O&P Library > POI > 1997, Vol 21, Num 03 > pp. 168 - 174

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Optimisation of the prescription for trans-tibial (TT) amputees

A. Cortés *
E. Viosca *
J. V. Hoyos *
J. Prat *
J. Sanchez-Lacuesta *

Abstract

The great diversity of prosthetic mechanisms available nowadays leads to the question of which type of artificial foot would be the most advisable for a particular person. To answer correctly, it is necessary to establish, in an objective way, the performance of each type of prosthetic mechanism. This knowledge is obtained by means of the study of the subject-prosthesis interaction, both in static and dynamic conditions.

This paper, based on the analysis of 8 trans-tibial (TT) amputees, presents a quantitative method for the study of human gait which allows the determination of the influence of four different prosthetic ankle-foot mechanisms (SACH, Single-axis, Greissinger and Dynamic) on gait. To do this, 1341 gait trials at different cadences were analysed (383 with normal subjects and 958 with amputees, using the four prosthetic feet under study). From all the variables available for study only those which offered interpretable clinical information were chosen for analysis. A total of 18 variables (kinetic, klnematic and time-related) were selected. A covariance analysis (ANOVA) of these variables was made, which showed that the factors influencing TT amputee gait were, in order of importance, cadence and leg studied (sound or prosthetic), inter-individual variability and, finally, the prosthetic mechanism used. When looklng at the performance during gait of the 4 prosthetic mechanisms studied it can be observed that there are similarities in the kinetic study between SACH and Dynamic feet on one hand and Single-axis and Greissinger feet on the other. These results seem to support the classification criteria of articulated and non-articulated prosthetic mechanisms.

Introduction

Both the increasing demand for a better life standard on the part of the amputees, improving the functionality of gait and even taking part in sport activities, and the natural motivation of competitiveness on the part of the manufacturers are encouraging the orthopaedic industry to progress with the development of new prosthetic devices. Nowadays, the possibilities of selection (among prosthetic designs) are so many that an individual's needs can be partially satisfied by different means, which makes it difficult to select the ideal product. In general terms the basis for a correct orthopaedic prescription is suiting the features offered by a device to the user's functional needs. This demands, in the first place, a knowledge of the performance of the different prosthetic mechanisms, both in static conditions and during use; and, in the second place, it is also necessary to know the functional needs of the intended user.

Few scientific reports address the question of making comparative analyses of different prosthetic mechanisms, and those few merely compare some of their characteristics separately (Arya et al., 1995; Casilla et al, 1995; Ehara et al., 1993; Goh et al., 1984; Schneider, 1993; Wing and Hittenberger, 1989). Additionally, the parameters analysed during gait and the methods used to obtain them vary from author to author. As a consequence, the comparison of the results of different research works and, consequently, the comparison of the different prosthetic mechanisms, becomes very difficult, if not impossible. Furthermore, the objective evaluation of the functional needs of the subject to be fitted is a question still to be solved and, maybe, a more complex matter than it seems.

If only the gait function is considered it is known that it is conditioned by numerous factors (Hoyos, 1984; Viosca, 1993):

• Individual factors: age (Gabell and Nayak 1984; Sudarsky, 1990), sex (Bhambhani and Sing, 1985; Jansen et al., 1982; Zuniga and Leavitt, 1973) and interindividual variability (Mann, 1981; Menard et al, 1992).
• Dynamics of gait: velocity (Murray et al, 1984) or cadence (Ayora, 1990; Boonstra et al., 1993).
• Environmental: ground surface or shoe type Jones et al., 1986).
• Amputation: etiology (Pohjolainen et al., 1989; Sulzle et al., 1978), surgical procedure (Burgess and Moore, 1977; Murdoch, 1984; Steinbach et al., 1982), or amputation level (Sengler, 1984; Skinner and Effeney, 1985; Waters et al, 1976).
• Prosthesis: fitting (Meier et al., 1973; Mizrahi et al., 1985; Saxena and Mukhopadhyay, 1977), alignment (Pearson et al., 1973; Radcliffe, 1962) or prosthetic mechanism.

It can be seen then that the solution to the problem is complex and depends on many factors, It is thus necessary to come up with a common method for the analysis of prosthetic gait which, considering the above mentioned factors, allows for the comparison of the results drawn from different research teams, and therefore, for the comparison of different prosthetic mechanisms. This would mean an important saving of effort, while it would solve many of the problems posed.

The purpose of this work is to provide solutions to some of the drawbacks mentioned, To do this, the first aim is to present an objective and quantitative method for the study of prosthetic gait, which allows for the comparison of gait patterns. This will lead to the second objective, the comparison of the dynamic behaviour of 4 prosthetic ankle-foot mechanisms used by TT amputees, through the modifications introduced in the gait parameters. Although this does not mean solving the problem of assessing the amputees' functional needs, it will give objective data about the performance of the different mechanisms and therefore mean a first approach to the solution of the prosthetic prescription in clinical practice.

