Abstract The shape memory effect, superelasticity, and good damping properties, uncommon in other implant alloys, make the nickel-titanium shape memory metal alloy (Nitinol or NiTi) a fascinating material for surgical applications. It provides a possibility to make self-locking, self-expanding and self-compressing implants. The purpose of this work was to determine if NiTi is a safe material for surgical implant applications. The primary cytotoxicity and the corrosion rate of NiTi were assessed in human osteoblast and fibroblast cell cultures. Comparisons were made with 316 LVM stainless steel (StSt) and pure titanium. The metal ions present in the media were analyzed using atomic absorption spectrometry (GFAAS). Despite the higher initial nickel dissolution, NiTi induced no toxic effects, decrease in cell proliferation or inhibition in the growth of cells in contact with the metal surface. The general soft tissue responses to NiTi were compared to corresponding responses to StSt and Ti-6Al-4V alloy in rats during a follow-up of 26 weeks. The muscular tissue response to NiTi was clearly non-toxic and non-irritating, as were also the neural and perineural responses. The overall inflammatory response and the presence of immune cells, macrophages and foreign body giant cells were similar compared to the other test materials. At 8 weeks, histomorphometry showed that the encapsule membrane of NiTi was thicker than that of stainless steel, but at 26 weeks the membrane thicknesses were equal. A regional acceleratory phenomenon (RAP) model was used to evaluate new bone formation, bone resorption and bone (re)modeling after periosteal implantation of NiTi, StSt or Ti-6Al-4V in rats using histomorphometry. Maximum new woven bone formation started earlier in the Ti-6Al-4V group than in the NiTi group, but also decreased earlier, and at 8 weeks the NiTi and StSt groups had greater cortical bone width. Later, no statistical differences were seen. NiTi had no negative effect on total new bone formation or normal RAP during a 26-week follow-up. The ultrastructural features of cell-NiTi adhesion were analyzed with scanning electron microscopy (FESEM). Cell adhesion and focal contacts showed a good acceptance of NiTi. Femoral osteotomies of rats were fixed with either NiTi or StSt intramedullary nails. Bone healing was examined with radiographs, peripheral quantitative computed tomography (pQCT) and histologically. The maximum follow-up was 60 weeks. There were more healed bone unions in the NiTi than the StSt group at early time points. Callus size and bone mineral density did not differ between the NiTi and StSt groups. Mineral density in both groups was lower in the osteotomy area than in the other areas along the nail. Density in the nail area was lower than in the proximal part of the operated femur or the contralateral femur. Bone contact to NiTi was close, indicating good tissue tolerance. Determination of trace metals from several organs was done by GFAAS or inductively coupled plasma-atomic emission spectrometry (ICP-AES). There were no statistically significant differences in nickel concentration between the NiTi and StSt groups in distant organs. The FESEM assessment showed surface corrosion changes to be more evident in the StSt implants. On the basis of this study, the biocompatibility of NiTi seems to be similar to or better than that of stainless steel or Ti-6Al-4V alloy. NiTi appears to be suitable for further use as a biomaterial, because its biocompatibility is good. When NiTi is intended to be used in long-term implants, optimal surface treatment must consider.

Purpose: Examine neuromechanical alterations due to isolated and/or combined knee pain and effusion in functional movements. Methods: A 4X3 randomised controlled laboratory study with repeated measures was used. Nineteen, healthy volunteers (age: 22.4 ± 2.4 years) underwent four different treatments (control, effusion, pain, and pain/effusion) with a week wash out period. Ten near-infrared cameras with 43 reflective markers, 12 surface EMG electrodes, and two ground-embedded force platforms were used to record neuromechanical changes during functional movements (walking and drop landing). To induce pain, 5% sodium chloride (1 ml) was injected into the infrapatellar fat pad. To induce effusion, 0.9% sodium chloride (50 ml) was injected into the knee joint capsule. To induce pain/effusion, both injections were employed. No injection was used for the control. Subjects performed walking and a single leg drop landing in three time intervals: precondition (prior to injection), condition (immediate post injection), and postcondition (30 min post injection). To quantify pain perception, the visual analogue scale was measured every two minutes. Results: Under pain/effusion treatment, subjects walked slowly with a shorter stride length. Joint moments of plantarflexion, knee extension, knee abduction, and hip abduction were reduced. Subjects also showed a decrease at 20% and 80% of stance phase, and an increase in 50% in vertical ground reaction force (VGRF). Under the same treatment, subjects landed with a less peak VGRF with increased time to peak VGRF, alterations of joint angles (ankle dorsiflexion, knee extension, and hip adduction), and moments (knee extension, knee abduction, and hip abduction). Conclusions: Joint pain and effusion cause neuromechanical alterations in the lower extremity during functional movements. These compensatory strategies may alter joint loading, potentially resulting in acceleration of the joint degenerative process. We also recommend use of crutches following injury to avoid modifications of movement strategies.

