Wear versus thickness and other features of 5-Mrad crosslinked UHMWPE acetabular liners.

Background: The low wear rates of crosslinked polyethylenes provide the potential to use larger diameters to resist dislocation. However, this requires the use of thinner liners in the acetabular component, with concern that higher contact stresses will increase wear, offsetting the benefits of the crosslinking.

Questions/purposes: We asked the following questions: Is the wear of conventional and crosslinked polyethylene liners affected by ball diameter, rigidity of backing, and liner thickness? Are the stresses in the liner affected by thickness?

Methods: Wear rates were measured in a hip simulator and stresses were calculated using finite element modeling.

Surface-gradient cross-linked polyethylene acetabular cups: oxidation resistance and wear against smooth and rough femoral balls.

Two methods were developed and evaluated for cross-linking the bearing surface of a polyethylene acetabular cup to a limited depth, in order to improve its resistance to wear without degrading the mechanical properties of the bulk of the component. In the first method, low-energy electron beams were used to cross-link only the bearing surface of the cups to a maximum depth of about 2 mm. The cups then were annealed at 100 degrees C in vacuum for 3 or 6 days to reduce the residual free radicals, and the resultant resistance to oxidation was compared by artificially aging the cups at 80 degrees C in air.

Biologic and tribologic considerations of alternative bearing surfaces.

Patients who are young or active or both who require total joint replacement pose a unique challenge; their high activity demands wear-resistant bearings that will perform for decades, without suffering from the adverse effects of accumulated wear products. We discuss the tribologic and biologic properties of newly introduced bearing materials for hip prostheses. The new PEs are intended to address the aseptic loosening problem by reducing the volume of submicron PE particles to a level well below that historically associated with osteolysis.

Monitoring the degradation process of biopolymers by ultrasonic longitudinal wave pulse-echo technique.

A non-destructive ultrasonic longitudinal wave pulse-echo technique was utilized to monitor the degradation process of three biodegradable polymers: poly(glycolic acid) (PGA), poly(L-lactic acid) (PLLA) and 50:50 poly(D,L-lactide-co-glycolide) (PDLLG). The degradation processes of PGA and PLLA, which have different molecular structure, were also studied by differential scanning calorimetry (DSC). The degradation processes of PDLLG specimens prepared by different methods were characterized by the ultrasonic wave technique and gel permeation chromatography (GPC).

Interaction of oxidation and crosslinking in gamma-irradiated ultrahigh molecular-weight polyethylene.

The interaction between oxidation and crosslinking in gamma-irradiated ultrahigh molecular-weight polyethylene with and without artificial aging was studied. The effect of the atmosphere during irradiation (air vs. low oxygen) occurred primarily within about 0.