Biomechanical Alterations In The Gait of Unilateral Transtibial Amputee Patients: A Bibliographic Review

Rodrigo Gonçalves Barroso - rodrigobarroso8@hotmail.com

Master in Trauma-Orthopedic and Sports Physiotherapy

Instituto de Pós-Graduação - IPOG

Niterói, RJ, June 20, 2015

Summary

Transtibial amputation is defined as total or partial removal of the body segment that is located between the knee and ankle joint, and can be performed at 3 levels: proximal, middle, and distal. This study aimed to delineate the biomechanical alterations that affect the gait of patients who underwent a unilateral transtibial amputation, but who are protected to perform the ambulation. The present study used the bibliographic review method, through research in the databases: SCOPUS and PUBMED. After reviewing scientific studies after 1990, some results that hinder the efficiency and safety of gait in these patients were identified, such as: asymmetry, changes in the physiological gait cycle, adaptive gait strategies in regular and irregular terrain, loss of propulsion, and postural instability. These changes are related to a higher incidence of orthopedic lesions and falls in these patients, and therefore it is necessary a better understanding of these changes aiming at the development of more effective interventions in the future.

Keywords: transtibial amputation; biomechanical changes; gait.

Introduction

Amputation is defined as the usually surgical, total or partial removal of a limb. This practice is as old as the history of humanity itself (CARVALHO, 1999). One of the oldest archaeological pieces suggesting amputation was reported in Israel, and is estimated to be from the year 1600 B.C. (BLOOM et al, 1995).

The predominant cause of amputation is peripheral vascular disease, combined or not with diabetes (O'SULLIVAN; SCHMITZ, 1993). Vascular causes when added to infections represented more than 90% of the 60,000 amputations performed in the United States in the 1990s (RUTHERFORD, 1995). Although not all studies find results above the rate of 90% for the sum of these two variables as preponderant causes, the literature consistently presents these two causes as main, Agne et al (2004) reported that 67.5% of the cases of amputations had vascular or infectious causes at the Hospital Universitário de Santa Maria. However, there is a trend of lower rates of vascular causes of amputations in patients living in underdeveloped countries, while the rates of traumatic amputations tend to be higher in these countries (UNWIN, 2000). According to Maffei (1995 apud AGNE et al, 2004, p. 85) the risk factors for the onset of vascular diseases are: advanced age, smoking, diabetes, hypertension, and lipoproteinemia. In summary, the major causes of amputations are: vascular, infectious, traumatic, neoplastic, and congenital (CRISTIAN, 2005).

In the current context, of marked advances in the diversity and efficiency of prosthetization, the present study is justified through the need to understand biomechanical changes in patients amputated for a successful rehabilitation program, considering that there is an incidence rate of falls around 50% higher in the amputee population compared to non-amputees, each year (MILLER; DEATHE, 2004). Lower limbs amputations also disrupt motor and proprioceptive function at the site, leading amputees to rely heavily on visual return for orthostatic balance (VANICEK et al, 2009). The same happens in gait, where visual and somatosensory return are also paramount for this function (GANDEVIA, 2001). However, gait and orthostatic balance are two essentially different tasks (KANG; DINGWELL, 2006). In order for these individuals to incorporate functional activities into their day-to-day without the high risk of fall, they need to effectively position the center of gravity within the limits of their support base, this requirement defines the limits of stability. The stability limit represents the maximum inclination of the vertical position that these individuals can achieve, without using the balance strategy of the step forward or falling. If there are abnormalities of the somatosensory system or musculoskeletal system such as muscle weakness, and limitations of ankle range of motion, the stability limit will be reduced. (HORAK, 2006)

