Radiofrequency treatment weakens the fatigue characteristics of rabbit anterior cruciate ligament

Abstract

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).

Conclusions: Using radiofrequency treatment makes rabbit anterior cruciate ligament weaker following cyclic loading.

Relevance: The radiofrequency treatment weakens the anterior cruciate ligament, and therefore, it perhaps should be protected until healing and adaptation restore its full strength.