CERAMIC-CERAMIC AND METAL-POLYETHYLENE TOTAL HIP REPLACEMENTS

Сomparative analysis of large diameter bearing ceramic monoblock acetabular components

Introduction

The goal of total hip arthroplasty (THA) is to provide ease to patients with persistent and exhausting pain. Durability is the main challenge associated with any tribological pair, with the aim of minimizing wear and thus avoiding problems with aseptic loosening of components and osteolysis. When polyethylene inserts are used in young patients, we should always consider their disadvantages, e.g., increased wear of the interacting components. Proper selection of friction pairs allows prolonged implant life. Ceramic-on-ceramic (CoC) friction pairs should provide long-term wear of the friction components.

Objectives

To evaluate the mid-term results of using the monoblock Maxera Cup (Zimmer Biomet) acetabular system in cementless THA.

Methods

We operated on 151 patients using the monoblock Maxera Cup (Zimmer Biomet) acetabular system. The mean follow-up duration was 6 years (73.8 ± 11.7 months). Fifty-seven women and 94 men aged 19-64 years were surgically treated. All 170 THA cases in 151 patients were divided into 3 groups according to the diameters of the CoC friction pairs used (40, 44, and 48 mm). As a control group, we have taken 50 patients who received 50 THA using a standard 36 mm CoC friction pair. The achieved functional results were evaluated using the HHS scale, WOMAC scale, and SF36 scale. We also evaluated the mean duration of surgical intervention and blood loss.

Results

When assessing long-term results, the average HHS significantly increased from 34.10 (before surgery) to 87.50 (postoperation) points in the 1st group, from 46.24 to 96.5 points in the 2nd group, and from 38.70 to 92.10 points in the 3rd group. From preoperative examination to 1 year after surgery, there was a 2.4-fold improvement in the functional results in group 1 and 1,8 and 2.9 -fold improvement in groups 2 and 3, indicating excellent treatment results. Inconsistent creaking in the implanted joint was noted in only 2.6% of cases in which a CoC friction pair with a diameter of 44 mm was used. We did not observe any complications associated with aseptic or septic loosening of the components either clinically or radiologically during the 7-year follow-up period after surgery in the entire patient population.

Conclusions

1Use of the CoC monoblock allowed us to expect an increase in the life cycle of the implant and provided good joint function and perception by the patient.2Monoblock cups provided good joint function and perception by the patient.3Acoustic effects, in the form of minor creaking, did not affect the functional results.

Does load-bearing materials influence hip capsule thickness in total hip replacement? An MRI case-matched study

BACKGROUND

Ceramic-on-ceramic (COC) total hip replacements (THR) have exhibited less instability and late dislocation. Hip capsule plays an important role in hip stability. Different surrounding soft tissue reactions have been observed according to the bearing material used but no study compared these data using MRI investigation. Therefore, we performed a retrospective case control study to compare hip capsule thicknesses according to the bearing materials in THR and in native hips.

HYPOTHESIS

Hip capsule is thicker after COC THR compared to ceramic- or metal-on-polyethylene (PE) bearings, or native hips.

MATERIALS AND METHOD

Magnetic resonance imaging (MRI) images, combined with a multi acquisition variable resonance image combination (MAVRIC) sequence, was used to measure the hip capsule thickness in 16 patients (29 hips) who had either COC (13 hips, median age at surgery: 64.8 years old, median follow-up at imaging: 2482 days), PE bearings (11 hips, median age at surgery: 48.4 years old (significantly different from COC THR), median follow-up at imaging: 1860 days (NS)), or a native hip with no implant (5 hips). Two independent radiologists measured capsular thicknesses in 4 different zones and were blinded regarding the bearing components. The imaged hips were classified into three groups: native, COC and PE.

