Table 1.

Digestion protocols to isolate metal wear debris

Study	Year	Digestion	Purification	Display	Image	Total number of particles examined	Measured parameters	Statistics
Schmiedberg et al. [38]	1994	Papain, proteinase K (NaOH wash)	Multiple sequential WCS (7 steps)	Drop evaporation	SEM	20	Length, width	Mean, SD
Doorn et al. [16]*	1998	Papain, proteinase K	Multiple sequential WCS (4 steps)	Nebulization on TEM grid	TEM	1–580	Diameter	Box plots
Tipper et al. [41]	1999	KOH 60°C	Extraction with chloroform:methanol (2:1) and repeated washes with 50% (v/v) acetone	Filtration	SEM	100	Mean dmax, aspect ratio (length/width), area, perimeter	One-way ANOVA
Catelas et al. [10]	2001	Papain, proteinase K	Multiple sequential WCS (6 steps)	Resin embedding and slicing	TEM	700–1300	Length, width	One-way ANOVA
Brown et al. [4]	2007	Papain, proteinase K, yeast lytic enzyme, Zymolase®	Multiple sequential WCS (12 steps)	Sequential filtration	SEM	150	dmax	One-way ANOVA
Billi et al.	2011	Proteinase K, 37°C	Density gradient centrifugation (1 step)	Silicon wafer or TEM grid	SEM or TEM	Minimum 1000	dmin, dmax, P, A, ECD, FL, FB, FF, AR, E, R, shape and chemical composition distribution	Nonparametric tests

* Particles isolated from tissue samples; WCS = washing/centrifugation/supernatant removal; TEM = transmission electron microscopy; SEM = scanning electron microscopy; d_min = minimum Feret’s diameter; d_max = maximum Feret’s diameter; P = perimeter; A = area; ECD = equivalent circle diameter; FL = fiber length; FB = fiber breadth; FF = form factor; AR = aspect ratio; E = elongation; R = roundness.