Mechanisms to absorb load in amputee running

Effect of High-Heeled Shoes on Balance and Lower-Extremity Biomechanics During Walking in Experienced and Novice High-Heeled Shoe Wearers

BACKGROUND

Wearing high-heeled shoes and carrying asymmetrical loads are common in ladies. However, knowledge of the effects of wearing high-heeled shoes on balance and lower-extremity biomechanics in experienced and novice high-heeled shoe wearers is lacking. The study aims to examine the effects of high-heeled shoes and asymmetrical load carrying on joint kinematics and kinetics of the lower extremity during walking as well as balance in experienced and novice high-heeled shoe wearers.

METHODS

Fifteen experienced and 15 novice high-heeled shoes wearers participated in this study. Using a motion analysis system, kinematic and kinetic data were collected while participants walked at their preferred speed in six conditions created from two types of shoes (9-cm high-heeled shoes and flat-heeled shoes) and three weights of symmetrical load (0%, 5%, and 10% of body weight). Stride time and length, step length, double support time, peak joint angles, and joint moments in a sagittal plane were analyzed. Single-leg and tandem-leg stance tests were performed in each condition.

RESULTS

Compared with experienced high-heeled shoe wearers, novice high-heeled shoe wearers had longer double support time and shorter stride length during 10% of body weight asymmetrical load walking; walked with greater knee flexion angle, smaller knee range of motion, and smaller ankle dorsiflexor moment; and scored lower in the single-leg and tandem-leg stance tests.

CONCLUSIONS

Novice high-heeled shoe wearers need to alter their lower-limb joint angles and moments to adjust to high-heeled shoes to achieve balance during gait while carrying an asymmetrical load.

Loading rates in unilateral transfemoral amputees with running-specific prostheses across a range of speeds

BACKGROUND

Understanding the potential risks of running-related injuries in unilateral transfemoral amputees contributes to the development and implementation of the injury prevention programme in running gait rehabilitation. We investigated the vertical ground reaction force loading in unilateral transfemoral amputees who used running-specific prostheses across a range of running speeds.

METHODS

Ten unilateral transfemoral amputees and ten non-amputees performed running trials on an instrumented treadmill at the incremental speeds of 30, 40, 50, and 60% of their maximum acquired speeds. Per-step and cumulative vertical instantaneous loading rates were calculated from the vertical ground reaction force in the affected, unaffected, and non-amputated control limbs.

FINDINGS

Both the per-step and cumulative vertical instantaneous loading rates of the unaffected limbs in runners with unilateral transfemoral amputation were significantly greater than the affected and non-amputated control limbs at all speeds.

INTERPRETATION

The results of the present study suggest that runners with unilateral transfemoral amputation may be exposed to a greater risk of running-related injuries in their unaffected limbs compared to the affected and non-amputated control limbs.

A systematic review of shock-attenuating componentry for lower limb amputees

BACKGROUND

Shock-attenuating pylons are commonly fitted to prostheses in order to compensate for the anatomical and biomechanical shock-absorbing features of the lower limb removed upon amputation. However, studies concerning their shock-attenuating capacity are highly variable and, to date, have not yet been reviewed, making them difficult to interpret and apply in clinical practice.

OBJECTIVES

To synthesise and appraise the available literature examining the effectiveness of shock-attenuating pylons in attenuating shock upon limb loading compared to rigid pylons among lower limb amputees.

STUDY DESIGN

Systematic review.

METHODS

A comprehensive search of seven databases was conducted using search terms concerning amputation level, shock-attenuating and rigid pylons as well as measures of shock attenuation. All studies yielded were screened against established inclusion and exclusion criteria before eligible articles were appraised using the Quality Assessment Standard for Crossover Studies adapted from the Cochrane handbook.

RESULTS

Nine articles were eligible for inclusion. While there was a trend among studies to indicate only a limited positive effect of shock-attenuating pylons in attenuating transient impact forces, limitations to the study designs, namely, in sampling, poor reporting of methodological details and heterogeneity of outcomes made conclusive interpretation of results difficult.

CONCLUSION

While the current body of literature does not reconcile with claims made by manufacturers of shock-attenuating pylons, it is insufficient to conclusively determine how effective shock-attenuating pylons are, in comparison with conventional rigid pylons, in attenuating transient impact forces among lower limb amputees. Higher quality research is required to better guide decisions regarding prescription of shock-attenuating componentry in clinical practice. Clinical relevance When delivered well, research can provide clinicians with objective and reliable data that can be applied in their practice to guide prescription of componentry. However, methodological limitations to research may compromise the reliability of findings, thereby producing potentially misleading outcomes. These limitations must be recognised and appreciated such that findings may be interpreted accurately and applied appropriately.

