Regenerated cartilage produced by autogenous periosteal grafts: a histologic and mechanical study in rabbits under the influence of continuous passive motion.

PURPOSE

To evaluate the repaired tissues formed in full-thickness cartilage defects in a rabbit model implanted with autogenous periosteal grafts under the influence of continuous passive motion (CPM) establishing a correlation between histology, histomorphometry, and mechanical behavior.

METHODS

Autogenous periosteal grafts were used to resurface full-thickness defects produced in the trochlear groove in the right knees of 60 New Zealand rabbits. Four groups were formed according to the time to death and postoperative mobilization: group A--active intermittent motion, euthanized at 8 weeks; group B--CPM, euthanized at 8 weeks; group C--active intermittent motion, euthanized at 36 weeks; and group D, CPM, euthanized at 36 weeks. Repaired tissues were evaluated grossly, histologically, and mechanically, as well as by histomorphometry.

RESULTS

The repair tissue was hyaline-like cartilage in 68.1% of the specimens in group A, 71.4% in group B, 0% in group C, and 20% in group D. The mean thickness of the regenerated tissue was 1.20 mm in group A, 1.23 mm in group B, 0.20 mm in group C, and 0.25 in group D. Elastic stiffness at 8 weeks was lower than that of the control cartilage and increased significantly at 36 weeks because of degenerative changes. Postoperative motion showed no influence on the results. Repaired tissue developed severe degenerative changes in time, and deterioration of the mechanical properties was observed without any protective effect of the CPM.

CONCLUSIONS

Full-thickness cartilage defects treated with autologous periosteal grafts were repaired with hyaline-like cartilage tissue. Regenerated tissue showed viscoelastic behavior similar to normal cartilage 8 weeks after surgery. CPM did not improve histologic or mechanical results. Repaired tissue did not last over time.

CLINICAL RELEVANCE

Free periosteal grafts should not be used clinically in the treatment of full-thickness cartilage defects because even though regenerated tissue seems initially to be hyaline-like cartilage, it is not capable of maintaining its histologic and mechanical properties over a long period of time.