Femoral Ball Heads Research Articles

Enhancement the Osseo Integration Properties of Polymer for Human Body Implants

In this research, polymer polymethyl methacrylate PMMA composite with nano ceramic Zr and HAp material were used to manufacture one part of the implant system (femoral ball head of hip implant). Three set of hybrid materials were fabricated and tested for this study; the first mixtures which contains 100% (PMMA), the second mixtures which contains (90% (PMMA) + 8% (Zr) + 2% (HAp)), and the third mixtures which contains (80% (PMMA) + 18% (Zr) + 2% (HAp)) were investigated. The mechanical properties for these mixtures increased with the increasing of nano ceramic concentration (Zr and HAp) composite material in the polymer compared to pure polymer PMMA sample. However, an increase in the concentration of Zr from 8% to 18% content cause a considerable decrease of the hardness where a drop of homogeneity in Zr- matrix PMMA contact occurred, V Hardness value are (68 ,80 and 70) Kg.mm for three mixture respectively. The wear test was in agreement with results of the hardness test. The weight loss of the above samples of the wear test were (0.041, 0.035 and 0.037) respectively. According to mechanical properties, the best sample contains (90% (PMMA) + 8% (Zr) + 2% (HAp)). The Scanning electron microscopy resolute showed the particles forming semi-continuous network along grain boundaries polymer for second sample mixtures containing (90% (PMMA) + 8% (Zr) + 2% (HAp)), provides a low atomic packing and high energy. This will make the grain boundaries more reactive and strengthen mechanical performance. The Optical microscopy, Scanning electron microscopy and Xray spectroscopy analysis for In vitro test using SBF shows the growth of HAp layer with an increase in concentration of Ca and P elements formed on the surface of the second sample. This display of good results is a proof of the biocompatibility of the polymer sample.

Model-Based Roentgen Stereophotogrammetric Analysis to Monitor the Head-Taper Junction in Total Hip Arthroplasty in Vivo-And They Do Move.

Model-based Roentgen stereophotogrammetric analysis (RSA) using elementary geometrical shape (EGS) models allows migration measurement of implants without the necessity of additional attached implant markers. The aims of this study were: (i) to assess the possibility of measuring potential head–taper movement in THA in vivo using model-based RSA and (ii) to prove the validity of measured head–taper migration data in vitro and in vivo. From a previous RSA study with a 10 years follow-up, retrospectively for n = 45 patients head–taper migration was calculated as the relative migration between femoral ball head and taper of the femoral stem using model-based RSA. A head–taper migration of 0.026 mm/year can be detected with available RSA technology. In vitro validation showed a total migration of 268 ± 11 µm along the taper axis in a similar range to what has been reported using the RSA method. In vivo, a proof for interchangeable applicability of model-based RSA (EGS) and standard marker-based RSA methods was indicated by a significant deviation within the migration result after 12-month follow-up for all translation measurements, which was significantly correlated to the measured head–taper migration (r from 0.40 to 0.67; p < 0.05). The results identified that model-based RSA (EGS) could be used to detect head–taper migration in vivo and the measured movement could be validated in vitro and in vivo as well. Those findings supported the possibility of applying RSA for helping evaluate the head–taper corrosion related failure (trunnionosis).

Influence of femoral head diameter on intraoperative range of motion in total hip arthroplasty

PurposeTo investigate the intraoperative change of range of motion (ROM) using different femoral ball head diameters in the same patient using a navigation system and to compare the postoperative ROM speculated by 3D computer simulation software and the actual intraoperative ROM. Materials and methodsFourteen patients (12 female and 2 male patients) who underwent one-sided primary total hip arthroplasty for hip osteoarthritis caused by developmental dysplasia of the hip from January 2016 to November 2017 were included. Dislocation was defined as the center of femoral head moved by 5 mm. After placing the cup and stem via the posterolateral approach, measurement of the ROM with 28-, 32-, and 36-mm-diameter femoral ball heads was carried out using the navigation system. Postoperative computed tomography (CT) was performed, and the ROM simulation of the same movement was measured intraoperatively using a small-sized ball head (ZedHip). ResultsThe intraoperative ROM was approximately closed to the preoperative ROM, and it tended to be in the following order: preoperative<28-mm head<32-mm head. As the diameter of the femoral head increased, the abduction increased significantly (p < 0.05). None reached 80% of the ROM simulated by ZedHip, and the movements that obtained 50% or more in the simulated ROM were flexion, abduction, and the angle until the dislocation. ConclusionsROM expansion due to the increase in femoral ball head diameter can be obtained even in vivo, but it was suggested that there is a limitation to the effect because of the interference of bone and soft tissue.

