Bioenergetic Comparison of a New Energy-Storing Foot and SACH Foot in Traumatic Below-Knee Vascular Amputations

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1 39 Bioenergetic Comparison of a New Energy-Storing Foot and in Traumatic Below-Knee Vascular Amputations Jean-Marie Casillas, MD, V~ronique Dulieu, MD, Martine Cohen, MD, Inks Marcer, MSc, Jean-Pierre Didier, MD ABSTRACT. Casillas J-M, Dulieu V, Cohen M, Marcer I, Didier J-P. Bioenergetic comparison of a new energystoring foot and SACH foot in patients with traumatic below-knee vascular amputations. Arch Phys Med Rehabil 1995;76: In this study, the metabolic performances of a new energy-storing foot (Proteor) and of the solid-ankle cushion heel (SACH) are compared. Twelve patients with traumatic below-knee amputations (mean age: _ 19.9 years) and 12 patients with vascular below-knee amputations (mean age: 73 ± 7 years) were studied. Oxygen uptake (VOz) was measured in all the subjects on a walkway at a self-selected velocity; only the subjects with traumatic amputation were tested on a level treadmill (progressive speed: and 6 km/h), and then in two randomized trials: incline (+5%) and decline walking treadmill test at 4 km/h. Vascular explorations were done in the vascular patients: distal pressure measurements, pulse plethysmography, transcutaneous oxygen tension. Free walking was improved in subjects with traumatic amputation using the energy-storing foot (+6%), with a better bioenergetic efficiency (0.24 _+ 0.4mL/kg.m vs 0.22 _+ 0.04mL/kg-m). However, in subjects with vascular amputation, this foot did not produce an increased free velocity nor an improved energy cost. During the level treadmill test, the traumatic amputee subjects showed a decrease of energy expenditure with the new prosthetic foot, more significant at sufficient speed (4 km/h): ± 3.42 vs ± 2.05 ml/kg/min (p <.05). The same effect is shown during the incline (19.31 ± 2.80 vs ± 2.32mL/kg/min--p <.02) and decline walking tests (14.13 ± 3.64 vs ± 1.54mL/kg/minnp <.02). There is no significant difference in cardiocirculatory effects between the two types of prosthetic foot. Despite a lower velocity, the subjects with vascular amputation exceed 70% of the maximal heart rate, with the cardiocirculatory factor being the main cause of walking restriction. The energy-storing foot should be reserved for active and fast walkers, whereas the SACH foot seems more suitable for elderly patients with amputation with a slow walk by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation In recent years, numerous technical advances in the field of medical devices have improved the mechanical quality and comfort of walking after below-knee amputation. However, such innovations must be evaluated objectively, particularly from the biomechanical and bioenergetic points of view. In this latter respect, differences in terms of energy expenditure between above- and below-knee amputation are well known, t'2 and the preservation of the knee emerges as a determining factor in the functional prognosis. It is, moreover, essential to distinguish between the traumatic and vascular origins of a major below-knee amputation; it would seem that the bioenergetic possibilities of the patient with vascular amputation are more restricted. 3 It is instructive to determine correlations between mechanical and energetic modifications but such correlations are difficult to establish because there are specific problems attached to below-knee amputation: the loss of propulsive function devolving on the From the Service de r66ducation Fonctionnelle, Centre Hospitalier Universitaire de Dijon, Cedex, France. Submitted for publication April 7, Accepted in revised form July 26, This research supported by the "Institut National Scientifique des Etudes et de la Recherche M6dicale (Contract No )". No commercial party having a direct financial interest in the results of the research supporting this article has or will confer a benefit upon the authors or upon any organizations with which the authors are associated. Reprint requests to Jean-Marie Casitlas, MD, Service de r66ducation Fonctionnelle, Centre Hospitalier Universitaire de Dijon, 23, rue Gaffarel, Dijon, Cedex, France by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation /95/ /0 ankle plantarflexors must be offset either by modifying the involvement of the supra-jacent articulations or by technical