Introduction and Objective. Despite pure alumina have shown excellent long-term results in patients undergoing total hip arthroplasty (THA), alumina matrix composites (AMCs) composed of alumina and zirconium oxide are more commonly used. There are no comparative studies between these two different ceramics. We performed a retrospective case-control study to compare results and associated complications between AMC from two manufacturers and those with pure alumina from another manufacturer. Materials and Methods. 480 uncemented THAs with ceramic on ceramic (CoC) bearing surfaces (288 men and 192 women; mean age of 54.1 ± 12.4 years), were implanted from 2010 to 2015. Group 1: 281 THAs with pure alumina; Group 2A: 142 with AMC bearing in a trabecular titanium cup. Group 2B: 57 hips with AMC bearing with a porous-coated cup. Results. The mean follow-up was 7.3 years. There was one late infection in group 1, eight dislocations, three in group 1 (1.1%), three in group 2A (2.1%), all with a 36 mm femoral head, and two in group 2C (3.5%). Liner malseating was found in one hip in group 1, and in five hips in group 2C, of these, there were four liner fractures (7.0%). Four cups were revised for iliopsoas impingement (three in group 1 and one in group 2B). Two cups were revised for aseptic loosening, one in group 1 and one in group 2A, and four revised femoral stems in group 2A, three for subsidence and another for postoperative periprosthetic B. 2. fracture. The mean preoperative Harris Hip Score was 48.6 ± 3.3 in the whole series and 93.9 ± 7.2 at the end of follow-up. The survival rate of revision for any cause was 98.2% (95% Confidence Interval: 96.6–99.8) at ten years for group 1, 95.8% (95% CI: 92.1–99.5) for group 2A, and 91.1% (95% CI: 83.7–98.5) for group 2B (log-rank 0.030). Conclusions. Outcome of uncemented CoC THA in young patients was satisfactory at mid-term in all three groups. However, liner fractures were frequent in group 2B. All dislocated hips in group 2A had a 36 mm femoral head diameter, and revision due to any cause was less frequent in group 1. Pure alumina CoC THA can be used as a benchmark for comparison with newer CoC THAs

Mechanical failure in total hip arthroplasty is usually due to aseptic loosening related to wear particles as seen with polyethylene bearing. Alumina has been proposed for avoiding wear problems. In vitro and mid-term clinical studies showed tribological advantages but early acetabular fixation issues. Since alumina on alumina bearing is currently used with new fixation techniques, updated evaluations of the ancient series are informative regarding the long-term tolerance of alumina in vivo. In this paper, we investigated 104 consecutive lumina on alumina cemented total hip arthroplasties (CER-VAER-OSTEAL, Roissy, France) implanted 20 years ago in 81 patients (from 1979 to 1983). Alumina femoral head was 32 mm in diameter. Alumina acetabular socket and titanium femoral stem were cemented. The clinical evaluation used Postel Merle d’Aubigné score. Radiological wear and appearance of osteolysis or loosening were noted for establishing actuarial curves. When accessible, histological samples from revision procedures were analyzed. Six infected cases were not taken into account later. The average follow-up was 11 years, reaching 18 years in 38 cases. Twenty-three hip were revised for changing 23 acetabular sockets, 12 femoral heads, and 1 femoral stem. We noted 1 femoral head fracture, 24 definite ace-tabular loosenings, 12 probable acetabular loosenings, and 3 definite femoral loosenings. Radiological acetabular osteolysis was present in 4 cases, always limited to De Lee zone 1, and associated with loosening. Radiological wear was below eye detection. Peri-prosthetic tissue showed non-specific histological reaction to cement particles. Survival rate at 20 years was 61.4% in term of revision (57.1% and 95.2% concerning acetabular and femoral defininte loosening). Beside the high rate of cemented fixation failure of the socket, loosened and non loosend cases showed an excellent tolerance of alumina on alumina bearing in the long-term, with minimal wear and osteolysis. This may also have protected the femoral component from complications

Introduction: Ceramic/ceramic articulation has a long history and is accepted as a low wear couple for total hip joint application. Due to the requirements for strength of the ball-head it may be necessary to combine products from different Alumina manufacturers. Material and methods: Alumina components according to ISO 6474 for commercial hip joint prosthesis were obtained from 3 sources and subjected to a series of simulator tests up to 5 million cycles. Variations were the type of testing and the quality and type of the Alumina. Wear tests were performed with two different types of simulators and different protocols also including micro-separation testing. Wear was characterised by weight loss, change in surface appearance and particle analysis. Results: Standard wear testing yielded very low wear rates below 0.5 mm3 per million cycles for the Alumina combinations of the third generation with a running in period and a steady state wear after 1 million cycles. Increasing the inclination of the cup up to 60° did not increase the wear rate. Mixing the components from various sources did not affect the wear rate significantly. Micro-separation testing increased the overall wear rate significantly and showed clinical relevant patterns with grain pullout and grain relieve. After a running in period a steady state without “avalanche” effect was observed again. The particle analysis compared favourably with retrieval studies. Although the wear rate was lower for the mixed couples it was statistically not significant. Conclusion: An improved test method for ceramics demonstrates clinically relevant wear in respect of amount, appearance and particle size. The new generation Alumina is more wear resistant and less sensitive to cup position and to micro-separation. Mixing of Alumina components from a single implant manufacturer does not change the low wear rates of ceramic/ceramic articulation and can, therefore, be applied

