Ceramic Femoral Heads Research Articles

Lower Rates of Ceramic Femoral Head Use in Non-White Patients in the United States, a National Registry Study

BackgroundThe purpose of our study was to investigate the association of race and ethnicity with the use of the newest technology and postoperative outcomes in total hip arthroplasty (THA) using the American Academy of Orthopaedic Surgeons (AAOS) American Joint Replacement Registry (AJRR). MethodsAdult THA procedures were queried from the AJRR from 2012 to 2020. A mixed-effects multivariate regression model was used to evaluate the association of race and ethnicity with the use of the newest technology (ceramic femoral head, dual-mobility implant, and robotic assist) at 30-day, and 90-day readmission. A proportional subdistribution hazard model was used to model a risk of revision THA. ResultsThere were 85,188 THAs with complete data for an analysis of outcomes and 103,218 for an analysis of ceramic head usage. The median length of follow-up was 37.9 months (interquartile range [IQR] 21.6 to 56.3 months). In multivariate models, compared to White non-Hispanic patients, Black (odds ratio [OR] 0.79, 95% confidence interval [CI] 0.69-0.92, P < .001), Hispanic (OR 0.76, CI 0.59-0.99, P = .037), Asian (OR 0.74, CI 0.55-1.00, P = .045), and Native American (OR 0.52, CI 0.30-0.87, P = .004) patients all had significantly lower rates of ceramic head use in THA. Compared to White non-Hispanic patients, Asian (hazard ratio [HR] 0.39, CI 0.18-0.86, P = .008) and Hispanic (HR 0.43, CI 0.19-0.98, P = .043) patients had significantly lower rates of revision. No differences in 30-day or 90-day readmission rates were seen. ConclusionBlack, Hispanic, Native American, and Asian patients had lower rates of ceramic head use in THA when compared to White patients. These differences did not translate into worse clinical outcomes on a short-term follow-up. In fact, Asian patients had lower revision rates compared to non-Hispanic White patients. Additional study is necessary to evaluate the long-term consequence of lower ceramic head use in non-White patients in the United States.

Le type de insert n’a aucun impact sur les changements de densité minérale osseuse autour d’une cupule acétabulaire en titane trabéculaire imprimée en 3D

BackgroundThree-dimensional printing of implants allows the ability to produce implants and interfaces which theoretically better mimic “normal” bone behaviour, leading to a possible reduction in stress shielding thus maintaining bone mineral density (BMD). This issue was not investigated in vivo using bone scan and different bearings, therefore we did a prospective study aiming to answer: 1) Is there a loss of BMD around the 3D printed trabecular titanium cup, when compared to the native hip? 2) Does liner type influence the BMD changes around the acetabulum when a 3D printed trabecular titanium cup is used? HypothesisBMD changes around the acetabulum are not influenced by the liner type, and the cup will be associated with a reduction in BMD when compared to the native hip. Material and methodsThis is a prospective observational study of patients receiving a primary total hip arthroplasty. A 3D printed Trabecular Titanium uncemented acetabular component was used in all cases. All patients received a ceramic femoral head, with either a ceramic or polyethylene acetabular liner. BMD measurements using DXA were performed at 6 weeks, 6,12 and 24 months after surgery to evaluate remodeling changes. The 3 acetabular regions of interest (ROI) of DeLee and Charnley were used for serial comparisons of peri-acetabular BMD. The study was powered as a non-inferiority study with the principle variables compared using a two-step repeated analysis of variance. ResultsA total of 48 consecutive patients were included in the study, with all patients completing their 2 year follow up. There were no failures, revisions or complications within this cohort. We found no statistically significant difference in the BMD change scores between the operated and the native hip in any of the 3 ROI zones. We found no differences in BMD scores when comparing ceramic to polyethylene acetabular liners, head sizes and BMI. DiscussionThis study shows a similar pattern of BMD behaviour around a 3D printed cup when compared to the contralateral native hip. We were unable to show a clinical or radiological difference between the bearing material, head size, or BMI when used with this type of acetabular component. Level of EvidenceIII; prospective comparative study.

A multi-center retrospective comparative study of third generation Ceramic-on- Ceramic total hip arthroplasty in patients younger than 45 years with or without the sandwich liner: A ten-year minimum.

