Alexander Proctor

Publications

• 6.04

  Impact points

  Microindentation for in vivo measurement of bone tissue mechanical properties in humans.

  Adolfo Diez-Perez, Roberto Güerri, Xavier Nogues, Enric Cáceres, Maria Jesus Peña, Leonardo Mellibovsky, Connor Randall, Daniel Bridges, James C Weaver, Alexander Proctor, Davis Brimer, Kurt J Koester, Robert O Ritchie, Paul K Hansma

  Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research. 02/2010; 25(8):1877-85.

  Bone tissue mechanical properties are deemed a key component of bone strength, but their assessment requires invasive procedures. Here we validate a new instrument, a reference point indentation (RPI) instrument, for measuring these tissue properties in vivo. The RPI instrument performs bone microin... [more] Bone tissue mechanical properties are deemed a key component of bone strength, but their assessment requires invasive procedures. Here we validate a new instrument, a reference point indentation (RPI) instrument, for measuring these tissue properties in vivo. The RPI instrument performs bone microindentation testing (BMT) by inserting a probe assembly through the skin covering the tibia and, after displacing periosteum, applying 20 indentation cycles at 2 Hz each with a maximum force of 11 N. We assessed 27 women with osteoporosis-related fractures and 8 controls of comparable ages. Measured total indentation distance (46.0 +/- 14 versus 31.7 +/- 3.3 microm, p = .008) and indentation distance increase (18.1 +/- 5.6 versus 12.3 +/- 2.9 microm, p = .008) were significantly greater in fracture patients than in controls. Areas under the receiver operating characteristic (ROC) curve for the two measurements were 93.1% (95% confidence interval [CI] 83.1-100) and 90.3% (95% CI 73.2-100), respectively. Interobserver coefficient of variation ranged from 8.7% to 15.5%, and the procedure was well tolerated. In a separate study of cadaveric human bone samples (n = 5), crack growth toughness and indentation distance increase correlated (r = -0.9036, p = .018), and scanning electron microscope images of cracks induced by indentation and by experimental fractures were similar. We conclude that BMT, by inducing microscopic fractures, directly measures bone mechanical properties at the tissue level. The technique is feasible for use in clinics with good reproducibility. It discriminates precisely between patients with and without fragility fracture and may provide clinicians and researchers with a direct in vivo measurement of bone tissue resistance to fracture.
• 1.52

  Impact points

  The tissue diagnostic instrument.

  Paul Hansma, Hongmei Yu, David Schultz, Azucena Rodriguez, Eugene A Yurtsev, Jessica Orr, Simon Tang, Jon Miller, Joseph Wallace, Frank Zok, [......], Carol Chen, Mathilde Peters, David Kohn, Jenni Buckley, Xiaojuan Li, Lisa Pruitt, Adolfo Diez-Perez, Tamara Alliston, Valerie Weaver, Jeffrey Lotz

  The Review of scientific instruments. 06/2009; 80(5):054303.

  Tissue mechanical properties reflect extracellular matrix composition and organization, and as such, their changes can be a signature of disease. Examples of such diseases include intervertebral disk degeneration, cancer, atherosclerosis, osteoarthritis, osteoporosis, and tooth decay. Here we introd... [more] Tissue mechanical properties reflect extracellular matrix composition and organization, and as such, their changes can be a signature of disease. Examples of such diseases include intervertebral disk degeneration, cancer, atherosclerosis, osteoarthritis, osteoporosis, and tooth decay. Here we introduce the tissue diagnostic instrument (TDI), a device designed to probe the mechanical properties of normal and diseased soft and hard tissues not only in the laboratory but also in patients. The TDI can distinguish between the nucleus and the annulus of spinal disks, between young and degenerated cartilage, and between normal and cancerous mammary glands. It can quantify the elastic modulus and hardness of the wet dentin left in a cavity after excavation. It can perform an indentation test of bone tissue, quantifying the indentation depth increase and other mechanical parameters. With local anesthesia and disposable, sterile, probe assemblies, there has been neither pain nor complications in tests on patients. We anticipate that this unique device will facilitate research on many tissue systems in living organisms, including plants, leading to new insights into disease mechanisms and methods for their early detection.

• The tissue diagnostic instrument

  Paul Hansma, Hongmei Yu, David Schultz, Eugene A. Yurtsev, Jessica Orr, Simon Tang, Jon Miller, Frank Zok, Richard Souza, Alexander Proctor, Xavier Nogues-Solan, M.Jesus Peña, Lisa Pruitt, Adolfo Diez-Perez, Tamara Alliston, Valerie Weaver, Jeff Lotz

  Review of Scientific Instruments. 05/2009;

