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.
The left CMJ was exposed surgically in 27 animals and a suture positioned at the posterolateral portion of the disc was pulled in an anterior direction causing 7 mm of anterior disc displacement. The suture was then fixed to the zygomatic arch. The changes in the CMJ were observed microscopically in 3 rabbits each at 2, 3, 5, 8, and 24 weeks. Another 12 rabbits underwent secondary disc repositioning surgery either the second and third week after disc displacement, and then 3 rabbits from each group were assessed microscopically at 5 to 6 weeks and 21 to 22 weeks after the first operation. Ten rabbits had a sham operation, and 2 served as unoperated controls. Histomorphometric evaluation included changes in morphology, cartilage, and disc condition.
Progressive osteoarthritic change was induced by disc displacement. Articular disc perforation at 5 weeks after the first operation was accompanied by subchondral bone exposure. The CMJ morphology was almost normal in rabbits that underwent secondary disc repositioning 2 weeks after disc displacement. However, osteoarthritic changes and perforated discs similar to those in rabbits that did not undergo secondary disc repositioning were seen in animals in which repositioning was done in the third week.
Artificial disc displacement in the rabbit causes osteoarthritic changes are reversible when the displaced disc is restored within after 2 weeks but not at 3 weeks.