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Relevance of the Spatial Distribution Pattern of Mechanical Properties of Articular Cartilage in Animal Studies S. Sim 1,2 I. Hadjab 1,2 A. Chevrier 1 M. Garon 2 E. Quenneville 2 M.D. Buschmann 1 1. Biomedical & Chemical Engineering,

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SLIDE 1

Relevance of the Spatial Distribution Pattern of Mechanical Properties of Articular Cartilage in Animal Studies

12th ICRS World Congress May 08-11 2015

  • S. Sim1,2
  • I. Hadjab1,2
  • A. Chevrier1
  • M. Garon2
  • E. Quenneville2

M.D. Buschmann1

  • 1. Biomedical & Chemical Engineering, Polytechnique Montreal, Montreal, QC, Canada
  • 2. Biomomentum Inc., Laval, QC, Canada
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SLIDE 2

D isclosure

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

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SLIDE 3

In order to evaluate the effect of cartilage treatment, appropriate control and treated sites need to be chosen. However, finding the right location for the control and treated sites is quite challenging in articular surfaces where a natural spatial distribution of mechanical properties and thickness is present in all healthy joints (Setton et al., 1994; Räsänen et al., 1996 ).

I ntroduction

Lateral Medial Treatment site Control site

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SLIDE 4
  • Non-destructive
  • Allows for multiple

testing

  • Allows for subsequent

analyses

  • Cartilage need to be harvested from the

articular surface

  • Disruption
  • f

the articular surface and mechanical environment

  • Difficult to properly extract cores from repaired

cartilage lesions in animals

Common mechanical test configurations

Unconfined Compression

impermeable impermeable

I ntroduction

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SLIDE 5

The purpose of this study was to assess the importance of considering the spatial distribution of the mechanical properties of normal articular cartilage in animal models

  • f cartilage repair, specifically the

distributions of thickness and instantaneous modulus.

I ntroduction

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SLIDE 6
  • Skeletally mature animals
  • Tibial plateau
  • Femoral condyles
  • Right and left joints
  • Visually normal articular surfaces

M

ethods

n= 1 4-5 years n=3 13-14 weeks

Sheep Rabbit

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SLIDE 7

Camera-registration system

Mechanically-controlled surface mapping Sample Top view image (1280x960 pixels) Position grid superimposed Converts in units of length (mm) Multiaxial Mechanical Tester input

M

ethods

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SLIDE 8

Mechanical testing by an automated indentation technique

  • 3-axis mechanical tester (Mach-1 v500css from Biomomentum)
  • Multiaxial load cell (force resolution: Fz = 0.35 gf and Fx = Fy = 0.25 gf)
  • Spherical indenter (r = 0.5 mm)

M

ethods

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SLIDE 9

Automated indentation technique

Perpendicular Indentation at each position

Thickness is missing

Contact coordinates (x,y,z) of predefined positions and 4 surrounding positions Surface orientation (θz) Normal force/displacement vs time

M

ethods

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SLIDE 10

Automated indentation technique

Perpendicular Indentation at each position

Thickness is missing

Contact coordinates (x,y,z) of predefined positions and 4 surrounding positions Surface orientation (θz) Normal force/displacement vs time

M

ethods

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SLIDE 11

Automated indentation technique

Perpendicular Indentation at each position

Thickness is missing

Contact coordinates (x,y,z) of predefined positions and 4 surrounding positions Surface orientation (θz) Normal force/displacement vs time

M

ethods

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SLIDE 12

Automated indentation technique

Perpendicular Indentation at each position

Thickness is missing

Contact coordinates (x,y,z) of predefined positions and 4 surrounding positions Surface orientation (θz) Normal force/displacement vs time

M

ethods

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SLIDE 13

Automated indentation technique

Perpendicular Indentation at each position

Thickness is missing

Contact coordinates (x,y,z) of predefined positions and 4 surrounding positions Surface orientation (θz) Normal force/displacement vs time

