Michael P. Dillon

Development and preliminary testing of a device for the direct measurement of forces and moments in the prosthetic limb of transfemoral amputees during activities of daily living

Purpose: To provide a comprehensive description of the direct measurement of forces and moments applied on the socket of transfemoral amputees during daily living activities. Methods: The forces and moments applied on the socket of one female transfemoral amputee were measured with a commercial transducer at a sampling frequency of 200 Hz and recorded at distance using a wireless modem to transmit the data. The subject was asked to walk in a straight line and around a circle as well as to ascend and descend a slope and stairs. The subject was instructed to perform each activity at her natural pace and as she would usually perform it during daily life. Results: The results were based on a high number of gait cycles of the prosthetic leg for each activity. For instance, 62 gait cycles were measured during level walking in a straight line. Ascending a slope produced a larger moment around the mediolateral axis than walking over the entire support phase. In addition, walking around a circle produced a higher moment about the long axis of the socket than walking during the push-off phase of the support. The mean stride frequency while descending a slope was higher than straight level walking. All the other activities presented a slower mean stride frequency than straight level walking. The impulse on the three axes was similar or smaller than walking in a straight line for all of the activities except for walking around a circle on the mediolateral axis, as well as ascending a slope and stairs and walking around a circle on the long axis. Conclusion: An apparatus to directly measure the actual forces and moments applied to the socket of the transfemoral amputees during an unlimited number of steps and a wide range of activities is presented. The apparatus presented here could be used by multidisciplinary teams, including engineers, prosthetists, and physiotherapists, facing the challenge of safely restoring the locomotion of transfemoral amputees fitted with a conventional socket or, in particular, an osseointegrated implant.

Erratum to: Describe the outcomes of dysvascular partial foot amputation and how these compare to transtibial amputation: a systematic review protocol for the development of shared decision making resources

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Developing Core Sets for persons following amputation based on the International Classification of Functioning, Disability and Health as a way to specify functioning

Amputation is a common late stage sequel of peripheral vascular disease and diabetes or a sequel of accidental trauma, civil unrest and landmines. The functional impairments affect many facets of life including but not limited to: Mobility; activities of daily living; body image and sexuality. Classification, measurement and comparison of the consequences of amputations has been impeded by the limited availability of internationally, multiculturally standardized instruments in the amputee setting. The introduction of the International Classification of Functioning, Disability and Health (ICF) by the World Health Assembly in May 2001 provides a globally accepted framework and classification system to describe, assess and compare function and disability. In order to facilitate the use of the ICF in everyday clinical practice and research, ICF core sets have been developed that focus on specific aspects of function typically associated with a particular disability. The objective of this paper is to outline the development process for the ICF core sets for persons following amputation. The ICF core sets are designed to translate the benefits of the ICF into clinical routine. The ICF core sets will be defined at a Consensus conference which will integrate evidence from preparatory studies, namely: (a) a systematic literature review regarding the outcome measures of clinical trails and observational studies, (b) semi-structured patient interviews, (c) international experts participating in an internet-based survey, and (d) cross-sectional, multi-center studies for clinical applicability. To validate the ICF core sets field-testing will follow. Invitation for participation: The development of ICF Core Sets is an inclusive and open process. Anyone who wishes to actively participate in this process is invited to do so.

Preservation of Residual Foot Length in Partial Foot Amputation: A Biomechanical Analysis

Background: Partial foot amputation may be preferred to more proximal amputation because of the perceived improvement in function associated with preserving foot length and the ankle joint complex, thus enabling normal gait and push-off. Clinically, partial foot amputees display significant wasting of the triceps surae musculature, strongly indicative of disuse. This investigation aimed to examine the belief that preserving residual foot length should be the primary operative objective necessary to maintain normal foot and ankle function. Method: The gait patterns of eight partial foot amputees and a cohort of matched nonamputee control subjects were analyzed using a peak three-dimensional (3D) motion analysis system incorporating an AMTI force platform (Advanced Mechanical Technology Inc., Waterton, MA). Amputee subjects used their own prostheses for the evaluation. Results: Amputations disarticulating the metatarsophalangeal (MTP) joint had little impact on the normal pattern of ankle power generation. However, amputation proximal to the MTP joint level resulted in virtually negligible power generation across the ankle, regardless of residual foot length. Subjects compensated for the lack of ankle power generation by adopting strategies in which the hip became the primary source of power to advance the body forward. Conclusions: The primary reason for a partial foot amputation is to preserve the normal function of the foot and ankle complex associated with push-off. As such, surgery should strive to preserve the metatarsal heads to allow amputees to use the ankles contribution to walking. Given that amputation proximal to the metatarsal heads compromised the normal propulsive function of the foot and ankle, surgery should not strive to preserve residual foot length to maintain function but should instead aim to achieve good distal tissue coverage and healing, particularly given that the hip joint(s), not the ankle, become the primary source of power for walking.

