Modular Hip Research Articles

Protein-metal interactions due to fretting corrosion at the taper junction of hip implants: An in vitro investigation using Raman spectroscopy

Modular hip implants are a clinically successful and widely used treatment for patients with arthritis. Despite ongoing retrieval studies the understanding of the fundamental physico-chemical mechanisms of friction and wear within the head-taper interface is still limited. Here, we Raman-spectroscopically analyze structural features of the biotribological material which is formed within the taper joint between Ti6Al4V and low-carbon cobalt alloy or high-nitrogen steel surfaces in in vitro gross-slip fretting corrosion tests with bovine calf serum. As a function of the fretting duration, we investigate short and long aliphatic chains and their adsorption behavior on the cobalt- and steel-type surfaces. Using the intensity and frequency shifts of the amide I and III Raman bands, we furthermore identify progressive protein folding and unfolding including the secondary structures of α-helix, β-sheet, and random-coil configuration as well as the formation of proteinaceous clusters depending on the hydrophilicity of the metallic surfaces. We additionally find a mixture of chromates and iron oxides with tryptophan and tyrosine at the worn cobalt alloy and high-nitrogen steel surfaces, respectively. Also, for long fretting duration, sp2 hybridized amorphous carbon is formed due to fretting-induced cleavage of proteins. Statement of significanceDespite efforts enhancing the biomedical tribology of hip implants, the impact of the organic environment on friction and wear at the femoral head-stem taper interface is limitedly understood. Using Raman spectroscopy we resolve structural changes within the biotribological material agglomerated at biomedical-grade metal alloys due to metal-organic interactions during in vitro fretting corrosion tests. Adsorption of short and long aliphatic chains, progressive protein (un)folding and proteinaceous cluster formation depend to a distinguishable extent on the fretting duration and type of alloy. Chromates and iron oxides are mixed with tryptophan and tyrosine, and amorphous carbon is formed resulting from a fretting-induced cleavage of serum proteins. Such information spectroscopically gleaned from biotribological material are vital to improve the design and performance of taper junctions.

Outcome of Endoprosthetic Hip Reconstruction Following Resection of Malignant Bone Tumors.

Over the past few decades, tumor arthroplasty has evolved into an established therapeutic approach for addressing bone defects following tumor resection in the extremities. As the diagnosis has a significant impact on patients' lives, it is important to give clear expectations for functional recovery. Therefore, we investigated both the functional outcomes and the quality of life (QoL) after tumor arthroplasty for malignant hip tumors. This retrospective study included patients who had undergone resections of malignant hip tumors with consecutive modular hip arthroplasty between 2010 and 2018. Demographics, tumor entity, and complications stemming from both tumors and treatments were evaluated through the analysis of medical records and perioperative records. The assessment of functional outcomes was conducted with the following patient-reported outcome measures (PROMs): the Harris Hip Score (HHS), Musculoskeletal Tumor Society Score (MSTS), and the Short Form Survey 36 (SF-36). Furthermore, we performed subgroup analysis in two groups: one divided into survivors and non-survivors, as well as younger individuals (<57 years) and older individuals (>57 years). A total of 30 patients were included in the study. At the time of follow-up, 19 patients were deceased. The average duration of follow-up was 3.2 (±2.51) years. The average age at the time of surgery was 60.3 (±15.20) years. Notably, there were no cases of amputation reported (0%). Five cases of implant failure were identified (16.67%). Among these, one was attributed to infection (3.3%), while four resulted from aseptic loosening (13.3%). In terms of functional outcomes, MSTS indicated good results (18 ± 7; range: 7-28; 60%), and the HHS demonstrated moderate outcomes (75.3%). Younger survivors (<57 years) exhibited notably superior results in terms of both the MSTS and physical functioning in the SF-36 (p = 0.03). In summary, this study shows declining tumor arthroplasty-related complications and satisfying functional outcomes as well as QoL. Noteworthy aspects include the relatively low rates of amputation and local tumor recurrences, which significantly favor the selection of appropriate therapeutic options. Moreover, the findings underscore the substantial impact of patients' age on overall functionality and engagement in daily activities.

