Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-014-3197-9
Knee
Changes in surface topography at the TKA backside articulation following in vivo service: a retrieval analysis Richard J. Holleyman · Susan C. Scholes · David Weir · Simon S. Jameson · Jim Holland · Tom J. Joyce · David J. Deehan
Received: 17 December 2013 / Accepted: 16 July 2014 © Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose With the advent of modular total knee arthroplasty (TKA) systems, backside wear at the articulation between the ultra-high-molecular-weight-polyethylene (UHMWPE) component undersurface and the tibial baseplate has received increasing attention as a source of clinically significant polyethylene wear debris. The aim of this study was to investigate the reciprocating interface at the TKA undersurface articulation using profilometry after in vivo service. Our null hypothesis was that there would be no discernible pattern or relationship between the metal tibial baseplate and UHMWPE surface profile. Methods A nanoscale analysis of thirty retrieved fixedbearing TKA explants was performed. Surface roughness (Sa) and skewness (Ssk) were measured on both the UHMWPE component undersurface and the tibial baseplate of explants using a non-contacting profilometer (1 nm resolution). Four pristine unimplanted components of two different designs (Stryker Kinemax and DePuy PFC) were examined for control purposes. Results Mean explant baseplate surface roughness was 1.24 μm (0.04–3.01 μm). Mean explant UHMWPE undersurface roughness was 1.16 μm (0.23–2.44 μm). Each explant had an individual roughness pattern with unique baseplate and undersurface UHMWPE surface roughness
R. J. Holleyman (*) · D. Weir · J. Holland · D. J. Deehan Newcastle Upon Tyne Hospitals Trust, Royal Victoria Infirmary & Freeman Hospital, Newcastle upon Tyne NE1 4LP, UK e-mail: [email protected] R. J. Holleyman · S. C. Scholes · T. J. Joyce · D. J. Deehan Newcastle University, Newcastle upon Tyne, UK S. S. Jameson University Hospital of North Durham, Durham, UK
that was different from, but closely related to, surface topography observed in control implants of the same manufacturer and design. Following in vivo service, UHMWPE undersurface showed changes towards a negative skewness, demonstrating that wear is occurring at the backside interface. Conclusion In vivo loading of the TKA prosthesis leads to measurable changes in surface profile at the backside articulation, which appear to be dependent on several factors including implant design and in vivo duration. These findings are consistent with wear occurring at this surface. Findings of this study would support the use of a polished tibial tray over an unpolished design in total knee arthroplasty with the goal of reducing PE wear by means of providing a smoother backside countersurface for the UHMWPE component. Keywords Profilometry · Surface properties · Backside wear · Undersurface articulation · Knee arthroplasty · Retrieval
Introduction Aseptic loosening remains the principal cause of mediumterm failure of total knee arthroplasty (TKA). With the advent of modular TKA systems, backside wear at the articulation between the polyethylene component undersurface and the tibial baseplate has received increasing attention as a source of clinically relevant polyethylene wear debris. This process is postulated to occur through micromotion between the captured fixed polyethylene component and the tibial baseplate consequent upon inexact locking [22]. Such debris may migrate, for example, directly through screw hole apertures and stimulate host
13
Knee Surg Sports Traumatol Arthrosc
osteoclastic-mediated bone resorption leading to aseptic loosening and implant failure [20]. Despite its prevalence, the fundamental mechanisms involved in wear at the backside articulation are not clear and previous work has focused primarily on design parameters of the implant such as the UHMWPE capture mechanism, fixed- versus mobile-bearing designs and implant material composition [2–4, 6, 9, 10, 15, 18, 19]. There are many designs of tibial baseplate and, indeed, some have polished or unpolished surfaces. Some are made from titanium and others from cobalt chromium (CoCr) or stainless steel alloys. Previous work on the femoral articulation has confirmed the importance of nanoscale abnormalities for clinical performance and also allowed for a glimpse into the mode of early wear through eburnation [11, 12]. Previous work has demonstrated increased UHMWPE wear associated with unpolished metal surfaces compared with polished surfaces when the small amplitude fretting conditions expected in tibial trays was applied [4]. There is an increasing awareness of the benefit of a highly polished tibial tray [4, 8, 15]. Profilometry is a validated and well-recognised investigative tool in the engineering field and has been gaining increasing coverage in its application to the study of orthopaedic implants [5, 13, 16, 17]. Whilst recent work has focused on surface topography at the femoral bearing, there is very little information explaining the profile of wear at the baseplate interface. We performed a retrospective nanoscale analysis of consecutive retrieved knee components so as to study the reciprocating interface at the undersurface articulation through profilometry following in vivo service. This technique has recently been validated for the femoral—polyethylene articulation [23]. Our null hypothesis was that there would be no discernible pattern or relationship between the metal and undersurface polyethylene surface profiles irrespective of Hood score (a semi-quantitive method of describing UHMWPE wear), patient characteristics or tibial tray material.
