The early failure and revision of bimodular primary total hip arthroplasty prostheses requires the identification of the risk factors for material loss and wear at the taper junctions through taper wear analysis. Deviations in taper geometries between revised and pristine modular neck tapers were determined using high resolution tactile measurements. A new algorithm was developed and validated to allow the quantitative analysis of material loss, complementing the standard visual inspection currently used. The algorithm was applied to a sample of 27 retrievals (in situ from 2.9 to 38.1 months) of the withdrawn Rejuvenate modular prosthesis. The mean wear volumes on the flat distal neck piece taper was 3.35 mm. 3. (0.55 to 7.57), mainly occurring in a characteristic pattern in areas with high mechanical loading. Wear volume tended to increase with time to revision (r² = 0.423, p = 0.001). Implant and patient specific data (offset, stem size, patient’s mass, age and body mass index) did not correlate with the amount of material loss observed (p >  0.078). Bilaterally revised implants showed higher amounts of combined total material loss and similar wear patterns on both sides. The consistent wear pattern found in this study has not been reported previously, suggesting that the device design and materials are associated with the failure of this prosthesis. Cite this article: Bone Joint J 2015;97-B:1350–7

Aims. There are limited published data detailing the volumetric material loss from tapers of conventional metal-on-polyethylene (MoP) total hip arthroplasties (THAs). Our aim was to address this by comparing the taper wear rates measured in an explanted cohort of the widely used Exeter THA with those measured in a group of metal-on-metal (MoM) THAs. Patients and Methods. We examined an existing retrieval database to identify all Exeter V40 and Universal MoP THAs. Volumetric wear analysis of the taper surfaces was conducted using previously validated methodology. These values were compared with those obtained from a series of MoM THAs using non-parametric statistical methodology. A number of patient and device variables were accounted for using multiple regression modelling. Results. A total of 95 Exeter MoP and 249 MoM THAs were examined. The median volumetric loss from the MoM cohort was over four times larger than that from the MoP cohort (1.01 mm. 3. vs 0.23 mm. 3. , p < 0.001), despite a significantly shorter median period in vivo for the MoM group (48 months vs 90 months, p < 0.001). Multiple regression modelling indicated that the dominant variables leading to greater female taper material loss were bearing diameter (p < 0.001), larger female taper angles (p < 0.001), and male titanium stem tapers (p < 0.001). Conclusion. Consistent with the long-term clinical success of the device, the volumetric material loss from Exeter femoral head tapers was, in general, small compared with that from larger-diameter MoM head tapers. Cite this article: Bone Joint J 2018;100-B:1310–9

Introduction. Numerous studies have reported on clinically significant volumes of material loss and corrosion at the head-stem junction of metal-on-metal (MOM) hips; less is understood about metal-on-polyethylene (MOP) hips. We compared the effect of bearing type (MOM vs MOP) on taper material loss for a hip system of a single design (DePuy Pinnacle). Methods. We recruited retrieved MOM (n=30) and MOP (n=22) bearing hips that were consecutively received at our centre. We prospectively collected associated clinical and imaging data. We measured the severity of corrosion and volumes of material loss at each head taper surface and used multivariate statistical analysis to investigate differences between the two bearing types. Results. The median rate of material loss for the MOM and MOP groups was 0.81 mm. 3. /year (0.01–3.45) and 0.03 mm. 3. /year (0–1.07) respectively (p<0.001). 29 out of 30 MOM hips were revised for adverse metal reactions, compared with 1 out of 22 MOP hips. Discussion. MOP hips lost significantly less material from their taper junctions than MOM hips. We suggest that the metal-metal interaction at the bearing surface of MOM hips enhances the corrosive environment at the head-stem junction. Conclusion. Our results can reassure patients with MOP Pinnacle hips that they are unlikely to experience clinically significant problems related to material loss from the taper junction