Understanding the role of head size and neck length in micromotion generation at the taper junction in total hip arthroplasty

Modular hip implants allow intra-operative adjustments for patient-specific customization and targeted replacement of damaged elements without full implant extraction. However, challenges arise from relative micromotions between components, potentially leading to implant failure due to cytotoxic metal debris. In this study magnitude and directions of micromotions at the taper junction were estimated, aiming to understand the effect of variations in head size and neck length. Starting from a reference configuration adhering to the 12/14 taper standard, six additional implant configurations were generated by varying the head size and/or neck length. A musculoskeletal multibody model of a prothesized lower limb was developed to estimate hip contact force and location during a normal walking task. Following the implant assembly, the multibody-derived loads were imposed as boundary conditions in a finite element analysis to compute the taper junction micromotions as the relative slip between the contacting surfaces. Results highlighted the L-size head as the most critical configuration, indicating a 2.81 μm relative slip at the mid-stance phase. The proposed approach enables the investigation of geometric variations in implants under accurate load conditions, providing valuable insights for designing less risky prostheses and informing clinical decision-making processes.

Influence of a Modified Procedure of Joining Ceramic Head and Adapter Sleeve on the Stem Taper in Revision: An Experimental Study.

In revision operations, ceramic heads of modular hip implants can be replaced. As the surface of the stem taper can be damaged, additional adapter sleeves are applied. The components are usually connected manually by the surgeon in a one-step procedure by hammer impacts. In this study, we investigated a two-step joining procedure with reproducible impaction force. First, the adapter sleeve and head were joined quasi-statically with a force of 2 kN using an assembly device. In the second step, these components were applied to the stem taper using a pulse-controlled instrument. For reference, the joints were assembled according to standard conditions using a tensile testing machine. An average pull-off force of 1309 ± 201 N was achieved for the components joined by the instrument, and the average measured values for the components joined by the testing machine were 1290 ± 140 N. All specimens achieved a force >350 N when released and therefore met the acceptance criterion defined for this study. This study showed that a modified procedure in two steps with a defined force has a positive effect on the reproducibility of the measured joining forces compared to previous studies.

Analysis of modular taper fractures of the revision hip stem Prevision and comparison of the original and current taper design.

The risk of mechanical failure of modular revision hip stems is frequently mentioned in the literature, but little is currently known about the actual clinical failure rates of this type of prosthesis. The current retrospective long-term analysis examines the distal and modular failure patterns of the Prevision hip stem from 18 years of clinical use. A design improvement of the modular taper was introduced in 2008, and the data could also be used to compare the original and the current design of the modular connection. We performed an analysis of the Prevision modular hip stem using the manufacturer's vigilance database and investigated different mechanical failure patterns of the hip stem from January 2004 to December 2022. Two mechanical failure patterns were identified: fractures in the area of the distal fluted profile (distal stem fracture) and failure of the modular taper (modular fracture). A failure rate of 0.07% was observed for distal stem fracture, and modular fracture rates of 1.74% for the original and 0.013% for the current taper design. A low risk of mechanical failure for both fracture types was observed compared to other known complications in revision hip arthroplasty. In addition, the data show that a design change did significantly reduce the risk of a modular fracture.

FE Investigation of Design and Quality Control-Related Issues Contributing to Metal-On-Metal Hip Implant Failures

High levels of cobalt and chromium ions were detected in the bodies of multiple recipients of modular cobalt chrome molybdenum metal-on-metal hip implants, necessitating the revision of their implants. A forensic engineering investigation of provided discovery documents and existing literature regarding the design, manufacturing, and clinical testing of these modular hip implants was performed. The investigation revealed that the modular interfaces of the implant allowed for micromotion to induce mechanically assisted crevice corrosion at these surfaces. The debris from this corrosion resulted in the release of metal ions into the bodies of the users, forming pseudotumors and compromising the user’s health and wellbeing. The effect of this corrosion was enhanced by the galvanic couple that existed between the modular components of the implant. In addition, scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) analysis identified silicon carbide (SiC) and aluminum oxide (AL2O3 ) particles left behind from polishing, which were embedded in the ball and liners. These particles accelerated the wear of the hip implant and further exacerbated the release of metal ions. The designers of future hip implants should take care in preventing the occurrence of the above-stated factors.