adjustments to the equipment--or by a combination of these two factors. A prosthesis restoring a dynamic propulsion function would constitute a decisive step forward, and in this respect the advent of so-called energy-storing feet in recent years is of great interest, although it must be said that objective evaluations of this type of foot have been performed only rarely and a posteriori. In this study we propose to undertake an appreciation, based on bioenergetic parameters, of a new foot belonging to the energy-storing range of feet (Proteor foot) by comparing it with the SACH foot (Solid Ankle Cushion Heel) in different walking situations, in two groups of patients with unilateral below-knee amputations, one of traumatic and the other of vascular origin. Population METHODS Group 1, patients with traumatic amputation. The inclusion criteria were: unilateral below-knee traumatic amputation, performed more than 2 years previously, with socket contact and a SACH foot. The exclusion criteria were: an associated handicap that might restrict walking ability; the need to use technical aids (walking sticks) even on an occasional basis; difficulty in treadmill walking resulting from parasitic contractions and balance disorders; stump problems that might hinder successful prosthesis fitting and lead to painful phenomena; intercurrent medical problems liable to

2 40 EVALUATION OF A NEW ENERGY-STORING FOOT, Casillas Table 1: Characteristics of 12 Men With Traumatic Amputation and 12 Patients With Vascular Amputation (10 men, 2 women) Age x Weight x Height Time (yrs) (kg) (em) Postamputation Traumatic 50.0 _ _ _ _+ 14yrs Vascular 73 _ _ _ _+ 4.2mos modify respiratory gaseous exchanges; and addiction to tobacco. Group 2, patients with vascular amputation. The inclusion criteria were: unilateral below-knee amputation caused by lower-limb arteriopathy at the definitive prosthesis-fitting phase; with a socket contact and a SACH foot. The exclusion criteria were: peripheral or central neurological disease affecting walking; lower-limb articular or pre-articular damage liable to cause walk-restricting pains; balance disorders; stump problems that might hinder successful prosthesis fitting and lead to painful phenomena; addiction to tobacco; and arterial claudication of the nonamputated limb. Table 1 presents the characteristics of subjects in the two groups. All subjects had a properly adjusted endoskeleton prosthesis with a supracondylar-type socket, without associated solidarization system, and fitted with a SACH foot. Three of the traumatic amputee subjects were sedentary and 9 regularly participated in some sport. Protocol The protocol for Group 1: Walking was evaluated for each subject in two sessions, one with the SACH foot and one with the prototype foot. Subjects were requested to only use the foot to be tested in the week preceding evaluation and to not change their routine. During each session, walking bioenergetics was measured in three random-order situations: Phase A: rest in seated position (20min), walking at self-selected velocity (comfortable speed) on flat indoor prepared surface (8min); rest in seated position (15min); 2.4kph walk on level treadmill (3min); followed by 4kph walk (3rain) and 6kph walk for the last 3 minutes (if tolerated by the patient). Phase B: rest in seated position (20min); 4kph walk on treadmill with an incline of +5% (5min); rest (5min); 4kph walk on treadmill with a decline of 5% (5rain). Phase C: (Phase B in reverse order): rest in seated position (20rain); 4kph walk on treadmill with a decline of 5% (5min); rest (5rain); 4 kph walk on treadmill with an incline of +5% (5min). During the test at self-selected speed, oxygen consumption was measured by open-circuit indirect calorimetry with expired gas collected in a Douglas bag from the 6th to the 8th minute of walking. The subject was equipped with a Hans Rudolph" valve mask fitted with a flow counter for direct measuring of expiratory flow. Oxygen consumption had been previously measured during the rest phase. Cardiac activity was monitored by telemetry (MV5 derivation, Life Scope 6 b telemeter); blood pressure was measured by sphygmomanometry before and after the walking phase, and automatically (MarquettC blood pressure monitor, model 1950) during the treadmill phase. The expired gases were analyzed directly during treadmill walking, with the valve mask connected