Abstract
Osteochondral autogenous transfer is an accepted treatment for the management of osteochondral defects in the knee. Concerns about donor site morbidity and kissing lesions of the patella lead us to assess the efficacy of filling donor sites with bioabsorbable bone cement in a sheep model. Donor sites were assessed two, eight and sixteen weeks postoperatively using macroscopic scoring, histology and creep indentation testing. At eight and sixteen weeks after graft harvest there were fewer patellar kissing lesions in the treatment group. Control defects had more extrinsic repair whereas cartilage flow was the predominate source of repair tissue in the treated group.
The purpose of this study was to determine if Norian SRS® bone cement can mitigate donor site morbidity in a model of osteochondral transplantation in the knee.
Ten sheep were assigned to either a control or experimental group. Under general anesthesia and aseptic technique, four donor site defects were created in standardized non-weightbearing regions of the trochlear ridge. These defects measured 4.5 mm in diameter x 10 mm deep. Norian SRS bone cement was used to fill donor site defects up to the level of the tidemark in five experimental sheep. In the control group (n=5), donor sites were left unfilled. One sheep from each group was sacrificed two weeks postoperatively and two sheep from each group were sacrificed at eight and sixteen weeks. Macroscopic scoring, histology and biomechanical creep indentation were used to assess the knee joints.
At eight weeks, treated defects had more filling by facilitating cartilage flow, yielding fewer kissing lesions on the patella. At sixteen weeks, the treated group had more cartilage flow but little extrinsic repair. The control group defects had a more uniform fill with repair tissue and better biomechanical properties but kissing lesions on the patella remained problem.
Short-term results suggest that unfilled donor sites allow better extrinsic repair at the expense of creating kissing lesions. Norian SRS cement reduced kissing lesions on the patella.
Norian SRS was a barrier to extrinsic repair but supported cartilage flow. Cartilage flow in thicker, human cartilage will be greater. It may be possible to support cartilage flow and still allow extrinsic repair by applying Norian SRS up to but not including the tidemark.
Funding: The authors received funding from Synthes, Canada for this project. Thanks to Deb McWade for technical assistance.
Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada
