Core Muscle Function and Postural Control in Lower Extremity Amputees

This study aims to investigate the effects of lower extremity amputation on core muscles and their relationship with postural control. The primary objective is to compare core muscle thickness in individuals with lower extremity amputation with both their intact side and a healthy control group using ultrasonographic assessment. The secondary objective is to examine the relationship between core muscle thickness and postural stability during different functional activities, and to determine the role of core muscles in postural control.

It is hypothesized that there are differences in core muscle thickness between the amputated and intact sides, as well as between amputees and healthy individuals. Additionally, core muscle function is expected to be associated with postural sway, limits of stability, functional tasks (such as sit-to-stand and stair negotiation), prosthesis adaptation, fear of falling, and the percentage of limb loss.

The study sample will consist of transtibial and transfemoral amputees who attend routine follow-up visits, along with a matched healthy control group. Ultrasonography will be used to objectively assess core muscle thickness, allowing the identification of muscle atrophy and asymmetrical loading. Postural control will be evaluated using a computerized balance system during various activities.

Statistical analyses will include descriptive statistics, normality tests, group comparisons, and correlation analyses. The findings are expected to contribute to the development of targeted rehabilitation programs focusing on core muscles to improve postural stability and reduce fall risk in individuals with lower extremity amputation.

Primary outcomes

• Diaphragm Thickening Fraction [Day 1]: Diaphragm thickness will be assessed bilaterally at the zone of apposition using B-mode ultrasonography at the end of quiet expiration and during deep inspiration. Diaphragm thickening fraction will be calculated as \[(thickness during deep inspiration - thickness at the end of quiet expiration) / thickness at the end of quiet expiration\] × 100 and reported as a percentage (%). Three high-quality measurements will be obtained for each side, and the mean value will be used for analysis. Bilateral measurements will be used for side and group comparisons.
• Transversus Abdominis Activation Ratio [Day 1]: Transversus abdominis muscle thickness will be assessed bilaterally using B-mode ultrasonography at the end of quiet expiration at rest and during the abdominal drawing-in maneuver. The activation ratio will be calculated by dividing muscle thickness during the abdominal drawing-in maneuver by muscle thickness at rest. Three high-quality measurements will be obtained for each side, and the mean value will be used for analysis. The activation ratio is dimensionless. Bilateral measurements will be used for side and group comparisons.
• Internal Oblique Activation Ratio [Day 1]: Internal oblique muscle thickness will be assessed bilaterally using B-mode ultrasonography at the end of quiet expiration at rest and during the abdominal drawing-in maneuver. The activation ratio will be calculated by dividing muscle thickness during the abdominal drawing-in maneuver by muscle thickness at rest. Three high-quality measurements will be obtained for each side, and the mean value will be used for analysis. The activation ratio is dimensionless. Bilateral measurements will be used for side and group comparisons.

