J. Grant (Ann Arbor, US)

University of Michigan Orthopaedic Surgery

Presenter Of 1 Presentation

Podium Presentation Osteochondral Grafts

10.3.2 - Cartilage Thickness Mismatches In Patellar Osteochondral Allograft Transplants Affect Local Cartilage Deformation

Presentation Topic
Osteochondral Grafts
Date
13.04.2022
Lecture Time
13:00 - 13:00
Room
Bellevue
Session Type
Free Papers
Disclosure
J. Grant: Research funding from JRF Ortho, Arthrex, Aesculap Biologics; consultant for JRF Ortho, Vericel

Abstract

Purpose

The goal of this study was to identify the effect of cartilage thickness mismatches between a graft and the surrounding native bone on cartilage tissue deformation in a human patellar osteochondral allograft model.

Methods and Materials

Two types of finite element models were used to quantify the effect of mismatches in the subchondral bone surface: a simplified 2D model and patient-specific 3D models. In the 2D models, the thickness of the graft cartilage in the graft region was varied from 0.33x the thickness of native cartilage to 3x the thickness of native cartilage, which was set to 2 mm. Ten 3D models were created from nano-CT scans of 16mm cadaveric patellar OCA transplants. A 1 MPa pressure was applied to the cartilage surface, and the patellar surface was fixed for all models.

Results

3D models highlighted which geometric features produced high stress regions in the patellar cartilage and where those stresses occurred. Furthermore, the 3D models provided ranges for the parameter sweeps that were conducted with 2D models. 2D models revealed that larger thickness mismatches with thicker recipient cartilage caused higher stresses. Compared to patellae with donor cartilage that was thicker than recipient cartilage, patellae with donor cartilage than was thinner than recipient cartilage had lower stresses when the recipient cartilage thickness was <4 mm. This trend reversed for recipient cartilage >4 mm. Surface curvature increased stresses when donor cartilage was thicker than recipient cartilage and decreased stresses when donor cartilage was thinner than recipient cartilage.patellar ocas - figure 4a-c.png

Conclusion

Mismatches in the subchondral bone can produce stress increases large enough to cause local chondrocyte death near the subchondral bone surface, highlighting that future monitoring of cartilage transplants should include full-thickness imaging techniques and that allografts should be matched based on cartilage thickness.

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