Thermal modification of the lax anterior cruciate ligament using radiofrequency: efficacy or catastrophe?

High failure rate for electrothermal shrinkage of the lax anterior cruciate ligament: a multicenter follow-up past 2 years

PURPOSE

The purpose of this study was to prospectively evaluate the midterm results (beyond 2 years) of thermal shrinkage on both lax native anterior cruciate ligament (ACL) and lax reconstructions and determine the effectiveness of this procedure.

METHODS

This is a multicenter study in which 64 patients from 2 sites underwent electrothermal shrinkage for a lax ACL, both native and previous reconstructions. They were followed up past 2 years with KT-1000 measurements (MEDmetric, San Diego, CA). Failure criteria included subsequent operations for instability or KT-1000 measurements greater than 5 mm. Three patients were lost to follow-up.

RESULTS

Among the 61 patients followed up past 2 years, failure occurred in 31 (50.8%). The failure rate for lax grafts alone was 78.9%, and there was a failure rate of 38.1% for lax native ligaments.

CONCLUSIONS

Electrothermal shrinkage of lax native or reconstructed ACLs is not an appropriate treatment.

A structural, kinetic model of soft tissue thermomechanics

A structure-based kinetic model was developed to predict the thermomechanical response of collagenous soft tissues. The collagen fibril was represented as an ensemble of molecular arrays with cross-links connecting the collagen molecules within the same array. A two-state kinetic model for protein folding was employed to represent the native and the denatured states of the collagen molecule. The Monte Carlo method was used to determine the state of the collagen molecule when subjected to thermal and mechanical loads. The model predictions were compared to existing experimental data for New Zealand white rabbit patellar tendons. The model predictions for one-dimensional tissue shrinkage and the corresponding mechanical property degradation agreed well with the experimental data, showing that the gross tissue behavior is dictated by molecular-level phenomena.