Ceramic-on-ceramic couplings are attractive alternative bearing surfaces that have been reported to eliminate or reduce problems related to polyethylene wear debris. However, the material in THA still remains one of the major concerns about the risk of fracture, due to its brittleness. The present study aims at reporting the fracture rate of a series of ceramic-on-ceramic THAs with use of the sandwich liner combined with a ceramic femoral head, and attempt to detect the relative risk factors, possible cause and assesse the medium-term clinical results. We retrospectively evaluated 282 patients (300 hips) with use of the sandwich liner ceramic-on-ceramic THA between 2001 and 2009 at three-centers. Patient assessment was based on demographic factors, including age, weight, gender and body-mass index. All patients were evaluated clinically and radio-graphically or computed tomography in consideration of dislocation, osteolysis, periprosthetic fracture, infection, loosening and implant fracture. five ceramic sandwich liners fracture (1.7%) were observed at an average of 7.3 years follow-up. These factors were irrelevant to the ceramic liner fracture, including age (p = 0.205), weight (p = 0.241), gender (p = 0.553), body-mass index (p = 0.736), inclination (p = 0.727), and anteversion (p = 0.606). The overall survival was 91.4% at 12 years with revision as the endpoint. Other complications included dislocation in two, perprosthetic fracture in two and osteolysis in eight hips. No hip had aseptic loosening of the implants was seen. We found that the sandwich liner may be lead to a high rate of alumina fracture and osteolysis. We have discontinued the use of sandwich liner with THA since 2009.

Mechanical behaviour investigation of PEEK coated titanium alloys for hip arthroplasty using finite element analysis

The poor mechanical strength of CP-Ti and the toxic properties of Ti6Al4V due to aluminum and vanadium contents stand out as essential issues to consider while using for total hip arthroplasty (THA). In this concern, the current study focused on investigating the stress-deformation and fatigue behaviour of three different titanium alloy stems (Ti6Al4V, Ti6Al7Nb, and Ti6Al4V ELI) with alumina ceramic femoral head and PEEK coatings using finite element analysis. The stress-deformation and fatigue behaviours were examined with and without PEEK coatings for estimating their feasibility in reducing stress-shielding effects considering knee bend gait activity for average 75 wt standard loading conditions. The fatigue behaviours were investigated using Goodman's mean stress fatigue theory by numerically analyzing employed materials' S-N (alternating stress-life cycles) curves. It was observed from the investigation that the Ti6Al7Nb stem with alumina ceramic femoral head employing PEEK coatings performed superior to other studied material combinations as it showed the lowest equivalent von-mises stresses (265.12 MPa) and the highest factor of safety (2.2895). The investigation showed that all the studied material combinations could survive for at least 10 million cycles according to their S-N curves data and respective yield strengths. Further, the employment of PEEK coatings showed their feasibility in reducing stress-shielding effects compared to bare hip implant models with a considerable increase in factor of safety.

Liner type has no impact on bone mineral density changes around a 3D printed trabecular titanium acetabular component

BackgroundThree-dimensional printing of implants allows the ability to produce implants and interfaces which theoretically better mimic “normal” bone behaviour, leading to a possible reduction in stress shielding thus maintaining bone mineral density (BMD). This issue was not investigated in vivo using bone scan and different bearings; therefore, we did a prospective study aiming to answer: 1) is there a loss of BMD around the 3D printed trabecular titanium cup, when compared to the native hip?; 2) does liner type influence the BMD changes around the acetabulum when a 3D printed trabecular titanium cup is used? HypothesisBMD changes around the acetabulum are not influenced by the liner type, and the cup will be associated with a reduction in BMD when compared to the native hip. Material and methodsThis is a prospective observational study of patients receiving a primary total hip arthroplasty. A 3D printed trabecular titanium uncemented acetabular component was used in all cases. All patients received a ceramic femoral head, with either a ceramic or polyethylene acetabular liner. BMD measurements using DXA were performed at 6 weeks, 6, 12 and 24 months after surgery to evaluate remodeling changes. The 3 acetabular regions of interest (ROI) of DeLee and Charnley were used for serial comparisons of peri-acetabular BMD. The study was powered as a non-inferiority study with the principle variables compared using a two-step repeated analysis of variance. ResultsA total of 48 consecutive patients were included in the study, with all patients completing their 2 year follow-up. There were no failures, revisions or complications within this cohort. We found no statistically significant difference in the BMD change scores between the operated and the native hip in any of the 3 ROI zones. We found no differences in BMD scores when comparing ceramic to polyethylene acetabular liners, head sizes and BMI. DiscussionThis study shows a similar pattern of BMD behaviour around a 3D printed cup when compared to the contralateral native hip. We were unable to show a clinical or radiological difference between the bearing material, head size, or BMI when used with this type of acetabular component. Level of evidenceIII; prospective comparative study.