Introduction. In this study, we aimed to investigate the effect of the topography of the female taper surface on taper wear. Patients/Materials & Methods. We measured volumetric material loss at the female taper surface of the first consecutive 36mm MoM hips received at our centre. The MoM hips were from a single manufacturer and possessed matching: head size (36mm); taper geometry (5.65 degree 12 14 tapers); and metallurgy (cobalt chrome female taper mated with a titanium stem). Volume loss was measured with a coordinate measuring machine using validated methods. Surface roughness was measured using a Surftest SJ400. There were 111 head tapers available for analysis. The majority had been revised secondary to ARMD, and a minority for loosening. The mean duration of implantation was 56 months. Volumetric wear values were log normalised in order to construct a multiple regression model to investigate the interaction of head offset, the head taper angle and the Rp value of the female taper surface. Rp is a roughness parameter, which is a measure of the peaks above the plateau of a surface. Results. The median (range) volumetric loss from the female taper surfaces was 0.132mm3 (0.008–2.149). Median Rp value was 1.94 microns (0.50 to 6.01). Multiple regression model returned an R2 value of 0.43 (p < 0.001) meaning that the Rp value of the female surface, the head offset, duration of implantation and the taper angle explained 43% of the variation in volumetric wear rates. Rp was the dominant variable. Discussion & Conclusion. The topography of the female taper surface appears to be an important factor in material loss from the taper junction in MoM hips. There was an unexpectedly wide variation in surface finishes in our sample set despite the fact that a single product from a single manufacturer was analysed

Introduction. Total hip replacement failure due to fretting-corrosion remains a clinical concern. We recently described that damage within CoCrMo femoral heads can occur either by mechanically-dominated fretting processes leading to imprinting (via rough trunnions) and surface fretting (via smooth trunnions), or by a chemically-dominated etching process along preferential corrosion sites, termed “column damage”. These corrosion sites occur due to banding of the alloy microstructure. Banding is likely caused during thermo-mechanical processing of the alloy and is characterized by local molybdenum depletion. It was the objective of this study to quantify material loss from femoral heads with severe corrosion, identify the underlying damage modes, and to correlate the damage to the alloy's microstructure. Methods. 105 femoral heads with a Goldberg score 4 were evaluated. Coordinate measuring machine data was used to compute material loss and visualize damage features. Time in situ and stem alloy were identified. Metallographic samples were produced for each case. Grain size and banding were identified using light-microscopy. Mann-Whitney tests were conducted to compare material loss between groups. Results. Heads exhibited imprinting and column damage in 72 and 51 cases, respectively, with an overlap of 36 cases. 18 heads exhibited surface fretting only. All heads with column damage exhibited a banded microstructure. Heads with column damage had higher material loss (p=0.05) than those without. Also, heads with a banded microstructure had higher material loss (p=0.035) than those with a homogenous microstructure. Grain size, carbide content, and time did not correlate with material loss. Conclusion. Column damage is a detrimental damage mode within CoCrMo femoral heads that is directly linked to banding within its microstructure. It appears that banding even affects material loss before column damage is identifiable. These results indicate that implant alloy microstructure must be optimized to minimize the release of fretting-corrosion products and related implant failure

Aims. We sought to determine whether cobalt-chromium alloy (CoCr) femoral stem tapers (trunnions) wear more than titanium (Ti) alloy stem tapers (trunnions) when used in a large diameter (LD) metal-on-metal (MoM) hip arthroplasty system. Patients and Methods. We performed explant analysis using validated methodology to determine the volumetric material loss at the taper surfaces of explanted LD CoCr MoM hip arthroplasties used with either a Ti alloy (n = 28) or CoCr femoral stem (n = 21). Only 12/14 taper constructs with a rough male taper surface and a nominal included angle close to 5.666° were included. Multiple regression modelling was undertaken using taper angle, taper roughness, bearing diameter (horizontal lever arm) as independent variables. Material loss was mapped using a coordinate measuring machine, profilometry and scanning electron microscopy. Results. After adjustment for other factors, CoCr stem tapers were found to have significantly greater volumetric material loss than the equivalent Ti stem tapers. Conclusion. When taper junction damage is identified during revision of a LD MoM hip, it should be suspected that a male taper composed of a standard CoCr alloy has sustained significant changes to the taper cone geometry which are likely to be more extensive than those affecting a Ti alloy stem. Cite this article: Bone Joint J 2017;99-B:1304–12