Aims: To compare acetabular surface treatments in alumina on alumina clinical trial. Methods: Utilizing new improved alumina ceramic materials and implant design, 514 hips were implanted in a US IDE prospective randomized study. All patients received the same press-þt hydroxylapatite-coated (HA) femoral stem. Two-thirds (349 hips) received an alumina ceramic bearing surface, while one-third (165 hips) received a cobalt chrome on polyethylene bearing. The alumina group was further divided with approximately one-half receiving a porous-coated titanium shell and alumina insert (172 hips Ð System I), and one-half receiving an arc deposited titanium shell with HA coating and alumina insert (177 hips Ð System II). System III, the control group, had a porous-coated titanium shell and polyethylene insert. All acetabular shells were of identical external geometry. Results: At latest follow-up, minimum 2 years (2–4 year range), differences were noted in the pattern of development of radiolucent lines around the acetabular components. Radiolucent lines were noted most commonly in De Lee Charnley Zone 3 in porous-coated shells (25/164 hips Ð System I, 33/151 hips Ð System III respectively). Radiolucent lines in Zone 3 were absent in the arc deposited with HA shells (System II) (p=0.001). Conclusions: These results appear to demonstrate that PSL style cups with arc dep and HA coating may improve levels of primary þxation versus that of porous-coated acetabular components

In order to avoid the consequences of polyethylene wear in a high-risk population, 128 alumina-alumina total hip arthroplasty were implanted in 116 consecutive patients of 40 years old or less. Osteonecrosis and sequellae of congenital hip dislocation were the main etiologies representing 71% of the hips. The same titanium alloy cemented stem was implanted in all hips. Four alumina acetabular component fixations were used: cemented plain alumina socket (41 hips), screw-in ring with an alumina insert (22 hips), a press-fit plain alumina socket (32 hips) and a press-fit titanium metal back with an alumina insert (33 hips). Eight patients (11 hips) died during the follow-up period. Sixteen revisions were documented, 12 for ace-tabular aseptic loosening, 3 for bipolar loosening (2 were septic), and 1 for unexplained pain. Eighty-nine hips were followed radiologically for two to twenty years. No femoral nor acetabular osteolysis were observed with an average follow-up of 8.4 years. Wear was unmeasurable. Four additional sockets showed definite migration. The respective survival rate at 7 years were 91.4% for the cemented cup, 88.8% for the screw-in ring, 95.1% for cementless press-fit plain alumina socket and 94.3% for the metal-back press-fit component. The ten-year survival rate was 88.0% for the cemented socket and 88.8% for the screw-in ring. The fifteen-year survival rate was 76.7% for the cemented socket. The occurrence of a graft was the only prognostic factor with a 62.6% survival rate at ten years for the grafted hips and a 90.1% for the non-grafted hips (p=0.004). The alumina-alumina bearing surfaces for young patients appeared as a valuable alternative to standard metal-polyethylene system. There is a need to improve socket fixation if we want to have a survival of the arthroplasty as long as the life expectancy of this increasing and demanding population. The last design with a fully coated HA titanium shell and an alumina liner seems to fulfill the requirements

On a theorethical basis a larger head diameter permit ewider range of motion and enhance the stability of the implant, reducing the risk of dislocation but increasing the level of friction and the production of debris. The need for a small head diameter (22 or 28 mm) was thus storically connected to the behaviour of the metal-polyethilene interface and the problem of PE debris. After the introduction of ceramics the production of debris diminished but the technology didn’t permit diameter-wider than 28 – 32 mm. The development of new ceramics with improved mechanical properties permit now to obtain thinner acetabular inserts and thus a larger head diameter, without increases the production of debris. From september 2003 to jenuary 2004 we have implanted 20 uncemented alumina on alumina THR with an head diameter of 36mm. The diagnosis was: hip fracture (14 cases) and hip osteoarthritis in 6cases. The mean age at operation was 73 years (52–88).. The mean follow-uptime was 5 months (3–8) The study is focused on preliminary observation about early complication. All the patients at the last follow-up have regained complete authonomy during the normal day life activity We have had only one early dislocation, occurred in the 5th post-op day, with the patient in sitting position. After reduction (under anesthesia) and partial immobilization for3 weeks in hip-spica cast there was not recurrence of the dislocation. No other complications were noted. One of the major problem regarding theutilization af alumina in hip arthroplasty is an higher risk of dislocation of the implant. The introduction of a new ceramic with improved mechanical properties that permit larger head size should minimize this risk. This fact, associated to the low production of debris of the alumina bearing-surfaces open new prospective in performing THR