Hip Instability Leading to Metallosis, Polyethylene Wear, and Failure of an Oxinium Femoral Head: A Case Report and Review of Literature

AbstractOxinium is a zirconium metal alloy with an oxidized (ceramicized) surface that aims to mimic the superior wear properties of a ceramic femoral head while maintaining the high strength of metal-bearing surfaces. There are several reports that illustrate the wear and/or failure of Oxinium femoral heads following abnormal head contact with metal cup, with only a few studies reporting on the occurrence of metallosis. We present a case of metallosis and failure of Oxinium femoral head following two incidents of hip instability and one closed reduction. Successful revision was performed with cemented cup and metal femoral head, with 68 months of follow-up. We aimed to highlight the importance of achieving stable and well-oriented hip components when using Oxinium-bearing surfaces and to present a short literature review regarding the wear of oxidized zirconium-bearing surfaces in hip arthroplasty.

421 Intrapelvic Protrusion of a Femoral Head in A Ceramic-on-Ceramic Total Hip Replacement, A Case Report

Abstract Introduction Ceramic on ceramic bearing in Total Hip Replacement (THR) is associated with a low but evident risk of ceramic linear fracture, which can lead to catastrophic failure if not diagnosed and treated early. Case presentation: A 59-year-old male patient, who underwent a ceramic-on-ceramic THR 8 years ago, presented to our centre with a five-week history of right hip pain, after he suddenly twisted his upper body and felt a sharp pain in his groin. Prior to the injury he had an excellent functional level with the prosthesis. His examination findings confirmed a reduced range of movement with pain in the groin on internal and external rotation. X-ray and CT of the hip confirmed a ceramic liner fracture with protrusion of the femoral head into the pelvis. A revision THR was subsequently performed. Discussion The usual pattern of liner fracture in this type of bearings is that the femoral head stays contained inside the metal cup. In our case, the ceramic femoral head uniquely fractured the liner and passed into the pelvis. To the best of our knowledge, this is the third reported case in literature where a ceramic femoral head protrudes through the metal cup into the pelvis.

Assessment of Extractability and Accuracy of Electronic Health Record Data for Joint Implant Registries

Implant registries provide valuable information on the performance of implants in a real-world setting, yet they have traditionally been expensive to establish and maintain. Electronic health records (EHRs) are widely used and may include the information needed to generate clinically meaningful reports similar to a formal implant registry. To quantify the extractability and accuracy of registry-relevant data from the EHR and to assess the ability of these data to track trends in implant use and the durability of implants (hereafter referred to as implant survivorship), using data stored since 2000 in the EHR of the largest integrated health care system in the United States. Retrospective cohort study of a large EHR of veterans who had 45 351 total hip arthroplasty procedures in Veterans Health Administration hospitals from 2000 to 2017. Data analysis was performed from January 1, 2000, to December 31, 2017. Total hip arthroplasty. Number of total hip arthroplasty procedures extracted from the EHR, trends in implant use, and relative survivorship of implants. A total of 45 351 total hip arthroplasty procedures were identified from 2000 to 2017 with 192 805 implant parts. Data completeness improved over the time. After 2014, 85% of prosthetic heads, 91% of shells, 81% of stems, and 85% of liners used in the Veterans Health Administration health care system were identified by part number. Revision burden and trends in metal vs ceramic prosthetic femoral head use were found to reflect data from the American Joint Replacement Registry. Recalled implants were obvious negative outliers in implant survivorship using Kaplan-Meier curves. Although loss to follow-up remains a challenge that requires additional attention to improve the quantitative nature of calculated implant survivorship, we conclude that data collected during routine clinical care and stored in the EHR of a large health system over 18 years were sufficient to provide clinically meaningful data on trends in implant use and to identify poor implants that were subsequently recalled. This automated approach was low cost and had no reporting burden. This low-cost, low-overhead method to assess implant use and performance within a large health care setting may be useful to internal quality assurance programs and, on a larger scale, to postmarket surveillance of implant performance.

