ARUP; ISBN: 978-0-9562121-5-3 - CMBBE 2012 - Cardiff University

4.3 Osteochondral defect treatment model
The osteochondral defect treatment model showed that the presence of the teZCC could
help to lower the interface shear stress due to misalignment of the implanted construct.
Without the teZCC, the implanted construct, with the bottom of the hydrogel aligned
with the bottom of the host cartilage, will endure a maximal shear stress at the hydrogelscaffold
interface of 0.15 MPa (Fig 4AB) under 10% deformation of zone 5. The
presence of teZCC reduced the maximal stress to about 5 kPa (Fig 4AB).
Figure 4: Osteochondral defect treatment model. Maximum shear stress at teZCChydrogel
interface (A) and at scaffold-teZCC interface (B) at 0.1 mm deformation
(10%) and different teZCC thicknesses.
Using the results from 4.2, the engineered construct without teZCC (55 kPa maximum
shear stress limit) would not resist the 0.15 MPa of maximal shear stress. On the other
hand, the engineered construct with teZCC (60 kPa maximum shear stress limit) would
resist the 5 kPa of maximal shear stress.
5. DISCUSSION
The zone of calcification is crucial for the fabrication of a functional osteochondral
construct. The teZCC confers both strength and anchorage of the hydrogel to the
scaffold. Indeed, the modeling and the in vitro test confirmed that the teZCC resulted in
a stronger interface.
Based on the developed numerical model, the presence of the teZCC would reduce the
interface shear stress under a push-off test. The teZCC would indeed mitigate the
difference in mechanical properties between both materials at the interfaces, which
would induce a lower shear stress [13]. During the push-off test, the shear stress is most
reduced at the teZCC-hydrogel interface than at teZCC-scaffold interface. Indeed, the
mechanical properties of the teZCC are closer to that of the hydrogel than the scaffold,
which creates a smaller gradient at the teZCC-hydrogel interface than at teZCC-scaffold
interface.
The osteochondral defect treatment model shows that the presence of the teZCC in the
construct would also reduce the interface stress at both interfaces. This corroborates the
findings discussed above in that the teZCC would smoothen the gradient of mechanical