The study was designed to compare the clinical performance of an Alumina ceramic acetabular bearing to that of a polyethylene bearing in a cementless hip couple. The study group consisted of 15 surgeons who performed 308 total hip replacements (297 patients) between January 29, 1998 and February 1, 2000. All patients received a porous coated cementless titanium stem with an Alumina ceramic 28 mm or 32 mm head. Patients were randomized to receive a porous titanium acetabular shell with either a polyethylene or Alumina cup liner. There were 164 Alumina cups and 144 polyethylene cups. The mean age was 57.3 years and consisted of 50% males and 50% females. The preoperative diagnoses were: osteoarthritis 69.8%, avascular necrosis 19.5 %, post traumatic arthritis 2.9 %, inflammatory arthritis 3.9% and other 3.9%. The mean follow up was 12 months. The longest follow up was 38 months. The Harris Hip Score was good and excellent in 86% of the control patients and 87% of the study patients. There has been 100% follow up and survivorship. There were two reoperations for recurrent dislocations in each group. There were no Alumina component fractures, no progressive radiolucencies and no evidence of rapid wear. In the short term follow-up between 12 and 38 months, there do not appear to be any differences between the patients with a bearing couple consisting of Alumina on plastic with those consisting of Alumina on Alumina. There have been no catastrophic failures of the ceramic components. The Alumina/Alumina bearing couple for total hip arthroplasty appears to be an excellent alternative bearing, providing the advantage of improved long term wear and a reduced incidence of polyethylene induced osteolysis

Introduction and purpose: Different bearing surfaces have been used to prevent osteolysis, such as alumina-alumina. We present here an analysis of the results of a prospective multi-center study of complications related to the use of alumina-alumina bearings. Materials and methods: In 4 hospitals 319 cups with hydroxyapatite stems and alumina-alumina bearing surfaces were implanted with a mean follow-up of 5.6 years (range: 3–8). The mean age of the patients was 52.7 (range: 14–70). Alumina wear was calculated by means of a special program. Results: Revision was performed of 5 cups and 2 stems. In one hip with a horizontal acetabular angle (35°) and a thin alumina liner (size 50/32), an acetabular liner fracture occurred 36 months after surgery. The probability of not undergoing revision due to any cause was 96.9% (CI 95%:94.7–99.1%). None of the patients reported any type of noise. All the non-revised cases showed good results both on clinical and X-ray exam at the end of the follow-up. The difference between the center of the head of the femur and the center of the head of the cup at 6 weeks after surgery was −2.45+0.53 mm, with no further changes seen during the follow-up. Conclusions: These data suggest that the prosthetic alumina-alumina bearing surface has excellent results over 5 years and that alumina fractures are infrequent. No changes were seen in terms of the penetration of the femoral head in any case. Longer follow-ups are necessary to determine if the reduction of wear translates into less osteolysis and loosening

The use of a total hip arthroplasty with alumina on alumina bearing couple should limit the risk of wear and secondary osteolysis. From June 1999 to December 2002, we have realised a continuous series of 265 ABGII cementless THA with Alumina bearing. The average age was 58 years (22–78 years). The main causes were osteoarthritis (81%) and osteonecrosis (13%). The operation was performed through a posterior standard approach. In all cases, an anatomic cementless ABG II stem and an acetabular cementless ABG II cup were implanted. The bearing couple was always Alumina Biolox Forte with a 28 mm femoral head in 99% of cases. To date, 12 patients died and 17 patients were lost to follow up (6.4%). 224 patients (232 hips) had a regular clinical and radiological follow-up. The mean follow up was 8.5 years (5–11 years). 9 patients were revised for septic loosening (4cases), femoral fracture (4 cases) and inveterate dislocation (1 case). There was no aseptic loosening. The overall survival rate at more than 10 years is 96.6%. We deplore 2 cases of postoperative dislocation. In this series, we did not observe any breakage of ceramic implant. The clinical and functional outcome is good and stable over time with an average PMA score at 17.6 and an average Harris score at 97.3. 16 patients reported at least one or more episode of abnormal noise “Squeaking” type (6%). It is most often a mild noise and it occurs in a static bending position. This noise disappeared with time in 10 cases. It never necessitated a prosthetic revision. The radiological control does not show any wear. There is no evidence of acetabular or femoral osteolysis. The radiological implant fixation according to the Engh and ARA criteria was good and stable in all cases. This series demonstrate that the implantation of an anatomic cementless HA arthroplasty with an alumina bearing in a young and active patient prevents the risk of wear and osteolysis and improves durability over time. The use of a 28 mm head does not increase the risk of instability and we did not observe failure of the ceramic implants

Purpose. Primary total hip arthroplasty (THA) has been a very successful surgical intervention for the management of end-stage arthritis in geriatric patients (> age 65). The mid- to long-term results have been less satisfactory however, in younger patients primarily due to the wear of the acetabular liner and loosening of the femoral component. The primary study purpose was to compare pain, function and stiffness over the first five years in a population less than 60 years of age who received either an alumina liner/alumina femoral head (alumina group) or a crossfire UHMWPE liner/alumina head (Poly group) following primary THA. Secondarily, we compared re-operation rates over five years between these two groups. Method. This was a randomized, controlled clinical trial of subjects with non-inflammatory OA who were booked for primary THA and consented to participate in the study. Subjects were evaluated pre-operatively and again at one and five years post-operatively by an evaluator who was blinded to group allocation. At each assessment, subjects completed the WOMAC Osteoarthritis Index (WOMAC); complications and re-operations were also recorded. All analyses were performed on an intention to treat basis. Results. 92 subjects were enrolled in the study. The mean age of subjects was 52.4 (SD 6.8) and 50 (54%) were male and was similar between groups (p>0.10). Baseline pain, function and stiffness as measured by the WOMAC were also similar between groups (p>0.48). Five-year follow-up data was available for 78 (85%) patients. Both groups showed substantial improvement in pain, function and stiffness within one year that was maintained out to five years post-operatively; there were no statistically significant differences between groups (p>0.50). Four subjects required re-operation within five years; no re-operation was related to liner type two cases were dislocation due to the malposition of the cup while the remaining two re-operations occurred in the immediate post-operative period for removal of hematoma. Conclusion. Our prospective randomized controlled trial showed substantial post-operative improvements in pain, stiffness, and function that were maintained out to five years, with no statistically significant differences seen between the two groups. No re-operations that were related to the liner type occurred in the first five post-operative years

