Radiofrequency treatment weakens the fatigue characteristics of rabbit anterior cruciate ligament

Objective. To evaluate the radiofrequency treatment applied to an intact anterior cruciate ligament, and to quantify the mechanical effects of controlled cyclic loading (simulating activities of daily living) post-treatment. Design. An in vitro radiofrequency energy application to the rabbit anterior cruciate ligament and cyclic loading of the treated ligament. Background. Effect of cyclic loading on the radiofrequency treated ligament in a controlled environment is not known. Methods. In the treatment group radiofrequency treatment was applied to an intact ligament and then the ligament was cyclically loaded for 3000 cycles, and stretched-to-failure. Control group was similar to treatment, except that the radiofrequency treatment was not applied. The cyclic loading (approximately 6% tensile strain) was kept below the injury threshold of the rabbit anterior cruciate ligament and was designed to simulate loading post-treatment. A relaxation test (5% constant strain for 180 s) was used to compare the results at different steps in the experiment; within each group and between the two groups. Results. Relaxation force increased in the treatment group (average 108% of intact, P<0.05), but decreased after the cyclic loading (average 71% of intact, P<0.05). There were significant differences in the force–deformation-failure curves between the treatment and control groups: average treated ligament failed at 59% and 57% of the control values respectively for the deformation and force (P<0.05). Conclusion. Using radiofrequency treatment makes rabbit anterior cruciate ligament weaker following cyclic loading.