title: Does immobilization after radiofrequency-induced shrinkage influence the biomechanical properties of collagenous tissue? An in vivo rabbit study.
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.
  
  
  OBJECTIVE
  To examine the role of postoperative immobilization after radiofrequency-induced shrinkage, with special emphasis on the biomechanical properties of shrunken collagenous tissue.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  Postoperative immobilization supports recovery of biomechanical properties after shrinkage. Despite immobilization, biomechanical properties of shrunken tissue did not completely reach levels of normal tissue.
  
  
  CONCLUSIONS
  Careful rehabilitation is imperative after radiofrequency-induced shrinkage. This animal model supports an immobilization period of at least 6 weeks after surgery.
authors.affiliation: Department of Orthopaedics, University Hospital Münster, Münster, Germany. poetzl@uni-muenster.de
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Pötzl
authors.forename: Till
authors.initials: T
authors.lastname: Heusner
authors.forename: Philipp
authors.initials: P
authors.lastname: Kümpers
authors.forename: Björn
authors.initials: B
authors.lastname: Marquardt
authors.forename: Jörn
authors.initials: J
authors.lastname: Steinbeck
mesh_terms: D000818:Animals; D001182:Arthroscopy; D001696:Biomechanical Phenomena; D017115:Catheter Ablation / Q000379:methods*; D007103:Immobilization / Q000502:physiology*; D010329:Patella / Q000601:surgery*; D011817:Rabbits; D012307:Risk Factors; D018709:Statistics, Nonparametric; D013710:Tendons / Q000502:physiology* / Q000601:surgery*; D013997:Time Factors