Metal Femoral Head Research Articles

Evaluation of in vivo wear of vitamin E-diffused highly crosslinked polyethylene at five years: a multicentre radiostereometric analysis study.

The primary aim of this study was to compare the wear properties of vitamin E-diffused, highly crosslinked polyethylene (VEPE) and one formulation of moderately crosslinked and mechanically annealed ultra-high molecular weight polyethylene (ModXLPE) in patients five years after primary total hip arthroplasty (THA). The secondary aim was to assess the clinical results of patients treated with VEPE by evaluating patient-reported outcome measures (PROMs), radiological evidence of fixation, and the incidence of mechanical failure. A total of 208 patients (221 THAs) from four international centres were recruited into a prospective study involving radiostereometric analysis (RSA) and the assessment of clinical outcomes. A total of 193 hips (87%) were reviewed at the five-year follow-up. Of these, 136 (70%) received VEPE (vs ModXLPE) liners and 68 (35%) received ceramic (vs metal) femoral heads. PROMs and radiographs were collected preoperatively and at one, two, and five years postoperatively. In addition, RSA images were collected to measure PE wear postoperatively and at one, two, and five years after surgery. We observed similar bedding in one year postoperatively and wear two years postoperatively between the two types of liner. However, there was significantly more penetration of the femoral head in the ModXLPE cohort compared with the VEPE cohort five years postoperatively (p < 0.001). The only variables independently predictive of increased wear were ModXLPE (vs VEPE) liner type (β = 0.22, p = 0.010) and metal (vs ceramic) femoral head (β = 0.21, p = 0.013). There was no association between increased wear and the development of radiolucency (p = 0.866) or PROMs. No patient had evidence of osteolysis. Five years postoperatively, patients with VEPE (vs ModXLPE) and ceramic (vs metal) femoral heads had decreased wear. The rates of wear for both liners were very low and have not led to any osteolysis or implant failure due to aseptic loosening.

Hip stability after total hip arthroplasty predicted by intraoperative stability test and range of motion: a cross-sectional study

BackgroundDislocation continues to be a common complication following total hip arthroplasty (THA). A larger intraoperative range of motion (ROM) is believed to minimize dislocation risk, and intraoperative stability tests have been used to assess the ROM. However, it is not clear whether or not intraoperative stability tests can predict hip stability after THA. It is also unclear which angles are required in intraoperative stability tests. We investigated the usefulness of intraoperative stability tests, and other risk factors to predict hip stability after THA.MethodsPatients operated by single surgeon at one hospital from June 2009 to December 2013 were evaluated. This study included 185 hips with 32 mm metal femoral head. The range of internal rotation with 90° hip flexion (IR angle) was measured as an intraoperative stability test. The variables studied as risk factors included age, height, weight, gender, cerebral dysfunction, preoperative diagnosis, history of previous hip surgery, and IR angle.ResultsMean IR angle was statistically different between patients with dislocation and patients without dislocation (59.5° vs 69.6°: p = 0.006). Cerebral dysfunction and a history of previous hip surgery were statistically related with prevalence of dislocation (p = 0.021, and p = 0.011). The receiver-operating characteristic curve analysis suggested that the cutoff points for IR angle were 51° and 67°. Dislocation rate in larger IR angle group was significantly lower than the rate in smaller IR angle group when patients were divided by 51° (p = 0.002). Logistic regression analyses showed that significant risk factors were cerebral dysfunction (OR: 5.3 (95%CI 1.1–25.9); p = 0.037), history of previous hip surgery (OR: 8.6 (95%CI 1.2–63.0); p = 0.035), and IR angle (OR: 10.4 (95%CI 1.9–57.1); p = 0.007).ConclusionsThe results showed that intraoperative stability test, especially the IR angle, was a useful method to predict hip stability after THA, and a larger intraoperative ROM reduced the likelihood of dislocation. 51° and 67° were indicated as cutoff points for IR angle. Cerebral dysfunction and a history of previous hip surgery are also risk factors for the incidence of dislocation after THA.Trial registrationThis is a retrospective study, not a clinical trial defined by the World Health Organization (WHO).

