Clinical Problem/Topic

People with lower limb amputation generally require greater effort to walk and run compared to people without amputation. The increased effort experienced by people with amputation may be reduced, in part, with the use of prosthetic devices designed to increase energy efficiency. This Clinical Knowledge Summary (CKS) presents the results of studies that assess the effects of prosthetic feet on energy efficiency during gait in people with transtibial amputation.

Background Information

The ability to move effectively and efficiently from one place to another is often impaired in people with a lower limb difference or amputation. Although mobility for someone with transtibial amputation can be partially restored through the provision of a prosthesis, even the most advanced prosthetic technologies cannot fully replicate the movement and functions of the biological limb. Thus, moving with a prosthesis is generally less efficient, and activities like walking and running require greater effort.¹ For example, energy cost (i.e., gait efficiency) at self-selected or comfortable walking speed is reported to be between 12% and 33% greater in transtibial prosthesis users than in people without amputation.^1-4 Similarly, transtibial prosthesis users require 8% to 38% more energy to run than runners without amputation.^5,6

Increasingly sophisticated prosthetic feet have been developed over the last 40 years in an attempt to mitigate the functional and metabolic deficits associated with a lower limb amputation. Advances in prosthetic materials, designs, and technology have prompted the development and commercialization of a wide variety of prosthetic feet.^7,8 Several studies have been conducted to assess whether different types of prosthetic feet can reduce energy costs associated with walking^9-18 or running^5,6 with a prosthesis. These studies have been conducted on a treadmill or overground and typically use portable respirometers or other indirect calorimetry systems to measure expired gases (Figure 1).¹⁹ Using these methods, investigators can estimate energy costs associated with a variety of activities (e.g., walking, running) and terrain conditions (e.g., level ground, inclines).

While research that assesses energetic outcomes in people with amputation is ongoing, the most recent systematic review²⁰ on the topic was published over 15 years ago and does not include the most current evidence or reflect contemporary prosthetic components and research methodologies. This CKS describes clinically-relevant findings from a 2021 systematic review and meta-analysis on energetic comparisons between prosthetic feet.²¹ The review and meta-analysis focused on studies that assess the relative effects of different prosthetic feet on transtibial prosthesis users' energetic outcomes. The results presented in this summary will inform clinicians about the influence of prosthetic foot type on gait efficiency.

Management/Clinical Practice Implications

Energy costs while walking on level ground

In general, prosthetic foot type did not influence energy costs when walking on a treadmill.^6,22-25 However, a reduction in energy costs was found for prosthetic feet with powered dorsiflexion compared to dynamic response feet when walking at slow speeds (effect size: 0.35; 95% CI: 0.06, 0.63; p=0.02).^26,27 This finding indicates that feet with powered dorsiflexion may have energetic benefits for users walking on level ground, but other types of feet are unlikely to meaningfully affect energy costs.

Energy costs while walking on inclines/declines

Compared to dynamic response feet, prosthetic feet with powered dorsiflexion significantly reduced energy costs when walking on a declined (-5 degree) treadmill (effect size: 0.51; 95% CI: 0.21, 0.80; p=0.001).^26,27 This finding suggests that people with amputation can descend ramps and hills with improved efficiency when using feet that have powered control of dorsiflexion. There was insufficient evidence to determine the effect of powered prosthetic feet on inclines.

Energy costs while running on level ground

In general, prosthetic foot type did not influence energy costs while running in comparisons of SACH and dynamic response feet and comparisons of dynamic response and running-specific feet. These results were drawn from small, pooled samples (<9 participants total), and the variability of data from these small samples may have contributed to the lack of significant findings.

Other findings from single studies

Unconfirmed results of single studies not included in meta-analyses indicated the following: (1) multi-axis feet may decrease energy costs relative to SACH feet on level terrain;¹⁴ (2) feet with integrated vertical shock absorption may reduce energy costs at fast walking speeds;²³ and (3) J-shaped running-specific feet may reduce energy costs compared to C-shaped designs when running on level ground.²⁸

Evidence

Studies

This systematic review and meta-analysis on energetic comparisons between feet included findings from 15 articles published between 1992 and 2018.²¹ Data from studies that compared the same foot types at similar speeds, and conditions were grouped. The number of studies that compared any two types of feet ranged between one and five. If at least two studies were available for any comparison, a meta-analysis was used to assess the effect of foot type on energy costs across studies.

