Amputee Mobility Predictor

Last Updated

November 04, 2017

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Purpose

This instrument measures the ambulatory potential of lower limb amputees with and without the use of prosthesis. It assesses the mobility of people with lower limb amputation prior to prosthetic fitting and predicts function following prosthetic prescription. The AMP has two sub-categories: Amputee Mobility Predictor with prosthesis (AMPPRO) and Amputee Mobility Predictor without prosthesis (AMPnoPRO).

Link to Instrument

Instrument Details

Acronym AMP

Assessment Type

Performance Measure

Cost

Free

Cost Description

Cost of equipment

Diagnosis/Conditions

Limb Loss & Impairment

Limb Loss and Amputation

A 21-item (AMPPRO) and 20-item (AMPnoPRO) objective measure
Static and dynamic sitting and standing activities, as well as transfer and gait skills of progressing difficulty are performed
Score range: AMPPRO 0-42 (47 if assistive device is included) and AMPnoPRO 0-38 (43 if assistive device is included). Higher scores indicate better mobility.
Every item has a key based on which it is scored, with every score having a different implication for every item.
Items 1, 11, 14, 15 (four scores are required for each leg) and 16 have scores ranging from 0 – 1.
Items 2, 3, 4, 5, 6, 7, 8 (two scores required for each leg), 9, 10, 12, 13, 17, 18, 19, 20 (one score each for ascending and descending) are scored as 0, 1 or 2.
Item 21 (assistive device selection) can possibly have a score ranging from 0 to 5 wherein every selection has been assigned a different score in increasing order of function.
For scoring form and protocol: https://www.ncbi.nlm.nih.gov/pubmed/11994800

Number of Items

21-item (AMPPRO)

20-item (AMPnoPRO)

Stopwatch
2 Chairs
12-inch ruler
Pencil
4-inch high obstacle
A set of stairs with 3 steps
15-ft walkway

10-15 minutes

Required Training

Reading an Article/Manual

Instrument Reviewers

Archana Kulkarni, PT April 2016; Mike Richardson, PT, DPT, GCS, COMT November 2017

Body Part

Lower Extremity

ICF Domain

Activity
Participation

Considerations

The item selection in the AMP is such that they are arranged in the level of increasing difficulty, so as to include patients who do/do not have adequate balance to perform the items.
Bilateral amputee (Syme’s amputation and higher) patients were included for the reliability part of the Gailey et al. study; however, they were excluded from the validity study. Therefore, all subjects for the validity study had to be unilateral amputee patients, with the exception of partial foot amputation on the contralateral side.
Bilateral amputee subjects with amputation levels higher than transtarsal foot amputations may be tested only with the AMPPRO because it is not physically possible for them to perform the AMPnoPRO.
An additional version for people with bilateral lower limb loss (AMP-B) is available that has slight modifications in scoring on 5 items (Raya et al., 2013)

Standard Error of Measurement (SEM)

Unilateral lower-limb amputation: (Resnik & Borgia, 2011; n = 44; (Amputation type: Transfemoral = 23 (52.3%), knee disarticulation = 2 (4.5%), Transtibial = 19 (43.2%); mean age = 66 (13.0) years; Limb loss of at least 2 years and current prosthesis user for at least 6 months)

SEM for entire group (n = 44): 1.5 points
No SEM reported for different amputation levels

Minimal Detectable Change (MDC)

Unilateral lower-limb amputation: (Resnik & Borgia, 2011)

MDC₉₀ for entire group (n = 44): 3.4 points
No MDC₉₀reported for different amputation levels

Normative Data

Lower limb amputees: (Gailey et al., 2002; n = 191, average time since amputation = 68 ± 111.15 months):

Normative data for lower limb amputees has been established according to the K classification, which contains descriptive functional levels for prosthetic users and classifies them under K0, K1, K2, K3 and K4 categories.

K0	Functional Level 0	The patient does not have the ability or potential to ambulate or transfer safely with or without assistance and a prosthesis does not enhance their quality of life or mobility.
K1	Functional Level 1	The patient has the ability or potential to use a prosthesis for transfer or ambulation on level surfaces at fixed cadence. Typical of the limited and unlimited household ambulator.
K2	Functional Level 2	The patient has the ability or potential for ambulation with the ability to traverse low-level environmental barriers such as curbs, stairs or uneven surfaces. Typical of the limited community ambulator.
K3	Functional Level 3	The patient has the ability or potential for ambulation with variable cadence. Typical of the community ambulator who has the ability to traverse most environmental barriers and may have vocational, therapeutic or exercise activity that demands prosthetic utilisation beyond simple locomotion.
K4	Functional Level 4	The patient 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

The normative values for each of the categories are (Gailey et al., 2002):

	AMPnoPRO	AMPPRO
K0	N/A	0-8
K1	9.7 ± 9.5	25.0 ± 7.4
K2	25.3 ± 7.3	34.7 ± 6.5
K3	31.4 ± 7.4	40.5 ± 3.9
K4	38.5 ± 3.0	44.7 ± 1.8

Test/Retest Reliability

Lower limb amputees (Gailey et al., 2002; n = 24, mean age = 68.3 years)

Excellent test-retest reliability (ICC = 0.96)
Good instrument stability with little variation from the initial testing period to follow-up 3 weeks later.