RESULTS

The COC THR group had the thickest capsules (median 7.0mm, range 2.9-15.5mm). This result was statistically significant (p<0.0001) when compared to PE THR (median 4.9mm, range 2.2-10.5mm), and to native hips (median 4.1mm, range 2.7-6.9mm) measurements, respectively. Furthermore, painful hips had thinner capsules (4.6mm, range 2-10.5) compared to not painful hips (6.8mm, range 2.3-15.5) (p=0.0006).

DISCUSSION

This is the first in-vivo study measuring capsular thickness in THR with the objective of measuring variations according to the hip implant materials used. The results revealed a significantly thicker capsule for the COC bearing compared to either PE or native hips, and a thinner capsule in painful hips.

LEVEL OF EVIDENCE

III, retrospective non-consecutive cohort study.

Alumina particles influence the interactions of cocultured osteoblasts and macrophages

The purpose of the current study was to evaluate the effects of alumina particles on secretion of several cytokines involved in bone resorption in cocultures of macrophages and osteoblasts. To distinguish the contribution of each individual cell type, we have established a heterologous in vitro system that makes use of mouse J774 cells and primary cultured human osteoblasts. J744 cells decreased the production of TNF-alpha when they were cocultured with osteoblasts. Treatment of J744 cells with alumina particles increased TNF-alpha secretion, but the induction was lower when cells were cocultured with osteoblasts. Secretion of IL-6 by J744 cells was very low, and increased in the presence of osteoblasts. Alumina particles were only able to stimulate the release of IL-6 by J744 cells when cells were cocultured with osteoblasts. On the other hand, incubation of osteoblasts with alumina particles enhanced the release of IL-6 and GM-CSF. Coculturing osteoblasts with J744 cells induced them to release IL-6 and GM-CSF, and treatment with alumina further increased the secretion of both mediators by osteoblasts. According to these in vitro results, it seems rather plausible that alumina particles are able to initiate an inflammatory response in vivo.

Ceramic-on-ceramic versus ceramic-on-polyethylene bearings in total hip arthroplasty: Results of a multicenter prospective randomized study and update of modern ceramic total hip trials in the United States

One reason why otherwise well-functioning total hip replacements have a finite service life is eventual aseptic loosening of the implants because of osteolysis induced by wear particles from the artificial bearing. Pain and osteolysis from wear debris can manifest even in the absence of aseptic loosening. Total hip replacements with ceramic-on-ceramic articulations have shown less wear both in vitro and in vivo. A randomized prospective clinical trial was conducted to compare the outcomes of ceramic-on-ceramic articulations to ceramic-on-polyethylene articulations. Two-year data are of interest because premature failures of ceramic femoral heads usually occur by this time interval. Of 500 patients enrolled in this trial, half received total hip replacements with alumina-on-alumina bearings, while the other half had ceramic-on-polyethylene bearings. At the two-year follow-up, 444 patients (217 study group and 227 control group) were available for review. The clinical and radiographic outcomes between the groups were comparable, and reflected the typical results of primary total hip replacements. No complications related to spontaneous failures of the ceramic bearings were observed at this early follow-up period. Further follow-up is needed to confirm these findings over the long-term, but the short-term safety of alumina ceramic bearings in hip replacements reported in other recent reports is further validated by our findings. (Hip International 2005; 15: 129-35).

Ceramics in total hip replacement

Alumina-on-alumina total hip arthroplasty has been used for 32 years in Europe. The theoretical advantages of this combination are represented by its remarkable sliding characteristics, its very low wear debris generation, and its improved fracture toughness. These advantages are achieved if the material is processed properly with high density, high purity and small grains. We summarize the results obtained with the alumina-on-alumina combination concerning in vitro and in vivo wear behavior with special emphasis on wear debris characterization and quantification and histologic tissue examinations. Alumina-on-alumina seems to be one of the best choices in young and active patients provided that sound socket fixation is maintained in the long term.

