Thomas J. Withrow

Preliminary Evaluations of a Self-Contained Anthropomorphic Transfemoral Prosthesis

This paper presents a self-contained powered knee and ankle prosthesis, intended to enhance the mobility of transfemoral amputees. A finite-state based impedance control approach, previously developed by the authors, is used for the control of the prosthesis during walking and standing. Experiments on an amputee subject for level treadmill and overground walking are described. Knee and ankle joint angle, torque, and power data taken during walking experiments at various speeds demonstrate the ability of the prosthesis to provide a functional gait that is representative of normal gait biomechanics. Measurements from the battery during level overground walking indicate that the self-contained device can provide more than 4500 strides, or 9 km, of walking at a speed of 5.1 km/h between battery charges.

The Relationship Between Quadriceps Muscle Force, Knee Flexion, and Anterior Cruciate Ligament Strain in an In Vitro Simulated Jump Landing

Background An instrumented cadaveric knee construct was used to quantify the association between impact force, quadriceps force, knee flexion angle, and anterior cruciate ligament relative strain in simulated unipedal jump landings. Hypothesis Anterior cruciate ligament strain will correlate with impact force, quadriceps force, and knee flexion angle. Study Design Descriptive laboratory study. Methods Eleven cadaveric knees (age, 70.8 [19.3] years; 5 male; 6 female) were mounted in a custom fixture with the tibia and femur secured to a triaxial load cell. Quadriceps, hamstring, and gastrocnemius muscle forces were simulated using pretensioned steel cables (stiffness, 7 kN/cm), and the quadriceps tendon force was measured using a load cell. Mean strain on the anteromedial bundle of the anterior cruciate ligament was measured using a DVRT. With the knee in 25° of flexion, the construct was vertically loaded by an impact force initially directed 4 cm posterior to the knee joint center. Tibiofemoral kinematics was measured using a 3D optoelectronic tracking system. Results The increase in anterior cruciate ligament relative strain was proportional to the increase in quadriceps force (r2 = 0.74; P <. 00001) and knee flexion angle (r2 = 0.88; P <. 00001) but was not correlated with the impact force (r2 = 0.009; P =. 08). Conclusion The increase in knee flexion and quadriceps force during this simulated 1-footed landing strongly influenced the relative strain on the anteromedial bundle of the anterior cruciate ligament. Clinical Relevance These results suggest that even in the presence of knee flexor muscle forces, the increase in quadriceps force required to prevent the knee from flexing during landing can place the anterior cruciate ligament at risk for large strains.

Design of a Multifunctional Anthropomorphic Prosthetic Hand With Extrinsic Actuation

This paper presents an anthropomorphic prototype hand prosthesis that is intended for use with a multiple-channel myoelectric interface. The hand contains 16 joints, which are differentially driven by a set of five independent actuators. The hand prototype was designed with the minimum number of independent actuators required to provide a set of eight canonical hand postures. This paper describes the design of the prosthesis prototype, demonstrates the hand in the desired eight canonical postures, and experimentally characterizes the force and speed capability of the device. A video is included in the supplementary material that also illustrates the functionality and performance of the hand.

Self-contained powered knee and ankle prosthesis: Initial evaluation on a transfemoral amputee

This paper presents an overview of the design and control of a fully self-contained prosthesis, which is intended to improve the mobility of transfemoral amputees. A finite-state based impedance control approach, previously developed by the authors, is used for the control of the prosthesis during walking and standing. The prosthesis was tested on an unilateral amputee subject for over-ground walking. Prosthesis sensor data (joint angles and torques) acquired during level ground walking experiments at a self-selected cadence demonstrates the ability of the device to provide a functional gait similar to normal gait biomechanics. Battery measurements during level ground walking experiments show that the self-contained device provides over 4,500 strides (9.0 km of walking at a speed of 5.1 km/h) between battery charges.

Design and control of an active electrical knee and ankle prosthesis

This paper presents an overview of the design and control of an electrically powered knee and ankle prosthesis. The prosthesis design incorporates two motor-driven ball screw units to drive the knee and ankle joints. A spring in parallel with the ankle motor unit is employed to decrease the power consumption and increase the torque output for a given motor size. The devicepsilas sensor package includes a custom load cell to measure the sagittal socket interface moment above the knee joint, a custom sensorized foot to measure the ground reaction force at the heel and ball of the foot, and commercial potentiometers and load cells to measure joint positions and torques. A finite-state based impedance control approach, previously developed by the authors, is used and experimental results on level treadmill walking are presented that demonstrate the potential of the device to restore normal gait. The experimental power consumption of the device projects a walking distance of 5.0 km at a speed of 2.8 km/hr with a lithium polymer battery pack.