No description available.

abstract: Locomotion is of prime importance in enabling human beings to effectively respond in space and time to meet different needs. Approximately 2 million Americans live with an amputation with most of those amputations being of the lower limbs. To advance current state-of-the-art lower limb prosthetic devices, it is necessary to adapt performance at a level of intelligence seen in human walking. As such, this thesis focuses on the mechanisms involved during human walking, while transitioning from rigid to compliant surfaces such as from pavement to sand, grass or granular media. Utilizing a unique tool, the Variable Stiffness Treadmill (VST), as the platform for human walking, rigid to compliant surface transitions are simulated. The analysis of muscular activation during the transition from rigid to different compliant surfaces reveals specific anticipatory muscle activation that precedes stepping on a compliant surface. There is also an indication of varying responses for different surface stiffness levels. This response is observed across subjects. Results obtained are novel and useful in establishing a framework for implementing control algorithm parameters to improve powered ankle prosthesis. With this, it is possible for the prosthesis to adapt to a new surface and therefore resulting in a more robust smart powered lower limb prosthesis. / Dissertation/Thesis / Masters Thesis Biomedical Engineering 2019

The main goal of this research was the in vitro investigation of the stiffness response of contracted airway smooth muscles under different external oscillations. Living animal airway smooth muscle tissues were dissected from pig tracheas and stimulated by a chemical stimulus (acetylcholine). These tissues were then systematically excited with different external vibrations. The force change was recorded to reflect the muscle stiffness change under vibration. The static and dynamic stiffness of contracted airway smooth muscles in isometric contraction were determined before, during and after vibrations. A continuum cross-bridge dynamic model (the fading memory model) was modified to accommodate smooth muscle behaviour and dynamically describes the cross-bridge kinetics. A two-dimensional finite element model (FEM) was developed to simulate longitudinal and transverse vibrations of the tissue. An empirical equation, derived from the experiments, is incorporated into the FEM. The results indicate that the stiffness of active smooth muscles can be physically reduced using external vibrations. This reduction is caused by a certain physical position change between actin and myosin. The dynamic stiffness has the tendency of decreasing as the frequency and/or amplitude of external vibration increases. However, the static stiffness decreases with an increase in the frequency and amplitude of excitation until it reaches a critical value of frequency where no variation in stiffness is observed. It is postulated that the tissue elasticity and mass inertia are the main contributors to the dynamic stiffness while the actin-myosin cross-bridge cycling is the main contributor to the static stiffness.

No description available.

