Metal release and corrosion effects of modular neck total hip arthroplasty

Effects of Shot Peening and Electropolishing Treatment on the Properties of Additively and Conventionally Manufactured Ti6Al4V Alloy: A Review

This literature review indicates that the basic microstructure of Ti6Al4V is bimodal, consisting of two phases, namely α + β, and it occurs after fabrication using conventional methods such as casting, plastic forming or machining processes. The fabrication of components via an additive manufacturing process significantly changes the microstructure and properties of Ti6Al4V. Due to the rapid heat exchange during heat treatment, the bimodal microstructure transforms into a lamellar microstructure, which consists of two phases: α' + β. Despite the application of optimum printing parameters, 3D printed products exhibit typical surface defects and discontinuities, and in turn, surface finishing using shot peening is recommended. A literature review signalizes that shot peening and electropolishing processes positively impact the corrosion behavior, the mechanical properties and the condition of the surface layer of conventionally manufactured titanium alloy. On the other hand, there is a lack of studies combining shot peening and electropolishing in one hybrid process for additively manufactured titanium alloys, which could synthesize the benefits of both processes. Therefore, this review paper clarifies the effects of shot peening and electropolishing treatment on the properties of both additively and conventionally manufactured Ti6Al4V alloys and shows the effect process on the microstructure and properties of Ti6Al4V titanium alloy.

Usefulness of modular neck adapter in partial hip revision

Background and Objective

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.

Methods

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.

Key Content and Findings

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.

Conclusions

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.

Clinical outcome of Bioball universal adapter in revision hip arthroplasty

Background

Removal of a well-fixed uncemented femoral component in revision hip arthroplasty is challenging. A modular head-neck adapter provides an option to optimise the femoral offset and anteversion, avoiding the need for femoral stem revision.

Aim

To present the clinical results following revision arthroplasty with the Bioball head-neck adapter in the elderly American Society of Anaesthesiologists (ASA) Grade II, III & IV patients.

Materials and methods

A retrospective review of our database was performed, and all patients classed as ASA grades II, III, & IV treated with the Bioball Universal Adapter (BUA) for 10 years were included. The indication for revision, stem retention, type of adapter, and head size were identified. Patients were contacted by a research nurse to assess the Forgotten Joint Score (FJS), the Oxford Hip Score (OHS), and any symptoms of instability at a minimum of one year post revision surgery.

Results

Our study included 47 patients. 5 (10.6%) were ASA II, 19 (40.4%) were ASA III and 23 (49%) were ASA IV. The mean age was 74 years. The mean follow up was 52 months ± 28.4 SD. The median FJS was 86 ± 11.6 SD. The median OHS was 43 ± 6.2 SD. One patient (2.1%) developed recurrent dislocation following lumbar spinal fusion. None of the other patients experienced instability. The survival rate for the adapter was 98%.

Conclusion

The BUA gives good clinical outcomes with very low post revision instability. It is a valuable option for the elderly because it avoids the morbidity and risks associated with the removal of a well-fixed femoral stem.

Level of Evidence

Level IV.

Satisfactory clinical and radiologic outcomes with a new shorter and modular stem for end-stage hip osteoarthritis: an international prospective multicentre pilot study

Introduction: This multicenter prospective cohort study aimed to assess the safety and clinical and radiologic performance of the CLS® BreviusTM Stem with Kinectiv® Technology. Material and Methods: A total of 222 consecutive subjects, recruited in five different centers, qualifying for primary total hip arthroplasty (THA), were enrolled in the study. All the subjects received the CLS® BreviusTM Stem with Kinectiv® Technology. All the enrolled study subjects underwent pre-operative clinical and radiographic evaluation. Additionally, all subjects underwent post-operative clinical, functional and radiographic evaluations at 6 months and 1, 2, 3, and 5 years. These evaluations included implant survival, pain and functional performance (Harris Hip Score [HHS], University of California, Los Angeles [UCLA] Activity Score, Oxford Hip Score), subject quality-of-life (EQ-5D), radiographic parameters, complications, and concentration of metal ions (aluminum and titanium) in blood. Results: No revisions were performed during the follow-up period. Of the 222 patients, only 76 completed the 5-year follow-up. Only 7 and 5 patients had aluminum and titanium 5-year evaluations, respectively. All the clinical parameters showed an overall improvement in the overtime measured with ANOVA for repeated measures; furthermore, the clinical scores showed a statistically significant improvement at 5 years with respect to pre-operative value (p < 0.001). Aluminum and titanium showed no variation for repeated measures at different time points (p > 0.05). A total of six complications were reported, of which only two were hip-related. Conclusions: The function of the CLS® BreviusTM Stem with Kinectiv® Technology indicated that subject well-being significantly increased following THA regardless of age, gender, BMI, previous surgery, primary diagnosis, and lifestyle.

Osteolysis in total hip arthroplasty in relation to metal ion release: Comparison between monolithic prostheses and different modularities

BACKGROUND

Among the various complications associated with total hip arthroplasty (THA) periprosthetic osteolysis and wear phenomena due to the release of metal particles, are two of the most common and have been reported to be correlated because of inflammatory responses directed towards released particles that generally activate macrophagic osteolytic effects. Therein, new masses known as pseudotumors can appear in soft tissues around a prosthetic implant. To date, there is paucity of reliable data from studies investigating for any association between the above mentioned adverse events.

AIM

To investigate for the existence of any association between serum and urine concentrations of metal-ions released in THA and periprosthetic osteolysis for modular neck and monolithic implants.

METHODS

Overall, 76 patients were divided into three groups according to the type of hip prosthesis implants: Monoblock, modular with metal head and modular with ceramic head. With an average f-up of 4 years, we conducted a radiological evaluation in order to detect any area of osteolysis around the prosthesis of both the femur and the acetabulum. Moreover, serum and urinary tests were performed to assess the values of Chromium and Cobalt released. Statistical analysis was performed to determine any association between the ion release and osteolysis.

RESULTS

For the 3 study groups, the monolithic, modular ceramic-headed and modular metal-headed implants had different incidences of osteolysis events, which were higher for the modular implants. Furthermore, the most serious of these (grade 3) were detected almost exclusively for the modular implants with metal heads. A mapping of the affected areas was performed revealing that the highest incidences of osteolysis were evidenced in the pertrochanteric region at the femur level, and in the supero-external region at the acetabular level. Regarding the evaluation of the release of metals-ions from wear processes, serum and urinary chromium and cobalt values were found to be higher in cases of modularity, and even more so for those with metal head. Statistical linear correlation test results suggested positive correlations between increasing metal concentrations and incidences areas of osteolysis. However, no cases of pseudo-tumor were detected.

CONCLUSION

Future studies are needed to identify risk factors that increase peri-prosthetic metal ion levels and whether these factors might be implicated in the triggering of local events, including osteolysis and aseptic loosening.