The components of the prostheses also play a fundamental role in the stability of these individuals, and the quality of the interface between the residual limb and the prosthesis, the soquee, reported as the most important aspect in any prosthesis (MARKS; MICHAEL, 2001). Regarding the components of the prostheses, there is a great concern with comfort, because patients point to this factor as being the main factor to adhere to the use of a given prosthesis (MILLER; DEATHE,2004). Another concern is in relation to impact absorption, as promoting good impact absorption is critical for any lower limb prosthesis. At each step, the forces are transmitted through the prosthesis to the residual limb, and to the proximal joints. Thus, an insufficient impact absorption is associated with pain and osteoarthrosis in the residual limb (KLUTE; KALLFELZ; CZERNIECKI, 2001). In addition, insufficient impact absorption is also related to increased low back pain in these patients (VOLOSHIN; WOSK, 1982, apud BOUTWELL et al, 2012, p. 228). Unilateral transtibial amputee patients present postural instability resulting from these biomechanical and neurophysiological changes, which leads to compensatory and adaptive mechanisms in both the static and dynamic aspects of balance. Furthermore, less effective postural control in transtibial amputee patients results in an increase in the demand of the healthy lower limb during orthostatic stance and gait (ISAKOV et al, 1992; JONES et al, 1997). A poor alignment of the prosthesis may also be a factor that leads to an increase in the demand of the healthy lower limb, besides being able to cause pressure changes in the prosthesis's system, and in the increase in gait asymmetry (ISAKOV et al, 1994). Postural instability, resulting from biomechanical changes, is a complicating factor of independence in the activities of daily living of these patients, so that the understanding of these alterations becomes paramount in the rehabilitation of transtibic amputees, considering that independence in the activities of daily life of amputees is a primary goal of physiatras, and physiotherapists (ISAKOV et al, 1992).

This study aims to investigate the literature after 1990, in order to delineate what are the most important biomechanical changes in gait of prosthetized unilateral transtibial amputee patients, in order to guide a better clinical practice of the areas of activity that depend on the biomechanical understanding of these patients.

Methodology

The study was developed through the analysis and interpretation of data obtained in bibliographic review research. The search for relevant publications in the scientific literature on this subject was carried out through the scopus and PUBMED databases. The search strategies were made by combining two distinct ways of keyword combinations. In the first combination, the following keywords were used: ''biomechanics'', 'amputation'', ''transtibial'', where 202 results were found with this first combination in the SCOPUS database, and 11 results in the PUBMED database. In a second search strategy, the following keywords were combined: '' amputation'', ''gait'', ''alteration'', where 24 results were found with this second combination in the SCOPUS database, and 2 results in the PUBMED database. It should also be noted that a search requirement is that the keywords searched should appear in the title or abstract of the work, an additional factor that helped refine the results. Only studies in Portuguese or English were included. Case studies, pilot studies and abstracts were excluded from this review, as well as excluding studies prior to 1990. The author selected at the end 33 scientific articles, after reading the abstracts, where he selected the most appropriate papers to support the theme proposed in the present study. In addition, 16 other articles were added later after reading the original 33 articles. This was due to the reference of works, which the author judged important for the theme, which had not been found in the initial search. There was also the consultation of three books for the accomplishment of this work. The books were consulted in the libraries of the Institute of Chest Diseases at the Hospital Universitário Clementino Fraga Filho, and in the Central Library of the Center for Health Sciences, both libraries belonging to the Universidade Federal do Rio de Janeiro.

Gait Changes in Unilateral Transtibial Amputee Patients

3.1. Gait characteristics

Preliminary, it is necessary to establish what characterizes the gait of a healthy subject, therefore it should be mentioned that these healthy individuals present a high level of symmetry for each variable analyzed in their gait, to mention those with the highest level of symmetry: step length, time of the support period, and time of the double support phase. However, there is no perfect symmetry even in healthy patients, since an approximate mean of 4% asymmetry was found when 12 different variables for gait of healthy subjects were evaluated (HERZOG et al, 1989 apud DINGWELL; Davis; FRAZIER, 1996, p. 102; ESQUENAZI; TALATY, 2007). Therefore, there are subtle values of asymmetry that are present even in the gait of normal subjects. However, the intensity of this asymmetry is different for each variable analyzed in gait, besides being a much lower asymmetry value than those found in the gait of transtibial amputee patients (DINGWELL; Davis; FRAZIER, 1996). The proportion of phases of a gait cycle is another factor that characterizes the gait of a healthy subject. The gait cycle is a cyclic pattern of motion that is repeated. The support period is divided into 5 phases: initial contact, load response, medium support, final support, and pre-balance. In addition, this period is also divided into 3 other phases that take into account the contralateral limb, and they are: double initial support, single support, and double terminal support. Each double support phase represents 10% of the gait cycle, while the single support phase represents 40% of this cycle, so the support period represents 60% of the total gait cycle (note that all these percentages are approximate values). Finally, the balance period represents the moment when there is no contact of the limb with the ground, and lasts exactly the same time in which the simple support occurs in the contralateral limb during the gait cycle, and therefore 40% of this cycle. This balance period is divided into 3 phases: initial balance sheet, average balance, and terminal balance. The duration of a stride is understood as the interval between an initial contact and the next ipsilateral initial contact. The step is recognized as the interval between sequential initial contacts with the soil, considering the initial contact of both the analyzed ipsilateral limb and the contralateral limb. Two steps characterize a stride (a complete gait cycle), steps that are practically symmetrical in normal individuals. The concept of gait cadence is characterized by a number of steps or passed per unit of time. The step length is the projected distance from the initial contact with the soil in sequence, considering the initial contact of both the analyzed ipsilateral limb and that of the contralateral limb, while the stride length is the projected distance between an initial contact until the next sequential initial contact of the same analyzed limb (ESQUENAZI; TALATY, 2007).