ZrO2-toughened Al2O3-based near-net shaped femoral head: Unique fabrication approach, 3D microstructure, burst strength and muscle cell response

The development of reliable biomedical devices demands the use of an integrated manufacturing protocol with comprehensive understanding of prototype characterization in terms of 3D microstructural analysis along with biocompatibility. While addressing these issues for ZrO2 (3mol% Y2O3 stabilized)-toughened Al2O3-based femoral head prototypes, the present work reports a unique fabrication protocol involving a sequence of uniaxial compaction followed by pre-sintering, machining, final sintering and polishing to ensure dimensional tolerance with respect to the design of patient-specific femoral head. The prototypes are characterized by a clinically relevant surface finish (Ra ~0.2μm) with good geometric circularity (±50μm). Extensive μCT analysis at different regions of interest confirms a homogeneous distribution and 3D spatial orientation of ZrO2 across the volume of the defect-free prototype. Further, an in vitro cell culture with a murine myoblast cell line (C2C12) over a period of 72h showed an increase in the number of mitochondrially-active cells and good cellular attachment with oriented cellular bridge formation, which confirms the excellent cytocompatibility. The as-machined ZTA femoral heads fracture at a load of 15.3kN during burst tests, conducted following ISO guidelines. Taken together, this novel fabrication approach can be effectively utilised in the development of near-net shaped bioceramic-based femoral ball heads.

FRETTING CORROSION OF COBALT AND TITANIUM IMPLANT ALLOYS IN SIMULATED BODY FLUIDS

The most important advantage of using modular hip joint endoprostheses is the possibility to adapt the endoprosthesis to the morphology and size of individual patients. However, the additional contact surface is subjected to fretting wear due to mutual micro displacements and the aggressive chemistry of the environment inside the human body (fretting corrosion). Today’s hip endoprostheses are generally composed of a hip stem, a femoral ball head and an acetabular cup (Figure 1). The hip stem is made of stainless steel, CoCrMo or a Ti alloys. The femoral ball head is made of stainless steel, CoCrMo, or a ceramic material. In the case of a modular hip stem, i.e. with a modular neck portion, the materials used are generally CoCrMo and Ti6Al 4V. (The interface between femoral ball head and the acetabular cup is an articulating surface and not the subject of this research project.) In this framework, a comparative study of the fretting corrosion resistance of the three most common metallic material combinations occurring in a modular, the non-articulating connection of total hip joint endoprostheses (CoCrMo-CoCrMo, CoCrMo-Ti6Al4V, and Ti6Al4V-Ti6Al4V) was undertaken. Studies were performed with a tribological tester, working in articulating-reciprocating motion, integrated with a potentiostat equipped with a tri-electrode system. The tribosystem consisted of a fixed stem pressed with a constant force to a plate performing the reciprocating motion of a predetermined frequency and amplitude. The tests were performed in diluted bovine serum at 37°C. Based on the obtained results, it was found that the greatest resistance to corrosion in static conditions was exhibited by the CoCrMo-CoCrMo friction pair, while the lowest ΔE value was obtained by CoCrMo-Ti6Al4V. It also confirmed the existence of a correlation between the intensity of the depassivation process caused by the mechanical destruction of the surface layer and the friction resistance values in the tribological system.

