelcup
Medial Heel Skive Prescription
Intrinsic Accommodations Sweet Spot to Accommodate Navicular
Mark Prominence with Lipstick
Vacuum Formed Accommodation Filled with Poron
Topcover - Glue Heel Only
x x
Rearfoot Post
Stabilizes Orthosis in Shoe
Not Necessarily Corrective
x x
x
Topcover
x
PTD Prescription Sample Material: 1/4” Polypropylene
Width: Medial Flange
Heel Cup Height: 22mm
Positive Cast : Medial Heel Skive
Positive Cast : Navicular Sweet Spot
Posting: 0/0 (flat) Rearfoot Post
Covers: EVA to Sulcus.
Glued Heel Only
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