Influence of manufacturing-related deviations on the junction strength of double modular hip endoprostheses

Osteoarthritis often requires surgical treatment with joint replacement. By using double modular hip endoprostheses, it is feasible to adapt the femoral angle to the patient and thus improve its biomechanics so that the anatomy of the patient can be better taken into account. Another advantage is that in case of damage of the taper, the stem can be left in the bone and only the neck adapter needs to be replaced. However, these advantages are accompanied by a higher risk of revision due to fretting of the additional connection. Fretting is influenced by angular deviations of the pairing. Therefore, the influence of the manufacturing-related angle deviations on the junction strength of the pairing Ti-6Al-4V ELI/ Ti-6Al-4V ELI and CoCr28Mo6/ Ti-6Al-4V ELI was investigated. Initially, outer tapers with two different surface topographies and defined angular deviation were manufactured. The tapers were joined with a static force of Fassembly = 4 kN and subsequently the separation forces of the junction and the contact area after push-out tests were investigated. Material-specific differences regarding separation forces were found. The CoCr/Ti pairing shows greater average separation forces than the Ti/Ti pairing, although the resulting contact area of the Ti/Ti pairing is larger than the contact area of the CoCr/Ti. However, the resulting separation forces are independent of the investigated contact cases and the surface topography. This enables the adaption of tolerances within the manufacturing process to ensure the secure utilization of double modular hip endoprostheses.

A convolutional neural network for high throughput screening of femoral stem taper corrosion.

Corrosion at the modular head-neck taper interface of total and hemiarthroplasty hip implants (trunnionosis) is a cause of implant failure and clinical concern. The Goldberg corrosion scoring method is considered the gold standard for observing trunnionosis, but it is labor-intensive to perform. This limits the quantity of implants retrieval studies typically analyze. Machine learning, particularly convolutional neural networks, have been used in various medical imaging applications and corrosion detection applications to help reduce repetitive and tedious image identification tasks. 725 retrieved modular femoral stem arthroplasty devices had their trunnion imaged in four positions and scored by an observer. A convolutional neural network was designed and trained from scratch using the images. There were four classes, each representing one of the established Goldberg corrosion classes. The composition of the classes were as follows: class 1 (n = 1228), class 2 (n = 1225), class 3 (n = 335), and class 4 (n = 102). The convolutional neural network utilized a single convolutional layer and RGB coloring. The convolutional neural network was able to distinguish no and mild corrosion (classes 1 and 2) from moderate and severe corrosion (classes 3 and 4) with an accuracy of 98.32%, a class 1 and 2 sensitivity of 0.9881, a class 3 and 4 sensitivity of 0.9556 and an area under the curve of 0.9740. This convolutional neural network may be used as a screening tool to identify retrieved modular hip arthroplasty device trunnions for further study and the presence of moderate and severe corrosion with high reliability, reducing the burden on skilled observers.

Longitudinal Radiographic Bone Density Measurement in Revision Hip Arthroplasty and Its Correlation with Clinical Outcome.

The subjective analysis of conventional radiography represents the principal method for bone diagnostics in endoprosthetics. Alternative objective quantitative methods are described but not commonly used. Therefore, semi-quantitative methods are tested using digital computation and artificial intelligence to standardize, simplify, and ultimately improve the assessment. This study aimed to evaluate the correlation between relative density progressions and clinical outcomes. Radiographs and clinical examinations before and 24 and 48 weeks after surgery were obtained from sixty-eight patients with a modular hip stem. For the calculation of the relative bone density, the modal gray values of the Gruen zones were measured using ImageJ and were normalized by gray values of the highest and lowest ROI. The clinical outcomes were measured according to the Harris hip score before evaluating them for correlations. Analyses were performed separately for subgroups and bone regions. The Harris hip score increased from 44.15 ± 15.00 pre-operatively to 66.20 ± 13.87 at the latest follow-up. The relative bone density adjustment of Gruen zone 7 showed a significant correlation to its clinical outcome. Other bone adaptations could be realistically reproduced and differences by regional zones and patients' histories visualized. Next to the simplicity and that no additional examination is required, the method provides good semi-quantitative results and visualizes adaptations, which make it suitable for use.

Trunnions and Modularity in Total Hip Arthroplasty: A Historical Review With Current Clinical Implications.

