Transtibial prosthetic alignment has small effects on whole-body angular momentum during functional tasks

Area of Science:

• Biomechanics
• Prosthetics
• Rehabilitation

Background:

• Transtibial amputation (TTA) often leads to impaired ankle function, causing balance difficulties.
• Prosthetic alignment significantly influences ground reaction forces (GRFs) and centers of pressure, impacting balance in individuals with TTA.

Purpose of the Study:

• To quantify the effect of prosthetic alignment variations on dynamic balance during functional tasks in individuals with TTA.
• To compare balance control strategies between individuals with TTA and able-bodied controls.

Main Methods:

• Ten individuals with TTA and ten controls performed walking, sit-to-stand, and stand-to-sit tasks.
• Participants with TTA used their prescribed prosthesis alignment and six altered alignments (±10mm anterior/posterior, medial/lateral; ±20mm vertical).
• Dynamic balance was assessed using whole-body angular momentum (H→WB), trunk range of motion (ROM), and peak GRFs.

Main Results:

• Individuals with TTA exhibited greater H→WB range in the sagittal plane during walking and in all planes during sit-to-stand compared to controls.
• Transverse plane H→WB was greater for TTA during stand-to-sit, linked to GRF and trunk ROM differences.
• Prosthetic alignment primarily affected frontal plane H→WB during walking, with vertical shifts correlating with inter-limb GRF differences.

Conclusions:

• Individuals with TTA demonstrate adaptability to small, translational prosthetic alignment changes for maintaining dynamic balance during chair transitions.
• Further research is needed to explore alignment effects on balance in other functional tasks and in individuals with lower mobility.
• Prosthetic alignment is a critical factor influencing dynamic balance and inter-limb loading in individuals with TTA.