  Tissue mechanical properties reflect extracellular matrix composition and organization, and as such, their changes can be a signature of disease. Examples of such diseases include intervertebral disk degeneration, cancer, atherosclerosis, osteoarthritis, osteoporosis, and tooth decay. Here we introd... [more] Tissue mechanical properties reflect extracellular matrix composition and organization, and as such, their changes can be a signature of disease. Examples of such diseases include intervertebral disk degeneration, cancer, atherosclerosis, osteoarthritis, osteoporosis, and tooth decay. Here we introduce the tissue diagnostic instrument �TDI�, a device designed to probe the mechanical properties of normal and diseased soft and hard tissues not only in the laboratory but also in patients. The TDI can distinguish between the nucleus and the annulus of spinal disks, between young and degenerated cartilage, and between normal and cancerous mammary glands. It can quantify the elastic modulus and hardness of the wet dentin left in a cavity after excavation. It can perform an indentation test of bone tissue, quantifying the indentation depth increase and other mechanical parameters. With local anesthesia and disposable, sterile, probe assemblies, there has been neither pain nor complications in tests on patients. We anticipate that this unique device will facilitate research on many tissue systems in living organisms, including plants, leading to new insights into disease mechanisms and methods for their early detection. © 2009 American Institute of Physics. �DOI: 10.1063/1.3127602� I. INTRODUCTION The tissue diagnostic instrument �TDI� was redesigned from the bone diagnostic instrument1,2 so as to measure tissue mechanical properties subcutaneously and in vivo with additional probe assemblies and an adjustable compliance �Fig. 1�. It consists of a thin probe assembly that can penetrate skin and soft tissue to reach deep tissues. The disposable, sterilizable probe assembly consists of an outer reference probe made from a 23 gauge hypodermic needle and an inner test probe made from stainless steel wire ranging from 175 to 300 �m in diameter and from 2 to 90 mm in length. Since friction between the test probe and the reference probe increases with length, it is desirable to use only the length needed to access the desired tissue location. The test probe is held in a nickel tube that couples to a magnet, which in turn is linked to a force generator. During operation the force generator oscillates the probe within the tissue of interest and concurrently measures the force and displacement. The maximum values for force and displacement are 12 N and 600 �m. The probe is typically operated at a frequency of 4 Hz because this is rapid enough to allow hand holding yet sufficiently slow to allow easy decoupling of the elastic and viscous response of the tissue �see supplementary material3 for more details including force and displacement ranges.� II. MEASUREMENTS We first illustrate TDI use in human spinal disks that are composed of a thick outer ligament �annulus fibrosus� and a central swelling hydrogel �nucleus pulposus�. Spinal disk degeneration can be the underlying cause of back pain leading to significant morbidity and societal expense. Intervertebral disks are one of the most highly loaded tissues in the body, and consequently material property insufficiency can lead to damage accumulation, inflammation, and pain. Disk degen- REVIEW OF SCIENTIFIC INSTRUMENTS 80, 054303 �2009� 0034-6748/2009/80�5�/054303/6/$25.00 80, 054303-1 © 2009 American Institute of Physics Downloaded 28 May 2009 to 72.215.163.35. Redistribution subject to AIP license or copyright; see http://rsi.aip.org/rsi/copyright.jsp
• 1.52

  Impact points

  The bone diagnostic instrument II: Indentation distance increase.

  Paul Hansma, Patricia Turner, Barney Drake, Eugene Yurtsev, Alexander Proctor, Phillip Mathews, Jason Lelujian, Connor Randall, Jonathan Adams, Ralf Jungmann, Federico Garza-de-Leon, Georg Fantner, Haykaz Mkrtchyan, Michael Pontin, Aaron Weaver, Morton B. Brown, Nadder Sahar, Ricardo Rossello, David Kohn

  The Review of scientific instruments. 07/2008; 79(6):064303.

  The bone diagnostic instrument (BDI) is being developed with the long-term goal of providing a way for researchers and clinicians to measure bone material properties of human bone in vivo. Such measurements could contribute to the overall assessment of bone fragility in the future. Here, we describe... [more] The bone diagnostic instrument (BDI) is being developed with the long-term goal of providing a way for researchers and clinicians to measure bone material properties of human bone in vivo. Such measurements could contribute to the overall assessment of bone fragility in the future. Here, we describe an improved BDI, the Osteoprobe IItrade mark. In the Osteoprobe IItrade mark, the probe assembly, which is designed to penetrate soft tissue, consists of a reference probe (a 22 gauge hypodermic needle) and a test probe (a small diameter, sharpened rod) which slides through the inside of the reference probe. The probe assembly is inserted through the skin to rest on the bone. The distance that the test probe is indented into the bone can be measured relative to the position of the reference probe. At this stage of development, the indentation distance increase (IDI) with repeated cycling to a fixed force appears to best distinguish bone that is more easily fractured from bone that is less easily fractured. Specifically, in three model systems, in which previous mechanical testing and/or tests reported here found degraded mechanical properties such as toughness and postyield strain, the BDI found increased IDI. However, it must be emphasized that, at this time, neither the IDI nor any other mechanical measurement by any technique has been shown clinically to correlate with fracture risk. Further, we do not yet understand the mechanism responsible for determining IDI beyond noting that it is a measure of the continuing damage that results from repeated loading. As such, it is more a measure of plasticity than elasticity in the bone.

• Publisher’s Note: “The bone diagnostic instrument II: Indentation distance increase” [Rev. Sci Instrum. 79, 064303 (2008)]

  Paul Hansma, Patricia Turner, Barney Drake, Eugene Yurtsev, Alexander Proctor, Phillip Mathews, Jason Lulejian, Connor Randall, Jonathan Adams, Ralf Jungmann, Federico Garza-de-Leon, Georg Fantner, Haykaz Mkrtchyan, Michael Pontin, Aaron Weaver, Morton B. Brown, Nadder Sahar, Ricardo Rossello, David Kohn

• The effect of NaF in vitro on the mechanical and material properties of trabecular and cortical bone

  Philipp J. Thurner, Blake Erickson, Patricia Turner, Ralf Jungmann, Jason Lelujian, Alexander Proctor, James C Weaver, Georg Schitter, Daniel E Morse, Paul K Hansma

  High doses of sodium fluoride in bones lead to severe softening, by weakening interfacial properties between the inorg. minerals and the org. components, while leaving mineralization unchanged. This leads to redn. of microdamage and assocd. stress-whitening pointing to a change in failure mode. Acco... [more] High doses of sodium fluoride in bones lead to severe softening, by weakening interfacial properties between the inorg. minerals and the org. components, while leaving mineralization unchanged. This leads to redn. of microdamage and assocd. stress-whitening pointing to a change in failure mode. Accordingly, elastic modulus, failure stress, and indentation-distance increase are decreased, whereas failure strain is increased. [on SciFinder (R)]