Trunnion in total hip arthroplasty refers to the interface between the neck of a femoral stem and the femoral head. Clinical complications arising from damage to this junction, whether it be due to mechanical wear, corrosion, or a combination, are referred to as mechanically assisted crevice corrosion (MACC), also commonly known as trunnionosis. With the use of modular hip prostheses, which help customize offset and leg length to an individual patient's anatomy, the incidence of MACC and revision due to MACC has increased in recent years. Although the cause of MACC is multifactorial, with patient factors and technique factors contributing to this condition, taper design and geometry, metallurgical properties of implants, and size mismatch of the bearing couple are some of the implant factors that have also been implicated in this clinical phenomenon. Understanding the history of taper design and geometry, the track record of older implants, and the rationale behind the development of current prostheses can help surgeons choose the right implants for their patients and accurately assess the pros and cons of new implants being introduced to the market each year.

Evaluation of fretting corrosion fatigue in burnishing of Ti6Al4V component for artificial hip joint

Modular hip replacements provide a flexible way to reconstruct the joint with optimized biomechanics, but one of the most common causes of modular hip prostheses failure is the fretting corrosion at the neck-head interface combined with their related micro-motion. In this context, the present study aims to improve the neck surface strength by means of burnishing process. An experimental campaign on Ti6Al4V hip joint neck was carried out at varying burnishing parameters: force and speed. The main surface integrity parameters affecting the neck performance have been evaluated, namely mean surface roughness, micro hardness, affected layer and microstructure. Afterwards, fretting corrosion fatigue tests on necks and alumina ceramic heads were performed under standard conditions simulating human walking. The relative motions at the neck-head interface were analyzed by an innovative technique able to detect changes during the test with high accuracy.

Modular hip exoskeleton improves walking function and reduces sedentary time in community-dwelling older adults

BackgroundDespite the benefits of physical activity for healthy physical and cognitive aging, 35% of adults over the age of 75 in the United States are inactive. Robotic exoskeleton-based exercise studies have shown benefits in improving walking function, but most are conducted in clinical settings with a neurologically impaired population. Emerging technology is starting to enable easy-to-use, lightweight, wearable robots, but their impact in the otherwise healthy older adult population remains mostly unknown. For the first time, this study investigates the feasibility and efficacy of using a lightweight, modular hip exoskeleton for in-community gait training in the older adult population to improve walking function.MethodsTwelve adults over the age of 65 were enrolled in a gait training intervention involving twelve 30-min sessions using the Gait Enhancing and Motivating System for Hip in their own senior living community.ResultsPerformance-based outcome measures suggest clinically significant improvements in balance, gait speed, and endurance following the exoskeleton training, and the device was safe and well tolerated. Gait speed below 1.0 m/s is an indicator of fall risk, and two out of the four participants below this threshold increased their self-selected gait speed over 1.0 m/s after intervention. Time spent in sedentary behavior also decreased significantly.ConclusionsThis intervention resulted in greater improvements in speed and endurance than traditional exercise programs, in significantly less time. Together, our results demonstrated that exoskeleton-based gait training is an effective intervention and novel approach to encouraging older adults to exercise and reduce sedentary time, while improving walking function. Future work will focus on whether the device can be used independently long-term by older adults as an everyday exercise and community-use personal mobility device.Trial registration This study was retrospectively registered with ClinicalTrials.gov (ID: NCT05197127).

An Overview of the Stability and Fretting Corrosion of Microgrooved Necks in the Taper Junction of Hip Implants.

Fretting corrosion at the head-neck interface of modular hip implants, scientifically termed trunnionosis/taperosis, may cause regional inflammation, metallosis, and adverse local tissue reactions. The severity of such a deleterious process depends on various design parameters. In this review, the influence of surface topography (in some cases, called microgrooves/ridges) on the overall performance of the microgrooved head-neck junctions is investigated. The methodologies together with the assumptions and simplifications, as well as the findings from both the experimental observations (retrieval and in vitro) and the numerical approaches used in previous studies, are presented and discussed. The performance of the microgrooved junctions is compared to those with a smooth surface finish in two main categories: stability and integrity; wear, corrosion, and material loss. Existing contradictions and disagreements among the reported results are reported and discussed in order to present a comprehensive picture of the microgrooved junctions. The current research needs and possible future research directions on the microgrooved junctions are also identified and presented.

The Role of the Assembly Force in the Tribocorrosion Behaviour of Hip Implant Head-Neck Junctions: An Adaptive Finite Element Approach.