Interfacial compliance, energy dissipation, frequency effects, and long-term fretting corrosion performance of Ti-6Al-4V/CoCrMo interfaces

Fretting corrosion in modular orthopedic implants is a well-documented process that may be associated with adverse local tissue reactions, pain, and revisions. Engineering modular junction interfaces to withstand applied fretting motion without surface abrasion could prevent implant degradation and surface damage. Previous work on geometrically modified Ti-6Al-4V/CoCrMo interfaces with increased compliance showed reduced fretting currents and surface damage during short term, variable-load in vitro testing. This study assesses the same interfaces under long-term conditions using an in vitro pin-on-disk fretting corrosion test apparatus. Preliminary variable-load frequency testing of typical control pin geometries showed a frequency-dependent current response, with underlying contact conditions of metal-metal interfaces that remained unchanged. One-million-cycle testing showed diminished fretting currents in all groups by 5 × 10⁵  cycles, but consistently lower currents in the high-compliance group. Corresponding fretting currents and work of fretting measurements of high-compliance pins confirmed that minimal fretting was experienced at the interface, with elastic bending of the pin accounting for almost all applied displacement. Debris generated during testing were composed of titanium and chromium oxides, small amounts of cobalt and molybdenum oxides, and sodium and phosphate originating from the surrounding test solution. Post-test analyses of sample surfaces revealed substantially more surface damage on CoCrMo disks than Ti-6Al-4V pins, thought to be a result of adhesive wear of mixed oxide debris on the pin and abrasion of the disk by the oxide debris layer. Surface damage to high-compliance pins suggests some abrasion is unavoidable with geometric modifications.

Prospective clinical study using radiostereometric analysis (RSA) to evaluate fixation of a modular cemented polished femoral stem

BACKGROUND

The long-term clinical success of cemented polished tapered femoral components has been demonstrated in prospective as well as registry studies. This stem design type has also been well studied with radiostereometric analysis (RSA) and provides a standard to evaluate alternative designs of polished tapered cemented femoral components. This prospective study evaluates the subsidence of a polished cemented stem with a modular neck design utilising RSA.

METHODS

26 patients were prospectively enrolled in the study and 23 were available for RSA analysis at 2 years.

RESULTS

The average subsidence of the femoral implant was 1.1 mm (SD 0.4 mm) at 2 years post operation. There were no revisions in this group, specifically no failures of the modular stem-neck design as has been seen with other implants.

CONCLUSIONS

The RSA subsidence pattern at 2 years of this cemented femoral stem is similar to other successful designs with long-term follow-up. The implications over time of stem neck modularity for cemented polished tapered femoral components requires further evaluation.

Does modularity of metal-on-metal hip implants increase cobalt: chromium ratio?

BACKGROUND

Blood metal ion levels are used in the surveillance of metal-on-metal (MoM) hip implants. Modular implants contain an extra source of metal debris that may affect the ratio of metal ions in the blood.

METHODS

This was a retrospective study of 503 patients with hip replacements made by a single manufacturer (Smith & Nephew, Warwick, UK) with the same bearing surface. There were 54 total hip arthroplasties, 35 Birmingham Mid-Head Resections and 414 hip resurfacings. Whole blood metal ion levels and their ratios were analysed to investigate the effect of a modular junction.

RESULTS

The cobalt:chromium ratios were greater in the total hip arthroplasty group (mean 2.3:1) when compared to the resurfacings group (mean 1.3:1, p = <0.05) and Birmingham Mid-Head Resection group (mean 1.1:1, p = 0.11).

CONCLUSIONS

This study demonstrated a trend for a higher cobalt:chromium ratio in patients with MoM total hip replacement that may be due to metal debris from the modular stem-head junction. Further work is required to correlate clinical data with retrieval analysis to confirm the effect of taper material loss on the cobalt:chromium ratio.

Clinical outcomes and dislocation rates after hip reconstruction using the Bioball system

INTRODUCTION

Instability accounts for 1/3 of revision total hip arthroplasty (rTHA) performed in the UK. Removal of well-fixed femoral stems in rTHA is challenging with a risk of blood loss and iatrogenic damage to the femur. The Bioball universal adaptor (BUA), a modular head neck extension adaptor, provides a mechanism for optimisation of femoral offset, leg length and femoral anteversion. This can avoid the need for femoral stem revision in selected cases.The aim of this study is to present the clinical results and rate of instability following revision with this BUA at a minimum of 2 years follow-up.

PATIENTS AND METHODS

A review of our prospectively collected database was performed. All patients treated with the Bioball device were included. Clinical and radiologic review were performed pre- and post-surgery. Specific enquiry for instability was made. The Oxford Hip Score (OHS), EuroQol (EQ-5D) score and WOMAC scores were calculated pre-and post-operatively. Complications were recorded.

RESULTS

32 rTHA procedures were performed using the Bioball device between 2013 and 2016. 4 patients did not wish to complete post-operative questionnaires. 2 patients (2/28, 7%) complained of recurrent dislocations following their rTHA procedure. 1 patient complained of instability but no dislocation. The median pre-operative EQ-5D was 0.195 (range -0.07-0.85), OHS was 20 (range 5-43) and WOMAC was 29.8 (range 15.5-52.3). The median EQ-5D was 0.85 (range 0.59-1), OHS was 39 (range 21-48) and WOMAC was 91.1 (range 44.5-99.2) at final follow-up. There were significant improvements in the EQ-5D (p = 0.0009), OHS (p = 0.0004) and WOMAC (p = 0.0001).

CONCLUSION

The BUA is associated with significant functional improvement and relatively low dislocation rates in revision THA. It is a viable option for use in the revision setting.

How to proceed with asymptomatic modular dual taper hip stems in the case of acetabular revision

How to proceed with a clinically asymptomatic modular Metha® Ti alloy stem with dual taper CoCr neck adapter in case of acetabular revision? To systematically answer this question the status of research and appropriate diagnostic methods in context to clinically symptomatic and asymptomatic dual taper stem-neck couplings has been evaluated based on a systematic literature review. A retrieval analysis of thirteen Metha® modular dual taper CoCr/Ti alloy hip stems has been performed and a rational decision making model as basis for a clinical recommendation was developed. From our observations we propose that in cases of acetabular revision, that for patients with a serum cobalt level of > 4 µg/L and a Co/Cr ratio > 3.6, the revision of the modular dual taper stem may be considered. Prior to acetabular revision surgery a systematic diagnostic evaluation should be executed, using specific tests such as serum metal (Co, Cr) ion analysis, plain antero-posterior and lateral radiographs and cross-sectional imaging modalities (Metal Artefact Reduction Sequence Magnetic Resonance Imaging). For an asymptomatic Metha® dual taper Ti alloy/CoCr stem-neck coupling at the stage of acetabular revision careful clinical decision making according to the proposed model should be followed and overreliance on any single examination should be avoided, considering the complete individual differential diagnosis and patient situation.

The Merete BioBall system in hip revision surgery: A systematic review

BACKGROUND

Modular hip arthroplasty is widely recognized in hip surgery; nevertheless, despite advances in prosthetic design, the incidence of hip revision surgery is increasing. In these procedures, a modular adapter that engages the femoral stem and the modular femoral head could be useful in order to protect the neck-head junction and restore preoperative biomechanics and soft tissue tension when the femoral or acetabular component should be retained. The Merete™ BioBall™ system (Merete Medical, Berlin, Germany) could fill this need. However the literature regarding this device is sparse, therefore we performed a systematic review to analyze: the indications for its use and clinical results and the causes of second revision and survival in hip revision surgery, mainly focus in complications of its use.