Femoral head wear and metallosis caused by damaged titanium porous coating after primary metal-on-polyethylene total hip arthroplasty: a case report

Excessive metal femoral head wear has been described only as revision surgery complication after primary ceramic-on-ceramic total hip arthroplasty (THA). Here, we present the first case of metal femoral head wear after primary metal-on-polyethylene THA. A 56-year-old woman was referred to our outpatient clinic 17 years after primary right-sided THA, experiencing pain and decreased right hip range of motion. Radiographic examination revealed acetabular cup dislocation, eccentric femoral head wear, damaged titanium porous coating of femoral stem, metallosis, and pseudotumor formation. Endoprosthetic components were extracted, but further reconstruction was impossible due to presence of large acetabular bone defect. Macro- and micro-structure of extracted components were analyzed. Acetabular liner surface was damaged, with scratches, indentations, and embedded metal debris particles present on the entire inner surface. Analysis of metal debris by energy-dispersive spectroscopy showed that it consisted of titanium and stainless-steel particles. Femoral head was gravely worn and elliptically shaped, with abrasive wear visible under scanning electron microscope. No signs of trunnionosis at head/neck junction were observed. Microstructure of femoral head material was homogeneous austenitic, with microhardness of 145 HV 0.2, which is lower than previously described titanium hardness. In conclusion, detached titanium porous coating of femoral stem can cause stainless-steel femoral head wear in primary metal-on-polyethylene THA. As soon as such detachment becomes evident, revision surgery should be considered to prevent devastating complications.

Large Metal Heads and Highly Cross-Linked Polyethylene Provide Low Wear and Complications at 5-13 Years

BackgroundHighly cross-linked polyethylene (XLPE) is reported to have low rates of linear and volumetric wear at 10-14 years. In a prior study, larger (36 and 40 mm) femoral heads were associated with more volumetric wear, but there were only 12 hips with these heads. MethodsWe evaluated 107 hips (93 patients, with a mean age of 76 years) with one design of uncemented acetabular component, a 36 (90 hips) or 40 mm (17 hips) metal femoral head, and one electron beam 100 kGy irradiated and remelted XLPE at a mean follow-up of 8 years (range 5-13 years). Selection of these femoral heads was based on several factors, including the perceived risk of dislocation, the outer diameter size of the acetabular component, and liner availability. Measurements of linear and volumetric wear were performed in one experienced laboratory by the Martell method and analyzed using the first-to-last method. Standard radiographs, with additional Judet views, were used to detect periprosthetic osteolysis. Clinical records were used to determine the complications of dislocation, liner fracture, and painful trunnion corrosion. ResultsFor the entire cohort, the median linear wear rate was 0.041 mm/y (95% confidence interval, 0.031-0.057) and the median volumetric wear rate was 34.6 mm3/y (95% confidence interval, 31.4-53.5). With the numbers available, there was no difference in linear or volumetric wear between the 36 and 40 mm head sizes. Small, asymptomatic osteolytic lesions were noted in 3 hips (2%). There were 3 patients (3%) with dislocation (2 early and 1 late), but these have not had a revision. There were no revisions for loosening, no liner fracture, and no patient with symptomatic trunnion corrosion. ConclusionThis acetabular component and XLPE with large metal heads had low rates of linear and volumetric wear. Large metal femoral heads did not lead to liner fracture, loosening, or symptomatic trunnion corrosion in this patient population. However, we recommend longer clinical follow-up studies and caution in the routine use of larger metal femoral heads in other, younger patient populations.

Results of Total Hip Arthroplasty with 36-mm Metallic Femoral Heads on 1st Generation Highly Cross Linked Polyethylene as a Bearing Surface in Less than Forty Year-old Patients: Minimum Ten-year Results.

PurposeWe evaluated long-term clinical and radiographic results in patients underwent primary total hip arthroplasty (THA) using 36-mm metallic femoral head and 1st generation highly cross-linked polyethylene among patients aged 40 years and less, with minimum 10 years follow-up.Materials and MethodsWe retrospectively reviewed 20 hips underwent primary THA by one hip surgeon using 36-mm femoral head and 1st generation highly cross-linked polyethylene from 2004 to 2006. Mean follow up was 131.55 months. Clinical follow-ups included functional measurements. And we evaluated post operative complications, prosthesis loosening, failure, and osteolysis. For radiologic evaluations, together with position of acetabular cup at 6 weeks later of postoperation, we separately calculated the penentrations of femoral heads into polyethylene liners during postoperation and one year later check-ups, and during one year later check-ups and final check-ups. Polywear pro3D 5.10 software was used to measure penetrations of femoral head.ResultsMean acetabular cup inclination and anteversion were 49.02° and 10.19°, respectively. Mean thickness of the polyethylene liner at 45° was 6.44 mm. There were no major complications such as implant loosening or osteolysis, and one case of dislocation occurred. Average modified Harris hip score at final follow-up was 91, and Merle d'Aubigne and Postel scores 15 were or over. Average femoral head penetration of bedding wear was 0.170±0.039 mm/year. Steady-state wear rates was 0.059±0.006 mm/year.ConclusionResults of THA with 36-mm metallic femoral heads on 1st generation highly cross linked as a bearing surface in less than 40 year-old patients were satisfactory.

