A Biomechanical Evaluation of the Ossur Power Knee in Persons With Transfemoral Amputation

NCT ID: NCT06218238

Last Updated: 2025-09-09

Basic Information

• Recruitment Status: RECRUITING
• Clinical Phase: NA
• Total Enrollment: 20 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2024-04-01
• Study Completion Date: 2027-03-31

Brief Summary

Microprocessor-controlled knees (MPKs) do not typically utilize motors to power joint rotation, but they automatically adjust resistance or damping in the joint to improve swing- and/or stance-phase control as appropriate for the prosthesis user during gait. The Ossur Power Knee is the only commercially-available MPK that uses a motor to provide active power generation during walking and other activities. The purpose of this proposed investigation is to perform and compare biomechanical evaluations of the Power Knee and Ossur Rheo XC, a passive MPK, during walking and other activities by prosthesis users. Furthermore, mobility between male and female subjects will be compared to determine if there are differences in prosthetic knee usage on the basis of sex.

Detailed Description

The anatomical knee is a complex, polycentric joint characterized by a large range of motion in the sagittal plane and limited mobility in the coronal and transverse planes. The sagittal plane motion is used for progression in stance phase, and limb clearance and advancement in swing. Limb prostheses are intended to restore function and cosmesis in persons with limb loss. The complexity and function of prosthetic components have advanced significantly as technology has improved, but a state-of-the-art artificial limb is still a relatively poor substitute for an anatomical one. Microprocessor-controlled knees (MPKs) do not typically utilize motors to power joint rotation, but they automatically adjust resistance or damping in the joint to improve swing- and/or stance-phase control as appropriate for the user during gait. The Ossur Power Knee, which was first introduced in 2006, is the only MPK that uses a motor to provide active power generation during walking and other activities involving knee flexion and extension. Last year, Ossur released the 3rd generation of its Power Knee and appears to have addressed many of the previous shortcomings in terms of reduced weight, less noise, lower cost and longer battery life. Therefore, the newest version of the Power Knee warrants a fresh evaluation since it is, in essence, substantially different in design and function from previous models.

The purpose of this proposed investigation is to perform biomechanical evaluations of the new Ossur Power Knee during walking and other activities by transfemoral prosthesis users. Using a cross-over experimental design, approximately 20 unilateral, transfemoral amputee subjects (10 men and 10 women) will be evaluated in the Jesse Brown VAMC Motion Analysis Research Laboratory (MARL) while wearing the Ossur Power Knee and Ossur Rheo XC, which is a passive MPK device. Furthermore, the Ossur Power Knee may offer distinct advantages to female prosthesis users, so mobility will be compared between men and women to determine if differences exist on the basis of sex. The specific aims and hypotheses of this project are:

Aim 1: To compare the effects of the Ossur Power Knee and Ossur Rheo XC on the gait of unilateral, transfemoral prosthesis users during level walking. Kinematic and kinetic data will be collected as subjects walk in the MARL. Hypothesis--the active knee flexion and extension provided by the Ossur Power Knee will (1) improve walking performance, and (2) reduce metabolic energy cost during ambulation.

Aim 2: To compare the effects of the Ossur Power Knee and Ossur Rheo XC on stairs, slopes and during sit-to-stand/stand-to-sit activities of unilateral, transfemoral prosthesis users. Kinematic data will be collected as subjects perform these activities. Hypothesis--subjects will have improved performance when using the Ossur Power Knee.

Aim 3: To analyze and compare gender specific data between subjects using the Ossur Power Knee and the Ossur Rheo XC. Hypothesis--male and female subjects will demonstrate substantially different abilities to use the two knee components, indicating that gender specific components should be further investigated and developed. Research focusing on the unique prosthetic needs of women Veterans is currently a special emphasis area of the VA RR&D Service.

Subjects will also be administered questionnaires and provided at-home diaries to document their perceptions of comfort, exertion and stability while using the different prosthetic knee units.

The repeated-measures, cross-over protocol design enables each subject to serve as their own control, and it will be determined whether statistically significant changes occur in their performance measures. A two-way mixed-methods ANOVA will be used to assess the main and interaction effects of sex (male, female) and knee type (Ossur Power Knee, Rheo XC). As a conservative approach, a Bonferroni correction will be used to account for the family-wise Type I error rate because multiple outcomes will be used to address each hypothesis.

Increased understanding about how the Ossur Power Knee affects the abilities of transfemoral prosthesis users will facilitate appropriate component selection by prosthetists and ultimately improve quality of life for prosthesis users.

Conditions

Transfemoral Amputation; Limb Loss; Limb Absence

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: TREATMENT
• Blinding Strategy: NONE

Study Groups

Ossur Power Knee

Subjects will be fitted with the Ossur Power Knee, which has powered flexion and extension.

Group Type: EXPERIMENTAL

Powered prosthetic knee joint

Intervention Type: OTHER

Subjects will be fitted and trained on the Ossur Power Knee. An accommodation of 1 month will be provided prior to evaluation with the knee joint.

Ossur Rheo XC Knee

Subjects will be fitted with the Ossur Rheo XC Knee, which is a conventional microprocessor-controlled knee joint that modulates the amount of damping during flexion and extension.

Group Type: ACTIVE_COMPARATOR

Conventional prosthetic knee joint

Intervention Type: OTHER

Subjects will be fitted and trained on the Ossur Rheo XC Knee. An accommodation of 1 month will be provided prior to evaluation with the knee joint.

Interventions

Powered prosthetic knee joint

Subjects will be fitted and trained on the Ossur Power Knee. An accommodation of 1 month will be provided prior to evaluation with the knee joint.

Intervention Type: OTHER

Conventional prosthetic knee joint

Subjects will be fitted and trained on the Ossur Rheo XC Knee. An accommodation of 1 month will be provided prior to evaluation with the knee joint.

Intervention Type: OTHER

Eligibility Criteria

Inclusion Criteria

• Unilateral, transfemoral amputation (any etiology).
• Age from 45-75 years.
• Residual limb length classified as standard (i.e., medium) to long.
• Prosthesis user for at least 1 year prior to enrolling in the study.
• K3 or K4 level ambulator.
• Good sensation on their residual limb(s) (upon routine clinical examination).
• Good skin integrity upon visual inspection.
• Does not require the use of assistive devices to walk for short distances.
• Not currently taking medications that are known to affect balance or gait.
• Presents with good socket fit based upon a standard assessment by the study prosthetist.

Exclusion Criteria

• Bilateral amputations
• Individuals with a knee disarticulation

• Minimum Eligible Age: 45 Years
• Maximum Eligible Age: 75 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

VA Office of Research and Development

FED

Sponsor Role: lead

Responsible Party

Responsibility Role: SPONSOR

Principal Investigators

Steven A Gard, PhD

Role: PRINCIPAL_INVESTIGATOR

Jesse Brown VA Medical Center, Chicago, IL

Locations

Jesse Brown VA Medical Center, Chicago, IL

Chicago, Illinois, United States

Site Status: RECRUITING

Countries

United States

Central Contacts

Rebecca Stine, MS

Role: CONTACT

rebecca.stine@va.gov

(312) 503-5726

Steven A Gard, PhD

Role: CONTACT

steven.gard@va.gov

Facility Contacts

Rebecca Stine, MS

Role: primary

rebecca.stine@va.gov

312-503-5726

Steven A Gard, PhD

Role: backup

steven.gard@va.gov

Other Identifiers

RX004541-01A2

Identifier Type: OTHER_GRANT

Identifier Source: secondary_id

A4541-R

Identifier Type: -

Identifier Source: org_study_id