Secondary outcomes

• Standing Postural Sway [Day 1]: Standing postural sway will be assessed using the Modified Clinical Test of Sensory Interaction on Balance (mCTSIB) with the NeuroCom Balance Master. Center-of-gravity sway velocity will be measured during standing under four sensory conditions: eyes open on a firm surface, eyes closed on a firm surface, eyes open on a foam surface, and eyes closed on a foam surface. Sway velocity will be expressed in degrees per second (°/s), with lower values indicating better postural stability.
• Percentage of Remaining Limb [Day 1]: The remaining limb length will be measured using a tape measure. The percentage of remaining limb will be calculated by dividing the remaining limb length by the total lower-extremity length and multiplying by 100. The result will be expressed as a percentage (%).
• Prosthesis Awareness [Day 1]: Prosthesis awareness will be assessed using the amputee-adapted Forgotten Joint Score-12 (FJS-12). The questionnaire consists of 12 items evaluating awareness of the prosthesis during activities of daily living. Higher scores indicate a greater ability to forget the prosthesis during daily activities.
• Fear of Falling [Day 1]: Fear of falling will be assessed using the Falls Efficacy Scale-International (FES-I). The scale consists of 16 items scored from 1 to 4, with a total score ranging from 16 to 64. Higher scores indicate greater concern about falling.
• Reaction Time During Limits of Stability Test [Day 1]: Reaction Time During Limits of Stability Test Reaction time will be assessed using the Limits of Stability test of the NeuroCom Balance Master. It represents the time between the visual cue and the initiation of voluntary movement toward the target and will be reported in seconds (s).
• Movement Velocity During Limits of Stability Test [Day 1]: Movement velocity will be assessed using the Limits of Stability test of the NeuroCom Balance Master. It represents the average speed of center-of-gravity movement toward the target and will be reported in degrees per second (°/s).
• Endpoint Excursion During Limits of Stability Test [Day 1]: Endpoint excursion will be assessed using the Limits of Stability test of the NeuroCom Balance Master. It represents the distance reached by the center of gravity during the initial movement toward the target and will be reported as a percentage (%).
• Maximum Excursion During Limits of Stability Test [Day 1]: Maximum excursion will be assessed using the Limits of Stability test of the NeuroCom Balance Master. It represents the maximum distance reached by the center of gravity toward the target and will be reported as a percentage (%).
• Directional Control During Limits of Stability Test [Day 1]: Directional control will be assessed using the Limits of Stability test of the NeuroCom Balance Master. It reflects the accuracy of center-of-gravity movement toward the intended target relative to extraneous movement and will be reported as a percentage (%).
• Weight Transfer Time During Sit-to-Stand [Day 1]: Weight transfer time will be assessed using the Sit-to-Stand test of the NeuroCom Balance Master. It represents the time from the initiation of the test until the center of gravity is transferred over the feet and will be reported in seconds (s).
• Rising Index During Sit-to-Stand [Day 1]: The rising index will be assessed using the Sit-to-Stand test on the NeuroCom Balance Master. It represents the force exerted by the lower extremities on the force platform during rising, normalized to body weight, and will be reported as a percentage (%).
• Postural Sway Velocity After Sit-to-Stand [Day 1]: Postural sway velocity will be assessed using the Sit-to-Stand test on the NeuroCom Balance Master. It represents the center-of-gravity sway velocity during the first five seconds after rising to a standing position and will be reported in degrees per second (°/s).
• Weight-Bearing Asymmetry During Sit-to-Stand [day 1]: Weight-bearing asymmetry will be assessed using the Sit-to-Stand test on the NeuroCom Balance Master. It quantifies the asymmetry in load distribution between the right and left lower extremities during the sit-to-stand task and in the first five seconds of standing, and will be reported as a percentage (%).
• Lift-Up Index During the Step Up/Over Task [Day 1]: The lift-up index will be assessed using the Step Up/Over test on the NeuroCom Balance Master. It represents the force exerted by the stepping limb to raise the body onto the step, normalized to body weight, and will be reported as a percentage (%).
• Movement Time During the Step Up/Over Task [day 1]: Movement time will be assessed using the Step Up/Over test on the NeuroCom Balance Master. It represents the time required to complete the stepping movement and will be reported in seconds (s).
• Impact Index During the Step Up/Over Task [Day 1]: The impact index will be assessed using the Step Up/Over test on the NeuroCom Balance Master. It represents the force exerted on the force platform during landing, normalized to body weight, and will be reported as a percentage (%).

Sex: All, ages: 20 Years to 60 Years, accepts healthy volunteers

For the Amputee Group

Inclusion Criteria:

* Being between 20-60 years of age
* Having a unilateral transtibial or transfemoral amputation
* Being at K1-K3 functional activity level
* Being able to stand without the use of assistive devices
* Using a prosthesis for at least 4 hours per day
* Volunteering to participate in the study

Exclusion Criteria:

* Having phantom or residual limb pain ≥6 according to the Numeric Rating Scale
* Having bilateral lower extremity amputation
* Having a Body Mass Index greater than 30

For the Healthy Control Group

Inclusion Criteria:

* Healthy individuals with demographic characteristics similar to the amputee group
* Not having a regular exercise habit

Exclusion Criteria:

* Having central or peripheral vestibular disorders
* Having lower extremity joint contractures
* Using medications that affect balance
* Having a Body Mass Index greater than 30