Evaluation of Surface Finish and Dimensional Control of Tribological Metal-Ultra High Molecular Weight Polyethylene Pair of Commercially Available Hip Implants

BackgroundDimensional control and surface finish of the femoral head and acetabular liner are critical factors in the manufacturing process due to the risk of increased polyethylene wear, which is the primary cause of aseptic failure of a metal/polymer hip prosthesis. The aim of this study is to perform a dimensional and surface finish analysis to evaluate the reproduction and accuracy of the manufacturing processes of metal femoral heads and ultra high molecular weight polyethylene acetabular liners. MethodsFour femoral heads and acetabular liners from 5 manufacturers were evaluated. The methods of evaluation followed the standards ISO 7206-2:2011 and ISO 21535:2010. ResultsThe diameter, sphericity, and roughness of the femoral heads from all the manufacturers were in accordance with the standard requirements. Only the sphericity showed a lack of repeatability among the manufacturers. The variability in sphericity was high among some manufacturers and low in others. The diameters of the acetabular liners of 2 manufacturers were not in accordance with the standard requirements. The repeatability of sphericity, thickness, and roughness of the acetabular liners were heterogeneous among the manufacturers, which means that some manufacturers need to improve quality control. ConclusionOur results showed a good dimensional and surface finish control of the manufacturing processes of the femoral heads. However, the same control was not shown during the manufacturing of the acetabular liners although all samples had a thickness and sphericity in accordance with the standard. A better quality control of the manufacturing process of ultra high molecular weight polyethylene acetabular liners should be made to improve the dimensional parameters of the acetabular liners and the tribological pair.

Mixing of Head-Stem Components in Total Hip Arthroplasty

BackgroundImplant manufacturers proclaim that the tapers of modular total hip arthroplasty are not standardized and can vary from manufacturer to manufacturer. That is why the combination of various components from different manufacturers (“Mix and Match”) is not permitted. In this study, different taper combinations were investigated experimentally to assess the effect of “Mix and Match” regarding the taper connection strength. MethodsTorque-off tests using hip stems and metal femoral heads from 6 different implant manufacturers were performed. First the components were tested as intended and afterwards the stems were combined with metal heads from other manufacturers. ResultsThere was no significant difference in taper connection strength when stems from the manufacturers Link, Smith & Nephew, and Zimmer were combined with heads from other manufacturers. The Biomet stems showed a significantly reduced taper connection strength if femoral heads of Aesculap, DePuy, or Smith & Nephew were used. On the contrary, the DePuy stems in combination with the originally intended femoral heads showed a significantly lower taper connection strength compared to the use of heads from Link, Biomet, and Zimmer. The same was observed for the Aesculap stems in combination with Zimmer heads. ConclusionThe results of this study suggest that mixing components from different manufacturers may affect the taper connection strength and could reduce the stability. As safety should be a high priority in patient treatment, any potential risks should be avoided. Therefore, mixing and matching of heads and femoral stems from different manufacturers cannot be recommended.

Adverse reaction to local metal debris does not always come from metal on metal bearing wear