There is also a higher gait speed in healthy patients when compared with patients amputated in unilateral lower limbs (BOONSTRA; FIDLER,EISMA, 1993; KOVAC; MEDVED; OSTOVIC, 2010), combined with an efficiency in energy consumption, because the scientific literature demonstrates lower heart rate and oxygen consumption values in the gait of healthy subjects, which demonstrates a biomechanical efficiency in their gait that is not only reflected in speed and symmetry, but also in their energy efficiency (HUNTER et al, 1995).

3.2. Changes in the gait cycle

That said, the gait cycle characteristics of transtibial amputated patients should be elucidated. Two studies reviewed in this study evaluated the spatial and time characteristics of gait kinematics in unilateral transtibial amputated patients when compared with those of normal subjects, as well as also evaluated the gait characteristics of the amputated lower limb in relation to the contralateral healthy lower limb of the same patient. The results were similar for these two studies, where the duration of the reduced support phase, the increased duration of the balance phase, and the reduced speed in the balance, and all these changes occur in the amputated limb in relation to the positive healthy limb of the same patient. The stride length was the only variable where an antagonistic result was found between the two studies, in the time-spatial analysis of the gait of these patients. (ISAKOV et al, 2000; KOVAC; MEDVED; OSTOVIC, 2010)

The same results are found when these variables are compared between the amputated limb of a patient, with the ipsilateral healthy limb of another subject in a control group, therefore they are found in the amputated limb: reduced duration of the support phase, increased duration of the swing phase, and reduced speed in the balance. The reason for a reduced support phase duration lies in the fact that there is a lower confidence of the amputated patient in the prosthetized limb, and that therefore these patients seek to transfer the discharge of their body weight to the healthy limb as soon as possible (KOVAC; MEDVED; OSTOVIC, 2010). Another important fact is that the asymmetry between the limb is and the amputated limb is not increased as there is an increase in the gait speed of these patients, when the time-spatial variables of gait (ISAKOV et al, 1996) are evaluated; ASTRÖM; STENSTRÖM, 2004). However, some studies show that gait speed, cadence, and stride length are statistically significantly higher in transtibial amputee patients due to traumatic causes than those amputated by vascular causes (HUANG et al, 2000; ASTRÖM; STENSTRÖM, 2004).

3.3. The absorption of impact on the gait of the transtibial amputee

Impact absorption is ordered during the response phase to the gait load. And the promotion of this absorption is a vital concern in relation to lower limb prostheses. At each step, the forces are transmitted through the prosthesis to the residual limb and proximal joints. Therefore, insufficient impact attenuation is related to low back pain (VOLOSHIN; WOSK, 1982, apud BOUTWELL et al, 2012, p. 228), osteoarthrosis, and increased pain in the residual limb (KLUTE; KALLFELZ; CZERNIECKI, 2001). Impact absorption is related to mechanisms in accordance with the locomotor system. Anatomical quilting of the calcaneus and ankle plantiflexion are two mechanisms of impact absorption of healthy subjects, who are not present after a transtibial amputation. It should also be added that knee flexion in the balance phase and pelvic obliqueness are two other mechanisms that promote substantial impact absorption during gait of healthy subjects (GARD; CHILDRESS, 1999). Although transtibial amputee patients are able to use these latter two mechanisms, the intensity of these mechanisms is reduced, in addition to the fact that movement patterns are frequently altered in relation to the gait of healthy subjects (MICHAUD et al,2000), which suggests a reduction in the ability to absorb impact in transtibial amputee patients. However, in these patients, the congruence between the residual limb and the interface of the prosthesis's system probably still promotes a degree of impact absorption. However, this absorption does not seem to be sufficient to compensate for the loss of physiological mechanisms of impact absorption (BOUTWELL et al, 2012).