Objectives. The use of ceramic femoral heads in total hip arthroplasty (THA) has increased due to their proven low bearing wear characteristics. Ceramic femoral heads are also thought to reduce wear and corrosion at the head-stem junction with titanium (Ti) stems when compared with metal heads. We sought to evaluate taper damage of ceramic compared with metal heads when paired with cobalt chromium (CoCr) alloy stems in a single stem design. Methods. This retrieval study involved 48 total hip arthroplasties (THAs) with CoCr V40 trunnions paired with either CoCr (n = 21) or ceramic (n = 27) heads. The taper junction of all hips was evaluated for fretting/corrosion damage and volumetric material loss using a roundness-measuring machine. We used linear regression analysis to investigate taper damage differences after adjusting for potential confounding variables. Results. We measured median taper material loss rates of 0.210 mm. 3. /year (0.030 to 0.448) for the metal head group and 0.084 mm. 3. /year (0.059 to 0.108) for the ceramic group. The difference was not significant (p = 0.58). Moreover, no significant correlation between material loss and implant or patient factors (p > 0.05) was found. Conclusions. Metal heads did not increase taper damage on CoCr trunnions compared with ceramic heads from the same hip design. The amount of material released at the taper junctions was very low when compared with available data regarding CoCr/Ti coupling in metal-on-metal bearings. Cite this article: A. Di Laura, H. Hothi, J. Henckel, I. Swiatkowska, M. H. L. Liow, Y-M. Kwon, J. A. Skinner, A. J. Hart. Retrieval analysis of metal and ceramic femoral heads on a single CoCr stem design. Bone Joint Res 2017;6:–350. DOI: 10.1302/2046-3758.65.BJR-2016-0325.R1

Trunnionosis, due to mechanical wear and/or corrosion at the head stem taper junction, can occur in metal on polyethylene (MOP) hip implants. In some patients this results in severe soft tissue destruction or Adverse Reaction to Metal Debris (ARMD). The amount of material required to cause ARMD is unknown but analyses of retrieved hips may provide the answer to this clinically important question. We collected implants from 20 patients with failed hips with MOP bearings, revised due to ARMD. We collected clinical, imaging and blood test data. We graded the severity of taper corrosion (1 to 4), and quantified the volume of material loss from this junction. We compared our results with previous data collected for metal-on-metal (MOM) hips. The median time to revision of the MOP hips was 51.3 (23.1–56.4) months. All head tapers were moderately to severely corroded with a median corrosion score of 4. The median (range) of total material loss at the taper of the MOP hips was 3.9 mm. 3. (2.96 – 7.85 mm. 3. ) and the material loss rate was 1.4 mm. 3. / year (0.56 – 1.82). Comparison with MOM hips revealed no significant difference in taper material loss (p=0.7344) with a median rate of 0.81 mm. 3. / year (0.01–3.45). We are the first to quantify the volume of material loss at the head taper of hip implants with MOP bearings that were revised due to trunnionosis. This data indicates that a clinically significant dose of cobalt and chromium to induce ARMD is approximately 1.4 mm. 3. / year. We have identified a clinically significant volume of taper material loss in MOP hips

Using a femoral head from one manufacturer on the stem of another manufacturer poses the risk that the taper interface between the components do not contact correctly and the performance of the joint will be impaired. The cohorts in this study are a combination of modular Birmingham Hip Resurfacing (BHR) and Adept femoral heads on CPT stems. The study reviews the geometry of the taper interfaces to establish if the taper clearance angles was outside of the normal range for other taper interfaces. In addition the rates of material loss from the bearings and taper and a ranking of the stem damage were reviewed to determine if the levels of loss were above that seen for other similar joints. The material loss analysis demonstrated that the rates or levels of loss from the bearings, taper and stem are no different to levels published for manufacturer matched joints and in many cases are lower. The results demonstrate that the taper clearance angles for the mixed manufacturer joints (BHR-CPT: 0.067 to −0.116, Adept-CPT: 0.101 to −0.056) were within the range of other studies and manufacturer matched clearances (0.134 to −0.149). Using components from different manufacturers has not in this instance increased the level of material loss from the joints, when compared to other similar manufacturer matched joints

Taper corrosion in Total Hip Arthroplasty has surfaced as a clinically relevant problem and has recently also been reported for metal heads against polyethylene. Low neck stiffness is a critical contributing factor. Catastrophic taper failures have been reported for one particular stem design with a small V-40 taper made from a less stiff titanium-alloy. The purpose of this study was to identify factors involved in the failure process. 31 revised CoCr heads ranging from 32 to 44m diameter combined with TMZF-Titanium alloy stem with a V-40 taper (Accolade I) were analysed. Stems were only available for catastrophic failure cases with dis-association (n=8) or taper fracture (n=1). Clinical data were limited to time-in-situ, patient gender and age. Head material loss increased with time in situ (r²=0.49, p<0.001). Longer heads and material loss exceeding 15mm³ showed bottoming out and consecutive catastrophic stem taper failure. Heads with failed stem tapers were all 36mm diameter. The head starts rotating on the stem taper after bottoming out, causing major abrasive wear, ultimately resulting in catastrophic failure; it is surprising that these catastrophic cases did not exhibit clinical symptoms due to raised Co and Cr metal ions, which must have resulted from the large amount of CoCr lost from the female head taper. This would have attracted medical attention and prevented catastrophic failure by taper dis-association. Control exams of patients treated with the respective stem type in combination with large CoCr heads should include metal ion determination in blood or serum, even if no clinical symptoms are present, in order to detect taper corrosion before catastrophic failure occurs

