Thomas Schmalz

Energy expenditure and biomechanical characteristics of lower limb amputee gait:: The influence of prosthetic alignment and different prosthetic components

In this study, the influence of different prosthetic alignments and components on oxygen consumption and the important biomechanical characteristics of the normal gait pattern of leg amputees was investigated. With 15 transtibial and 12 transfemoral amputees, the oxygen consumption during walking on a treadmill was analyzed and biomechanical parameters during walking on even ground at a self-selected speed were defined. The amputation of all patients was caused by trauma. Variations of the prosthetic alignment affect the energy consumption of transfemoral amputees more significantly than that of transtibial amputees. Comparison of different prosthetic feet worn by transtibial amputees did not show significant differences regarding metabolic parameters. Compared with conventional hydraulic knee controls, the oxygen consumption of transfemoral amputees provided with an electronically controlled hydraulic knee joint is reduced. All investigated variations can be clearly characterized by the sagittal moments acting on the joints of the prosthetic limb during gait.

Comparative Biomechanical Analysis of Current Microprocessor-Controlled Prosthetic Knee Joints

OBJECTIVE To investigate and identify functional differences of 4 microprocessor-controlled prosthetic knee joints (C-Leg, Hybrid Knee [also called Energy Knee], Rheo Knee, Adaptive 2). DESIGN Tested situations were walking on level ground, on stairs and ramps; additionally, the fall prevention potentials for each design were examined. The measuring technology used included an optoelectronic camera system combined with 2 forceplates as well as a mobile spiroergometric system. SETTING The study was conducted in a gait laboratory. PARTICIPANTS Subjects with unilateral transfemoral amputations (N=9; mobility grade, 3-4; age, 22-49y) were tested. INTERVENTIONS Participants were fitted and tested with 4 different microprocessor-controlled knee joints. MAIN OUTCOME MEASURES Static prosthetic alignment, time distance parameters, kinematic and kinetic data and metabolic energy consumption. RESULTS Compared with the Hybrid Knee and the Adaptive 2, the C-Leg offers clear advantages in the provision of adequate swing phase flexion resistances and terminal extension damping during level walking at various speeds, especially at higher walking speeds. The Rheo Knee provides sufficient terminal extension; however, swing phase flexion resistances seem to be too low. The values for metabolic energy consumption show only slight differences during level walking. The joint resistances generated for descending stairs and ramps relieve the contralateral side to varying degrees. When walking on stairs, safety-relevant technical differences between the investigated joint types can be observed. Designs with adequate internal resistances offer stability advantages when the foot is positioned on the step. Stumble recovery tests reveal that the different knee joint designs vary in their effectiveness in preventing the patient from falling. CONCLUSIONS The patient benefits provided by the investigated electronic prosthetic knee joints differ considerably. The C-Leg appears to offer the amputee greater functional and safety-related advantages than the other tested knee joints. Reduced loading of the contralateral side has been demonstrated during ramp and stair descent. Metabolic energy consumption does not vary significantly between the tested knees. Hence, this parameter seems not to be a suitable criterion for assessing microprocessor-controlled knee components.

Immediate Effects of a New Microprocessor-Controlled Prosthetic Knee Joint: A Comparative Biomechanical Evaluation

OBJECTIVE To investigate the immediate biomechanical effects after transition to a new microprocessor-controlled prosthetic knee joint. DESIGN Intervention cross-over study with repeated measures. Only prosthetic knee joints were changed. SETTING Motion analysis laboratory. PARTICIPANTS Men (N=11; mean age ± SD, 36.7±10.2y; Medicare functional classification level, 3-4) with unilateral transfemoral amputation. INTERVENTIONS Two microprocessor-controlled prosthetic knee joints: C-Leg and a new prosthetic knee joint, Genium. MAIN OUTCOME MEASURES Static prosthetic alignment, time-distance parameters, kinematic and kinetic parameters, and center of pressure. RESULTS After a half-day training and an additional half-day accommodation, improved biomechanical outcomes were demonstrated by the Genium: lower ground reaction forces at weight acceptance during level walking at various velocities, increased swing phase flexion angles during walking on a ramp, and level walking with small steps. Maximum knee flexion angle during swing phase at various velocities was nearly equal for Genium. Step-over-step stair ascent with the Genium knee was more physiologic as demonstrated by a more equal load distribution between the prosthetic and contralateral sides and a more natural gait pattern. When descending stairs and ramps, knee flexion moments with the Genium tended to increase. During quiet stance on a decline, subjects using Genium accepted higher loading of the prosthetic side knee joint, thus reducing same side hip joint loading as well as postural sway. CONCLUSIONS In comparision to the C-Leg, the Genium demonstrated immediate biomechanical advantages during various daily ambulatory activities, which may lead to an increase in range and diversity of activity of people with above-knee amputations. Results showed that use of the Genium facilitated more natural gait biomechanics and load distribution throughout the affected and sound musculoskeletal structure. This was observed during quiet stance on a decline, walking on level ground, and walking up and down ramps and stairs.

