Bio-tribo-corrosion resistant 3D Printed Composites for Load-bearing Implants

Among load-bearing implants, total hip arthroplasty (THA) is probably the most clinically
successful intervention. CoCrMo alloy, a wear resistant material of choice, is typically used in
femoral heads for THAs. In vivo life of THAs are often reduced due to debris generation, and Co
and Cr metal ion release from modular junctions. Management of taper corrosion from trunnions
of CoCrMo head and Ti6Al4V stems remain a serious challenge today. Taper corrosion
happens primarily due to mechanically assisted crevice corrosion (MACC) along with fretting
and galvanic corrosion, and leads to adverse local tissue reactions (ALTR), an immune-
mediated biological reaction due to elevated Co and Cr ions. ALTR has profound influence on
bone, leading to implant failure, which can result in early revision surgery. Co and Cr ions can
also cause other symptoms such as deafness, blindness, and interstitial cell damage resulting in
impaired renal functioning. Our application is focused on self-lubricating and self-healing
calcium phosphate (CaP) reinforced Ti- or CoCrMo-alloys to minimize bio-tribocorrosion in
applications such as trunnions in modular taper interlocks in THAs. CoCrMo-CaP composite will
be designed to minimize Co and Cr ion release compared to pure CoCrMo alloy; while Ti alloy-
CaP composites will be designed to completely eliminate the release of Co and Cr ions due to
corrosion or wear degradation.
The objective of this proposed research is to test our central hypothesis that CaP based solid
lubricants in Ti or CoCrMo alloys will form an in situ film at the contact surface to minimize bio-
tribo-corrosion and reduce metal ion release. The rationale is that once we understand the
mechanisms of tribofilm formation and its influence on bio-tribo-corrosion, we can design
implants with reduced metal ion release possibility in vivo. Our preliminary data show in situ
tribofilm formation with CaP reinforcement in Ti6Al4V or CoCrMo alloys during in vitro bio-tribo-
corrosion studies. Presence of tribofilm lowered wear induced damage and minimized metal ion
release in vitro. We have three Specific Aims for the proposed program – (1) to understand
tribocorrosion mechanism and tribofilm formation in CaP reinforced Ti-alloy matrix composites,
and measure their in vitro biological response; (2) to understand tribocorrosion mechanism and
tribofilm formation in CaP reinforced CoCrMo composites, and measure their in vitro biological
response, and (3) to measure in vivo biological properties of CaP added Ti or CoCrMo alloys.

Grant Number: 5R01AR078241-05
NIH Institute/Center: NIH
Principal Investigator: AMIT BANDYOPADHYAY