Introduction:. Uncemented acetabular component fixation has been considered the most reliable fixation method in contemporary metal-on-metal hip resurfacing arthroplasty (HRA). During prospective long-term follow-up of a HRA device, we have encountered a surprisingly high incidence of this complication and wish to alert surgeons and manufacturers of this problem. Methods:. The study group was comprised of all 373 HRAs performed by a single surgeon using this hybrid hip resurfacing implant from May 2001 to March 2005. The acetabular component features a dual-coated bone ingrowth surface of plasma-sprayed titanium plus hydroxylappatite. There were a total of 34 revisions identified at the time of this study. Results:. There were 5 other cases (1.3%) of late acetabular loosening all occurring greater than 8 years postoperatively at an average of 9 ± 1 years after the primary surgery. All of theses patients were functioning well with radiographically stable implants for at least 8 years. Intraoperative findings included debonding of large portions of the porous coating which remained adhered to the underlying bone. We concluded that these cases represented primary mechanical implant failures. There was a moderate amount of wear debris, presumably from the backside. There was no bone loss evident. There were no soft tissue masses. There were also 2 cases of adverse wear failure with pain and soft tissue masses diagnosed preoperatively with well-fixed implants. One of these patients also suffered component debonding prior to revision. Two (2/5; 40%) cases had an acetabular inclination angle ≥50°. Implant
We identified an unusual pattern of backside deformation on polyethylene (PE) inserts of contemporary total knee replacements (TKRs). The PE backside's margins were inferiorly deformed in TKRs with NexGen central-locking trays. This backside deformation was significantly associated with tray debonding. Furthermore, recent studies have shown high rate of tray debonding in PS NexGen TKRs. Subsequently, a field safety notice was issued regarding the performance of this particular device combination and the Option tray has been withdrawn from use. Therefore, we hypothesised that the backside deformation of PS inserts may be greater than that of CR inserts. At our national implant retrieval centre, we used peer-reviewed techniques to analyse changes in the bearing wear rate and backside surface deformation of NexGen PE inserts using coordinate measuring machines [N=84 (CR-43 and PS-41) TKRs with non-augmented-trays]. Multiple regression was used to determine which variable had the greatest influence on backside deformation. The amount of cement cover on trays was quantified as a %of the total surface using Image-J software.Objectives
Design and Methods
One of the modern design total knee arthroplasty (TKA) system, the NexGen Legacy posterior-stabilized (LPS) Flex prosthesis, has been in use at our hospital since 2001. Between 2006 and 2011, NexGen LPS-Flex primary TKA were mainly performed in combination with a cemented short-keeled minimally invasive version tibial tray (MIS tibial component) instead of the traditional NexGen stemmed tibial tray. We observed some cases required early revision of isolated tibial component in primary TKA performed in this period. Therefore, our objectives were to report the series of this revision cases and to consider this failure mechanism. A total of 526 primary TKAs were performed using a NexGen LPS-Flex prosthesis and MIS tibial component during five-year period at our hospital. The mean age was 74 years at the time of the index procedure. We assessed revision rate of this tibial tray in this study and described clinical course of the revision cases. We also examined the clinical and radiographic features which could be associated with the failure.[Introduction]
[Patients & Methods]
Metal ion and particle release, particularly cobalt, has become an important subject in total hip arthroplasty, as it has shown to induce metal hypersensitivity, adverse local tissue reactions and systemic ion related diseases. The purpose of the following study was compare the ion release barrier function of a zirconium nitride (ZrN) multilayer coated hip stem for cemented use, designed for patients with metal ion hypersensitivity, against its uncoated version in a test configuration simulating the worst case scenario of a severely debonded hip stem. The ZrN multilayer coating is applied on a CoCrMo hip stem and consists of a thin adhesive chromium layer, five alternating intermediate layers out of chromium nitride (CrN) and chromium carbonitride (CrCN) and a final zirconium nitride (ZrN) shielding layer [1]. Hip stems with a ZrN multilayer coating (CoreHip AS, Aesculap AG, Germany) were tested in comparison with a cobalt-chrome uncoated version (CoreHip, Aesculap AG, Germany). In order to create a worst case scenario, the smallest stem size with the biggest offset in combination with an XL ceramic head (offset +7 mm) was used. The stems were embedded according to the ISO 7206-6 test in a bone cement sheet. Once the bone cement was bonded, the stem was pulled out and a PMMA grain was placed inside the femoral cavity in order to uprise the hip stem above its embedding line and simulate a debonded cemented hip stem with a severe toggling condition. The dynamic test was performed under bovine serum environment with an axial force of 3.875 kN [2] at 11.6 Hz for 15 million cycles. The test was interrupted after 1, 3, 5, 10 and 15 million cycles and the surfaces of the stems were analyzed through scanning electron microscopy (SEM) with energy dispersive X-Ray (EDX). Moreover, the test medium was analyzed for metal ion concentration (cobalt, chromium and molybdenum) using ICP-MS.Introduction
Methods
