Document Title: Poetzl-AJSM-Apr04.shtml
Article Title: Does Immobilization After Radiofrequency-Induced Shrinkage Influence the Biomechanical Properties of Collagenous Tissue? An In Vivo Rabbit Study
Authors: Wolfgang Pötzl, MD*, Till Heusner, Philipp Kümpers, Björn Marquardt, MD and Jörn Steinbeck, MD
Location: Department of Orthopaedics, University Hospital Münster, Münster, Germany
Publication: American Journal of Sports Medicine, Baltimore, Maryland
Date: April-May 2004
Volume 32, Number 4, pages 681-687
Keywords: thermal shrinkage, knee, Laser/Radiofrequency energy.

(Figures included. Reference-denoting numbers appear in the same point size as the document text.)

Comments: This study looks at thermal shrinkage from a tissue viewpoint, and uses the patellar tendon of the rabbit. Granted, while much experience with thermal shrinkage has been gained in the context of shoulders, this article reveals that there is still much to worry about with regards to the use of thermal shrinkage for ACLs. The authors note that even with carefully done six-week immobilization periods, the treated rabbit tendons failed to completely recover their normal biomechanical properties. Also, it must be remembered that the knee of a rabbit is not subjected to proportionally the same physiological loadings as the human knee. Most notably, the human knee must deal with lever arms (tibia and femur) that are proportionally much longer than their counterparts in the diminutive rabbit; furthermore, humans are bipedal and rabbits are quadrupedal. This means that the thermal-shrinkage-related worries raised by this study are greatly amplified when human knees are being considered.

ABSTRACT

Background: Despite widespread use of radiofrequency-induced shrinkage of collagenous tissue, there have been no animal studies on the effects of postoperative immobilization on the biomechanical behavior of shrunken tissue.

Purpose: To examine the role of postoperative immobilization after radiofrequency-induced shrinkage, with special emphasis on the biomechanical properties of shrunken collagenous tissue.

Study Design: Controlled laboratory study.

Methods: One patellar tendon of 66 New Zealand White rabbits was shrunk. Six rabbits were sacrificed immediately after surgery. Twenty rabbits were not immobilized, twenty were immobilized for 3 weeks, and twenty were immobilized for 6 weeks. The biomechanical parameters failure strength, stiffness, and relaxation were tested.

Results: Nine weeks after surgery, biomechanical parameters were still low compared to control tendons. Shrunken tendons did not reach levels of normal tissue at any time after surgery, regardless of whether the animals had been immobilized. According to time-related development, all biomechanical parameters had the lowest levels 3 weeks after surgery. Immobilized tendons demonstrated a better and faster recovery than nonimmobilized tendons compared to the immediate postoperative level.

Conclusion: Postoperative immobilization supports recovery of biomechanical properties after shrinkage. Despite immobilization, biomechanical properties of shrunken tissue did not completely reach levels of normal tissue.

Clinical Relevance: Careful rehabilitation is imperative after radiofrequency-induced shrinkage. This animal model supports an immobilization period of at least 6 weeks after surgery.

To access the full text of this article, please click here.
There is no charge for viewing articles. However, a password is required.
If you do not already have a password, please e-mail Michael Frind at frind@execulink.com for one.
Prior to requesting a password, please make certain you have read the Site Terms of Use pertaining to this site.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Copyright American Journal of Sports Medicine, American Orthopaedic Society for Sports Medicine, April 2004. For details regarding copyright as it applies to this page, please visit the page entitled "Site Terms of Use and Aspects of Copyright" on this site.

This website was created for the benefit of the world's largest knee-injury community, Bob's ACL WWWBoard (also known as the Kneeboard), accessible to everyone at http://factotem.org.

Documents posted on this site serve merely as a virtual library, and are intended solely for purposes of making access to high-quality peer-reviewed medical-journal articles convenient for all users of the Kneeboard. Knee-injury patients are hereby encouraged to discuss this material with their respective medical teams.

Site Terms of Use and Aspects of Copyright

Printing Hints and Tips