The concept of a leaf spring structured midsole shoe (LEAF) is based on shifting the foot anteriorly during the first part of stance phase in heel-toe running. The aim of the current study is to analyze the effects of a LEAF compared to a standard foam midsole shoe (FOAM) on the foot kinematics in overground and treadmill running at two running speeds.
Nine male heel strikers ran on a treadmill with the LEAF and the FOAM at 3 and 4 m/s, each for 5 min. Furthermore, the participants performed with both shoes six runs each on a 40 m indoor track at running speeds of 3 and 4 m/s. For one stance phase the ground reaction forces were measured using a force plate imbedded in the track. Running speed and shoe order were randomized. Kinematics (VICON, 200Hz) and kinetics (AMTI, 1000Hz; only overground) were used to calculate the anterior shift of the foot, the foot ground angle at heel strike (FGA at HS) and the horizontal path of the center of pressure (COP).
The LEAF increases the anterior foot shift in treadmill and overground running at both running speeds compared to the FOAM, without changing the individuals’ strike pattern. Furthermore, the anterior foot shift affects the COP leading to an overall enlarged COP path. These findings indicate a benefit of the structured midsole on performance at least at moderate running speeds
For lower limb amputees graded walking imposes a high level of motor ability, due to the missing proprioceptive feedback of the limb, and the necessary compensation mechanisms. In order to facilitate gait a focus in prosthesis research is the development of the prostheses ankle joints from rigid to moveable. Therefore, the aim of this case study was to analyse the effects of three different prostheses with a rigid and a moveable ankle joint during graded walking of a unilateral amputee.
One male unilateral transfemoral amputee was recruited for this study and a comparison of following three prostheses (endolite, Germany) was performed: Elan (movable ankle joint with flexible resistance), Echelon (movable ankle joint with steady resistance) and Esprit (rigid ankle joint). Kinematic (12 cameras, Vicon, UK, 250 Hz) and kinetic (2 force plates, AMTI, MA, 1000 Hz) data were recorded during self-paced walking on a 6 m ramp, which was set to the inclinations of -12°, -4°, 0°, 4° and 12°. Following gait parameters, ground reaction forces, joint angles and joint moments were calculated.
Gait parameters, ground reaction forces and joint angles were marginally influenced by the different prosthetic designs, but major changes occurred on the joint moment level. The use of the rigid ankle prosthesis Esprit induced up to 10 times higher joint moments compared to the moveable ankle joint prostheses. This case study showed that a moveable ankle joint can reduce the joint moments during graded walking, which might be advantageous to use for transfemoral amputees in graded walking.
Background: Patellofemoral pain (PFP) is a common condition seen in orthopedic practice. A commonly cited hypothesis as to the cause of PFP is increased patellofemoral joint (PFJ) stress secondary to abnormal lower extremity kinematics (ie. excessive hip internal rotation and knee valgus). However, the influence of these motions on PFJ contact mechanics is unknown.
Purpose: To assess the influence of hip rotation and knee valgus on PFJ stress using finite element (FE) analysis.
Methods: Patella cartilage stress profiles for a healthy participant were quantified utilizing a subject-specific FE model. Input parameters included: joint geometry, quadriceps muscle forces, and weight-bearing PFJ kinematics. Using a nonlinear FE solver, quasi-static loading simulations were performed to quantify patella cartilage stress during a static squatting maneuver (45° knee flexion). To simulate hip rotation (0-8°) and knee valgus (0-12°), the femur and tibia were rotated in the transverse and frontal plane respectively in 2° increments.
Results: Increasing hip rotation resulted in a linear increase in patella cartilage stress. In contrast, increasing knee valgus resulted in a decrease in patella cartilage stress. The combination of hip rotation and knee valgus did not result in higher PFJ cartilage stress compared to isolated hip rotation.
Conclusions: Patella cartilage stress appears to be influenced to a greater degree by hip internal rotation as opposed to knee valgus. Surprisingly, higher degrees of knee valgus resulted in decreased cartilage stress (in the absence of hip rotation). Our finding supports the premise that persons exhibiting excessive hip internal rotation may be pre-disposed to elevated patella cartilage stress.