to the gas analyzer (Med Graphics d TM CPX cycleby-cycle analyzer) with a flexible tube. In all cases the same ortoprosthetist was responsible for foot assembly and dismantling, as well as for adjustments. Each subject used the same pair of shoes for the two series of tests. A satisfaction index was established by the subject after evaluation of each foot: the rating was determined on a visual scale ranging from 0 to 100, 0 corresponding to "entirely unsatisfactory" and 100 to "entirely satisfactory." In Group 2, in view of the difficulty experienced by elderly people in walking on a treadmill, only the self-selected speed test with oxygen consumption measurement by open-circuit indirect calorimetry was performed. All the vascular amputee patients had previously undergone a series of noninvasive vascular study to ensure better evaluation of lower-limb arteriopathy in both the nonamputated limb and the stump. Studies of the nonamputated limb included: Doppler measurement of the systolic ankle pressure index (relation of SBP measured at the ankle to humeral SBP); transcutaneous oxygen tension (TcPO2) (Radiometer TCM 2) on the forefoot in strict supine position; recording pulse plethysmography signal by gauge on the second toe, at rest and after ischemia provoked by 4-minute calf cuff = calculation of the waveform's magnification; venoarteriolar reflexe by TcPO2 registered on the dorsum of the foot: fluctuation in values when moving from supine to seated position. In the residual limb we recorded TcPO2 in supine position at the top of the antero-external face of the stump. The results were exploited by Student Fischer's paired test; the test was verified by variance analysis and probability was deemed significant when p was less than.05. Group I RESULTS Table 2 shows the oxygen uptake (~/O2) values recorded during walking at self-selected speed, on level treadmill at progressive speed, and on 5% inclined and then declined treadmill. Free walking speed was higher with the prototype foot than with the SACH foot, reaching a mean value close to that of a healthy, nonamputated adult. The VO2 was identical for the two devices when calculated per minute of walking, and lower with the new prosthetic foot when calculated in terms of meters walked. During walking on level treadmill at progressive speed, energy expenditure was lower with the prototype foot and the difference became more significant as speed increased. However, the small number of patients tested at fast speed (6kph) made it impossible to draw significant statistical conclusions. The same increased bioenergetic efficiency linked to the energy-storing foot was encountered with inclined treadmill walking, whether positive or negative (changing the chronology of inclined treadmill walking in the course of phases B and C had no significant effect on the recorded VO2 values). The results of cardiocirculatory adaptation during the free walking phase are given in table 3 (percentage of maximum theoretical heart rate attained at the eighth minute of walking - tension adaptation) and in the course of treadmill walking

3 EVALUATION OF A NEW ENERGY-STORING FOOT, Casillas 41 Table 2:VO2 Values Collected From 12 Patients With Below-Knee Traumatic Amputation During Free Walking, Level Treadmill Walking at Different Speeds (Phase A) and Inclined Treadmill Walking (Phase B, C) Energy-Storing Foot ~'O2 at rest NS Free walking (n = 12) Phase A Velocity (m/rain) _ _ <0.01 ~'O2 (ml/kg/min) _ , 3.62 NS " 02 (ml/kg/m) , p = km/h Level treadmill , , < 0.05 n= 12 4km/h Level treadmill _ <0.05 n=2 6km/h Level treadmill _ _ 3.29 n=6 Treadmill test VO2 (ml/kg/min) Phase B Phase C Incline treadmill 5% _ <0.02 4km/h--n = 12 Decline treadmill 5% _ 1.54 <0.02 Decline treadmill 5% <.002 4km/h--n = 12 Incline treadmill 5% , _ <0.01 at 4km/h with a positive incline of 5%, which is the most solicited from a bioenergetic point of view (difference of heart rate after effort and at rest before effort - tension adaptation). Lastly, these patients reported on average a far higher satisfaction rating when walking with the energy-storing foot: a mean rating of 84.6 _+ 16.6% against 63.8 _+ 28.3% for the SACH foot. Vascular Amputee Patients Table 4 gives the results of the angiological investigations. The patients were classified according to the hemodynamic evaluation of the nonamputated limb on the systolic pressure index values, 