







































All articles are permanently available online to the public without restrictions or subscription fees. They are free to be used, cited, 

and distributed, provided that appropriate acknowledgment is included. Authors retain the copyright of their original contributions 

and grant the Canadian Online Publication Group (COPG) a license to publish the article and identify itself as the original publisher. 

CPOJ articles are licensed under the Creative Commons Attribution 4.0 International License. 

 

CPOJ Website: https://jps.library.utoronto.ca/index.php/cpoj/index 

Editorial Office: cpoj@online-publication.com    

ISSN: 2561-987X 

CPOJ is a member of, and subscribes to the principles of, the Committee on Publication Ethics (COPE). CPOJ articles are freely 

accessible on PubMed Central® (PMC). 

 

 

VOLUME 7, ISSUE 2 

 2024 
 

RESEARCH ARTICLE 

 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered 

hip joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

  

 

https://jps.library.utoronto.ca/index.php/cpoj/index
mailto:cpoj@online-publication.com
https://publicationethics.org/about/our-organisation
https://pmc.ncbi.nlm.nih.gov/journals/?term=%22Canadian+Prosthetics+%26+Orthotics+Journal%22
https://members.publicationethics.org/members/canadian-prosthetics-orthotics-journal
https://doi.org/10.33137/cpoj.v7i2.44494
https://pmc.ncbi.nlm.nih.gov/journals/?term=%22Canadian+Prosthetics+%26+Orthotics+Journal%22


 

1 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

 

 

RESEARCH ARTICLE 

 

DEVELOPMENT AND EVALUATION OF AN ANTERIORLY MOUNTED MICROPROCESSOR-

CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen K1, Baddour N1, Cho L1, Langlois D2, Dumond P1, Lemaire E.D3,4* 

1. Department of Mechanical Engineering, Faculty of Engineering, University of Ottawa, Ottawa, Canada. 
2. Össur, Grjothals 1-5, 110 Reykjavik, Iceland.  
3. Department of Medicine, Faculty of Medicine, University of Ottawa, Ottawa, Canada. 
4. Center for Rehabilitation Research and Development, Ottawa Hospital Research Institute, Ottawa, Canada. 
 
  
 

 

 

 

  

 

 

 

 

 

 

 

 

 

 

 

INTRODUCTION   

Lower limb prostheses facilitate daily ambulation for people 

with amputation. Microprocessor powered lower limb 

prosthetics technology, primarily for knee joints, can 

improve balance and stability1 and can lower energy 

expenditure, leading to increased daily activity and overall 

satisfaction.2  However, similar  solutions  for  hip  joints  are  

 

 

 

not available. Considering that walking performance is 

greatly affected by proximal amputation locations,3 many 

people with hip disarticulation (HD) and hemipelvectomy 

(HP) amputation experience difficulty walking with 

prostheses. As a result, more than 50% of such individuals 

opt for alternative solutions such as wheelchairs for daily 

mobility.4 

A powered prosthetic hip joint could solve common 

challenges in current hip-knee-ankle-foot (HKAF) 

prostheses, namely stability, metabolic cost, and range of 

motion, allowing people to recover a more natural gait.5 

Commonly used prosthetic hip joints can be grouped into 

single-axis or polycentric joints, based on the number of 

pivot points and linkages involved in the mechanism. While 

 
OPEN  ACCESS 

ABSTRACT 

BACKGROUND: Prosthetic solutions for individuals with hip disarticulation and hemipelvectomy 

amputations currently rely exclusively on passive hip joint mechanisms. Although powered knee and 

ankle joint prostheses have improved gait in people with amputation, no powered hip joint options are 

commercially available. 

OBJECTIVE: To develop and validate the mechanism, structural integrity, and design of an anteriorly 

mounted powered hip joint prosthesis. 

METHODOLOGY: A microprocessor-controlled powered hip joint prosthesis (PHP) was developed, 

incorporating a cable-and-pulley transmission system. Stress calculations and Finite Element Analysis 

(FEA) were performed to ensure that the device can withstand the forces from daily activities. The 

prototype underwent mechanical strength testing in accordance with International Organization for 

Standardization (ISO) 15032:2000 standards, ensuring suitability for user loads of up to 100 kg. For 

functional testing, three able-bodied individuals were video recorded while walking with the power hip 

in a prosthesis simulator. For each participant, hip angles and stride parameters during level walking 

were assessed by analyzing five gait cycles. 

FINDINGS: The novel PHP met most of the design criteria; however, it protruded 56 mm anteriorly 

from the lamination plate, exceeding the specified criterion of 20 mm. The joint's range of motion 

included 22° of extension and 145° of flexion. The joint prototype's height was 347 mm, and it weighed 

3.9 kg. Furthermore, it passed ISO 15032:2000 strength tests, withstanding a 3360 Newton (N) load 

without failure. The device successfully enabled able-bodied individuals to walk using a hip 

disarticulation simulator and supported a 98 kg user during level walking.   

CONCLUSION: The microprocessor-controlled PHP exhibited successful performance in both 

mechanical strength and functional testing. Future work is needed to optimize and assess the design, 

which could reduce the device's weight and size. A complex control system to adjust gait based on 

pelvic motion is currently under development. 

 

 

ARTICLE INFO 

Received: December 10, 2024 

Accepted: January 31, 2025 

Published: February 7, 2025 
 

CITATION 

Brannen K, Baddour N, Cho L, Langlois 

D, Dumond P, Lemaire E.D. 

Development and evaluation of an 

anteriorly mounted microprocessor-

controlled powered hip joint prosthesis. 