Mid-term outcomes of the R3\u2122 delta ceramic acetabular system in total hip arthroplasty

BackgroundWhilst bony fixation of hip replacement has stable solutions, there remains controversy over which bearing best optimizes longevity and function. Ceramic-on-ceramic (CoC) bearing combinations are associated with lower risk of revision due to aseptic loosening and dislocation. Evidence for long-term functional outcomes of modern, 4th generation CoC bearings is limited. The aim of this study was to analyze outcomes and complications of the R3™ Acetabular System (Smith & Nephew, Inc., Cordova, TN, USA) in combination with BIOLOX® Delta ceramic femoral head in patients undergoing primary total hip arthroplasty (THA).MethodsBetween June 2009 and May 2011, 175 patients (178 hips) were enrolled into a prospective, study at 6 sites in Europe and prospectively followed-up at 3 months and 1, 3, 5, and 7 years postoperative.ResultsTotal WOMAC score improved from 63 (range, 22–91) preoperative to 8 (range, 0–8) at 1-year follow-up and remained unchanged at 7-year follow-up. Modified Harris hip score improved from 45 (range, 10–87) preoperative to 83 (range, 25–100) at 3 months, 91 (range, 42–100) at 1 year, and 92 (range, 46, 100) at 7 years. UCLA Activity Rating Scale score improved from 3.3 (range, 1–8) preoperative to 6.2 (range, 2–8) at 1 year; it marginally declined to 5.8 (range, 3–8) at 7-year follow-up. There were 4 trochanteric fractures and 5 patients died of unrelated reasons. Three hips were revised (2 periprosthetic fractures and 1 subluxation). The 7-year cumulative survival rate was 98.3%.ConclusionClinical and functional improvements of THA with CoC bearing are maintained at 7 years postoperative.Trial registrationClinicalTrials.Gov, NCT03566082, Registered 10 January 2018—retrospectively registered,

Biotribology in Arthroplasty: Worn Surfaces Investigation on Ceramic Hip Femoral Heads Considering Wettability

Ceramic-on-ceramic bearings for total hip replacement are considered the best choice to avoid problems such as osteolysis and wear, mainly related to soft bearings. The aim of this work was to investigate in a comparative way different kinds of ceramic femoral heads for total hip replacements from a biotribological point of view, discussing the results obtained in terms of topographies, presence of metal transfer (MT) phenomena, and wettability on their worn surfaces in a tribological framework. Different ceramic femoral heads derived from in vitro wear tests, retrieved form patients, and brand new total hip replacements were investigated. The patients group had an average age of 60 years (ranging from 27 to 83). In most cases, the cause of failure was aseptic loosening of the acetabular component. Roughness analyses were performed to measure the tribological surface evolution of the material; an SEM and EDS investigation on the explanted heads proves and quantified MT, while the wettability was measured through a novel optical laboratory set-up with the aim to furnish useful data in the framework of synovial lubrication phenomena acting in the tribosystem. For the average roughness measurements on explanted specimens were considered three parameters (Ra = the average area between the roughness profile and its mean line; Rt = the vertical distance from the deepest valley to the highest peak of the roughness profile; and Rsk = it is the skewness and it is a measure of the asymmetry of the amplitude distribution function. In other words, the skewness indicates whether a surface is dominated by peaks or by valleys) and their values were: Ra 0.22 ± 0.12 μm, Rt 34.5 ± 13.5 μm and Rsk −0.01 ± 11.3; on the new specimens we measured Ra 0.01 ± 0.001 μm, Rt 0.12 ± 0.09 μm, and Rsk = 5.67 ± 8.7; for the in vitro specimens they were Ra 0.05 ± 0.12 μm, Rt 0.71 ± 1.4 μm and Rsk 7.73 ± 20.6. The wettability angle measurements showed hydrophilic surfaces for all femoral heads considered in this study with small differences between the three investigated categories, allowing to discuss their effects on the biobearings’ lubrication phenomena.