MATERIALS AND METHODS

Databases including PubMed and Google Scholar were searched for English-language articles published between 01/01/1999 and 01/04/2017, using search terms related to the system Merete™ BioBall™. Studies that reported the clinical use of the Merete™ BioBall™ system in hip revision surgery were selected. Data related to the indications, characteristics of the implant, clinical results, causes of second revision and survival were gathered.

RESULTS

A total of 14 studies with a level IV evidence were analyzed. Information related to the implant was provided in 194 cases. Isolated acetabular revision was the main indication of implant use (139/194 [71.6%]). The most common combination used was the standard implant (69/110 specified [59.4%]), 3XL length (28/107 specified [26.2%]) with 32mm metal head (58/187 specified [31%]). After a follow-up ranging from 2 to 97 months, there were 16 complications, thirteen (81,2%) were revised, including one neck fracture of the stem (6.25%), two ceramic head fractures (12,5%) and six recurrent dislocations (37,5%). Implant survival was 92.8% at 52.5 months of follow-up in the longest published series. Clinical and functional results were provided in a heterogeneous way.

CONCLUSIONS

There is insufficient evidence to recommend for or contraindicate the use of the Merete™ BioBall™ system. The Isolated acetabular revision was the main indication of implant use. When dislocation is the indication of its use the rate of second revision is high. Some important complications possibly related with the implant design have been reported but as isolated cases. The neck adapter failure or corrosion phenomena have not been reported. Further prospective and controlled trials are needed to assess the use of this type of implant and its survival.

LEVEL OF EVIDENCE

Level III systematic review of case series.

Novel concept of a modular hip implant could contribute to less implant failure in THA: a hypothesis

Background

The modularity in total hip arthroplasty (THA) allows orthopaedic surgeons for an exact reconstruction of hip biomechanical parameters especially in revision and tumor arthroplasty. Modular structured femoral stems using taper junctions showed increased implant breakage in the recent past.

Presentation of the hypothesis

We hypothesize that a novel modular stem-neck-interface leads to less implant breakage compared to conventional femoral stems.

Testing of the hypothesis

For this purpose, a novel modular femoral stem for THA was to design and manufacture. Therefore, three different variants of interface mechanisms were developed that enable a simple connection between the stem and the neck modules and allow for intra-operatively adjustment. Three prototypes A, B and C were manufactured and subsequently dynamic fatigue (ISO 7206–6) and body donor tested.

Implication of the hypothesis

Modularity in THA is mainly applied in THA as well as in revision and tumor arthroplasty. Modular implants are barely used because of the high risk of breakage. Another risks in this context are taper fretting, corrosion and disconnection. With the novel design, it should be possible to detach the stem and neck module intra-operatively to adapt the anatomical situation. The novel coupling mechanism of the rotating interface seems to be the most suitable for a secure stem-neck connection and is characterized by good intraoperative handling.

Modularity in Total Hip Arthroplasty: Benefits, Risks, Mechanisms, Diagnosis, and Management

Modular implants are currently widely used in total hip arthroplasty because they give surgeons versatility during the operation, allow for easier revision surgery, and can be adjusted to better fit the anatomy of the specific patient. However, modular implants, specifically those that have metal-on-metal junctions, are susceptible to crevice and fretting corrosion. This can ultimately cause implant failure, inflammation, and adverse local tissue reaction, among other possible side effects. Surgeons should be aware of the possibility of implant corrosion and should follow a set of recommended guidelines to systematically diagnose and treat patients with corroded implants. Ultimately, surgeons will continue to use modular implants because of their widespread benefits. However, more research is needed to determine how to minimize corrosion and the negative side effects that have been associated with modular junctions in total hip arthroplasty. [Orthopedics. 2017; 40(6):355-366.].

Cementless modular neck stems: are they a safe option in primary total hip arthroplasty?

PURPOSE

The objective was to assess aseptic complications and functional outcome using a primary total hip arthroplasty with modular neck.

METHODS

Prospective cohort of 317 consecutive patients. The mean age was 61.1 (range, 41-84) years. The H-Max-M model (Lima, Italy) system was used in all patients. The functional assessment was made by the Harris Hip Score, Short Form-36 (SF-36), Western Ontario and McMaster Universities Osteoarthritis Index and visual analogue scale for pain. Radiological outcomes were also assessed, and adverse events and complications were noted.

RESULTS

The mean follow-up was 6.1 (range, 2-8) years. Functional outcome significantly improved in most patients. There were 3 deep infections (0.9%) and 17 aseptic complications (5.3%) including 1 intraoperative acetabular fracture, 3 later periprosthetic femoral fractures, 1 broken ceramic insert, 1 acetabular loosening, 3 femoral loosening and 1 broken titanium modular neck in a obese patient. No pseudotumors or elevated serum levels of metal ions were found among the patients with radiolucent lines or aseptic loosening.

CONCLUSIONS

The findings in the present study showed that the H-MAX-M stem provided satisfactory functional outcome in most patients with a low rate of complications attributable to the modular neck design. We consider that using this novel modular neck-stem coupling design can be an alternative to the conventional monoblock stems in patients without overweight.

The Chemical Form of Metal Species Released from Corroded Taper Junctions of Hip Implants: Synchrotron Analysis of Patient Tissue

The mechanisms of metal release from the articulation at the head cup bearing and the tapered junctions of orthopaedic hip implants are known to differ and the debris generated varies in size, shape and volume. Significantly less metal is lost from the taper junction between Cobalt-Chromium-Molybdenum (CoCrMo) and Titanium (Ti) components (fretting-corrosion dominant mechanism), when compared to the CoCrMo bearing surfaces (wear-corrosion dominant mechanism). Corrosion particles from the taper junction can lead to Adverse Reactions to Metal Debris (ARMD) similar to those seen with CoCrMo bearings. We used synchrotron methods to understand the modes underlying clinically significant tissue reactions to Co, Cr and Ti by analysing viable peri-prosthetic tissue. Cr was present as Cr₂O₃ in the corroded group in addition to CrPO₄ found in the metal-on-metal (MoM) group. Interestingly, Ti was present as TiO₂ in an amorphous rather than rutile or anatase physical form. The metal species were co-localized in the same micron-scale particles as result of corrosion processes and in one cell type, the phagocytes. This work gives new insights into the degradation products from metal devices as well as guidance for toxicological studies in humans.

Fretting and Corrosion Between a Metal Shell and Metal Liner May Explain the High Rate of Failure of R3 Modular Metal-on-Metal Hips

BACKGROUND

The R3 acetabular system used with its metal liner has higher revision rates when compared to its ceramic and polyethylene liner. In June 2012, the medical and healthcare products regulatory agency issued an alert regarding the metal liner of the R3 acetabular system.

METHODS

Six retrieved R3 acetabular systems with metal liners underwent detailed visual analysis using macroscopic and microscopic techniques.

RESULTS

Visual analysis discovered corrosion on the backside of the metal liners. There was a distinct border to the areas of corrosion that conformed to antirotation tab insertions on the inner surface of the acetabular shell, which are for the polyethylene liner. Scanning electron microscopy indicated evidence of crevice corrosion, and energy-dispersive X-ray analysis confirmed corrosion debris rich in titanium.