Canadian Prosthetics & Orthotics 

Journal. 2024; Volume 7, Issue 2, No. 7. 

https://doi.org/10.33137/cpoj.v7i2.4449

4 

KEYWORDS 

Microprocessor-Controlled Prosthesis; 

Powered Hip Joint; Hip Disarticulation; 

Hemipelvectomy; Prosthesis Design; 

Amputation; Lower Limb Amputation; 

Hip–Knee–Ankle–Foot Prosthesis 

 

* CORRESPONDING AUTHOR: 

Professor Edward Lemaire, PhD 

Affiliation: Department of Medicine, Faculty of Medicine, University of 
Ottawa, Ottawa, Canada. 

E-Mail: elemaire@uottawa.ca 

ORCID ID: https://orcid.org/0000-0003-4693-2623 

 

Journal Homepage: https://jps.library.utoronto.ca/index.php/cpoj/index 

Volume 7, Issue 2, Article No. 7. 2024 

 

 

https://doi.org/10.33137/cpoj.v7i2.44494
https://doi.org/10.33137/cpoj.v7i2.44494
https://doi.org/10.33137/cpoj.v7i2.44494
mailto:elemaire@uottawa.ca
https://jps.library.utoronto.ca/index.php/cpoj/index


 

2 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

polycentric joints like the Ottobock Helix 3D have improved 

gait compared to other devices,4 any passive hip joint 

requires the user to generate hip moments by using lumbar 

spine and pelvis movements for propulsion. This comes 

with the disadvantage of high energy expenditure while 

walking,3-6 asymmetrical gait,7 and an increased risk of 

long-term injury from musculoskeletal imbalances.8 

Microprocessor-controlled knee joints have better capability 

to react to user movement, detecting harmful movements 

like trips and stumbles to reduce injury risk.9 These devices 

can also adapt to various walking environments (e.g., level 

ground, ramp, stairs). Given that the average adult performs 

approximately 60 sit-to-stand movements daily,10 the added 

support and assistance from a powered prosthesis could 

reduce sit-stand asymmetry and load on the intact leg in 

individuals with amputation. A powered prosthetic hip joint 

could enable step-over-step stair ascent, a capability 

currently lacking in people with HD and HP amputation.11 

A powered prosthetic hip joint was reported by Ueyama et 

al.,12 who prototyped a device using direct current (DC) 

motors positioned within the thigh to power the hip and knee 

joints, with the joints sharing microcontroller boards, battery, 

and sensor data. An able-bodied participant successfully 

walked with the prosthesis, but the device required users to 

wear the battery in a waist bag and the prosthesis would not 

fit under clothing.  

A laterally mounted powered hip joint prosthesis was 

previously developed by Mroz et al.13 with the hip axis of 

rotation similar to the anatomical joint center. A cable driven 

transmission system transferred motor torque from the 

prosthetic thigh to the hip axis of rotation. The thigh chassis 

that housed the battery and electronics was separately 

validated.14 A weight bearing strut with double row steel ball 

bearings provided clearance for the device to swing 

beneath the pelvis.13 Able-bodied participants successfully 

walked with the laterally mounted PHP using a prosthesis 

simulator. Although this prototype successfully met most of 

the design requirements, there is still room for improvement 

in terms of weight and size. 

This paper explored the design and development of the 

main mechanical and structural components of an anteriorly 

mounted PHP, focusing on the rope and pulley transmission 

system that drives the mechanism. The anteriorly mounted 

design provides a compact system with the motor and 

electronics in the thigh, distal to the joint center of rotation. 

A successful PHP could greatly enhance safe mobility for 

people with HD or HP amputations. 

METHODOLOGY 

Design Requirements 

Based on existing international standards, literature review, 

the research team's clinical experience working with HD, HP 

or transfemoral amputation, and discussions with experts, 

the following design criteria were selected:  

• Joint angular velocity of at least 150 °/s.15,16 

• Maximum hip moment of 96 Nm to accommodate for a 

100 kg user.17,18 

• Joint range of motion of 130° flexion and 20° 

extension.18 

• Device weight should remain under 4 kg. This is 

compared to Össur’s Power Knee weighing 3.2 kg using 

the same actuator and battery.19 

• Device strength based on ISO 15032:2000 standards for 

prosthetic hip joints:20 

o Withstand 2240 N load for 30 s without 

deformation >15 mm, and 3360 N without ductile 

failure. 

o Joint must withstand 2x106 cycles from 50 N to 

1330 N without failure. 

• Must comfortably fit under user clothing: 

o Anterior protrusion less than 20 mm from the 

center of lamination plate. 

o Lateral protrusion less than 80 mm from center of 

lamination plate.21 

o Medial protrusion less than 50 mm from center of 

lamination plate. 

• Device length must remain under 378 mm (using 

anthropometric data, thigh length is 0.245*height, or 378 

mm for the 15th percentile women height).21 

• No finger traps or sharp edges for user safety. 

Design and development of PHP prototype 

The PHP main components (Figure 1) were designed using 

SolidWorks software (Version 2020). All metal components 

were made with aluminum 2024-T4 or 17-4 PH stainless 

steel, except for the off-the-shelf parts like screws and 

retaining rings. To make the prototype lighter, aluminum 

was used as much as possible, but steel was needed for 

parts requiring more strength. Note that the actuator is 

located below the joint to minimize anterior protrusion. 

Actuator torque is transmitted through the cable and pulley 

to the joint center.22  

The cable and pulley transmission system consists of four 

equally sized pulleys connected by two high strength steel 

cables (Figure 2). When torque is applied by the actuator to 

the bottom pulley, tension is applied to the cable and the 

assembly rotates around the top pulley in the opposite 

direction. Much like a belt drive transmission, the 

mechanism transfers torque over an extended distance with 

less components and weight. Pulleys diameters are also 

constrained since a small diameter requires greater tension 

on the cable to achieve the same torque (Figure 2). 
Therefore, 52 mm diameter pulleys were chosen to maintain 

the system’s integrity while balancing performance and 

compactness. 