The cyclic loading, in the corrosive medium of the human body, results in tribocorrosion at the interface of the head-neck taper junction of hip implants. The resulting metal ions and wear debris adversely affect the local tissues. The force applied by surgeons to assemble the junction has proven to play a major role in the mechanics of the taper junction which, in turn, can influence the tribocorrosion damage. Recently, finite element method has been used to predict the material loss at the head-neck interface. However, in most finite element studies, the contribution of electrochemical corrosion has been ignored. Therefore, a detailed study to investigate the influence of the assembly force on the tribocorrosive behaviour of the head-neck junction, which considers both the mechanical and chemical material removal, is of paramount interest. In this study, a finite-element-based algorithm was used to investigate the effect of assembly force on the tribocorrosion damage at the junction interface, for over four million cycles of simulated level gait. The patterns of the material removal in the modelling results were compared with the damage patterns observed in a group of retrieved modular hip implants. The results of this study showed that for different cases, chemical wear was in the range of 25-50% of the total material loss, after four million cycles. A minimum assembly force (4 kN for the studied cases) was needed to maintain the interlock in the junction. The computational model was able to predict the damage pattern at the retrieved head-neck interface.

FINITE ELEMENT APPROACH TO DESIGN OF MODULAR HIP IMPLANTS MINIMIZING FRETTING WEAR

Total hip replacement is a commonly used technique for the treatment of degenerative joint diseases. Several design innovations are pursued to meet their growing clinical need. Modular hip implants have emerged to become a mainstay in design as these offer a large array of femoral offsets, length adjustment and greater stability. A major disadvantage of modular implants is that each interface becomes a potential site for corrosion, fretting and fatigue between mating surfaces, which eventually leads to mechanical-assisted crevice corrosion. Though experimental studies have revealed the role of different implant design or manufacturing factors that affect MACC, finite element simulation models developed so far factor in only a few design modification in order to improve implant life. The objective of this study is to investigate the effect of bulk porosity, surface roughness and strength of the bone at the implantation site on implant performance in terms of contact pressure, micromotion and wear depth. It is observed that a three times increase in surface roughness increases wear depth by 1.2 times, increases porosity by 120%, causes wear to change two-fold, while weaker bone shows appreciably higher wear. The findings of this study provide a comprehensive tool to design hip implant with reduced probability of failure.

Decomposition of micromotion at the head-neck interface in total hip arthroplasty during walking

Fretting corrosion as one of the leading causes for failure of modular hip prostheses has been associated with micromotion at head-neck taper junction. Decomposition of micromotion is helpful to promote the development of more realistic experiments investigating failure mechanisms of the head-neck junction in total hip arthroplasty. The aim of this study was to decompose the complex three-dimensional micromotion at the head-neck junction into multiple fundamental modes, including three translational and three rotational components. A three-dimensional finite element model composed of head-neck junction, liner and acetabular cup with a typical 12/14 taper size, as well as the taper mismatch of −4', was developed during walking. The analysis was divided into three procedures: a) the assembly simulation of the head and neck during surgery, b) verification with a simplified axisymmetric model, and c) three-dimensional modelling under normal walking. This study revealed that the main forms of micromotion contained circumferential, longitudinal micromotion and longitudinal rolling toggling, and were closely related to the state of motion. The maximum translational micromotion was predicted to be 10.9 μm during the walking gait, with the predominant modes of the circumferential translation of 9.6 μm, the longitudinal translation of 5.5 μm and the longitudinal rotation of 0.29° along the taper junction. These findings may provide design considerations for further experimental testing about fretting and facilitate the understanding of the fretting mechanisms in hip prostheses.

Adult presentation of severe sequelae of Tom Smith arthritis treated with bilateral total hip arthroplasty: A case report.

