Chimba Mkandawire

Applications of UHMWPE in Total Ankle Replacements

Publisher Summary This chapter provides a historical overview of the total ankle replacement (TAR). The anatomy and biomechanics of the ankle are reviewed and an in-depth description of early-generation and contemporary TAR designs is provided, with a focus on the ultra-high molecular weight polyethylene (UHMWPE) component of each design. UHMWPE wear in TAR is also considered and available data related to clinical complications and retrieval analysis of the UHMWPE components are reviewed in this study. It explains that the foot and ankle complex comprises 26 bones within the foot, which are nonsesamoid bones, two bones of the lower leg, and approximately 109 ligament and fascicle groups spanning these 28 bones. The goal of a TAR design should be to mimic the ankle joint as closely as possible. Specifically, a suitable range of motion should be available to allow for proper gait patterns and other activities of daily living. TAR designs are expected to have a reproducible surgical technique, minimal bone resection, rapid and adequate bone in growth, minimal constraint and replication of physiological ankle motion, and pain relief. Relevant to the UHMWPE components, the design should also offer minimal complications and need for early revision, as well as long-term survivorship.

Chapter 11 – Applications of UHMWPE in Total Ankle Replacements

Publisher Summary This chapter provides a historical overview of the total ankle replacement (TAR). The anatomy and biomechanics of the ankle are reviewed and an in-depth description of early-generation and contemporary TAR designs is provided, with a focus on the ultra-high molecular weight polyethylene (UHMWPE) component of each design. UHMWPE wear in TAR is also considered and available data related to clinical complications and retrieval analysis of the UHMWPE components are reviewed in this study. It explains that the foot and ankle complex comprises 26 bones within the foot, which are nonsesamoid bones, two bones of the lower leg, and approximately 109 ligament and fascicle groups spanning these 28 bones. The goal of a TAR design should be to mimic the ankle joint as closely as possible. Specifically, a suitable range of motion should be available to allow for proper gait patterns and other activities of daily living. TAR designs are expected to have a reproducible surgical technique, minimal bone resection, rapid and adequate bone in growth, minimal constraint and replication of physiological ankle motion, and pain relief. Relevant to the UHMWPE components, the design should also offer minimal complications and need for early revision, as well as long-term survivorship.

Foot Injury Patterns With Protective Footwear After Lift Truck Impact

The objective of this study was to evaluate the properties and kinematics of an ASTM steel toe cage during quasi-static loading and forklift runover. Example ASTM F2413-05-compliant steel-toed shoes were loaded via forklift and via mechanical test device, and examined visually for external damage and fluoroscopically for internal displacement and damage of the steel-toed cage. Resulting displacement was quantified and analyzed to assess likely foot injuries and their location sustained by the wearer. When loaded by a lift truck, an ASTM F2413-05-compliant steel toe supported the weight without crushing, but the structure of the shoe around the steel cup did not, causing the steel toe to rotate and translate fore-aft or laterally, depending on the direction of loading. The survival of the steel toe combined with the failure of the shoe around it may lead to sparing of the toes, with crushing of the distal midfoot due either to direct or induced loading of the foot. Steel-toed shoes are unlikely to prevent injury to the midfoot or proximal phalanges when loaded by a forklift.Copyright

Biomechanical, Perceptual, and Cognitive Factors Involved in Maintaining Postural Control While Standing or Walking on Non-Moving and Moving Surfaces: A Literature Review

Postural control has been defined as “regulating the body’s position in space for the dual purposes of stability and orientation.” How the body achieves postural control depends, in part, on the environment. A person navigating a non-moving surface (e.g. hallway, stairway, or step ladder) will process information and will employ different strategies to maintain postural control than someone who is standing or walking on a moving surface (e.g., forklifts, personal transportation systems, escalators, and moving walkways). In both environments, sensory, cognitive, and motor control systems contribute to postural control. The musculoskeletal system uses muscle activation and joint positioning to control the body’s alignment and muscle tone. The biomechanics of postural control rely on information that the musculoskeletal system receives from sensory systems including the vestibular system, which is generally implicated in behaviors requiring balance control, as well as the somatosensory and visual systems. Furthermore, sensory information from these and other systems can be enhanced by cognitive processes, such as attention. The ability to maintain postural control while standing or walking is critical in preventing falls on both non-moving and moving surfaces. This review focuses on moving surfaces and includes a discussion of the biomechanical, perceptual, and cognitive factors responsible for postural control.Copyright

Biomechanical, Perceptual, and Cognitive Factors Involved in Balance Recovery Following Unexpected Perturbations: A Literature Review

For an individual standing or walking on a moving or non-moving surface, perturbations can result in postural instability and sudden loss of balance. When unexpected perturbations occur, specific mechanisms involving the sensory, cognitive, and motor systems activate in order to regain postural control. For example, specific muscle synergies can result in compensatory limb movements (e.g. stepping or reaching towards a fixed object) that are prevalent mechanical responses to sudden loss of balance and play a crucial role in preventing falls. These movements require the interaction of multiple sensory systems including the visual, somatosensory, and vestibular systems. If sensory information is unavailable or incomplete, there may be a greater reliance on cognitive processes such as memory and attention in order to execute a balance-recovering mechanical response; however, if cognitive processes are tasked, compensatory responses may be negatively affected. The ability to recover from sudden loss of balance is critical in preventing falls on both non-moving and moving surfaces. This review includes a discussion of the biomechanical, perceptual, and cognitive factors responsible for the control of balance recovery on moving surfaces.Copyright

HEAD MOTION IN THE CORONAL PLANE DURING LOW-SPEED LATERAL IMPACT COLLISIONS

INTRODUCTION Although numerous studies have been done on frontal and rear impact collisions and the resulting occupant kinematics, relatively few have considered the effects of lateral impacts on occupant kinematics. Understanding the kinematics of the head during lateral impacts can assist in determining how the passive response of the human body relate to one another when presented with such a stimulus. This information is invaluable in the design of motor vehicle safety systems, amusement park rides, and other situations where an unexpected lateral impact may occur.