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Mechanically assisted crevice corrosion at the head-neck interface puts implants at risk of trunnionosis, femoral head dissociation, implant failure and the development of metallosis. Metal-on-Metal bearings have very low wear rates, significantly lower than metal-on-polytethylene, but their wear results in cobalt and chromium ion systemic distribution. This is a study of the MITCH metal-on-metal bearing surface coupled with an Accolade TMZF stem. This was a retrospective review of 24 total hip replacements 21 patients in that underwent MITCH TRH/Accolade TMZF implantation at a minimum of 12 years post operatively. The primary outcome of this study was all-cause revision with particular attention to revision due to trunnion failure and/or cobalt and chromium ion level. There was a revision rate of 66.7 % (n = 16) at a minimum of twelve years post operatively. Most notably there were six revisions for a gross trunnion failure. Two cases were revised for impending trunnion failure. There were seven cases revised for elevated serum cobalt and chromium levels and one was revised for unexplained pain. Patients in our study that underwent TMZF alloy cementless stems coupled with large cobalt chromium alloy heads are at high risk of catastrophic trunnion failure. The high rate of trunnnionosis in this implant combination is thought to be related to a significantly different Young's modulus due to a material mismatch coupled with galvanic corrosion. [ABSTRACT FROM AUTHOR]

Background: The risks of metal release due to fretting and corrosion at the head–neck junction and consequent adverse local tissue reaction (ALTR) have concerns in metal-on-polyethylene (MoP) total hip arthroplasty (THA). Although trunnions have become thinner in diameter to increase the range of motion, it has remained unclear whether this change affects metal release and ALTR in vivo. This study aimed to investigate serum metal concentrations and the prevalence of ALTR in MoP THA with a 9/10-mm stem trunnion. Patients and methods: A consecutive series of 37 hips that underwent THA using MoP grafted with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) with a 9/10-mm trunnion stem were retrospectively reviewed. Serum metal levels were assessed and compared with those in MoP THA with a 10/12-mm trunnion stem. ALTR was diagnosed with serum metal levels and cross-sectional images. The factors associated with serum metal levels were also assessed. Results: The median serum cobalt and chromium levels were 1.5 μg/L and 1.0 μg/L in the 9/10-mm group and 0.2 μg/L and 0.4 μg/L in the 10/12-mm group, respectively. ALTR was found in 5 hips of 3 patients. Revision surgery was performed in 4 hips, and all stem trunnions and femoral heads showed severe corrosion. Postoperative walking ability was associated with serum metal levels. Conclusion: It was found that a 9/10-mm stem trunnion with MoP grafted with PMPC had high risks of metal release in primary THA. Careful follow-up and cross-sectional imaging are needed to detect ALTR for early revision. [ABSTRACT FROM AUTHOR]

The calculation of sliding bearings for different types of friction is considered. The forces on the bearing are determined when the force between the shaft and bearing is almost zero. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effect of femoral head material on the impaction force, relative motion, and stability of the trunnion. There were three groups with different head materials (n = 5 per group)—CoCr Group: 36 mm CoCr heads, Ceramic Group: 36 mm ceramic heads, Ceramic + Sleeve Group: 36 mm ceramic heads with a titanium sleeve—that were all impacted twice and disengaged onto titanium alloy (Ti6al4V) trunnions in in vitro conditions. A high‐speed camera system was utilized to characterize relative displacement behavior of the head‐trunnion junction motion. The first impact force of Ceramic + Sleeve Group (14,241 SD, 935) was significantly lower than the first impact force in Ceramic Group (14,961 N, SD = 184). Ceramic + Sleeve Group had a lower magnitude bounce‐back displacement following the first impact (17.7 μm, SD = 11), p < 0.05) compared to CoCr Group (298.8 μm, SD = 84) and Group 2 (196.5 μm, SD = 31). Ceramic + Sleeve Group sat further on the trunnion (cumulative final displacement, 366.8 μm, SD = 71, p < 0.001) compared to CoCr Group (142.5 μm, SD = 41.8) and Ceramic Group (183.8 μm, SD = 30). Ceramic + Sleeve Group demonstrated two distinct disengagement patterns—(a) the sleeve disengaged from the trunnion (pull‐off force 6810 N), and (b) the femoral head disengaged from the sleeve (pull‐off force 18,620 N), with large fluctuations in pull‐off force. The presence of a titanium sleeve with a ceramic head resulted in significant differences in impaction force on the trunnion, motion and displacement, and unique mechanisms for disengagement. Further investigation is required to determine potential clinical impact. [ABSTRACT FROM AUTHOR]