significant varus or valgus misalignment (
Knee
Changes in surface topography at the TKA backside articulation following in vivo service: a retrieval analysis Richard J. Holleyman · Susan C. Scholes · David Weir · Simon S. Jameson · Jim Holland · Tom J. Joyce · David J. Deehan
Received: 17 December 2013 / Accepted: 16 July 2014 © Springer-Verlag Berlin Heidelberg 2014
Abstract Purpose With the advent of modular total knee arthroplasty (TKA) systems, backside wear at the articulation between the ultra-high-molecular-weight-polyethylene (UHMWPE) component undersurface and the tibial baseplate has received increasing attention as a source of clinically significant polyethylene wear debris. The aim of this study was to investigate the reciprocating interface at the TKA undersurface articulation using profilometry after in vivo service. Our null hypothesis was that there would be no discernible pattern or relationship between the metal tibial baseplate and UHMWPE surface profile. Methods A nanoscale analysis of thirty retrieved fixedbearing TKA explants was performed. Surface roughness (Sa) and skewness (Ssk) were measured on both the UHMWPE component undersurface and the tibial baseplate of explants using a non-contacting profilometer (1 nm resolution). Four pristine unimplanted components of two different designs (Stryker Kinemax and DePuy PFC) were examined for control purposes. Results Mean explant baseplate surface roughness was 1.24 μm (0.04–3.01 μm). Mean explant UHMWPE undersurface roughness was 1.16 μm (0.23–2.44 μm). Each explant had an individual roughness pattern with unique baseplate and undersurface UHMWPE surface roughness
R. J. Holleyman (*) · D. Weir · J. Holland · D. J. Deehan Newcastle Upon Tyne Hospitals Trust, Royal Victoria Infirmary & Freeman Hospital, Newcastle upon Tyne NE1 4LP, UK e-mail: [email protected] R. J. Holleyman · S. C. Scholes · T. J. Joyce · D. J. Deehan Newcastle University, Newcastle upon Tyne, UK S. S. Jameson University Hospital of North Durham, Durham, UK
that was different from, but closely related to, surface topography observed in control implants of the same manufacturer and design. Following in vivo service, UHMWPE undersurface showed changes towards a negative skewness, demonstrating that wear is occurring at the backside interface. Conclusion In vivo loading of the TKA prosthesis leads to measurable changes in surface profile at the backside articulation, which appear to be dependent on several factors including implant design and in vivo duration. These findings are consistent with wear occurring at this surface. Findings of this study would support the use of a polished tibial tray over an unpolished design in total knee arthroplasty with the goal of reducing PE wear by means of providing a smoother backside countersurface for the UHMWPE component. Keywords Profilometry · Surface properties · Backside wear · Undersurface articulation · Knee arthroplasty · Retrieval
Introduction Aseptic loosening remains the principal cause of mediumterm failure of total knee arthroplasty (TKA). With the advent of modular TKA systems, backside wear at the articulation between the polyethylene component undersurface and the tibial baseplate has received increasing attention as a source of clinically relevant polyethylene wear debris. This process is postulated to occur through micromotion between the captured fixed polyethylene component and the tibial baseplate consequent upon inexact locking [22]. Such debris may migrate, for example, directly through screw hole apertures and stimulate host
13
Knee Surg Sports Traumatol Arthrosc
osteoclastic-mediated bone resorption leading to aseptic loosening and implant failure [20]. Despite its prevalence, the fundamental mechanisms involved in wear at the backside articulation are not clear and previous work has focused primarily on design parameters of the implant such as the UHMWPE capture mechanism, fixed- versus mobile-bearing designs and implant material composition [2–4, 6, 9, 10, 15, 18, 19]. There are many designs of tibial baseplate and, indeed, some have polished or unpolished surfaces. Some are made from titanium and others from cobalt chromium (CoCr) or stainless steel alloys. Previous work on the femoral articulation has confirmed the importance of nanoscale abnormalities for clinical performance and also allowed for a glimpse into the mode of early wear through eburnation [11, 12]. Previous work has demonstrated increased UHMWPE wear associated with unpolished metal surfaces compared with polished surfaces when the small amplitude fretting conditions expected in tibial trays was applied [4]. There is an increasing awareness of the benefit of a highly polished tibial tray [4, 8, 15]. Profilometry is a validated and well-recognised investigative tool in the engineering field and has been gaining increasing coverage in its application to the study of orthopaedic implants [5, 13, 16, 17]. Whilst recent work has focused on surface topography at the femoral bearing, there is very little information explaining the profile of wear at the baseplate interface. We performed a retrospective nanoscale analysis of consecutive retrieved knee components so as to study the reciprocating interface at the undersurface articulation through profilometry following in vivo service. This technique has recently been validated for the femoral—polyethylene articulation [23]. Our null hypothesis was that there would be no discernible pattern or relationship between the metal and undersurface polyethylene surface profiles irrespective of Hood score (a semi-quantitive method of describing UHMWPE wear), patient characteristics or tibial tray material.
significant varus or valgus misalignment (
