Neck Taper Research Articles

How Does the Micro-Groove Profile Influence the Mechanics of Taper Junction in Hip Implants? A Finite Element Study

This study aims to investigate the effect of ridged (micro-grooved) surface finish over the trunnion surface on the mechanics (stress, strain, and deformation) of the head–neck taper interface in hip implants. Using finite element modelling, the study focused on the geometric parameters of such micro-grooves to study how they would mechanically affect stress and deformation fields after the assembly procedure. As such, five different 2D models with varying micro-groove height and spacing were produced and assembled under an impaction assembly force of 4 kN in a 32 mm CoCrMo head engaged with a 12/14 Ti-6Al-4V neck. The results showed that lower von Mises stresses could be induced by either an increase or decrease in spacing against the base model (Model 1), which probably signifies that the relationship between the ridge spacing and stress may depend on the level of spacing. It was concluded that the geometrical parameters of the ridges (and their non-linear interactions) impact not only the stress and strain fields but also the assembly loading time at which the maximal stress and plastic deformation occur.

Usefulness of modular neck adapter in partial hip revision.

Modular neck adapters allow different length and offset changes to reach a stable total hip arthroplasty (THA) and permit a quick partial hip revision procedure without removing the existing components. The literature is poor on this matter and about the long-term related outcomes. This narrative review summarizes the most recent literature about these devices as an option of surgical treatment in partial total hip arthroplasty revision (THAr) focusing on indications, clinical and radiological outcomes, and related complications. The narrative review of the current available literature was conducted in December 2022 through electronic database. The terms used were: "Head neck taper" OR "Merete BioBall" AND "revision Total Hip Arthroplasty (MeSH Terms)". The timeframe was limited between 01/01/2000 and 01/12/2022. The studies regarding the clinical use of the Merete BioBall® system in hip revision surgery were included, while all the papers concerning modular stem prosthesis were excluded. The surgical procedure is safe, quick and allows the surgeon to correct a well-fixed stem version, length and offset, besides retensioning soft tissues. Clinical and radiological outcomes are good with low complications rates. The modular neck adapter system seems to be a good surgical procedure for recurrent dislocation of THA, especially in case of a second THAr surgery. However, the main indication of adapter use remains the isolated acetabular cup revision. The related complications are rare: the worst is the re-dislocation due to an insufficient stem version and length correction. Re-dislocation rates reported in literature vary from 5.2% to 15%. Corrosion or fretting of the modular system are not reported in literature.

DAMAGE ANALYSIS OF RETRIEVED BIOLOX DELTA CERAMIC COMPONENTS FROM TOTAL HIP ARTHROPLASTIES

In 2020 almost 90% of femoral heads for total hip implants in Germany were made of ceramic. Nevertheless, the cellular interactions and abrasion mechanisms in vivo have not been fully understood until now. Metal transfer from the head-neck taper connection, occurring as smear or large-area deposit, negatively influences the surface quality of the articulating bearing. In order to prevent metal transfer, damage patterns of 40 Biolox delta ceramic retrievals with CoC and CoPE bearings were analysed.A classification of damage type and severity for each component (n=40) was done according to an established scoring system. To investigate the physical properties, the surface quality was measured using confocal microscopy, quantitative analysis of phase composition were performed by Raman spectroscopy and qualitative analysis of metal traces was done by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX). The periprosthetic tissue was analysed for abrasion particles with SEM and EDX.Both bearing types show different damage patterns. Dotted/ drizzled metal smears were identified in 82 % of CoC (n=16) and 96 % of CoPE (n=24) bearings. Most traces on the ceramic heads were identified in the proximal area while they were observed predominantly in the distal area for the ceramic inlays. The identified marks are similar to those of metallic bearings. Metallic smears lead to an increase of up to 30 % in the monoclinic crystalline phase of the ceramic. The roughness increases by up to six times to Ra=48 nm. Ceramic and metallic wear particles from the articulating surfaces or head neck taper junctions were found in the periprosthetic tissue.Damage patterns on CoC hip implants seem to be similar to those of metallic implants. More detailed analysis of CoC implants are needed to understand the described damage patterns and provide advice for prevention.

Insights into Imprinting: How Is the Phenomenon of Tribocorrosion at Head-Neck Taper Interfaces Related to Corrosion, Fretting, and Implant Design Parameters?

Wear and corrosion at modular neck tapers in THA can lead to major clinical implications such as periprosthetic osteolysis, adverse local tissue reactions, or implant failure. The material degradation processes at the taper interface are complex and involve fretting corrosion, third-body abrasion, as well as electrochemical and crevice corrosion. One phenomenon in this context is imprinting of the head taper, where the initially smooth surface develops a topography that reflects the rougher neck taper profile. The formation mechanism of this specific phenomenon, and its relation to other observed damage features, is unclear. An analysis of retrieved implants may offer some insights into this process. (1) Is imprinting related to time in situ of the implants and to the taper damage modes of corrosion and fretting? (2) Are implant design parameters like neck taper profile, stem material, or head seating associated with the formation of imprinting? (3) Is imprinting created by an impression of the neck taper profile or can a different mechanistic explanation for imprinting be derived? Thirty-one THAs with cobalt-chromium-molybdenum-alloy (CoCrMo) heads retrieved between 2013 and 2019 at revision surgery from an institutional registry were investigated. Inclusion criteria were: 12/14 tapers, a head size of 36 mm or smaller, time in situ more than 1 year, and intact nonmodular stems without sleeve adaptors. After grouping the residual THAs according to stem type, stem material, and manufacturer, all groups of three or more were included. Of the resulting subset of 31 retrievals, nine THAs exhibited a still assembled head-neck taper connection. The median (range) time in situ was 5 years (1 to 23). Two stem materials (21 titanium-alloy and 10 stainless steel), three kinds of bearing couples (11 metal-on-metal, 13 metal-on-polyethylene, and seven dual-mobility heads), and two different neck taper profiles (six wavy profile and 25 fluted profile) were present in the collection. Four THAs exhibited signs of eccentric head seating. The 31 investigated THAs represented 21% of the retrieved THAs with a CoCrMo alloy head during the specified period.At the head tapers, the damage modes of corrosion, fretting, and imprinting were semiquantitatively rated on a scale between 0 (no corrosion/fretting/imprinting) and 3 (severe corrosion/fretting/imprinting). Corrosion and fretting were assessed applying the Goldberg score, with the modification that the scale started at 0 and not at 1. Imprinting was assessed with a custom scoring system. Rating was done individually at the proximal and distal head taper half and summed to one total damage score for each retrieval and damage mode. Correlations between the damage modes and time in situ and between the damage modes among each other, were assessed using the Spearman rank order correlation coefficient (ρ). Associations between imprinting and implant design parameters were investigated by comparing the total imprinting score distributions with the Mann-Whitney U-test. Metallographically prepared cross-sections of assembled head-neck taper connections were examined by optical microscopy and disassembled head and neck taper surfaces were assessed by scanning electron microscopy (SEM). The imprinting damage score increased with time in-situ (ρ = 0.72; p < 0.001) and the corrosion damage score (ρ = 0.63; p < 0.001) but not with the fretting damage score (ρ = 0.35; p = 0.05). There was no difference in total imprinting score comparing neck taper profiles or stem materials, with the numbers available. Eccentric head seating had elevated total imprinting score (median 6 [interquartile range 0]) compared with centric seating (median 1 [2]; p = 0.001). Light optical investigations showed that imprinting can be present on the head taper surfaces even if the depth of abraded material exceeds the neck taper profile height. SEM investigations showed bands of pitting corrosion in the imprinted grooves. The microscopic investigations suggest that imprinting is not an independent phenomenon but a process that accompanies the continuous material degradation of the head taper surface because of circular damage on the passive layer induced by grooved neck tapers. Material loss from head-neck taper connections involving CoCrMo alloy heads is a source of metal ions and could potentially be reduced if hip stems with smooth neck tapers were used. Surgeons should pay attention to the exact centric seating of the femoral head onto the stem taper during joining of the parts.

Effect of abutment neck taper and cement types on the amount of remnant cement in cement-retained implant restorations: an in vitro study.