Sample size

Data from a total of 141 participants were included from the reviewed studies. The median sample size was eight participants, and samples ranged from 3-27 across studies. Thus, most studies may not have sufficient sample sizes to detect significant differences.

Participant characteristics

Study samples were predominantly male (88%) with unilateral amputation (96%) from non-dysvascular causes (88%). Most participants (56%) were classified as unlimited community ambulators or active adults. Thus, the findings of this review and meta-analysis are best generalized to men with unilateral amputation from non-dysvascular etiologies. Use caution when generalizing results to patients not well-represented in this body of literature.

1. Waters RL, Mulroy S. The energy expenditure of normal and pathologic gait. Gait Posture. 1999;9(3):207-31.
2. Genin JJ, Bastien GJ, Franck B, Detrembleur C, Willems PA. Effect of speed on the energy cost of walking in unilateral traumatic lower limb amputees. Eur J Appl Physiol. 2008;103(6):655-63.
3. Gailey RS, Wenger MA, Raya M, Kirk N, Erbs K, Spyropoulos P, et al. Energy expenditure of trans-tibial amputees during ambulation at self-selected pace. Prosthet Orthot Int. 1994;18(2):84-91.
4. Pinzur MS. The metabolic cost of lower extremity amputation. Clin Podiatr Med Surg. 1997;14(4):599-602.
5. Brown MB, Millard-Stafford ML, Allison AR. Running-specific prostheses permit energy cost similar to nonamputees. Med Sci Sports Exerc. 2009;41(5):1080-7.
6. Mengelkoch LJ, Kahle JT, Highsmith MJ. Energy costs & performance of transtibial amputees & non-amputees during walking & running. Int J Sports Med. 2014;35(14):1223-8.
7. Laferrier JZ, Gailey R. Advances in lower-limb prosthetic technology. Phys Med Rehabil Clin N Am. 2010;21(1):87-110.
8. Versluys R, Beyl P, Van Damme M, Desomer A, Van Ham R, Lefeber D. Prosthetic feet: state-of-the-art review and the importance of mimicking human ankle-foot biomechanics. Disabil Rehabil Assist Technol. 2009;4(2):65-75.
9. Au SK, Weber J, Herr H. Powered Ankle-Foot Prosthesis Improves Walking Metabolic Economy. IEEE Trans Robot. 2009;25(1):51-66.
10. Grabowski AM, Rifkin J, Kram R. K3 PROMOTER prosthetic foot reduces the metabolic cost of walking for unilateral transtibial amputees. J Prosthet Orthot. 2010;22(2):113-20.
11. Klodd E, Hansen A, Fatone S, Edwards M. Effects of prosthetic foot forefoot flexibility on oxygen cost and subjective preference rankings of unilateral transtibial prosthesis users. J Rehabil Res Dev. 2010;47(6):543-52.
12. Zelik KE, Collins SH, Adamczyk PG, Segal AD, Klute GK, Morgenroth DC, et al. Systematic variation of prosthetic foot spring affects center-of-mass mechanics and metabolic cost during walking. IEEE Trans Neural Syst Rehabil Eng. 2011;19(4):411-9.
13. Segal AD, Zelik KE, Klute GK, Morgenroth DC, Hahn ME, Orendurff MS, et al. The effects of a controlled energy storage and return prototype prosthetic foot on transtibial amputee ambulation. Hum Mov Sci. 2012;31(4):918-31.
14. Delussu AS, Paradisi F, Brunelli S, Pellegrini R, Zenardi D, Traballesi M. Comparison between SACH foot and a new multiaxial prosthetic foot during walking in hypomobile transtibial amputees: physiological responses and functional assessment. Eur J Phys Rehabil Med. 2016;52(3):304-9.
15. Lacraz A, Armand S, Turcot K, Carmona G, Stern R, Borens O, et al. Comparison of the Otto Bock solid ankle cushion heel foot with wooden keel to the low-cost CR-Equipements solid ankle cushion heel foot with polypropylene keel: A randomized prospective double-blind crossover study assessing patient satisfaction and energy expenditure. Prosthet Orthot Int. 2016.
