Amputee Mobility Predictor

Original Editor - Mariam Hashem

Top Contributors - Mariam Hashem, Sheik Abdul Khadir and Sweta Christian

Objective

Amputee mobility predictor (AMP) is a quick and easily administered assessment tool designed to measure the functional status of lower-limb amputees with (AMPPRO) and without (AMPnoPRO) the use of a prosthesis.

The test was also designed to be clinically feasible in that it takes less than 10 to 15 minutes to administer and requires very little equipment.

AMP can be used before prosthetic fitting to predict functional mobility after prosthetic fitting. Although the AMP can be administered both with (AMPPRO) and without (AMPnoPRO) a prosthesis, the AMPnoPRO has the greatest potential to assist in prosthetic prescription.

The AMP was also designed to assess the specific tasks identified in the 5-level Medicare functional classification system (MFCL). MFCL was developed in 1995 by the US Health Care Financing Administration (HCFA) to describe the functional abilities of persons who had undergone lower-limb amputation. (K0, K1, K2, K3, K4)[1]

K-Level 0 Does not have the ability or potential to ambulate or transfer safely with or without assistance, and a prosthesis does not enhance quality of life or mobility.
K-Level 1


Has the ability or potential to use a prosthesis for transfers or ambulation in level surfaces at a fixed cadence. Typical of the limited and unlimited household ambulator
K-Level 2 Has the ability or potential for ambulation with the ability to transverse low-level environmental barriers such as curbs, stairs, or uneven surfaces. Typical of the limited community ambulator.
K-Level 3 Has the ability or potential for ambulation with variable cadence. Typical of the community ambulator who has the ability to transverse most environmental barriers and may have vocational, therapeutic, or exercise activity that demands prosthetic use beyond simple locomotion.
K-Level 4 Has the ability or potential for prosthetic ambulation that exceeds basic ambulation skills, exhibiting high impact, stress, or energy levels. Typical of the prosthetic demands of the child, active adult, or athlete.

Intended Population

Unilateral or Bilateral Lower limb amputees. However, bilateral amputee subjects with amputation levels higher than trans-tarsal foot amputations may be tested only with the AMPPRO because it is not physically possible for them to perform the AMPnoPRO.[1]

Methods of Use

The total score range for the AMP is 0 to 42 points. In its AMPnoPRO configuration, the highest possible score is 38 points because item 8, single-limb standing, is eliminated (standing on the prosthetic side is impossible). By using an assistive device, the subjects’ potential total score possibilities increase by 5 points (to 43 and 47 points for the AMPnoPRO and AMPRO, respectively), depending on the type of assistive device used during testing.

Most AMP items offer 3 scoring choices: 0 indicates inability to perform the task, 1 implies minimal level of achievement or that some assistance was required in completing the task, and 2 denotes complete independence or mastery of the task

The items are organized with an increasing level of difficulty to allow for the progressive assessment of the amputee.

Items 1 and 2 test the ability to maintain sitting balance. The sitting reach test assesses the ability to displace one’s center of mass (COM) and to return to balanced sitting without falling. If the amputee subject does not have the ability to sit and reach in sitting independently, then the possibility for even limited prosthetic use is remote and the amputee subject therefore would be classed as a level K0.

Items 3 through 7 are designed to examine the amputee subject’s ability to maintain balance while performing the relatively simple task of transferring from chair to chair and standing unchallenged. These skills are necessary for a level 1 amputee subject who would receive a prosthesis for transfers and simple standing activities. The ability to perform these test items safely would probably suggest that the patient could manage a prosthesis in limited situations, especially in a supervised environment.

Items 8 through 13 are more challenging activities related to standing balance. Subject performs several tests including; single-limb balance, modified standing reach test, nudge test, and check reactive balance. In order to maintain balance during these tests subject requires adequate somatosensory and vestibular systems. Succeeding these tests means that the amputee subject has the potential to be a safe household ambulator; that is, he/she can function at level K2

AMP items 14 through 20 evaluate the quality of gait and the ability to negotiate specific obstacles. These qualities are defined as k3 ambulator or level 4 suggesting, the amputee subject can perform all skills with greater ease.

Item 21 accounts for the use of particular assistive devices.[1]



Validity

The concurrent validity of the AMP was tested against 2 known tests, the 6-minute walk, which is a rehabilitation standard, and the Amputee Activity Survey (AAS), which has been shown to be a valid subjective instrument for amputee subjects. The 6-minute walk distance showed a moderate to high positive relationship with both the AMPnoPRO and AMPPRO (r =.69, P<.0001; r=.82, P<.0001, respectively). The AAS had a high to moderate positive correlation to the AMPnoPRO and AMPPRO  (r=.67, P<.0001; r=.77,P<.0001, respectively).

Predictive validity of the AMP was also examined by first determining the relationship between the 6-minute walk distance and the AMPnoPRO test, age, time after amputation, and comorbidity. The overall model was statistically significant (P<.0001) indicating that together these variables do a fairly good job of explaining the variance in the 6-minute walk distance.[1]

Reliability

Gailey et al tested the intra and inter-rater reliability of the AMP with and without a prosthesis using Intra-class correlation coefficients (ICCs). The inter-rater score demonstrated excellent reliability (.99) for the AMPPRO and the AMPnoPRO. Test-retest intra-rater reliability also had excellent reliability, with rater 1 and rater 2 ICC scores of .96 and .98, respectively, for the AMPPRO. ICC scores for the AMPnoPRO were .97 and .86, respectively, for rater 1 and rater 2.[1]

Resources:

-Amputee mobility predictor

-Predictor, A. M., Index, L. C., Group, S. I., Medicine, A., Index, R. M., Index, T. B., … Classification, I. (2005). Lower Limb Prosthetic Outcome Measures : A Review of the Literature 1995 to 2005 Elizabeth Condie , Grad Dip Phys , FCSP , Helen Scott , Grad Dip Phys , MCSP , and Shaun Treweek , BSc , PhD American Academy of Orthotists and Prosthetists Lower Limb Prosthetic Outcome Measures : A Review of the Literature 1995 to 2005.

-Kaluf, B. (2014). Evaluation of Mobility in Persons with Limb Loss Using the Amputee Mobility Predictor and the Prosthesis Evaluation Questionnaire Y Mobility Subscale: A Six-Month Retrospective Chart Review, 26(2).

References

  1. 1.0 1.1 1.2 1.3 1.4 Gailey, R. S., Roach, K. E., Applegate, E. B., Cho, B., Cunniffe, B., Licht, S., … Cho, B. (2002). The Amputee Mobility Predictor : An Instrument to Assess Determinants of the Lower-Limb Amputee ’ s Ability to Ambulate, 83(May). https://doi.org/10.1053/apmr.2002.32309