PURPOSEThe present study aims to analyze the effect of abutment neck taper and types of cement on the amount of undetected remnant cement of cement-retained implant prostheses.MATERIALS AND METHODSThree neck taper angles (53°, 65°, 77°) and three types of cement (RMGI: resin-modified glass ionomer, ZPC: zinc phosphate cement, ZOE: zinc oxide eugenol cement) were used. For each group, the surface percentage was measured using digital image and graphic editing software. The weight of before and after removing remnant cement from the abutment-crown assembly was measured using an electronic scale. Two-way ANOVA and Duncan & Scheffe’s test were used to compare the calculated surface percentage and weight of remnant cement (α = .05).RESULTSThere were significant differences in remnant cement surface percentage and weight according to neck taper angles (P < .05). However, there were no significant differences in remnant cement surface percentage and weight on types of cement. No interaction was found between neck taper angles and types of luting cement (P > .05). The wide abutment with a small neck taper angle showed the most significant amount of remnant cement. And the types of luting cement did not influence the amount of residual cement.CONCLUSIONTo remove excess cement better, the emergence profile of the crown should be straight to the neck taper of the abutment in cement-retained implant restoration.

Wear estimation of trapezoidal and circular shaped hip implants along with varying taper trunnion radiuses using finite element method

Background and objectiveThe hip joint is the vital joint that is responsible for the bodyweight transfer from the upper body to the lower body. Due to age these joints are worn out and need to be replaced by artificial hip implants. Wear is the predominant factor that is responsible for the loosening of hip implants. The wear occurs between the joints due to various reasons. The wear estimation at the design stage gives a clear idea about the life of the implants and also minor changes in the design may also significantly increase the life expectancy of the implant which can further reduce the rate of revision surgery. The linear wear rate is estimated in the taper trunnion surface. MethodsIn this study, the circular and trapezoidal-shaped stem implant is designed, and wear studies are performed at the trunnion junction. The femoral head of size 28 mm, acetabular cup thickness of 4 mm, and a backing cup of thickness 2 mm are considered for the study. The neck taper radiuses at the top surface are altered. Ansys is used to perform the simulations. ResultsAt the time of assembly of the femoral head into the stem, the stresses were found to be increasing with an increase in the top surface radius of the neck taper junctions. However, when the walking conditions are considered for wear estimation of implants the circular implants with the 12/14 mm taper exhibited the lesser linear wear rate of 0.003 mm/year. The trapezoidal implants with the 10/14 mm taper exhibited a lesser linear wear rate of 0.032 mm/year. ConclusionsWear is an important parameter that leads to the revision of implants due to loosening. It is found that with the decrease in the taper radius at the top surface against the standard 12/14 mm taper there is no significant decrease in the wear rate at the taper junction. Overall the circular implants exhibited less wear rate results over the trapezoidal-shaped stem implants. Due to the less linear wear rate, the circular implant has a higher life over the trapezoidal-shaped implant. Further, these implants can be manufactured to test using a hip simulator with the same conditions to validate the obtained results.

What the Surgeon Can Do to Reduce the Risk of Trunnionosis in Hip Arthroplasty: Recommendations from the Literature.

Trunnionosis, defined as wear and corrosion at the head–neck taper connection, is a cause of failure in hip arthroplasty. Trunnionosis is linked to a synergistic combination of factors related to the prosthesis, the patient, and the surgeon. This review presents analytical models that allow for the quantification of the impact of these factors, with the aim of providing practical recommendations to help surgeons minimize the occurrence of this failure mode. A tighter fit reduces micromotion and, consequently, fretting of the taper connection. The paramount parameters controlling the fixation force are the coefficient of friction and the impaction force. The influence of the head diameter, as well as of the diameter and angle of the taper, is comparatively small, but varus alignment of the taper and heads with longer necks are unfavourable under physiologic loads. The trunnion should be rinsed, cleaned, and dried carefully, while avoiding any contamination of the bore—the female counterpart within the head—prior to assembly. Biological debris, and even residual water, might critically reduce the fixation of the taper connection between the head and the neck. The impaction force applied to the components should correspond to at least two strong blows with a 500 g hammer, striking the head with an ad hoc impactor aligned with the axis of the taper. These strong blows should correspond to a minimum impaction force of 4000 N.

Sensing Localized Surface Corrosion Damage of CoCrMo Alloys and Modular Tapers of Total Hip Retrievals Using Nearfield Electrochemical Impedance Spectroscopy.

