Lumbar neurogenic claudication secondary to spinal stenosis causes narrowing of the spinal canal that contributes to extremity lower back pain. Lumbar extension, as seen in standing and walking, exacerbates symptoms by decreasing the foraminal height, width, and area, whereas flexion, as seen in sitting, improves symptoms by increasing the cross-sectional area of the foramen. Interspinous process devices have been developed to treat symptomatic lumbar stenosis [1]. The device is placed between the spinous processes and serves to limit the amount of extension that can occur beyond a neutral alignment. The objective of this study was to perform low endurance cyclic tests on the In-Space spinous process spacer (Synthes Spine) to assess fixation and containment in a human cadaveric spine model in vitro. The device was cyclically tested under an alternating sequence of combined loading conditions using a new protocol developed on a robotic based spinal testing system (Spine Robot).

Current in vitro testing methodologies remain limited in the ability to explore spinal dynamics. The gold standard of flexibility testing has traditionally focused on evaluating MSU rotational ranges of motion only. While such data may be applied towards evaluation of the Instantaneous Axis of Rotation (IAR), many systems lack the needed sensitivity. The result is that there is currently no consensus on the location of the IAR. Further, very limited data or insight can be gathered as to the precise kinematic or dynamic state of the MSU, or the influence of surgically implanted motion restoration devices. For example, total disc arthroplasty devices are typically rigid mechanical devices that impose an IAR or IAR range. How might this imposed IAR affect MSU mechanics? How might variations in surgical placement of an implant be scientifically quantified? More recently an emerging group of compliant motion restoration devices are being developed that require new methods of evaluation. How well does a compliant device restore the native mechanics of the disc or MSU? To address and understand these increasingly important issues, novel, more advanced biomechanical testing protocols need to be developed.

In this paper we describe the implementation of a system that gives assistive force feedback to the remote user in a teleoperation based environment. The force feedback would help the user in trajectory following exercises for stroke rehabilitation. Exercises in virtual environments on a PC as well as real world exercises with a remote robotic arm, that would follow a trajectory in real-time as the user moves the master device, could be performed. Such real world exercises augmented with real-time force feedback can make the exercises more effective as the user gets force assistance along the desired path. Moreover, the system can find its application in remote therapy, where the therapist is away from the user, as it can be teleoperated and has internet based protocols. The assistive force feedback has been implemented using simple sensors such as the camera and the laser and a PC-based real-time multithreaded control system. The real-time force feedback from the remote robot to the master device has been possible using effective multithreading programming strategies in the control system design and novel sensor integration. The system also has the capabilities of autonomous as well as supervisory control of the remote robot and is modular as far as integration of different master devices for stroke rehabilitation exercises is concerned.

One of the primary goals of medical micro and nano robots is to reach currently inaccessible areas of the human body and carry out a host of complex operations, such as minimally invasive surgery (MIS), highly localized drug delivery, and screening for diseases at their very early stages. One of the innovative approaches to design microrobot propulsion is based on the flagellar motion of bacteria [1]. Certain bacteria, such as Escherichia coli ( E.coli ) use multiple flagella often concentrated at one end of their bodies to induce locomotion. Each flagellum is formed in a left-handed helix and has a motor at the base that rotates the flagellum in a corkscrew motion. As pointed out by Purcell in his Lecture “Life at low Reynolds numbers” [2], microorganisms experience an environment quite different from our own. In particular, because of their small size (of the order of microns), inertia is, to them, essentially irrelevant. The fact that inertia is irrelevant for micro-organisms makes it difficult for them to move. The propulsive mechanisms based on flow inertia will not work on a mesoscopic scale. To overcome this problem, organisms living in low Reynolds number regimes have developed moving organelles which have a handedness to them. For instance, E. Coli ’s flagella rotate with a helical motion, much like a corkscrew. This configuration produces patterns of motion that do not repeat the first half of the cycle in reverse for the second half, allowing the organisms to achieve movement in their environment.

Bone is a living tissue which is continually adapting to its biological environment via continuous formation and resorption. It is generally accepted that bone remodeling occurs in response to daily mechanical loading. The remodeling process enables various functions, such as damage repair, adaptation to mechanical loads, and mineral homeostasis [1]. The cells that are responsible for the bone remodeling process are the bone resorbing osteoclasts and the bone forming osteoblasts. These cells closely coordinate their actions in a basic multicellular unit to renew “packets” of bone.

Bistable structures, exemplified by the Venus flytrap [1] and slap bracelets (see Fig. 1), can tranform quickly from one functional shape to the other upon mechanical actuation. Potential applications can be found in mechanical/electromechanical devices from bio-inspired robots to deployable aerocraft wings. Related challenges emerged include theoretically modeling the spontaneous curving and buckling of thin objects such as leaves, flowers, nanohelices, nanoscrolls and flexible electronics [2, 3]. Despite the significant modeling efforts about such large deformation of shell structures [4, 5], the nonlinear geometric effects remain poorly understood. Here we present a continuum elasticity theory that incorporates geometric nonlinearity for large deformation of shells, and investigates, through both theoretical analysis and table-top experiments, the geometric and mechanical conditions for bistability, and the role of edge effects. Our work classifies the conditions for bistability, defines the design space for bistable morphing structures, and extends the theory of plates and shells with large deformation. A mechanical framework is provided for analyzing morphogenesis associated with growth and instability, which will also facilitate the design of multistable structures, from bio-inspired robots to deployable structures in aerospace applications.