5 lower-limb arteriopathy stages in increasing order of severity: index above 0.95; index lying between 0.70 and 0.95; index lying between 0.55 and 0.70; index lying between 0.40 and 0.55 and index below The mean walking speed and VO2 values recorded during the test on prepared walkway for the two types of foot are shown in table 5. There were no significant differences between these values, this may be attributed to the use of one or other of the two feet. The figures for cardiocirculatory adaptation are presented in table 6. DISCUSSION The concept of energy storing has its origins in the search for a dynamic action in the prosthesis based on the energy generated in walking. The concept therefore seeks to recreate the propulsive effect normally provided by the plantar flexors, energy is stored during the heel-contact phase and then released during the final plantar-contact phase. A number of prosthetic feet based on this concept have been manufactured: Flex Foot, e Flex Walk, e Carbon Copy II, f and Safe II. g The Proteor foot is of recent design and is not commercially available. It seemed worthwhile to submit it to preliminary evaluation. This foot (fig) consists of two flexible carbon strips embedded in low-density polyurethane foam; as soon as the heel is solicited, the absorption of ground pressure is ensured by coiling of the rear strip, the propulsive role being performed by the front strip. The SACH foot, by contrast, adopts a passive system from the mechanical point of view. It has a wooden core representing the tarsus, a forefoot in compact polyurethane, and an alveolate polyurethane heel that gives the foot a certain degree of absorption and facilitates the stride in association with the incurvation of the forefoot. The SACH device has been available since the early 1960s and is the most prescribed foot in the world. It is radically different in terms of conception from energystoring feet and possesses no single-axis articulation at the ankle even though this feature procures greater walking comfort. 4-6 Measurement of free walking speed is a good criterion for functional evaluation of walking, because it is reputed to correspond to the optimum bioenergetic efficiency level. 7,s A comparison of this self-selected speed in our series of traumatic patients fitted with a SACH foot with identical groups evaluated in other studies, placed our patients in an Table 3: Cardiocirculatory Adaptation in Patients With Traumatic Amputation Energy-Storing Foot Free walking (n = 12) Percentage of Maximum Theoretical Heart Rate 60.5% 57.8% NS SBP/DBPmmHg/mmHg 160 _+ 15/96 _ / NS Treadmill incline test 5% (n = 12) HR following effort - HR at rest NS SBP/DBPmmHg/mmHg 146 +_ 20/ _+ 22/83 _+ 13 NS

4 42 EVALUATION OF A NEW ENERGY-STORING FOOT, Casillas Table 4: Results of Vascular Explorations in 12 Patients With Below-knee Vascular Amputation. Classification in Increasing Order of Severity According to Ankle Systolic Pressure Index. Included: TcPO2 Values on the Forefoot and the Stump Antero-external Face, Pulse Plethysmography on the Second Toe; Reactivity to Ischemia (RHT With Amplitude Magnification); Presence (if any) of Veno-Arteriolar Reflex Pulse Patients Foot TcPOz (mm Hg) VAR Plethysmography RHT Stump TcPO2 (mm Hg) Ankle pressure index > 0.95 Va (1.2) 30 Ta (1.5) 50 Si (1.3) > Index > > Index > > Index > 0.40 Mean Pe Pr La Sc La (2.7) 37 Mean 55 _+ 6 4-/1+ 5+/0-4-/ (48-65) (37-68) Mi Bo Ro (1.8) 50 Tr (1.3) 40 Mean _+ 5 + = Present. - = Absent. Abbreviations: TcPO2, transcutaneous oxygen tension; VAR, Veno Arteriolar Reflex; RHT, Reactive Hyperemia Test. intermediate position (75m/rain): 71m/min for the Wagner series, m/min for Nielsen ~ and 64.4m/min for Barth. H But Nielsen specified three very active patients with a mean walking speed of 80.5ngmin, and Lehmann 6 noted a speed of 91.3m/min in 10 subjects (again with the SACH foot). We are confronted yet again, and in a peculiarly pronounced form, with the classic notion of a slackening of free speed when there is a vascular cause of amputation ~'12 in our arteritic patients. The use of the prototype foot by traumatic patients led to a significant improvement of 6.4% in free walking speed in comparison with the SACH foot. For the traumatic amputee patients training in the use of the SACH foot is an important factor given the amount of time elapsed between the amputation and the test. A shorter