Incidence of Modern Alumina Ceramic and Alumina Matrix Composite Femoral Head Failures in Nearly 6 Million Hip Implants

BackgroundBecause of improvements in ceramic materials and manufacturing, the incidence of ceramic failures has decreased over time. Recent concerns with corrosion have contributed to an increase in ceramic ball head utilization. The purpose of this study is to report the incidence of modern alumina bearing failures from a single major ceramic manufacturer in nearly 6 million hip implants and to identify trends in the modes of failure of these implants. MethodsBeginning in the year 2000, CeramTec AG (Plochingen, Germany) began a comprehensive program for reporting and gathering failure data on its products. From January 1, 2000, to December 31, 2013, over 3.2 million pure alumina (PA) and 2.78 million alumina matrix composite (AMC) ceramic ball heads were implanted worldwide. During this period, there were 672 PA and 28 AMC femoral head fractures. The fractures were analyzed with respect to time to failure, head size, and implant factors. ResultsThe incidence of clinical fractures of modern PA femoral heads and AMC femoral heads was 1 in 5000 (0.0201%) and 1 in 100,000 (0.0010%), respectively (P < .0001). The majority of implant failures (80%) occurred within 48 months following surgery (P < .01). Fractures were usually associated with specific events such as trauma, mismatched components, and dislocations. Large-diameter PA heads were associated with a lower rate of fracture compared to smaller-diameter femoral heads (0.0316% for 28-mm heads vs 0.0080% for heads 32 mm or greater [P < .01]). Similar trends were observed with AMC heads. The neck lengths of the femoral ball heads were also a factor: a short-taper 28-mm ball head was more likely to fracture compared to other neck lengths (P < .01). ConclusionModern PA ceramic heads are reliable with extremely low risk of fracture. The reliability is even better with AMC heads.

Primary Total Hip Arthroplasty With Fourth-Generation Ceramic-on-Ceramic: Analysis of Complications in 939 Consecutive Cases Followed for 2-10 Years

BackgroundDelta ceramics may be the bearing of choice for younger and active patients due to its improved toughness and wear characteristics, provided there is no risk of fracture. However, ceramic fracture is the most serious complication related to this type of bearing. Although millions of Delta ceramics have been implanted worldwide, short to midterm results have been scarcely reported in the literature. The purpose of this study was to report the complication rate at short to midterm follow-up associated with the bearing surface used in a series of primary total hip arthroplasties with Delta ceramic-on-ceramic bearings performed in a single institution. MethodsA total of 939 cases (880 patients) undergoing primary total hip arthroplasty with fourth-generation Delta ceramic-on-ceramic bearings were retrospectively reviewed. They were followed for an average of 5.3 years (2-10 years). ResultsOne hip experienced a liner fracture, 2 cups presented early loosening due to friction between the acetabular screw and the backside of the liner, one femoral ball head had a fracture; one case of squeaking was reported, which is impending revision. Considering revision or impending revision in relationship with the bearing surface as the end point, the mean survival rate was 99.3% (confidence interval 95%, 98.3%-99.7%) at 2-10 years. ConclusionThis study showed a low rate of ceramic fracture compared with others; however, it was much higher than the complication rate presented by the manufacturers. The complications observed were directly related to technical errors that surgeons should avoid when using this type of surface.

Are asymmetric metal markings on the cone surface of ceramic femoral heads an indication of entrapped debris?

