Relationship of spasticity to knee angular velocity and motion during gait in cerebral palsy.

This study investigated the effects of spasticity in the hamstrings and quadriceps muscles on gait parameters including temporal spatial measures, knee position, excursion and angular velocity in 25 children with spastic diplegic cerebral palsy (CP) as compared to 17 age-matched peers. While subjects were instructed to relax, an isokinetic device alternately flexed and extended the left knee at one of the three constant velocities 30 degrees/s, 60 degrees/s and 120 degrees/s, while surface electromyography (EMG) electrodes over the biceps femoris and the rectus femoris recorded muscle activity. Patients then participated in 3D gait analysis at a self-selected speed.

Biomechanical changes in gait following selective dorsal rhizotomy.

Object: The purpose of this study was to evaluate the effects of selective dorsal rhizotomy (SDR) on the walking pattern of children with cerebral palsy (CP). The authors hypothesized that SDR would reduce the overactive stretch reflex and result in improved joint positions, greater joint angular velocities and motion, and greater strides. The authors also expected that the changes from the SDR would be reflected in the electrical activities of the muscles.

Ankle and knee coupling in patients with spastic diplegia: effects of gastrocnemius-soleus lengthening.

Background: Empirical observations of subjects with an equinus gait have suggested that there is coupled motion between the ankle and knee such that, during single-limb stance, the ankle moves into equinus as the knee extends. Since the gastrocnemius-soleus muscle-tendon unit spans both joints, we hypothesized that this muscle-tendon unit may be responsible for the coupling and that lengthening of the gastrocnemius-soleus muscle alone would result in greater ankle dorsiflexion as well as greater knee extension in single-limb stance, effectively uncoupling these joints. The concept that gastrocnemius-soleus lengthening may promote knee extension is counter to the popular notion that crouch gait may result if the hamstrings are not lengthened concomitantly.

Biomechanical efficacy of an internal fixator for treatment of distal radius fractures.

Despite the effectiveness of external fixation in the treatment of complex wrist fractures, the complication rate for this modality ranges from 20% to 62%. Common complications are related to the use of percutaneous metal pins and result in an average reoperation rate of 16%. In addition, external fixation is unable to prevent dorsal collapse of the radius or maintain the normal palmar tilt of the radiocarpal joint surface.

Biomechanical evaluation of early fracture healing in normal and diabetic rats.

Diabetes mellitus has been shown to alter the properties of bone and impair fracture healing in both humans and animals. The objective of this study was to document changes in the structural and material properties of intact bone and bone with healed fractures in diabetic rats compared with nondiabetic controls after 3 and 4 weeks of healing. Rods were inserted in the right femurs of control rats and rats with streptozotocin-induced diabetes, and the femurs were fractured in a standardized procedure and then allowed to heal for 3 and 4 weeks.

Rate-independent characteristics of an arthroscopically implantable force probe in the human achilles tendon.

The effect of loading rate on specimen calibration was investigated for an implantable force sensor of the two-point loading variety. This variety of sensor incorporates a strain gage to measure the compressive load applied to the sensor due to tensile loading in a soft tissue specimen. The Achilles tendon in each of four human cadaveric lower extremities was instrumented with a force sensor and then loaded in tension using a materials testing machine.

Physiologic bowing in children: an analysis of the pendulum mechanism.

Prompted by common observations, we investigated why physiologic bowing occurs in infants and what purpose is served by its characteristic varus to valgus to neutral movement of the mechanical axis of the knee which we term "pendulum-like swing" in the frontal plane. Anthropomorphic data were readily available on age-related increase in weight, femoral and tibial lengths, and changes in lower extremity to allow construction of an "average" leg representing "normal" limb alignment of a growing infant male aged 1-8 years. This enabled us to calculate the bending moments on five anatomic levels of the limb about the knee; more important, during some growth periods the bending moments are minimal and may be used to diagnose pathologies of the lower limb.

Forces and moments on the human leg in the frontal plane during static bipedal stance.

An experimental apparatus was assembled that permitted measurement of the vertical and lateral ground reaction forces as the hip is abducted, resulting in foot separations ranging from 0.25 to 71 cm, with the knee in 0 degree flexion. Twelve healthy volunteers (8 men and 4 women) were tested.

A piece-wise non-linear elastic stress expression of human and pig coronary arteries tested in vitro.

Eight human and nineteen pig unembalmed proximal left anterior descending and circumflex coronary arteries were subjected to linear volume changes (2 s ramp time) at three fixed axial extensions while immersed in a physiological saline bath at body temperature. Measured parameters included: lumen pressure, outside diameter, axial force, and axial extension. The deformations were measured using a video dimensional analyzer.

Effects of ankle taping on the motion and loading pattern of the foot for walking subjects.

Gait analysis was used to compare the ground reaction forces, ankle and foot rotations in the sagittal plane, and the center of pressure pattern beneath the right feet of seven normal subjects walking barefoot, with and without their right ankles taped in the neutral position. Instrumentation included a force plate, ankle goniometer, and two accelerometers mounted on top of the foot. The ground reaction forces showed no changes between the same ankle, taped and untaped.