Background

The CoCrMo large bearings had shown a high failure rate, because of metal ion and particle release. Alumina matrix composite (AMC) ball heads have shown to mitigate such phenomena. The aim of this study was to investigate the leaching properties of AMC clinically as well as experimentally.

Introduction and Objective. Ceramic on Ceramic bearings in Total Hip Arthroplasty (THA) afford a low friction coefficient, low wear rates and extreme hardness. Significant complications include hip squeak, ceramic fracture and poor polyethylene performance in revision procedures due to imbedding of abrasive microscopic ceramic fragments. We report on the results of this bearing at a minimum of 10 years. Materials and Methods. A single-centre retrospective review of 449 THAs was performed. Primary outcome measures included aseptic revision and all-cause revision rates at a minimum of 10 years post operatively. Evaluation of functionality was performed with WOMAC and SF-36 scores which were performed pre-operatively and at intervals of 6 months, one year, 2 years, 5 years and 10 years post operatively. Results. There was a 6.2% (n=28) all-cause and 5.3% (n=24) aseptic revision rate for ceramic on ceramic total hip arthroplasty at minimum of 10 years with a mean time to revision 4.8 years (range 2 months − 11.6 years). Notably, there were 2 revisions for ceramic head fracture, one for ceramic liner fracture, 3 for aseptic loosening and 3 revisions for squeaking. Pain of unknown origin was the most common reason for revision. There was an improvement in postoperative WOMAC scores from a mean of 59.8 (range 15–95) pre-operatively to a mean of 15.6 (range 0–78) at 10 years. Conclusions. This study showed good functional outcomes but high revision rates for CoC THA at a minimum of 10 years. The role for CoC bearings in THA has been called into question in recent years and may continue to decline in popularity, even in younger patients. Further large scale studies are important to assess the long-term outcomes of this bearing surface

This was a retrospective study of registry data from a National Orthopaedic Hospital for all THRs with 10-year follow-up data. Inclusion criteria were all THRs with a minimum of 10-year follow-up data. All metal-on-metal (MoM) THRs and MoM resurfacings were excluded from the analysis due to the high rate of revision associated with these bearings. Univariate and multivariate analyses controlling for confounding variables were performed to compare outcomes. A total of 1,697 THRs were performed in 1,553 patients. The four significant predictors for revision were fixation type (p<0.01), surface bearing type (p<0.01), age (P<0.05) and head size (p<0.05). Gender, BMI and approach had no effect on revision rates. The lowest 10-year all-cause revision rates were seen in cemented THRs at 1.7%. Ceramic-on-poly bearings had the lowest revision rate at only 1.2%. Metal-on-poly bearings had a 1.7% revision rate. Ceramic on ceramic bearings had a 7.1% revision rate with 1 revision for squeak and 1 revision for ceramic head fracture. The causes for revision in order of decreasing frequency were as follows: Infection (n=13, 0.7%), dislocation (n=7, 0.4%), periprosthetic fracture (n=3, 0.2%) and aseptic loosening (n=2, 0.1%). There were 2 re-revisions at 10 years in total. The smaller 22.225mm head sizes had a significantly lower revision rate than other head sizes (p<0.05). Ceramic-on-poly bearings, cemented fixation and smaller head sizes perform better in the experience of this registry. However, with multivariate analysis, these differences were shown to be insignificant

Background. Many factors contribute to the occurrence of edge-loading conditions in hip replacement; soft tissue tension, surgical position, patient biomechanical variations and type of activities, hip design, etc. The aim of this study was to determine the effect of different levels of rotational and translational surgical positioning of hip replacement bearings on the occurrence and severity of edge-loading and the resultant wear rates. Method. The Leeds II Hip-Joint Simulator and 36mm diameter alumina matrix composite ceramic bearings (BIOLOX delta, DePuy Synthes, UK) were used in this study. Different levels of mismatch between the reconstructed rotational centres of the head and the cup were considered (2, 3 and 4mm) in the medial-lateral axis. Two cup inclination angles were investigated; an equivalent to 45 and 65 degrees in-vivo, thus six conditions (n=6 for each condition) were studied in total with three million cycles completed for each condition. The wear of the ceramic-on-ceramic bearings were determined using a microbalance (Mettler Toledo, XP205, UK) and the dynamic microseparation displacement was measured using a Liner Variable Differential Transformer. Results. When a translational joint centre mismatch was coupled with a higher cup inclination angle, the severity of edge-loading increased when compared with the effect of those variables applied individually. Increasing the medial-lateral joint centre mismatch from 2 to 3 to 4mm resulted in increased wear rates under both cup inclination angles, with the 65 degree cup inclination angle having significantly higher wear rate than the cup inclination angle of 45 degree (p=0.02, p=0.02, and p<0.01 respectively). Conclusion. The cups with a 45 degree inclination angle showed greater resistance to dynamic microseparation as a result of joint centre mismatch. This study demonstrated that optimal position should not only consider the rotational position of the acetabular cup but also the relative centres of rotation of the head and the cup. Disclosure. John Fisher is a paid consultant to DePuy Synthes. Jonathan Thompson and Graham H. Issac are employees at DePuy Synthes