Concerns about ceramics in THA

Currently available ceramic materials are superior to those used originally in total hip arthroplasty, which should translate into a much lower complication rate than what has been reported previously. In spite of this, a number of concerns remain. The ceramic-on-ceramic articulation is not immune to wear and surface damage. Conditions associated with ceramic wear include vertical cup position, femoral neck impingement, and femoral head separation. A unique pattern of stripe wear has been described as something that results from microseparation during gait. Catastrophic failure, although rare, continues to be a concern, and not all fractures can be predicted by proof testing. Revisions needed because of ceramic fractures can be extensive, and the results of the revision procedures can be compromised by the presence of highly abrasive particulate debris that is retained. Other concerns include the generation of debris from modular interfaces, neck damage and debris generation from impingement of some designs, inability to use a ceramic head a second time on a metal trunnion, and the dramatic loss of head and liner options intraoperatively. Although ceramics show great promise as a lower wear articulation, manufacturing and design modifications and improvements will continue in an attempt to address the substantial concerns that persist.

Biologic and tribologic considerations of alternative bearing surfaces

Patients who are young or active or both who require total joint replacement pose a unique challenge; their high activity demands wear-resistant bearings that will perform for decades, without suffering from the adverse effects of accumulated wear products. We discuss the tribologic and biologic properties of newly introduced bearing materials for hip prostheses. The new PEs are intended to address the aseptic loosening problem by reducing the volume of submicron PE particles to a level well below that historically associated with osteolysis. However, choosing among the several variations of the cross-linked thermally-stabilized PEs is confounded by conflicting opinions regarding the optimum balance between long-term wear resistance and mechanical strength, and regarding potential effects of differences in morphologic features of the submicron-sized wear particles on their relative osteolytic potential. Metal-on-metal bearings have clinically proven wear resistance and the advantage of self-polishing, but the long-term biologic effects of metallic ions remain unknown. Ceramic-on-ceramic bearings have the advantage of high biocompatibility and usually very low wear, but fracture remains a rare but catastrophic complication. The choice of an appropriate bearing couple should be made after a thorough consideration of the relative risks and potential benefits of each of these materials.

Long-term results of alumina-on-alumina hip arthroplasty for osteonecrosis

Alumina-on-alumina bearings in THR may, in theory, provide an effective answer to osteolysis in young patients with ON of the femoral head. The purpose of this retrospective study was to report the long-term results of a series of 52 consecutive alumina THAs (41 patients) done for ON. The mean age of the patients at surgery was 41 years (range, 22-79 years). Cemented femoral stems with a 32-mm alumina head were used. Plain alumina cups were used and were either cemented (39 hips) or press-fit (13 hips). No patients were lost to followup. Sixteen hips have been revised. Aseptic loosening of the socket was the main cause of failure. At an average 16-year followup (range, 11-23.65 years), 26 hips were rated excellent and one hip was rated good. No osteolysis was observed and wear was undetectable. If revision for aseptic loosening was the end point, the rate of survival was 88.5% at 10 years for the socket and 100% at 10 years for the stem. With the alumina-on-alumina hip replacement done for ON, absence of osteolysis can be expected for as many as 24 years after the operation. New methods of socket fixation now are being explored.

Surface characterization and debris analysis of ceramic pairings after ten million cycles on a hip joint simulator

This study was aimed at characterizing the ceramic wear particles produced during tests on a hip joint wear simulator of up to 10 million cycles. Alumina and alumina-zirconia composites were studied as commercial or potential hip joint products respectively. No ceramic particles could be observed, even after a careful isolation procedure. This confirms the low wear rate found for these materials in previous works (of the order of tenths of milligrams per million cycles). Surface characterization was conducted by means of scanning electron microscopy. It confirms the low wear regime of ceramic pairings and allows ceramic wear debris morphology to be defined. The effect of microstructure on surface wear is discussed.

Alumina ceramic bearings for total hip arthroplasty

This article presents an experience with alumina ceramic bearings involving the use of improved ceramic materials as well as new design considerations. The alumina-alumina ceramic hard bearing is a safe option for the younger, more active patient.