Transfemoral amputees walking on a rotary hydraulic prosthetic knee mechanism: A preliminary report

Results from multiple instrumented gait analysis trials of seven traumatic transfemoral amputees capable of community ambulation are reviewed. All subjects used a novel rotary hydraulic prosthetic knee offering both stance and swing phase control, in combination with various contemporary prosthetic ankle-foot mechanisms. Unlike previous hydraulic stance and swing units, the Otto Bock 3R80 knee provides stance stability whenever the desired weightbearing load is applied to the prosthesis The mechanical principles and basic functions of the knee joint are described. Results from three phases of gait studies are presented to identify inter-individual variability and the effect of varying sagittal plane knee alignment and the ankle-foot mechanism selected. Subjective amputee preferences for specific foot devices are presented The pattern of hip moments on the amputated side during stance phase are characteristic of the individual amputee. However, the magnitude and timing of the hip moments vary considerably between individual amputees. So long as the prosthetic knee remains biomechanically stable, it appears that alignment alterations or the use of varying foot devices have little impact on the hip extension moment. On the other hand, the hip flexion effort required for the amputee to initiate knee flexion in late stance phase is directly related to the linear position of the prosthetic knee in the sagittal plane: the more posterior the knee, the greater the effort needed to begin swing phase Clinical function of this hydraulic prosthetic knee was considered satisfactory with all tested ankle-foot mechanisms. Transfemoral amputee preference for specific prosthetic feet in this study seemed to be determined by two biomechanical factors: (1) their ability to benefit from the use of a dynamic response foot without compensating with the non-amputated knee, and (2) their ability to generate a hip extension moment on the prosthetic side during the weight acceptance phase of gait

Stair ascent with an innovative microprocessor-controlled exoprosthetic knee joint.

Abstract Climbing stairs can pose a major challenge for above-knee amputees as a result of compromised motor performance and limitations to prosthetic design. A new, innovative microprocessor-controlled prosthetic knee joint, the Genium, incorporates a function that allows an above-knee amputee to climb stairs step over step. To execute this function, a number of different sensors and complex switching algorithms were integrated into the prosthetic knee joint. The function is intuitive for the user. A biomechanical study was conducted to assess objective gait measurements and calculate joint kinematics and kinetics as subjects ascended stairs. Results demonstrated that climbing stairs step over step is more biomechanically efficient for an amputee using the Genium prosthetic knee than the previously possible conventional method where the extended prosthesis is trailed as the amputee executes one or two steps at a time. There is a natural amount of stress on the residual musculoskeletal system, and it has been shown that the healthy contralateral side supports the movements of the amputated side. The mechanical power that the healthy contralateral knee joint needs to generate during the extension phase is also reduced. Similarly, there is near normal loading of the hip joint on the amputated side.

Biomechanical Differences between Two Exoprosthetic Hip Joint Systems during Level Walking

Previous studies have shown low end-user acceptance of a hip disarticulation style prosthesis and that the limitations of such prostheses, including poor gait pattern, socket discomfort, weight of the prosthesis, loss of mobility, instability and high energy consumption are a contributing factor. This study was initiated to determine if a new style of prosthetic hip joint could help to overcome some of the limitations concerning the gait pattern. The present study analyzed the gait pattern of six hip disarticulation amputee subjects. The objective was to compare two different prosthetic hip joints, both from Otto Bock HealthCare: The new Helix3D and the 7E7, which is based on the Canadian model proposed by McLaurin (1954). Kinematics and kinetics were recorded by an optoelectronic camera system with six CCD cameras and two force plates. During weight acceptance, the Helix3D extends considerably slower and reaches full extension later than the 7E7. The increased range of pelvic tilt observed with hip disarticulation amputees is significantly reduced (by 5 ± 3 degrees) when using the Helix3D Hip Joint. In addition, this system showed increased stance phase knee joint flexion as well as increased maximum swing phase knee flexion angles compared to the 7E7. These motion analysis results show that the Helix3D Hip Joint can reduce gait abnormalities compared to the uniplanar design of the 7E7 hip joint.

Effects of Adaptation to a Functionally New Prosthetic Lower-Limb Component: Results of Biomechanical Tests Immediately after Fitting and after 3 Months of Use

ABSTRACT Ten established transfemoral amputees completed biomechanical tests after they had been fitted with a new prosthetic knee joint (test sessions: a few hours and 3 months after fitting). The required adaptation phase after fitting of a new prosthesis is frequently discussed. This phase is considered to be completed when the test result is no longer influenced by the patients’ learning processes. The study contributes to the understanding of the adaptation effects experienced prosthesis users require to master various motion patterns after being fitted with functionally new prosthetic knee joints. Biomechanical parameters (ground reaction forces, joint moments, and joint angles at the knee and the hip) were measured for level walking as well as ascending and descending ramps and stairs. For level walking, walking on ramps, and descending stairs, relevant differences in the parameters between the two tests could not be identified. For ascending stairs, the results of both tests showed obvious differences. The functions of a newly fitted prosthetic component can be intuitively used after a few hours of adaptation time if the motion patterns required are similar to that of the previous fitting. If specific functions require the learning of a motion, the learning processes will require a longer adaptation period.