 

https://doi.org/10.33137/cpoj.v7i2.44494
https://www.ottobock.com/en-ca/product/7E10


 

3 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

Figure 1: Powered hip joint components. Transmission system: 

Drive train composed of four pulleys of equal diameter and steel 

cables enabling joint flexion and extension (steel cables are not 

shown in this figure); Shafts: Structural components that bear user 

weight and tension from the pulleys. The proximal shaft connects 

the top hinge and bearing housing, and the distal shaft applies 

torque to the bottom pulleys; Bearing housing: Connects to the top 

of the actuator and facilitates joint rotation around the top shaft; Top 

hinge: Interface between the lamination plate and joint center; 

Lamination plate: Plate embedded in the prosthetic socket to attach 

the joint; Actuator: Össur Power Knee™ microprocessor-controlled 

motor modified for the PHP, providing torque and power to the 

system; Mounting components: Attachment ring and medial 

attachment piece secures the actuator to the attachment plate 

(chassis’ top plate); Chassis: Contains the electronic and the 

battery (Össur Power Knee). 

 

The cables were crossed in a figure-eight configuration, to 

ensure that the input torque from the motor and the reaction 

torque from the fixed pulleys (top) are in the same direction. 

Without a counteracting torque to establish equilibrium, the 

entire system rotates. Pulleys of equal diameter were 

selected, ensuring equal speed and torque between the top 

and bottom pulleys, to deliver the required 96 Nm of torque 

and 150°/s angular velocity. The pulleys were machined 

from 17-4 PH H900 steel to withstand high radial loads 

imposed by the cable and were designed to have a minimal 

diameter to reduce weight and space. The PHP pulleys 

were designed to allow the rope to anchor inside the part, to 

prevent slipping (Figure 2). The rope loop fits around a 

groove on the inside of the pulley and a hole on the top 

allows the rope to stick out and wrap around the pulley. 

High strength ropes or cables are required to meet the load 

requirements and provide better flexibility, and greater 

strength. To achieve a 96 Nm hip moment with a 52 mm 

diameter pulley, 4200 N of tension must be applied to the 

rope. Liquid crystal polymer (LCP) ropes such as VectranTM 

(https://kuraray.us.com/products/fibers/vectran/) meet 

these requirements, but steel cabling was selected for the 

initial prototype testing due to ease of crimping on 

terminators (Figure 2). 

The top hinge is secured to both the top shaft and lamination 

plate (Figure 1), while the bottom hinge is mounted on 

bearings. The bearing housing connects to a female 

pyramid adapter that is secured to its male counterpart on 

the actuator (Figure 2). Needle roller bearings were selected 

for this application for their ability to handle high radial loads 

while occupying minimal space.  

Like many transmission systems, the cable and pulley 

system must be pre-tensioned to ensure control 

responsiveness. If slack exists at an idle position, the 

actuator must first turn to take up the slack before joint 

movement can occur. For optimal performance, the joint 

must rotate synchronously with the actuator to avoid 

backlash caused by the oscillating nature of the 

mechanism. This issue was addressed by implementing a 

novel tensioning system consisting of multiple keyways on 

the top shaft and pulleys. The shaft contains eight equally 

spaced keyways, while the pulleys contain nine. This results 

in 72 possible orientations of the top pulleys where the top 

pulleys can be rotated and secured every 5° via a 

compatible keyway (Figure 3). Additionally, the system 

requires the medial and lateral pulleys to be tensioned in 

opposite directions, necessitating the use of two separate 

pulleys on the same shaft. 

Two main mechanisms were used to mount the PHP to the 

top plate of an aluminum chassis that holds the battery and 

other electrical components (Figure 4). A cylindrical groove 

was machined out of the chassis’ top plate to ensure full 

contact with the actuator’s bottom. The attachment ring 

contains a circular bolt pattern that fastens the ring to the 

circumference of the actuator. Two tapped holes were 

located underneath the attachment ring to secure the ring to 

the chassis’ top plate, restricting movement of the actuator’s 

outer casing. An additional medial attachment piece was 

fastened to the medial side of the actuator’s center, 

providing a secondary bracing mechanism to prevent the 

actuator from lifting off the chassis. 

The PHP prototype was constructed from an assembly of 

machined parts and off the shelf components. Mechanical 

drawings with appropriate dimensions and tolerances for 

each part were made before machining.  

Lamination 

plate 

Top hinge 

Battery 

Chassis 

Chassis’ top 

plate  

Medial 

attachment 

Actuator 

Bearing housing 

Electronic 

Attachment 

ring 

Pulley 

Shafts 

Transmission 

system  

M
o
u

n
ti
n
g
 c

o
m

p
o

n
e

n
ts

  

https://doi.org/10.33137/cpoj.v7i2.44494
https://kuraray.us.com/products/fibers/vectran/


 

4 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

An Össur Power Knee™ microprocessor-controlled motor 

was modified for the PHP, providing torque and power to 

the system. The lamination plate was designed to fit a 

prosthesis simulator that allowed able bodied participants to 

test the prototype.23 

Testing and Validation 

     Static Load Testing 

Static load testing ensured that the PHP was strong enough 

to withstand operating loads of a 100 kg person, using the 

procedures outlined in ISO 15032:2000 Prostheses – 

Structural testing of hip joints.20 Two testing conditions were 

evaluated: medial-lateral (ML) and anterior-posterior (AP) 

extension (Figure 5 and Figure 6). The PHP was tested in a 

servo hydraulic testing system. This study only explores 

prototype functionality under short-term use.  