Running at submaximal speeds, the role of the intact and prosthetic limbs for trans-tibial amputees

BACKGROUND

Dynamic Elastic Response prostheses are designed to absorb and return strain energy in running. Past research has focused on running prostheses with a single toe spring designed for high speeds.

RESEARCH QUESTION

To determine how runners with amputation modulate the ground reaction force of each limb to run at different speeds using a general-purpose dynamic prosthesis which has a heel spring.

METHODS

Overground running data were collected in 16 recreational runners (8 transtibial amputee using their own BladeXT prosthesis and 8 controls) using Vicon Nexus V.2.5 with Kistler force plates. Participants ran at self-selected running pace, 70% and 130% of that pace. Vertical, braking and propulsion peak ground reaction forces and impulses and vertical loading and decay rates were analysed between limbs at each speed (ANOVA) and their association with speed assessed (simple linear regression).

RESULTS

The vertical, braking forces and impulses and propulsive force were significantly less (p < 0.05) on the prosthetic limb than controls at the faster speed, but there was no difference in the propulsive impulse. The intact limb did not evidence increased vertical force at any speed, but experienced increased braking (p < 0.05) compared to both prosthetic limb and controls at the slow speed. For all limbs, braking and propulsive peak forces, decay rate, step length and step frequency were strongly (r > 0.6) and significantly (p < 0.05) associated with speed. On the prosthetic limb vertical impulse was strongly and significantly negatively associated with speed and control's braking impulse was associated with speed.

SIGNIFICANCE

A leg-specific response was found at different speeds. On the prosthetic limb the technique was to brake less not propel more at higher speeds with reduced vertical drive. Running at self-selected speed could be used for fitness without inducing detrimental ground reaction forces on the intact limb or evoking asymmetry in step length and frequency.

Characterisation of the responsive properties of two running-specific prosthetic models

BACKGROUND

The need for information regarding running-specific prosthetic properties has previously been voiced. Such information is necessary to assist in athletes' prostheses selection.

OBJECTIVES

This study aimed to describe the characteristics of two commercially available running-specific prostheses.

STUDY DESIGN

The running-specific prostheses were tested (in an experimental setup) without the external interference of athlete performance variations.

METHODS

Four stiffness categories of each running-specific prosthetic model (Xtend^™ and Xtreme^™) were tested at seven alignment setups and three drop masses (28, 38 and 48 kg). Results for peak ground reaction force (GRF_peak), contact time ( t_c), flight time ( t_f), reactive strength index (RSI) and maximal compression (Δ L) were determined during controlled dropping of running-specific prostheses onto a force platform with different masses attached to the experimental setup.

RESULTS

No statistically significant differences were found between the different setups of the running-specific prostheses. Statistically significant differences were found between the two models for all outcome variables (GRF_peak, Xtend > Xtreme; t_c, Xtreme > Xtend; t_f, Xtreme > Xtend; RSI, Xtend > Xtreme; Δ L, Xtreme > Xtend; p < 0.05).

CONCLUSION

These findings suggest that the Xtreme stores more elastic energy than the Xtend, leading to a greater performance response. The specific responsive features of blades could guide sprint athletes in their choice of running-specific prostheses. Clinical relevance Insights into the running-specific prosthesis (RSP) properties and an understanding of its responsive characteristics have implications for athletes' prosthetic choice. Physiologically and metabolically, a short sprint event (i.e. 100 m) places different demands on the athlete than a long sprint event (i.e. 400 m), and the RSP should match these performance demands.

Impact testing of the residual limb: System response to changes in prosthetic stiffness

Currently, it is unknown whether changing prosthetic limb stiffness affects the total limb stiffness and influences the shock absorption of an individual with transtibial amputation. The hypotheses tested within this study are that a decrease in longitudinal prosthetic stiffness will produce (1) a reduced total limb stiffness, and (2) reduced magnitude of peak impact forces and increased time delay to peak force. Fourteen subjects with a transtibial amputation participated in this study. Prosthetic stiffness was modified by means of a shock-absorbing pylon that provides reduced longitudinal stiffness through compression of a helical spring within the pylon. A sudden loading evaluation device was built to examine changes in limb loading mechanics during a sudden impact event. No significant change was found in the peak force magnitude or timing of the peak force between prosthetic limb stiffness conditions. Total limb stiffness estimates ranged from 14.9 to 17.9 kN/m but were not significantly different between conditions. Thus, the prosthetic-side total limb stiffness was unaffected by changes in prosthetic limb stiffness. The insensitivity of the total limb stiffness to prosthetic stiffness may be explained by the mechanical characteristics (i.e., stiffness and damping) of the anatomical tissue within the residual limb.