Debris from failed ceramic-on-ceramic and ceramic-on-polyethylene hip prostheses

To compare the properties of wear debris between ceramic-on-ceramic and ceramic-on-polyethylene total hip prostheses, particles were isolated and characterized from tissue biopsies obtained at revision arthroplasty or autopsy from two similar uncemented modular hip systems. Group A hips (11 patients; mean, 31 months in vivo) had titanium shells with alumina inserts, alumina femoral heads, and titanium alloy stems. Group B hips (seven patients; mean, 42 months) were the same as Group A but with polyethylene acetabular inserts. Particles were characterized using an electrical resistance particle analyzer, scanning electron microscope, and energy dispersive xray spectroscope. Most of the particles in Group A were ceramic, whereas most of the particles in Group B were polyethylene. Metal particles from the femoral stem and the acetabular shell also were present. If one Group A hip with impingement is excluded, the rate of particle production is significantly lower in the ceramic-on-ceramic group than in the ceramic-on-polyethylene group. With the number of samples available, no significant difference in average size could be detected among the different types of particles or among the groups.

Bioactivity of sol-gel bioactive glass coated alumina implants

Alumina on alumina total hip arthroplasty has been in use for more than 25 years with encouraging results. However, an improvement of the alumina/bone interface still is required. The objective of this study was to investigate the in vitro and in vivo osteoconductive properties of sol-gel bioactive glass coated alumina implants. Two sol-gel glass compositions (58S Bioglass(R) and 77S Bioglass(R)) were used as coatings on alumina substrates and implanted in a rabbit model. The 58S sol-gel coating was employed in two configurations, single (A58S1) and double layer (A58S2). SEM analysis after one week in simulated body fluid revealed small crystals assumed to represent the initial phase of hydroxyapatite formation, whereas no clear conclusion could be drawn from Fourier transform infrared spectroscopy data. The percentage of bone in direct contact was greater for coated implants when compared to bulk alumina implants (p <0.001). In the case of A58S1 implants, bone percentage significantly increased from 45.1% after 3 weeks up to 87. 8% after 24 weeks of implantation (p = 0.0004). The presence of osteoid tissue, related to an aluminum release from the alumina substrates, was greatly diminished when compared to melt-derived glass-coated alumina implants.

Evolution of alumina-on-alumina implants: a review

The use of alumina-on-alumina sliding surfaces for total hip replacement is becoming increasingly popular. The author has reviewed the 30-year history of this material. Technical aspects such as the quality of the material, quality of the design, and the risk of fracture are presented. The clinical results observed by the author are summarized with additional references to the results of other surgeons. The overall conclusion is that this material is very safe if all the quality requirements are met. The extremely low generation of wear debris and the excellent biologic tolerance of the material impart a long lifetime to the implant in young and active patients.

Press-fit metal-backed alumina sockets: a minimum 5-year followup study

Two hundred thirty-four consecutive alumina-on-alumina hip replacements using a press-fit metal-backed socket, performed on 214 patients (98 women, 116 men) have been reviewed. These included 201 primary procedures and 33 revision procedures. The median age of the patients at the time of surgery was 62 years (range, 21-83 years). Fourteen patients (16 hips) died from unrelated causes. Eleven patients (11 hips) underwent a total hip arthroplasty revision for recurrent dislocation (one hip), deep infection (two hips), fracture of alumina femoral head (one hip), persistent hip pain (one hip) and aseptic loosening (six hips). The survival rate after 9 years was 93.4% when revision of the prosthesis was considered the end point, and 97.4% if revision of the prosthesis for aseptic loosening was considered the end point. Results were assessed in the surviving patients with a minimal 5-year followup (170 patients, 184 hips). At the median followup of 7.8 years, the average Merle d'Aubigné and Postel score had improved from 11.9- to 17.7. Results were graded as excellent in 148 hips (80.5%), very good in 31 hips (17%), good in two hips (1%), and fair in three hips (1.5%). Radiologic data were documented for 134 patients (143 hips). Three sockets (2%) had a complete and nonprogressive radiolucent line less than 1-mm thick, one stem (0.7%) had lucencies involving five zones, and two stems (1.4%) had isolated femoral osteolysis. Neither component migration nor acetabular osteolysis were detected. A press-fit metal-backed socket may offer a good solution for alumina socket fixation when combined with a careful surgical technique of implantation.