BackgroundThe probability of in vivo failure of ceramic hip joint implants is very low (0.004-0.05%). In addition to material flaws and overloading, improper handling during implantation can induce fractures of the ceramic ball head in the long term. Identifying the causes of an in vivo fracture contributes to improved understanding and potentially to further reduction of the fracture probability for patients. Asymmetric metal markings on the cone surface of in vivo ball head fractures have been reported. The question, therefore, is whether asymmetric loading is the sole cause or whether additional factors, specifically contamination entrapped in the taper fit, also contribute or are even the main cause.MethodsThe influence of the asymmetric physiological load configuration on resulting metal markings in the cone surface of an alumina femoral ball head with and without biological contaminants was investigated. Static and cyclic tests on ball heads were carried out in a load configuration of 0° (axisymmetric) and 40° in a physiological environment. The analysis of the metal marking was carried out to gain a better understanding of the processes that contribute to the generation of metal marking. Fractography was carried out to determine the fracture initiation of failed ball heads.ResultsDifferent types and sizes of residuals entrapped in the conical surface are shown to yield strongly asymmetric metal marking patterns. All heads tested without contaminants exhibited an almost homogenous distribution of residual metal markings around the circumference of the ceramic cone surface at the proximal end of the bore hole. The failure of ball heads that contained entrapped contaminants revealed a common fracture pattern. The site of fracture initiation on two of the failed heads was in the entrance region of the bore hole on the superior half of the head.ConclusionAsymmetric metal markings observed on the ball heads tested in this investigation are most probably caused by the presence of contaminants entrapped in the taper fit. Homogenous metal mark distributions around the circumference indicate proper assembly of the ball head without entrapped contaminants. It should, however, be noted that different taper designs may possibly result in different marking patterns.

What an Orthopedic Surgeon Should Know: Selection of a Bearing Couple in Case of Revision After a Fractured Ceramic Component

Revision surgery for fractured ceramic components in total hip arthroplasty (THA) potentially leaves small ceramic fragments in the joint capsule, and the fragments might become embedded in polyethylene (PE) acetabular liners. The purpose of this study was to determine the wear behavior of metal femoral ball heads and ceramic femoral ball heads tested with highly cross-linked and conventional polyethylene liners in the presence of ceramic debris. A worst-case scenario, assuming embedding of ceramic fragments in the PE liner, contamination of the test environment with third-body ceramic debris and continuous subluxation, was simulated in vitro. High wear rates were found for metal femoral ball heads, being 1,010 times higher when compared to ceramic femoral ball heads tested with XPE liners and 560 times higher when compared to ceramic femoral ball heads tested with PE liners. The test results indicate the use of ceramic femoral ball heads for revision surgery in the presence of ceramic fragments.

Ceramic Versus Metal Femoral Heads in Combination With Polyethylene Cups: Long-Term Wear Analysis at 20 Years

Bearing surfaces are an important implant-related factor in the process of wear and resulting osteolysis. Especially, polyethylene (PE) wear is known to be a major reason for aseptic loosening of the acetabular and femoral components in total hip replacement (THR). In the past, several studies showed the advantages of ceramic femoral ball heads compared with metal ball heads with respect to the resulting PE wear. In this framework, we posed the question whether ceramic and metal ball heads still resulted in similar clinical outcome regarding PE wear after 20-year follow-up. Additionally, we investigated whether wear and osteolysis were correlated within these groups and compared our findings with results from appropriate publications. In this prospective study, 93 nonselected, consecutive uncemented hip arthroplasties were performed in 80 patients with use of the titanium-coated Robert Mathys (RM) cup and the cementless Spotorno stem. Eighty ceramic and 13 metal femoral heads with a diameter of 32 mm were used. The mean age of the patients was 52 years. The average follow-up was 19.3 years. No patient was lost for follow-up. The metal group showed a mean wear rate of 0.190 mm/year, whereas the ceramic group had 0.107 mm/year ( P = 0.025). The rate of revision cases was clearly higher within the CoCrMo group showing 6 revisions in 13 cases (46.2%) compared with 11 in 80 cases (13.8%) within the ceramic group. Wear rates were positively correlated to femoral head material ( P = 0.025), stem osteolysis ( P = 0.003), cup osteolysis ( P = 0.011), cup revision ( P = 0.041), and cup inclination ( P = 0.012). This long-term study shows that during a period of 20 years, ceramic ball heads generate less linear PE wear compared with metal ball heads, thus causing significantly less osteolysis and revisions of either component.

Electrophoretic Deposition as a Novel Near Net Shaping Technique for Functionally Graded Biomaterials

Complex shaped functionally graded alumina and zirconia based femoral ball-heads for biomedical applications were shaped by electrophoretic deposition (EPD). A composition gradient in alumina and zirconia was engineered to obtain a pure alumina surface region and a homogeneous alumina/zirconia core with intermediate continuously graded regions to generate appropriate thermal residual stresses after sintering. The gradient profiles were designed to obtain maximum compressive surface stresses and minimal tensile stresses in the core of the component to increase the strength and wear properties when compared to pure alumina components.

Alumina ceramic bearings for hip endoprostheses: the Austrian experiences.

The current authors review clinical and retrieval experiences with hemispheric monolithic alumina ceramic sockets (Group 1), implanted between 1976 and 1979, and similar modular titanium sockets with alumina ceramic inlays (Group 2), implanted between 1990 and 1995. Both cementless sockets articulated with alumina ceramic femoral ball heads for total hip joint replacements. Clinical followup of patients with hemispheric monolithic alumina ceramic sockets (Group 1, 138 sockets) resulted in a total failure rate of 19.6% after 5 to 20 years. Radiologic analysis of eight stable sockets showed migration of 0.2 mm to 2.89 mm, but in four sockets at risk for late aseptic failure after an average followup of 12.5 years as much as 13.4 mm of migration was seen. Histologic evaluation revealed pseudosynovial membranes as thick as 1 mm with fine birefringent wear particles within mononuclear macrophages around two stable retrieved sockets. The membranes around four loose sockets were 6 to 10 mm thick and also heavily loaded with larger alumina wear particles. After 7 years followup clinical analysis of patients with modular titanium sockets with alumina ceramic inlays (Group 2, 30 sockets) resulted in four revisions, compared with one revision of 50 identical sockets (control group) with polyethylene instead of alumina ceramic inlays. Wear particle analyses in scanning electron microscopy showed significantly more particles (x 10(9) +/- standard deviation/g dry tissue) from the control group (4.26+/-6.38), compared with alumina ceramic bearings of Group 1 (0.70+/-0.79), and of Group 2 (1.62+/-2.13). The alumina particle sizes ranged between 0.13 and 78.38 microm. The mean annual linear wear of 38.8 microm was calculated for the bearings in Group 1, and of 26.94 microm for bearings in Group 2. These results support the good tribologic and biologic performance of alumina ceramic bearings for total hip arthroplasty.

Bacterial adhesion to femoral ballhead surfaces of artificial hipjoints in vitro

In orthopedic surgery one of the most significant complications is the infection of implants by microorganisms. The purpose of this study was to investigate whether an adhesion of microbes to femoral ballheads consisting of aluminium oxide, zirconium oxide and CoCrMo-alloy is possible, especially to the smoothly polished surface, and whether this implant component might play a role in respect of the mode of infection. The femoral ballheads were contaminated with strains of Staphylococcus aureus and exopolysaccharide producing Staphylococcus epidermidis and incubated in two fractions for 36 and 72 hours. The present experiment documents that the strains of microorganisms tested adhere well to all ballheads used. However, the surfaces of the zirconium oxide ballheads manifest the most pronounced bacterial lawn with the strains investigated.In comparison to aluminium oxide ballheads which also show several layers of colonisation over large areas, these are overgrown with plate-like microbial lawns. Due to the surface tension and surface energy the microbial adhesion is found on metal (CoCrMo-alloy) ballheads initially in small rounded areas with tendency to confluence.

Reliability of ceramic components for total hip endoprostheses

AbstractThe material and component requirements for ceramic femoral ball heads in total hip replacement systems are described and briefly discussed. Reliability is correlated to the homogeneity of the material in terms of microstructure and Weibull modulus, and to the design of the components. Stress distribution can be analysed by finite element analysis. Based on controlled and specialised processing and the stress analysis data the design can be optimised. Proof testing, as part of final inspection, is an efficient method for eliminating components having strengths at the low end of the strength distribution spectrum.

