Surface morphology and wear mechanisms of four clinically relevant biomaterials after hip simulator testing

Abstract

The surfaces of worn components hold clues to the underlying wear mechanisms. Previous evidence suggested that the absolute wear rates of acetabular components in a hip simulator were related to mechanical behavior; we hypothesized that the surface morphology of the liners might also be sensitive to mechanical properties. A noncontact, three-dimensional surface topography measurement system based on white light interferometry was used to quantify the surface morphology of ultra-high molecular weight polyethylene, polytetrafluoroethylene, high-density polyethylene, and polyacetal liners, and their corresponding femoral heads, after 3 million cycles in a multi-directional hip simulator. Comparisons were made with the fatigue soaked and control (as machined) components. Statistically significant power law relationships were observed between the arithmetic mean surface roughness (R(a)) of the worn acetabular liners and the volumetric wear rate in the hip simulator (p < 0.01, r(2) = 0.52). Significant relationships were also observed between R(a) and the elastic and large deformation mechanical behavior of the liner materials, measured directly from the wear-tested liners using the small punch test (p < 0.01, r(2) = 0.54-0.81). The results support the hypothesis that wear mechanisms of acetabular liners during hip simulator testing are related to surface morphology in conjunction with the mechanical behavior of the polymeric materials.

Retrieval analysis of motion preserving spinal devices and periprosthetic tissues

“…Furthermore, by quantitatively analyzing the surface data, the roughness and waviness can be quantified and compared with as-manufactured components, thereby providing insight into the magnitude of surface changes that occur in vivo. 8 – 10 Ultimately, quantitative measurements of implant surfaces are used to validate in vitro and computational models that seek to simulate in vivo wear processes.…”

Recent Developments in Cyclic Acetal Biomaterials for Tissue Engineering Applications

“…Macroporous EH scaffolds were prepared using a leachable porogen strategy. Briefly, macroporous networks were fabricated by incorporating a NaCl porogen (70,75, and 80 wt%) into the EHD monomer solution prior to cross-linking. EH networks were formed around the crystals by radical polymerization, and the porogen was removed by water leaching.…”

“…Polyacetals have also been used clinically in several orthopedic implants, most notably the Freeman all-polymer knee replacement and hip resurfacing prostheses (73,74). Current studies have discussed work on surface wear of hip joints and mechanical properties of these materials (73)(74)(75). A recent study published by Lee and Choi demonstrated that the properties of a porous polyacetal block were similar to that of bone (76).…”

Measurement outcomes from hip simulators

“…Alternative methods to measure wear directly were also developed including observing shape change through contact profilometry and using co-ordinate measuring machines (CMM) 5 and optical methods such as holography, white light interferometry and shadow graphs. 6–8 Osteolysis, the primary cause of revision in metal-on-polyethylene bearings, 9 was recognised to be caused by the cellular response to the polyethylene wear particles. 10 The size and volume of these polyethylene particles have more recently been shown to further influence cell behaviour 11 suggesting that while polyethylene wear rates indicated polyethylene loss, they do not necessarily fully predict clinical outcomes.…”