Kalyani Nair

Integrative Structural Biomechanical Concepts of Ankylosing Spondylitis

Ankylosing spondylitis (AS) is not fully explained by inflammatory processes. Clinical, epidemiological, genetic, and course of disease features indicate additional host-related risk processes and predispositions. Collectively, the pattern of predisposition to onset in adolescent and young adult ages, male preponderance, and widely varied severity of AS is unique among rheumatic diseases. However, this pattern could reflect biomechanical and structural differences between the sexes, naturally occurring musculoskeletal changes over life cycles, and a population polymorphism. During juvenile development, the body is more flexible and weaker than during adolescent maturation and young adulthood, when strengthening and stiffening considerably increase. During middle and later ages, the musculoskeletal system again weakens. The novel concept of an innate axial myofascial hypertonicity reflects basic mechanobiological principles in human function, tissue reactivity, and pathology. However, these processes have been little studied and require critical testing. The proposed physical mechanisms likely interact with recognized immunobiological pathways. The structural biomechanical processes and tissue reactions might possibly precede initiation of other AS-related pathways. Research in the combined structural mechanobiology and immunobiology processes promises to improve understanding of the initiation and perpetuation of AS than prevailing concepts. The combined processes might better explain characteristic enthesopathic and inflammatory processes in AS.

Greater Resting Lumbar Extensor Myofascial Stiffness in Younger Ankylosing Spondylitis Patients Than Age-Comparable Healthy Volunteers Quantified by Myotonometry

OBJECTIVE To quantify resting lumbar erector myofascial stiffness in younger patients with ankylosing spondylitis (AS) and age-comparable healthy control subjects using a handheld mechanical impulse-based myotonometric device. DESIGN A case-control study of 24 patients with AS and 24 age-comparable healthy control subjects. SETTING University physical therapy department. PARTICIPANTS Patients with AS (men: n=19; women: n=5; total: N=24) and healthy volunteers (men: n=19; women: n=5; total: N=24) without low back pain (age range, 18-46y). INTERVENTIONS Not applicable. MAIN OUTCOME MEASURE Lumbar myofascial stiffness. RESULTS At the initial measurements, median stiffness (Nm) of the averaged right- and left-sided values was greater (P=.021) in 24 patients with AS than 24 control subjects (268.9 vs 238.9, respectively). Repeated measurements after a 10-minute prone resting period were also greater (P=.007) in patients with AS than control subjects (281.0 vs 241.4, respectively). The 48 averaged right- and left-sided values from baseline and 10-minute measurements were compared in each subject group. The patients with AS more frequently (P=.012) had stiffness values >250 Nm (35 [72.9%] vs 22 [45.8%] in control subjects). CONCLUSIONS Lumbar myofascial stiffness was greater in 24 patients with AS than in the control subjects. A hypothesized biomechanical concept of increased resting lumbar myofascial stiffness in AS may be supported by this preliminary controlled study.

Repeatability, Reproducibility, and Calibration of the MyotonPro® on Tissue Mimicking Phantoms

The MyotonPro® (Myoton AS, Tallinn, Estonia) is commonly used to quantify stiffness properties of living tissues in situ. Current studies quantify the dynamic stiffness properties of living tissues, but do not validate or compare these measurements to a standardized method. Additionally, living tissue, being dynamic in nature, presents much variability in data collection. To address these issues this study focuses on the repeatability and reproducibility of the MyotonPro® on polymeric gel-based tissue phantoms. In addition, a correlation study is also performed to translate dynamic stiffness to a more standardized property, Young’s modulus. Such studies help to confirm the reliability of the measurements obtained in situ.Copyright

Quantifying intrinsic properties of resting lumbar muscle in healthy subjects using a handheld myometer

Resting muscle exhibits certain inherent properties whose interpretation is important to the understanding of the function and health of muscle. These physical properties aid in better understanding the behavior of muscle and its effects on the lumbosacral spine. A wealth of research has been performed on actively contracting muscles, however there is little existing literature on the properties of muscle in its relaxed state. In this study, the resting muscle properties of the lower lumbar muscles were quantified in 20 young, healthy adults. Measurements were taken from the left and right sides of the back, and were repeated after a 10 minute waiting period. Surface electromyography (sEMG) measurements were also carried out simultaneous to ensure the patients muscles were in a resting state. Data suggest that the hypothesis of a population variation of human resting muscle tone (HRMT) properties may occur among normal subjects; however, more quantitative data is required to confirm and characterize this trait.

Effects of Process Parameters on Cell Damage in a 3D Cell Printing Process

Various types of bio-fabrication methods have been developed to manufacture products with living cells incorporated via mechanical means. One of fundamental questions that need to be answered is whether cells remain viable and/or functional when subjected to these mechanical disturbances. In this paper, we focus on a 3D cell-printing process via pressure induced deposition. Our experimental studies show that process parameters such as pressure applied and nozzle size affect the cell viability. Given that the cells are suspended in the alginate solution during the printing process, Computational Fluid Dynamic (CFD) analysis is employed to model the pressure-driven flow system and determine the local environment that the living cells are in under varying process parameters. Effects of obtained wall shear stress and exposure time are examined in terms of cell damage based on the corresponding experimental data.Copyright

Biomechanical properties of low back myofascial tissue in younger adult ankylosing spondylitis patients and matched healthy control subjects

