Altered mechanics and increased loading on intact limbs of individuals with a unilateral transtibial amputation in comparison with non-amputees during a start-stop task.

Individuals with a unilateral transtibial amputation (ITTA) often experience greater loading on the intact limb during running and stepping tasks compared to individuals without amputation. This study aimed to investigate the mechanics of load absorption in the intact limb of ITTA and determine if increased ground reaction forces (GRF) persist during a start-stop task which (i) controlled touch-down velocity and (ii) removed the requirement for on-going locomotion. Data were collected using a twelve-camera motion capture system with two Kistler force platforms. Variables were extracted during the final loading phase of a 2-step start-stop task. The intact limb of ITTA and the dominant limb of able-bodied controls were compared using independent t-tests and effect size analysis. ITTA showed lower knee flexion angles at touchdown (p = 0.007, g = -1.43), and peak vertical GRF (p = 0.01, g = -1.33) compared to control subjects. ITTA also exhibited less hip (p = 0.14, g = 0.76) and ankle (p = 0.002, g = 1.82) absorptive power at touchdown and at peak vertical GRF (hip: p = 0.01, g = 1.23; ankle: p = 0.05, g = 0.97). ITTA exhibited greater peak vertical GRF (p = 0.01, g = 1.30) and braking GRF (p = 0.05, g = -0.96) on the intact limb compared to the controls. Our results indicate altered joint mechanics through the intact limb of ITTA are independent of the touchdown conditions or the need for ongoing locomotion. These altered joint mechanics increased loading experienced by the intact limb. Further work should be conducted examining a variety of other dynamic movements to fully understand the involved mechanics, so that intervention studies can be developed to reduce the load experienced by ITTA.

Dynamic elastic response prostheses alter approach angles and ground reaction forces but not leg stiffness during a start-stop task.

In a dynamic elastic response prosthesis (DERP), spring-like properties aim to replace the loss of musculature and soft tissues and optimise dynamic movement biomechanics, yet higher intact limb (IL) loading exists. It is unknown how amputees wearing a DERP will perform in start-stop movements and how altering the prosthetic stiffness will influence the performance and loading. This study assessed movement dynamics through comparisons in spatiotemporal, kinematic and kinetic variables and leg stiffness of intact, prosthetic and control limbs. The effect of prosthetic stiffness on movement dynamics was also determined. Eleven male unilateral transtibial amputees performed a start-stop task with one DERP set at two different stiffness - Prescribed and Stiffer. Eleven control participants performed the movement with the dominant limb. Kinematic and kinetic data were collected by a twelve-camera motion capture system synchronised with a Kistler force platform. Selected variables were compared between intact, prosthetic and control limbs, and against prosthetic stiffness using ANOVA and effect size. Pearson's Correlation was used to analyse relationship between leg stiffness and prosthetic deflection. Amputees showed a more horizontal approach to the bound during the start-stop movement, with lower horizontal velocities and a longer stance time on the IL compared to controls. In both stiffness conditions, the IL showed selected higher anteroposterior and vertical forces and impulses when compared to the controls. Leg stiffness was not significantly different between limbs as a result of the interplay between angle swept and magnitude of force, even with the change in prosthetic stiffness. A main effect for prosthetic stiffness was found only in higher impact forces of the prosthetic limb and more horizontal touchdown angles of the IL when using the prescribed DERP. In conclusion, amputees achieve the movement with a horizontal approach when compared to controls which may reflect difficulty of movement initiation with a DERP and a difficulty in performing the movement dynamically. The forces and impulses of the IL were high compared to control limbs. The consistent leg stiffness implies compensation strategies through other joints.

Scoliosis: lower limb asymmetries during the gait cycle.

BACKGROUND: Several studies indicate that the gait pattern of subjects suffering from scoliosis differs from the norm. However, there is conflicting evidence regarding the source of this discrepancy. OBJECTIVE: To evaluate lower limb asymmetries in selected gait variables. STUDY DESIGN: A case-control study on lower limb asymmetries during gait which can be related to scoliosis. METHODS: 31 subjects with scoliosis (Study Group - SG) and an equal comparative control sample (Control Group - CG) of subjects underwent objective gait analysis with the Vicon® motion caption system whilst walking at a comfortable speed along the gait laboratory walkway. Analysis was performed at three levels: (1) Asymmetry in the SG against asymmetry in the CG, (2) Difference in magnitude of asymmetry between the SG and CG, and (3) Global mean values in the SG vs. CG. The Paired Student T-Test was used for intra-group analysis whilst the Independent Student T-Test was used for inter-group analysis of the selected parameters, which include temporal parameters (stride length, stride time, step length, individual step speed, speed of gait, cadence, swing-to-stance ratio), ground reaction force (peak GRF values during Loading and Propulsion phases, vertical component only) and electromyography (peak EMG values and their time of onset, as a percentage of the gait cycle) of two lower limb muscles (Gastronemius and Vastus Medialis). RESULTS: No intra-group variation was found to be significant. However, the speed of gait was found to be significantly slower (p = 0.03) in scoliotic subjects when compared to the norm, as a result of the shorter stride length (p = 0.002 and longer stride time (p = 0.001) in the SG. Furthermore, there was statistical significance in the time of onset of EMG peaks for the Lateral Gastrocnemius (p = 0.02) with regards to inter-group difference in magnitude of lower limb asymmetry and global mean values. CONCLUSIONS: Scoliosis is a tri-planar deformity which has some impact on the gait pattern. This research study concludes that scoliotic subjects have a slower speed of gait due to a shorter stride length and a longer stride time, together with variations in the timing of muscle activation.