Wear and corrosion damage of biomedical alloys alters the structure and electrochemical properties of the surface heterogeneously. It was hypothesized that local regions on the same surface systematically differ from one another in terms of their impedance characteristics. To test this hypothesis, CoCrMo disks exposed to electrosurgical and inflammatory-species-driven damage were characterized using a localized impedance technique, nearfield electrochemical impedance spectroscopy (NEIS), to assess point-specific surface integrity in response to applied damage. It was found that electrosurgical damage, as may arise during primary arthroplasty and revision surgeries, and hydrogen peroxide concentrations of 5-10 mM significantly alter the corrosion susceptibility of the local surface compared to the as-polished CoCrMo surface. A CoCrMo retrieved neck taper (Goldberg score of 4) was scored in different local regions on the basis of visual appearance, and it was found that there is a direct relationship between increasing debris coverage and decreasing impedance, with the global surface impedance closest to the most severely scored local region. This noninvasive method, which uses a millielectrode configuration to test localized regions, can measure the heterogeneous electrochemical impedance of an implant surface and be tailored to assess specific damage and corrosion mechanisms revealed on retrieval surfaces.

Five-year results of endovascular abdominal aortic aneurysm repair with the Ovation abdominal stent graft

ObjectiveEndovascular abdominal aortic aneurysm repair (EVAR) has been rigorously compared with open repair for the treatment of abdominal aortic aneurysms in randomized trials and observational studies, but a comparison of individual devices is lacking, and single-device registries and trials are limited by small sample size. Here we report a descriptive analysis of the Effectiveness of Custom Seal with Ovation: Review of the Evidence (ENCORE) database, pooled results of multiple studies evaluating the midterm results of EVAR with the Ovation Abdominal Stent Graft Platform. MethodsThis is a retrospective analysis of the ENCORE database, a cohort of patients undergoing EVAR with the Ovation platform composed of pooled, prospectively collected data from 1296 patients from five clinical trials and the prospectively maintained European Union Post-Market Registry. The primary outcomes were 5-year rates of type IA and type I or III endoleak. Secondary outcomes included were 30-day mortality, 30-day major adverse event, technical success (successful deployment of the aortic body and iliac limbs), as well as 5-year survival, and freedom from aneurysm-related mortality, type II endoleak, device-related intervention, aneurysm rupture, sac expansion, and conversion to open repair. ResultsA total of 1296 patients were included in the analysis. The average age was 73 ± 8 years and 81% of patients were male. Fifty percent of patients had complex aortic anatomy, (neck length <10 mm, neck diameter >28 mm, neck angle >60°, reverse neck taper >10%, distal common iliac artery diameter <10 mm, or external iliac artery diameter <6 mm). Technical success was 99.7%. Thirty-day mortality was 0.3%, 30-day rate of major adverse event was 1.6%, and polymer leak rate was 0.2%. Freedom from type IA endoleak at 1, 3, and 5 years was 97.6%, 97.1%, and 95.8%, respectively; type I or III endoleak at 1, 3, and 5 years was 96.9%, 95.7%, and 94.0%, respectively. Freedom from device-related reintervention at 1, 3, and 5 years was 96.2%, 94.4%, and 92.4% and primary freedom from sac expansion was 97.0% at 1 year, 90.3% at 3 years, and 84.9% at 5 years. Freedom from all-cause mortality and aneurysm-related mortality at 5 years were 78.9% and 99.3%, respectively. ConclusionsThis analysis of the ENCORE database demonstrates that EVAR with the Ovation platform has favorable midterm durability evidenced by successful aneurysm exclusion and 5-year freedom from aneurysm-related mortality.

An alternative solution to the problem of “cold welding” the adapter of the modular head with the cone of the stably osseointegrated femoral component of the M2a-Magnum implant, when choosing the volume of revision endoprosthetics

The main advantages of the М2а-Magnum modular system pair are the presence of a group of metals metal with wear of the large head, which is the maximum value that makes it possible to increase the range of motion in the hip joint by more than 160 with virtually no risk of dislocation [1]. This allows you to freely conduct active work and sports. However, the system is not without drawbacks. First of all, this is the unrevealed danger of damage to metal ions in the blood, as well as the problem of the development of a pseudotumor lymphoid reaction [2,3], leading to extensive osteolysis, an increased risk of periprosthetic fractures, and, accordingly, an increase in the frequency of endoprosthesis destabilization. Currently, the use of constructions is practically suspended, but there are more than 1 million patients in the world [4] with implanted large "metals - metal pairs". In revision surgery with M2a-Magnum implants, the main problem is often the inability to remove the femoral head adapter component from the neck taper. fretting corrosion is observed, leading to the effect of cold welding. The latter is typical for the connection of titanium surfaces (adapter of the head module and the neck of the femoral component). It turns out that it should be noted that the M2a-38 system does not have a titanium adapter made of a cobalt-chromium alloy and devoid of this problem [4].