Background: Ankylosing spondylitis is a degenerative and inflammatory rheumatologic disorder that primarily affects the spine. Delayed diagnosis leads to debilitating spinal damage. This study examines biomechanical properties of non‐contracting (resting) human lower lumbar myofascia in ankylosing spondylitis patients and matched healthy control subjects. Methods: Biomechanical properties of stiffness, frequency, decrement, stress relaxation time, and creep were quantified from 24 ankylosing spondylitis patients (19 male, 5 female) and 24 age‐ and sex‐matched control subjects in prone position on both sides initially and after 10min rest. Concurrent surface electromyography measurements were performed to ensure resting state. Statistical analyses were conducted, and significance was set at p<0.05. Findings: Decreased lumbar muscle elasticity (inverse of decrement) was primarily correlated with disease duration in ankylosing spondylitis subjects, whereas BMI was the primary correlate in control subjects. In ankylosing spondylitis and control groups, significant positive correlations were observed between the linear elastic properties of stiffness and frequency as well as between the viscoelastic parameters of stress relaxation time and creep. The preceding groups also showed significant negative correlations between the linear elastic and viscoelastic properties. Interpretation: Findings indicate that increased disease duration is associated with decreased tissue elasticity or myofascial degradation. Both ankylosing spondylitis and healthy subjects revealed similar correlations between the linear and viscoelastic properties which suggest that the disease does not directly alter their inherent interrelations. The novel results that stiffness is greater in AS than normal subjects, whereas decrement is significantly correlated with AS disease duration deserves further investigation of the biomechanical properties and their underlying mechanisms. HIGHLIGHTSLimited studies exist in the area of human resting muscle tone and its effects.The role of muscle properties in ankylosing spondylitis has not been studied.Few studies relate BMI, age, disease duration with muscle biomechanical properties.Disease duration alters low back elasticity and stiffness in ankylosing spondylitis.Relations between linear elastic and viscoelastic properties not altered by disease.

On analysis of surface electromyography signal from resting lumbar myofascial tissue

Ankylosing spondylitis (AS) often develops in early adulthood with progressive reduced spine mobility. Myofascial stiffness or tone is the stiffness of resting muscle and its alterations may be associated with low back disorders. In our research, the passive resting stiffness of lower lumbar extensor myofascia in young subjects has been quantified concurrently with surface electromyography (sEMG). Our hypothesis is that greater lumbar myofascial stiffness in AS vs normal subjects is an intrinsic myofascial property and analyses of sEMG will help in determining its potential relations to variations in resting muscle tone. The focus of this study is to use a differential amplifier to amplify the sEMG signal and use Myoscan sensor to collect data, then apply signal processing algorithms for time-frequency analysis. Such quantitative studies may help identify AS disease in the earliest stage and enhance the clinical evaluation of this disease.

Biocompatibility of human Whartons Jelly Mesenchymal Stem Cells on poly-caprolactone and collagen based nanofiber mats

Nanofiber scaffolds were fabricated to analyze the proliferation of human Whartons Jelly Mesenchymal Stem Cells (hWJMSCs) for skin tissue engineering applications. Poly-caprolactone (PCL) and PCL mixed with collagen scaffolds were fabricated using electrospinning. ImageJ analysis was carried out on SEM images to characterize the structural and morphological properties of the nanofiber scaffolds. Tensile testing was also performed to quantify the mechanical properties of the scaffolds. The scaffolds were then seeded with hWJMSCs to study cell proliferation over five days in order to determine the feasibility for tissue regeneration. The average fiber diameters for the PCL scaffold and for the PCL/collagen scaffold were 0.542 μm and 0.633 μm, respectively. The Youngs Moduli of the PCL and PCL/collagen scaffolds were 0.00370 Pa and 0.00683 Pa. respectively. After analyzing the data, it can be concluded that the PCL/collagen scaffold is better suited for regeneration of damaged or diseased nervous tissue.

Finite Element Analysis of the effects of resting muscle tone on enthesis sites in the lumbar spine

Using Finite Element Analysis (FEA) to model the lumbar spine and its surrounding fascia provides valuable information regarding the reactions between the multifidus muscle and the spine. The focus of this study is to analyze the effects of resting muscle stiffness properties at the enthesis sites of the spine. Entheses, or attachment sites of tendons, joint capsules or ligaments to bones, have been shown to be locations of stress concentrations. Additionally, enthesophytes, or bone spurs at an enthesis, have also been identified as a physiological response to mechanical stress. This study will test the hypothesis that the enthesis lesions present in patients with low back pain (LBP) and other musculoskeletal disorders such as ankylosing spondylitis (AS) may result from excess stress concentrations due to increased resting muscle stiffness.

Design and Development of a Modular Medical Simulation Prototype for Pediatric Spinal Detethering Surgeries

Medical simulation is a developing field used in the education of medical students, doctors, residents, and many other medical professionals. Despite emerging simulation tools, little has been done to address surgeries in congenital patients, specifically with regards to the spinal cord. The objective of this project was to design, fabricate, and functionally evaluate a medical simulator to address the challenge of teaching the spinal detethering surgical procedure to neurosurgery residents. This simulator was designed to mimic anatomical and physiological characteristics of the lower lumbar region. Pressure sensors were used to quantify the forces that were applied to the spinal cord during the surgical procedure and a LabVIEW program was developed to monitor the pressure profile. The simulator was functionally evaluated by six residents, one fellow, one doctor, and two medical students. A conclusive, quantitative method for scoring these surgeries has not yet been developed, however, the residents and medical students were able to compare their procedures with those of more experienced doctors and fellows via qualitative methods. Future developments will include incorporating quantitative scoring methods as well as noise elimination hardware into the design.