Aims. Surgeons have commonly used modular femoral heads and stems from different manufacturers, although this is not recommended by orthopaedic companies due to the different manufacturing processes. We compared the rate of corrosion and rate of wear at the trunnion/head taper junction in two groups of retrieved hips; those with mixed manufacturers (MM) and those from the same manufacturer (SM). . Materials and Methods. We identified 151 retrieved hips with large-diameter cobalt-chromium heads; 51 of two designs that had been paired with stems from different manufacturers (MM) and 100 of seven designs paired with stems from the same manufacturer (SM). We determined the severity of corrosion with the Goldberg corrosion score and the volume of material loss at the head/stem junction. We used multivariable statistical analysis to determine if there was a significant difference between the two groups. . Results. We found no significant difference in the corrosion scores of the two groups. The median rate of material loss at the head/stem junction for the MM and SM groups were 0.39 mm. 3. /year (0.00 to 4.73) and 0.46 mm. 3. /year (0.00 to 6.71) respectively; this difference was not significant after controlling for confounding factors (p = 0.06). . Conclusion. The use of stems with heads of another manufacturer does not appear to affect the amount of metal lost from the surfaces between these two components at total hip arthroplasty. Other surgical, implant and patient factors should be considered when determining the mechanisms of failure of large diameter metal-on-metal hip arthroplasties. Cite this article: Bone Joint J 2016;98-B:917–24

Introduction. Modular-neck hips have twice the rate of revision compared to fixed stems. Metal related pathology is the second most common reason for revision of implants featuring titanium stems with cobalt chrome necks. We aimed to understand the in-vivo performance of current designs and explore the rationale for their continued use. Methods. This study involved the examination of 200 retrieved modular-neck hips grouped according to the material used for their neck and stem. Groups A, B and C had neck/stems featuring CoCr/beta Ti-alloy (TMZF), CoCr/Ti6Al4V-alloy, and Ti6Al4V/Ti6Al4V respectively. Reasons for revision included pain, elevated metal ion levels and fluid collection. The stem-neck interface was assessed for severity of fretting/corrosion using metrology methods to compute linear wear penetration rate. Results. All retrieved implants with a CoCr/Ti combination showed evidence of moderate-severe fretting corrosion at the neck-stem junction. Maximum penetration depth rate in group A (median of 17.9μm/year) was higher than that in group B (median=5.8μm/year); p=0.0012 and group C (median=1.55μm/year), p=0.0095. Implant failure occurred 2-fold earlier in modular-neck hips with TMZF-alloy stems than Ti6Al4V. There was a strong correlation between severity of damage and time to revision in the TMZF group A (p < 0.0001) and between taper damage and Co levels (p < 0.0001) and Cr levels (p < 0.0012). Patient and implant data did not correlate with the amount of material loss observed, (p>0.05). Discussion. The findings are in agreement with registry data as designs with CoCr/Ti at neck/stem interfaces had the highest levels of fretting and corrosion and lower threshold for revision. Conclusion. Corrosion of metal orthopaedic implants remains of clinical concern to patients, surgeons and industry. In light of the findings, the continued use of modular-neck with a metal mismatch at the neck/stem junction is unfavourable and should be avoided

