Properties with Histological Scores and Mechanical Properties in - PowerPoint PPT Presentation

Correlation of Electromechanical Properties with Histological Scores and Mechanical Properties in Human Tibial Plateau S. Sim 1,2 A. Chevrier 1 M. Garon 2 E. Quenneville 2 M.D. Buschmann 1 1. Biomedical & Chemical Engineering, Polytechnique Montreal, Montreal, QC, Canada 2. Biomomentum Inc., Laval, QC, Canada 12 th 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:  dGEMRIC  T2 mapping Quantitative MRI  T1rho mapping  Sodium MRI  Ultrasound imaging  Optical reflection spectroscopy Arthroscopy  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 Streaming potentials in a network of collagen fibrils

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 Visual Assessment ICRS Grade > 0 ICRS Grading Electromechanical Assessment Arthro-BST TM Extraction of cores Tubular chisels Unconfined compression of cores Mach-1 TM Histological assessment of cores Mankin score

M ethods Visual Assessment Normal ICRS Grade > 0 Degraded

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) Time (s) Soulhat et al., 1999 Fibril modulus (E f ) Equilibrium modulus (E m ) 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 :  E f (r=− 0.73, p<0.0001)  permeability log (k) (r=0.64, p<0.0001) Weak correlations between QP and:  E m (r=− 0.30, p=0.0186)  thickness of AC (r=0.42, p=0.0006) The electromechanical QP decreases with increasing E f and E m whereas the electromechanical QP increases with permeability and thickness, as expected.

R esults Electromechanical QP vs. Histology Mankin 0 Mankin 3 Mankin 8 QP = 8 QP = 15 QP = 22  Strong correlation between electromechanical QP and Mankin score (r = 0.50, p = 0.0004) Safranin O/Fast Green stained sections showed that GAG staining in the cartilage matrix and structural integrity decreased as the electromechanical QP increased, corresponding to weaker electromechanical properties.

D iscussion  Measured electromechanical QP in human tibial plateau correlated significantly with mechanical parameters and with the histological Mankin score, similar to what was found previously in human distal femurs (Sim et al., 2014).  A weak correlation was found between the electromechanical QP and the thickness of the cartilage on tibial plateau (no correlation was observed on distal femurs (Sim et al., 2014)). This might be related to the fact that there is more variation in the thickness of the tibial plateau surface than distal femurs.

C onclusion  These results demonstrate that the Arthro-BST QP correlates with mechanical parameters and histological Mankin score in the tibial plateau.  A significant advantage is the non-destructive nature of the method allowing for subsequent analysis.  The Arthro-BST has been designed for compatibility with arthroscopy, and could be useful in assessing cartilage quality during surgery.

A knowledgements Funding was provided by: - National Sciences and Engineering Research Council (NSERC) - Fonds québécois de la recherche sur la nature et les technologies (FQRNT) - Biomomentum Inc. We acknowledge the technical contributions of: - Geneviève Picard - Viorica Lascau-Coman - Camille Larose - Philippe Martel

R eferences  Matzat 2013, Quant Imaging Med Surg 3 :162  Nieminen 2012, J Magn Reson Imaging 36 :1287  Virén 2010, Ultrasound Med Biol 36 :833  Johansson 2011, Phys Med Biol 56 :1865  Sato 2011, Lasers Surg Med 43 :421  Spahn 2013, Arch Orthop Trauma Surg 133 :997  Frank 1987, J Orthop Res 5 :497  Legare 2002, J Orthop Res 20 :819  Garon 2002, J Biomech 35 :207  Sim 2014, Osteoarthritis and Cartilage 22 :1926  Soulhat 1999, J Biomech Eng 121 :340  Mankin 1971, J Bone Joint Surg Am 53 :523