The presented work is concerned with the development and application of an ultrasonic detection scheme suitable for the monitoring of muscle dynamics with high temporal - down to 5 µs - and spatial resolution - down to 0.78 µm. A differential detection scheme has been developed to monitor the variations of the velocity of longitudinal polarized ultrasound waves travelling in contracting and relaxing muscle, compensating for variations of the path length by referencing to a frame. The observed time dependent variations of the time-of-flight of the ultrasonic waves caused by variations in the muscle and in addition by minor deformations of the enclosure are detected each separately and synchronously and are evaluated differentially. Beside of the detected increase of the speed of sound observed for contracted muscle with respect to the relaxed state of about 0.6%, the recovery time from maximum isometric contraction is quantified and relaxation processes are observed for the recovery phase following the isometric contraction. The developed ultrasonic calliper was employed to monitor both, the brain controlled and externally excited muscle dynamics with sampling intervals down to 10 ms synchronously with signals relating to the excitation. Monitored are the activation, hold, and relaxation phase for maximum voluntary isometric contraction of the gastrocnemius muscle. A so far not reported post tetanus overshoot and subsequent exponential recovery are observed. Both are attributed to the muscle as suggested by combined monitoring with EMG and are modelled with a lumped mechanical circuit containing an idealized bidirectional linear motor unit, ratchet, damper, and springs. Both, the rapid contraction and relaxation phases require a high order filter or alternatively a kernel filter, attributed to the nerve system as suggested by external electric stimulation. The respective response function is modelled by an electrical lumped circuit. Together with a reaction time and occasionally observed droops in the hold phase, both adjusted empirically, the monitored response is represented in close approximation by the combined electrical and mechanical lumped circuits. The respectively determined model parameters provide a refined evaluation scheme for the performance of monitored athletes. Valuable parameters relate to the latent period, the muscle response time, the activation and deactivation dynamics, a possible droop and other instabilities of the hold phase, and parameters characterizing the relaxation phase including the observed post tetanus overshoot and subsequent contraction. Monitored and modelled are also the different processes involved in active muscle dynamics including isotonic, isometric, and eccentric contraction or stretching. The developed technology provides time sequential observation of these processes and registration of their path in the extension and force parameter space. Under suitable conditions the closed-loop cycles of mind controlled human muscle movements proceed along characteristic lines coinciding with well identifiable elementary processes. The presentation of the monitored processes in the extension and force parameter space allows the determination of the mechanical energy expenditure for the observed different muscle actions. An elementary macroscopic mechanical model has been developed, suitable to express the basic features of the monitored muscle dynamics.