Introduction Abnormal metal ion release from wear of metal-on-metal (MoM) bearing in total hip arthroplasty (THA) is associated with adverse local reactions to metal debris (ARMD). Metal particles may also arise from wear and corrosion of the implant's modular junction. The aim of this study was to compare ion levels and rate of ARMD between patients with THA sharing the same MoM bearing but one group having monoblock stems versus another group having modular stems. Materiel et methodes This study included 45 patients who underwent primary MoM THA using the same acetabular component and large diameter metallic modular femoral head. 32 hips received a modular stem and 13 hips received a monoblock stem. Cobalt (Co) and chromium (Cr) ion concentrations, ARMD rate and function measured by UCLA and WOMAC scores were compared between groups. Resultats ARMD rate was significantly lower in the monoblock group (16%) compared to the modular group (46%, P = 0.031). Revision for ARMD was performed at 115 ± 5.9 months after primary THA in the monoblock group versus 63 ± 2.3 months in the modular group. ARMD cases had severe wear and corrosion of the junction between stem and femoral head trunnion in all monoblock cases and the junction between stem and modular neck in all the modular ones. Cr and Co ions levels were significantly lower in the monoblock stem group: 2.0 ± 1.0 μg/L vs. 7.2 ± 11.4 μg/L (P Discussion The rate of ARMD was significantly higher in the modular stem group and this group required revision earlier. Although both groups had MoM bearings, corrosion at stem/neck or neck/head junctions were seen as the source of excessive metal ions release lea. Conclusion In the presence of ARMD, MoM bearing wear may not be the main source of failure. Modular junction's poor performances may be more deleterious than the bearing. To avoid such complication, THA femoral stem modular junctions should be eliminated (return to a full monoblock implant) or have improved junction design.

The impact of surface and geometry on coefficient of friction of artificial hip joints

Coefficient of friction (COF) tests were conducted on 28-mm and 36-mm-diameter hip joint prostheses for four different material combinations, with or without the presence of Ultra High Molecular Weight Polyethylene (UHMWPE) particles using a novel pendulum hip simulator. The effects of three micro dimpled arrays on femoral head against a polyethylene and a metallic cup were also investigated. Clearance played a vital role in the COF of ceramic on polyethylene and ceramic on ceramic artificial hip joints. Micro dimpled metallic femoral heads yielded higher COF against a polyethylene cup; however, with metal on metal prostheses the dimpled arrays significantly reduced the COF. In situ images revealed evidence that the dimple arrays enhanced film formation, which was the main mechanism that contributed to reduced friction.

Mechanical Stability of the Taper Connection of Large Metal Femoral Heads With Adapter Sleeves in Total Hip Arthroplasty Analyzed Using Explicit Finite Element Simulations

BackgroundLarge diameter heads (LDHs) of metal-on-metal bearings in total hip arthroplasty provide increased range of motion and reduced dislocation rates. However, major concerns grew over high wear rates from the modular connection between femoral stem and head, especially in combination with adapter sleeves. MethodsA computational study on the taper connection stability of LDH (50 mm) with adapter sleeves of different lengths (S, M, L, and XL) compared with a standard femoral head (32 mm) without adapter sleeves was conducted using explicit finite element analyses. Four different impact configurations were considered resulting from varied mallet mass (0.5 vs 1.0 kg) and velocity (1.0 vs 2.0 m/s). The taper stability was evaluated by determination of the pull-off forces and micromotions due to simulated joint loads during walking (2 kN and 7.9 Nm, respectively). Moreover, the deformations of the adapter sleeves and the contact area in the taper connections were evaluated. ResultsAlthough the pull-off forces of the LDH with different-sized adapter sleeves were comparable, contact area decreased and adapter sleeve deformations increased (up to 283%) with an increasing adapter sleeve length. Moreover, the micromotions of LDH with adapter sleeves were up to 7-times higher, as compared with the standard femoral head without an adapter sleeve. ConclusionThe present numerical study confirms that the assembly technique of LDH with adapter sleeves reveals increased micromotions compared with standard femoral head sizes. We could demonstrate that deviations of the stem trunnion geometry and improper surgical instructions led to worse mechanical stability of the taper connection.

The surface topography of a metallic femoral head and its influence on the wear mechanism of a polymeric acetabulum

The wear mechanisms of friction components depend on conditions of articulation, material properties and surface topography of the co-acting parts. Therefore, it is important to examine these determinants in order to improve the durability of a friction pair. With the view of securing the longer life of articulating surfaces, a metallic femoral head used in conjunction with a polymeric acetabulum was subject to research. The components of the friction pair were prepared in accordance with the standard specification ASTM F2033-12. From the precision machining process of metallic femoral heads, two different kinds of surface topography (defined by Ra parameter: Ra(A)<Ra(B)) were obtained. The tribological research was performed with a testing machine simulating the kinematic movements and the working conditions of a natural joint (friction pair: ball-and-socket) in the Ringer's solution. The measurements of the surface topography (machined and worn surfaces) were conducted using the following measuring devices: coordinate measuring machine, white light interference microscopy and scanning electron microscopy. Based on the analysis results, the influence of the surface topography of the metallic ball upon tribological characteristics was determined. The wear mechanisms of the polymeric socket resulted from a number of phenomena, including plastic deformation, abrasive wear, fatigue and adhesion.