CONCLUSION

The high failure rate of the metal liner option of the R3 acetabular system may be attributed to corrosion on the backside of the liner which appear to result from geometry and design characteristics of the acetabular shell.

Sensitivity and Specificity of Metal Ion Levels in Predicting "Pseudotumors" due to Taper Corrosion in Patients With Dual Taper Modular Total Hip Arthroplasty

BACKGROUND

Currently, no serum metal ion threshold exists to identify adverse tissue reactions in total hip arthroplasty (THA) patients with taper corrosion. Our study aims to investigate the sensitivity and specificity of serum metal ions in detecting taper corrosion related pseudotumors in patients with dual taper modular THA.

METHODS

A total of 148 patients with dual taper modular THA were investigated: (1) 90 patients with pseudotumors detected with metal artifact reduction sequence-magnetic resonance imaging (MARS-MRI) and (2) 58 patients without pseudotumors on MARS-MRI. Receiver operating characteristic curves were constructed to determine the sensitivity and specificity using different metal ion thresholds. The severity of intraoperative tissue damage was correlated with preoperative metal ion levels.

RESULTS

Pseudotumor was associated with higher cobalt (5.0 μg/L vs 3.7 μg/L, P < .01) and Co/Cr ratio (6.0 vs 3.7, P < .01). The sensitivity and specificity for cobalt level of 2.8 μg/L and Co/Cr ratio of 3.8 in detecting taper corrosion-related pseudotumors on MARS-MRI was 88% and 32% and 70% and 50%, respectively. Higher intraoperative tissue damage grades demonstrated significantly higher Co/Cr ratios (8.6 vs 3.4, P = .03).

CONCLUSION

Although metal ion levels alone should not be relied on as the sole parameter to determine revision surgery, cobalt level >2.8 μg/L and the Co/Cr ratio >3.8 are useful clinical diagnostic adjuncts in the systematic clinical evaluation for taper corrosion-related adverse tissue reactions in patients with dual modular taper THA.

Metal-on-metal total hip arthroplasty: risk factors for pseudotumours and clinical systematic evaluation

The potential advantages of contemporary MoM THA implants include less volumetric wear with subsequent reduction of polyethylene wear-induced osteolysis and greater component stability with use of large-diameter femoral heads. However, there have been concerns regarding significantly elevated revision rates in MoM THA due to MoM-related complications such as adverse local tissue reaction (pseudotumour) formation. The increased failure rate in MoM hip arthroplasty is associated with the generation of biologically active, nanometer sized metal particles from the MoM bearing surfaces and taper junctions, which result in the development of a localized, adverse periprosthetic soft tissue response. The focus of this article is to provide an update on (1) implant, surgical and patient factors associated with adverse local tissue reactions (pseudotumours) and (2) the clinical systematic evaluation and management of patients with MoM hip arthroplasty based on the currently available evidence. There should be a low threshold to conduct a systematic clinical evaluation of patients with MoM hip arthroplasty as early recognition and diagnosis will allow the initiation of prompt and appropriate treatment. As a symptomatic MoM total hip arthroplasty may have intrinsic and extrinsic causes, patients should be evaluated systematically, utilizing risk stratification algorithms. Although specialized laboratory tests such as metal ion levels and cross sectional imaging modalities such as MARS MRI can be used to facilitate clinical decision making, over-reliance on any single investigative tool in the clinical decision-making process should be avoided. Further research is required to obtain a better understanding of implant and patient risk factors associated with tribocorrosion in MoM total hip arthroplasty.

Magnetic Resonance Imaging Predicts Adverse Local Tissue Reaction Histologic Severity in Modular Neck Total Hip Arthroplasty

BACKGROUND

The association between advanced imaging, serum metal ion levels, and histologic adverse local tissue reaction (ALTR) severity has not been previously reported for Rejuvenate modular neck femoral stems.

METHODS

A cohort of 90 patients with 98 Rejuvenate modular neck femoral stems was revised by a single surgeon from July 2011 to December 2014. Before revision, patients underwent multiacquisition variable resonance image combination sequence magnetic resonance imaging (MRI), and serum cobalt and chromium ion levels were measured. Histologic samples from the revision surgery were scored for synovial lining, inflammatory infiltrate, and tissue organization as proposed by Campbell. Regression based on the generalized estimating equations approach was used to assess the univariate association between each MRI, demographic, and metal ion measure and ALTR severity while accounting for the correlation between bilateral hips. Random forest analysis was then used to determine the relative importance of MRI characteristics, demographics, and metal ion levels in predicting ALTR severity.

RESULTS

Synovial thickness as measured on MRI was found to be the strongest predictor of ALTR histologic severity in a recalled modular neck femoral stem.

CONCLUSION

MRI can accurately describe ALTR in modular femoral neck total hip arthroplasty. MRI characteristics, particularly maximal synovial thickness and synovitis volume, predicted histologic severity. Serum metal ion levels do not correlate with histologic severity in Rejuvenate modular neck total hip arthroplasty.

Serologic and radiographic outcome of total hip arthroplasty with CoCr modular neck at mid-term follow-up

PURPOSE

The aim of this study is a radiographic evaluation and to determine serologic values of chromium and cobalt in the blood and urine of patients who have been implanted with a Stryker^® ABG II Modular Neck and see if there is correlation with the features of prosthesis and patients.

METHODS

The study involves the collection of data from patients operated on for total hip model with the ABG II Modular Neck with a minimum follow-up of 1 year.

RESULTS

We evaluated 22 patients who underwent implantation of a hip prosthesis with modular neck in CoCr. Of these, the average Cr in the blood was 0.63 μgL^-1 (range 0.1-2.15 μgL^-1), the average of Co in the blood was 3.50 μgL^-1 (range 0.62-7.78 μgL^-1), the average Cr in the urine was 1.24 μgL^-1 (range 0.48-2.21 μgL^-1), and the average Co in urine was 14.22 μgL^-1 (range 3.3-31.2 μgL^-1). None of these patients had undergone revision surgery.

CONCLUSIONS

Our study seems to indicate that the restoration of offset and age are correlated with the release of metal ions, although the correlation is weak and needs better methodological studies and a greater number of patients to confirm this hypothesis.

STUDY TYPE

Case series Level of Evidence 4.

Clinical outcome of design modifications to the CLS Spotorno Stem in total hip replacement

PURPOSE

historically, the original CLS Spotorno Stem has demonstrated excellent survival. The design of this stem was recently modified, resulting in the introduction of a shorter, modular version (CLS Brevius). The purpose of the current study was to evaluate the functional, radiological and survivorship outcomes of the cementless CLS Brevius Stem in a multi-surgeon, single center, consecutive series study at two years post-surgery.

METHODS

the Authors performed 170 total hip arthroplasties in 155 patients using the shorter, triple-taper stem design (CLS Brevius). The patients' diagnoses were primary hip osteoarthritis (OA) in 74.4%, secondary hip OA in 22.6%, and post-traumatic hip OA in 3%. All operations were performed through a mini-posterior approach, with the patient in the lateral decubitus position. The mean follow-up was 32 months (24-44 months). Outcome was assessed using the Harris Hip Score (HHS).