Summary Statement. A new 28mm-diameter ceramic-on-ceramic (COC) acetabular bearing couple (Biomet Orthopedics) showed extremely low wear, even under adverse microseparation conditions∗. The wear results are similar or more favorable than those reported for clinical retrievals and wear testing of similar ceramic bearings. Introduction. A new acetabular shell and ceramic insert design (Biomet) incorporates features to help prevent malalignment during implantation, while still providing secure fixation within the acetabular shell. The incorporation of Biolox. ®. Delta (zirconia toughened alumina, CeramTec) material should provide improved wear resistance over pure alumina ceramics. The goal of this study is to evaluate the wear durability of this system for standard and microseparation testing. Materials & Methods. The 28 mm diameter ceramic heads and inserts (CeramTec) were seated on taper spigots and within acetabular shells (Biomet), respectively. Six sets of parts were tested for 5M cycles of standard hip wear testing (ISO 14242) and an additional six sets of parts for 2M cycles of microseparation testing. The microseparation testing protocol included a steep cup angle (60° in-vivo), side load, and reduced axial load to induce head-liner separation. The lateral displacement was increased from 0.5mm, to 1mm, and then to 2mm in order to replicate wear features observed in extreme situations of clinical retrievals. [1]. The parts were weighed (gravimetric wear rates) and photographed throughout the test. SEM, transformation, and wear debris analyses were completed. Results. The steady-state wear rate throughout standard testing was 0.0094 +/− 0.0029 mm. 3. /10. 6. cycles (+/-95% CI). The initial 0.5mm microseparation distance (0–1M cycles) showed no signs of wear. Most heads showed wear stripes after increasing to 1.0mm (1–1.5M cycles), and then all test parts showed stripes after increasing to 2mm. The increased visibility in wear stripes correlated with an increased level of measured wear. For the 2mm separation-distance testing interval, the wear rate was 0.178 +/− 0.052mm. 3. /10. 6. cycles. Discussion/Conclusion. The lack of wear stripes during 0.5mm of microseparation is an indication of the strength of the implants. A distance of 1–2mm is an extreme level of microseparation and the 60° in-vivo cup inclination created an even worse-case situation for wear; however, the implants showed excellent mechanical strength and low wear rates. SEM and transformation analyses showed minimal wear and evidence of stress-induced ceramic toughening. Microseparation testing at another lab . [2]. has shown a similarly low wear rate (0.5 mm. 3. /10. 6. cycles) for Biolox. ®. Delta ceramic, with Biolox. ®. Forte (alumina ceramic, without zirconia) showing a considerably higher wear rate (6.3mm. 3. /10. 6. cycles). The standard testing wear rate (0.0094+/-0.0029 mm. 3. /10. 6. cycles) was much lower than the average wear rate (0.69+/-0.63 mm. 3. /10. 6. cycles) of several COC implant retrievals by Walter . [1]. The 28mm steady-state wear rate of this test is better than or equal to the wear rate (0.0101 mm. 3. /10. 6. cycles) observed in other 28mm COC systems.∗∗. ∗Ceramic-on-Ceramic articulation is not cleared for use in the United States. ∗∗Laboratory results are not necessarily indicative of clinical performance

Background. As the number of ceramic THR bearings used worldwide is increasing, the number of implants that experience off-normal working conditions, e.g. edge loading, third bodies in the joint, soft tissues laxity, dislocation/subluxation of the joint, increases too. Under all such conditions the bearing surfaces can be damaged, leading eventually to a limitation of the expected performances of the implant. Methods. We characterised the damage resistance of different bearing surfaces (alumina matrix composite BIOLOXdelta, alpha-alumina BIOLOXforte, zirconia 3Y-TZP, oxidized zirconium alloy Zr-2.5Nb, CoCr-alloy) by scratch tests performed following the European standard EN 1071–3:2005. Also the scratch hardness of same materials has been assessed. Results. The Lc1 value (i.e., the load for the onset of a scratch) measured for BIOLOXdelta is about fivefold the one measured for the oxidized zirconium alloy (OXZr) surface and about tenfold the Lc1 measured for the CoCr alloy. The height of ridges along the scratch edges due to plastic flow in the composite ceramic BIOLOXdelta are only 21% in height than in CoCr, and only a small fraction (0.04%) of the height of ridges measured on OXZr surfaces. The scratch hardness of the metal samples tested (CoCr, OXZr) results one order of magnitude lower than the ones of ceramics. This behavior is not influenced by of the presence of the coating on OXZr surface. Conclusions. The transformation toughened ceramics tested (BIOLOXdelta, 3Y-TZP) are the materials that exhibit the higher resistance to scratching. Ridges at scratch edges are lower in ceramics than in coated or uncoated metals. The result show the superior scratch resistance behavior of toughened ceramics for THR wear couples with respect to coated or bare alloys. Level of Evidence. Level 1

Objectives

Our study aimed to examine not only the incidence but also the impact of noise from two types of total hip replacement articulations: ceramic-on-ceramic and ceramic-on-polyethylene.