Since the servo hydraulic testing system could only move 

along one axis, an adjustable testing rig was developed. 

The PHP top hinge was bolted onto an aluminum block 

attached to a pole and adjustable moment arm. The bottom 

of the chassis was attached to a similar assembly by a 

pyramid adapter. The testing procedure was as follows:  

 

Figure 2: Left: Schematic of the PHP and a pulley; Middle: Illustration of the steel ropes and pulleys; Right: Free body diagram of the crossed 

cable system, where T1 is the input torque from the actuator acting on the driving pulley, F12 is the tensile force from the cables on the pulleys, 

M2 is the reaction moment on the fixed pulley shaft, R1, and R2 are the reaction force of the cable force on the pulleys. 

 

Figure 3: Offset keyway tensioning solution. The red key demonstrates one of the pulley positioning possibilities. 

Top hinge 

Bottom hinge 

Female pyramid 

adapter 

Distal pully (medial) 

Distal pully (lateral) 

Actuator 

Thigh 

chassis 

Steel ropes for 

medial pulleys 

Steel ropes for 

lateral pulleys 

F12 

F12 

R 2 
M 2 

R 1 

T 1 

X 

X 

Shaft contains eight equally 

spaced keyways 

Pulleys contains nine 

equally spaced keyways 

Female adapter 

Actuator with male adapter 

Lamination plate 

Red key 

https://doi.org/10.33137/cpoj.v7i2.44494


 

5 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

1.   Set force to a 1024 N settling load and hold for 30 s. 

2.   Return load to zero. 

3.   Increase load at a rate of 200 N/s until 3360 N. 

4.   Return load to zero. 

The ML test was set up in the fully extended position, as 

shown in Figure 5. All moment arm lengths and angles were 

based on the ISO 15032:200 0 medial lateral loading 

conditions. 

       Functional Testing 

The functional testing protocol was approved by the 

University of Ottawa Office of Research Ethics and Integrity. 

Functional testing was performed by three able-bodied 

participants (members of the research team) on a 

prosthesis simulator23 that enables them to walk on a HKAF 

prosthesis. Informed consent was obtained from all 

participants, and the inclusion criterion was being able-

bodied without any balance issues.  

The assembly consisted of the PHP, Össur Rheo 3 knee 

joint, and Össur Pro-Flex XC foot. Participants wore an 

elevated outsole on the intact limb (left leg) to create 40 mm 

ground clearance for the right foot during stance (Figure 7). 

In this setup, only the prosthesis simulator and the left leg 

contacted the ground.23 Participant subjective feedback was 

also recorded comparing the PHP to previous Helix3D 

walking tests. Each participant was first trained on the 

simulator using the OttoBock Helix 3D joint and learned to 

walk comfortably before continuing with trials using the 

PHP. One or two canes were also used by the participants 

for support and safety. The participants were given one 

training session to familiarize themselves to walking with the 

PHP on the simulator and one testing session where the 

data was recorded.  

For functional testing, a simple control system was 

implemented for the PHP. It applied a predetermined and 

repeated gait cycle, tuned to operate at a specific pace to 

provide a comfortable gait pattern for all users. This cycle 

began at 40° flexion at heel strike and then extended to 20° 

extension. Once full extension was reached, the joint swung 

to 44° flexion and slowly returned to the initial condition of 

40° flexion. A 2.5 s stride time was implemented to suit the 

participants. PHP gait profile used for functional testing was 

illustrated in the authors’ previous publication.13 

For functional testing, five gait cycles were video recorded 

using a smartphone where no large stumbles were present 

and where the participant did not contact the floor with their 

prosthetic side natural foot. The videos were analyzed using 

the Kinovea video annotation tool to measure the hip angle 

(angle between the torso and the line connecting the hip 

joint and the knee) and determine stride parameters. Initial 

contact and toe-off times were used to identify the step 

times of each stride for each participant. 

 

 

Figure 4: Left: Attachment ring and medial attachment piece bracing the outer casing of the actuator to the top plate of the electronics 

chassis; Middel: The thigh chassis that housed the battery and electronics; Right: Joint dimensions. 

Medial 

attachment 

 

3
4
7

 m
m

 

1
7
1

 m
m

 

Chassis’ top plate with 

a cylindrical groove 

Attachment 

ring 

 

https://doi.org/10.33137/cpoj.v7i2.44494


 

6 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

 

 

 

Figure 5: Left: Medial-Lateral mechanical testing (ISO-15032:2000) conditions for the powered hip prosthesis; Right: Setup for static load. 

 

 

 

Figure 6: Left: Anterior-posterior mechanical testing (ISO-15032:2000) conditions for the powered hip prosthesis; Right: Setup for static load. 

Applied force 

Applied force 

Applied force 

Applied force 

Mounting block 

Mounting block 

Load application 

point 

Load application 

point 

Adjustable 

testing rig 

Adjustable 

testing rig 

https://doi.org/10.33137/cpoj.v7i2.44494


 

7 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

Figure 7: Hip disarticulation simulator23 setup with PHP, Össur 

Rheo 3 knee joint, and Össur Pro-Flex XC foot. Participants wore 

an elevated outsole on the intact limb to create 40 mm ground 

clearance for the right foot during stance. 

RESULTS 

Successful construction of the prototype validated the PHP 

manufacturing and assembly methods. The device weighed 

a total 3.9 kg, including the battery, electronics, and chassis.  

