American Academy of Orthotists & Prosthetists

Evidence Note: The Biomechanics of Ambulation after Partial Foot Amputation

Scope of Review

The purpose of this Evidence Note is to facilitate access to knowledge regarding the biomechanics of ambulation after partial foot amputation (PFA) and the effect of prosthetic and orthotic interventions.

Published research that evaluated some aspect of gait in persons with PFA, with or without a prosthesis or orthosis, was considered as part of this Evidence Note. Consistent with the International Standards Organization (ISO) definition of PFA,¹ publications describing the gait of persons with Syme's amputation (ankle disarticulation) were not considered.

Etiology

PFA is an all-too-common sequel to advanced vascular disease, typically secondary to diabetes.^2–6 Less commonly, PFA may result from trauma, limb deficiency, frostbite, or systemic disorders.^7–9

Based on data from the Vital and Health Statistics, Ambulatory and Inpatient Procedures¹⁰ and accounting for the increase in the population since 1996, it can be estimated that there are approximately 1.27 million Americans living with lower-limb amputation. More than 618,000 persons have a PFA, making the procedure nearly twice as common as either transtibial (below-knee) or transfemoral (above-knee) amputation.¹⁰ Estimates of the prevalence of limb loss in the United States for 2005 are comparable.¹¹

Given that the incidence of PFA increases exponentially after 40 years of age, almost in parallel with the incidence of diabetes,¹² one could contend that the number of persons with PFA will increase as the number of older persons and those living with diabetes increases.¹³ Similar observations have been made about the increasing incidence of lower-limb amputation more broadly.¹¹

The vast majority of PFA involve the toes and/or metatarsophalangeal joint (76 percent) with more proximal procedures, including transmetatarsal or mid-tarsal amputation, less frequently performed (24 percent).^10,14 Persons with amputation proximal to the metatarsophalangeal level experience the most significant functional deficit and are therefore likely to seek treatment from a prosthetist or orthotist.

Descriptions of Prosthetic and Orthotic Interventions

A wide range of devices have been used by persons with PFA, including foot orthoses, toe fillers, cosmetic silicone prostheses, ankle-foot orthoses, slipper sockets, or clamshell-type prostheses.^15–20 These devices are typically used with regular footwear, but on occasion may be used with "extra depth" or custom shoes. Shoe modifications, such as rocker soles, have also been used as an adjunct to prosthetic and orthotic intervention.

Generally, the extensiveness of the intervention is proportional to the extent of tissue lost. Persons with amputation affecting the toes or metatarsals may use relatively simple insoles or toe fillers. These devices are usually made from various foams or silicone-type materials aimed at redistributing pressure (typically away from the end of the remaining foot) and thereby preventing skin breakdown and ulceration. By comparison, persons with amputation at the Chopart level (midtarsal disarticulation) may use a more extensive clamshell-type prosthesis incorporating a rigid laminated socket that encompasses the leg and remaining foot. As well as protecting the residuum from skin breakdown, these devices aim to improve gait by replacing the effective foot length.

Summary of the Evidence

A single systematic review describing the biomechanics of ambulation after PFA was identified.²¹ This review formed the basis of the American Academy of Orthotists and Prosthetists (the Academy) Eighth State of the Science conference. The review appraised 28 publications from an unconstrained literature search to December 2006. The review included findings from a doctoral dissertation²² that has since been published.^23,24 The additional studies^25,26 published since this review did not meet the criteria defined in the scope of this Evidence Note.

The majority of publications included in this systematic review were observationalⁱ with only a few experimental studiesⁱⁱ comparing the effect of different prosthetic and orthotic interventions on gait.²¹

While the review concluded that there was a "high" level of evidence that PFA affects many aspects of gait (i.e., temporospatial, ankle kinematics and kinetics, as well as plantar pressures), there was little confidence in the evidence regarding how these aspects of gait are changed by PFA or prosthetic and orthotic intervention.²¹ For example, there was a "high" level of evidence that PFA had an effect on sagittal plane ankle kinematics during gait but only a "low" level of evidence that PFA changes the magnitude or timing of the dorsiflexion peak during stance or that differences exist based on amputation level.