Biomechanics of Ambulation after Partial Foot Amputation: A Systematic Literature Review.

The purpose of this systematic review was to establish what is known about gait and prosthetic/orthotic intervention in persons with partial foot amputation (PFA) and to identify what needs to be known to optimize gait and prosthetic/orthotic intervention. A systematic search of the literature identified 437 citations, with 28 publications selected for review based on inclusion criteria. Studies analyzing the gait of PFA were generally published in the last two decades in a myriad of journals spanning many disciplines. Publications that met the inclusion criteria were predominantly classified as case-control or cross-sectional studies and were reviewed based on various aspects of the biomechanics of gait, including temporospatial, ground reaction force (GRF), center of pressure (CoP) excursion, kinematics, kinetics, plantar pressure, electromyography, and energy expenditure. Studies reporting results for each variable were described, methodological issues identified and discussed, and the results summarized. The quality of the evidence was then rated as high, moderate, low, or insufficient for a number of outcome statements based on the various aspects of the biomechanics of gait. Overall, there was a high level of evidence that PFA generally affects temporospatial, GRF, ankle kinetics, and plantar pressures during gait, but there was less confidence in the evidence regarding more detailed statements about exactly how these aspects of gait are affected by PFA. This is reflective of the small and heterogenous populations included in the reviewed literature. Because the studies were largely observational, there is insufficient evidence regarding the efficacy of specific prosthetic and orthotic interventions, although generally there was low to moderate evidence that prosthetic and orthotic interventions affect ankle kinematics and moments and may moderate CoP progression. There remains the need to further our understanding of the biomechanics of PFA gait and establish hypotheses regarding prosthetic and orthotic requirements for improved ambulation/function and protection of the residuum.

Can partial foot prostheses effectively restore foot length

Our understanding of how partial foot prostheses function stems from static force analyses, where assumptions about the location of the ground reaction force during terminal stance have been made. While such assumptions seemed reasonably based on an understanding of normal gait, they are often illogical based on what is observed clinically. As such, the aim of this work was to evaluate the belief that partial foot prostheses are able to restore the effective foot length. Centre of pressure (CoP) excursion data were collected as part of a complete gait analysis incorporating an Advanced Mechanical Technology Inc. force platform. The CoP excursion patterns, observed in a cohort of eight partial foot amputees and matched control subjects, highlight the inability of toe fillers and slipper sockets to restore the ‘effective’ foot length in transmetatarsal and Lisfranc amputees, whereas clamshell prostheses fitted to the Chopart amputees were able to restore the effective foot length. In the transmetatarsal and Lisfranc amputees, the observed CoP excursion patterns could indicate a learned gait strategy necessary to reduce the requirement of the weak triceps surae musculature as well as spare the sensitive distal stump from extreme forces. The toe fillers and slipper sockets fitted to these amputees may not be stiff enough to support the amputees body weight or the device may not be designed appropriately to assist the weakened triceps musculature to resist the external moments caused by loading the forefoot. The clamshell prostheses restored the ‘effective’ foot length due to the rigid toe lever and clamshell socket, which could allow and comfortably support the generation of substantial external moments during terminal stance.