Methodology

The work has been developed following an accurate experimental procedure detailed below. In order not to confuse the variability due to the prostheses with that due to the individual nature and circumstances of the amputation or the amputee, the sample for the study was selected to be as homogeneous as possible so that the only source of variability was the prosthetic mechanism.

The gait analysis was carried out in a group of 8 TT amputees and 7 non-amputees. The amputees were fitted with patellar-tendon-

bearing (PTB) prostheses and they fulfilled the following requirements: male; age between 18 and 50; traumatic TT amputation at least two years prior to the experience; good shaped stump free from skin problems, suture defects or hypertrophic scars; not suffering from any concurrent illnesses and having a high or very high level of functional gait activity according to Day's scale (Day, 1981), The control group were 7 non-amputated subjects, in good health condition, with normal gait and anthropometric characteristics similar to those in the amputee group.

The data of the two groups are shown in Table 1 and Table 2.

Four prosthetic feet were studied, each representative of one of the families of articular devices most commonly used in the authors' hospitals (SACH, Single-axis, Greissinger and Dynamic). These feet were mounted on a copy of the amputee's prescribed prosthesis and were interchanged at random, allowing for a two-week adaption period before measurement.

All prostheses were made by the same manufacturer, to ensure similar criteria of manufacture, fitting and alignment thus avoiding variability derived from these factors. In all cases Oxford shoes with a 25mm heel were used. The experimental sessions were carried out at the Laboratory of Human Gait and Movement Analysis at the Institute of Biomechanics of Valencia (IBV). The equipment used was:

• 12m long walkway instrumented with two DINASCAN-IBV© extensometric force plates (Sánchez-Lacuesta et al., 1992).
• A system of polycentric electrogoniometry for the measurement of both limbs-hip, knee and ankle angles on the sagittal plane (Cortes et al, 1992).
• Telemetry equipment for the transmission of signals from the electrogoniometers.
• Data acquisition and control system which combines the signals from the platforms with those from the electrogoniometers and a PC with the appropriate software for data processing.

After a period of adaption to the laboratory conditions and the equipment used, and with the purpose of studying gait in a wide range of cadences, the subject was asked to walk at free cadence and, then, faster and slower until a spectrum of cadences ranging from 60 to 140 steps per minute was obtained. No metronome was used to measure cadence since it conditioned excessively the asymmetrical gait of the amputee. Instead, the period (T) which took them to walk five steps was timed in seconds and then calculated cadence (C) C = 5x (60/T), expressed in steps/min.

A total of 1341 trials of gait were made at different cadences, 958 of which corresponded to amputees and 383 to normal subjects. From all the variables which could be studied those selected for analysis were the ones that, in the authors' opinion, gave better clinical information on gait. A total of 18 variables was selected (Fig. 1 and Fig. 2); 7 were kinetic, 10 kinematic and 1 time-related (Single Support Stance Time SST). All of them are easy to interpret and were related to mechanical or physiological events in the gait cycle.

The data were processed using BMDP Statistical Software and a co-variance analysis was done with the 18 variables selected. Cadence was set as covariable and subject (NAME), limb considered - sound or prosthetic - (SP) and type of prosthetic mechanism used (FOOTTYPE) were set as factors. The analysis of the Snedecor's F magnitude allows the controlled factors to be sorted according to their relative importance on the variable analysed.

Whenever significant differences were found a multiple linear regression analysis was performed with the purpose of adjusting evolution patterns of the dependent variables analysed as a function of cadence for each limb considered and prosthetic mechanism used. Only those graphs with a significant coefficient R of multiple correlation (p < 0.01) were considered.

Results and discussion

The results of the ANOVA showed that cadence, subject (NAME), limb studied (SP) and type of prosthetic mechanism used (FOOTTYPE) have a significant (p < 0.05) or highly significant (p < 0.01) influence on most of the variables analysed (Cortés, 1993). As can be seen in [table3], the order of importance of the controlled factors with regard to the variables is, in the first place, cadence and limb studied (SP), in the second place, subject (NAME) and, in the last place, type of articular mechanism used (FOOTTYPE).

Consequently, the gait variables studied are greatly influenced by cadence. This suggests that gait trials should be performed in a wide range of cadences. Most of the experimental works reviewed (Doane and Holt, 1983; Enoka et al., 1982; Hoy et al., 1982; Winter and Sienko, 1988;) aim at the study of the influence of the type of prosthetic mechanism on gait although they neither consider cadence in a complete way nor the nature of the limb studied (sound or prosthetic). The results of this study show that these factors have greater influence on the dependent variables analysed than the type of articular mechanism used. This might explain the fact that the results published are not coincident.