M

ethods

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SLIDE 14

Vertical Distance

Thickness = vertical distance x cosine (surface orientation) Surface orientation Cartilage surface Subchondral bone

M

ethods

Automated Thickness measurement

Replace the spherical indenter with a needle

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SLIDE 15

Indentation analysis

Instantaneous Modulus (MPa)

Elastic Model in Indentation (Hayes, 1972)

Using the known thickness Perpendicular Force (N)

𝐽𝑁 = 𝑄 𝐼 ∙ (1 − 𝑤2) 2𝑏𝑙 (𝑏 ℎ ∙ 𝑤)

Perpendicular Displacement (mm)

M

ethods

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SLIDE 16
  • Large variation

within the medial and lateral compartment of femoral condyle and tibial plateau.

  • The cartilage is

thinner in regions covered by the meniscus while a thicker cartilage is

  • bserved on the

rest of the surface.

R esults

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SLIDE 17
  • Large variation

within the medial and lateral compartment of femoral condyle and tibial plateau.

  • The cartilage is

stiffer in regions covered by the meniscus while a softer cartilage is

  • bserved on the

rest of the surface.

R esults

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SLIDE 18
  • Measured thickness agrees with those reported in the

literature (Stockwell et al., 1971).

D iscussion

  • The instantaneous modulus and thickness mappings

measured show similar distribution patterns than those previously observed for the stifle joints of larger species, with stiffer and thinner cartilage in the region covered by the meniscus (Sim et al., 2013), suggesting a dependence with weight bearing and kinematics (Fukubayashi et al., 1980) for all species.

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SLIDE 19
  • Considering these results, major concern arise:
  • Treatments may not be comparable if the chosen regions

initially have different properties.

D iscussion

1.8 ± 0.3 MPa 8.9 ± 4.0 MPa

Lateral Medial

MPa

Anterior Posterior

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SLIDE 20

D iscussion

  • Considering these results, major concern arise:
  • Cartilage thickness and instantaneous modulus can vary by a

factor up to 10 over a distance of only 5% of the total articular surface width.

Lateral Medial MPa

  • These thickness and modulus maps clearly show that any

difference between treated and non-treated cartilage could be confounded with the natural topographic variability rather than due to the treatment itself.

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SLIDE 21

C onclusion

By considering the spatial distribution

  • f cartilage properties when choosing

control and treated sites, the effects of treatment may be more easily discerned.

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SLIDE 22
  • Funding provided by the National Sciences and Engineering

Research Council (NSERC) and the Fonds québécois de la recherche sur la nature et les technologies (FQRNT).

  • Rat samples were provided by Simon Authier from

CiToxLAB.

  • Rabbit samples were provided by Anik Chevrier from the

Biomaterials and Cartilage Laboratory (BCL).

A knowledgements

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SLIDE 23
  • Setton 1994, J Orthop Res 12:451
  • Räsänen 1996, J Biomed Mater Res 31:519
  • Jurvelin 1995, J Biomech 28: 231
  • Hayes 1972, J Biomech 5:541
  • Stockwell 1971, J Anat 3:411
  • Sim 2013, Trans ORS2013: poster 1975
  • Fukubayashi 1980, Acta Orthop Scand 51(6):871

R eferences

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SLIDE 24

O ther presentations

  • Correlation of Traditional and Novel Outcome Measures for the Assessment of

Regenerated Osteochondral Tissue in a Sheep Model. Poster #83

  • Evaluation of Entire Ovine Cartilage Repair Articular Surfaces: Mechanical and

Electromechanical Assessment. Poster #87

  • Correlation of Non-destructive Electromechanical Probe (Arthro-BST) Assessment

with Histological Scores and Mechanical Properties in Human Tibial Plateau. Presentation #23.2.8

  • Mapping Articular Cartilage Biomechanical Properties of Normal & Osteoarthritis

Mice Using Indentation. Presentation #23.2.9