h-Adhesive wear:

Adhesive   wear  occurs   when   the   adhesion   between   two 'contactir. surfaces exceeds the cohesive force within one of (he materials (7).

Histologicai analysis of the wear surfaces of surgically retrieved tibia] inserts has shown striated wear patterns with ripples that are oriented perpendicular and parallel to the primary direction of anterior-posterior motion (73).

The origin of participate polyethylene debris may result from the detachment of these striations (72).

It occurs at the primary articulations "(the tibiofemoral and pateilofemoral articulation), and at the backside and the tibial post-c?.^ articulations of posterior stabilized total knee designs (72).

Puloski S. K. et al. reported that adhesive wear or burnishing was the predominant wear mechanism in twenty-three posterior stabilized total knee designs, and that 30% of the inserts exhibited sever damage w>^fb gross loss of polyethylene, primarily in the posterior region of the post

(74).

c-Aorasic wear :

Abrasive wear is characterized by the generation of wear debris from the cuuiug and removal of the soft polyethylene articular surface by hard asperities on the temoral component and by hard third-body particles. such as bone chips or bone-cement particles (72).

Third body wear results from the interposition of a third substance between two contacting surfaces (7).