Papers by Vivek Shekhawat
Biotribology, 2021
Biomechanical influences play a fundamental role in the structural, functional, and biosynthetic ... more Biomechanical influences play a fundamental role in the structural, functional, and biosynthetic properties of articular cartilage. During physiologic joint loading, the contact area between two surfaces migrates due to the primary and secondary motions of the joint. It has been demonstrated that a migratory contact area plays a critical role in reducing the coefficient of friction at the cartilage surface. However, a detailed analysis of the influences that a migratory contact area plays on the structural, functional, and biosynthetic properties remain to be explored. In this study, bovine cartilage explants were placed in a biotribometer. Explants were subjected to compression and shear forces of migratory contact area, namely moving contact (MC) articulation, or stationary contact area, namely stationary contact (SC) articulation. Free swelling explants were used as control. In a separate study, bovine cartilage-bone grafts were used for frictional testing. On histologic analysis, the SC group had evidence of surface fibrillations, which was not evident in the MC group. Compared to the SC group, the MC group cartilage explants had increased chondrocyte viability, increased lubricin synthesis, and comparable proteoglycan synthesis and release. MC articulation had reduced coefficient of friction as compared to SC articulation. MC articulation led to reduced surface roughness as compared to SC articulation. In conclusion, a migratory contact area can play an important role in maintaining the structural, function, and biosynthetic properties of articular cartilage. This study provides further evidence of the importance of migratory contact area and in vitro assessment of natural joint movement, which can be further evaluated in the context of cartilage homeostasis and disease.
Journal of orthopaedic research : official publication of the Orthopaedic Research Society, Mar 23, 2016
The purpose of this study was to investigate the effects of trauma and subsequent articulation on... more The purpose of this study was to investigate the effects of trauma and subsequent articulation on adult human ankle cartilage subjected to injurious impact. Trauma was initiated through impaction on talar cartilage explants. Articulation and loading were applied in a joint bioreactor over five consecutive days. The early (24 hrs) effects of impaction included reduced chondrocytes viability (51% vs. 81% for non-impacted; p = 0.03), increased levels of apoptosis (43% vs. 27%; p = 0.03), and an increase in the histopathology score (4.4 vs. 1.7; p = 0.02) as compared to non-impacted cartilage explants. One of the key findings was that damage also stimulated PRG4 release (2.2 vs. 1.5 µg/ml). Subsequent articulation for five days did not lead to further changes in tissue histopathology and cell viability, neither for injured nor non-injured samples. However, articulation led to increased apoptosis in the injured samples (p = 0.03 for the interaction term). Articulation also caused a signi...
Proceedings of the Human Factors and Ergonomics Society Annual Meeting, 2015
Unobtrusive observations of bicyclists were conducted at two-way, three-way, and four-way stop-co... more Unobtrusive observations of bicyclists were conducted at two-way, three-way, and four-way stop-controlled intersections. Consistent with previous reports, most cyclists did not stop at the stop sign. However, most cyclists did exhibit safety-related behaviors by making accommodations for traffic conditions. It was found that the cyclists conducted precautionary visual search when approaching stop signs, and that they were more likely to slow substantially or stop if cross traffic was not controlled by stop signs or if there were potential conflicts from other road users. Implications for safety interventions are discussed.
ASME 2008 Summer Bioengineering Conference, Parts A and B, 2008
ABSTRACT
SAE Technical Paper Series, 2014
Osteoarthritis and Cartilage, 2009
Objective: By means of scanning white light interferometry, develop a noncontact, nondestructive ... more Objective: By means of scanning white light interferometry, develop a noncontact, nondestructive technique capable of measuring surface topography of viable cartilage. Methods: Using full thickness cylindrical cartilage explants obtained from bovine calf knees, experiments were performed to produce a surface preparation protocol that yields highly repeatable topographical measurements while maintaining cartilage viability. To further validate the technique, a series of human talar cartilage samples, displaying varying degrees of cartilage degeneration, was then subjected to interferometric measurements and compared to their histology. Results: A key aspect of the technique of surface topographic measurement by interferometry was the development of an optimal surface preparation process. The technique was successfully validated against standard 2-D profilometry. The intrinsic variability of the technique is less than 2%, which is much less than the average point-to-point variability of 17% observed across a cartilage specimen. The technique was hence sufficiently sensitive to readily detect differences in roughness between surfaces of healthy cartilage in different locations on the bovine knee. Thus, the average roughness of the medial explants exceeded that of the lateral explants by 0.35 mm Ra (P ¼ 0.003) and the roughness of the trochlear explants exceeded that of the condylar explants by 0.55 mm Ra (P < 0.0001). Also, applying this technique to diseased human talar cartilage samples, a statistically significant increase in the average surface roughness value per unit increase in histological degeneration score was observed (!0.2 mm Ra, P 0.041), making surface roughness obtained via interferometry a useful parameter for evaluating cartilage health nondestructively. Conclusions: The aim of developing a protocol based on white light interferometry to measure the surface topography of viable articular cartilage was achieved. This interferometric technique opens the door to monitoring the surface topography of live cartilage, as is desirable for ex vivo tests on cartilage explants.
Osteoarthritis and Cartilage, 2007
Purpose: We have previously shown that bone morphogenetic protein 2 (BMP-2) can induce the chondr... more Purpose: We have previously shown that bone morphogenetic protein 2 (BMP-2) can induce the chondrogenic differentiation of synovial-tissue explants in a time-dependent manner. However, BMP-2 alone cannot effect the complete differentiation of synovial tissue into a typical hyaline type of articular cartilage throughout the entire explant volume. In the present study, we investigated 16.2 Cellular responses in acute trauma of human ankle cartilage: Cell survival, catabolic cytokines and neuromediators
Arthroscopy: The Journal of Arthroscopic & Related Surgery, 2012
Advanced cartilage repair techniques and the development of superior resurfacing materials for ar... more Advanced cartilage repair techniques and the development of superior resurfacing materials for articulation against cartilage could have a major impact on future treatment and surgical techniques by challenging the current dominance of total hip and knee joint replacements. Such advances require the development of ex vivo cartilage tribological tests that include the capability of monitoring the surface topography of live cartilage. Toward this end, we report on a non-contact, non-destructive technique based on scanning white light interferometry that is capable of measuring the surface topography of viable cartilage. A key aspect of the technique was the development of an optimal surface preparation process. The technique was successfully validated against standard 2-D profilometry. The intrinsic variability of the technique is much less than the average point-to-point variability observed across a cartilage specimen. The technique was thus sufficiently sensitive to readily detect ...
Unobtrusive observations of bicyclists were conducted at two-way, three-way, and four-way stop-co... more Unobtrusive observations of bicyclists were conducted at two-way, three-way, and four-way stop-controlled intersections. Consistent with previous reports, most cyclists did not stop at the stop sign.
Uploads
Papers by Vivek Shekhawat