Validation of the Narrowing Beam Walking Test in Lower Limb Prosthesis Users

Area of Science:

• Biomechanics and Rehabilitation Engineering
• Prosthetics and Orthotics
• Clinical Assessment Tools

Background:

• Balance assessment is crucial for lower limb prosthesis users to predict fall risk and guide rehabilitation.
• Existing balance tests may have limitations in sensitivity or specificity for this population.
• The Narrowing Beam Walking Test (NBWT) was developed as a novel performance-based measure.

Purpose of the Study:

• To evaluate the content, construct, and discriminant validity of the NBWT.
• To determine if the NBWT can reliably differentiate balance abilities in prosthesis users.
• To establish the NBWT's utility in assessing balance impairments and fall risk.

Main Methods:

• A cross-sectional study involving 40 unilateral transtibial and transfemoral prosthesis users.
• Content validity assessed via ceiling and floor effects.
• Construct validity examined through correlations with established balance tests (TUG, FSST, BBS, ABC-S).
• Discriminant validity evaluated using receiver operating characteristic (ROC) curve analysis based on fall history, amputation level, and functional mobility.

Main Results:

• No ceiling or floor effects were observed for the NBWT.
• NBWT scores showed strong correlations with performance-based balance tests (ρ=.70–.85) and moderate correlation with the ABC-S (ρ=.49).
• Significantly lower NBWT scores were found in participants with a history of falls, transfemoral amputations, and lower mobility levels.
• The NBWT demonstrated the largest area under the ROC curve (.81), indicating superior discriminant ability.

Conclusions:

• The NBWT exhibits strong content, construct, and discriminant validity.
• The test is a reliable performance-based measure for assessing balance in lower limb prosthesis users.
• Evidence supports the NBWT's use for evaluating balance deficits and fall risk in this population.