Transverse rotation and longitudinal translation during prosthetic gait - a literature review

Improved technology allows for more accurate gait analysis to increase awareness of nonoptimized prosthetic gait patterns and for the manufacture of sophisticated prosthetic components to improve nonoptimized gait patterns. However, prescriptions are often based on intuition rather than rigorous research findings for evidence-based practice. The number of studies found in the literature that are based on prosthetic research regarding transverse rotation and longitudinal translation is small when compared to topics regarding other types of movements. Some design criteria for prosthetic components described in those studies that permit transverse rotation and longitudinal translation can be found in current designs. However, little research has been conducted to establish their effectiveness on the gait parameters and residual limb. This literature review is an investigation into these motions between the socket and the prosthetic foot, with particular reference to gait characteristics and prosthetic design criteria

Measurement system for the evaluation of alternating pressure redistribution mattresses using pressure relief index and tissue perfusion – a preliminary study

Clinicians who are selecting dynamic support surfaces such as alternating pressure redistribution mattresses (APRMs) for the prevention and treatment of pressure ulcers are faced with commercial literature that predominantly reports on magnitudes of interface pressures, rather than on additional parameters. The aim of this preliminary study was to generate a pressure relief index (PRI) to evaluate dynamic support surfaces using the magnitude of interface pressures as well as their duration. Data for generating a PRI were captured from 11 subjects on two different dynamic support surfaces using three different, arbitrarily selected, interface pressure thresholds. Tissue perfusion measurements were used to evaluate the reliability of the calculated PRI. The results demonstrate a good relationship (r=0.7) between PRI and tissue perfusion values. The generated PRI appears to be a reliable indicator of the recovery time allowed below a given interface pressure and is therefore a useful parameter for selecting appropriate dynamic support surfaces

The biomechanical effects of the inclusion of a torque absorber and type of knee units on trans-femoral amputee gait

This paper reports on a pilot study investigating the effects on the gait of two transfemoral amputees of to the inclusion of a torque absorber (TA) and its location relative to the knee unit. Both subjects carried out gait tests with a prosthesis with no TA with, a TA proximal to the knee unit and with a TA distal to the knee unit. Three-dimensional gait analysis was carried out to establish the kinematic and kinetic gait parameters of both the prosthetic and sound side. It was found that the TA did not significantly affect the sagittal kinetic and kinematic parameters of the sound or the prosthetic side. However, for one subject the axial rotation of the socket relative to the foot was significantly greater with the TA. It was concluded that by using the methodology of this pilot study, it is possible to investigate the rotations in the transverse plane within the prosthetic limb and pelvis. Further, including a TA may reduce the relative motion between the stump and the socket and therefore may decrease skin breakdown due to diminished shear force

Scoliosis imaging : an analysis of radiation risk in the CT scan projection radiograph and a comparison with projection radiography and EOS

Introduction: Scoliosis is defined as a deformity of the spine with lateral curvature in the coronal plane. It requires regular X-ray imaging to monitor the progress of the disorder, therefore scoliotic patients are frequently exposed to radiation. It is important to lower the risk from these exposures for young patients. The aim of this work is to compare organ dose (OD) values resulting from Scan Projection Radiograph (SPR) mode in CT against projection radiography and EOS® imaging system when assessing scoliosis. Methods: A dosimetry phantom was used to represent a 10-year old child. Thermoluminescent dosimetry detectors were used for measuring OD. The phantom was imaged with CT in SPR mode using 27 imaging parameters; projection radiography and EOS machines using local scoliosis imaging procedures. Imaging was performed in anteroposterior, posteroanterior and lateral projections. Results: 17 protocols delivered significantly lower radiation dose than projection radiography (p <0.05). OD values from the CT SPR imaging protocols and projection radiography were statistically significant higher than the results from EOS. No statistically significant differences in OD were observed between 10 imaging protocols and those from projection radiography and EOS imaging protocols (p >0.05). Conclusion: EOS has the lowest dose. Where this technology is not available we suggest there is a potential for OD reduction in scoliosis imaging using CT SPR compared to projection radiography. Further work is required to investigate image quality in relation to the measurement of Cobb angle with CT SPR

Energy flow analysis of amputee walking shows a proximally-directed transfer of energy in intact limbs, compared to a distally-directed transfer in prosthetic limbs at push-off

Reduced capacity and increased metabolic cost of walking occurs in amputees, despite advances in prosthetic componentry. Joint powers can quantify deficiencies in prosthetic gait, but do not reveal how energy is exchanged between limb segments. This study aimed to quantify these energy exchanges during amputee walking. Optical motion and forceplate data collected during walking at a self-selected speed for cohorts of 10 controls, 10 unilateral trans-tibial, 10 unilateral trans-femoral and 10 bilateral trans-femoral amputees were used to determine the energy exchanges between lower limb segments. At push-off, consistent thigh and shank segment powers were observed between amputee groups (1.12W/kg vs. 1.05W/kg for intact limbs and 0.97W/kg vs. 0.99W/kg for prosthetic limbs), and reduced prosthetic ankle power, particularly in trans-femoral amputees (3.12W/kg vs. 0.87W/kg). Proximally-directed energy exchange was observed in the intact limbs of amputees and controls, while prosthetic limbs displayed distally-directed energy exchanges at the knee and hip. This study used energy flow analysis to show a reversal in the direction in which energy is exchanged between prosthetic limb segments at push-off. This reversal was required to provide sufficient energy to propel the limb segments and is likely a direct result of the lack of push-off power at the prosthetic ankle, particularly in trans-femoral amputees, and leads to their increased metabolic cost of walking