Expecting the low wear property and the longevity, since October 1998, we have been using the alumina on alumina bearing for the hip arthroplasty. Until July 2008, for dysplastic 1078 hips we have implanted the bearing couple. Among them, we evaluated 86 hips in 79 patients (male 3, female 76) with the primary arthroplasty, Spongiosa Metal II Total Hip System (GHE: ESKA implants, Lübeck, Germany/Biolox Forte. ®. : Ceramtec AG, Plochingen, Germany), osteoarthritis secondary to developmental dysplasia, age 60 or below, and a minimum of five years follow-up. The preoperative diagnosis included the failed pelvic and/or femoral osteotomy, avascular necrosis after DDH, dislocation, and subdislocation. The average age at the surgery was 53 (27 to 60). The average of follow-up period was 6.3 (4.6 to 9.1) years. The implants have a macro-porous structure on the surface. To set the metal shell in the intended position, the sclerotic lesion was adequately resected by the chisels and then we used the acetabulum reamers. Otherwise the sclerotic lesion would prevent the reamer to go into the suitable direction. We reamed the acetabulum until the lamina interna to use the maximum size of the metal shell (i.e. to use the liner as thick as possible) and at the same time for the medialization of the hip center. To avoid impingement, the osteophyte was resected without hesitating. We added the adductor tenotomy for 19 hips, the extensive release of the flexor tendons (including the quadriceps origin, the sartroius origin, and the gluteus maximus insertion) for three hips, and the release of the extensor insertion (the gluteus maximus) for two hips, and the release of the flexor insertion (the iliopsoas) for two hips. The hip score was improved in all patients. The average amount of the hip score was 59 before the surgery and was 90 at the final follow-up. A positive Trendelenburg sign was observed in 53 hips (62%) before the surgery and 12 hips (14%) at the final follow-up. We had no revision, no bearing failure (alumina fracture or excessive wear), no dislocation, and no squeaking in these patients. The average inclination angle of the cup was 41 (29 to 49) degrees. The average anteversion angle of the cup was 19 (13 to 27) degrees. No patient required the revision surgery. At the final follow-up, all implants were stable. In the acetabulum, the radio-lucent line was observed in two hips (2%) (zone I). In the femur the line was observed in 13 hips (15%). All lines existed in the proximal femur. There was no cystic osteolytic lesion. The prevalence of these periprosthetic reactions was less than those in the same type implant with the polyethylene on alumina bearing. Some authors alerted that the alumina on alumina articulation should only be applied in when the optimized implant orientation is obtained so as to prevent the impingement and dislocation. Fortunately the alignment in this study was within the safe zone. However, we must always be very careful of the joint alignment, range of motion, and the muscle tension during the surgery to avoid the bearing failure, as setting an adequate alignment and obtaining a firm uncemented fixation of the cup is relatively difficult in dysplastic hips. From this view point, Spongiosa Metal II cup suits the use of the alumina on alumina bearing especially for dysplastic hips

A modular layered acetabular component (metal-polyethylene-ceramic) was developed in Japan for use in alumina ceramic-on-ceramic total hip replacement. Between May 1999 and July 2000, we performed 35 alumina ceramic-on-ceramic total hip replacements in 30 consecutive patients, using this layered component and evaluated the clinical and radiological results over a mean follow-up of 5.8 years (5 to 6.5). A total of six hips underwent revision, one for infection, two for dislocation with loosening of the acetabular component, two for alumina liner fractures and one for component dissociation with pelvic osteolysis. There were no fractures of the ceramic heads, and no loosening of the femoral or acetabular component in the unrevised hips was seen at final follow-up. Osteolysis was not observed in any of the unrevised hips. The survivorship analysis at six years after surgery was 83%. The layered acetabular component in our experience, has poor durability because of unexpected mechanical failures including alumina liner fracture and component dissociation

Aims. Our aim in this study was to describe a continuing review of 11 total hip arthroplasties using 22.225 mm Alumina ceramic femoral heads on a Charnley flanged femoral component, articulating against a silane crosslinked polyethylene. Patients and Methods. Nine patients (11 THAs) were reviewed at a mean of 27.5 years (26 to 28) post-operatively. Outcome was assessed using the d’Aubigne and Postel, and Charnley scores and penetration was recorded on radiographs. In addition, the oxidation of a 29-year-old shelf-aged acetabular component was analysed. Results. The mean clinical outcome scores remained excellent at final follow-up. The mean total penetration remained 0.41 mm (0.40 to 0.41). There was no radiographic evidence of acetabular or femoral loosening or osteolysis. There was negligible oxidation in the shelf-aged sample despite gamma irradiation and storage in air. Conclusion. These results highlight the long-term stability and durability of this type of crosslinked, antioxidant containing polyethylene when used in combination with a small diameter alumina ceramic femoral head. Cite this article: Bone Joint J 2017;99-B:1286–9

