The goal of this observational study is to learn how muscle strength, balance, and functional ability are affected in people with above-knee (transfemoral) amputations. The main questions it aims to answer are: How does the length of the lost part of the leg, compared to the intact leg, affect muscle strength, balance, and functional capacity? Is muscle strength at specific lower limb joints related to balance and performance ? Participants will: Have muscle strength measured at all intact lower limb joints using an isokinetic dynamometer Complete balance assessments using force platform technology that measures weight distribution and evaluates both static and dynamic balance Perform a six-minute walk test to evaluate endurance and functional capacity The study will help improve understanding of how limb length and joint-specific muscle strength impact mobility, supporting the development of better rehabilitation programs for amputees.
This study is a cross-sectional observational study designed to assess lower extremity muscle strength, balance, and functional capacity in individuals with unilateral transfemoral amputation. The primary aim is to examine how the length of the lost part of the limb, in relation to the intact limb, correlates with these physical performance parameters. This study does not involve any intervention or follow-up over time. All data will be collected at one time point. Therefore, although the registry requires a study model selection, the study design does not align with standard cohort or case-control models. For this reason, the "Other" option was selected as the most appropriate observational study model.
Study Type
OBSERVATIONAL
Enrollment
15
Length of Residual Limb and Intact Limb (cm) and Percentage of Limb Loss (%)
Anthropometric measurements will be performed using a standard measuring tape. For the amputated limb, the distance will be measured from the greater trochanter to the distal end of the residual limb along the lateral midline. For the intact limb, the measurement will extend from the greater trochanter to the plantar surface of the foot. The difference between these two measurements will represent the length of the lost limb. The percentage of limb loss will then be calculated by comparing the lost length to the total length of the intact limb.
Time frame: 1 day
Isokinetic Strength Testing
Isokinetic muscle strength assessments will be conducted using the IsoMed 2000 Dynamometer (D\&R Ferstl GmbH, Hemau, Germany). Measurements will include peak torque (Nm) and total work (J) values for hip, knee, and ankle flexor/extensor muscles. Testing will be performed under the following angular velocities and repetitions: 1. Hip Flexion/Extension: 5 reps at 60°/s, 10 reps at 120°/s (supine position) 2. Knee Flexion/Extension: 5 reps at 60°/s, 10 reps at 180°/s (seated, hip at 90°) 3. Ankle Plantar/Dorsiflexion: 5 reps at 60°/s, 10 reps at 120°/s (seated, semi-flexed hip, 90° knee flexion) Rest periods will be given between measurements to minimize fatigue. Tests will be randomized across different joints and days to avoid order effects. Data will be summarized as peak torque and total work values for each muscle group at the specified angular velocities.
Time frame: 5 days
Stability Coefficient (Eyes Open and Closed), Single-Leg Stability of Intact Side, and Limits of Stability (mm)
Participants' balance abilities will be assessed using the Huber 360® Evolution (LPG Systems, Valence, France), a motorized multi-axial platform with integrated force sensors. The following parameters will be measured and reported: 1. Static balance with eyes open and eyes closed (coefficient of stability) 2. Single-Leg Stability on the intact limb (coefficient of stability) 3. Limits of stability quantified as sway in mm
Time frame: 1 day
6 minute walk test
Time frame: 1 day
The Amputee Mobility Predictor (AMP)
Mobility level will be assessed using the Amputee Mobility Predictor (AMP) scale. This performance-based tool includes 21 items covering balance while sitting, transfers, standing balance, walking, stair climbing, and assistive device use. Scores range from 0 to 47, with higher scores indicating better mobility. Based on the scores, participants will be classified according to the Medicare Functional Classification Levels (K-levels), which are defined by the United States Centers for Medicare \& Medicaid Services (CMS) to standardize functional mobility and prosthetic eligibility.
Time frame: 1 day
The Comprehensive Lower-limb Amputee Socket Survey (CLASS)
Socket fit and comfort will be evaluated using The Comprehensive Lower-limb Amputee Socket Survey (CLASS), a validated self-report questionnaire developed by Gailey et al. The survey includes 15 items assessing four domains: stability, suspension, comfort, and appearance of the prosthetic socket. Each item is rated on a 4-point ordinal scale, and total scores are converted into a percentage score ranging from 0% to 100%, with higher percentages indicating better socket fit and greater user satisfaction.
Time frame: 1 day
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