Lower-limb amputation (unilateral): (Resnik & Borgia, 2011)

Excellent test-retest reliability ICC = .88 (CI₉₅ = .79 - .93)

Interrater/Intrarater Reliability

Lower limb amputees (Gailey et al., 2002)

Excellent interrater reliability for subjects tested with and without prosthesis, ICC = 0.99
Excellent intrarater reliability for subjects tested with prosthesis (0.96), and for subjects tested without prosthesis (ICC = 0.97)

Criterion Validity (Predictive/Concurrent)

Predictive validity:

Lower limb amputation (Gailey et al., 2002; n = 167; mean age = 54.8 years, average time since amputation = 68 ± 111.15 months)

Excellent predictive validity with 6 minute walk test (F = 66.389, r = 0.78)

Bilateral lower limb amputation (Raya et al., 2013; n = 26)

Excellent predictive validity of AMP with New Injury Severity Score (NISS) (r = -0.82)
Excellent predictive validity of AMP with 6 minute walk test (r = 0.60)
Excellent predictive validity of Amputee Mobility Predictor – Bialteral (AMP-B) with NISS (r = -0.79)
Excellent predictive validity of AMP-B with 6 minute walk test (r = 0.60)

Concurrent validity:

Lower limb amputation (Gailey et al., 2002)

Excellent concurrent validity with 6 minute walk test in patients without prosthetics (r = 0.69, P < 0.0001)
Excellent concurrent validity with 6 minute walk test in patients with prosthetics (r = 0.82, P < 0.001)
Excellent concurrent validity with age in patients without prosthetics (r = -0.69, P < 0.0001)
Adequate concurrent validity with age in patients with prosthetics (r = -0.56, P < 0.001)

Construct Validity

Convergent Validity:
Lower limb amputation (bilateral): (Raya et al., 2013; n = 26; bilateral transtibial amputation: n = 12; bilateral transfemoral amputation: n = 7; combination transfemoral/transtibial: n = 7; all military (active or retired) servicemen; ability to ambulate at least 250 feet in 6 minutes; mean age 28.6 (5.5) years)
Excellent correlation with 6MWT (r = .603)
Lower-limb amputations (unilateral): (Gailey et al., 2002; n = 167 for validity portion subset)
Excellent correlations between 6-minute walk test (6MWT) and AMPPRO (r = .82, p < .001), AMPnoPRO (r = .69, p < .001)
Excellent correlations between Amputee Activity Survey (AAS) and AMPPRO (r = .77, p < .001), AMPnoPRO (r = .67, p < .001)
Discriminant Validity:
Lower-limb amputations (unilateral): (Gailey et al., 2002; n = 167 for validity portion subset)

Comparison of K-level Groups’ AMPPRO, AMPnoPRO, 6MWT, and AAS Scores
Mean Measure	K 0-1	K2	K3	K4	P (1-way ANOVA)
*n =*	18	43	67	39
AMPnoPRO (SD)	9.67 (9.51)	25.28 (7.32)	31.36 (7.38)	38.49 (3.03)	.0001^*
AMPPRO (SD)	25.00 (7.37)	34.65 (6.49)	40.50 (3.90)	44.67 (1.75)	.0001^*
6MWT (m) (SD)	49.86 (29.82)	189.90 (111.30)	298.64 (102.37)	419.46 (86.15)	.0001^*
AAS	-36.50 (25.19)	-7.51 (27.47)	11.28 (20.29)	27.77 (14.06)	.0001^*
6MWT: Six-minute walk test; SD: Standard Deviation; ANOVA: Analysis of Variance; AAS: Amputee Activity Survey; (*) significant findings (P < .001)

The researchers found a statistically significant difference among the K-level categories, however significant overlap among the categories was noted (Deathe et al., 2009)
Lower-limb loss (unilateral): (Kaluf, 2014; n = 123; amputation level: transtibial (TT) n = 90, transfemoral amputation (TF) n = 33; K-levels: K2, n = 25 (16 TT, 9 TF), mean age 67.6 (11.3) years; K3, n = 83 (64 TT, 19 TF), mean age 60.8 (13.7) years; K4, n = 15 (10 TT, 5 TF), mean age 38.9 (23.3) years; Retrospective chart review of 120 charts)
The AMPPRO did not find a significant difference between patients at the K3 and K4 levels, which may indicate a possible ceiling effect.