Advance of head taper corrosion after metal on polyethylene total hip arthroplasty

Total hip arthroplasty is currently an important surgical method for the treatment of hip diseases. The modular design of the head and neck taper facilitates the adjustment of limb length and femoral offset during surgery, however, complications such as wear, corrosion and looseness of the modular interface are also inevitable old problems. In recent years, with the changes in the design of prostheses, the trend that patients becomes younger and active, and the development of minimally invasive surgery, taper corrosion has again become a problem that needs to be solved and cannot be ignored, which is causing the attention of joint surgeons. There have been many studies on the complications associated with metal-on-metal prosthesis modular interfaces, such as increased metal ion level, taper corrosion and adverse local tissue reactions, while there are few studies on the complications of metal-on-polyethylene total hip arthroplasty, and metal-on-polyethylene prosthesis has similar problems such as increased local metal ion level and adverse tissue reactions caused by taper corrosion, which may also lead to complications such as prosthesis loosening, dislocation and fracture. Currently there are few reports about head and neck taper corrosion of metal-on-polyethylene prosthesis in China and there are still controversies about its manifestation and mechanism. In this paper, we summarized the above problems through literature reviewto expound the concept, research history, assessment methods, and incidence of metal-on-polyethylene prosthesistaper corrosion and the effect of material composition, diameter of the metal head, neck length, femoral offset, geometry of the taper, surgical factors, in vivo time, and patient factors on taper corrosion are analyzed. In summary, there are still many problems in the researches about the specific forming mechanism that have not been solved, thus it is very important for the prevention of taper corrosion: choosing the same material or ceramic material, avoiding overlarge diameter of the femoral head and femoral offset, avoiding too small taper degree, paying attention to the strength of tapping and cleaning of the taper are the current viable options.

Modelling and analysis of tool deflections in tailored micro end mills

The deflection of micro end mills has a detrimental effect on surface quality of the machined micro components and adversely affects the achievable dimensional and geometrical tolerances. In this paper, the analysis and modelling of tool deflections of tailored micro end mills have been considered. The tool deflections are obtained using analytical models as well as finite element simulations and verified using a dedicated measurement setup, which uses a capacitive sensor with a nanometre resolution for static tool deflection measurements. The optimisation of the micro end mill geometry has been performed to determine optimum neck taper angle and transition radius of the single edge micro end mill to have minimum tool deflections. With the developed model, tool failure predictions for a given process parameter set can be performed and it can be used for better micro milling process planning.

Modelling and analysis of tool deflections in tailored micro end mills

The deflection of micro end mills has a detrimental effect on surface quality of the machined micro components and adversely affects the achievable dimensional and geometrical tolerances. In this paper, the analysis and modelling of tool deflections of tailored micro end mills have been considered. The tool deflections are obtained using analytical models as well as finite element simulations and verified using a dedicated measurement setup, which uses a capacitive sensor with a nanometre resolution for static tool deflection measurements. The optimisation of the micro end mill geometry has been performed to determine optimum neck taper angle and transition radius of the single edge micro end mill to have minimum tool deflections. With the developed model, tool failure predictions for a given process parameter set can be performed and it can be used for better micro milling process planning.

Dual-taper modular hip implant: Investigation of 3-dimensional surface scans for component contact, shape, and fit.

BackgroundThe etiology of wear particle generation and subsequent corrosion in modular total hip arthroplasty implants likely begins with mechanical fretting. The purpose of this study was to determine geometric features of the male and female taper surfaces that drive stability within the neck-stem junction.MethodsEighteen modular hip components received 3-dimensional surface scans to examine the neck-stem taper junction using an optical scanner. The normal distance between the surfaces of the neck taper as seated in the stem slot was measured and produced a color map of the contact proximity. Contour plots identified surface shape variation and contact. Angle measurements and neck seated depth were analyzed by regression.ResultsThe typical features observed were (1) a vertical line of contact at one end of the transition from the flat surface to the radius surface; (2) a vertical line of contact in the radius surface just past the centerline; (3) a concavity along the flat surface between the neck and stem components; and (4) one of the neck flat surfaces was closer to its mating surface on the stem. The seated depth of the neck was dependent on the taper angles in the flat section of the neck (R2 = 0.5000, P = .0332).ConclusionsThe shape of the neck and stem tapers deviate from ideal design dimensions, contributing to relative motions between the neck and stem. While these processes are not proven to directly cause implant failure, they may place the implants at higher risk for failure.

