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Injured rabbit ACL treated by radiofrequency. Effects of cyclic loading
A Merter Ozenci1, Manohar M Panjabi
1Biomechanics Research Laboratory, Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, New Haven, CT, USA.
Background:
Radiofrequency treatment is increasingly used to treat shoulder instability. Patients are asked to restrain their physical activities after this treatment but there is no precise information concerning the necessity for the restrain.
Methods:
There were two groups of ten specimens each. Treatment group specimens were stretched to subfailure injury, treated by a radiofrequency probe, and then cyclically loaded. Control group specimens were stretched to the same subfailure injury, Sham treated, and then cyclically loaded. Between each step of the experiment in both groups there was a relaxation test to examine the ligament viscoelastic properties. At the end, each ligament was stretched to failure and the load-elongation curve obtained.
Findings:
Relaxation forces decreased after the subfailure injury in both groups (average 76% and 81% of intact state, in treatment and control groups, respectively). In the treatment group, the relaxation forces first increased after the radiofrequency treatment (average 99% of intact state), and then decreased after the cyclic loading (average 50% of intact state). The treated ligaments failed at lower loads and smaller deformations than the controls.
Interpretation:
The radiofrequency treatment restored viscoelastic properties of the injured ligaments, but cyclic loading degraded these. Protection of the treated ligament is advised during the immediate post-operative period.
