Mechanical Palpation Research Articles

Osteoimmunological Principles Adapted to Achieve Mechanically Superior Posterolateral Fusion in a New Zealand White Rabbit Model Using Antigen-Coated, Electrospun Beta-Tricalcium Phosphate.

Introduction Triggering the immune system via antigenic stimulation at the time of spinal fusion surgery may enhance bone morphogenesis and result in successful bony arthrodesis. We sought to demonstrate that bone morphogenesis could be enhanced via antigenic immunologic stimulation of a surgical fusion site. Methods New Zealand white rabbits underwent non-instrumented posterolateral fusion of L5-6 with implantation of either an immunologically activated graft (inert beta-tricalcium phosphate) or harvested autograft. Fusion was evaluated using plain radiographs, micro-computed tomography (CT), mechanical palpation, and biomechanical testing. The final evaluation was carried out at 12 weeks postoperatively. Results Eight rabbits received immunologically activated grafts; 10 received autografts and served as historical controls. Fusion rates were identical between groups (both 50%). Radiographs and micro CT of the fusion mass showed no significant difference between groups, and both showed good incorporation of the transverse processes into the fusion masses with radiographic evidence confirming trabeculation and bone remodeling. However, mechanical testing of the fusion sites showed superior fusion strength in the rabbits that received immunologically activated grafts, approaching a factor of two on flexion/extension, lateral bending, and axial rotation. Little to no graft material was appreciable in the non-fused antigen-treated specimens. Conclusions There is a long-standing need for a graft material that can replace autograft bone, due to the negative clinical consequences and financial costs pertaining to autologous bone harvesting. No allograft bone substitute to date has been able to reliably replicate the success of harvested autograft bone. This study suggests that immunological enhancement of inert beta-tricalcium phosphate can potentially be a substitute for allograft bone that can meet and even exceed the success of harvested autograft bone.

Prediction model of contact forces and IOP during digital palpation of porcine eyes

Frequent intraocular pressure (IOP) measurements are desirable in the diagnosis and management of glaucoma. Most current tonometers utilize some form of corneal deformation to estimate the IOP, since trans-scleral tonometry suffers from loss of sensitivity. Tran-scleral and trans-palpebral tonometry, however, offer a pathway towards a non-invasive home tonometry. This article presents a mathematical model capturing the relationship between the IOP and the displacements imposed onto the sclera by externally applied forces. Similar to manual digital palpation tonometry, trans-scleral mechanical palpation makes use of two force probes that are advanced in a specific order and distance. Data from the applied forces and displacements, along with concurrent measurements of IOP is used to produce a phenomenological mathematical model. The experiments were carried out on enucleated porcine eyes.Two models are presented. Model 1 predicts IOP vs forces and displacements, while Model 2 predicts the baseline IOP (prior to applying the forces) as a function of the measured forces and displacements. The proposed models result in IOP errors of 1.65 mmHG and 0.82 mmHg, respectively. Model parameters were extracted using least-squares-based system identification methods. The results show that the proposed models can be used to estimate the baseline IOP with accuracy of ±1 mmHg over a pressure range of 10–35 mmHg, solely from measurement of tactile forces and displacements.

Numerical Analysis of the Localization of Pulmonary Nodules during Thoracoscopic Surgery by Ultra-Wideband Radio Technology

Worldwide, lung cancer is one of the most common causes of cancer-related death. Detected by computer tomography, it is usually removed through thoracoscopic surgery. During the surgery the lung collapses requiring some strategies to track or localize the new position of the lesion. This is particularly challenging in the case of minimally invasive surgeries when mechanical palpation is not possible. Here we undertake a preliminary study with numerical analysis of an ultra-wideband (UWB) radio technology which can be employed directly during thoracoscopic surgery to localize deep solitary pulmonary nodules. This study was conducted through Finite Difference Time Domain (FDTD) simulations, where a spherical target mimicking a nodule located between 1 and 6 cm of depth and an UWB pulse at several frequencies between 0.5 and 5 GHz was used for localization. This investigation quantifies the influence of several parameters, such frequency, lesion depth, and number of acquisitions, on the final confocal image used to locate a cancer in the lung tissue. We also provide extensive discussion on several artifacts that appear in the images. The results show that the cancer localization was possible at operational frequencies below 1 GHz and for deep nodules (>5 cm), while at lower depths and higher frequencies several artifacts hindered its detection.