Introduction and importanceTom Smith arthritis (TSA) is a pyogenic arthritis of the hip joint that occurs in infancy and has considerable morbidity. Reports on surgical management of severe hip dysplasia in adulthood secondary to TSA are extremely limited. We describe a patient who successfully underwent a bilateral total hip arthroplasty for the severely damaged hip joints secondary to TSA with satisfactory functional outcomes.Case presentationA 25-year-old female was unable to walk for more than 10 ft due to pain in both hips and knees predominantly on the left side. She developed pyogenic septic arthritis with sepsis at 6 weeks of age and underwent multiple surgical procedures to drain the infection and for reconstruction. She had limited range of motion and was severely disabled. She underwent an uneventful left total hip arthroplasty and two years later, a right total hip arthroplasty using S-ROM modular hip systems. The pre and post-operative Harris Hips scores were 53.4 (left), 46 (right) and 95.7 (left), 89.65 (right), respectively.Clinical discussionDetailed preoperative evaluation of the anatomy was paramount. Assessment of the limb-length discrepancy by means of scanogram, templating the anatomy with computed tomography and planning the anatomical location of the centre of the relocated hip were mandatory.ConclusionBilateral total hip arthroplasty is a feasible option to manage the rare occurrence of severely damaged bilateral hip joints caused by TSA presenting in adulthood. Reconstructive options for late sequelae should be individualized based on the degree of involvement, hip stability, and patient expectations.

Influence of surface topography on junction strength of modular hip endoprostheses

The improved adaption of a modular hip endoprosthesis to patient-specific anatomy by means of a neck adapter is accompanied by the risk of a higher revision rate. This is due to micromotions leading to friction wear and corrosion of the additional taper interface. This results in the need to manufacture a load-adapted interface of modular hip endoprostheses. In this study, the influence of the machining processes turning and deep rolling on the surface topography of outer tapers of TiAl6V4 ELI and CoCrMo28 was investigated. In order to gain knowledge about the junction strength in dependence of the surface topography, tapers were joined and the separation force was investigated during push out tests. Results indicate that the adjustment of surface topographies of the outer taper is associated with a higher reproducibility in deep rolling than in turning. In addition, for the turning process inner tapers have a higher scattering of the investigated roughness parameters of the surface topography than the outer tapers. For the investigated taper angle of 5.665°, the influence of the surface topography on the separation forces is not significant. However, there is a little scatter of the taper angles of the samples depending on the machining process which leads to a difference between the inner and outer taper angle. This could significantly reduce the contact area of the junction and could be an explanation for the lack of significance of the separation forces we observed. Furthermore, no significant dependence of the separation forces on material properties was observed.

Influence of the taper on the fretting wear of the femoral stem-femoral head taper junction in total hip prosthesis

PurposeThe purpose of this paper is to study the roughness effect on the fixation of taper junction components and surfaces wear in terms of taper surface design. The roughness of the femoral heads’ taper and of the femoral stems’ trunnions can influence the fretting wear of the taper junction.Design/methodology/approachIt was analysed whether a microgrooved taper surface of the femoral stem trunnion improves the fixation and reduces the wear rate at the taper junction of the hip prosthesis. Two models have studied: a femoral head with a smooth tapered surface combined with a microgrooved stem trunnion and a femoral head with a smooth tapered surface combined with a trunnion that had a smooth surface of the tapered. To compare the wear evolution between these two models, a computerised finite element model of the wear was used.FindingsThe results obtained after analysis carried out during millions of loading cycles showed that the depth of the linear wear and the total material loss were higher for the femoral heads joined with microgrooved trunnions. The main conclusion of this paper is that the smooth surfaces of the taper and of the trunnions will ensure a better fixation at the taper junction, and therefore, will reduce the volumetric wear rates.Originality/valueA higher fixation of the taper junction will reduce the total hip prosthesis failure and, finally, it will improve the quality and durability of modular hip prostheses.

Assessment of physical, chemical, and tribochemical properties of biomedical alloys used in explanted modular hip prostheses.

During their service life, modular interfaces experience tribological, and corrosion phenomena that lead to deterioration, which in turn can cause a revision procedure to remove the failed prosthesis. To achieve a clearer understanding of the surface performance of those biomedical alloys and the role of the surface properties in the mechanical and chemical performance, samples were taken from retrieval implants made of Ti6Al4V and Co28Cr6Mo alloys. Polarization resistance and pin-on-disk tests were performed on these samples. Physical properties such as contact angle, roughness, microhardness, and Young's modulus were determined. A correlation between surface energy and evolution of the tribological contact was observed for both biomedical alloys. In tribocorrosion tests, titanium particles seem to remain in the surface, unlike what is observed in CoCr alloys. These metallic or oxidized particles could cause necrosis or adverse tissue reactions.