Biomaterials improve the quality of life for an ever increasing number of people each year. The range of applications is vast and includes such things as joint and limb replacements, artificial arteries and skin, contact lenses and dentures. Ceramic biomaterials can be divided roughly into three main types governed by their in vivo behaviour and tissue response. In broad terms, there are the bioresorbable ceramics (b-tricalciumphosphate), bioreactive (hydroxyapatite, fluorapatite and bioglass) and bioinert (alumina, zirconia and pyrolytic carbon). The resorbable ones are incorporated into the surrounding tissue, or may even dissolve completely over a period of time. The bioreactive ones, like hydroxyapatite (used for coatings on metallic pins), encourage bonding to surrounding tissue with, for example, new bone growth being stimulated. The bionert ceramics are mostly used for structural components. Alumina and Zirconia are known for their general chemical inertness and hardness. These properties are exploited for implant purposes, where they are used as an articulating surface in hip and knee joints. Their ability to be polished to a high surface finish make them an ideal candidate for this wear application, where they operate against materials such as ultra high molecular weight polyethylene (UHMWPE). Alumina is a highly inert material and resistant to most corrosive environments, including the highly dynamic environment that is the human body. Under physiological conditions, it is classed as nearly inert, with evidence of any response from surrounding tissues and remaining essentially unchanged after many tyears of service. However, the body does recognise it as a foreign material and does attempt to isolate it by forming a layer of non adherent fibrous tissue around the implant where possible. Porous alumina may also be used to replace large sections of bone that have been removed for reasons such as cancer. Alumina has been used in dental applications. Specifically, it has been used for tooth replacements. The term high alumina ceramics is referred to materials that have the minimal content of 97% of alumina. If the percentage of minimal alumina is of 99% it is called high purity alumina ceramics. In its α phase (better famous like corundum), characterized from its particular structure and stability, the high purity alumina is used in orthopaedics, in the articulations of the hip and knee prostheses. From more than 30 years, the alumina has been successfully used. Today, more than 3,5 million of ball-heads e and 350 thousand of inserts of alumina BIOLOXA8 have been implanted confirming, in clinical use, the characteristics of low wear and biocompatibility that has allowed to reduce the problems of osteolisis induced by the polyethylene. The increase of the mechanical characteristics, the new shapes and the conical fixation have raised the reliability of the ball-heads and inserts of alumina. The BIOLOXA8forte (in commerce from 1994) is an high purity alumina (ca 99,7 %) with a small percentage of magnesium oxide (MgO). Approximately 50 years ago, magnesium oxide was introduced in the phase of sintering of the alumina, because it was discovered that a small amount of this additive prevented the increase of grains of alumina during the sintering process. It was therefore possible to have a more homogenous and dense microstructure, both characteristic directly correlated with the mechanical resistance. The suffix ‘forte’ derives from the increased mechanical characteristic caught up with the continuous optimization of the fabrication technology. Many laboratory tests and clinical cases have shown that the wear rate of alumina-alumina bearing coupling is extremely low (0.001 mm/year). If compared with metal-polyethylene (0,2 mm/year), it evidences the drastic reduction of particles of debris and therefore of the osteolysis problem. One of the main factors that the reduction of the wear rate involves is the characteristic molecular structure of alumina. Its superficial layer is composed of oxygen atoms that create a residual electric power which interacts with polarized molecules of the lubricant, binding it to the surface by strong Van der Waals ties. It is therefore guaranteed the presence of a fluid film that reduces the coefficient of clutch between the two surfaces involved during the articulation. The colour of alumina components is subjected to variations. Originally it is ivory, but it can easy stretch to the brown after sterilization with gamma beams that interact with the free valences introduced by the MgO. This change of colour does not induce changes of the mechanical characteristics. Currently the systems are completely modular and allow a wide choice of couplings. Ceramic acetabulum has been abandoned and replaced by ceramic inserts. In 1984 and subsequently in 1995, the introduction of ISO standards for the production of ceramics ball-heads and inserts and the concept of conical fixation has allowed to catch up higher reliability. The third generation of alumina has reduced the complications rates to values around 0.01% (for the 28 mm ball-heads and inserts), maintaining the excellent tribology and wear characteristics. Today, the alumina BIOLOXA8forte components are prepared in clean-room, sintered with high quality control processes, marked by laser and accurately inspected and tested. The dimension of grains of the microstructure, currently reduced to inferior values of 2 B5m, has allowed to raise the value of the mechanical resistance of about 45% (580 Mpa) of the value requested by ISO standard (400 Mpa). The tolerances between ceramics (ball-heads and inserts) and metallic parts (taper and metal shell) are fundamental for lengthening the implant reliability. It is important to control and certificate the stems and cups which the ceramic parts are applied on. Correct assembling and the respect of the compatibilities between parts (angle, material, producer) guarantee the longevity of the implants. Actually, in the orthopaedic field, the alumina application is mainly used in standard applications of the hip prostheses. Ball-heads of 22 milimeters of diameter, lengths of neck type XL, and the knee prostheses are not possible because of the mechanical characteristics of alumina not allowing to catch up the elevate stress values requested for these special applications. Between 1975 and 1977, the first studies issued that the strenght of alumina could be reinforced by the introduction of ceramic oxides. It was discovered that the strenght and toughness of alumina could endure a remarkable increment through the realization of composites with oxide of zirconium (zirconia). In the zirconia, during the phase of cooling from temperatures over 1170A1C, the grains endure a change of phase (from tetragonal to monoclinic), with an increase of 3% of volume. At ambient temperature the phase monoclina is stable. This transformation is martensitic, with energy absorption, and involves a heat-proof change of the simmetry of the structure. In the case of dispersed grains of zirconia in the alumina matrix, the transformation absorbs the energy of the crack and the tenacity of the ceramics increases. The Yttria (Y2O3) use, as stabilizing of the zirconia, has allowed to exceed the problem of the defects of the structure. It was introduced a percentage of zirconia stabilized with yttria (Y-TZP) in the alumina matrix and other mixed oxides to counterbalance the reduction of the hardness caused by particles of zirconia and to create lengthened particles during the sintering. All this studies have been used to create the new ceramics BIOLOXA8delta. Tests of biocompatibility in agreement with norms EN 30993 have been carried out allowing the implants of these new composite ceramics. The BIOLOXA8delta has a bending strenght around 1000 MPa, that is more than the double of the alumina standard (400 MPa). In the minimum fracture load test, ball-heads of 28 mm AF millimeter (neck L) have caught up values around 100 KN, very beyond the 46 KN requested by the FDA. Multiple cycles of sterilization in autoclaves have demonstrated that the BIOLOXA8delta does not endure alterations of the mechanical and tribological characteristics. On the basis of these results, BIOLOXA8delta will allow the realization of medical ceramics devices, already in study phase, like knee prosthesis, 22 mm ball-heads, thinner wallthickness of inserts, whose realization was not possible with the ceramic materials up to now available