3.4. The absence of the foot and ankle

Unilateral transtibial amputee patients have as main characteristics the loss of the foot and ankle joint, and therefore these characteristics become the greatest challenge for the rehabilitation of these patients, since there is not yet a prosthesis capable of perfectly emulate the properties of the foot and ankle (SMITH, 2003). The loss of gait propulsion due to the absence of plantiflexor muscles is one of the most considerable problems in transtibial amputees, as it is even reported that this variable is correlated with the energy inefficiency of gait (HUNTER et al, 1995). However, this is not the absence that most worries health professionals, because the loss of foot architecture combined with sense loss are more difficult problems to be emulated in prostheses, and have more serious repercussions, such as: increased impact, pain, and osteoarthrosis in the healthy contralateral knee (KLUTE et al, 2001), low back pain (VOLOSHIN; WOSK, 1982, apud BOUTWELL et al, 2012, p. 228), and difficulty in balancing and adapting to different types of soils (GOUJON et al, 2006). The foot does not remain unchanged throughout the gait cycle, it adjusts and adapts according to the cycle phase. During the rocking phase the foot becomes more malleable and adapts to the soil in which it is located. As the foot begins the initial contact phase and response to the load, it contributes to the absorption of the impact (due to its initial malleability), and becomes more rigid and stable as the weight discharge progresses on it. This stiffness and final stability is necessary for better propulsion in the final stages of support (CRISTIAN,2005).

Some studies even demonstrate that the artificial foot is the main cause of transtibial amputee patients needing asymmetry in gait, in order to have compensation capable of producing a more efficient prosthetized gait (ISAKOV et al, 1997; KLUTE et al, 2001). Therefore, the challenge of the manufacture of prostheses today lies in the attempt to emulate these characteristics of the foot that are modified during the gait cycle. Currently, foot prostheses can be created that are stiffer to improve propulsion, or softer to improve impact absorption, but not both in the same prosthesis (SMITH, 2003).

3.5. Adaptive strategies

It is suggested that the torque of the plantiflexion exerted on the ankle at the end of the support phase is the most efficient way to produce an increase in the translation force in the hip joint during the balance phase (ARMAND et al, 1996, apud HILL, 1999, p.546). However, it is natural for adaptive strategies to occur in the kinetics and kinematics of gait due to the changes suffered by a transtibial amputee patient. Therefore, it was verified that, as adaptation, the preserved musculature of the hip and knee joint allows rotational work in the hip joint for the elevation of the lower limb, at the beginning of the gait swing phase, even if this happens with a lower efficiency than would occur with the foot and ankle joint intact, and therefore what is usually called propulsion is lost (HILL et al , 1997).

Some changes occur when transtibial amputee patients are submitted to gait on uneven terrain, citing the tendency to use shorter but wider steps so that they can increase the support base to obtain a higher limit of mediolateral stability (GATES et al, 2012), in addition to the fact that they further reduce the speed when crossing an unstable terrain (LAMOTH et al , 2010). However, despite this more careful gait, they still have a higher risk of fall when walking on rough terrain compared to healthy subjects (MILLER; SPEECHLEY; DEATHE, 2001).

Another remarkable adaptive strategy is presented on the descent of steps on a staircase, where transtibial amputee patients descend with the lower limb prosthetized with complete extension of the knee and hip, it is reported that this adaptation ensures a vector of the ground reaction force passing before the knee joint. It should be added that this strategy is carried out to decrease the torque required in the knee extensors to ensure the descent on a step (JONES et al, 2006).