Passive knee kinematics and kinetics following total knee replacement (TKR) are dependent on the topology of the component joint surfaces as well as the properties of the passive soft tissue structures (ligaments and capsule). Recently, explicit computer models have been used for the prediction of knee joint kinematics based on experimental investigations [1]. However, most of these models replicate experimental knee simulators [2], which simulate soft tissue structures using springs or elastomeric structures. New generations of experimental setups deploy industrial robots for measuring kinematics and kinetics in six degrees of freedom as well as the contribution of soft tissue structures. Based on these experiments, accurate soft tissue properties are available for use in computer models to aid more realistic predictions of kinematics. Final evidence of the quality of the kinematic predictions from these computer models can be provided by direct validation of the models against experimental data. Therefore, the objective of this study was to use in vitro robotic test data to develop, verify, and validate specimen specific virtual models suitable for predicting laxity and kinematics of the reconstructed knee.

This work deals with neural network-based gait-pattern adaptation algorithm for an active orthosis. The proposed device is developed for lower limbs and based on a commercially available orthosis, Figure 1. Active orthoses can be designed for helping physically weak or injured people during rehabilitation procedures [1]. The robotic orthosis Lokomat is being recently used for rehabilitation of patients with stroke or spinal cord injury individuals [2]. Gait-pattern adaptation algorithms are proposed by Riener, et. al [3], considering the human-machine interaction. The algorithms in Riener, et. al [3] were developed for a fixed base robotic system; they can not be applied directly in the proposed orthosis, since no stability of the gait pattern is considered. A trajectory generator for biped robots taking into account the ZMP (Zero Moment Point) criterion is presented in Huang, et al. [4]. This method presents suitable results with smooth and second-order differentiable curves.

A standard biomechanical testing protocol for evaluation of the sub-axial cervical spine is the application of pure bending moments to the free end of the spine (with opposing end fixed) and measurement of its motion response. The pure moment protocol is often used to compare spinal fusion instrumentation and has also been used to evaluate non-fusion instrumentation (e.g. disc arthroplasty devices) [1,2]. A variety of different testing systems have been employed to implement pure moment application. In cases where the loading is applied quasi-statically using a series of weights and pulleys the spine may relax between intermittent loading phases and/or unintended loading may be applied causing experimental artifact. Our objective was to use an existing programmable robotic testing platform (Spine Robot) to develop a novel real time force control strategy to simulate pure moment loading under precisely controlled continuous movement conditions. This would serve to advance robotic testing capabilities with an end goal to simulate different protocols in the same platform, and to potentially minimize fixturing and quasi-static artifacts.

The concept of passive dynamic walking and running [5] has demonstrated that a simple passive model can represent the dynamics of whole-body human locomotion. Since then, many passive models were developed and studied: [3,1,2,11]. The later developed Spring-Loaded Inverted Pendulum (SLIP) [1, 4, 11, 2] exhibits stable center of mass (CoM) motions just by resetting the landing angle at each touch down. Also, compared to SLIP, a SLIP-like model with simple flight leg control is better at resisting perturbations of the angle of velocity but not the magnitude [11, 2, 7]. Energy conserving models explain much about whole-body locomotion. Recently, there has been investigations of modified spring-mass models capable of greater stability, like that of animals and robots [9, 10, 8, 12]. Inspired by RHex [6], the Clock-Torqued Spring-Loaded Inverted Pendulum (CT-SLIP) model [9] was developed, and has been used to explain the robust stability of animal locomotion [12]. Here we present a model (mechanism) simpler than CT-SLIP called Forced-Damped SLIP (FD-SLIP) that can attain full asymptotically stability of the CoM during locomotion, and is capable of both walking and running motions. The FD-SLIP model, having fewer parameters, is more accessible and easier to analyze for the exploration and discovery of principles of legged locomotion.

In vitro testing provides a critical tool for understanding the biomechanics of the subaxial cervical spine. Previous common testing protocols used to evaluate the subaxial cervical spine include pure moment, follower load, and eccentric lever arm (EL) loading methods [1,2,3]. Although these methods are widely accepted, there is always a goal to try to better simulate physiologic loading conditions. While the follower load attempts to simulate compression due to muscle activation, no previous protocol has taken into account the constant vertical force vector applied to C2 produced by the weight of the human head. Furthermore, we are unaware of previous direct protocol to protocol comparisons using the same testing platform and test specimens. Our multi-axis programmable robotic testing platform (Spine Robot) provides the means to explore such comparisons. The objectives of this study were: 1) to develop a novel head weight influenced loading protocol (HWL), 2) simulate and compare the EL protocol and the HWL protocol on a single programmable robotic testing frame with a consistent specimen sample group.

Recently, computer-aided robotic systems, such as Robodoc ® system and Makoplasty ® system, have been used to enable surgeons to improve the accuracy of cutting and alignment in knee and hip arthroplasty [1,2,3]. The incision is normally done at the anterior part of the knee and the cutting is performed from the frontal direction during the TKA because enough working space of the tools is required during cutting process. Currently minimal invasive surgery (MIS) is the most popular keyword in the arthroplasty [4], and at this moment the MIS could not be performed common in the TKA using the robotic system. This MIS TKA could be achieved in lateral direction, and different cutting process also changes the robot configuration, which mainly affect the system accuracy. In this study, we investigated what additional advantages could be achieved in the bone cutting process laterally using laboratory-level less-invasive TKA surgical robot system.