period of adaptation would probably have resulted in even faster walking with the prototype foot. In similar protocol conditions (SACH foot versus Flex Foot), Nielsen ~ reported an improvement of 9% in 7 patients with traumatic below-knee amputations (mean age: 26.7 years years). Among the 7, the author distinguished 3 physically fit patients whose free walking rate with the SACH foot was 80.5m/rain, ie, the same rate as that of a nonamputated subjectj Bioenergetic efficiency in these patients was excellent and it is not surprising that improvement at self-selected speed is less pronounced with the Flex Foot. Wagner 9 did not observe any difference with regard Table 5:~/O2 and Walking Speed Values for 12 Patients With Below-knee Vascular Amputation in the Course of Walking Test on Flat Surface at Self-Selected Speed Energystoring Foot ~/O2 at rest (ml/kg/min) _ 0.80 NS Velocity (m/min) NS 702 (ml/kg/min) _+ 1, _ NS 702 (ml/kg/m) NS to either speed or rhythm. Similarly, Lehmann ~3 noted an absence of improvement in free walking speed in 9 very active below-knee amputees: 90.0m/min with a SACH foot, 90.2m/min with a Seattle foot and 90.0m/min with a Flex Foot. In patients amputated for lower-limb arteriopathy, there was no significant variation in free walking speed caused by the installation of a supposedly more effective foot. As for bioenergetic walking efficiency (VO2 measured per meters covered) at self-selected speed, there was an improvement in patients with traumatic amputations and no change with the vascular group. Our values for the traumatic group must be compared with those of Waters 12 who, in his study of 14 young adult below-knee amputees, note a mean value of 0.20 _+ 0.05mL/kg/m for a speed of m/min. In addition, Torburn 14 tested 5 patients in free walking (3 patients with traumatic below-knee amputation and 2 patients with vascular below-knee amputations) using four different dynamic feet versus SACH. His study did not show any modification with regard to metabolic efficiency. Lehmann, ~3 compared the SACH foot to two energy-storing feet (Seattle and Flex Foot) in 9 active patients with below-knee amputations (comfortable walking speed of 90m/min while using the SACH foot), and did not objectify an improvement in free walking speed nor a bioenergetic optimization. It is likely that these 9 highly mobile patients with amputations Table 6: Cardiocirculatory Adaptation in Patients With Vascular Amputation Energy-Storing Foot Percentage of maximum theoretical heart rate 73% 76% NS SBP/DBP (mm Hg)/ (mm Hg) 169 _+ 12/86 _ _+ 12/86 _+ 10 NS Arch Phys Med Rehabil Vo! 76, January 1995

5 EVALUATION OF A NEW ENERGY-STORING FOOT, Casillas 43 Forefoot portion Mal leol i The Proteor prototype foot. Heel cavit,v portion with the SACH foot, like Nielsen's 3 active subjects 4 possessed maximum walking efficiency, because they attained and even exceeded the comfortable walking speed of ablebodied subjects: a technical improvement to the apparatus cannot change either self-selected speed or the 402 corresponding to this speed. Although it is less physiological, treadmill walking makes it possible to standardize the results. Use of the treadmill is not usually feasible with vascular amputee patients who are mostly elderly subjects with balance disorders that require the use of crutches. Speed is increased in the course of phase A so that the optimum walking performance may be determined. Our results were similar to those of Nielsen, ~ specifying a greater bioenergetic walking efficiency with the energy-storing foot at speeds approaching comfortable walking speeds for these subjects. The number of patients tested at 6kph was too small for statistical analysis. With regard to fast treadmill walking, Lehmann ~3 did not report significant differences between the energy-storing foot and the SACH foot. The purpose of phases B and C was to study the response to slope variation at a constant speed of 4km/ h, ie, close to the mean speed of a person with a traumatic below-knee amputation. 1'~2 It is important to evaluate the bioenergetic repercussions of flexion and extension demands make on the prosthetic foot; the improvement observed on the level treadmill was also apparent with positive and negative inclined treadmill with reference to walking physiology (negative incline energy economy). The cardiocirculatory effect may restrict walking, particularly in patients with vascular amputation. Heart rate frequency indirectly reflects overall metabolic effort '5 and heart adaptation. A heart rate that is 70% to 80% in excess of the maximum theoretical rate may cause walking to be halted. 