Polyethylene and metal debris generated by non-articulating surfaces of modular acetabular components

Abstract

We report a prospective study of the liner-metal interfaces of modular uncemented acetabular components as sources of debris. We collected the pseudomembrane from the screw-cup junction and the empty screw holes of the metal backing of 19 acetabula after an average implantation of 22 months. Associated osteolytic lesions were separately collected in two cases. The back surfaces of the liners and the screws were examined for damage, and some liners were scanned by electron microscopy. The tissues were studied histologically and by atomic absorption spectrophotometry to measure titanium content. The pseudomembrane from the screw-cup junction contained polyethylene debris in seven specimens and metal debris in ten. The material from empty screw holes was necrotic tissue or dense fibroconnective tissue with a proliferative histiocytic infiltrate and foreign-body giant-cell reaction. It contained polyethylene debris in 14 cases and metal in five. The two acetabular osteolytic lesions also showed a foreign-body giant-cell reaction to particulate debris. The average titanium levels in pseudomembranes from the screw-cup junction and the empty screw holes were 959 micrograms/g (48 to 11,900) and 74 micrograms/g (0.72 to 331) respectively. The tissue from the two lytic lesions showed average titanium levels of 139 and 147 micrograms/g respectively. The back surfaces of the PE liners showed surface deformation, burnishing, and embedded metal debris. All 30 retrieved screws demonstrated fretting at the base of the head and on the proximal shaft. Non-articular modular junctions create new interfaces for the generation of particulate debris, which may cause granulomatous reaction.

Survivorship of Monoblock Trabecular Metal Cups in Primary THA

“…holes allow backside debris to gain access to the boneimplant interface and accelerate periprosthetic osteolysis and loosening [6,11,12,19,23]. Younger age and initial diagnosis of osteonecrosis are known to adversely influence the long-term outcome of THA [2,3,10,27,33].…”

Effects of episodic subluxation events on third body ingress and embedment in the THA bearing surface

“…Third body particles are defined as debris originating other than from normal articulation between the femoral head and acetabular liner. Metallic debris predominates as third body particles, as demonstrated by a retrieval study of polyethylene liners involving quantification of embedded particles (Lundberg et al, 2007a); examples of metallic third body particles include porous ingrowth beads (Dowd et al, 2000;Najjar et al, 2000) or metal particles from the implants (Hirakawa et al, 2004;Huk et al, 1994;Kim et al, 2005;Lewis, 1997), from trochanteric reattachment fixation (Amstutz and Maki, 1978;Bronson, 1976;Hop et al, 1997), or from surgical instruments (Mackay et al, 2000). Third body particles can also originate from hydroxyapatite (Bauer et al, 1994;Bloebaum et al, 1997;Willie et al, 2000), bone (Que and Topoleski, 2000), or bone cement (Isaac et al, 1992;Joshi et al, 2001).…”

Backside Wear Is Not Dependent on the Acetabular Socket Design in Crosslinked Polyethylene Liners

“…Apart from the articular side, the interface between the liner and metal socket is also a potential source of polyethylene debris in modern modular acetabular implants [1,12,23,25,28,29,36,43,45]. Although articular-sided wear of polyethylene has been well documented and quantified [3,14,20,21,24,42,47], the role of backside wear in modern modular prostheses continues to be controversial because even less is known about backside wear with this newer material [1,12,25].…”

“…However, a cause-effect relationship has not been clearly established by these in vitro studies. A few retrieval studies [1,12,23,25,43,45] have also been performed involving direct visual/volumetric assessment of backside wear. However, gaps persist in our knowledge, and there are limited data regarding the in vivo backside wear characteristics of polyethylene liners (especially that of XLPE) and we have a limited understanding of what the important factors are that contribute to backside wear.…”