Surface Damage in Machined Ram-Extruded and Net-Shape Molded Retrieved Polyethylene Tibial Inserts of Total Knee Replacements

Gamma Inert Sterilization: A Solution to Polyethylene Oxidation?

“…Nevertheless, considerable mechanical degradation has been reported to occur at lower oxidation levels for historical polyethylene inserts produced from 1900H resins with respect to those manufactured from GUR resins 15 . Moreover, although historical direct-compression-molded 1900H components have been reported to be oxidation and damageresistant [25][26][27][28] , recent studies also have demonstrated no significant difference in the wear performance of conventional polyethylene components and non-irradiated specimens manufactured from different resins and with various consolidation methods 29,30 , 1900H and direct compression molding among them.…”

Current Modes of Failure in TKA: Infection, Instability, and Stiffness Predominate

“…At 5-year followup, wear-related failures were 1.1% in inserts sterilized in inert gas versus 8.3% in knees with inserts sterilized in air. Berzins et al [1] reported less polyethylene surface damage in tibial inserts manufactured by net-shaped molding in the absence of calcium stearate compared with those inserts manufactured by ram extrusion with calcium stearate additive.…”

Orthopedic Implant Retrieval and Failure Analysis

“…Significant implant failure was observed with components that were manufactured using machined ram-extruded polyethylene [84][85][86][87][88][89]. Berzins et al proposed that net-shaped molded components may have demonstrated superior performance relating to the type of resin, the absence of calcium stearate, the consolidation method, or the method of final geometry shaping [84].…”

“…Berzins et al proposed that net-shaped molded components may have demonstrated superior performance relating to the type of resin, the absence of calcium stearate, the consolidation method, or the method of final geometry shaping [84].…”

“…There appears to be an initial "bedding in" period that is not related to wear per se [102][103][104]. Patterns of wear can be polar or edge loaded with high and low areas [84,105]. There is a risk of fracture with increased polyethylene wear in the critical weight bearing area [101,106].…”