Alumina and zirconia are known for their general chemical inertness and hardness. These properties are exploited for implant purposes, where they are used as an articulating surface in hip and knee joints. Their ability to be polished to a high surface finish make them an ideal candidate for such wear applications, where they compete against materials such as ultra-high-molecular-weight polyethylene. Alumina is a highly inert material and resistant to most corrosive environments. The term high alumina ceramics refersr to materials that have a minimal content of 97% of alumina. If there is a 99% minimal percentage of alumina it is called high purity alumina ceramics. In its _ phase (more famous than corundum), characterised by its particular structure and stability, high purity alumina has been being used in orthopaedics since 1970, in the articulations of the hip prostheses. BIOLOX. ®. forte (commercially available since 1994) is high purity alumina (ca 99.7 %) with a small percentage of magnesium oxide (MgO). Approximately 50 years ago, MgO was introduced during the sintering phase of alumina because it was discovered that a small amount of this additive prevented the increase in grains of alumina during the sintering process. It was therefore possible to have a more homogenous and dense microstructure; both characteristics directly correlated with the mechanical resistance. The suffix forte derives from the increased mechanical characteristic and continuous optimisation of the fabrication technology. One of the main factors involved in wear reduction is the characteristic molecular structure of alumina. Its superficial layer is composed of oxygen atoms that create a residual electric power which interacts with polarized molecules of the lubricant, tying it to the surface by strong Van der Waals ties. Therefore the presence of a fluid film that reduces the coefficient of clutch between the two surfaces involved during the articulation is guaranteed. The colour of alumina components varies. Originally it is ivory, but it can easily become brown after sterilization with gamma beams that interact with the free valences introduced by the MgO. This change in colour does not change the mechanical characteristics. Currently the systems are completely modular and allow a wide choice of couplings. In 1984 and subsequently in 1995, the introduction of ISO norms for the production of ceramics ball-heads and inserts and the concept of conical fixation has provided higher reliability. Today, the alumina BIOLOX. ®. forte components are prepared in clean-rooms, sintered with high quality control processes, laser marked and accurately inspected and tested. The tolerances between ceramics (ball-heads and inserts) and metallic parts (taper and metal shell) are fundamental for increasing implant reliability. It is important to control and validate the stems and cups which the ceramic parts are applied on. Correct assembly and the respect of the compatibilities between parts (angle, material, producer) guarantee the longevity of the implants. Actually, in the orthopaedic field, alumina is mainly used in standard applications of hip prostheses. Ball-heads of 22 mm in diameter, lengths of neck type XL, and the knee prostheses are not possible because the mechanical characteristics of alumina do not allow for the elevated stress values requested for these special applications. Between 1975 and 1977, it was discovered that the strength and toughness of alumina could endure a remarkable increment by developing composites with oxide of zirconium (zirconia). In zirconia, during the phase of cooling from temperatures over 1170°C, the grains go through a change of phase (from tetragonal to monoclica), with an increase of 3% of volume. At ambient temperatures the monoclica phase is stable. This transformation is martensitic, with energy absorption, and involves a heat-proof change of the symmetry of the structure. In the case of dispersed grains of zirconia in the alumina matrix, the transformation absorbs the energy of the crack and the strength of the ceramics increases. With the use of yttria (Y. 2. O. 3. ) to stabilise the zirconia the problem of the structure defects can be resolved. A percentage of zirconia stabilized with yttria (Y-TZP) was introduced in the alumina matrix and other mixed oxides to counterbalance the reduction of the hardness caused by particles of zirconia and to create lengthened particles during the sintering. All these studies have been used to create the new ceramic BIOLOX. ®. delta. Tests of biocompatibility in agreement with norms EN 30993 have been carried out, so that implants can be made of these new composite ceramics. Since 1970, more than 3,500,000 ball-heads and 350,000 inserts of alumina BIOLOX. ®. have been implanted. Owing to the grain size, currently reduced to values under 2 μm, the value of the mechanical resistance has been raised to about 580 MPa. The increase in the mechanical characteristics, the new shapes and the conical fixation have reduced the risk of fracture of the BIOLOX. ®. forte ball-heads and inserts to around 0.01% (Ø28 mm), maintaining the excellent tribology and wear characteristics. Many laboratory tests and clinical cases have shown that the wear rate of the alumina-alumina bearing complex is extremely low (0.001 mm/year). If compared with metal-polyethylene (0.2 mm/year) it shows a drastic reduction of particles of debris and therefore of the osteolysis problem. BIOLOX. ®. delta has a bending strength of around 1000 MPa, which is more than double that of the alumina ISO (400 MPa). In the minimum fracture load test, ball-heads of 28 mm Ø millimeter (neck L) have achieved values of around 100 KN, well beyond the 46 KN requested by the FDA. Multiple cycles of sterilisation in autoclaves have demonstrated that the the mechanical and tribological characteristics of BIOLOX. ®. delta are not altered. On the basis of these results, BIOLOX. ®. forte can be considered a reliable alternative to other materials in standard applications and the new alumina composite BIOLOX. ®. delta will allow the realization of medical ceramics devices, already in the study phase, such as knee prosthesis, 22-mm ball-heads and thinner wall-thickness of inserts, which could not be developed up to now with the available ceramic materials