RESULTS

the mean HHS improved from 32 preoperatively to 92 points at final follow-up, while the stem survival rate was 99.4%. Overall, the results were excellent in148 hips (87%), good in 14 hips (8.2%), fair in six hips (3.6%), and poor in two hips (1.2%). Intraoperative complications included a calcar fissure in three hips (1.7%). Correct femoral offset was reproduced in 97% while the planned center of hip rotation was achieved in 98%. Only one hip underwent early stem revision; this was due to major subsidence.

CONCLUSIONS

the modified CLS stem design showed excellent short-term results with a low rate of early postoperative complications. One of the main findings of this study was the high correlation between the planned femoral offset and center of hip rotation and the final radiographic measurements. This high reproducibility, which indicates the ability of the system to restore normal hip anatomy, is indeed due to the extensive modularity that characterizes this stem system. Long-term follow-up studies are necessary to fully compare the outcomes of the new design with its highly successful predecessor.

LEVEL OF EVIDENCE

Level IV, therapeutic cases series.

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.

The biological response to orthopaedic implants for joint replacement: Part I: Metals

Joint replacement is a commonly performed, highly successful orthopaedic procedure, for which surgeons have a large choice of different materials and implant designs. The materials used for joint replacement must be both biologically acceptable to minimize adverse local tissue reactions, and robust enough to support weight bearing during common activities of daily living. Modern joint replacements are made from metals and their alloys, polymers, ceramics, and composites. This review focuses on the biological response to the different biomaterials used for joint replacement. In general, modern materials for joint replacement are well tolerated by the body as long as they are in bulk (rather than in particulate or ionic) form, are mechanically stable and noninfected. If the latter conditions are not met, the prosthesis will be associated with an acute/chronic inflammatory reaction, peri-prosthetic osteolysis, loosening and failure. This article (Part 1 of 2) is dedicated to the use of metallic devices in orthopaedic surgery including the associated biological response to metallic byproducts is a review of the basic science literature regarding this topic. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2162-2173, 2017.

Eighty-six Percent Failure Rate of a Modular-Neck Femoral Stem Design at 3 to 5 Years: Lessons Learned

BACKGROUND

While innovation drives advancement, it is not immune to failure. Previously, we reported a corrosion-related revision rate of 28% (23 of 81 total hip arthroplasties) among patients who received the Rejuvenate modular-neck stem implant with short-term follow-up. Because we observed a dramatic interval failure rate after our initial report, we undertook this study.

METHODS

We prospectively followed a cohort of patients who had undergone implantation of the Rejuvenate modular-neck stem, as previously reported. At a minimum of 3 years of follow-up (range, 3.0 to 5.5 years), 73 hips in 63 patients (90% of the original group) were available for analysis. The mean serum cobalt and chromium ion levels were obtained preoperatively and postoperatively. Elevated serum cobalt ion levels (>4 μg/L), pain, or abnormal magnetic resonance imaging (MRI) findings were indications for revision surgery. Patient factors and serum metal ion levels were correlated to revision surgery. Additionally, post-revision serum cobalt and chromium ion level trends were assessed.

RESULTS

An 86% clinical failure rate (63 of the 73 hips) was observed at a mean follow-up of 4.2 ± 0.6 years (range, 3.0 to 5.5 years); 57 (78%) of the hips underwent revision at a mean of 3.2 ± 1.0 years (range, 1.0 to 5.5 years), and 6 (8%) of the hips were scheduled for revision. Patients who underwent revision surgery were younger and had greater serum metal ion levels and greater pain compared with patients who did not undergo revision. An elevated serum cobalt ion level was the most important independent factor associated with revision surgery. Cobalt ion levels decreased sharply after revision; however, some patients demonstrated persistent elevation with more gradual decline.

CONCLUSIONS

Emphasizing the reporting of positive results may leave orthopaedic surgeons reticent to publicize negative results; however, the high failure rate of this implant design within 5 years prompted this report. We believe that patients and orthopaedic surgeons should be made aware of this implant's clinical problems and patients should be followed closely. Expedient revision is necessary when failure is identified, to minimize potentially severe tissue damage and metal toxicity.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Short-Term Outcomes and Complications After Rejuvenate Modular Total Hip Arthroplasty Revision

BACKGROUND

The early short-term outcomes and complications after revision of the recalled Rejuvenate modular neck hip arthroplasty have not been previously reported. This study's purpose is to describe the early outcomes and complications after revision of the Rejuvenate modular femoral neck.

METHODS

A retrospective cohort included 92 patients with 92 Rejuvenate modular neck total hip arthroplasty (THA) who underwent revision surgery between July 2011 and April 2014. Preoperative, 1-year, and 2-year patient-reported outcome measures including Western Ontario and McMaster Universities Arthritis Index (WOMAC) and Short Form 12 (SF-12) were described in 92 patients.

RESULTS

Complications arose in (12 of 92) 13% of patients including 8 greater trochanteric fractures, 1 intraoperative periprosthetic acetabular fracture, 2 dislocations, 1 early aseptic loosening, and 1 infection requiring a 2-stage revision. Overall, 66% of patients with a complication required reoperation. Significant changes were noted between preoperative and 1- and 2-year outcomes with respect to WOMAC pain score (P = .0031), WOMAC total score (P = .021), SF-12 mental component score (P < .0001), and physical component score (P < .0001).

CONCLUSIONS

Patients can expect an improvement in pain (WOMAC pain) and function (total WOMAC, SF-12 Physical Health Composite Scale), but overall worsening in the SF-12 mental component scores. Patients' physical function improvements are offset by worsened mental function scores. Patients undergoing revision of Rejuvenate modular neck THA implants should be counseled on modest functional improvements and relative frequency of complications.

Titanium: a review on exposure, release, penetration, allergy, epidemiology, and clinical reactivity

Exposure to titanium (Ti) from implants and from personal care products as nanoparticles (NPs) is common. This article reviews exposure sources, ion release, skin penetration, allergenic effects, and diagnostic possibilities. We conclude that human exposure to Ti mainly derives from dental and medical implants, personal care products, and foods. Despite being considered to be highly biocompatible relative to other metals, Ti is released in the presence of biological fluids and tissue, especially under certain circumstances, which seem to be more likely with regard to dental implants. Although most of the studies reviewed have important limitations, Ti seems not to penetrate a competent skin barrier, either as pure Ti, alloy, or as Ti oxide NPs. However, there are some indications of Ti penetration through the oral mucosa. We conclude that patch testing with the available Ti preparations for detection of type IV hypersensitivity is currently inadequate for Ti. Although several other methods for contact allergy detection have been suggested, including lymphocyte stimulation tests, none has yet been generally accepted, and the diagnosis of Ti allergy is therefore still based primarily on clinical evaluation. Reports on clinical allergy and adverse events have rarely been published. Whether this is because of unawareness of possible adverse reactions to this specific metal, difficulties in detection methods, or the metal actually being relatively safe to use, is still unresolved.

Stem Migration and Fretting Corrosion of the Antirotation Pin in the K2/Apex Hip System

BACKGROUND

Many exchangeable neck hip systems have been withdrawn because of fretting corrosion at the neck/stem coupling.