This prototype, similar to the Ottobock Helix 3D, features 

right and left configurations. In this study, a right PHP was 

manufactured and tested. 

Static load test results  

The test procedure was the same for both ML and AP, with 

the only difference being the loading conditions. Figure 8 

depict the force and displacement versus time profiles of the 

ML test and AP tests, respectively. Both tests withstood the 

3360 N ultimate strength test, displaying no signs of ductile 

fracture or plastic deformation. The ML test displayed a 

maximum displacement of 8.5 mm, whereas the AP test 

displayed less displacement at 4 mm (Figure 8). 

Functional testing results 

Three male volunteers (members of the research team) 

participated in functional testing (Table 1). Heel contact and 

toe-off times were used to identify the step times of each 

stride for each participant. The results of the five-stride test 

are shown in Figure 9. 

Maximum flexion and extension angles were identified in 

Table 2. The average range of motion during level walking 

was 47.2 ± 6.4°, which remained within the sufficient 

preprogrammed range of 64°. 

The average step time on the prosthetic side averaged 0.63 

times the intact side. The average swing time for the intact 

side was 0.29 ± 0.04 s and the average prosthetic leg swing 

time was 1.08 ± 0.10 s (Table 3). 

 

 

 

Figure 8: Top: PHP force and displacement profiles for medial-

lateral static load testing; Bottom: PHP force and displacement 

profiles for anterior-posterior static load testing. 

 

Table 1: Participant information. 

Participant A B C 

Sex Male Male Male 

Age (years) 44 28 25 

Height (cm) 178 180 175 

Weight (kg) 95 95 98 

Number of canes 
used by participants 

1 2 2 

 

0

1

2

3

4

5

6

7

8

9

0

500

1000

1500

2000

2500

3000

3500

4000

0 20 40 60 80 100

D
is

p
la

c
e
m

e
n
t 

(m
m

)

F
o
rc

e
 (

N
)

Time (s)

Force Displacement

0

1

2

3

4

5

0

500

1000

1500

2000

2500

3000

3500

4000

0 20 40 60 80 100

D
is

p
la

c
e
m

e
n
t 

(m
m

)

F
o
rc

e
 (

N
)

Time (s)

Force Displacement

40 mm ground 

clearance 

40 mm outsole 

https://doi.org/10.33137/cpoj.v7i2.44494


 

8 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

Table 2: Functional testing range of motion. 

Participant 
Maximum 

flexion (°) 

Maximum 

extension (°) 

Range of motion 

(°) 

A 21.1 ± 4.0 19.3 ± 1.7 40.4 ± 4.3 

B 41.4 ± 2.5 4.3 ± 8.9 45.7 ± 9.2 

C 39.3 ± 2.5 16.1 ± 3.5 55.3 ± 4.3 

Average 33.9 ± 3.1 13.2 ± 5.6 47.2 ± 6.4 
 

Table 3: Functional testing gait parameters with percentages of 

average stride time. 

Participant A B C Average 

Stride time (s) 
2.35 ± 

0.07 

2.38 ± 

0.10 

2.45 ± 

0.09 

2.39 ± 

0.09 

Step 

time 

(s) 

Prosthetic 
1.50 ± 
0.10 

(64 %) 

1.19 ± 

0.06 

(50%) 

1.24 ± 

0.08 

(50%) 

1.31 ± 

0.08 

(55%) 

Intact 

2.04 ± 

0.06 

(88%) 

2.09 ± 

0.02 

(89%) 

2.09 ± 

0.10 

(86%) 

2.07 ± 

0.07 

(88%) 

Swing 

time 

(s) 

Prosthetic 

0.85 ± 

0.07 

(36%) 

1.18 ± 

0.14 

(50%) 

1.22 ± 

0.08 

(50%) 

1.08 ± 

0.10 

(45%) 

Intact 
0.27 ± 
0.02 

(12 %) 

0.27 ± 

0.03 

(11%) 

0.34 ± 

0.05 

(14%) 

0.29 ± 

0.04 

(12%) 

Double support 

time (s) 

0.94 ± 

0.16 

(40%) 

0.91 ± 

0.08 

(38%) 

0.89 ± 

0.06 

(36%) 

0.91 ± 

0.11 

(38%) 

Cadence 

(steps/min) 
51.2 ± 1.4 

50.6 ± 

2.2 

49.0 ± 

1.9 

50.3 ± 

1.8 

Step time ratio 
0.73 ± 

0.05 

0.57 ± 

0.03 

0.59 ± 

0.06 

0.63 ± 

0.05 
 

All three participants stated that the PHP was easier to 

operate than the non-powered Helix3D joint, specifically 

noting that manual swinging and large pelvic rotation were 

not necessary for propulsion (subjective feedback). The 

participants also noted that the additional weight of the PHP 

compared to the Helix3D did not cause any problems. 

 

Figure 9: PHP hip flexion angle vs time across 5 strides for 

participant A (blue), participant B (red), and participant C (green). 

Design Requirements Evaluation 

The final design tested in this study met most of the design 

criteria (Table 4).   

DISCUSSION 

A novel microprocessor-controlled PHP was designed and 

evaluated for both strength and function. The pulley and 

cable power transmission system was successful in 

transmitting rotational power from the actuator to the hip 

joint. The final design met most of the design criteria, 

including mechanical strength tests. The PHP was also 

tested with able-bodied participants using a hip 

disarticulation prosthesis simulator, where ambulation was 

successful. 

The device weighed 3.9 kg, putting the PHP under the 4.0 

kg weight limit. The functional testing participants noted that 

this 3.9 kg weight did not feel heavy while walking or 

noticeably impede their motion. The anterior protrusion 

criterion was 20 mm, but the prototype tested in this study 

protruded 56 mm. Future work is needed to optimize and 

assess the design, which could reduce the device's weight 

and size. 

