Electrothermal shrinkage reduces laxity but alters creep behavior in a lapine ligament model

Thermal denaturation of collagen in ligament tissue hers the potential to e nhance arthroscopic shoulder stabilization. Previous studies have shown tha t laser energy produces significant capsular shortening without alteration of viscoelastic properties, but little information is available on the effe cts of radio frequency electrothermal energy. We assessed the acute effects of radio Frequency shrinkage with use of the lapine medial collateral liga ment model, in which the tibial insertion was shifted proximally to produce abnormal laxity Thermal treatment resulted in restoration of laxity from 3 .33 +/- 0.25 mm to 0.66 +/- 0.31 mm, which was not significantly different from medial collateral ligaments replaced anatomically (0.50 +/- 0.34 mm). When tested at 4.1 megapascals, cyclic and static creep strains were increa sed twofold to threefold in thermally-created ligaments (P < .01), and part ial failure occurred in 2 of 8 cases. We conclude that radio frequency elec trothermal shrinkage is effective at reducing laxity but significantly alte rs viscoelastic properties, posing a risk of recurrent stretching-out at "p hysiological" loads.