Histologic changes associated with experimental partial anterior disc displacement in the rabbit temporomandibular joint

Aims: To correlate histologic changes with the stress developed by various disc interferences via a model of partial anterior disc displacement in the rabbit temporomandibular joint (TMJ). Methods: Eighteen male New Zealand r abbits were operated on to expose the temporomandibular disc without severi ng its attachments. A suture was passed around the lateral part of the disc over the condylar attachments and the 2 strands were fixed in the orbital cavity. In 9 rabbits, a resorbable suture was used to secure the disc displ acement. In the other 9, a nonresorbable suture was fixed with a nickel-tit anium spring to displace and maintain tension on the disc. Three non-operat ed animals served as controls. The animals were sacrificed at 12 and 24 wee ks after surgery, and the TMJs were prepared for undecalcified histology. R esults: In the first group, the disc remained in a normal position, but its morphology was modified and small histologic changes were observed in the cartilage. In the second group, the disc was displaced in various positions corresponding to the strength delivered by the spring. Conclusion: Adaptiv e changes were observed in joints with a slightly displaced disc, while deg enerative changes were associated with larger disc displacements. In each e xperimental joint, histologic changes increased from the medial to lateral parts. This phenomenon was related to the stress gradient induced by axial disc rotation over the condyle. Any disc displacement always resulted in ch anges in the cartilage.