Biomomentum | Publication

Correlation of Electromechanical Properties with Histological Scores and Mechanical Properties in Human Tibial Plateau S. Sim1,2 A. Chevrier1 M. Garon2 E. Quenneville2 M.D. Buschmann1 1. Biomedical & Chemical Engineering, Polytechnique Montreal, Montreal, QC, Canada 2. Biomomentum Inc., Laval, QC, Canada

12th ICRS World Congress May 08-11 2015

D isclosure Eric Quenneville and Martin Garon are the owners of Biomomentum Inc.

I ntroduction Current lack in monitoring AC degeneration with accuracy and sensitivity, mostly at an early stage of degeneration where treatments may be useful. Many research groups have focused on techniques to evaluate articular cartilage: Quantitative MRI

   

dGEMRIC T2 mapping T1rho mapping Sodium MRI

Arthroscopy

   

Ultrasound imaging Optical reflection spectroscopy Pulsed laser irradiation Near-infrared spectroscopy

There is still an enduring demand in Orthopaedics for an objective and reliable clinically applicable technique to evaluate articular cartilage tissue health (Spahn et al., 2011).

I ntroduction Our research group has developed the electromechanical probe Arthro-BST Streaming potentials

Electromechanical properties of AC electric fields produced by the cartilage under load

In vitro studies showed that streaming potentials reflect the structure/function and composition of cartilage and are sensitive to degradation. (Frank, 1987) (Legare, 2002) (Garon, 2002)

I ntroduction Origins of streaming potentials?

Mobile Positive Ions

GAG GAG Positive ions In the fluid

E=0 Aggrecan immobilized in a network of collagen fibrils

I ntroduction Origins of streaming potentials? Fluid flow induced by cartilage loading

GAG Positive ions In the fluid

E Aggrecan immobilized in a network of collagen fibrils

Streaming potentials

I ntroduction Streaming potentials are recorded by the Arthro-BST by each microelectrode when the indenter is manually compressed against the articular cartilage surface. The quantitative parameter (QP) corresponds to the number of microelectrodes in contact with the cartilage (contact area) when the sum of their streaming potentials reaches 100 mV. Contact Area on Spherical Tip

mV

Time

 High QP = Weak electromechanical properties

I ntroduction Streaming potentials are recorded by the Arthro-BST by each microelectrode when the indenter is manually compressed against the articular cartilage surface. The quantitative parameter (QP) corresponds to the number of microelectrodes in contact with the cartilage (contact area) when the sum of their streaming potentials reaches 100 mV. Contact Area on Spherical Tip

mV

Time

 Low QP = Strong electromechanical properties

I ntroduction A previous study on human distal femurs (Sim et al., 2014) showed that the electromechanical QP correlated strongly: • with the Mankin score • with unconfined compression parameters (fibril modulus, matrix modulus, permeability) While weaker correlations were observed with the biochemical composition (GAG per wet weight) and water content.

(Sim et al., 2014)

I ntroduction The purpose of this study was to investigate if electromechanical properties of human tibial plateau correlate strongly with histological scores and with mechanical properties as in human distal femurs.

M ethods Samples Six pairs of tibial plateau from human donors (5 males and 1 female, average age 48 years) were provided by RTI Surgical (FL, USA).

M ethods Overview ICRS Grade > 0

Visual Assessment ICRS Grading Electromechanical Assessment Arthro-BSTTM Extraction of cores Tubular chisels Unconfined compression of cores Mach-1TM Histological assessment of cores Mankin score

M ethods Visual Assessment Normal

Degraded

ICRS Grade > 0

M ethods Camera-Registration System + Electromechanical Assessment

M ethods Camera-Registration System + Electromechanical Assessment

16.0 Contact Area on Spherical Tip

M ethods Camera-Registration System + Electromechanical Assessment

7.0 Contact Area on Spherical Tip

M ethods Extraction of cores

  

Harvested from normal and degraded regions Precisely document the location of each core relative to the position grid used for Arthro-BST measurements The QP of each core was calculated as the average of all QPs measured within 6 mm from the core center location

M ethods Unconfined compression on cores 56 cores Thickness measured using a calibrated dissection microscope Using Mach-1 (Biomomentum) mechanical tester Precompression of 10% of thickness Followed by 5 compressions each of 2% of thickness Load (N)

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Time (s)

Soulhat et al., 1999 Fibril modulus (Ef) Equilibrium modulus (Em) Permeability (k)

M ethods Histology on cores    

56 cores Safranin O-Fast Green-stained sections Scored with the Mankin histological-histochemical grading system (Mankin et al., 1971) One blinded observer

Mankin Score

R esults Electromechanical QP vs. Unconfined Compression Strong correlations between QP and :  Ef (r=−0.73, p