Wear characteristics of ceramic-on-ceramic for hip endoprostheses

Femoral ball heads of aluminium oxide or zirconium oxide ceramics are used for total hip replacement. This application is based on their attractive tribological properties. Standard and state-of-the-art are femoral ball heads made of alumina (Al 2O 3) articulating against acetabular cups of polyethylene (PE-UHMW) and zirconia (Y-TZP) heads articulating against polyethylene cups. A very attractive wear couple is ceramic-on-ceramic. Some of the various ceramic combinations have been tested using the ring-on-disc method according to ISO 6474. The combination alumina/alumina was found to produce extremely low wear; catastrophic wear was found for the combinations alumina/Y-TZP and Y-TZP/Y-TZP.

Wear characteristics of sliding pairs of zirconia (Y-TZP) for hip endoprostheses

Femoral ball heads made of aluminium or zirconium oxide ceramics are used for total hip replacement. This application is based on their attractive tribological properties. Standard and state-of-the-art with good wear properties are femoral ball heads made of alumina (Al2O3) articulating against polyethylene (PE-UHMW) acetabular cups (since 1974) and zirconia (Y-TZP) heads articulating against polyethylene cups (since 1986). The best tribological combinations are alumina heads articulating against alumina cups. Zirconia has better mechanical properties (for example, bending strength or fracture toughness) than alumina. Therefore R&D is going on to design zirconia acetabular cups. The wear characteristics of zirconia (Y-TZP) articulating against itself were investigated using a ring-on-disc testing device according to ISO 6474. The high wear rate emphasized that medical-grade zirconia (Y-TZP according to ISO/ DIS 13356) should not be used for acetabular cups.

The colour of medical-grade zirconia (Y-TZP)

Optical spectroscopy, ESR spectroscopy, and standard and wavelength- and-temperature-resolved thermoluminenscence spectroscopy of as-sintered and γ-irradiated medical-grade yttrium-stabilized tetragonal zirconia polycrystal (Y-TZP) material showed that the pronounced colour change, after irradiation, from off-white to a purplish-grey shade can be related to two electronic transitions at local defects in the crystal lattice. The first transition could be associated with an electron-hole state characterized by an oxygen ion trapped in the vicinity of a yttrium ion (Y'ZrO*) and can be correlated with an optical absorption band at 2.6 eV (480 nm). The second transition is presumably an extrinsic defect correlated with an optical absorption band at 3.2 eV (395 nm). From the experimental results it can be concluded that those local electronic defects responsible for the colour change on γ-irradiation do not influence safety-related mechanical or chemical properties of the ceramic femoral ball heads of hip endoprostheses produced from Y-TZP.

Development in medical-grade alumina during the past two decades

Medical-grade alumina (Al 2O 3) ceramic has been used in various clinical applications for the past two decades. The primary applications have been in orthopedic and dental implants. The most successful application is the femoral ball head for hip endoprostheses. Up to May 1993 more than 2 million heads have been used worldwide. The following topics will be discussed: Properties and design of ceramic femoral ball heads for total hip replacement (THR), safety factors, standards and government regulations, and future development.

Increasing the safety of ceramic femoral heads for hip prostheses

Since 1974 Biolox ceramic femoral ball heads have been used successfully for artificial modular hip joints. The revision rate due to ball head fracture is lower than 0.02%. This is an extremely low value. In this article it is shown how the safety of a ceramic ball head can be improved using the procedures of HIPing, engraving by laser technique, and 100% proof testing. By applying these means the materials properties density, grain size, grain size distribution, and the strength of the ball head, i.e. the fracture load can be improved significantly.

Investigations into the mechanical reliability of ceramic femoral heads for hip joints

This paper reports the findings of a finite element analysis applied to the study of ceramic femoral ball heads. The objective of carrying out these analyses was to assess the shape design and loading conditions applied to specific femoral heads and to capture the stress fields developed when they are subjected to idealized test conditions. Two designs were considered, these being the existing Biolox keyhole shape, manufactured by Cerasiv, Medical Products Division and an alternative design with a flat top internal hole. For each of these designs, three load cases and two types of frictional contact were considered. It is shown that the key hole shape with full taper contact conditions together with the higher value of surface friction produce the lowest tensile stress fields in the ball head hence increasing mechanical reliability.