3.6. In relation to the prosthesis steeds

Transtibial amputated patients may present with a gait limitation due to an undue fitting with the prosthesis socket, which usually progresses with a poor distribution of pressure in the socket, shear forces (ZHANG; ROBERTS, 2000), torque force, and frictions between the skin and prosthesis liner (SANDERS et al,2000). Skin problems such as allergic contact dermatitis, follicular hyperkeratosis, and infections are common (LYON et al, 2000). In addition to bony prominences, fluctuations in stump volume, and pain are also on the list of problems. However, patients who have been amputated due to vascular causes are especially vulnerable to these changes, as are diabetic patients with polyneuropathy (LEVY, 1995). Zhang & Roberts (2000) identified a considerable movement as well as the stress of the shear force that occurs between the residual limb and the prosthesis liner. And other studies were conducted in order to achieve a clinical method and objective of producing a system capable of fitting properly (SEWELL et al, 2000).

In order to avoid all these problems in the skin of the residual limb, a high-quality liner is necessary (SEWELL et al, 2000). A silicone liner is able to reduce friction between the skin and the liner, and is therefore able to increase comfort during the gait and rest of these patients, however it may still be able to produce torque force on the stump (CLUITMANS et al, 1994). However, the polyurethane liner seems to be almost unanimous among patients in relation to the material pointed out as the most comfortable to use in the interface with the prosthesis (HATFIELD; MORRISON, 2001; ASTRÖM; STENSTRÖM, 2004). Liners can also serve as a means of restoring impact absorption during gait. They are recognized as an important factor in changing the pressure distribution in the socket (FERGASON; SMITH, 1999). The liner used (usually silicone or polyurethane) increases congruence at the stump interface with the prosthesis's system, reducing focal peak pressures, and therefore provides a more uniform distribution of pressure in the residual limb. However, discomfort in the prosthesis's system can also be caused by excessive sweating at the site, and rashes. Both were associated with the use of liners (HATFIELD; MORRISON, 2001). The greater the thickness of the liner, the greater the increase in temperature at the interface of the prosthesis with the stump, which increases the incidence of sweating and the skin irritations associated with it. Therefore, a balance should be struck between increased comfort due to reduced transmission of peak pressure and the potential increase in the incidence of skin irritations. However, when compared to a 9mm liner with a thinner 3mm liner, a lower peak pressure was noted over the fibula head in all patients who used a thicker 9mm liner. In addition, patients report greater comfort when using the liner with a thickness of 9mm, compared to its 3mm version (BOUTWELL et al, 2012).

3.7. The relationship with the alignment of the prosthesis

The alignment of a transtibial prosthesis is verified through the three-dimensional orientation of the system in relation to the prosthetic foot, and is an important factor for the gait quality of these patients. A poorly aligned prosthesis affects the gait pattern in these patients (SANDERS et al, 1993; ROSSI et al, 1995), and may result in an abrasion or irritation at the interface between the stump and socket (CHOW et al, 2006), gait instability (PINZUR et al, 1995), and a compensatory muscle activity that results in an increase in energy consumption during gait (SCHMALZ et al, 2002).

There is still a lack of an objective way to prescribe an adequate alignment, because it is currently dependent on the judgment of health professionals, concomitantly with the perception of the amputee patient, so that an adequate alignment can be reached in the prosthesis (ZAHEDI et al, 1986 apud BOONE et al, 2012, p.620). However, the judgment of health professionals may not be a reliable way for the alignment of the prosthesis, because it has already been demonstrated that these professionals accept a variation between -5º to 13º in an angulation in the sagittal plane, and between -15mm up to 35mm for a previous translation (SIN et al, 2001).

Conclusion

The present study points out some of the biomechanical alterations that occur after a unilateral transtibial amputation, which are described in the scientific literature. However, it was not possible to find the role of each of these variables in the relationship with the higher incidence of falls in these patients, as well as it is not possible to affirm whether all biomechanical alterations were covered, due to limitations in the methodology of this study. New, more comprehensive, high-rigor methodological studies are needed to achieve the goal of guiding better clinical practice in unilateral transtibial amputee patients.