Fig. 3 depicts the relationship between kinetic variables and cadence for each type of articular mechanism. It can be observed, generally speaking, that there are similarities in behaviour of SACH and Dynamic feet, on the one hand, and of Single-axis and Greissinger on the other. This refers both to the sound limb and the prosthetic one. Therefore, from a kinetic point of view, the results suggest that the most determinant factor related to the behaviour of prosthetic feet is the presence or absence of a joint which allows for plantar flexion.

Nevertheless, it is important to point out other particular items that are not under this general rule. Single-axis and Greissinger feet show a different behaviour with respect to variable FX1 (maximum fore-aft horizontal force at heel contact). This suggests that the Greissinger foot behaves as a non-articulated foot, with values for FX1 below those of the control subjects. This pattern of kinetic behaviour is kinetically supported by Enoka et al., (1982) who did not detect the expected plantar flexion corresponding to the design. On the contrary, horizontal force (FX1) in the artificial limb with the Single-axis mechanism is much higher than with the other prosthetic mechanisms, and even higher than for the control group. A possible explanation is that part of the energy used during gait causes the mechanism to extend (plantarflexion), which implies that it must pivot on/around the heel and means a greater braking force. Enoka et al. (1982) showed that this does not occur in the Greissinger foot, probably because a higher force is needed to perform plantarflexion, which in practice behaves as a non-articulated mechanism.

Conclusions

In summary, the general conclusions of the study are as follows:

• The method presented for the study of prosthetic gait seems to be appropriate because it is objective and quantitative, allowing comparison of the results obtained with different prostheses. It could be a valid proposal as a standard method for the study of prosthetic gait.
• The factors which influence the amputee's gait can be arranged according to the following order of importance: cadence and type of limb (sound or prosthetic): subject (which accounts for individual variability) and type of prosthetic mechanism used.
• Since these factors have a significant effect, they should be considered in the experimental design; otherwise, the conclusions attained can be confusing or mistaken.
• The results of this work show similarities between the kinetic behaviour of SACH and Dynamic feet on the one hand, and Single-axis and Greissinger on the other, This fact supports the criterion for the classification of prosthetic mechanisms as articulated and non-articulated.

Acknowledgments

The authors would like to thank Otto Bock Ibérica for supplying all prosthetic feet free of charge; Ortopedia Sotos SL for making and fitting the prostheses; Prof V. Carot (Polytechnic of Valencia UPV) for his help with statistical analysis and finally, all the subjects who generously participated in the experiment.

References:

1. Arya AP, Less A, Nirula HC, Klenerman L (1995). A biomechanical comparison of the SACH, Seattle and Jaipur feet using ground reaction forces. Prosthet Orthot Int 19, 37-45.
2. Ayora M (1990) Contribución al Análisis Paramétrico de la Marcha Humana Normal: Influencia de la Cadencia, Sexo, Edad and Morfología de la Huella Plantar. Thesis. Universidad Autónoma de Barcelona.
3. Bhambhani Y, Sing M (1985), Metabolic and cinematographic analysis of walking and running in men and women. Med Sci Sport Exerc 17, 131-137.
4. Boonstra AM, Fidler V, Eisma WH (1993). Walking speed of normal subjects and amputees: aspects of validity of gait analysis. Prosthet Orthot Int 17, 78-82.
5. Burgess EM, Moore AJ (1977). A study of interface pressures in the below-knee prosthesis (physiological suspension: an interim report). Bull Prosthet Res 10(28), 58-70
6. Casillas JM, Dulieu V, Cohen M, Marcer I, Didier JP (1995). Bioenergetic comparison of a new energy-storing foot and SACH foot in traumatic below-knee vascular amputations. Arch Phys Med Rehabil 76, 39-44.
7. Cortes A, Viosca E, Vera P, HoYos JV (1992). Técnicas biomecánicas de análisis de la marcha humana. Arch Med Deport 33, 27-31.
8. Cortés A (1993). Análisis biomecánico de distintos mecanismos de tobillo para amputados de miembro inferior por debajo de la rodilla. Thesis. Universidad de Valencia.
9. Day HJB (1981). The assessment and description of amputee activity. Prosthet Orthot Int 5, 23-28.
10. Doane Ne, Holt E (1983) A comparison of the SACH and single axis foot in the gait of unilateral below-knee amputees. Prosthet Orthot Int 7, 33-36
11. Ehara Y, Beppu M, Nomura S, Kunimi Y, Takahashi S (1993). Energy storing property of so called energy storing prosthetic feet. Arch Phys Med Rehabil 74, 68-72.
12. Enoka RM, Miller DI, Burgess EM (1982). Below-knee amputee running gait. Am J Phys Med 61, 66-84.
13. Gabell A, Nayak USL (1984). The effect of age on variability in gait. J Gerontol 39, 662-666.
14. Goh JCH, Solomonidis SE, Spence WD, Paul JP (1984). Biomechanical evaluation of SACH and uniaxial feet. Prosthet Orthot Int 8, 147-154.
15. Hoy MG, Whiting WC, Zernicke RF (1982). Stride kinematics and knee joint kinetics of child amputee gait. Arch Phys Med Rehabil 63, 74-82.
16. Hoyos JV (1984). Aportación al estudio de la marcha humana mediante el diseño y constructión de un sistema automatizado de análisis Thesis Universidad Politécnica de Valencia
17. Jansen EC, Vittas D, Hellberg S, Hansen J (1982). Normal gait of young and old men and women: ground reaction forces measurement on a treadmill. Acta Orthop Scand 53, 193-196.
18. Jones BH, Knapik J, Daniels WL, Toner MM (1986). The energy cost of women walking and running in shoes and boots. Ergonomics 29, 439-443.
19. Mann RW (1981). Cybernetic limb prosthesis. Ann Biomed Eng 9, 1-43.
20. Meier RH, Meeks ED, Herman RM (1973). Stump socket fit of below-knee prostheses: comparison of three methods of measurement. Arch Phys Med Rehabil 54, 553-558.
21. Menard MR, McBride ME, Sanderson DJ, Murray DD (1992). Comparative biomechanical analysis of energy-storing prosthetic feet. Arch Phys Med Rehabil 73,451-458.
22. Mizrahi J, Susak Z, Bahar A, Seliktar R, Najenson T (1985). Biomechanical evaluation of an adjustable patallar-tendon-bearing prosthesis. Scand J Rehabil Med (Suppl) No. 12, 117-123.
23. Murdoch G (1984). Amputation revisited. Prosthet Orthot Int 8,8-15
24. Murray MP, Mollinger LA, Gardner GM, Sepic SB (1984). Kinematic and EMG patterns during slow, free and fast walking. J Orthop Res 2, 272-28
25. Pearson JR, Holmgren G, March L, Oberg K (1973). Pressures in critical regions of the below-knee patellar-tendon-bearing prosthesis. Bull Prosthet Res 10 (19), 52-76.
26. Pohjolainen T, Alaranta H, Wikstrom J (1989). Primary survival and prosthetic fitting of lower limb amputees. Prosthet Orthot Int 13, 63-69.
27. Radcliffe CW (1962). The biomechanics of below-knee prostheses in normal, level, bipedal walking. Artificial Limbs 6(2), 16-24.
28. Sánchez-Lacuesta J, Comín M, Prat J, Soler-Gracia C, Dejoz R, Peris JL, Hoyos JV, Vera P (1992). New force plate design for the analysis of musculo-skeletal and neurological diseases: preliminary experience. In: European Symposium on Clinical Gait Analysis, Zürich.
29. Saxena SC, Mukhopadhyay P (1977). E.M.G. operated electronic artifical-leg controller. Med Biol Eng Comput 15, 553-557.
30. Schneider K, Hart T, Zernicke RF, Setoguchi Y, Oppenheim W (1993). Dynamics of below-knee amputee gait: SACH foot versus Flex-foot. J. Biomech 26, 1191-1204.
31. Sengler J (1984). Coût énergétique de la marche normale et prothétique (2a partie): revue de la literature. J Rédapt Méd 4,46-52
32. Skinner HB, Effeney DJ (1985). Gait analysis in amputees. Am J Phys Med 64, 82-89.
33. Steinbach TV, Nadvorna H, Arazi D (1982). A five year follow-up study of phantom limb pain in post traumatic amputees. Scand J Rehabil Med 14, 203-207.
34. Sudarsky L (1990). Geriatrics: gait disorders in the elderly. N Engl J Med 332, 1441-1446.
35. Sulzle H, Pagliarulo M, Rodgers M, Jordan C (1978). Energetics of amputee gait. Orthop Clin North Am 9, 358-362.
36. Viosca E (1993). Estudio biomecánico comparanvo entre el patron de marcha humana normal y del amputado tibial. Thesis. Universidad Politécnica de Valencia.
37. Waters RL, Perry J, Antonelli D, Hislop H (1976). Energy cost of walking of amputees: the influence of level of amputation. J Bone Joint Surg 58A, 42-46.
38. Wing DC and Hittenberger DA (1989). Energy-storing prosthetic feet. Arch Phys Med Rehabil 70, 330-335.
39. Winter DA, Sienko SE (1988). Biomechanics of below-knee amputee gait. J Biomech 21, 361-367.
40. Zuniga EN, Leavitt LA (1973). Quantified gait characteristics of women. Arch Phys Med Rehabil 54, 570-571.

O&P Library > POI > 1997, Vol 21, Num 03 > pp. 168 - 174