In general, there is "insufficient" evidence regarding the efficacy of particular prosthetic and orthotic interventions because the majority of publications were observational and the few experimental studies were often inadequately designed.²¹

The depth of our understanding of the effects of PFA and the influence of prosthetic and orthotic intervention on the biomechanics of walking has been limited by a number of consistent flaws in the design of the research.²¹ For example, amputee cohorts tended to be quite heterogeneous in terms of time since amputation,^6,28–32 amputation level (including the number of toes amputated),^9,33–35 age,^9,28 and involvement of the contralateral lower limb.^28–31 Experimental studies often failed to match study groups to control for the influence of systemic disease.^6,32,34,36 This makes it difficult to know whether the differences observed between experimental conditions reflect the intervention or merely the underlying disease in one of the experimental groups.

Despite these problems, there is some limited evidence describing how persons with PFA walk and the influence of prosthetic and orthotic intervention. The following provides a brief summary of the findings of the systematic review; however, more research is needed to improve the level of confidence in these findings.²¹

Persons with PFA walk at much the same speed as appropriately matched controls.^33,37 The slower velocity often observed in persons with PFA^28–33 seems to be attributable to the influence of diabetes, rather than the amputation itself.

Power generation across the affected ankle during gait is virtually negligible once the metatarsal heads have been compromised, regardless of the residual foot length or the type of prosthetic and orthotic intervention provided.^6,7,23,38

Insoles, toe fillers, and slipper sockets do not allow the center of pressure (CoP) to progress beyond the end of the remaining foot until after contralateral heel contact, when weight is shifted to the unaffected limb.^23,39 In contrast, clamshell-type devices often provided to persons with Chopart amputation seem to normalize the CoP excursion^23,39 as did a BlueRocker™ ToeOff® orthosis.⁴⁰

It has been hypothesized that the ability of a prosthesis to restore the effective foot length requires a suitably stiff forefoot capable of supporting the amputee's body mass, a socket or anterior leg shell capable of comfortably distributing to the leg and remaining foot the interface pressures caused by loading the toe lever, and a relatively stiff connection between the foot and leg segment to help moderate the moments caused by loading the toe lever.^21,23,39 Either a rigid ankle, a free joint with a dorsiflexion stop, or the sort of stiffness inherent in a BlueRocker ToeOff orthosis may be appropriate.^21,39,40

There is a moderate level of evidence that PFA causes an increase in peak forefoot pressures compared to the contralateral side.^30,36,41–44 There is insufficient evidence to suggest that prosthetic and orthotic interventions have an effect on pressure distribution compared to footwear alone because only one paper30 directly compared various pressure-reduction interventions.

Future Research

There is a need to improve the depth of knowledge on this topic. Well-designed observational studies are needed to help answer basic questions about the gait of persons with PFA so that we can move toward well-rationalized comparative-effectiveness studies of prosthetic and orthotic interventions.²¹

In some cases, the "low" level of evidence on this topic could be improved by independent verification of findings that are currently based on a single, small, well-executed investigation whose evidence cannot, in isolation, be vested with great confidence.²¹ In other cases, consistent flaws in research design limited confidence in the findings, and researchers should consider these issues when designing future investigations.²¹

Although challenging, many of the flaws in research design can be addressed with careful consideration and planning. For example, researchers should better match amputee and control groups for systemic disease, age, and contralateral involvement; randomize the order of experimental conditions; employ repeated-measures designs; and better describe the prosthetic and orthotic interventions being studied.²¹

Acknowledgments

This Evidence Note was compiled by Michael Dillon, PhD, with the assistance of Stefania Fatone, PhD. This Evidence Note was made possible by the American Academy of Orthotists and Prosthetists through a grant (Award Number H235K080004) from the U.S. Department of Education. The contents do not necessarily represent the policy of the Department of Education, and you should not assume endorsement by the Federal Government. Thanks to Scott Magis for the illustrations.

