SYMPOSIA PAPER Published: 01 January 1998

Quantitative Analysis of Extraneous Matter in Fabricated Ultra-High Molecular Weight Polyethylene (UHMWPE)


The existence of extraneous particles in both extruded and compression molded ultra-high molecular weight polyethylene (UHMWPE) is a leading cause of scrap during the fabrication of orthopaedic implants from the material. ASTM Specification for Ultra-High-Molecular-Weight Polyethylene Powder and Fabricated Form for Surgical Implants (F 648-96) permits a given level of extraneous particles in both the resin and fabricated forms. However, material with particulate levels at the top end of the specification would result in an average of one to two particles open to the surface of each tibial or acetabular implant. Due to the application of UHMWPE as a wear surface in joint replacement surgeries, it is unacceptable for a product to have any particles open to the surface. As a result, most material would be rejected if it ran at the upper level of the specification. This research determined that the use of a volume counting method coupled with statistical process control tools and control parameters based on historical performance is superior to the current surface count analysis used in ASTM F 648 to determine the cleanliness of the fabricated material.

Author Information

Fesmire, RS
Quality Control Systems, Smith & Nephew Orthopaedics, Memphis, TN
Asiala, SP
Poly Hi Solidur, Fort Wayne, IN
Evans, MA
Poly Hi Solidur, Fort Wayne, IN
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Developed by Committee: F04
Pages: 24–29
DOI: 10.1520/STP11907S
ISBN-EB: 978-0-8031-5379-0
ISBN-13: 978-0-8031-2482-0