Incidence of lower limb amputation in Australian hospitals from 2000 to 2010

Background: Contemporary literature reports that the incidence of lower limb amputation has declined in many countries. This impression may be misleading given that many publications only describe the incidence of lower limb amputations above the ankle and fail to include lower limb amputations below the ankle. Objectives: To describe trends in the incidence of different levels of lower limb amputation in Australian hospitals over a 10-year period. Study design: Descriptive. Method: Data describing the age-standardised incidence of lower limb amputation were calculated from the Australian National Hospital Morbidity database and analysed for trends over a 10-year period. Results: The age-standardised incidence of lower limb amputation remained unchanged over time (p = 0.786). A significant increase in the incidence of partial foot amputations (p = 0.001) and a decline in the incidence of transfemoral (p = 0.00) and transtibial amputations (p = 0.00) were observed. There are now three lower limb amputations below the ankle for every lower limb amputation above the ankle. Conclusion: While the age-standardised incidence of all lower limb amputation has not changed, a shift in the proportion of lower limb amputations above the ankle and lower limb amputations below the ankle may be the result of improved management of precursor disease that makes partial foot amputation a more commonly utilised alternative to lower limb amputations above the ankle. Clinical relevance This article highlights that although the incidence of lower limb amputation has remained steady, the proportion of amputations above the ankle and below the ankle has changed dramatically over the last decade. This has implications for how we judge the success of efforts to reduce the incidence of lower limb amputation and the services required to meet the increasing proportion of persons with amputation below the ankle.

Effect of inaccuracies in anthropometric data and linked-segment inverse dynamic modeling on kinetics of gait in persons with partial foot amputation.

The accuracy of data derived from linked-segment models depends on how well the system has been represented. Previous investigations describing the gait of persons with partial foot amputation did not account for the unique anthropometry of the residuum or the inclusion of a prosthesis and footwear in the model and, as such, are likely to have underestimated the magnitude of the peak joint moments and powers. This investigation determined the effect of inaccuracies in the anthropometric input data on the kinetics of gait. Toward this end, a geometric model was developed and validated to estimate body segment parameters of various intact and partial feet. These data were then incorporated into customized linked-segment models, and the kinetic data were compared with that obtained from conventional models. Results indicate that accurate modeling increased the magnitude of the peak hip and knee joint moments and powers during terminal swing. Conventional inverse dynamic models are sufficiently accurate for research questions relating to stance phase. More accurate models that account for the anthropometry of the residuum, prosthesis, and footwear better reflect the work of the hip extensors and knee flexors to decelerate the limb during terminal swing phase.

Quality of life in persons with partial foot or transtibial amputation: A systematic review

Study design: Systematic review. Background: Common beliefs about quality of life in people with partial foot and transtibial amputation are often described as passing comments in the literature with seeming little research evidence. A clear understanding of the research evidence is important to inform decisions about amputation level from a quality of life perspective. Objective: To systematically gather and appraise research evidence comparing quality of life between persons with partial foot and transtibial amputation. Methods: A comprehensive suite of databases (e.g. Cochrane Library, MEDLINE and Web of Science) were searched using terms relating to amputation level and quality of life. Reference lists of articles that met the inclusion criteria were hand searched. Included studies reported quantitative data for persons with partial foot and transtibial amputation secondary to peripheral vascular disease and diabetes. Studies were appraised using the McMaster University Critical Review form. Results: There is insufficient evidence comparing quality of life in people with partial foot and transtibial amputation. The available evidence suggests that quality of life may be very similar in people with partial foot and transtibial amputation and the small differences are not likely to be clinically meaningful. Conclusion: Without adequate evidence comparing quality of life in people with partial foot and transtibial amputation, it is difficult to inform decisions about amputation level from a quality of life perspective. Clinical relevance There is insufficient evidence about differences in QoL between persons with PFA or TTA. Contrary to common belief, the available evidence suggests that QoL may be similar in persons with PFA and TTA. Further research is needed to inform decisions about amputation level from a QoL perspective.

Effect of prosthetic design on center of pressure excursion in partial foot prostheses

Investigations into the gait of persons with partial foot amputation (PFA) suggest that the effective foot length can be restored when the prosthesis incorporates a relatively stiff forefoot, restricts dorsiflexion, and includes a mechanism whereby forces caused by loading the toe lever can be comfortably distributed to the leg (e.g., an anterior tibial shell). The purpose of this investigation was to systematically alter these variables to understand which design elements are responsible for restoration of the effective foot length. By manipulating features of the prosthesis design in two persons with PFA, we demonstrated using three-dimensional motion analysis that the prosthesis must incorporate each of these design elements to restore the effective foot length. When these design elements were used in concert, the persons with PFA adopted a gait pattern more consistent with nondisabled persons. Further work is required on a larger cohort to ensure the observations are generalizable.