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Research Papers

Applications of a New Handheld Reference Point Indentation Instrument Measuring Bone Material Strength

[+] Author and Article Information
Daniel Bridges, Heather Barnard, Hal Kopeikin

Department of Physics,
University of California,
Santa Barbara, CA 93106

Leonardo Mellibovsky

Hospital del Mar-IMIM-Universitat
Autónoma and RETICEF,
Instituto Carlos III,
Barcelona 08003, Spain

Kevin Hoffseth, Henry T. Y. Yang

Department of Mechanical Engineering,
University of California,
Santa Barbara, CA 93106

Ananya Srikanth, Srinivasan Chandrasekar

Materials Engineering,
Purdue University,
West Lafayette, IN 47907

James C. Weaver

Wyss Institute for Biologically
Inspired Engineering,
Harvard University,
Cambridge, MA 02138

James Candy

Active Life Technologies LLC,
Santa Barbara, CA 93101

Timothy Lescun

Veterinary Clinical Sciences,
Purdue University,
West Lafayette, IN 47907

Eric Orwoll

Oregon Health & Science University,
Portland, OR 97239

Doug Herthel

Alamo Pintado Equine Medical Center,
Los Olivos, CA 93441

Sundeep Khosla

Mayo Clinic,
Rochester, MN 55905

Adolfo Diez-Perez

Hospital del Mar-IMIM-Universitat
Autónoma and RETICEF,
Instituto Carlos III,
Barcelona 08003, Spain

Paul K. Hansma

Department of Physics,
University of California,
Santa Barbara, CA 93106
Active Life Technologies LLC,
Santa Barbara, CA 93101

Manuscript received June 13, 2012; final manuscript received June 3, 2013; published online September 24, 2013. Editor: Gerald E. Miller.

J. Med. Devices 7(4), 041005 (Sep 24, 2013) (6 pages) Paper No: MED-12-1079; doi: 10.1115/1.4024829 History: Received June 13, 2012; Revised June 03, 2013

A novel, hand-held Reference Point Indentation (RPI) instrument, measures how well the bone of living patients and large animals resists indentation. The results presented here are reported in terms of Bone Material Strength, which is a normalized measure of how well the bone resists indentation, and is inversely related to the indentation distance into the bone. We present examples of the instrument's use in: (1) laboratory experiments on bone, including experiments through a layer of soft tissue, (2) three human clinical trials, two ongoing in Barcelona and at the Mayo Clinic, and one completed in Portland, OR, and (3) two ongoing horse clinical trials, one at Purdue University and another at Alamo Pintado Stables in California. The instrument is capable of measuring consistent values when testing through soft tissue such as skin and periosteum, and does so handheld, an improvement over previous Reference Point Indentation instruments. Measurements conducted on horses showed reproducible results when testing the horse through tissue or on bare bone. In the human clinical trials, reasonable and consistent values were obtained, suggesting the Osteoprobe® is capable of measuring Bone Material Strength in vivo, but larger studies are needed to determine the efficacy of the instrument's use in medical diagnosis.

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Figures

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Fig. 1

Scanning electron microscope images of Osteoprobe indentations in the tibia of two different 83-year-old female donors. These images display the microcracks created by the measurement to determine the BMS. The bone on the left (Sample A) appears to have fewer and shorter microcracks on the bone's surface, which resulted in a lower indentation distance and correspondingly a higher BMS of 89.8. Conversely, the bone on the right (Sample B) appears to have more microcracks, which resulted in a greater indentation distance and a lower BMS of 66.2. Thus, the bone with higher BMS is the bone that is more resistant to local damage from indentation.

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Fig. 2

In vivo testing on a human patient with the calibration phantom (PMMA) test results. The spread of values for the patient, compared to the PMMA Phantom, is larger due to the natural heterogeneity of the bone. This is why at least five tests are conducted in vivo on humans: to reduce the error of the mean below the value that typically separates one patient from another.

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Fig. 3

BMS values of ex vivo human samples comparing through tissue tests to tests performed on exposed bone. The data suggests that there is no significant difference in BMS values between these two methods of indentation (p > 0.25), which is vital because it demonstrates the Osteoprobe®'s consistency between through tissue and exposed bone tests, typical of in vivo and ex vivo testing, respectively.

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Fig. 4

Bone fracture is a serious problem for horses, especially thoroughbred race horses. Here one of us (DH) at Alamo Pintado stables measures the Bone Material Strength of a young, lame thoroughbred horse. He and (KH) each measured both legs and obtained BMS of 80 ± 13.

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