METHOD

Our prospective randomized study evaluating stem stability (Roentgen stereophotogrammetric analysis, dual-energy x-ray absorptiometry) and clinical outcomes between the K2/Apex hip systems was ceased early because of a withdrawal of the stems which had an unfavorably high early revision rate reported in the Australian Orthopaedic Association National Joint Registry (9.3% at 3 years).

RESULTS

At 2 years, there are no clinical differences between the stems. Roentgen stereophotogrammetric analysis has identified a high proportion of potentially concerning subsidence and retroversion in both groups, more marked in the K2 stem, although mostly in asymptomatic patients. Dual-energy x-ray absorptiometry has shown similar bone density around the stems. Retrieval analysis of 3 study patients showed fretting corrosion of the antirotation pin and aseptic lymphocyte-dominated vasculitis-associated lesion, with no relationship to bearing type or size. Analysis of 7 further nonstudy K2/Apex stems confirmed similar corrosion.

CONCLUSION

This study shows potentially concerning subsidence of both stems and is the first to describe corrosion at the neck-stem interface and a relationship to metal-related pathology.

Outcome of a modular head-neck adapter system in revision hip arthroplasty

PURPOSE

Revision hip arthroplasty using a modular head-neck adapter gives the possibility of keeping a well-fixed femoral component while revising the acetabular prosthesis or femoral head and adapt leg length and femoral offset to the individual anatomy intraoperatively. The success of this kind of surgery is still unclear due to the lack of medium- to long-term follow-up. Therefore, we analyzed the clinical and radiological outcome of the modular Merete BioBall© adapter system in revision hip surgery.

METHODS

In this retrospective study, we included 95 consecutive patients with a Merete BioBall© adapter system implanted during revision hip arthroplasty. The average follow-up was 52.5 months. For clinical evaluation, we used the Harris Hip Score. The health-related quality of life was determined with the visual analog pain scale.

RESULTS

The surgeries were performed 97 months after prior hip arthroplasty on average. The main indications for the Merete BioBall© adapter system were dislocation, acetabular loosening, and wear. In the clinical outcome, patients achieved 80.9 points in the Harris Hip Score. The mean level of persisting pain was 1.4 (VAS). The overall survival of the Merete BioBall© system in revision hip arthroplasty revealed 92.8 % survival at 8.17 years follow-up with a repeat revision rate of 5.2 %.

CONCLUSIONS

Performing revision hip arthroplasty using the Merete BioBall

Serum Metal Ions with a Titanium Modular Neck Total Hip Replacement System

The goal of this study is to evaluate serum levels of chromium (Cr), cobalt (Co), and titanium (Ti) within the first two years following total hip arthroplasty using a Ti modular neck system. Twenty-five patients were randomized to a metal-on-metal (MoM) bearing with an all CoCr shell, and the remaining 25 received a metal-on-polyethylene (MoP) with a Ti shell. Serum levels demonstrated increases for Cr, Co, and Ti at 1 year (P < .001). MoM had similar Ti levels to MoP hips at 1 year (P=0.11) but lower at 2 years (P=0.03). Results suggest that the passive corrosion (i.e., chemical, pitting, and crevice corrosion) of exposed non-articular metal surfaces may be a greater source of ions than the neck-stem or head-neck interfaces.

Corrosion and Fretting of a Modular Hip System: A Retrieval Analysis of 60 Rejuvenate Stems

Femoral stems with dual-taper modularity were introduced to allow independent control of length, offset, and version. Corrosion and fretting related to micromotion at the neck-stem junction are thought to stimulate an adverse local tissue reaction (ALTR). Analysis of 60 consecutively retrieved modular-neck stem implants (Rejuvenate, Stryker) revised primarily for ALTR was done to determine the variables influencing corrosion and fretting patterns at the neck-stem interface. Taper damage evaluation was performed with stereomicrocopic analysis with two observers. Evidence of fretting and corrosion was seen at the neck-stem taper in all implants, including three implants revised for periprosthetic fractures within four weeks of the index surgery indicating that this process starts early. Femoral stems paired with the long overall neck lengths had significantly higher corrosion scores. Correlation of the corrosion severity at particular locations with the length of implantation suggests that the neck-stem junction experiences cyclic cantilever bending in vivo. The positive correlation between the length of implantation and fretting/corrosion scores bodes poorly for patients who still have this implant. Scanning electron microscopy on a subset of specimens was also performed to evaluate the black corrosion material. We strongly urge frequent follow-up exams for every patient with this particular modular hip stem.

Fracture of the Modular Neck in Total Hip Arthroplasty

Modularity of the components in total hip arthroplasty has had an increase in popularity in the last decades. We present the case of a 53-year-old man with a history of avascular necrosis of the femoral head due to a hypophyseal adenoma. A total hip modular arthroplasty was implanted. Three and a half years after the surgery the patient attended the emergency room due to acute left hip pain with no prior traumatism. Radiological examination confirmed a fracture of the modular neck. A revision surgery was performed finding an important pseudotumoral well-organized periprosthetic tissue reaction. Through an extended trochanteric osteotomy the femoral component was removed, and a straight-stem revision prosthesis implanted. There are several potential advantages when using modularity in total hip arthroplasty that surgeons may benefit from, but complications have arisen and must be addressed. Various circumstances such as large femoral head with a long varus neck, corrosion, patient's BMI, and activity level may participate in creating the necessary environment for fatigue failure of the implant.

Short-Term Metal Ion Trends Following Removal of Recalled Modular Neck Femoral Stems

Elevated serum metal ions have been well documented with the Rejuvenate modular neck femoral stem (Stryker, Mahwah, NJ); however, the rate at which ion levels decline following revision is less clear. This study included fifty-nine consecutive revisions of Rejuvenate stems for symptomatic ALTR. Blood tests prior to revision and postoperatively at 6weeks, 3months, 6months, and 1year measured serum cobalt and chromium concentrations, ESR, and CRP. At six weeks following revision of a unilateral Rejuvenate, cobalt and chromium levels dropped from preoperative levels by 67% and 42%, respectively. At three months, cobalt levels declined to 19% of preoperative values, but chromium levels remained stable. With this information, surgeons can set realistic expectations for serum metal ion levels following Rejuvenate stem revision.

Titanium-titanium modular neck for primary THA. Result of a prospective series of 170 cemented THA with a minimum follow-up of 5 years

BACKGROUND

Although they have been in use since the end of the 1980s, modular titanium neck components are associated with a risk of wear or fracture, and their safety has recently become a subject of debate and has never been evaluated in a consecutive series of patients. The goal of this study was to evaluate: revision-free survival of these implants after a minimum follow-up of 5 years; clinical and radiographic results; and the potential complications associated with the use of modular titanium neck components.

HYPOTHESIS

The use of titanium modular neck on cemented titanium THA is safe at a minimum follow-up of 5 years.

PATIENTS AND METHODS

Between January 2006 and December 2008, we prospectively followed 170 patients (170 hips) who underwent primary anatomical THA with a modular cemented titanium stem design implant. The indications were unilateral THA for primary (n=160) or secondary (n=10) hip osteoarthritis (aseptic osteonecrosis of the femoral head or hip dysplasia). Mean age of patients was 75.4±5.8 years old (52-85), and mean BMI was 26.1±4.5 kg/m(2) (16.6-42.1). Patients were operated on by a modified Watson-Jones anterolateral approach based on preoperative 2D planning. All patients underwent annual clinical and radiological follow-up by an independent observer.