References

AGNE, J. E.; CASSOL, C. M.; BATAGLION, D.; FERREIRA, F. V. Identificação das causas de amputações de membros no Hospital Universitário de Santa Maria. Saúde, Rio Grande do Sul, v. 30, n.1-2,p. 84-89, 2004

ARMAND, M., PATLA, A.E., HUISSON, J.P. Modeling of the human swing leg during locomotion. In: Biennial Conference of the Canadian Society for Biomechanics, 9, 1996. Vancouver, Canada. Anais… Vancouver, Simon Fraser University, 1996.

ASTRÖM, I., STENSTRÖM, A., Effect on gait and socket comfort in unilateral trans-tibia1 amputees after exchange to a polyurethane concept. Prosthetics and Orthotics International, v. 28, p. 28-36, 2004.

BLOOM, A. I., BLOOM, R. A., KAHILA, G., EISENBERG, E., SMITH P., Amputation of the hand in the 3600-year-old skeletal remains of an adult male: The first case reported from Israel. International Journal of Osteoarchaeology, v. 5, p. 188–191, 1995.

BOONE, D.A., KOBAYASHI, T., CHOU, T.G., ARABIAN A.K., COLEMAN, K.L., ORENDURFF, M.S., ZHANG M., Influence of malalignment on socket reaction moments during gait in amputees with transtibial prostheses. Gait and Posture, v.37, p.620-626, 2012.

BOONSTRA, A.M., FIDLER, V., EISMA, W.H., Walking speed of normal subjects and amputees: aspects of validity of gait analysis. Prosthetics and Orthotics International, v.17, p.78-82, 1993.

BOUTWELL, E., STINE, R., HANSEN, A., TUCKER, K, GARD, S., Effect of gel liner thickness on gait biomechanics and pressure distribution within the transtibial socket. Journal of Rehabilitation Research & Development, v. 49, n.2, p.227-240, 2012.

CARVALHO, J.A. Amputações em membros inferiores: em busca de plena reabilitação. São Paulo: Manole, 1999.

CHOW, D.H.K., HOLMES, A.D., LEE, C.K.L., SIN, S.W., The effect of prosthesis alignment on the symmetry of gait in subjects with unilateral transtibial amputation. Prosthetics and Orthotics International, v.30, n.2, p.114-128, 2006.

CLUITMANS, J., GEBOERS, M., DECKERS, J., RINGS, F., Experiences with respect to the ICEROSS system for trans-tibial prostheses. Prosthetics and Orthotics International, v. 18, p. 78-83, 1994.

CRISTIAN, A. Lower Limb Amputation: A Guide to Living a Quality Life. 1º edição. Nova Iorque: Demos Medical Pub. p.7, 2005.

DINGWELL, J.B., DAVIS, B.L., FRAZIER, D.M., Use of an instrumented treadmill for real-time gait symmetry evaluation and feedback in normal and trans-tibial amputees subjects. Prosthetics and Orthotics International, v.20, p. 101–110, 1996.

ESQUENAZI, A., TALATY, M., Gait analysis: Technology and Clinical Applications. Physical medicine and Rehabilitation. 3º Edição. Londres: Saunders Elsevier, 2007.

FERGASON, J., SMITH, D.G., Socket considerations for the patient with a transtibial amputation. Clinical Orthopaedic and Related Research, v.361, p. 76-84, 1999.

GANDEVIA, S.C., Spinal and supraspinal factors in human muscle fatigue. Physiological Reviews v.81, n.4, p. 1725–1789, 2001.

GARD, S.A., CHILDRESS, D.S., The influence of stance-phase knee flexion on the vertical displacement of the trunk during normal walking. Archives of Physical Medicine and Rehabilitation, v.80, n.1, p.26-32, 1999.

GATES, D.H., SCOTT, S.J., WILKEN J.M., DINGWELL J.B., Frontal plane dynanic margins of stability in individuals with and without transtibial amputation walking on a loose rock surface. Gait Posture, v. 38, n.4, p.570-575, 2013.

GOUJON, H., BONNET, X., SAUTREUIL, P., MAURISSET, M., DARMON, L., FODE, P., & LAVASTE F., A functional evaluation of prosthetic foot kinematics during lower-limb amputee gait. Prosthetics and Orthotics International, v. 30, n.2, p.213-223, 2006.

HATFIELD, A.G., MORRISON, J.D., Polyurethane gel liner usage in the Oxford Prosthetic Service. Prosthetics and Orthotics International, v. 25, p.41-46, 2001.