The effect of altering head length on corrosion using a material loss method.

Corrosion at head neck taper junctions in total hip arthroplasty has increasingly been reported in the literature. Debate persists as to the exact causes and clinical significance of corrosion. Increased offset and head length has been correlated with an increased risk of tribocorrosion due to an adverse mechanical environment. The purpose of this study is to assess the effect of head length on corrosion of a metal-on-polyethylene articulation. Retrievals from a single institution of 28-mm cobalt chromium alloy heads with a 12/14 taper from a single manufacturer were studied. Corrosion of femoral head bores were studied utilising a material loss method. Testing was performed using co-ordinate measuring for maximum linear wear depth. 56 heads were examined with lengths of either -3, 0, +4 or +8 mm and all had been in situ for a minimum of 2 years. There were no significant differences in mean maximum linear wear depth (MLWD) (p = 0.6545). There was no correlation found between MLWD and the time implants were in situ (Spearman coefficient -0.1157) and no significant difference seen between high or standard offset stems (p = 0.1336). In contrast to studies using qualitative methodologies, there was no correlation between head length and material loss when confined to a 28-mm head. Broad application of this outcome should be cautioned against as this study examined 1 taper construct and a metal-on-polyethylene articulation.

Biomaterials for hip implants – important considerations relating to the choice of materials

Abstract This article is a review of important material requirements for hip biomaterials including their response to the body environment (biocompatibility), mechanical properties, wear resistance, fretting corrosion and availability as well as the price. The application of proper biomaterials for hip implants is one of the major focal points in this article. Background information is also provided on metals used in other prosthetic devices and implant components. Titanium and its alloys, cobalt base alloys and stainless steels (bio-steels) are used for load-bearing hip implants. These three groups of metallic materials will be introduced and discussed in detail. Metals and their alloys are crystalline materials since their properties depend on the crystal lattice, chemical and phase compositions, grain size, lattice defects, crystalline texture and residual micro- and macro-stresses. All these features of biomaterials are formed during technological manufacturing, such as metallurgical process, solidification, plastic deformation (rolling and forging), machining, heat treatment and coating. All these technological processes work in optimal conditions in order to achieve the optimal microstructure and mechanical, chemical and biological properties. Amongst the above-mentioned particular properties of biomaterials, fretting is a major concern as regards hip implants at the femoral head and neck taper interface. Additional important mechanisms of interaction between the implant and the human body must be taken into account, i.e. diffusion stream of foreign particles and atoms from the implant to body fluids, to the tissue and to the bone. These foreign particles and atoms are released from the implant to the body fluid, to the tissue and to the bone as wear product during use. All together they contribute to the wear, i.e. loss of weight, strength or volume of hip components. Wear rates of ultrahigh molecular weight polyethylene mated against Ti-6Al-4V are significantly greater than the ones for Co-Cr-Mo alloys. Therefore, thermochemical surface treatments like diffusion ion nitriding should be applied to increase the resistance of titanium alloys to wear. Austenitic stainless steels are also used for temporary applications, but they have lower resistance to pitting corrosion than titanium and cobalt alloys. The purpose of the paper is to introduce a group of metallic materials, which is often chosen for surgical hip implants. Conclusions of the paper refer to information which support important medical and patient decisions on hip implants. Also, the development of biomaterials, their treatments, properties, surface layers and coatings are considered. All these features develop over time and need synergy and experience in the progress of the biomedical, mechanical and materials science.