The presented work is concerned with the development and application of an ultrasonic detection scheme suitable for the monitoring of muscle dynamics with high temporal - down to 5 µs - and spatial resolution - down to 0.78 µm. A differential detection scheme has been developed to monitor the variations of the velocity of longitudinal polarized ultrasound waves travelling in contracting and relaxing muscle, compensating for variations of the path length by referencing to a frame. The observed time dependent variations of the time-of-flight of the ultrasonic waves caused by variations in the muscle and in addition by minor deformations of the enclosure are detected each separately and synchronously and are evaluated differentially. Beside of the detected increase of the speed of sound observed for contracted muscle with respect to the relaxed state of about 0.6%, the recovery time from maximum isometric contraction is quantified and relaxation processes are observed for the recovery phase following the isometric contraction. The developed ultrasonic calliper was employed to monitor both, the brain controlled and externally excited muscle dynamics with sampling intervals down to 10 ms synchronously with signals relating to the excitation. Monitored are the activation, hold, and relaxation phase for maximum voluntary isometric contraction of the gastrocnemius muscle. A so far not reported post tetanus overshoot and subsequent exponential recovery are observed. Both are attributed to the muscle as suggested by combined monitoring with EMG and are modelled with a lumped mechanical circuit containing an idealized bidirectional linear motor unit, ratchet, damper, and springs. Both, the rapid contraction and relaxation phases require a high order filter or alternatively a kernel filter, attributed to the nerve system as suggested by external electric stimulation. The respective response function is modelled by an electrical lumped circuit. Together with a reaction time and occasionally observed droops in the hold phase, both adjusted empirically, the monitored response is represented in close approximation by the combined electrical and mechanical lumped circuits. The respectively determined model parameters provide a refined evaluation scheme for the performance of monitored athletes. Valuable parameters relate to the latent period, the muscle response time, the activation and deactivation dynamics, a possible droop and other instabilities of the hold phase, and parameters characterizing the relaxation phase including the observed post tetanus overshoot and subsequent contraction. Monitored and modelled are also the different processes involved in active muscle dynamics including isotonic, isometric, and eccentric contraction or stretching. The developed technology provides time sequential observation of these processes and registration of their path in the extension and force parameter space. Under suitable conditions the closed-loop cycles of mind controlled human muscle movements proceed along characteristic lines coinciding with well identifiable elementary processes. The presentation of the monitored processes in the extension and force parameter space allows the determination of the mechanical energy expenditure for the observed different muscle actions. An elementary macroscopic mechanical model has been developed, suitable to express the basic features of the monitored muscle dynamics.:Table of Contents Chapter 1 1. Introduction 1 1.1 Monitoring of muscle biomechanics 1 1.2 Detection methods in biomechanics 2 1.3 Ultrasound in biomechanical application 5 1.4 Skeletal muscle 6 1.5 Activation of skeletal muscle 8 1.6 Catatonus effect 10 Chapter 2 2. Concepts and methods in ultrasonic motion monitoring 12 2.1 Ultrasound 12 2.2 Specific concepts of the developed ultrasonic detection scheme 16 2.2.1 Time-of-flight 17 2.2.2 Cross correlation 18 2.2.3 Concepts of cross correlation 19 2.2.4 Chirp technique 19 Chapter 3 3. Ultrasonic monitoring of the muscle extension 21 3.1 Data analysis 21 3.2 Application of the developed monitoring scheme 23 3.2.1 Fast signal and data acquisition mode 23 3.2.2 Monitoring with off-line evaluation 24 3.2.3 Method 26 3.2.4 Data evaluation 27 3.3 Quasi-continuous monitoring scheme 28 3.3.1 Slow with on-line data processing and display 29 3.3.2 Fast with data storage only 30 3.4 Monitoring with on-line evaluation 34 3.4.1 Application involving monitoring of athletic performance 36 3.4.2 Data evaluation 37 3.4.3 Summary 42 3.5 Comparative study of pre and post physical loading session 43 3.5.1 Method 43 3.5.2 Results 44 3.5.3 Summary 45 Chapter 4 4. High resolution monitoring of the velocity of ultrasound in contracting and relaxing muscle 47 4.1 Methods 49 4.2 Results and evaluation 51 4.2.1 Poission’s ratio for isometrically contracted muscle 52 4.3 Summary 53 Chapter 5 5. Monitoring of muscle dynamics, muscle force, and EMG 56 5.1 Synchronous monitoring of muscle dynamics with muscle force 56 5.1.1 Force-length dynamics under all-out isometric contraction 56 5.1.1.1 Method 56 5.1.1.2 Result and evaluation 58 5.1.2 Force-length dynamics of equal holding monitoring 62 5.1.2.1 Method 62 5.1.2.2 Results and evaluation 63 5.1.3 Summary 67 5.2 Synchronous monitoring of muscle movement with EMG 69 5.2.1 Method 69 5.2.2 Results and evaluation 70 5.3 Synchronous monitoring of muscle movement, EMG and muscle force 73 5.3.1 Method 73 5.3.2 Results and evaluation 74 5.3.3 Summary 77 Chapter 6 6. Monitoring of skeletal muscle dynamics under isometric contraction and modelling of the non-linear response including post tetanus effects 80 6.1 Method 82 6.2 Data analysis 82 6.3 Results and evaluation 82 6.3.1 Mechanical model 83 6.3.2 Equations relating to modelling 85 6.3.3 Comparison of experimental results and modelling 91 6.3.4 Electrical lumped circuit 93 6.4 Summary 100 Chapter 7 7. Lumped Circuit Model and Energy Transfer for quasi-static approximation 101 7.1 Basic muscle model and biomechanical processes 102 7.1.1 Muscle model 102 7.1.2 Force in the muscular motoric processes 104 7.2 Method 104 7.3 Results of experimental observations of muscle action 106 7.3.1 Muscle force and closed-loop contraction dynamics 106 7.3.2 Muscle work considerations 109 7.4 Summary 110 Chapter 8 8.1 Ultrasonic calliper 112 8.2 Interpretation of sound velocity variation in muscle 114 8.3 Monitored muscle dynamics 118 8.4 Isometric muscle action and tetanus effect 121 8.5 Quasi-static muscle action 125 8.6 Summarizing statement with a moderate outlook 126 References 128 Acknowledgements 140 Selbständigkeitserklärung 141