16. Quesada RE, Caputo JM, Collins SH. Increasing ankle push-off work with a powered prosthesis does not necessarily reduce metabolic rate for transtibial amputees. J Biomech. 2016;49(14):3452-9.
17. Gardiner J, Bari AZ, Howard D, Kenney L. Transtibial amputee gait efficiency: Energy storage and return versus solid ankle cushioned heel prosthetic feet. J Rehabil Res Dev. 2016;53(6):1133-8.
18. McDonald CL, Kramer PA, Morgan SJ, Halsne EG, Cheever SM, Hafner BJ. Energy expenditure in people with transtibial amputation walking with crossover and energy storing prosthetic feet: A randomized within-subject study. Gait Posture. 2018;62:349-54.
19. Macfarlane DJ. Open-circuit respirometry: a historical review of portable gas analysis systems. Eur J Appl Physiol. 2017;117(12):2369-86.
20. Hofstad C, Linde H, Limbeek J, Postema K. Prescription of prosthetic ankle-foot mechanisms after lower limb amputation. Cochrane Database Syst Rev. 2004(1):Cd003978.
21. Hafner BJ, Halsne EG, Morgan SJ, Morgenroth DC, Humbert AT. Effects of prosthetic feet on metabolic energy expenditure in people with transtibial amputation: a systematic review and meta-analysis. PM R. 2021.
22. Barth DG, Schumacher L, Thomas SS. Gait analysis and energy cost of below-knee amputees wearing six different prosthetic feet. J Prosthet Orthot. 1992;4(2):63-75.
23. Hsu M, Nielsen DH, Yack HJ, Shurr DG. Physiological measurements of walking and running in people with transtibial amputations with 3 different prostheses. J Ortho Sport Phys Ther. 1999;29(9):526-33.
24. Schmalz T, Blumentritt S, Jarasch R. Energy expenditure and biomechanical characteristics of lower limb amputee gait: The influence of prosthetic alignment and different prosthetic components. Gait Posture. 2002;16(3):255-63.
25. Hsu M, Nielsen DH, Lin-Chan S, Shurr D. The effects of prosthetic foot design on physiologic measurements, self-selected walking velocity, and physical activity in people with transtibial amputation. Arch Phys Med Rehabil. 2006;87(1):123-9.
26. Delussu AS, Brunelli S, Paradisi F, Iosa M, Pellegrini R, Zenardi D, et al. Assessment of the effects of carbon fiber and bionic foot during overground and treadmill walking in transtibial amputees. Gait Posture. 2013;38(4):876-82.
27. Darter BJ, Wilken JM. Energetic consequences of using a prosthesis with adaptive ankle motion during slope walking in persons with a transtibial amputation. Prosthet Orthot Int. 2014;38(1):5-11.
28. Beck ON, Taboga P, Grabowski AM. Prosthetic model, but not stiffness or height, affects the metabolic cost of running for athletes with unilateral transtibial amputations. J Appl Physiol. 2017;123(1):38-48.

Reference for Full Systematic Review

Hafner BJ, Halsne EG, Morgan SJ, Morgenroth DC, Humbert AT. Effects of prosthetic feet on metabolic energy expenditure in people with transtibial amputation: a systematic review and meta-analysis. PM R. 2021.

Acknowledgments

This work was supported by a research grant from the American Academy of Orthotists and Prosthetists and the Office of the Assistant Secretary of Defense for Health Affairs through the Orthotics and Prosthetics Outcomes Research Program under Award No. W81XWH-15-1-0458.

Suggested Citation

Morgan SJ, Halsne EG, Morgenroth DC, Humbert AT, Hafner BJ. American Academy of Orthotists and Prosthetists (AAOP) Clinical Knowledge Summary: Effects of prosthetic feet on metabolic energy expenditure in transtibial amputation patients. Washington DC, 2021.