Collective indentation as a novel strategy for mechanical palpation tomography

The method of mechanical (or robotic) palpation tomography assumes the use of a rigid indenter for in vivo detecting the presence of tissue lesions by the quasi-static contact probe inspection of the surface of the human body. The interpretation of the indentation data requires the inverse solution to contact problems for inhomogeneous substrates. A particular interest has been drawn to quantitative and qualitative analysis of the deformation behavior of a homogeneous elastic substrate with a spherical inclusion under the action of a rigid probe on the substrate surface. In the present paper, using a first-order perturbation-based asymptotic model of multiple contact, it is shown that the indentation tomography problem can be solved in a more efficient way if a system of indenters is simultaneously employed for performing the mechanical palpation diagnostics.

Development and validation of a palpation device for arbitrary muscle stiffness measurements within subjects

Objective: Neuromuscular disorders can often be quantified by the amount of muscle activity and is generally measured through electromyography. However, this method cannot provide arbitrary data as it only detects fluctuations in electrical potential. There is a need for arbitrary and standardised assessments of muscle tone to enable physiotherapists to make correct diagnoses. In this work, we present the rationale and results of a newly developed device to measure arbitrary muscle stiffness. Approach: Three prototypes were developed and iteratively improved. The first one relied on the theory of electrical impedance myography and the two other models managed a mechanical approach using a palpation probe and two reference areas. The final mechanical palpation principle was optimised and tested for two devices and two operators. The experiments were conducted in 39 subjects for left and right arm for relaxed and tensioned m. biceps brachii. Main results: The results show the reliability of the palpation device in terms of repeatability between identical measurements (ICC = 0.93), between different operators (ICC = 0.84) and between the two devices (ICC = 0.88). The device detects significant differences between relaxed and tensioned biceps brachii conditions (p < 0.001). Significance: The study indicates the feasibility of a mechanical muscle stiffness method to provide arbitrary data. The opportunities of the mechanical palpation device to identify variations in neuromuscular impairments in a reproducible procedure is confirmed. Further studies are required to evaluate the tonus of various muscles under diverse circumstances and to pinpoint further applications in clinical practice.

Quantitative diagnostics of soft tissue through viscoelastic characterization using time-based instrumented palpation

Although palpation has been successfully employed for centuries to assess soft tissue quality, it is a subjective test, and is therefore qualitative and depends on the experience of the practitioner. To reproduce what the medical practitioner feels needs more than a simple quasi-static stiffness measurement. This paper assesses the capacity of dynamic mechanical palpation to measure the changes in viscoelastic properties that soft tissue can exhibit under certain pathological conditions. A diagnostic framework is proposed to measure elastic and viscous behaviors simultaneously using a reduced set of viscoelastic parameters, giving a reliable index for quantitative assessment of tissue quality. The approach is illustrated on prostate models reconstructed from prostate MRI scans. The examples show that the change in viscoelastic time constant between healthy and cancerous tissue is a key index for quantitative diagnostics using point probing. The method is not limited to any particular tissue or material and is therefore useful for tissue where defining a unique time constant is not trivial. The proposed framework of quantitative assessment could become a useful tool in clinical diagnostics for soft tissue.

Magnetic resonance elastography of the brain using multishot spiral readouts with self‐navigated motion correction

Magnetic resonance elastography (MRE) has been introduced in clinical practice as a possible surrogate for mechanical palpation, but its application to study the human brain in vivo has been limited by low spatial resolution and the complexity of the inverse problem associated with biomechanical property estimation. Here, we report significant improvements in brain MRE data acquisition by reporting images with high spatial resolution and signal-to-noise ratio as quantified by octahedral shear strain metrics. Specifically, we have developed a sequence for brain MRE based on multishot, variable-density spiral imaging, and three-dimensional displacement acquisition and implemented a correction scheme for any resulting phase errors. A Rayleigh damped model of brain tissue mechanics was adopted to represent the parenchyma and was integrated via a finite element-based iterative inversion algorithm. A multiresolution phantom study demonstrates the need for obtaining high-resolution MRE data when estimating focal mechanical properties. Measurements on three healthy volunteers demonstrate satisfactory resolution of gray and white matter, and mechanical heterogeneities correspond well with white matter histoarchitecture. Together, these advances enable MRE scans that result in high-fidelity, spatially resolved estimates of in vivo brain tissue mechanical properties, improving upon lower resolution MRE brain studies that only report volume averaged stiffness values.