The design requirement for the PHP was to support users 

up to 100 kg. The PHP successfully supported a 98 kg user 

during functional testing, which is close to the required 100 

kg. The PHP also successfully passed ISO mechanical 

testing designed for users up to 100 kg. The strength 

requirements outlined in ISO 15032:2000 were to withstand 

a 2240 N load for 30 s without failure or deformation greater 

than 15 mm, withstand a 3360 N load without ductile failure, 

and withstand 2×106 cycles between 50 N and 1330 N 

without failure. The PHP withstood a 3360 N load without 

failure or deformation greater than 15 mm. Cyclical testing 

was not conducted on the PHP; however, calculations and 

FEA simulations indicate that the device should be able to 

withstand fatigue from the cycles outlined in the ISO 

standard.  

During level walking, the PHP achieved an average of 13.2 

± 5.6° of extension and 33.9 ± 3.1° of flexion (Figure 9). The 

maximum extension and flexion measured with a protractor 

were 22° and 145°, respectively, successfully surpassing 

the 20° hip extension and 130° hip flexion requirements. 

The final PHP power transmission gear ratio was 1:1. 

Therefore, the device should have the same maximum 

torque and angular velocity as the Össur Power Knee™ 

microprocessor-controlled motor. The maximum actuator 

torque is 96 Nm and the maximum angular velocity is 

300°/s, reaching the outlined 96 Nm and 150°/s outlined 

criteria. The actual hip moment was not measured; 

however, moments were enough to successfully propel all 

three functional testing participants forward and support 

body weight, allowing level ground walking. 

Geometric constraints were established to ensure the PHP 

could fit comfortably under a user’s pants. The first 

-30

-20

-10

0

10

20

30

40

50

0 2 4 6 8 10 12 14

H
ip

 a
n
g
le

 (
°

fl
e
x
io

n
)

Time (s)

Participant A Participant B Participant C

https://doi.org/10.33137/cpoj.v7i2.44494


 

9 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

geometric restriction was that the PHP could not protrude 

more than 20 mm from the top of the lamination plate. The 

final prototype for initial testing protruded 56 mm anteriorly, 

failing to meet the criterion. Even though this criterion not 

met, this prototype could still be accommodated under 

loose-fitting pants. The PHP could also not protrude more 

than 80 mm laterally or 50 mm medially from the center of 

the lamination plate. 71 mm lateral protrusion and 50 mm 

medial protrusion were measured on the final device. The 

device length was also controlled to ensure a large 

population could use the device. 

The PHP could not have any uncovered finger traps. A 

cover was designed to go over the pulley system, where the 
main finger traps occurred. However, the cover no longer fit 

over the pulleys when the steel cables were used for 

functional testing. A cover that encompasses the entire 

device would also be more successful because there is still 

potential for a finger to be caught between the bearing 

housing and the lamination plate with the current design. 

Therefore, this requirement was only partially met and could 

be improved upon. 

From the functional test results, discrepancies in the joint 

range of motion data were present, where the recorded 

range of motion was 8.3° less than the joint’s pre-

programed range of motion. This difference was likely the 

result of a difference in step timing (landing early) compared 

to the pre-programmed gait profile. Offsets in the recording 

angle can cause inaccuracies in the measurements since 

the footage was recorded in 2D. For future work, 

biomechanical data should be collected on people with HD 

or HP amputations, using 3D motion capture systems to 

accurately measure gait data.  

Another key finding from the functional test results is that 

the user tends to spend more time on their intact leg 

compared to the prosthesis. This causes asymmetrical gait 

patterns and is likely the result of the user feeling less stable 

on the prosthetic side. To be more specific, when the 

participant is supported with the prosthesis, they will quickly 

swing their intact leg in front for support. Feelings of 

discomfort and instability may be reduced with more training 

and experience with the prosthesis, along with a fully 

developed intelligent control system. 

The PHP tested in the current study weighs 3.9 kg, meeting 

the design criteria. Ueyama et al.,12 who prototyped a 

device using direct current (DC) motors, also noted that 

developing a lightweight powered hip joint prosthesis is 

challenging. They reported that the socket weighed 1.5 kg, 

resulting in a total robotic HDP weight of 11.3 kg. They did 

not provide the joint's weight separately. As well, electronics 

and battery were located at the waist, not integrated into the 

prosthesis.  Similarly, Mroz et al.,13 who evaluated a PHP 

mounted laterally, mentioned weight as a challenge, with 

their prototype weighing 5.7 kg. Further work is needed to 

decrease the PHP's size and weight.  

Limitations 

There are some limitations in this study. Since the control 

system was not fully developed during the primary 

functional testing, a simple control system was implemented 

that could only be used for level walking at a fixed speed. 

Additionally, the study was conducted with only three able-

bodied individuals. Evaluation with HD or HP is required in 

future evaluation.  

Table 4: Design criteria and results. 