Introduction. Dual-mobility bearings increase the stable range of motion of total hip arthroplasty (THA) but are limited by the mechanical effects of a large diameter metal on polyethylene bearing which may cause high rates of wear from the surfaces of the polyethylene bearing and the head-stem taper. Improved polyethylene (PE) has reduced concern over bearing wear but the effects on the taper junction are unknown. We aimed to better understand the effect of dual mobility bearings on fretting-corrosion damage to the taper junction by comparison to standard bearings. Materials and Methods. We collected and analysed retrieved hips of one design with either dual mobility (n= 39) or standard bearings (n=30). The bearing size in the dual mobility group was 42mm whereas in the standard bearing group it had a median of 36mm. Stem trunnions had V40 tapers. Time of implantation and body mass index were comparable between the two groups. Fretting and corrosion at the stem trunnions was quantified by: 1) visual scoring and 2) surface profilometry. Results. Corrosion and fretting of the head-stem taper junction was lower in the dual mobility group when compared to the standard group as measured by both visual scoring (p=0.0002) and surface profilometry to measure material loss (p<0.0001). We did not see black debris, characteristic of severe corrosion processes, at the male surfaces in the dual mobility group. Discussion. In this study, visual damage at the male taper surfaces of dual mobility systems was less that that occurring at the male taper surfaces of standard articulating systems, measurements of wear rates were in agreements with the macroscopic evaluation. Conclusions. The frictional torque on the head-stem taper junction may be reduced with the use of a dual-mobility system when compared to a standard bearing system

Aims

This study investigates head-neck taper corrosion with varying head size in a novel hip simulator instrumented to measure corrosion related electrical activity under torsional loads.

Aims

Acetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning.

Introduction. Historical studies have reported incidences of taper corrosion in retrieved MoP hips of 20–50%. These studies relied on visual assessments, rather than using modern analytical techniques. Patients/Materials and Methods. The Northern Retrieval Registry was initiated to routinely analyse all retrieved hips. The volumetric wear rates of retrieved Exeter head tapers were measured using a coordinate measuring machine using validated methods and compared to the available results obtained from an ongoing study of failed MoM prostheses. Power analysis suggested that we would need at least fifty Exeter head tapers to provide significant results. Non-parametric tests were used to assess differences. We have previously identified head diameter/offset/taper angle and taper surface roughness as variables associated with taper wear. The effect of bearing material combination remains unquantified. These design variables were entered into a multiple regression model following log normalisation of taper wear. Results. 56 consecutively retrieved Exeter head tapers underwent assessment. 36 were of size 28mm. Primary causes for revision were acetabular loosening/periprosthetic fractures. Mean duration in vivo was 87 (1 – 252) months. Median total volumetric wear was 0.29mm. 3. with a wear rate of 0.07mm. 3. /year. There were 353 MoMs. Median taper wear rates for 28mm MoM was 0.07, for 36mm was 0.11, for 38–44mm was 0.31, for 45 – 48mm was 0.52, for 49–52 was 0.55mm and for >52mm was 1.36mm. 3. /year. While Exeter taper wear was significantly lower than the MoM group as a whole (p<0.001), regression modelling indicated that bearing diameter had the greatest influence on taper wear. Discussion. Contrary to previous literature reports, significant material loss at the taper junction of conventional arthroplasties is not commonly observed. Exeter hips appear to be protected to some extent by the smaller head size and lower taper roughness when compared to contemporary MoM devices. The effect of the bearing combination remains under investigation

Aims

The optimum clearance between the bearing surfaces of hip arthroplasties is unknown. Theoretically, to minimize wear, it is understood that clearances must be low enough to maintain optimal contact pressure and fluid film lubrication, while being large enough to allow lubricant recovery and reduce contact patch size. This study aimed to identify the relationship between diametrical clearance and volumetric wear, through the analysis of retrieved components.

Objectives

Previous studies have suggested that metal-on-metal (MoM) Pinnacle (DePuy Synthes, Warsaw, Indiana) hip arthroplasties implanted after 2006 exhibit higher failure rates. This was attributed to the production of implants with reduced diametrical clearances between their bearing surfaces, which, it was speculated, were outside manufacturing tolerances. This study aimed to better understand the performance of Pinnacle Systems manufactured before and after this event.

Objectives

We investigated the reliability of the cobalt-chromium (CoCr) synovial joint fluid ratio (JFR) in identifying the presence of a severe aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) response and/or suboptimal taper performance (SOTP) following metal-on-metal (MoM) hip arthroplasty. We then examined the possibility that the CoCr JFR may influence the serum partitioning of Co and Cr.

Objectives

We have encountered patients who developed large joint fluid collections with massive elevations in chromium (Cr) and cobalt (Co) concentrations following metal-on-metal (MoM) hip arthroplasties. In some cases, retrieval analysis determined that these ion concentrations could not be explained simply by the wear rates of the components. We hypothesized that these effects may be associated with aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL).