13. ISPO WeltkongressPoster [3459] Abstract [634] | Thema: Orthetik

Page 1 of 4

AuthorKim, JangHwan (None KR)HanSeo univ. - prosthetics and orthotics

TitleDevelopment of Multi-linkage Orthotic Knee Joint for Paralysis

Coauthors

Lim KD, Yi JB

Summary

We developed 4-bar linkage knee joint attachable to KAFO. This new knee joint flex freely at

swing phase and lock geometrically at stance phase. There are no needs of any electric parts,

sensors, and mechanical accessories. The operation reliability was successfully evaluated at

3D gait lab.

Introduction

KAFOs are used in patients with severe knee extensor and hamstring weakness, structural

knee instability, etc. There are several types of orthotic knee joints. The single axis knee joint,

straight-set knee joint, drop lock, ratchet lock, and bail lock, posterior offset knee joint, and

so on. Recently stance control orthosis (SCO) was developed as an advanced orthotic joint.

Stance control orthotic knee joints are designed to allow free flexion of the knee in swing, while

providing full stability in stance by automatically locking on initiation of the stance phase of gait.

We developed an orthotic knee joint using 4-bar linkage polycentric technique realizing SCO.

The 4-bar linkage mechanism guarantees knee flexion at swing phase and stability at stance

phase by geometric locking. It has been verified so far in prosthetics. There are no needs of

electric power, sensor, connecting circuit, bulky upright, etc. The reliability of this function was

evaluated in 3D gait lab.

Methods

The geometric locking mechanism has been designed with consideration of biomechanical

aspects. We considered GRF, necessary moment at the knee, single equivalent force, etc. And

the functional and safe 4-bar mechanism was designed by relevant software for dynamics. Both

superior, inferior end for assembling upright was designed for compatibility with conventional

upright parts. Two same but symmetric joint parts was necessary on each leg. Therefore

13. ISPO WeltkongressPoster [3459] Abstract [634] | Thema: Orthetik

Page 2 of 4

locating those on precise symmetric position was very important. It was essential to confirm

parallel between two joint parts, and coincidence with every match axis of links. For guarantee

geometrical kinematics accurately, rigid cuff and secure bandage was applied to above and

below knee. Full leg length casting was necessary for rigid cuff. Operation test was performed

at 3D gait lab.

Results

Appropriate mechanical design was leaded by computing various biomechanical conditions.

Four bar structure fulfilled given conditions. Smoothness of rotation at each joint between

links is controlled by several steps. The range of motion goes through with normal range. The

dimension of the developed joint part is small enough through all directions. Those are 15*4*1.2

#. Aluminum alloy was selected for material. Consequently this joint is lightweight enough.

In fabricating KAFO with these joint parts, full leg length casting was performed for rigid

cuff forming. The rigid cuffs covered posterior half of circumference. The rigid cuffs were

thermoformed by polypropylene and leather bands attached to those. The anatomical reference

point to locate the joint part was apex of lateral epicondyle of femur and matching point of joint

part was anterior-superior one of four axes. To confirm coincidence of axes, long straight stick

passed through reference axes of two symmetric parts, piercing plaster model. Rest parts of

KAFO were conventional ones.

After fitting on subject with polio, no collapse was happening while wagging the CoG in

standing. As protracting pelvis of affected side and starting swing the same side leg, knee joint

of KAFO began flexion. As consummation of swing phase, orthotic knee joint was fully extended

and got ready for stable initial contact. In stance phase, knee joint showed secure stability.

Conclusion

In the meantime many knee joint mechanisms have challenged natural and safe knee motion.

With the posterior offset joint, it is difficult to balance stability and smooth swing. Horton’s one

has additional weight and decreased stability at initial contact. In the case of UTX, it is ankle

dependent mechanism so additional cable is needed. SPL type requires enough hip extension

muscle power. And it is inappropriate for full weight bearing. E-knee needs electric power so

13. ISPO WeltkongressPoster [3459] Abstract [634] | Thema: Orthetik

Page 3 of 4

additional equipments that battery, circuit, clutch, sensor, etc. are required. Accurate operation

is dependent on sensors at sole and logic algorithm.

This research has achieved lightweight, no bulky, no electric power, and reliably operated knee

joint development using polycentric mechanism. 4-bar linkage design fulfilled the requirements

of this development. However this specific design was for non-contracture knee. For various

knee contracture aspect, additional designs using different dimensions are required.

References

Braddom RL. 2007. Physical medicine and rehabilitation, 3rd ed. Elsevier Inc.

Hebert JS, Liggins AB. 2005. Gait evaluation of an automatic stance-control knee orthosis in a

patient with postpoliomyelitis. Arch Phys Med Rehabil 86:1676-1680

Irby SE, Bernhardt KA, Kaufman KR. 2007. Gait changes over time in stance control orthosis

users. Prosthet Orthot Int 31(4):353-361

Kaufman KR, Irby SE, Mathewson JW, et al. 1196. Energy-efficient knee-ankle foot orthosis: A

case study. J Prosthet Orthot 8(3):79-85

McMillan AG, Kendrick K, Michael JW, et al. 2004. Preliminary evidence for effectiveness of a

stance control orthosis. J Prosthet Orthot 16(1):6-13

Rosa J, Gamble JG. 1994. Human Walking, 2nd ed. Williams & Wilkins

13. ISPO WeltkongressPoster [3459] Abstract [634] | Thema: Orthetik

Page 4 of 4

Image: P6057816_None.JPG