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Introduction: Trunnion geometry is known to vary between hip systems. Trunnionosis and the impact of trunnion design on total hip arthroplasty (THA) survival, has gained attention as a failure mechanism. We sought to report the differences in patient-reported outcome measures (PROMs) between the most commonly utilised modern THA trunnions. Methods: We reviewed primary unilateral THA patients from May 2007 to October 2011. The most frequently used stems were included. LEAS, HOOS subdomains, and SF-12 were obtained pre and post operatively while satisfaction was measured at 2 years after THA. Trunnions were grouped by taper geometry and manufacturer. The 2-year change in PROMs for each trunnion was compared to the pooled 2-year change in HOOS for all other trunnions. Results: 3950 THA patients were studied. 6 trunnion designs were evaluated from 5 manufacturers. The range in differences between the 2-year change in individual PROMs were as follows: HOOS pain (0.6–2.4), HOOS symptoms (0–3.8), HOOS ADL (0.4–4), and HOOS QOL (0.5–3.6). None of the differences in the 2-year change in PROMs reached a minimal clinically important change (MCIC), which we previously determined to be a minimum of 9 points for all HOOS domains. Conclusion: All of the trunnions designs utilised in our study cohort demonstrated excellent clinical results. Small differences were well below the known MCIC; and were not clinically relevant. The findings of this study should prompt further investigations into the long-term impact of trunnion design on clinical patient-reported outcomes. [ABSTRACT FROM AUTHOR]

Femoral head-neck modularity in total hip arthroplasty (THA) is advantageous but taper corrosion at the trunnion can result in implant failure. We report two cases of acute catastrophic trunnion failure with a TMZF alloy cementless stem. Demographic, clinical, radiographic and operative data including implant retrieval was recorded and is presented. Case 1: A 79 year old farmer presented with sudden onset of hip pain and an inability to weight bear. He underwent a cementless large diameter stemmed metal-on-metal system (MITCH acetabular component, 56mm cobalt chrome head 4.5 lateralised Accolade TMZF, Stryker) nine years previously. He denied symptoms prior to his presentation to the Emergency Department. Case 2: An 86 year old gentleman presented with sudden onset of hip pain and inability to weight bear. He underwent a cementless large diameter stemmed metal-on-poly THA (Trident acetabular component, X3 polyethylene insert, 44mm cobalt chrome head, 4.5 lateralised Accolade TMZF, Stryker)nine years previously. This man had been complaining of mild hip symptoms prior to presentation. Patients that have received TMZF alloy cementless stems coupled with CoCr alloy heads are at risk of catastrophic trunnion failure. Importantly, background trunnion corrosion may occur silently and present emergently irrespective of surveillance. [ABSTRACT FROM AUTHOR]

