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Design Innovation Paper

Development and Evaluation of a Mechanical Stance-Controlled Orthotic Knee Joint With Stance Flexion

[+] Author and Article Information
Jan Andrysek

Bloorview Research Institute,
Holland Bloorview Kids Rehabilitation Hospital,
150 Kilgour Road,
Toronto, ON M4G1R8, Canada
e-mail: jandrysek@hollandbloorview.ca;
Institute for Biomaterials and Biomedical Engineering, University of Toronto,
27 King's College Circle,
Toronto, ON M5S, Canada

Matthew J. Leineweber

Bloorview Research Institute,
Holland Bloorview Kids Rehabilitation Hospital,
150 Kilgour Road,
Toronto, ON M4G1R8, Canada
e-mail: mleineweber@hollandbloorview.ca

Hankyu Lee

Institute for Biomaterials and Biomedical Engineering,
University of Toronto,
27 King's College Circle,
Toronto, ON M5S, Canada
e-mail: hankyu.lee@mail.utoronto.ca

1Corresponding author.

Contributed by the Mechanisms and Robotics Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received March 22, 2016; final manuscript received November 15, 2016; published online January 16, 2017. Assoc. Editor: David Myszka.

J. Mech. Des 139(3), 035001 (Jan 16, 2017) (7 pages) Paper No: MD-16-1234; doi: 10.1115/1.4035372 History: Received March 22, 2016; Revised November 15, 2016

Stance-control orthotic knee joints stabilize the knee joint during the weight-bearing portion of gait without restricting swing-phase flexion, thus achieving a more normal gait for individuals with quadriceps muscle weakness. These devices must be designed around well-defined stance-control strategies that enable or hinder joint motion at specific events during the gait cycle. This paper presents a new type of stance-control strategy and a novel stance-controller design. Pilot clinical testing was performed on a prototype, demonstrating feasibility of this approach for providing reliable knee stability while facilitating swing-phase flexion. In particular, 44 deg of swing-phase flexion and 15 deg of stance-phase flexion were achieved during level walking. Further testing is needed in situ to provide additional validation and assess other mobility conditions.

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References

Figures

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Fig. 1

The SCOKJ triggering events are shown in relation to the knee moments from KAFO users [22]. Key trigger events for disengaging the lock 1 (t1 and t2) are defined by the threshold indicated by the dashed line (0.15 N·m/kg). The shortest time the lock must remain in the disengaged mode to allow for swing flexion (ttimermin) and the longest time it can remain in the disengaged mode (ttimermax) before initiation of stance phase of subsequent gait cycle.

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Fig. 2

(a) Prototype SCOKJ shown locked and unloaded, (b) subjected to a flexion moment at distal axis (B) as occurs in midstance showing stance flexion as the die spring (3) is compressed, (c) with the occurrence of an extension moment at the proximal axis (A) causing the knee to unlock, and (d) and flexed during swing-phase

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Fig. 3

External knee moment averaged over three trials each for regular walking speed of 1.05 m/s and fast walking speed of 1.41 m/s [22]. The vertical bars identify the meanand standard deviation of the timing for trigger events t1, t2, and t3, as well as the toe-off event. Lock disengagement is first triggered as the knee flexion moment drops below the threshold (0.15 N·m/kg), and the lock becomes fully disengaged at the minimum flexion moment (t2) when the lock teeth fully clear, which corresponds to about 20 deg of knee flexion. The lock must be reset before weight bearing of the subsequent step (t3). Maximum and minimum ttimer values are represented by solid and dashed arrows, respectively.

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Fig. 4

Prototype SCOKJ worn by participant

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Fig. 5

Knee angles achieved during gait using a KAFO. The shaded areas around the locked-knee and stance-controlled knee angle profiles represent the standard deviation of the three trials at each timepoint.

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Fig. 6

External knee moments and corresponding knee angles from gait analysis with SCOKJ. The threshold for triggering point is based on theoretical calculation and corresponds well with loading curve which begins to sharply rise once maximum stance flexion has been achieved.

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