Comparison of AMPPRO and PEQ-MS scores for levels K2-4
Outcome Measure		K2	K3	K4		p
AMPPRO	Mean	29	38	43.5	ANOVA	.0027^*
	Median	25.5	41	44
	n	6	43	8	Kruskal-Wallis	.0035^*
	SD	8.1	7.9	2.3
PEQ-MS	Mean	16.7	31.4	37.9	ANOVA	.0005^*
	Median	17.5	31	37
	n	6	43	7	Kruskal-Wallis	.0024^*
	SD	8.5	9.9	6.1
AMPPRO, Amputee Mobility Predictor with prosthesis; PEQ-MS, Prosthetic Evaluation Questionnaire-Mobility Subscale; ANOVA, analysis of variance

Significant difference (p < .05) between K2 and K4 (AMPPRO)
Significant difference (p < .05) between K2 and K3 (AMPPRO)
Significant difference (p < .05) between K2 and K4 (PEQ-MS)
Significant difference (p < .05) between K2 and K3 (PEQ-MS)
Unable to discriminate between K3 and K4

Content Validity

Not statistically assessed, however, the tool’s creators reported that AMP items assessed a wide range of functional skills that included items from both the Performance-Oriented Assessment of Mobility Problems (POMA) and Duke Mobility Skills Profile (DMSP) as well as including single-leg stance (Gailey et al., 2002)

Face Validity

Not statistically assessed, however, 79 clinicians (24 certified prosthetist (CP), 51 certified prosthetist and orthotist (CPO), and 4 other) surveyed indicated the AMP was the most common assessment tool used (Gaunaurd et al., 2015)

Floor/Ceiling Effects

The AMPPRO did not find a significant difference between patients at the K3 and K4 levels which may indicate a possible ceiling effect (Kaluf, 2014)

Bibliography

Deathe, A. B., Wolfe, D. L., Devlin, M., Hebert, J. S., Miller, W. C., & Pallaveshi, L. (2009). Selection of outcome measures in lower extremity amputation rehabilitation: ICF activities. Disability and Rehabilitation, 31(18), 1455–1473. https://doi.org/10.1080/09638280802639491

Gailey, R. S. (2006). Predictive outcome measures versus functional outcome measures in the lower limb amputee. Journal of Prosthetics and Orthotics, 18(6), 51–60.

Gailey, R. S., Roach, K. E., Applegate, E. B., Cho, B., Cunniffe, B., Licht, S., . . . Nash, M. S. (2002). The amputee mobility predictor: An instrument to assess determinants of a lower limb amputee's ability to ambulate. Archives of Physical Medicine and Rehabilitation, 83(5), 613-627. http://dx.doi.org/10.1053/apmr.2002.32309

Gaunaurd, I., Spaulding, S. E., Amtmann, D., Salem, R., Gailey, R., Morgan, S. J., & Hafner, B. J. (2015). Use of and confidence in administering outcome measures among clinical prosthetists: Results from a national survey and mixed-methods training program. Prosthetics and Orthotics International, 39(4), 314–321. https://doi.org/10.1177/0309364614532865

Heinemann, A. W., Connelly, L., Ehrlich-Jones, L., & Fatone, S. (2014). Outcome instruments for prosthetics: Clinical applications. Physical Medicine and Rehabilitation Clinics of North America, 25(1), 179–198. https://doi.org/10.1016/j.pmr.2013.09.002

Kaluf, B. (2014). Evaluation of mobility in persons with limb loss using the Amputee Mobility Predictor and the Prosthesis Evaluation Questionnaire - Mobility Subscale: A Six-month retrospective chart review. Journal of Prosthetics and Orthotics, 26(2), 70–76. https://doi.org/10.1097/JPO.0000000000000020

Raya, M. A., Gailey, R. S., Gaunaurd, I. A., Ganyard, H., Knapp Wood, J., McDonough, K., & Palmisano, T. (2013). Amputee mobility predictor bilateral: A performance-based measure of mobility for people with bilateral lower limb loss. Journal of Rehabilitation Research and Developement, 50(7), 961-968.

Resnik, L., & Borgia, M. (2011). Reliability of outcome measures for people with lower-limb amputations: Distinguishing true change from statistical error. Physical Therapy, 91(4), 555–565. https://doi.org/10.2522/ptj.20100287

Spaan, M. H., Vrieling, A. H., Berg, P. van de, Dijkstra, P. U., & Keeken, H. G. van. (2017). Predicting mobility outcome in lower limb amputees with motor ability tests used in early rehabilitation. Prostethics and Orthotics International, 41(2), 171–177. https://doi.org/10.1177/0309364616670397