Background: Multiple cases of dissociation of the head from the neck termed as gross trunnion failure (GTF) in total hip replacement have been described. Very little quantitative data is available for patient and implant factors associated and predisposing to this complication.Study Purpose: To systematically review and analyze all studies which have gross trunnion failure in case of metal on polyethylene (MoP) total hip replacement.Methods: PubMed database was searched. We also performed a secondary search by pearling bibliography of all full text articles obtained. Predefined inclusion and exclusion criteria were used for abstract screening by two independent observers. A total 46 cases met our inclusion criteria. These were included in the final analysis and data was pooled.Results: Till date, 46 cases of GTF in MoP THR have been reported. The mean age at time of revision was 70.13 years (range 50 to 89 years). The mean time to revision surgery was 8.24 years (range 4.7 to 14 years). 91.4% cases were male. BMI was ≥ 25 in 38/41 cases and ≥ 30 in 21/41 cases. Pain (95.5%) and difficulty or inability to walk (97.7%) were the most common symptoms. A total of 19/44 cases described varying sounds like click, clunk, and pop before dislocation. Accolade TMZF/TMZF plus was the most common stem used in 34/46 cases. The stem neck angle was 127 degrees in 97% cases (32/33 cases). A positive neck offset of 4 mm or more was used in 91.1% cases (40/44 cases). The head size ≥ 36 mm in approximately 90% cases. The head material was cobalt chromium in all 45 cases, where data was available. Among the intra-operative findings, the most common findings were metallosis (41/44), black or brow coloured synovial fluid (21/44), pseudotumour (19/44), synovial hypertrophy (18/44), damage to the abductor musculature (17/44), proximal femoral osteolysis (5/44 cases), and heterotrophic ossification (2/44 cases). Histopathological analysis was available in 11 cases and was suggestive of fibrous tissue with chronic cellular infiltrate in all cases. The serum cobalt and chromium concentrations were raised above normal in 86.4% (19/22) and 21.7% cases (5/23) respectively.Conclusions: Gross trunnion failure may not be as uncommon as was previously thought. A number potential associations and predisposing factors of this complication have been highlighted in this review. But due to small sample size and weak level of evidence, further studies are needed in this field. [ABSTRACT FROM AUTHOR]

Introduction: Material loss at the head-neck junction in total hip arthroplasty may cause adverse clinical symptoms and implant failure. The purpose of this study was to quantitatively examine the effects of head size, stem material and stem offset on material loss of the head-neck taper interface of a single trunnion design in retrieval implants of metal on polyethylene bearing surfaces. Methods: A retrieval study was performed to identify all 28-mm and 32-mm femoral heads from a single implant/taper design implanted for >2 years. This included n = 56 of the 28-mm heads and n = 23 of the 32-mm heads. The 28-mm femoral heads were matched to 32-mm femoral heads based on time in vivo and head length. A coordinate measuring machine was used to determine maximum linear corrosion depth (MLD). Differences in MLD for head diameter, stem material, and stem offset were determined. Results: There were no differences between groups for age, gender, BMI, or implantation time. There was no difference in MLD between 28 mm and 32 mm matched paired head diameters (p = 0.59). There was also no difference in MLD between titanium or cobalt-chromium stems (p = 0.79), and regular or high-offset stems (p = 0.95). Conclusion: There is no statistical difference in femoral head MLD at the head-neck junction in THA between 28-mm and 32-mm matched paired femoral heads, similar or mixed alloy coupled femoral head stem constructs, and regular or high offset stems. [ABSTRACT FROM AUTHOR]

ABSTRACT: Mechanically assisted crevice corrosion (MACC) is a mechanism for trunnion damage in total hip arthroplasties (THAs). Retrieval studies have shown reduced MACC‐related damage for ceramic heads compared with cobalt–chromium (CoCr) heads. We propose that ceramic heads demonstrate fretting at higher cyclic compressive loads than CoCr heads on titanium alloy trunnions in a simulated corrosion model. A closed electrochemical chamber was used to measure fretting current onset loads for two modern titanium alloy trunnions (Zimmer 12/14 and Stryker V‐40) in which trunnion failure has been reported. Ceramic and CoCr alloy 36 + 0 mm heads were impacted on each trunnion and cyclically loaded at 3 Hz with increasing magnitude from 100 to 3,400 N for 540 cycles. Onset load was the cyclic compressive load at which the slope of the average fretting current increased significantly. A CoCr head with V40 trunnion demonstrated the lowest onset load (1,400 N), while the V40 trunnion with a ceramic head showed the highest onset load (2,200 N). Significant differences occurred in average fretting current between head materials for V40 trunnions (p < 0.001) at loads over 2,000 N. CoCr‐12/14 and ceramic‐12/14 couples demonstrated similar onset loads (2,000 N). All head–trunnion combinations showed cyclical fretting response to loading at 100 N. Head material composition was observed to increase fretting at the taper junction but the effect was taper geometry dependent. Using ceramic heads may reduce the phenomena of trunnion fretting and corrosion but the effect of both trunnion geometry and metallurgy warrants further investigation. Statement of clinical significance: Trunnion corrosion may occur with titanium alloy stems regardless of the head material used. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1630–1636, 2018. [ABSTRACT FROM AUTHOR]