The effects of prosthetic ankle stiffness on stability of gait in people with trans-tibial amputation

The ability to control balance during walking is a critical precondition for minimizing fall risk, but is compromised in persons with lower-limb loss due to reduced sensory feedback mechanisms and inability to actively modulate prosthesis mechanical function. Consequently, these individuals are at increased fall risk as compared to their able-bodied counterparts. A number of gait parameters, including symmetry and temporal variability in step/stride characteristics have been used as estimates of gait stability and fall risk. This study performed an investigation into prosthetic ankle rotational stiffness effects on gait parameters related to walking stability of trans-tibial prosthesis users. Five men walked with an experimental prosthesis that allowed for independent modulation of plantarflexion and dorsiflexion stiffness. Two levels of plantarflexion and dorsiflexion stiffness were tested during level, uphill, and downhill walking. The results demonstrate that low plantarflexion stiffness reduced time to foot-flat, and this was associated with increased perceived stability, while low dorsiflexion stiffness demonstrated trends in temporal-spatial parameters that are associated with improved gait stability (reduced variability and asymmetry). Prosthesis design and prescription for low rotational stiffness may enhance gait safety for trans-tibial prosthesis users at risk of unsteadiness and falls

Stance phase mechanical characterization of transtibial prostheses distal to the socket : a review

Achieving the required functionality of a trans-tibial prosthesis during the stance phase of gait (e.g., shock absorption, close to normal roll-over characteristics, and smooth transition into swing) depends on the “Amputee Independent Prosthesis Properties” (AIPPs), defined here as the mechanical properties of the prosthesis that directly influence the performance of the amputee. Accordingly, if research studies are to advance the design of prostheses to achieve improved user performance, AIPPs must be a primary consideration. However, the majority of reported studies can be categorized as either human performance testing of commercial prosthetic components or AIPP characterization; and only in a few notable cases have authors reported studies in which these two approaches are combined. Moreover, very little consistency exists in the current methods used for AIPP characterization, thus making comparisons between the results of such studies very difficult. This paper introduces a framework for studying prosthesis design, which includes AIPP characterization, human performance and/or gait simulation studies, and detailed design. This framework provides a structure for reviewing previous approaches to AIPP characterization, discussing both their merits and shortcomings, and their use in previous experimental and simulation studies. For the purposes of this review, stance phase AIPP models have been categorized as either lumped parameter or roll-over shape based

Performance of optimised prosthetic ankle designs that are based on a hydraulic variable displacement actuator (VDA)

Current energy storage and return (ESR) prosthetic feet only marginally reduce the cost of amputee locomotion compared to basic solid ankle cushioned heel (SACH) feet, possibly due to their lack of push-off at the end of stance. To our knowledge, a prosthetic ankle that utilises a hydraulic variable displacement actuator (VDA) to improve push-off performance has not previously been proposed. Therefore, here we report a design optimisation and simulation feasibility study for a VDA based prosthetic ankle. The proposed device stores the eccentric ankle work done from heel strike to maximum dorsiflexion in a hydraulic accumulator and then returns the stored energy to power push-off. Optimisation was used to establish the best spring characteristic and gear ratio between ankle and VDA. The corresponding simulations show that, in level walking, normal push-off is achieved and, per gait cycle, the energy stored in the accumulator increases by 22% of the requirements for normal push-off. Although the results are promising, there are many unanswered questions and, for this approach to be a success, a new miniature, low-losses, lightweight VDA would be required that is half the size of the smallest commercially available device

The effects of transverse rotation angle on compression and effective lever arm of prosthetic feet during simulated stance

Background and Aim: Unlike sagittal plane prosthesis alignment, few studies have observed the effects of transverse plane alignment on gait and prosthesis behaviour. Changes in transverse plane rotation angle will rotate the points of loading on the prosthesis during stance and may alter its mechanical behaviour. This study observed the effects of increasing the external transverse plane rotation angle, or toe-out, on foot compression and effective lever arm of three commonly prescribed prosthetic feet. Technique: The roll-over shape of a SACH, Flex, and single-axis foot was measured at four external rotation angle conditions (0°, 5°, 7°, and 12° relative to neutral). Differences in foot compression between conditions were measured as average distance between roll-over shapes. Discussion: Increasing the transverse plane rotation angle did not affect foot compression. However, it did affect the effective lever arm, which was maximised with the 5° condition, although differences between conditions were small