Trunnion Failure of the Recalled Low Friction Ion Treatment Cobalt Chromium Alloy Femoral Head

BackgroundGross trunnion failure (GTF) is a rare complication in total hip arthroplasty (THA) reported across a range of manufacturers. Specific lots of the Stryker low friction ion treatment (LFIT) anatomic cobalt chromium alloy (CoCr) V40 femoral head were recalled in August 2016. In part, the recall was based out of concerns for disassociation of the femoral head from the stem and GTF. MethodsWe report on 28 patients (30 implants) with either GTF (n = 18) or head-neck taper corrosion (n = 12) of the LFIT CoCr femoral head and the Accolade titanium-molybdenum-zirconium-iron alloy femoral stems. All these cases were associated with adverse local tissue reactions requiring revision of the THA. ResultsIn our series, a conservative estimate of the incidence of failure was 4.7% (n = 636 total implanted) at 8.0 ± 1.4 years from the index procedure. Failures were associated with a high-offset 127° femoral stem neck angle and increased neck lengths; 43.3% (13 of 30) of the observed failures included implant sizes outside the voluntary recall (27.8% [5 of 18] of the GTF and 75.0% [8 of 12] of the taper corrosion cases). Serum cobalt and chromium levels were elevated (cobalt: 8.4 ± 7.0 μg/mL; chromium: 3.4 ± 3.3 μ/L; cobalt/chromium ratio: 3.7). The metal artifact reduction sequence magnetic resonance imaging demonstrated large cystic fluid collections typical with adverse local tissue reactions. During revision, a pseudotumor was observed in all cases. Pathology suggested a chronic inflammatory response. Impending GTF could be diagnosed based on aspiration of black synovial fluid and an oblique femoral head as compared with the neck taper on radiographs. ConclusionIn our series of the recalled LFIT CoCr femoral head, the risk of impending GTF or head-neck taper corrosion should be considered as a potential diagnosis in a painful LFIT femoral head and Accolade titanium-molybdenum-zirconium-iron alloy THA with unknown etiology. Almost half of the failures we observed included sizes outside of the voluntary recall.

Modular Necks and Corrosion - Review of Five Cases

This report updates previous articles and commentary presented on Modular Necks from our Tissue Sparing Implant Study Group. In July 2012 we reported that at two years post-op we had encountered no modular neck taper failures or any signs of fretting corrosion, or pseudo tumors associated with the ARC™ Stem.Today we describe five patients out of five hundred and forty-two who had total hip arthroplasty revision [titanium alloy stem, cobalt-chromium modular neck (c.c.) and c.c. modular head (32 mm or 36 mm), highly-cross-linked polyethylene liner, metal titanium plasma sprayed cementless metal cup]. All patients’ were female and all demonstrated progressive hip pain or late instability. All had debridement of the periarticular soft tissue, stem extraction with new primary length cementless stem replacement. At revision and early follow up all patients are doing well, however, we recommend heighten awareness in all active female patients with modular neck stem junctions.

Experience with Modular Necks for Cemented Total Hip Arthroplasty

This is a retrospective review of two series of using the same stem and modular neck design (R-120™) with the exception that the second series had an improved modular neck construct. Model I, 145 stems implanted between 2002 and 2005. Taper neck problems consisted of two neck trunion fractures at the neck stem junction and one modular neck disassociation at the modular junction. Stem was withdrawn from the market and redesigned to a more robust structure.Model II, 188 stems were implanted between 2007 and 2011 by the senior author utilizing the same surgical technique. There have been no modular neck taper problems.This paper will demonstrate that once a modular junction problem has been identified corrective action can be taken to resolve the problem. We advocate that there is a benefit to a modular neck cemented stem design and all modular junctions are not equal in design or function.

Evaluation of the Painful Dual Taper Modular Neck Stem Total Hip Arthroplasty: Do They All Require Revision?

Although dual taper modular-neck total hip arthroplasty (THA) design with additional neck-stem modularity has the potential to optimize hip biomechanical parameters by facilitating adjustments of leg length, femoral neck version and offset, there is increasing concern regarding this stem design as a result of the growing numbers of adverse local tissue reactions due to fretting and corrosion at the neck-stem taper junction. Implant factors such as taper cone angle, taper surface roughness, taper contact area, modular neck taper metallurgy, and femoral head size play important roles in influencing extent of taper corrosion. There should be a low threshold to conduct a systematic clinical evaluation of patients with dual-taper modular-neck stem THA using systematic risk stratification algorithms as early recognition and diagnosis will ensure prompt and appropriate treatment. Although specialized tests such as metal ion analysis and cross-sectional imaging modalities such as metal artifact reduction sequence magnetic resonance imaging (MARS MRI) are useful in optimizing clinical decision-making, overreliance on any single investigative tool in the clinical decision-making process for revision surgery should be avoided.