Sensitivity of Indentation Testing to Step-Off Edges and Interface Integrity in Cartilage Repair

Abstract

Step-off edges and tissue interfaces are prevalent in cartilage injury such as after intra-articular fracture and reduction, and in focal defects and surgical repair procedures such as osteochondral graft implantation. It would be useful to assess the function of injured or donor tissues near such step-off edges and the extent of integration at material interfaces. The objective of this study was to determine if indentation testing is sensitive to the presence of step-off edges and the integrity of material interfaces, in both in vitro simulated repair samples of bovine cartilage defect filled with fibrin matrix, and in vivo biological repair samples from a goat animal model. Indentation stiffness decreased at locations approaching a step-off edge, a lacerated interface, or an integrated interface in which the distal tissue was relatively soft. The indentation stiffness increased or remained constant when the site of indentation approached an integrated interface in which the distal tissue was relatively stiff or similar in stiffness to the tissue being tested. These results indicate that indentation testing is sensitive to step-off edges and interface integrity, and may be useful for assessing cartilage injury and for following the progression of tissue integration after surgical treatments.

Analysis of Stored Osteochondral Allografts at the Time of Surgical Implantation

“…On this scale, a relatively low value indicates a relatively soft sample. 3,4,21 Statistical Analysis For statistical analysis, t tests were used to compare control and experimental values, and analysis of variance was used to compare cell viability of cartilage zones. Significance was set at P = .05 for all tests.…”

Bone Screws Have Advantages in Repair of Experimental Osteochondral Fragments

“…The suppression of degeneration of the surrounding cartilage adjacent to the defect site with bone screws was unexpected. We suggest edge effects attributable to the chondral defects were decreased because of maintenance of repaired chondral tissue at the defect site [2] and degeneration of the surrounding cartilage tissues therefore might be prevented.…”

“…The stiffness of repaired tissue and surrounding cartilage was tested on each screw hole in Group B and Group P. We ensured specimens for histologic evaluation and biomechanical testing did not overlap. We pressurized with a cylindrical probe (0.66-mm diameter) at a speed of 0.01 mm/second as previously described [2,10,17]. Combined tissue stiffness was measured from the linear phase of the stress-strain curve.…”

Reconstruct large osteochondral defects of the knee with hIGF-1 gene enhanced Mosaicplasty

“…At the donor sites, multiple cells embedded within the gel integrated with the adjacent cartilage well, and filled deeply into the defects, leaving a regular surface. The ultimate success for repair osteochondral defects may require the integration with surrounding cartilage in order to maintain biomechanical integrity [1,11,15,37]. That means no "dead space" would be more valuable to the ultimate long-term outcome.…”