Assessment of Strength, Balance, and Function in Above-Knee Amputees in Relation to Residual Limb Length

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.

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:

• Hip Flexion/Extension: 5 reps at 60°/s, 10 reps at 120°/s (supine position)
• Knee Flexion/Extension: 5 reps at 60°/s, 10 reps at 180°/s (seated, hip at 90°)
• 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.

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:

• Static balance with eyes open and eyes closed (coefficient of stability)
• Single-Leg Stability on the intact limb (coefficient of stability)
• Limits of stability quantified as sway in mm

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.

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.