Tailor-made design, fabrication and validation of SrO doped nanostructured ZTA ceramic Femoral head – Acetabular socket liner assembly

An established commercial grade SrO doped ZTA composition has been considered to design, fabrication through uniaxial pressing followed by sintering and polishing, validation of dimension, 3D surface profile, 3D microstructure, and compressive load bearing capacity of femoral head – acetabular socket liner prototypes for the hip prosthesis. While design and dimensions are concerned, both the steel (HRC60) molds were designed and machined to achieve precious dimensions of femoral head (FH; OD – 30 ± 0.01 mm) and acetabular socket liner (ASL; ID – 30.15 ± 0.01 mm). A close variation in the range of ±0.01 mm was confirmed the precision geometry of polished FH and ASL with consideration of 22 points coordinate measuring method (CMM). 3D surface profile ensures the surface characteristics of Ra = 0.2 ± 0.01 μm and Rq = 0.5 ± 0.01 μm for outer surface of FH and an inner surface of ASL, respectively. Structure integrity and fabrication defects including cracks and pores free bulk structures were confirmed by Micro CT. The compressive load resistance known as burst strength for independent FH and FH-ASL assembly were measured 16.2 KN and 17.6 KN, respectively. The developed ceramic prototypes have an economic advantage and can be adopted as artificial hip prosthesis after extensive in-vitro and in-vivo analysis.

Stand up! Are normal weight-bearing forces sufficient for a 12/14 Morse taper locking in total hip arthroplasty?

The aim of this study was to investigate total hip arthroplasty (THA) Morse taper pull-off strengths after impaction prior to cyclical loading compared to cyclical loading alone. The practical relevance of the experiment is to provide a perspective on what may be clinically satisfactory taper assembly given the spectrum of head tapping patterns used by surgeons, as well as compare traditional impaction performed in standard THA with alternate methods of taper engagement such as 'in situ assembly' used in micro-invasive techniques. 36 taper constructs utilising a combination of cobalt-chrome alloy and ceramic-titanium alloy junctions were investigated in vitro in wet and dry conditions with cyclical loading of the constructs. Taper disengagement strengths with and without impaction were compared. Secondary investigation of the surface roughness of the heads and tapers was also assessed. An impaction to a wet taper resulted in a greater pull off force compared to a dry taper with a CoCr head and taper combination. Impacting the head and dryness of the taper did not affect pull off forces of a ceramic femoral head on titanium taper. Pulling a head off a taper significantly alters the head surface roughness. Impaction of a taper does not provide any benefit over cyclical loading of a taper assembly alone for pull-off strength.

Global diversity in bearings in primary THA.

Choice of articulating materials, head size and the design of the articulation will become decisive for the long-term performance of a total hip arthroplasty (THA) and especially in terms of risk for dislocation and wear-related problems. Here we account for common alternatives based on available studies and the evidence that can be derived from them.Metal or ceramic femoral heads articulating against a liner or cup made of highly cross-linked polyethylene and ceramic-on-ceramic articulations have about similar risk for complications leading to revision, whereas the performance of metal-on-metal articulations, especially with use of big heads, is inferior. The clinical significance of problems related to ceramic-on-ceramic articulations such as squeaking remains unclear. With use of current technology ceramic fractures are rare.Large femoral heads have the potential to increase the range of hip movement before impingement occurs and are therefore expected to reduce dislocation rates. On the other hand, issues related to bearing wear, corrosion at the taper-trunnion junction and groin pain may arise with larger heads and jeopardize the longevity of THA. Based on current knowledge, 32-mm heads seem to be optimal for metal-on-polyethylene bearings. Patients with ceramic-on-ceramic bearings may benefit from even larger heads such as 36 or 40 mm, but so far there are no long-term reports that confirm the safety of bearings larger than 36 mm.Assessment of lipped liners is difficult because randomized studies are lacking, but retrospective clinical studies and registry data seem to indicate that this liner modification will reduce the rate of dislocation or revision due to dislocation without clear evidence of clinically obvious problems due to neck-liner impingement.The majority of studies support the view that constrained liners and dual mobility cups (DMC) will reduce the risk of revision due to dislocation both in primary and revision THA, the latter gaining increasing popularity in some countries. Both these devices suffer from implant-specific problems, which seem to be more common for the constrained liner designs. The majority of studies of these implants suffer from various methodological problems, not least selection bias, which calls for randomized studies preferably in a multi-centre setting to obtain sufficient power. In the 2020s, the orthopaedic profession should place more effort on such studies, as has already been achieved within other medical specialties, to improve the level of evidence in the choice of articulation when performing one of the most common in-hospital surgical procedures in Europe.Cite this article: EFORT Open Rev 2020;5:763-775. DOI: 10.1302/2058-5241.5.200002

