ANATOMIC AND MECHANICAL-PROPERTIES OF THE LATERAL DISC ATTACHMENT OF THE TEMPOROMANDIBULAR-JOINT

Purpose: This study measured the strength to failure of the human temp oromandibular joint (TMJ) lateral disc attachment (LDA) using a tensio n-compression machine. These data were correlated with the LDA locatio n and its morphologic aspects, the age-and sex of the subjects, and th e amount of the lateral pterygoid muscle (LPM) inserted in the disc. M ethods: Forty-two TMJs without any obvious internal damage were carefu lly dissected to preserve the LDA. The width of insertion of the later al pterygoid muscle fibers in the anterior band, as well as the width of the disc, were measured. The tension test was performed until the c omplete failure of the sample using a screw machine. Results: Two type s of LDA were recognized. In LDA 1, the anterior and posterior bands l ateral disc junction were directly inserted on the lateral pole, where as in LDA 2 this lateral junction was attached behind and below the po le through a sheet of fibrous tissue. The breaking points for LDA 1 (5 5.8 N) and LDA 2 (28.8 N) were significantly different (P = .03). No c orrelation was found between the amount of LPM discal fibers insertion , sex, age, or the LDA breaking strength point. Conclusion: The LDA 2 insertion strongly suggests that the lateral joint ligament together w ith the capsule may act as a substitute for the original disc attachme nt to the lateral pole of the condyle.