16 Although this point was not reached with our traumatic patients, it was attained with the arteritic patients, without, however, causing the walking test to be discontinued because of fatigue. No difference in heart rate or blood pressure, attributable to either of the shoes, was observed. Functional vascular explorations in our arteritic patients showed a marked heterogenicity of the hemodynamic and microcirculatory state of the nonamputated limb. The TcPO2 measurement on the dorsal surface of the foot provides important information on the microcirculatory state17; none of the patients presented a permanent ischemia because TcPO2 was always more than 40mmHg. TM We are, therefore, concerned with patients presenting with lower-limb arteriopathy lesions, compensated from the microcirculatory point of view despite the diversity of the hemodynamic state as clearly shown by the differences in the systolic pressure index. This microcirculatory adaptation to the lower-limb arteriopathy lesions was confirmed by pulse plethysmography in each patient's second toe. There is, however, a pronounced heterogenicity regarding vaso-regulation, as was shown by the results of the venoarteriolar reflex and the reactive hyperemia test. There does not seem to be a correlation between the dynamic tests and the systolic pressure index. The TcPO2 figures collected from the stump also differed widely from one person to another, although three cases were noted with a TcPO2 of less than 40mmHg but more than 20mmHg. Despite the sometimes painful constraints inherent in using a socket contact, '9 there was no discontinuation of the free walking test as a result of stump pains, or for that matter of a claudication of the remaining member. Evaluation on ground reaction force plate in association with the kinematic study makes it possible to reach a quantitative assessment of the power developed by a given muscular group. 3'2 Thus, Czerniecki et al 2t showed that in a person with below-knee amputation, running with the SACH foot, the excessive reliance on hip extensors as absorbers and energy producers could be partially reduced by fitting an energy-storing foot which restores the balance between knee and hip intervention with respect to absorption phenomena. In walking, the propulsive effect associated with the energystoring foot is less pronouncedy but the improvement in absorption during heel contact is preserved. This modeling of walking activity from mechanical and kinematic data has already resulted in a proposed classification of the different prosthetic feet according to their quality.23 The purely biomechanical aspects linked to an energy-storing foot include: lengthened stride on the nonamputated side, posterior stride time increase on amputated side, reduced amplitude of center-of-gravity vertical movement, 24'25 increased mobility of the ankle joint, 26 improvement in impulsive function on the amputated side, and greater forefoot compliance. 6'~3"27 CONCLUSION This new energy-storing foot improves the walking performance of subjects already displaying excellent functional possibilities, but has no effect with elderly, slow-walking patients with vascular amputation. There would seem, in fact, to be an opposition between the two functional qualities of a prosthetic foot (dynamic aspect and stability); the vascular patient seeks easy proprioceptive support control on the amputated side--in other words, maximum safety. The energy-storing foot may improve gait comfort for patients with vascular amputations by reducing shearing force at the stump and the weight of the prosthesis. References 1. Fisher SV, Gullickson G. Energy cost of ambulation in health and disability: a literature review. Arch Phys Med Rehabil 1978;59: Huang CT, Jackson JR, Moore NB, Fine PR, Kuhlemeier KV, Traugh GH, et al. Amputation: energy cost of ambulation. Arch Phys Med Rehabil 1979;60: Winter DA, Eng P. Energy generation and absorption at the ankle and knee during fast, natural, and slow cadences. Clin Orthop Rel Res 1983; 175: Arch Phys Med RehabU Vol 76, January 1995