A functional comparison of conventional knee–ankle–foot orthoses and a microprocessor-controlled leg orthosis system based on biomechanical parameters

Background: The microprocessor-controlled leg orthosis C-Brace enables patients with paretic or paralysed lower limb muscles to use dampened knee flexion under weight-bearing and speed-adapted control of the swing phase. Objectives: The objective of the present study was to investigate the new technical functions of the C-Brace orthosis, based on biomechanical parameters. Study design: The study enrolled six patients. The C-Brace orthosis is compared with conventional leg orthoses (four stance control orthoses, two locked knee–ankle–foot orthoses) using biomechanical parameters of level walking, descending ramps and descending stairs. Methods: Ground reaction forces, joint moments and kinematic parameters were measured for level walking as well as ascending and descending ramps and stairs. Results: With the C-Brace, a nearly natural stance phase knee flexion was measured during level walking (mean value 11° ± 5.6°). The maximum swing phase knee flexion angle of the C-Brace approached the normal value of 65° more closely than the stance control orthoses (66° ± 8.5° vs 74° ± 6.4°). No significant differences in the joint moments were found between the C-Brace and stance control orthosis conditions. In contrast to the conventional orthoses, all patients were able to ambulate ramps and stairs using a step-over-step technique with C-Brace (flexion angle 64.6° ± 8.2° and 70.5° ± 12.4°). Conclusion: The results show that the functions of the C-Brace for situation-dependent knee flexion under weight bearing have been used by patients with a high level of confidence. Clinical relevance The functional benefits of the C-Brace in comparison with the conventional orthotic mechanisms could be demonstrated most clearly for descending ramps and stairs. The C-Brace orthosis is able to combine improved orthotic function with sustained orthotic safety.

Biomechanical influences of shoulder disarticulation prosthesis during standing and level walking

Background: Modern prosthetic systems with more degrees of freedom offer the patient clearly improved functions. However, the influence of functional arm prostheses on body posture and gait have never been quantified. Objectives: The purpose of this investigation was to observe the impact of a functional arm prosthesis on body posture and gait of shoulder disarticulation patients. Study Design: Experimental, biomechanical. Methods: Eight patients with unilateral shoulder disarticulation were enrolled. Static posture and gait analyses were conducted with and without using a functional arm prosthesis. Static posture analysis using the L.A.S.A.R. Posture device as well as kinematic and kinetic gait analysis using an optoelectronic camera system combined with force plates were conducted with and without prosthesis in eight unilateral shoulder disarticulation patients. Results: Static analysis confirmed that an arm prosthesis improves body posture of amputees. Gait analysis revealed that compensatory movements during walking as well as external knee moments on the prosthetic side leg are significantly reduced when using a free swinging shoulder joint. Conclusions: An arm prosthesis does not only offer functional and cosmetic benefits. The results confirm that unilateral shoulder disarticulation patients benefit from a functional arm prosthesis with a free swinging shoulder joint in terms of optimized posture and gait dynamics. Clinical relevance This study demonstrates that shoulder disarticulation patients benefit from a functional prosthesis with a free swinging shoulder joint. Such prosthesis significantly improves body posture and gait characteristics, reduces compensatory movements and relieves distress to the musculoskeletal system. This should be considered when prescribing a prosthesis for shoulder disarticulation amputees.

Standing on slopes – how current microprocessor-controlled prosthetic feet support transtibial and transfemoral amputees in an everyday task

BackgroundConventional prosthetic feet like energy storage and return feet provide only a limited range of ankle motion compared to human ones. In order to overcome the poor rotational adaptability, prosthetic manufacturers developed different prosthetic feet with an additional rotational joint and implemented active control in different states. It was the aim of the study to investigate to what extent these commercially available microprocessor-controlled prosthetic feet support a natural posture while standing on inclines and which concept is most beneficial for lower limb amputees.MethodsFour unilateral transtibial and four unilateral transfemoral amputees participated in the study. Each of the subjects wore five different microprocessor-controlled prosthetic feet in addition to their everyday feet. The subjects were asked to stand on slopes of different inclinations (level ground, upward slope of 10°, and downward slope of −10°). Vertical ground reaction forces, joint torques and joint angles in the sagittal plane were measured for both legs separately for the different situations and compared to a non-amputee reference group.ResultsDifferences in the biomechanical parameters were observed between the different prosthetic feet and compared to the reference group for the investigated situations. They were most prominent while standing on a downward slope. For example, on the prosthetic side, the vertical ground reaction force is reduced by about 20%, and the torque about the knee acts to flex the joint for feet that are not capable of a full adaptation to the downward slope. In contrast, fully adaptable feet with an auto-adaptive dorsiflexion stop show no changes in vertical ground reaction forces and knee extending torques.ConclusionsA prosthetic foot that provides both, an auto-adaptive dorsiflexion stop and a sufficient range of motion for fully adapting to inclinations appears to be the key element in the prosthetic fitting for standing on inclinations in lower limb amputees. In such situations, this prosthetic concept appears superior to both, conventional feet with passive structures as well as feet that solely provide a sufficient range of motion. The results also indicate that both, transfemoral and transtibial amputees benefit from such a foot.