Changes in Condylar Coefficient of Friction After Osteochondral Graft Transplantation and Modulation With Hyaluronan
Received 12 June 2008; accepted 22 April 2009. published online 18 September 2009.
Purpose
To better understand the changes in the cartilage coefficient of friction (COF) after an osteochondral repair, an assessment of dynamic loads has been developed using a goat knee model. The application of hyaluronan (HA) was also assessed for its lubricative properties and the resulting COF of the knee after osteochondral repair.
Methods
A total of 18 caprine knees were dissected and mounted into an Instron load frame (Instron, Norwood, MA) for testing. The COF was measured in 10 knees relative to the normal, unaltered joint and then calibrated to account for friction of the system. These experimental knees were tested in 5 modes: normal; empty 4.5-mm defect; and osteochondral repairs that were elevated, flush, or depressed relative to the cartilage surface. Saline solution lavage kept the knees moist during testing. The effect of HA was evaluated after mechanical testing. Eight knees were used to study the effect of lavage on the joints because of the significant increase in the COF that it produced.
Results
Whereas all modes increased the COF from normal levels, the most significant changes occurred when there was proud placement. Increases of 4 times the normal friction levels were measured. Increases in the COF were also associated with saline solution lavage (0.006 to 0.046). There was a significant reduction in friction after HA injection, which reduced the COF to near-normal levels.
Conclusions
There is a significant increase in the COF associated with saline solution lavage and an osteochondral plug being left proud, which can be temporarily reduced with a lubricative material such as HA.
Clinical Relevance
Dramatic increases in the COF can potentially damage chondrocytes when the patient begins articulating the joint after surgery. Such injuries may affect the ability of the cartilage to heal fully. Reducing the elevated COF with lubricating materials, such as HA, is recommended based on the results of this study.
Department of Orthopaedic Surgery, University of California, San Diego, La Jolla, California, U.S.A.
Address correspondence and reprint requests to John G. Lane, M.D., Department of Orthopaedic Surgery, University of California, San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0863, U.S.A.
Supported by the Musculoskeletal and Joint Research Foundation, San Diego, California. The work was performed in the authors' affiliated laboratories, UCSD Dept Ortho Surg Connective Tissue Biochemistry Laboratories. The authors report no conflict of interest.
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