Cost Analysis of Ceramic Heads in Primary Total Hip Arthroplasty.

The advent of adverse local tissue reactions seen in metal-on-metal bearings, and the recent recognition of trunnionosis, have led many surgeons to recommend ceramic-on-polyethylene articulations for primary total hip arthroplasty. However, to our knowledge, there has been little research that has considered whether the increased cost of ceramic provides enough benefit over cobalt-chromium to justify its use. The primary purpose of this study was to compare the cost-effectiveness of ceramic-on-polyethylene implants and metal-on-polyethylene implants in patients undergoing total hip arthroplasty. Markov decision modeling was used to determine the ceramic-on-polyethylene implant revision rate necessary to be cost-effective compared with the revision rate of metal-on-polyethylene implants across a range of patient ages and implant costs. A different set of Markov models was used to estimate the national cost burden of choosing ceramic-on-polyethylene implants over metal-on-polyethylene implants for primary total hip arthroplasties. The Premier Research Database was used to identify 20,398 patients who in 2012 were ≥45 years of age and underwent a total hip arthroplasty with either a ceramic-on-polyethylene implant or a metal-on-polyethylene implant. The cost-effectiveness of ceramic heads is highly dependent on the cost differential between ceramic and metal femoral heads and the age of the patient. At a cost differential of $325, ceramic-on-polyethylene bearings are cost-effective for patients <85 years of age. At a cost differential of $600, it is cost-effective to utilize ceramic-on-polyethylene bearings in patients <65 years of age, and, at a differential of $1,003, ceramic-on-polyethylene bearings are not cost-effective at any age. The ability to recoup the initial increased expenditure of ceramic heads through a diminished lifetime revision cost is dependent on the price premium for ceramic and the age of the patient. A wholesale switch to ceramic bearings regardless of age or cost differential may result in an economic burden to the health system. Economic and decision analysis, Level III. See Instructions for Authors for a complete description of levels of evidence.

Retrieval analysis of ceramic-coated metal-on-polyethylene total hip replacements.

Ceramic coatings have been used in metal-on-polyethylene (MOP) hips to reduce the risk of wear and also infection; the clinical efficacy of this remains unclear. This retrieval study sought to better understand the performance of coated bearing surfaces. Forty-three coated MOP components were analysed post-retrieval for evidence of coating loss and gross polyethylene wear. Coating loss was graded using a visual semi-quantitative protocol. Evidence of gross polyethylene wear was determined by radiographic analysis and visual inspection of the retrieved implants. All components with gross polyethylene wear (n = 10) were revised due to a malfunctioning acetabular component; 35% (n = 15) of implants exhibited visible coating loss and the incidence of polyethylene wear in samples with coating loss was 54%, significantly (p = 0.02) elevated compared to samples with intact coatings (14%). In this study we found evidence of coating loss on metal femoral heads which was associated with increased wear of the corresponding polyethylene acetabular cups.

Will New Metal Heads Restore Mechanical Integrity of Corroded Trunnions?

BackgroundMetal wear and corrosion from modular junctions in total hip arthroplasty can lead to further unwanted surgery. Trunnion tribocorrosion is recognized as an important contributor to failure. This study was performed to determine if new metal heads restore mechanical integrity of the original modular junction after impaction on corroded trunnions, and assess which variables affect stability of the new interface created at revision total hip arthroplasty. MethodsTwenty-two trunnions, cobalt-chromium (CoCr) and titanium alloy (TiAIV), (CoCr, n = 12; TiAIV, n = 10) and new metal heads were used, 10 trunnions in pristine condition and 12 with corrosion damage. Test states were performed using an MTS Machine and included the following: 1, Assembly; 2, Disassembly; 3, Assembly; 4, Toggling; and 5, Disassembly. During loading, three-dimensional motion of the head-trunnion junction was measured using a custom jig. ResultsThere were no statistical differences in the tested mechanical properties between corroded and pristine trunnions implanted with a new metal femoral head. Average micromotion of the head versus trunnion interface was greatest at the start of loading, stabilizing after approximately 50 loading cycles at an average of 30.6 ± 3.2 μm. ConclusionCorrosion at the trunnion does not disrupt mechanical integrity of the junction when a CoCr head is replaced with a CoCr trunnion. However, increased interface motion of a new metal head on a corroded titanium trunnion requires additional study. The evaluation of ball head size on mechanical integrity of trunnions would also be a potential subject of future investigation, as increasing the ball head size at the time of revision is not uncommon in revisions today.