RESULTS

At a mean follow-up of 71±8 months (60-84), 5 patients died and 7 were lost to follow-up. There was no revision of THA after a maximum follow-up of 84 months. The Harris score improved significantly from 50.4±11.3 (0-76) preoperatively to 84.5±15.2 (14-100) at the final follow-up. There was no difference in postoperative femoral offset or the position of the center of rotation compared to the opposite side. On the other hand, the neck-shaft angle (NSA) and limb length were corrected (2±5° [-11 to +14°] and 2.16±3.6 mm [-7.4 to +12.7 mm]) respectively. Fifteen patients (9%) had limb length discrepancies of more than 5 mm and 4 patients (2%) of more than 10 mm. There were no complications due to the modular implant design.

DISCUSSION

Our study suggests that the use of cemented titanium implants with a modular titanium stem is safe at a follow-up of 5 years. The modular design does not prevent limb length discrepancies but restores femoral offset.

LEVEL OF EVIDENCE

IV: prospective, non-comparative study.

Large fixed-size metal-on-metal total hip arthroplasty: higher serum metal ion levels in patients with pain

PURPOSE

Recently, concerns have arisen about metal-on-metal (MoM) total hip arthroplasty (THA). Therefore, the purpose of this cross-sectional cohort study was to describe the incidence of pain, pseudotumours, revisions and the relation between elevated metal ion levels, functional outcome and quality of life after MoM THA.

METHODS

In 351 patients, 377 MoM THA with a fixed-size 38-mm head were evaluated with a mean follow-up of 30 months (range 11-58). Evaluation included pain, serum metal ions, patient-reported questionnaires (Short Form-36 [SF-36], Hip disability and Osteoarthritis Outcome Score [HOOS] and the Oxford Hip Score [OHS]) and radiological imaging. Sixteen patients did not participate in the screening.

RESULTS

One hundred and eighteen (35 %) patients reported pain and showed significantly higher cobalt and chromium levels compared to patients without pain. Median serum cobalt levels were 4.4 μg/l (interquartile range [IQR] 6.6) and chromium levels were 3.6 μg/l (IQR 4.8). Patients with cobalt levels of ≤5 μg/l reported significantly better outcome on the SF-36 and HOOS. Fifty-seven pseudotumours were identified in 227 THAs. A revision rate of 19 % was observed.

CONCLUSIONS

In conclusion, 35 % of the patients experienced pain after MoM THA. These patients showed significantly higher serum metal ion levels. The patient-reported questionnaires indicated significantly better outcome in patients with cobalt levels ≤5 μg/l.

Risk stratification algorithm for management of patients with dual modular taper total hip arthroplasty: consensus statement of the American Association of Hip and Knee Surgeons, the American Academy of Orthopaedic Surgeons and the Hip Society

Although 'dual taper' modular stems with interchangeable modular necks have the potential to optimize hip biomechanical parameters, there is increasing concern regarding the occurrence of adverse local tissue reactions from mechanically assisted crevice corrosion at the neck-stem taper junction. A systematic treatment approach (risk stratification algorithm) based on the currently available data is recommended to optimize patient management. While specialized tests such as metal ion analysis and MARS MRI are useful modalities in evaluating for adverse tissue reactions, over-reliance on any single investigative tool in the clinical decision-making process should be avoided. There should be a low threshold to perform a systematic evaluation of patients with dual taper stem total hip arthroplasty as early recognition and diagnosis will facilitate the initiation of appropriate treatment.

Mechanically assisted taper corrosion in modular TKA

The purpose of this study was to characterize the prevalence of taper damage in modular TKA components. One hundred ninety-eight modular components were revised after 3.9±4.2 years of implantation. Modular components were evaluated for fretting corrosion using a semi-quantitative 4-point scoring system. Design features and patient information were assessed as predictors of fretting corrosion damage. Mild-to-severe fretting corrosion (score ≥2) was observed in 94/101 tapers on the modular femoral components and 90/97 tapers on the modular tibial components. Mixed alloy pairs (p=0.03), taper design (p<0.001), and component type (p=0.02) were associated with taper corrosion. The results from this study supported the hypothesis that there is taper corrosion in TKA. However the clinical implications remain unclear.

Outcomes of dual modular cementless femoral stems in revision hip arthroplasty

With an increasing number of primary hip replacements being performed every year, the burden of revision hip arthroplasty, for septic and aseptic loosening, recurrent dislocation or periprosthetic fracture, is also increasing. In recent years, different approaches to revising the femoral prosthesis have emerged; including both cemented and cementless techniques. With a stable cement mantle and good bone quality, or through the use of impaction bone grafting when bone stock is lacking, it is possible to re-cement a femoral prosthesis. Alternatively, a cementless modular femoral prosthesis may be used, providing the surgeon with further options for restoring leg length, hip offset, anteversion and stability. Studies evaluating the use of modular cementless prostheses have so far been limited to midterm studies, with results comparable to primary hip arthroplasty. There are some concerns, however, regarding tribological complications such as stem fracture, corrosion, and failure, and long-term studies are required to further evaluate these concerns. This review outlines the current evidence for the use of both cemented and cementless modular femoral prostheses in the setting of revision hip arthroplasty. Results of prospective and retrospective studies will be outlined, along with results obtained from national joint registries.

Early corrosion-related failure of the rejuvenate modular total hip replacement

BACKGROUND

The Rejuvenate modular-neck stem implant (Stryker Orthopaedics, Mahwah, New Jersey) was recently recalled due to corrosion at the femoral neck-stem junction. The purpose of this study was to investigate the rate of corrosion-related failure and survivorship of this implant and analyze the correlation of implant and patient factors with serum metal ion levels and revisions.

METHODS

From June 2009 to July 2012, 123 Rejuvenate total hip arthroplasty stems (ninety-seven modular and twenty-six non-modular) were implanted in 104 patients by a single surgeon. Serum cobalt (Co) and chromium (Cr) levels (micrograms per liter [μg/L]) were measured postoperatively for all patients. Patients with persistent hip pain or elevated metal ion levels underwent magnetic resonance imaging for assessment of osteolysis or adverse local tissue reactions. Correlation of implant factors (stem size, head size, head length, and femoral head-neck offset) and patient factors (age, sex, and body mass index) with serum metal ion levels and revisions were analyzed with use of logistic regression models.

RESULTS

The mean duration of follow-up (and standard deviation) was 2.7 ± 0.6 years. The mean Co and Cr levels were 5.4 ± 5.7 μg/L (range, 0.2 to 31 μg/L) and 2.1 ± 1.5 μg/L (range, 0.1 to 4.3 μg/L), respectively. The differences in Co and Cr levels between the two groups (modular and non-modular) were significant: 48% of the total hip arthroplasties in the modular group resulted in elevated metal ion levels (Co >4.0 μg/L and Cr >2.0 μg/L; p < 0.05). The metal ion levels in the non-modular group were normal. In the modular group, higher metal ion levels were significantly correlated with younger age and a higher femoral head-neck offset (p = 0.04). Pain and high Co serum levels were significant predictors of revision surgery (p = 0.006). The rate of revision at the time of this study was 28% in the modular group, with the majority of the revisions performed in the second year after surgery; the Kaplan-Meier survivorship was 40% at four years.