Are Oxinium Femoral Heads Superior to Alternative Bearing Surface Materials? A Systematic Review

AbstractOxidized zirconium (OxZr) femoral heads were developed to emulate the superior wear and scratch properties of ceramics while eliminating their unwanted tendency for brittle fracturing. Studies using OxZr have demonstrated reduced linear and volumetric wear of polyethylene (PE) liners when compared with cobalt chrome, ceramic, and steel femoral heads. The purpose of this systematic review was to determine the difference in revision rates, radiologically determined linear wear rates, and patient-reported outcomes among OxZr and alternative bearing materials. Following the Preferred Reporting Items for Systematic Review and Meta-Analysis protocols, a systematic review of published literature through April 24, 2018 was conducted. Among the 862 cases included at a mean weighted follow-up of 4.78 years, the revision THA rate and patient-reported outcomes were similar among OxZr and alternative bearing materials. One of the five studies demonstrated significantly lower linear wear rates in the OxZr group when paired with ultrahigh molecular-weight PE (OxZr 0.03 mm/y vs. stainless-steel 0.11 mm/y; p &lt; 0.001) and when paired with highly-crosslinked PE (OxZr 0.02 mm/y vs. stainless-steel 0.04 mm/y; p &lt; 0.001). The remaining four studies found no difference in linear wear rates. OxZr demonstrated similar outcome to that of modern-day ceramic and metal femoral heads for short- and mid-term revision surgery rates and patient-reported outcomes. Longer term studies are needed to evaluate if any long-term wear advantages are seen with the use of OxZr femoral heads and if the use of OxZr is cost effective compared with ceramic or metal alternatives. The level of evidence of the study is level II, systematic review.

Influence of Metallic Deposition on Ceramic Femoral Heads on the Wear Behavior of Artificial Hip Joints: A Simulator Study.

Several retrieval studies have reported on metallic depositions on ceramic femoral heads, but the effect on the wear behavior of artificial hip joints has not been investigated in wear simulator studies. In the present study, retrieved ceramic heads with metallic depositions as third particles were tested against cross-linked ultra-high-molecular-weight polyethylene (UHMWPE) liners in a hip wear simulator. The amount of liner wear and expansion of metallic depositions on the heads were determined before and after wear testing with digital microscopy. The surface roughness of the heads was investigated in areas with and without metallic depositions by laser scanning microscopy. After five million load cycles, a non-significant reduction in the metallic formation on the retrieved heads was found. The metallic areas showed a higher surface roughness compared to unconcerned areas. The liners showed a higher wear rate of 1.57 ± 1.36 mg/million cycles for 28 mm heads and 2.42 ± 0.82 mg/million cycles for 36 mm heads with metallic depositions, in comparison with new ceramic heads with a 28 mm size ((−0.06 ± 0.89) mg/million cycles) and 36 mm size ((2.04 ± 0.46) mg/million cycles). Metallic transfer on ceramic heads can lead to an increased surface roughness and higher wear rates at the UHMWPE liners. Therefore, metallic contact of the ceramic femoral head should be avoided.