6 44 EVALUATION OF A NEW ENERGY-STORING FOOT, CasUlas 4. Goh JCH, Solomonidis SE, Spence WD, Paul JP. Biomechanical evaluation of SACH and uniaxial feet. Prosthet Orthot Int 1984;8: James KB, Stein RB. Improved ankle-foot system for above-knee amputees. Am J Phys Med 1986;65: Lehmann JF, Price R, Boswell-Bessette S, Dralle A, Questad K. Comprehensive analysis of dynamic elastic response feet: Seattle ankle/lite foot versus SACH foot. Arch Phys Med Rehabil 1993;74: Bard G, Ralston HJ. Measurement of energy expenditure during ambulation with special reference to evaluation of assistive devices. Arch Phys Med Rehabil 1959;40: Inman VT. Conservation of energy in ambulation. Arch Phys Med Rehabil 1967;48: Wagner J, Sienko S, Supan T, Barth D. Motion analysis of SACH vs. flex-foot in moderately active below-knee amputees. Clin Prosthet Orthot 1987; 11: Nielsen DH, Shurr DG, Golden JC, Meier K. Comparison of energy cost and gait efficiency during ambulation in below-knee amputees using different prosthetic feet: a preliminary report. J Prosthet Orthot 1988; 1: Barth DG, Schumacher L, Sienko S. Gait analysis and energy cost of below-knee amputees wearing six different prosthetic feet. J Prosthet Orthot 1989;2: Waters RL, Perry J, Antonelli D0 Hislop HJ. Energy cost of walking of amputees: the influence of level amputation. J Bone Joint Surg 1976;58: Lehmann JF, Price R, Boswell-Bessette S, Dralle A, Questad K, delatenr BJ. Comprehensive analysis of energy storing prosthetic feet: Flex foot and Seattle foot versus standard SACH foot. Arch Phys Med Rehabil 1993;74: T0rburn L, Perry J, Ayyappa E, Shanfield SL. Below-knee amputee gait with dynamic elastic response prosthetic feet: a pilot study. J Rehabil Res Develop 1990;27(4): ,~.strand P, Rodahl K. Textbook of work physiology. 3rd rev. ed. New York: McGraw-Hill, Nielsen DH, Amundsen LR. Exercise physiology: an overview with emphasis on aerobic capacity and energy cost. In: Livingstone CH, editor. Clinics in Physical Therapy. 1981: Rooke TW, Osmundson PJ. Variability and reproductibility of transcutaneous oxygen tension measurement in the assessment of peripheral vascular disease. Angiology 1989; Byrne P, Provan JL, Ameli FM, Jones DP. The use of transcutaneous oxygen tension measurements in the diagnosis of peripheral vascular insufficiency. Ann Surg 1983; 200: Casillas J-M, Michel C, Aurelle B, Becker F, Marcer I, Schultz S, et al. Transcutaneous oxygen pressure: a definitive measure for prosthesis fitting on below-knee amputations. Am J Phys Med Rehabil 1993; 72: Czerniecki JM, Gitter A. Insights into amputee running. A muscle work analysis. Am J Phys Med Rehabil 1992;71: Czerniecki JM, Gitter A, Munro C. Joint moment and muscle power output characteristics of below-knee amputees during running: the influence of energy storing prosthetic feet. J B iomech 1991;24: Gitter A, Czerniecki J, Degroot DM. Biomechanical analysis of the influence of prosthetic feet on below-knee amputee walking. Am J Phys Med Rehabil 1991;70: Ehara Y, Beppu M, Nomura S, Kunimi Y, Takahashi S. Energy storing property of so-called energy-storing prosthetic feet. Arch Phys Med Rehabil 1993;74: MacFarlane PA, Nielsen DH, Shurr DG, Meier K. Gait comparisons for below-knee amputees using a flex-foot versus a conventional prosthetic foot. J Prosthet Orthot 1990;3: Wirta RW, Mason R, Calvo K, Golbranson FL. Effect on gait using various prosthetic ankle-foot devices. J Rehabil Res Develop 1991;28: Barr AE, Siegel KL, Danoff JV, McGarvey III CL, Tomasko A, Sable I, et al. Biomechanical comparison of the energy-storing capabilities of SACH and carbon copy II prosthetic feet during the stance phase of gait in a person with below-knee amputation. Phys Ther 1992;72: Menard MR, MacBride ME, Sanderson DJ, Murray DD. Comparative biomechanical analysis of energy-storing prosthetic feet. Arch Phys Med Rehabil 1992;73: Suppliers a. Hans Rudolph Incorporated, 7200 Wyandotte, Kansas City, MO b. Life Scope 6 telemeter, Nihon Kohden Corporation, 31.4 Nishiochiai 1, Chome, Simjuku-Ku, Tokyo 161 Japan. c. Marquette blood pressure monitor Model 1950, Marquette Electronics Incorporated, USA, 8200 W. Tower Avenue, Milwaukee, WI d. Med Graphics TM CPX cycle-by-cycle analyzer, Medical Graphics Corporation, 350 Oak Grove Parkway, St. Paul, MN e. Flex Foot Incorporated, Cabot Road 106, Laguna Hills, CA f. Carbon Copy II, Ohio Willow Vood Company, PO Box 192, Mt Sterling, OH g. Safe II, Campbell Childs Incorporated, 400 Industrial Circle, White City, OR