A Comparison of Blood Metal Ions in Total Hip Arthroplasty Using Metal and Ceramic Heads

BackgroundIn recent time, metal ion debris and adverse local tissue reaction have reemerged as an area of clinical concern with the use of large femoral heads after total hip arthroplasty (THA). MethodsBetween June 2014 and January 2015, 60 patients with a noncemented THA using a titanium (titanium, molybdenum, zirconium, and iron alloy) femoral stem and a V40 trunnion were identified with a minimum 5-year follow-up. All THAs had a 32- or 36-mm metal (n = 30) or ceramic (n = 30) femoral head coupled with highly cross-linked polyethylene. Cobalt, chromium, and nickel ions were measured. ResultsPatients with metal heads had detectable cobalt and chromium levels. Cobalt levels were detectable in 17 (56.7%) patients with a mean of 2.0 μg/L (range: <1.0-10.8 μg/L). Chromium levels were detectable in 5 (16.7%) patients with a mean of 0.3 μg/L (range: <1.0-2.2 μg/L). All patients with a ceramic head had nondetectable cobalt and chromium levels. Cobalt and chromium levels were significantly higher with metal heads compared to ceramic heads (P < .01). Cobalt levels were significantly higher with 36-mm metal heads compared with 32-mm heads (P < .01). Seven patients with metal femoral heads had mild hip symptoms, 4 of whom had positive findings of early adverse local tissue reaction on magnetic resonance imaging. All ceramic THA was asymptomatic. ConclusionThe incidence and magnitude of cobalt and chromium levels is higher in metal heads compared to ceramic heads with this implant system (P < .01). Thirty-six millimeter metal femoral heads result in larger levels of cobalt compared with 32-mm metal heads.

Adverse Local Tissue Reaction in Total Hip Replacement

&lt;p&gt;Total hip replacement (THR) utilizing metal-on-polyethylene articulations was successful for many years. Modifications in materials and implant designs were created to improve wear and allow greater ability to adjust the implant position, optimizing joint mechanics. Three recent cobalt-chromium designs that involve metal to metal contact (metal-on-metal or MoM, modular neck-stems, large metal femoral heads) have produced metal debris through corrosion, releasing cobalt ions around the implant. Unfortunately, these metal nanoparticles have led to a wide spectrum of soft tissue destruction called adverse local tissue reaction (ALTR). This review article assesses ALTR following THR using MoM cobalt-chromium designs, as well as the diagnostic testing used to identify at risk hips. Findings revealed that a possible explanation for ALTR is hypersensitivity to cobalt with lymphocytic perivascular infiltration, known as aseptic lymphocytic vasculitis associated lesion (ALVAL). Solid or cystic masses called “pseudotumors” may also form around the implant. Given the destructive nature of ALTR to the surrounding capsule, muscle, and bone, surgical revision of the MoM junction is generally required. In addition to physical examination and x-rays, diagnosis now depends on drawing serum cobalt and chromium levels, as well as the use of a metal artifact reduction suppression (MARS) MRI.&lt;/p&gt;&lt;p&gt;The authors believe that the optimal design and bearing surface for THR is a titanium femoral stem and acetabulum with a ceramic femoral head (32 or 36 mm) articulating on a polyethylene acetabular insert. Manufacturers have now produced a polyethylene with superior bearing characteristics, as evidenced by minimal wear after five to ten years of implantation. &lt;/p&gt;

Long-term Results of a First-Generation Annealed Highly Cross-Linked Polyethylene in Young, Active Patients.