The choice to use alumina in the manufacture of a low-wear THR bearing made by Boutin and its co-workers has proven its effectiveness in almost 35 years of clinical use. A continuous development process aimed to improve mechanical properties led to today’s materials that exhibit extreme high reliability. The recent introduction in clinical use of alumina matrix composites represents the latest evolution of alumina that thanks to high hardness, toughness, and bending strength allow to manufacture new design of ceramic components. Composites obtained introducing zirconia in the alumina matrix, known as Zirconia Toughened Alumina (ZTA) are candidate for use in THA bearings from a long time. A real breakthrough was represented by alumina ceramics toughened both by zirconia both by platelets nucleated in-situ during sintering (Zirconia-Platelet Toughened Alumina - ZPTA). The chemical composition and the microstructure of ZPTA were optimised to achieve a ceramic material joining strength of more than 1200MPa, Vickers hardness 1975, fracture toughness of 6,5 MPa m-1/2, andextremely low wear also in the most severe simulator tests performed in microseparation mode The paper reviews the improvements introduced in the technology of ceramic for arthoplasty, and their effects on the microstructural properties and on the performances of the past and actual generation of ceramic for THR bearings, and summarise the results obtained in the development of alumina matrix composites

It has been suggested that the wear of ultra-high molecular weight polyethylene (UHMWPE) in total hip replacement is substantially reduced when the femoral head is ceramic rather than metal. However, studies of alumina and zirconia ceramic femoral heads on the penetration of an UHMWPE liner in vivo have given conflicting results. The purpose of this study was to examine the surface characteristics of 30 alumina and 24 zirconia ceramic femoral heads and to identify any phase transformation in the zirconia heads. We also studied the penetration rate of alumina and zirconia heads into contemporary UHMWPE liners. The alumina heads had been implanted for a mean of 11.3 years (8.1 to 16.2) and zirconia heads for a mean of 9.8 years (7.5 to 15). The mean surface roughness values of the explanted alumina heads (Ra 40.12 nm and Rpm 578.34 nm) were similar to those for the explanted zirconia heads (Ra 36.21 nm and Rpm 607.34 nm). The mean value of the monoclinic phase of two control zirconia heads was 1% (0.8% to 1.5%) and 1.2% (0.9% to 1.3%), respectively. The mean value of the monoclinic phase of 24 explanted zirconia heads was 7.3% (1% to 26%). In the alumina group, the mean linear penetration rate of the UMWPE liner was 0.10 mm/yr (0.09 to 0.12) in hips with low Ra and Rpm values (13.22 nm and 85.91 nm, respectively). The mean linear penetration rate of the UHMWPE liner was 0.13 mm/yr (0.07 to 0.23) in hips with high Ra and Rpm values (198.72 nm and 1329 nm, respectively). This difference was significant (p = 0.041). In the zirconia head group, the mean linear penetration rate of the UHMWPE liner was 0.09 mm/yr (0.07 to 0.14) in hips with low Ra and Rpm values (12.78 nm and 92.99 nm, respectively). The mean linear penetration rate of the UHMWPE liner was 0.12 mm/yr (0.08 to 0.22) in hips with high Ra and Rpm values (199.21 nm and 1381 nm, respectively). This difference was significant (p = 0.039). The explanted zirconia heads which had a minimal phase transformation had similar surface roughness and a similar penetration rate of UHMWPE liner as the explanted alumina head