 Requirement Actual value 
Met the design 

criteria 

Device weight  Maximum 4.0 kg  Measured 3.9 kg  Yes 

User weight  Maximum 100 kg  
Tested with 98 kg user  
Passed strength tests for 100 kg user  

Yes 

Strength  

Withstand 2240 N load for 30 s without failure or 
deformation > 15 mm  
Withstand 3360 N load without ductile failure  
Withstand 2×106 cycles between 50 N and 1330 
N without failure  

Passed static loading tests  
FEA simulations indicated that device should 
pass cyclical loading test  

Yes 

Range of motion 
Minimum 20° hip extension  22° hip extension (measured with protractor)  Yes 

Minimum 130° hip flexion  145° hip flexion (measured with protractor)  Yes 

Hip moment  Minimum 96 Nm  1:1 gear ratio should provide 96 Nm hip moment  Yes* 

Angular velocity  Minimum 150 °/s  
1:1 gear ratio should provide 300°/s angular 
velocity   

Yes* 

Anterior protrusion  Maximum 20 mm from top of lamination plate  
56 mm (measured with ruler) without the cover-
59 mm with the cover  

No 

Lateral protrusion  
Maximum 7.99 cm from centre of lamination 
plate  

7.2 cm (measured with ruler)  Yes 

Medial protrusion  
Maximum 4.99 cm from centre of lamination 
plate  

4.7 cm (measured with ruler)  Yes 

Device length  Maximum 378 mm   347 mm (measured with ruler)  Yes 

User safety  No uncovered finger traps  
Cover prevents most finger traps  
Cover does not fit over steel cables  

No 
 

* The Össur Power Knee™ microprocessor-controlled motor was used in this prototype, which provides 96 Nm of hip torque and an angular velocity of 300°/s. 

https://doi.org/10.33137/cpoj.v7i2.44494


 

10 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

During the initial testing, steel cabling was selected due to 

ease of crimping on terminators. However, steel cables are 

not ideal for a final product because their rated capacity is 

1779 N, which falls below the design criterion tensile 

strength of 4465 N, posing a risk of failure under increased 

loads.  

CONCLUSION 

The novel microprocessor-controlled PHP demonstrated 

successful performance in both mechanical strength and 

functional testing. The pulley and cable transmission 

system effectively transmitted power from the actuator to 

the hip joint, meeting the functional design requirements 

while maintaining a compact and lightweight profile, 

showing strong potential for real-world applications. While 

the PHP achieved most of its principal design objectives, 

some areas like part optimization, control system design, 

and cable strength and slack management require further 

refinement. Future iterations could focus on implementing 

an intelligent adaptive control system, optimizing 

mechanical parts and mechanisms, and continuing 

functional testing with people with HD or HP amputations.  

At this stage of development, a reasonable balance 

between comfort and safety has been achieved and will be 

further refined as development progresses. Continued 

research and development will aim to address the 

remaining challenges, prioritizing gait stability and 

symmetry, pushing the technology closer to real-world 

deployment. 

ACKNOWLEDGEMENTS 

The authors would like to thank Farshad Golshan, and Hossein 

Gholizadeh for their work on the powered hip design and control 

system development, Yousef Bader for his help with the assembly, 

and the Ottawa Hospital Rehabilitation Centre and the University of 

Ottawa for providing resources for development and testing. They 

would also like to thank Össur staff for their assistance with 

documentation of the knee joint and electronics. 

DECLARATION OF CONFLICTING INTERESTS 

David Langlois is an employee of Össur. No other conflicts of 

interest. 
 

AUTHORS CONTRIBUTION 

• Kelly Brannen: Conceptualization; Joint design; Data 

collection and analysis; Manuscript revision. 

• Natalie Baddour: Conceptualization; Data analysis; 

Manuscript revision, Supervision. 

• Lucas Cho: Prepared the initial manuscript; Manuscript 

revision. 

• David Langlois: Conceptualization; Design. 

• Patrick Dumond: Design. 

• Edward Lemaire: Conceptualization; Data analysis; 

Manuscript revision; Supervision. 

 

SOURCES OF SUPPORT 

This study was financially supported by Össur and Mitacs. 

REFERENCES 

1.Kaufman KR, Levine JA, Brey RH, Iverson BK, McCrady SK, 

Padgett DJ, et al. Gait and balance of transfemoral amputees using 

passive mechanical and microprocessor-controlled prosthetic 

knees. Gait Posture. 2007;26(4):489-93, DOI: 

10.1016/j.gaitpost.2007.07.011 

2.Kaufman KR, Levine JA, Brey RH, McCrady SK, Padgett DJ, 

Joyner MJ. Energy expenditure and activity of transfemoral 

amputees using mechanical and microprocessor-controlled 

prosthetic knees. Arch Phys Med Rehabil. 2008;89(7):1380-1385. 

DOI: 10.1016/j.apmr.2007.11.053 

3.Waters RL, Perry J, Antonelli DA, Hislop H. Energy cost of 

walking of amputees: The influence of level of amputation. J. Bone 

Joint Surg Am. 1976;58(1):42-6 

4.Ludwigs E, Bellmann M, Schmalz T, Blumentritt S. Biomechanical 

differences between two exoprosthetic hip joint systems during 

level walking. Prosthet Orthot Int. 2010;34(4):449-60. DOI: 

10.3109/03093646.2010.499551 

5.Grimmer M, Seyfarth A. Mimicking human-like leg function in 

prosthetic limbs. Neuro-robotics: From brain machine interfaces to 

rehabilitation robotics. 2014:105-55. DOI: 10.1007/978-94-017-

8932-5_5 

6.Chin T, Sawamura S, Shiba R, Oyabu H, Nagakura Y, Nakagawa 

A. Energy expenditure during walking in amputees after 

disarticulation of the hip: A microprocessor-controlled swing-phase 

control knee versus a mechanical-controlled stance-phase control 

knee. J. Bone Joint Surg Br. 2005;87(1):117-9 

7.Karimi MT, Kamali M, Omar H, Mostmand J. Evaluation of gait 

performance of a hemipelvectomy amputation walking with a 

canadian prosthesis. Case Rep Orthop. 2014;962980. DOI: 

10.1155/2014/962980 

8.Gailey R, Allen K, Castles J, Kucharik J, Roeder M. Review of 

secondary physical conditions associated with lower-limb 

amputation and long-term prosthesis use. J Rehabil Res Dev. 