Urethral flow-responsive afferents in the cat sacral dorsal root ganglia

Although sensory feedback from the urethra plays an integral role in the regulation of lower urinary tract function, little is known about the properties of flow-responsive primary afferent neurons. The purpose of this study was to characterize the activity of sacral afferents that responded to fluid flow through the urethra. Single neuron action potentials were recorded extracellularly from the S1 and S2 dorsal root ganglia in eight cats anesthetized with α-chloralose. 21 of 116cells responded to urethral flow but not to mechanical palpation of the perineum, 22 responded to both urethral flow and palpation, and 27 responded to palpation only. 34 of the 43 flow-responsive cells exhibited a firing response to 10ml flow boluses that could be fit using a power function: FR(t)=a×(t)b+c, where FR is firing rate, t is time, and a, b and c are constants. In all 34cells the ‘b’ term was negative, indicating that the firing rate slowed over the time course of the urethral flow. In 16 of the 24cells that were recorded during at least four different flow rates, a power function provided a good fit of the relationship between firing rate and flow rate: FR(flow)=k×(flow)p+q, where k, p and q are constants. In each of these 16cells the ‘p’ term was positive, indicating that the firing rate tended to increase with increases in flow rate. These are the first data to characterize the properties of flow-responsive afferents in the cat, and reveal properties that parallel those of other afferents.

Evaluation of elastic modulus of materials by adhesive (no–slip) nano–indentation

Results of Mossakovskii's analysis for the elastic, adhesive (no–slip) contact between a rigid, axisymmetric punch and an isotropic, elastic half–space are developed in order to show that a simple relation exists between the contact stiffness, the contact area and the elastic modulus. The relation is similar to the Bulychev–Alekhin–Shorshorov equation, which is commonly used for evaluation of elastic modulus of materials by nano–indentation. The final formula differs from the frictionless case by a factor that depends on the Poisson ratio of the material. The bounds for the values of the factor are estimated. Similar to the frictionless analysis performed by Pharr, Oliver and Brotzen, the relation is not dependent on the geometry of the punch.

Le comportement mécanique fin d’un assemblage collé

We compare the fine mechanical behaviour of two adhesively bonded joints, of the double-lap type, one of which has tapered splice plates.The active surfaces (bearers) of the adherends underwent a chemical sulfochromic treatment, directly applied to the raw surfaces of 2024-PLA5 Aluminium alloy in T 3 state, in conformity with the recommandations of Aerospatiale Aquitaine.The roughness geometry of bearers is defined by the principal parameters of profile, obtained through mechanical palpation, and by the Abbot curve.Mechanical behaviour of the test specimens is experimentally characterized in the course of a trial in simple traction, by the simultaneous measurement of deformations through electrical strainganges, and the record of acoustical emission. The trials are realized at room temperature.The studied structures have a very complex behaviour. This sterns from the fact that the adherends are not slender (overlap length l = 12,5 mm, overlap width l 1 = 25 mm), and that they are bonded by a supported, adhesive film, of Hysol 9628 NW, whose behaviour is strongly elastic-plastic.This situation induced us to use, for the modelling, a slender assembly, fully bevelled, the adherends of which are bonded by a brittle adhesive without marked visco-elasticity. A simplified calculation has been worked out by Michel L. L. Klein, by utilizing a method that generalizes the classical theory, where the adherends are strained in preponderant traction (see pp. 33-36 of this issue).If we take, for darnage criterion, the begining of the first microcracks, it becomes apparent that the test-specimen with tapered splice plates is the most resistant. The results, obtained by the two techniques, are very correlated.