A model for temporomandibular joint disc repositioning surgery

Purpose: The present study establishes a model of reversible anterior disc displacement using the rabbit craniomandibular joint (CMJ) and examines the period required for successful disc repositioning surgery. Materials and Methods: The left CMJ was exposed surgically in 27 animals an d a suture positioned at the posterolateral portion of the disc was pulled in an anterior direction causing 7 min of anterior disc displacement. The s uture was then fixed to the zygomatic arch. The changes in the CMJ were obs erved microscopically in 3 rabbits each at 2, 3, 5, 8, and 24 weeks. Anothe r 12 rabbits underwent secondary disc repositioning surgery either the seco nd and third week after disc displacement, and then 3 rabbits from each gro up were assessed microscopically at 5 to 6 weeks and 21 to 22 weeks after t he first operation. Ten rabbits had a sham operation, and 2 served as unope rated controls. Histomorphometric evaluation included changes in morphology , cartilage, and disc condition. Results: Progressive osteoarthritic change was induced by disc displacement . Articular disc perforation at 5 weeks after the first operation was accom panied by subchondral bone exposure. The CMJ morphology was almost normal i n rabbits that underwent secondary disc repositioning 2 weeks after disc di splacement. However, osteoarthritic changes and perforated discs similar to those in rabbits that did not undergo secondary disc repositioning were se en in animals in which repositioning was done in the third week. Conclusion: Artificial disc displacement in the rabbit causes osteoarthriti c changes are reversible when the displaced disc is restored within after 2 weeks but not at 3 weeks. (C) 2001 American Association of Oral and Maxill ofacial Surgeons.