CONCLUSIONS

The short-term high rate of corrosion-related revision with Rejuvenate modular-neck stems is striking.

[Use of allergy implants in Germany: results of a survey]

In a representative survey among members of the working group for joint replacement (AE) in Germany (86.7% response) it was found that 0.6% of patients with total knee arthroplasty (TKA) and 1.2% of patients with total hip arthroplasty (THA) may have a problem due to hypersensitivity to nickel or cobalt after implantation. Only one third of them may need revision surgery. Although patients with hypersensitivity are rare 84% of surgeons would prefer to use a specially coated allergy implant for knee arthroplasty patients. However, no long term results and few data on the topic of allergies and joint arthroplasty are available for these implants so that this has to be critically discussed with patients. Before a revision is performed it is recommended to perform knee arthroscopy to obtain tissue for microbiological and histopathological investigations. The second part of this questionnaire will look at the special question of how to deal with allergy patients based on constructed case examples.

The local effects of metal corrosion in total hip arthroplasty

Corrosion has long been recognized to occur in total hip arthroplasty, but the local effects of this process have only recently become better understood. This article provides an overview of corrosion at modular junctions, and discusses the various etiologic factors for corrosion and the biologic response to metal debris released from this junction. Algorithms are provided for diagnosis and treatment, in accordance with the best available data.

Modular taper junction corrosion and failure: how to approach a recalled total hip arthroplasty implant

Corrosion at the modular neck-stem taper junction has become an increasingly important topic as several reports have identified this couple as a possible source for early failure with findings similar to failed metal-on-metal hip arthroplasties. Recently, two different modular stem systems from a single manufacturer were voluntarily recalled due to concerns of failure of the modular taper junction. We discuss how to approach the diagnosis and management of patients with these particular stem systems. We further reviewed the literature to evaluate whether this is a manufacturer-specific defect or indicative of a broader trend. Recent studies appear to implicate the basic design of the neck-stem taper junction, rather than a single manufacturer, which is at high risk for fretting and corrosion.

Wear in total knee arthroplasty--just a question of polyethylene?: Metal ion release in total knee arthroplasty

PURPOSE

Biological reactions against wear particles are a common cause for revision in total knee arthroplasty. To date, wear has mainly been attributed to polyethylene. However, the implants have large metallic surfaces that also could potentially lead to metal wear products (metal ions and debris). The aim of this study was to determine the local release of cobalt, chromium, molybdenum and titanium in total knee arthroplasty during a standard knee wear test.

METHODS

Four moderately conforming fixed-bearing implants were subjected to physiological loadings and motions for 5×10(6) walking cycles in a knee wear simulator. Polyethylene wear was determined gravimetrically and the release of metallic wear products was measured using high resolution-inductively coupled plasma-mass spectrometry.

RESULTS

A polyethylene wear rate of 7.28 ± 0.27 mg/10(6) cycles was determined and the cumulative mass of released metals measured 1.63 ± 0.28 mg for cobalt, 0.47 ± 0.06 mg for chromium, 0.42 ± 0.06 mg for molybdenum and 1.28 ± 0.14 mg for titanium.

CONCLUSION

For other metallic implants such as metal-on-metal total hip arthroplasty, the metal wear products can interact with the immune system, potentially leading to immunotoxic effects. In this study about 12 % by weight of the wear products were metallic, and these particles and ions may become clinically relevant for patients sensitive to these materials in particular. Non-metallic materials (e.g. ceramics or suitable coatings) may be considered for an alternative treatment for those patients.

Modular neck femoral stems

Following the recall of modular neck hip stems in July 2012, research into femoral modularity will intensify over the next few years. This review aims to provide surgeons with an up-to-date summary of the clinically relevant evidence. The development of femoral modularity, and a classification system, is described. The theoretical rationale for modularity is summarised and the clinical outcomes are explored. The review also examines the clinically relevant problems reported following the use of femoral stems with a modular neck. Joint replacement registries in the United Kingdom and Australia have provided data on the failure rates of modular devices but cannot identify the mechanism of failure. This information is needed to determine whether modular neck femoral stems will be used in the future, and how we should monitor patients who already have them implanted.

Range of motion in a modular femoral stem system with a variety of neck options

Modular femoral stem systems decouple leg length, offset, and version. The hip ROM and type of impingement for 162 femoral head/neck combinations were measured at four extreme hip positions in a Sawbones pelvis and femur to identify constructs that lead to early impingement. Hip ROM increased in all positions with increasing head size and neck length. We identified a new type of impingement created by the build-up of the proximal femoral stem: femoral stem on acetabular liner impingement. Seventy percent of neutral neck options achieved our definition of acceptable ROM. In general, when utilizing a modular femoral stem, surgeons can minimize impingement by choosing the longest femoral neck that does not over-lengthen the limb, using the largest femoral head accommodated by the cup, and avoiding neck version unless the cup or stem is malaligned.

Is increased modularity associated with increased fretting and corrosion damage in metal-on-metal total hip arthroplasty devices?: a retrieval study

This retrieval study documents taper damage at modular interfaces in retrieved MOM THA systems and investigates if increased modularity is associated with increased fretting and corrosion. One hundred thirty-four (134) heads and 60 stems (41 modular necks) of 8 different bearing designs (5 manufacturers) were analyzed. Damage at the shell-liner interface of 18 modular CoCr acetabular liners and the corresponding 11 acetabular shells was also evaluated. The results of this study support the hypothesis that fretting and corrosion damage occurs at a variety of modular component interfaces in contemporary MOM THAs. We also found that modularity of the femoral stem was associated with increased damage at the head. An analysis of component and patient variables revealed that dissimilar alloy pairing, larger head sizes, increased medio-lateral offsets and longer neck moment arms were all associated with increased taper damage at the modular interfaces.

Micromotions at the taper interface between stem and neck adapter of a bimodular hip prosthesis during activities of daily living

The stem-neck taper interface of bimodular hip endoprostheses bears the risk of micromotions that can result in ongoing corrosion due to removal of the passive layer and ultimately cause implant fracture. We investigated the extent of micromotions at the stem-neck interface and the seating behavior of necks of one design made from different alloys during daily activities. Modular hip prostheses (n = 36, Metha®, Aesculap AG, Germany) with neck adapters (CoCr29Mo6 or Ti6Al4V) were embedded in PMMA (ISO 7206-4) and exposed to cyclic loading with peak loads ranging from walking (Fmax  = 2.3 kN) to stumbling (Fmax  = 5.3 kN). Translational and rotational micromotions at the taper interface and seating characteristics during assembly and loading were determined using four eddy-current sensors. Seating during loading after implant assembly was dependent on load magnitude but not on material coupling. Micromotions in the stem-neck interface correlated positively with load levels (CoCr: 2.6-6.3 µm, Ti: 4.6-13.8 µm; p < 0.001) with Ti neck adapters exhibiting significantly larger micromotions than CoCr (p < 0.001). These findings explain why high body weights and activities related to higher loads could increase the risk of fretting-induced implant failures in clinical application, especially for Ti-Ti combinations. Still, the role of taper seating is not clearly understood.