The survivorship of total hip arthroplasty in younger patients is dependent on the wear characteristics of the bearing surfaces. Long-term results with conventional polyethylene in young patients show a high failure rate. This study assessed the long-term results of a first-generation annealed highly cross-linked polyethylene (HCLPE) in uncemented total hip arthroplasty in young, active patients. Between 1999 and 2003, 112 total hip arthroplasty procedures performed in 91 patients with an average University of California Los Angeles activity score of 8 and mean age of 53 years (range, 24-65 years) were included from a prospective database. In all patients, a 28-mm metal femoral head on annealed HCLPE (Crossfire; Stryker, Mahwah, New Jersey) was used. At minimum 10-year follow-up (11.5±0.94 years), Kaplan-Meier survivorship was 97% for all failures (1 periprosthetic infection and 1 late dislocation) and 100% for mechanical failure (no revisions for osteolysis or loosening). This study showed low revision rates for wear-related failure and superior survivorship in young, active patients. Oxidation causing failure of the locking mechanism has not been a problem with Crossfire for up to 10 years.

Metallosis after Exchange of the Femoral Head and Liner following Ceramic Acetabular Liner Dissociation in Total Hip Arthroplasty with a Modular Layered Acetabular Component

The type of bearing material that should be used in revision surgery after the failure of ceramic-on-ceramic total hip arthroplasty (THA) remains controversial. In the case of ceramic fracture, the residual ceramic particles can cause consequent metallosis when metal implants are used for revision THA. On the other hand, in the case of THA failure without ceramic fracture, revision THA with a metal femoral head provides satisfactory results. We report an unusual case of progressive osteolysis due to metallosis that developed after revision THA for ceramic liner dissociation without a liner fracture performed using a metal femoral head and polyethylene liner. The residual metal debris and abnormal pumping motion of the polyethylene liner due to the breakage of the locking system or the aspherical metal shell being abraded by the ceramic head seemed to be the cause of the progressive osteolysis.

The effect of lubricant constituents on lubrication mechanisms in hip joint replacements

The aim of the present paper is to provide a novel experimental approach enabling to assess the thickness of lubricant film within hip prostheses in meaning of the contribution of particular proteins. Thin film colorimetric interferometry was combined with fluorescent microscopy finding that a combination of optical methods can help to better understand the interfacial lubrication processes in hip replacements. The contact of metal femoral head against a glass disc was investigated under various operating conditions. As a test lubricant, the saline solution containing the albumin and γ-globulin in a concentration 2:1 was employed. Two different mean speeds were applied, 5.7 and 22mm/s, respectively. The measurements were carried out under pure rolling, partial negative and partial positive sliding conditions showing that kinematic conditions substantially affects the formation of protein film. Under pure rolling conditions, an increasing tendency of lubricant film independently on rolling speed was detected, while the total thickness of lubricant film can be attributed mainly to albumin. When the ball was faster than the disc (negative sliding), a very thin lubricant film was observed for lower speed with no significant effect of particular proteins. The increase in sliding speed led to the increase of film thickness mainly caused due to the presence of γ-globulin. On the contrary, when the disc was faster than the ball (positive sliding), the film formation was very complex and time dependent while both of the studied proteins have shown any qualitative change during the test, however the effect of albumin seems to be much more important. Since a very good agreement of the results was obtained, it can be concluded that the approach consisting of two optical methods can provide the fundamental information about the lubricant film formation in meaning of particular proteins while the simultaneous presence of other constituents in model synovial fluid.

May the surface roughness of the retrieved femoral head influence the wear behavior of the polyethylene liner?

This study was aimed at determining the surface degradation occurred on retrieved ceramic and metallic heads, as well as the influence of the head surface quality on the wear of the polyethylene counterface. To this purpose, 14 ceramic and 14 metallic femoral heads retrieved at revision surgery were examined. Scanning electron microscopic analysis provided visual evidence that some metallic heads presented crescent wear more often than the ceramic ones; the former showed a higher volumetric loss (as determined by Coordinate Measuring Machine) than the latter, but less negative Rsk values. This apparent lack of correlation between volumetric loss (i.e., wear factor) and roughness data may be explained by considering that they are two temporally variant parameters. No significant differences were observed between the Ra values of the two sets of femoral heads. The cups articulating against metal heads were characterized by higher mean wear volumes than those articulating against alumina although this difference was not statistically significant; metal heads displayed significantly higher mean wear volumes than alumina heads. The micro-Raman analysis of the cup articulated against the most worn alumina femoral head showed an orthorhombic into monoclinic phase transformation that was not observed in the cups coupled to metal heads. The obtained results showed that the surface finishing of the femoral head (in terms of Rsk values) determined the morphological changes experienced by the ultra-high-molecular-weight polyethylene crystalline phase at the molecular level. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1374-1385, 2016.