2008;45(1),15–29. DOI: 10.1682/jrrd.2006.11.0147 

9.Fluit R, Prinsen EC, Wang S, Van Der Kooij H. A comparison of 

control strategies in commercial and research knee prostheses. 

IEEE Trans Biomed Eng. 2019;67(1):277-90. DOI: 

10.1109/TBME.2019.2912466 

10.Dall PM, Kerr A. Frequency of the sit to stand task: An 

observational study of free-living adults. Appl Ergon. 

2010;41(1):58-61. DOI: 10.1016/j.apergo.2009.04.005 

11.Ludwigs E, Bellmann M, Schmalz T, Blumentritt S. 

Biomechanical differences between two exoprosthetic hip joint 

systems during level walking. Prosthet Orthot Int. 2010;34(4):449-

60. DOI: 10.3109/03093646.2010.499551 

12.Ueyama Y, Kubo T, Shibata M. Robotic hip-disarticulation 

prosthesis: Evaluation of prosthetic gaits in a non-amputee 

individual. Adv Robot. 2020;34(1):37-44. DOI: 

10.1080/01691864.2019.1705908 

https://doi.org/10.33137/cpoj.v7i2.44494


 

11 

Brannen K, Baddour N, Cho L, Langlois D, Dumond P, Lemaire E.D. Development and evaluation of an anteriorly mounted microprocessor-controlled powered hip 
joint prosthesis. Canadian Prosthetics & Orthotics Journal. 2024; Volume 7, Issue 2, No. 7. https://doi.org/10.33137/cpoj.v7i2.44494 

CANADIAN PROSTHETICS & ORTHOTICS JOURNAL 

ISSN: 2561-987X MICROPROCESSOR-CONTROLLED POWERED HIP JOINT PROSTHESIS 

Brannen et al., 2024 

13.Mroz S, Baddour N, Dumond P, Lemaire ED. Design and 

prototype validation of a laterally mounted powered hip joint 

prothesis. J Rehabil Assist Technol Eng. 2024;11. DOI: 

10.1177/20556683241248584 

14.Bader Y, Langlois D, Baddour N, Lemaire ED. Development of 

an Integrated Powered Hip and Microprocessor-Controlled Knee 

for a Hip–Knee–Ankle–Foot Prosthesis. Bioeng. 2023;10(5):614. 

DOI: 10.3390/bioengineering10050614 

15.Bona RL, Gomeñuka NA, Storniolo JL, Bonezi A, Biancardi CM. 

Self-selected walking speed in individuals with transfemoral 

amputation: Recovery, economy and rehabilitation index. Eur J 

Physiother. 2020;22(3):133-40. DOI: 10.1080/21679169.2018. 

1561941 

16.Darter BJ, Nielsen DH, Yack HJ, Janz KF. Home-based 

treadmill training to improve gait performance in persons with a 

chronic transfemoral amputation. Arch Phys Med Rehabil. 

2013;94(12):2440-7. DOI: 10.1016/j.apmr.2013.08.001 

17.Schmalz T, Blumentritt S, Marx B. Biomechanical analysis of 

stair ambulation in lower limb amputees. Gait Posture. 

2007;25(2):267-78. DOI: 10.1016/j.gaitpost.2006.04.008 

18.Segal AD, Orendurff MS, Klute GK, McDowell ML, Pecoraro JA, 

Shofer J, et al. Kinematic and kinetic comparisons of transfemoral 

amputee gait using C-Leg and Mauch SNS prosthetic knees. J 

Rehabil Res Dev. 2006;43(7). DOI: 10.1682/jrrd.2005.09.0147 

19.Össur. Power Knee PKA01: Instructions for Use [Internet]. [cited 

2024 Dec 10]. Available from: 

https://ossur.com.ua/Media/ossur/Instructions/Brochures/knee/PO

WER%20KNEE%20Instructions%20for%20use.pdf 

20.ISO 15032:2000. Prostheses – Structural testing of hip joints 

[Internet]. 2000 [cited 2024 Dec 10]. Available from: 

https://webstore.ansi.org/standards/bsi/bsiso150322000 

21.Gordon CC. 1988 Anthropometric survey of US army personnel: 

methods and summary statistics. Technical Report Natick/TR-

89/044. 1989. 

http://mreed.umtri.umich.edu/mreed/downloads/anthro/ansur/Gord

on_1989.pdf 

22.Brannen K. Design and evaluation of a microprocessor-

controlled powered hip prosthesis [master's thesis]. Ottawa (ON): 

University of Ottawa; 2023 

23.Fanous A, Botros M, Gholizadeh H, Baddour N, Lemaire ED. 

Design and evaluation of a hip prosthesis simulator: A technical 

note. Prosthet Orthot Int. 2023;4,443–446. DOI: 10.1097/PXR. 

0000000000000208 

 

 

 

 

 

 

 

 

 

 

 

 

 

https://doi.org/10.33137/cpoj.v7i2.44494
https://ossur.com.ua/Media/ossur/Instructions/Brochures/knee/POWER%20KNEE%20Instructions%20for%20use.pdf
https://ossur.com.ua/Media/ossur/Instructions/Brochures/knee/POWER%20KNEE%20Instructions%20for%20use.pdf
https://webstore.ansi.org/standards/bsi/bsiso150322000
http://mreed.umtri.umich.edu/mreed/downloads/anthro/ansur/Gordon_1989.pdf
http://mreed.umtri.umich.edu/mreed/downloads/anthro/ansur/Gordon_1989.pdf