Polyethylene Wear With Ceramic and Metal Femoral Heads at 5 Years: A Randomized Controlled Trial With Radiostereometric Analysis

BackgroundA common bearing combination in total hip arthroplasty today is a metal femoral head articulating with polyethylene in the cup. Ceramic heads are thought to be more resistant to third-body damage, and have better wettability and decreased surface roughness, which taken together have been suggested to result in less polyethylene wear. The purpose of this study is to compare the initial creep deformation and follow wear pattern, using radiostereometric analysis, of ceramic and metal femoral heads that articulate with a modern highly cross-linked polyethylene cup liner. MethodsFifty patients with primary osteoarthritis and scheduled for an uncemented total hip arthroplasty were randomized 1:1 to either a ceramic (BIOLOX delta) or a metal (CoCr) femoral head. The patients were followed up for 5 years with repeated radiostereometric analysis examinations (postoperatively, then at 14 days, 3, 12, 24, and 60 months), as well as a hip-specific outcome questionnaire. ResultsDuring the first 3 months both groups showed expected creep within the liner of 0.12 mm (standard deviation 0.03) for the ceramic and 0.08 mm (standard deviation 0.02) for the metal heads. Between 3 months and 5 years there was very little wear of the liner in either group, corresponding to 0.003 mm/y for ceramic and 0.007 mm/y for metal heads. There was no difference in cup migration or clinical outcome between the groups and no cups were revised. ConclusionWith the introduction of modern highly cross-linked polyethylene, the ceramic head demonstrates no superiority when it comes to either early deformation or polyethylene wear compared with the metal head.

Influence of Different Damage Patterns of the Stem Taper on Fixation and Fracture Strength of Ceramic Ball Heads for Total Hip Replacement.

Background Modularity finds frequent application in total hip replacement, allowing a preferable individual configuration and a simplified revision by retaining the femoral stem and replacing the prosthetic head. However, micromotions within the interface between the head and the stem taper can arise, resulting in the release of wear debris and corrosion products. The aim of our experimental study was to evaluate the influence of different taper damages on the fixation and fracture stability of ceramic femoral heads, after static and dynamic implant loading. Methods Ceramic ball heads (36 mm diameter) and 12/14 stem tapers made of titanium with various mild damage patterns (intact, scratched, and truncated) were tested. The heads were assembled on the taper with a quasistatic load of 2 kN and separated into a static and a dynamic group afterwards. The dynamic group (n = 18) was loaded over 1.5 million gait cycles in a hip wear simulator (ISO 14242-1). In contrast, the static group (n = 18) was not mechanically loaded after assembly. To determine the taper stability, all heads of the dynamic and static groups were either pulled off (ASTM 2009) or turned off (ISO 7206-16). A head fracture test (ISO 7206-10) was also performed. Subsequent to the fixation stability tests, the taper surface was visually evaluated in terms of any signs of wear or corrosion after the dynamic loading. Results In 10 of the 18 cases, discoloration of the taper was determined after the dynamic loading and subsequent cleaning, indicating the first signs of corrosion. Pull-off forces as well as turn-off moments were increased between 23% and 54% after the dynamic loading compared to the unloaded tapers. No significant influence of taper damage was determined in terms of taper fixation strength. However, the taper damage led to a decrease in fracture strength by approximately 20% (scratched) and 40% (truncated), respectively. Conclusion The results suggest that careful handling and accurate manufacturing of the stem taper are crucial for the ceramic head fracture strength, even though a mild damage showed no significant influence on taper stability. Moreover, our data indicate that a further seating of the prosthetic head may occur during daily activities, when the resulting hip force increases the assembly load.

Comparative Biomechanical Study of Crosslinked Polyethylene Wear with 36-mm Ceramic Femoral Heads and with 32-mm Metal Femoral Heads.

Objective This study aims to compare the in vitro wear rate of crosslinked, high molecular weight polyethylene coupled to 36-mm diameter ceramic heads and 32-mm diameter metal heads. Methods Ceramic-on-polyethylene (36 mm) and metal-on-polyethylene (32 mm) tribological pairs were submitted to biomechanical tests in a simulator to determine the wear rate after 15 × 10 6 cycles. Results A statistically significant difference ( p = 0.0005) was detected when comparing the wear rate of assemblies with metallic heads (average wear: 14.12 mg/MC) and ceramic heads (average wear: 7.46 mg/MC). Conclusion The present study demonstrated the lower wear rate in prosthetic assemblies using 36-mm crosslinked ceramic-on-polyethylene tribological pairs compared to 32-mm crosslinked metal-on-polyethylene assemblies. This finding demonstrates the effectiveness of ceramic-on-polyethylene tribological pairs, even with large diameter heads.

