A Device to Measure Ankle Proprioception in Children with Cerebral Palsy

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A Device to Measure Ankle Proprioception in
Children with Cerebral Palsy

• BME 401 Group 7
• Kiki Zissimopoulos
• Amy Nichols
• Raj Shani

Mentors Dr. Diane Damiano, Dwyane Maxam
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Outline

• Cerebral Palsy and Proprioception
• Current Testing Methods
• Need for Proprioception Test
• Design Specifications
• Design Alternatives
• Preliminary Analysis
• Schedule and Organization of Responsibilities

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Background

• Cerebral Palsy
• Chronic condition affecting over ½ million
  Americans.
• Results from brain damage before, during, or
  after birth impairing body movement and muscle
  control.
• Alters muscle tone, often causing stiff ankle
  tendons (E) and preventing the person from
  walking normally.

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Background cont.

• Surgical Treatment
• Lengthening the Achilles tendon decreases tendon
  stiffness, improves walking ability, but possibly
  decreases proprioception.
• Proprioception
• Sense of joint position in the absence of visual
  cues
• Crucial for everyday living (i.e. walking).

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Test Protocol

• Audio and visual cues are eliminated.
• Joint of interest is positioned by the tester and
  returned to the neutral starting point.
• Active proprioception test
• Patient must actively reproduce the same
  position.
• Passive proprioception test
• Patient must respond when the tester has reached
  the same position.

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Existing Proprioception Tests

• Platform
• Aircast
• Cuff
• Footclamp
• Manual

Platform (Gross)
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Existing Proprioception Tests

• Platform
• Aircast
• Cuff
• Footclamp
• Manual

Aircast (Grob)
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Existing Proprioception Tests

• Platform
• Aircast
• Cuff
• Footclamp
• Manual

Cuff (Good)
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Existing Proprioception Tests

• Platform
• Aircast
• Cuff
• Footclamp
• Manual

Foot Clamp (van Deursen)
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Need

• No test apparatus currently exists to accurately
  and quantitatively measure proprioceptive ability
  without tactile cues.
• Proprioceptive ability is not isolated.
• Our goal Create a device that tests ankle
  proprioception of cerebral palsy patients
  without providing tactile cues.

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Test Requirements

• Patients are tested pre and post surgery.
• Electric goniometer will measure angular ankle
  position and a motor will move the foot.
  (US PAT 4,442,606).
• Static test
• Match one foot to angular position of the other
  through verbal responses.
• Match picture to perceived ankle joint position.
• Dynamic test
• Respond when motion is detected.

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Design Requirements

• No tactile cues
• No audio or visual cues
• Comfortable
• Adjustable for children 7-17 years old
• Foot width - 3-5 in.
• Foot length - 4-10 in.
• Low velocity - 1-2 per second

• Outputs angle and velocity data
• Size - 2ft x 2ft x 3ft
• Total test time - under ½ hour
• Easy to use-setup in 5 minutes
• Costs under 10,000
• Safe - emergency release in under 5 seconds

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Design Ideas-Hydraulics

• Contacts side of foot only
• Smooth movement from motor powered pumps

Hydraulics Side Bar Stimulus Overload Polymer
Cast Track
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Design Ideas-Sidebar

• Sidebars keep foot rigid
• Motor acts as the ankle joint

Hydraulics Side Bar Stimulus Overload Polymer
Cast Arcing Track
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Design Ideas-Stimulus Overload

• Attempts to trick the body by applying forces
  opposite to motion through inflating air bags

Hydraulics Side Bar Stimulus Overload Polymer
Cast Arcing Track
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Design Ideas-Polymer Cast

• Eliminates tactile cues by distributing the
  forces in the polymer
• Motor drives the encasing box

Hydraulics Side Bar Stimulus Overload Polymer
Cast Arcing Track
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Design Ideas-Arcing Track

• Motor rotates foot in a smooth 40 arc with no
  tactile cues.
• Adjustable track radius for different sizes

Hydraulics Side Bar Stimulus Overload Polymer
Cast Arcing Track
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Preliminary Analysis

• Ankle rotation range 20 off neutral for
  dorsiflexion and plantarflexion
• Radius of rotation 5.08cm-15.24cm (2-6) based
  on foot length of 10.16cm-30.48cm (4-12)
• Maximum arc length range- 3.54cm-10.64cm
  (1.40-4.19 )

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neutral
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Preliminary Analysis (cont.)

• Velocity - 1-2 per second
• 0.0028 Hz.-0.0056 Hz.
• Maximum motor torque .99 Nm
• Foot weight estimated as 1.29 body weight (de
  Leva) and acts at the center of the foot.
• Achilles tendon force is 6.16 N, based on
  cerebral palsy specific data for muscle
  characteristics.

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Schedule
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Organization of Responsibilities
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References

• De Leva, Paolo. Adjustments to
  zatsiorsky-seluyanovs segmetn inertia
  parameters. J Biomech. 1996 29(9) 1223-1230.
• Good, Lars, et al. Joint position sense is not
  changed after acute disruption of the anterior
  cruciate ligament. Acta Orthop Scand 1999 70(2)
  194-198.
• Grob, K.R., et al. Lack of correlation between
  different measurements of proprioception in the
  knee. J Bone Joint Surg. 2002 84-B614-618.
• Gross, Michael T. Effect of recurrent lateral
  ankle sprains on active and passive judgments of
  joint position. Physical Therapy 1986 67(10)
  1505-1509.
• Van Deursen, Robert W.M., et al. The role of
  muscle spindles in ankle movement perception in
  human subjects with diabetic neuropathy. Exp
  Brain Res 1998 120(1)1-8.

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Contact Information

• Mentors
• Dr. Diane Damiano, PhD
• dld6830_at_bjc.org
• Dwyane Maxam
• dem6428_at_bjc.org
• Project Website
• http//cec.wustl.edu/bme401g7/

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Any questions??