Introduction: Since the recent failure of certain coating models, hybrid implants (coated acetabular inserts with conventional stems) and stems with modular necks, there has been growing interest in the consequences of the generation and release of metal particles at the prosthetic interfaces. The use of ceramic heads has recently been described as an option for reducing the production of metal ions and their consequences. Case report: The present case report describes the first complete metallisation of a ceramic head secondary to an excessive release of metal ions at the head-neck junction. Conclusions: We believe this to have occurred due to the use of 12/14 cones of different manufacturers. [ABSTRACT FROM AUTHOR]

Modular hip replacement components offer numerous advantages, and the modular femoral component has become standard for contemporary total hip implants. Recent reports of mechanically assisted crevice corrosion (MACC) at the head-neck junction, and associated adverse local tissue reactions (ALTRs), have renewed concerns for complications attributed to modularity. This manuscript describes the diagnosis, prognosis, and treatment options for MACC and highlights how appropriate pre-revision evaluation and planning, in conjunction with meticulous surgical technique, should be followed to avoid complications and achieve optimal surgical outcomes. Future directions for research include biomechanical, clinical, and retrieval studies. [ABSTRACT FROM AUTHOR]

Trunnionosis is defined as wear of the femoral head-neck interface and has recently been acknowledged as a growing cause of total hip arthroplasty failure. Some studies have reported that it accounts for up to 3 % of all revisions. The exact cause of trunnionosis is currently unknown; however, postulated etiologies include modular junction wear, corrosion damage, and metal ion release. Additionally, implant design and trunnion geometries may contribute to the progression of component failure. In order to aid in our understanding of this phenomenon, our aim was to present the current literature on (1) the effect of femoral head size on trunnionosis, (2) the effect of trunnion design on trunnionosis, (3) localized biological reactions associated with trunnionosis, and (4) gross trunnion failures. It is hoped that this will encourage further research and interest aimed at minimizing this complication. [ABSTRACT FROM AUTHOR]

In the article, the authors discuss the use of the old Morse taper mechanical principle and femoral head modularity in total hip arthroplasty. Topics include the goal of arthroplasty to restore the biomechanical parameters of the hip joint to achieve optimal leg length and stability and how the stress distribution among the parts of the Morse taper is affected by taper angle, contact length, and inner and outer diameters.

Recent problems with large head metal on metal hip replacements have spiked renewed interest in the head-neck junction. A thorough knowledge of the principles of the locking mechanism, the assembly technique and affecting factors on the strength of this junction is needed. Currently a confusing variability in terms is used to describe this junction. This overcomplicates an already complex issue. The purpose of this literature review is to collect and list the different terms used and to propose a uniform terminology. Two authors independently searched the electronic databases of PubMed, CINAHL and MEDLINE with specific key words and combinations according to the PRISMA guidelines. The initial search yielded a total of 518 articles with ultimately 53 articles included in the present analysis. No consensus for a uniform term for the 2 sides of the head-stem junction was found. Since there is already pronounced variability in taper designs between different manufacturers (even so similarly named, e.g. "12/14"), a uniform terminology could be the first step to simplify the situation. "Male" and "female taper" is proposed as the appropriate terminology for the stem and head junction in hip replacement, respectively. The importance of the assembly technique understanding the principles of the locking mechanism is emphasised. [ABSTRACT FROM AUTHOR]

Implant modularity has recently come under increasing scrutiny due to concerns regarding wear, corrosion and potential adverse reactions to metal debris. This review outlines the evolution and development of the femoral stem trunnion and relates this to contemporary issues now encountered. Despite different manufacturers producing what appear to be similar trunnion designs, there is still a lack of standardisation, with small but significant design variations. Wear and corrosion is certainly not a new phenomenon, but recent changes in design and the use of larger metal head sizes has potentially made the problem more prevalent. These issues along with steps to avoid these problems are discussed. [ABSTRACT FROM AUTHOR]

