Table 5.

In vitro cell line biocompatibility studies

Study	Test material	Particle production	Assay	UHMWPE comparator?	Cell line	Outcomes	Relative reactivity
Morrison et al. [34]	PEEK	Chemical extraction	LDH activity GSH content MTT viability	Yes*	3T3 Mouse fibroblasts Rat osteoblasts	Osteoblast morphology remained unchanged after particle exposure for 48 hours; PEEK particles had no significant effect on GSH levels in fibroblasts, a slight decrease in osteoblast GSH levels, and no significant change to LDH activity in either cell line; PEEK exhibited a slight stimulatory effect on osteoblast protein content	–
Howling et al. [19]	CFR-PEEK	Multidirectional Pin-on-plate	ATP viability	No (latex)	L929 Mouse fibroblasts U937 Macrophage-like cells	No cell viability reduction caused by CFR-PEEK particles	–
Hallab et al. [17]	X-UHMWPE PEEK	Cryomilling/pulverization	Proliferation assay ATP viability LDH activity Cytokine analysis	Yes	Human (THP-1) macrophages/monocytes PBMNCs CD14+ monocytes	No significant effects on proliferation or viability between particle types; UHMWPE particles caused greater LDH activity compared with PEEK and X-UHMWPE. X-UHMWPE caused a significant increase in inflammatory cytokines relative to PEEK; the largest PEEK particles (approximately 13 μm) resulted in significant reduction of macrophage viability	(−)

* PE type not specified; PEEK = polyetheretherketone; PE = polyethylene; X-UHMWPE = crosslinked UHMWPE; ATP = adenosine triphosphate; MTT = MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide); PBMNC = peripheral blood mononuclear cells; LDH = lactate dehydrogenase; GSH = glutathione; (−) = decreased reactivity relative to comparator; – = similar reactivity to comparator.