Leg Length Balance in Total Hip Arthroplasty for Patients with Unilateral Crowe Type IV Developmental Dysplasia of the Hip.

ObjectiveTo explore the leg length balance in total hip arthroplasty (THA) with shortening subtrochanteric osteotomy (SSTO) or not for unilateral Crowe type IV developmental dysplasia of the hip (DDH) through the evaluation of postoperative full‐length anteroposterior radiographs.MethodsThe postoperative radiographs of 60 patients with unilateral Crowe type IV DDH from July 2012 to May 2019 were retrospectively reviewed. All patients underwent THA using the Pinnacle Acetabular Cup system, a ceramic liner and femoral head, and the S‐ROM stem with a proximal sleeve or cone. Patients with leg length discrepancy (LLD) < 10 mm were defined as the non‐LLD group. To identify differences associated with SSTO, the group was further divided into two groups based on whether the patient underwent SSTO. A total of 48 patients (26 for SSTO and 22 for non‐SSTO) were in the non‐LLD group. There were 3 male and 45 female patients. The mean age of the patients in the non‐LLD group was 39 years. These data, including leg length, femoral length, the height of center of rotation (COR) of the hip, the depth of the sleeve or cone in the femoral medullary canal and the height of the greater trochanter, were measured.ResultsIn the non‐LLD group, the femoral lengths in both SSTO and non‐SSTO groups were significantly shorter on the operated side compared with the contralateral side, and the mean discrepancy in the SSTO group was approximately equal to the mean length of the SSTO. The mean height of the COR of the hip on the operated sides in both SSTO and non‐SSTO groups was 13.2 mm, and the contralateral sides were 15.2 and 15.5 mm, respectively. The depth of the sleeve or cone in the femoral medullary canal between SSTO and non‐SSTO groups was 21.7 and 30.6 mm, respectively. The depth of the sleeve or cone in the SSTO group was negatively correlated with the length of SSTO. The heights of the greater trochanter in the operated and contralateral sides were 5.3 and 16.6 mm in the SSTO group, and 13.2 and 17.2 mm in the non‐SSTO group, respectively.ConclusionsShortening subtrochanteric osteotomy led to femoral shortening on the operated side for patients with unilateral Crowe type IV DDH. The position of the sleeve or cone should be close to the apex of the greater trochanter to compensate the length of the SSTO. The position of the sleeve or cone without SSTO should be adjusted to make sure that the height of the greater trochanter on the operated side is close to that on the contralateral side.

Contact conditions for total hip head-neck modular taper junctions with microgrooved stem tapers

Implant failure due to fretting-corrosion of head-neck modular junctions is a rising problem in total hip arthroplasty. Fretting-corrosion initiates when micromotion leads to metal release; however, factors leading to micromotion, such as microgrooves on the stem taper, are not fully understood. The purpose of this study is to describe a finite element analysis technique to determine head-neck contact mechanics and investigate the effect of stem taper microgroove height during head-neck assembly. Two-dimensional axisymmetric finite element models were created. Models were created for a ceramic femoral head and a CoCrMo femoral head against Ti6Al4V stem tapers and compared to available data from prior experiments. Stem taper microgroove height was investigated with a generic 12/14 model. Head-neck assembly was performed to four maximum loads (500 N, 2000 N, 4000 N, 8000 N). For the stem taper coupled with the ceramic head, the number of microgrooves in contact and plastically deformed differed by 2.5 microgrooves (4%) and 6.5 microgrooves (11%), respectively, between the finite element models and experiment. For the stem taper coupled with the CoCrMo head, all microgrooves were in contact after all assembly loads in the finite element model due to an almost identical conical angle between the taper surfaces. In the experiments, all grooves were only in contact for the 8000 N assembly load. Contact area, plastic (permanent) deformation, and contact pressure increased with increasing assembly loads and deeper microgrooves. The described modeling technique can be used to investigate the relationship between implant design factors, allowing for optimal microgroove design within material couples.