Abstract
Radio frequency (RF) electrothermal capsulorrhaphy has potential to enhance the results of arthroscopic stabilisation. However, early clinical reports have shown variable results when compared with open stabilisation. Numerous experiments have shown that the mechanical properties of thermally treated tissue are mechanically inferior to normal tissue during the early phase of remodelling. Ultimately, the real issue is how thermally treated tissue compares with tissue shortened by surgical plication, as would occur in an open procedure.
Using a validated technique the tibial insertion of the medial collateral ligament (MCL) of the knee was shifted proximally to induce abnormal laxity in 30 mature NZ White rabbits. Bipolar RF shrinkage was applied to the MCL in 15 rabbits, while in the remainder the MCL was surgically transected and plicated with a nonabsorbable suture. Unlimited mobilisation was permitted until euthanasia at 12 weeks after surgery. Bone-ligament-bone complexes were harvested and underwent low-load (viscoelastic) and high-load (tensile failure) analysis on an Instron mechanical testing apparatus. Specimens from intact MCLs were also collected for polarised light microscopy and transmission electron micrography. Quantitative analysis of collagen fibril morphology was performed on the TEM images.
There were no significant complications postoperatively. In both groups there was evidence of ligament healing and remodelling with a thin layer of scar tissue surrounding the MCL. Preliminary analysis has demonstrated that the cross-sectional area of the thermally treated MCLs was increased compared with the plicated MCLs. Somewhat surprisingly, the plicated group had greater vascularity and cellularity in the healing zone than the thermal group. Although crimp patterns remained disorganised in both groups, the collagen matrix appeared more organised in the thermal group.
These results support the concept that the thermally denatured matrix may act as a scaffold for rapid remodelling of the MCL, resulting in a larger mass of ‘scar’ tissue at the site of shrinkage. Since scar tissue following surgical transection is known to be materially inferior to normal ligament tissue, the increased volume in the thermal group may confer an advantage in structural terms. Mechanical testing is presently underway in our laboratory to determine this issue.
The abstracts were prepared by Mr Roger Emery. Correspondence should be addressed to him at the British Orthopaedic Association, Royal College of Surgeons, 35-43 Lincoln’s Inn Fields, London WC2A 3PN