HERZOG, W., NIGG, B.M., READ, L.J., OLSSON, E., Asymmetries in ground reaction force patterns in normal human gait. Medicine & Science in Sports & Exercise, v. 21, p.110-114, 1989.

HILL, S.W., PATLA, A.E., ISHAC, M.G., ADKIN, A.L., SUPAN, T.J., BARTH, D.G., Altered kinetic strategy for the control of swing limb elevation over obstacles in unilateral below-knee amputee gait. Journal of Biomechanics, v.32, p. 545-549, 1999.

HILL, S.W., PATLA, A.E., ISHAC, M.G., ADKIN, A.L., SUPAN, T.J., BARTH, D.G., Kinematic patterns of participants with a below knee prosthesis stepping over obstacles of various heights during locomotion. Gait and Posture, v.6, p. 186-192, 1997.

HORAK, F.B., Postural orientation and equilibrium: what do we need to know about neural control of balance to prevent falls? Age and Ageing, v.35, n.2, p. 7-11, 2006.

HUANG, G.F., CHOU, Y.L., SU, F.C., Gait analysis and energy consumption of below-knee amputees wearing three different prosthetic feet. Gait & Posture, v.12, p.162- 168, 2000.

HUNTER, D., COLE, E.S., MURRAY, J.M., MURRAY, T.D., Energy expenditure of below-knee amputees during harness-supported treadmill ambulation. Journal of Orthopaedic & Sports Physical Therapy. v.21, n. 5, 1995.

ISAKOV, E., MIZRAHI, J., RING, H.,SUSAK, Z., HAKIM, N.,  Standing sway and weight-bearing distribution in people with below-knee amputations. Archives of Physical Medicine and Rehabilitation, v. 73, p. 174-178, 1992.

ISAKOV, E., MIZRAHI, J., SUSAK, Z., ONA, I., HAKIM, N., Influence of prosthesis alignment on the standing balance of below-knee amputees. Clinical Biomechanics, v. 9, p. 258-262, 1994.

ISAKOV, E., BURGER, H., KRAJNIK, J., GREGORIC, M., MARINCEK, C., Influence of speed on gait parameters and on symmetry in trans-tibial amputees. Prosthetics and Orthotics International, v.20, p.153-158, 1996.

ISAKOV, E., BURGER, H., KRAJNIK, J., GREGORIC, M., MARINCECK, C., Double-limb support and step- length asymmetry in below-knee amputees. Scandinavian Journal of Rehabilitation Medicine, v. 29, p.75-79, 1997.

ISAKOV, E., KEREN, O., BENJUYA, N., Trans-tibial amputee gait: time-distance parameters and EMG activity. Prosthetics and Orthotics International, v.24, p. 216-220, 2000.

JONES, M.E., STEEL, J.R., BASHFORD, G.M., DAVIDSON, I.R., Static versus dynamic prosthetic weight bearing in elderly trans-tibial amputees. Prosthetics and Orthotics International, v. 21, p.100-106, 1997.

JONES, S.F., TWIGG, P.C., SCALLY, A.J., BUCKLEY, J.G., The mechanics of landing when stepping down in unilateral lower-limb amputees. Clinical Biomechanics, v.21, p. 184-193, 2006.

KANG, H.G., DINGWELL, J.B., A direct comparison of local dynamic stability during standing and walking. Experimental Brain Research, v.172, n.1, p. 35–48, 2006.

KLUTE, G.K., KALLFELZ, C.F., CZERNIECKI, J.M., Mechanical properties of prosthetic limbs: Adapting to the patient.  Journal of Rehabilitation Research & Development, v.38, n.3, p.299-307, 2001.

KOVAC, I., MEDVED, V., OSTOJIC, L., Spatial, temporal and kinematic characteristics of traumatic transtibial amputees gait. Collegium Antropologicum, v. 34, p. 205-213, 2010.

LAMOTH, C.J.C., AINSWORTH, E., POLOMSKI, W., HOUDIJK, H., Variability and stability analysis of walking of transfemoral amputees. Medical engineering & physics, v.32, n. 9, p. 1009-1014, 2010.

