Comparison of three joint simulator wear debris isolation techniques: Aciddigestion, base digestion, and enzyme cleavage

Quantification of ultrahigh molecular weight polyethylene (UHMWPE) wear deb ris remains a challenging task in orthopedic device analysis. Currently, th e weight loss method is the only accepted practice for quantifying the amou nt of wear generated from a PE component. This technique utilizes loaded so ak controls and weight differences to account for polymeric material lost t hrough wear mechanisms. This method enables the determination of the amount of wear in the orthopedic device, but it provides no information about deb ris particulate size distribution. In order to shed light on wear mechanism s, information about the wear debris and its size distribution is necessary . To date, particulate isolation has been performed using the base digestio n technique. The method uses a strong base, ultracentrifugation, and filtra tion to digest serum constituents and to isolate PE debris from sera. It sh ould be noted that particulate isolation methods provide valuable informati on about particulate size distribution and may Elucidate the mechanisms of wear associated with polymeric orthopedic implants; however, these techniqu es do not yet provide a direct measure of the amount of wt ar. The aim of t his study is to present alternative approaches to wear particle isolation f or analysis of polymer wear in total joint replacements without recourse to ultracentrifugation. Three polymer wear debris isolation techniques (the b ase method, an acid treatment, and an enzymatic digestion technique) are co mpared for effectiveness in simulator studies. A requirement of each techni que is that the wear particulate must be completely devoid of serum protein s in order to effectively image and count these particles. In all methods t he isolation is performed through filtration and chemical treatment. Subseq uently, the isolated polymer particles are imaged using scanning electron m icroscopy and quantified with digital image analysis. The results from this study clearly show that isolation can be performed without the use of ultr acentrifugation and that these methods provide a viable option for wear deb ris analysis. (C) 2001 John Wiley & Sons, Inc. J Biomed Mater Res 56: 245-2 49, 2001.