Design of a Bone-Attached Parallel Robot for Percutaneous Cochlear Implantation

Access to the cochlea requires drilling in close proximity to bone-embedded nerves, blood vessels, and other structures, the violation of which can result in complications for the patient. It has recently been shown that microstereotactic frames can enable an image-guided percutaneous approach, removing reliance on human experience and hand-eye coordination, and reducing trauma. However, constructing current microstereotactic frames disrupts the clinical workflow, requiring multiday intrasurgical manufacturing delays, or an on-call machine shop in or near the hospital. In this paper, we describe a new kind of microsterotactic frame that obviates these delay and infrastructure issues by being repositionable. Inspired by the prior success of bone-attached parallel robots in knee and spinal procedures, we present an automated image-guided microstereotactic frame. Experiments demonstrate a mean accuracy at the cochlea of 0.20 ± 0.07 mm in phantom testing with trajectories taken from a human clinical dataset. We also describe a cadaver experiment evaluating the entire image-guided surgery pipeline, where we achieved an accuracy of 0.38 mm at the cochlea.

A Gas-Actuated Anthropomorphic Prosthesis for Transhumeral Amputees

This paper presents the design of a gas-actuated anthropomorphic arm prosthesis with 21 degrees of freedom and nine independent actuators. The prosthesis utilizes the monopropellant hydrogen peroxide as a gas generator to power nine pneumatic type actuators. Of the nine independent actuators, one provides direct- drive actuation of the elbow, three provide direct-drive actuation for the wrist, and the remaining five actuate an underactuated 17 degree of freedom hand. This paper describes the design of the prosthesis, including the design of small-scale high-performance servovalves, which enable the implementation of the monopropellant concept in a transhumeral prosthesis. Experimental results are given characterizing both the servovalve performance and the force and/or motion control of various joints under closed-loop control.

Design of a multifunctional anthropomorphic prosthetic hand with extrinsic actuation

This paper presents an anthropomorphic prototype hand prosthesis that is intended for use with a multiple channel myoelectric interface. The hand contains 16 joints, which are differentially driven by a set of five independent actuators. The hand prototype was designed with the minimum number of independent actuators required to provide a set of eight canonical hand postures. This paper describes the design of the prosthesis prototype, demonstrates the hand in the desired eight canonical postures, and experimentally characterizes the force and speed capability of the device. A video is included in the supplemental material that also illustrates the functionality and performance of the hand.

Design and simulation of a joint-coupled orthosis for regulating FES-aided gait

A hybrid functional electrical stimulation (FES)/orthosis system is being developed which combines two channels of (surface-electrode-based) electrical stimulation with a computer-controlled orthosis for the purpose of restoring gait to spinal cord injured (SCI) individuals (albeit with a stability aid, such as a walker). The orthosis is an energetically passive, controllable device which 1) unidirectionally couples hip to knee flexion; 2) aids hip and knee flexion with a spring assist; and 3) incorporates sensors and modulated friction brakes, which are used in conjunction with electrical stimulation for the feedback control of joint (and therefore limb) trajectories. This paper describes the hybrid FES approach and the design of the joint coupled orthosis. A dynamic simulation of an SCI individual using the hybrid approach is described, and results from the simulation are presented that indicate the promise of the JCO approach.

Design of a joint-coupled orthosis for FES-aided gait

A hybrid functional electrical stimulation (FES)/orthosis system is being developed which combines two channels of (surface-electrode-based) electrical stimulation with a computer-controlled orthosis for the purpose of restoring gait to spinal cord injured (SCI) individuals (albeit with a stability aid, such as a walker). The orthosis is an energetically passive, controllable device which 1) unidirectionally couples hip to knee flexion; 2) aids hip and knee flexion with a spring assist; and 3) incorporates sensors and modulated friction brakes, which are used in conjunction with electrical stimulation for the feedback control of joint (and therefore limb) trajectories. This paper describes the hybrid FES approach and the design of the joint coupled orthosis. Preliminary experiments are presented which test the joint coupling concept and assess the extent of quadriceps fatigue imposed by the bias spring and joint coupling.