Suggested Citation

Dillon M and Fatone S. Evidence Note: The Biomechanics of Ambulation after Partial Foot Amputation. Washington DC: American Academy of Orthotists and Prosthetists. 2009.

References

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2. Mueller MJ, Allen BT, Sinacore DR. Incidence of skin breakdown and higher amputation after transmetatarsal amputation: implications for rehabilitation. Arch Phys Med Rehabil. 1995;76:50–54.

3. Miller N, Dardik H, Wolodiger F, et al. Transmetatarsal amputation: the role of adjunctive revascularization. J Vasc Surg. 1991;13:705–711.

4. McKittrick LS, McKittrick JB, Risley TS. Transmetatarsal amputation for infection or gangrene in patients with diabetes mellitus. J Am Podiatr Med Assoc. 1993;83:62–78.

5. Sanders LJ, Dunlap G. Transmetatarsal amputation. A successful approach to limb salvage. J Am Podiatr Med Assoc. 1992;82:129–135.

6. Mueller MJ, Salsich GB, Bastian AJ. Differences in the gait characteristics of people with diabetes and transmetatarsal amputation compared with age-matched controls. Gait Posture. 1998;7:200–206.

7. Tang SFT, Chen CPC, Chen MJL, et al. Transmetatarsal amputation prosthesis with carbon-fiber plate: enhanced gait function. Am J Phys Med Rehabil. 2004;83:124–130.

8. Pinzur MS, Wolf B, Havey RM. Walking pattern of midfoot and ankle disarticulation amputees. Foot Ankle Int. 1997;18:635–638.

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23. Dillon MP, Barker T. Comparison of gait of persons with partial foot amputation wearing prosthesis to matched a control group: an observational study. J Rehab Res Dev. 2008;45:1335–1342.

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25. Kanade RV, Van Deursen RW, Harding KG, et al. Investigation of standing balance in patients with diabetic neuropathy at different stages of foot complications. Clin Biomech. 2008;23:1183–1191.

26. Dillon M, Hansen AH, Fatone S. Influence of marker models on ankle kinematics in persons with partial foot amputation: an investigation using a mechanical model. J Rehab Res Dev. 2008;45:567–576.

27. American Academy of Orthotists and Prosthetists. State-of-the-Science Evidence Reporting Guidelines. www.oandp.org/grants/MasterAgenda/AAOP_EvidenceReportGuidlines.pdf. Accessed June 5, 2009.

28. Mueller MJ, Salsich GB, Strube MJ. Functional limitations in patients with diabetes and transmetatarsal amputations. Phys Ther. 1997;77:937–943.

29. Mueller MJ, Strube MJ. Therapeutic footwear: enhanced function in people with diabetes and transmetatarsal amputation. Arch Phys Med Rehabil. 1997;78:952–956.

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34. Boyd LA, Rao SS, Burnfield JM, et al. Forefoot rocker mechanisms in individuals with partial foot amputation. Paper presented at the Gait and Clinical Movement Analysis; March 10–13, 1999; Dallas, TX.

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39. Dillon MP, Barker TM. Can partial foot prostheses effectively restore foot length? Prosthet Orthot Int. 2006;30:17–23.

40. Wilson EJ. Restoring Centre of Pressure Excursion in Partial Foot Amputees using ToeOFF-style Orthoses [dissertation]. Bundoora: National Centre for Prosthetics and Orthotics; 2005; La Trobe University.

41. Garbalosa JC, Cavanagh PR, Wu G, et al. Foot function in diabetic patients after partial amputation. Foot Ankle Int. 1996;17:43–48.

42. Armstrong DG, Lavery LA. Plantar pressures are higher in diabetic patients following partial foot amputation. Ostomy Wound Manage. 1998;44:30–32.

43. Lavery LA, Lavery DC, Quebedeax-Farnham TL. Increased foot pressures after great toe amputation in diabetes. Diabetes Care. 1995;18:1460–1462.

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