Introduction. Third body wear caused by contaminated bearing environment with debris that may have been generated by a worn or fractured revised bearing coupling, but also originated by generation of metal/cement particles during the primary or revision surgery, may be a relevant issue for the implant life. Objectives. To evaluate the wear behavior of a last generation alumina matrix ceramic composite (AMC) bearing in a worst case scenario consisting of highly contaminated test lubricant with alumina particles in a hip joint simulator study. Methods. AMC (BIOLOX®delta - Group 1) and alumina (BIOLOX®forte - Group 2) liners with an internal diameter of 32mm were articulated against AMC BIOLOX®OPTION heads (all CeramTec GmbH, Plochingen). Coarse alumina particles (D(50):60µm) and fine alumina particles (D(50):0.30µm) with a concentration of 48mg/ml were used as environmental contamination of the first 2mlc and the second 2mlc, respectively. All components were tested according to ISO14242-1(2012) using the EndoLab®hip joint simulator. Each group consisted of 3 couples plus one axially loaded control consisting of a 32mm AMC head on an alumina liner. The test fluid was exchanged every 500'000 cycles. Two different test regimes describing level walking and subluxation of the insert from the femoral head were used as test input. The first regime included 500 standard walking cycles followed by a second block of 5 subluxation cycles. Head subluxation is assumed to increase the number of third-body particles that enter the otherwise closely conforming articular bearing space, when compared to level-walking cycles alone. To maintain the particle suspension in the test fluid, the test fluid of each test chamber was circulated by peristaltic pumps. The wear rate was determined by gravimetric method. The surface of ball heads was subjected to visual inspection every 500'000 cycles by optical and laser microscope. The depth of scratches was measured by the laser microscope. Results. After 2 million load cycles with the test fluid contaminated with coarse alumina particles, no significant wear was detected by the gravimetric method. The qualitative surface inspection by laser microscope individuated an increasing, but low concentration of sparse tiny scratches about 40nm deep on ball head surface at every simulator stop. Nevertheless, after loading the chambers with fine alumina particles, bearing surface wear seemed to increase consistently, since opaque areas appeared after 3 million load cycles, but the wear-rate remained close to the gravimetric measurement detection limit (about 0.1–0.2mg) indicating the still extremely low wear-rate of the tested ceramic couplings. Conclusions. This study confirms the high wear and scratch resistance of AMC used in THA. Even in heavily contaminated environment with hard alumina particles, which may occur after fracture of a ceramic component, gravimetry wasn't able to detect significant wear. The visual inspection by laser microscope exhibited only slight damaged surface characterized by tiny scratches and more opaque areas in the main wear zone as result of using fine alumina particles. Ceramic-on-ceramic is a safe bearing even in the case of revision for ceramic fracture, maintaining the excellent wear resistance of this bearing

Aims. To determine the effect of a change in design of a cementless ceramic acetabular component in fixation and clinical outcome after total hip arthroplasty. Patients and Methods. We compared 342 hips (302 patients) operated between 1999 and 2005 with a relatively smooth hydroxyapatite coated acetabular component (group 1), and 337 hips (310 patients) operated between 2006 and 2011 using a similar acetabular component with a macrotexture on the entire outer surface of the component (group 2). The mean age of the patients was 53.5 (14 to 70) in group 1 and 53.0 (15 to 70) in group 2. The mean follow-up was 12.7 years (10 to 17) for group 1 and 7.2 years (4 to 10) for group 2. Results. No hips were revised due to complications related to bearing fracture or to stem loosening. A total of 15 acetabular components were revised for aseptic loosening in group 1 and two in group 2. The survival rate for acetabular component aseptic loosening at eight years was 96.8% (95% confidence interval (CI) 94.8 to 98.7) for group 1 and 99.2% (95% CI 98.0 to 100) for group 2. The risk for aseptic loosening of the acetabular component was higher in group 1 (p = 0.04, Hazard Ratio (HR) 4.99), dysplastic acetabula (p = 0.01, HR 4.12), components outside Lewinnek´s zone (p < 0.001, HR 6.13) and in those with a hip rotation centre distance greater than 5 mm (p = 0.005, HR 4.09). . Conclusion. Alumina ceramic-on-ceramic THA is an excellent option for young patients. Although newer components appeared to improve fixation, acetabular reconstruction is essential to obtain a satisfactory outcome. Cite this article: Bone Joint J 2017;99-B:749–58

The choice to use alumina in the manufacture of a low-wear THR bearing made by Boutin and its co-workers has proven its effectiveness in almost 35 years of clinical use. A continuous development process aimed to improve mechanical properties led to today’s materials that exhibit extreme high reliability. The recent introduction in clinical use of an alumina matrix composite developed by CeramTec and available under the trade name Biolox®Delta represents the latest evolution of alumina. This material allow new design in ceramic components thanks to its equilibrium among high hardness, high toughness, and high bending strength. Composites obtained introducing zirconia in the alumina matrix, known as Zirconia Toughened Alumina (ZTA) are candidate for use in THA bearings from a long time. A real breakthrough was represented by alumina ceramics toughened both by phase transformation both by platelets nucleated in-situ during sintering. Optimised processing and quality control led to optimised material behaviour. The chemical composition and the microstructure of Biolox®Delta were optimised to achieve a ceramic material joining strength of more than 1200 MPa, Vickers hardness 1975, fracture toughness of 6,5 MPam-1/2, and extremely low wear also in the most severe simulator tests performed in microseparation mode. The paper reviews the improvements introduced in the technology of ceramic for arthoplasty, and their effects on the microstructural properties and on the performances of the past and actual generation of ceramic for THR bearings, and summarise the results obtained in the development of alumina matrix composite Biolox® Delta