LEVY, S.W., Amputees: skin problems and prostheses. Cutis v. 55,p. 297-301, 1995.

LYON, C.C, KULKARNI, J., ZlMERSON, E., VAN ROSS, E., BECK, M.H., Skin disorders in amputees. Journal of the American Academy of Dermatology, v.42,p. 501-507, 2000.

MAFFEI, F. H. A. Doenças Vasculares. 2 .ed. Rio de Janeiro: Medsi, 1995

MARKS, L.J., MICHAEL, J.W., Science, medicine, and the future: Artificial limbs. British Medical Journal, v.323, n.7315, p. 732-735, 2001.

MICHAUD, S.B., GARD, S.A., CHILDRESS, D.S., A preliminary investigation of pelvic obliquity patterns during gait in persons with transtibial and transfemoral amputation. Journal of Rehabilitation Research and Development, v.37, n.1, p.1-10, 2000.

MILLER, W.C., DEATHE, A.B., A prospective study examining balance confidence among individuals with lower limb amputation. Disability and Rehabilitation v. 26, n.14–15, p. 875–881, 2004.

MILLER, W.C., SPEECHLEY, M., DEATHE B., The prevalence and risk factors of falling and fear of falling among lower extremity amputees. Archives of Physical Medicine and Rehabilitation, v.82, n. 8, p. 1031-1037, 2001.

O´SULLIVAN, S.B., SCHMITZ, T.J., Fisioterapia: Avaliação, Tratamento. 2. ed. São Paulo: Manole, 1993.

PINZUR, M.S., COX, W., KAISER, J., MORRIS, T., PATWARDHAN, A., VRBOS, L., The effect of prosthetic alignment on relative limb loading in persons with trans-tibial amputation: a preliminary report. Journal of Rehabilitation Research and Development, v.32, p.373–377, 1995.

ROSSI, S.A., DOYLE, W., SKINNER, H.B., Gait initiation of persons with below-knee amputation: The characterization and comparison of force profiles. Journal of Rehabilitation Research and Development, v.32, p.120–127, 1995.

RUTHERFORD, R.B., Vascular Surgery. v. 2, 4 ed. Philadelphia: W. B. Saunders Company, 1995.

SANDERS, J.E., DALY, C.H., BURGESS, E.M, Clinical measurement of normal and shear stresses on a trans-tibial stump: Characteristics of wave-form shapes during walking. Prosthetics and Orthotics International, v.17, p.38–48, 1993.

SANDERS, J.E., GREVE, J.M., CLINTON, C., HAFNER, B.J., Changes in interface pressure and stump shape over time: preliminary results from a trans-tibial amputee subject. Prosthetics and Orthotics International, v. 24, p. 163-168, 2000.

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 and Posture, v.16, p.255-263, 2002.

SEWELL, P., NOROOZI, S., VINNEY, J., ANDREWS, S., Developments in trans-tibial prosthetic socket fitting process: a review of past and present research. Prosthetics and Orthotics International, v. 24,p. 97-107, 2000.

SMITH, D.G., Transtibial amputation: successes and challenges.[Editorial]. In motion magazine, v. 13, n.4, jul./ago., 2003.

UNWIN, N. Epidemiology of lower extremity amputation in centres in Europe, North America and East Asia. British Journal Surgery, v. 87, p .328–337, 2000.

VANICEK, N., STRIKE, S., MCNAUGHTON, L., POLMAN, R., Postural responses to dynamic perturbations in amputee fallers versus non-fallers: a comparative study with able-bodied subjects. Archives of Physical Medicine and Rehabilitation. v. 90, p. 1018–1025, 2009.

VOLOSHIN, A., WOSK, J., An in vivo study of low back pain and shock absorption in the human locomotor system. Journal of Biomechanics, v. 15, p. 21-27, 1982.

ZAHEDI, M.S., SPENCE, W.D., SOLOMONIDIS, S.E., PAUL, J.P., Alignment of lower-limb prostheses. Journal of Rehabilitation Research and Development, v. 23, p. 2-19, 1986.

ZHANG, M., ROBERTS, C., Comparison of computational analysis with clinical measurement of stresses on below-knee residual limb in a prosthetic socket. Medical Engineering & Physics, v. 22, p. 607-612, 2000.