ABSTRACT Modular hip implants allows for the adjustment of leg length, offset, and the ability to remove the head for acetabular exposure during primary and revision surgery. The design of the Morse taper facilitates the intimate contact of the conical trunnion of the femoral stem (male component), with the conical bore of the femoral head (female component). Orthopaedic trunnion tapers are not standardized and vary in length, taper angle, and base dimension. Variations in the design and surface characteristics of the trunnion, will directly reflect on the interface at the taper junction and can influence the likelihood of subsequent wear, corrosion and longevity of the implant. The effect of surface topography of trunnions on commercially available hip stems has not yet been considered as a possible contributing factor in the corrosion observed at taper junctions. In this study we analyzed the surface topography and surface roughness of randomly selected commercially available femoral hip stem trunnions to obtain a greater insight into their surface characteristics. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:98-105, 2015. [ABSTRACT FROM AUTHOR]

In contrast to the articulating and taper surfaces of failed total hip replacements, volumetric wear analysis of trunnions is not routinely performed. Metal wear particles from the trunnion may contribute not only to the failures of metal-on-metal total hip replacements but also to all hip replacements utilising metal trunnions. A validation study was performed with the material removed in stages from the trunnions of an Exeter V40 stem, a Corail stem and an Accolade stem to simulate different magnitudes of wear. The material loss from the trunnions was measured both volumetrically with a coordinate measuring machine and gravimetrically with a high-precision balance. A cohort of 28 ex vivo trunnions was also measured using the coordinate measuring machine. The maximum error between the two methods was found to be 0.13 mm3. This result was comparable with the coordinate measuring machine method for the taper surface (0.2 mm3). The ex vivo trunnions had a median wear volume of 0.14mm3 (range: 0.04–0.28 mm3). This is the first study to determine the accuracy of volumetric wear measurements of trunnions by comparing against gravimetric measurements. Volumetric wear analysis of trunnions may provide additional insights into failures of modular total hip prostheses and will be performed routinely at our centre. [ABSTRACT FROM AUTHOR]

We have developed a graphic representation (APS shot-range diagrams) of achievable shot coordinates with the automatic positioning system (APS) for Gamma Knife stereotactic radiosurgery. We formulated a mathematical relationship between the APS coordinate system and the Leksell frame coordinate system (frame-system) by considering the relative translation and rotation. Using the transformation equations, we calculated the Y- Z coordinate domain in the frame-system (domain B), which corresponds to the known coordinate domain achievable in the APS coordinate system (domain A). APS shot-range diagrams were presented by overlaying of domain B over domain A so that one can easily visualize the achievable shot coordinates with APS for various gamma angles. Domains A and B are identical for a 90° gamma angle, but they are different for other gamma angles. Applications of the diagrams to clinical cases, in which Leksell GammaPlan treatment planning software automatically set some of the shots in a treatment plan as trunnion shots because of the APS coordinate limit, enabled us to avoid the trunnion shots, and consequently to achieve much faster treatment delivery. In conclusion, APS shot-range diagrams can be used for achieving more efficient treatment delivery by avoiding unnecessary trunnion shots with a Gamma Knife unit equipped with the APS. [ABSTRACT FROM AUTHOR]

This study was designed to test whether the number of impacts, the experience of the surgeon or impact force made significant difference in pull off forces. The forces applied by 10 orthopaedic surgeons (five residents and five attending staff) to impact the femoral head onto the trunnion of a femoral component were recorded. The resultant forces were then divided into four energy levels and compared to determine if the number of impacts would make a difference in pull off strength. No significant differences existed between the resident versus attending groups in magnitude of force applied. Through ANOVA testing, it was found that at each of the energy levels, multiple blows demonstrated a significant pull off strength difference compared to a single blow. Increased pull off force was also noted when the magnitude of force of the applied blows was increased. We recommend at least two firm, axially aligned blows to impact the femoral head onto the trunnion intra-operatively. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Federal Institute for Materials Research and Testing (BAM) intends to provide a new guideline for the analysis and assessment of lid and trunnion systems. This guideline is discussed in the present paper with respect to its contents and structure, its compatibility with other guidelines and selective technical issues to demonstrate its use. Particularly, the motivation, the principles and the background of the guideline are addressed. Therefore, the present paper discusses current conclusions drawn from experimental results and the wide use of advanced analysis methods such as finite element analysis as well as the incorporation of these aspects in the guideline draft. [ABSTRACT FROM AUTHOR]