Biological reactions to wear debris in total joint replacement

The vast majority of total hip prostheses currently implanted consist of a hard metal or ceramic femoral head articulating against an ultra-high molecular weight polyethylene (UHMWPE) acetabular cup. Over the last 10 years, evidence has accumulated to show that these prostheses are prone to failure due to late aseptic loosening and few survive beyond 25 years. With an increasing need to implant hip prostheses in the younger, more active patient the need to understand the mechanisms of failure and to develop artificial hip joints using alternative materials have become major issues in the orthopaedic community. This review focuses initially on our current understanding of the biological reactions to UHMWPE prosthetic wear debris in vivo and in vitro since this is believed to be the main cause of late aseptic loosening. While the precise mechanisms of osteolysis induced by UHMWPE wear debris have not been elucidated, the major message to emerge is that it is not the wear volume that determines the biological response to the debris, but the concentration of the wear volume that is within the critical size range (0.2-0.8 micron) for macrophage activation. The review then considers whether the problem of wear-debris-induced osteolysis may be overcome with the use of new generation metal-on-metal or ceramic-on-ceramic prostheses. For metal-on-metal prostheses, the prospects for increasing the osteolysis free life of the implant are good but additional biological problems associated with the nanometre size and reactivity of the wear particles in vivo may emerge. For the ceramic-on-ceramic prostheses, although initial prospects are encouraging, more data are needed on the characteristics of the wear particles generated in vivo before predictions can be made. It is concluded that the pre-clinical testing of any new materials for joint replacement must include an analysis of the wear particle characteristics and their biological reactivity in addition to the usual assessment of wear.

Ceramic bearing surfaces

Despite more than 25 years of clinical experience with ceramic materials as bearing surfaces, their role in modern joint replacement surgery remains to be clearly defined. The two primary materials are alumina and zirconia. The application of these materials is primarily as a femoral head bearing surface against polyethylene, but alumina also is used as a femoral head and an acetabulum to provide a polyethylene-free bearing surface. Important issues that must be clarified for these materials to gain wide acceptance are the material properties, wear rates against polyethylene and alumina, the biologic response to ceramic wear debris, and cost in relation to indications. The bulk materials are biocompatible, hard, wettable, high-strength, and can yield good surface finishes. Linear polyethylene wear against alumina heads is reported to be as much as a factor of 5 to 10 lower than metal versus polyethylene. Thus, the ceramic femoral head may be a good choice for the younger patient in whom it seems necessary to use a larger head for stability reasons with a polyethylene cup. Ceramic-on-ceramic wear rates are in the range of 0.003 mm/year, a factor of 10 less than the lowest polyethylene wear rates. These costly materials are limited in head and neck sizes because of statistical variation in strength that can lead to fracture. Occasional reports of high alumina-on-alumina wear have appeared. Many of the problems of the past have been design, manufacture, or application related, and have been improved or eliminated. Proper clinical technique in the use of ceramic femoral heads is crucial to prevent fracture. The materials hold high promise and should continue to be used so that additional experience can help define the clinical indications for components made of these materials.

Flow cytometric analysis of macrophage response to ceramic and polyethylene particles: effects of size, concentration, and composition

Using the J774 macrophage cell line, we designed an in vitro model to analyze by flow cytometry the effects of size, concentration, and composition of ceramic (Al2O3 and ZrO2) and high density polyethylene (HDP) particles on phagocytosis and cell mortality. Inflammatory mediator (TNF-alpha) also was measured by ELISA. Kinetic studies revealed that phagocytosis of the particles begins very early after cell exposure, increasing with time and particle concentration and reaching a plateau after 15 h. This implies that the optimum period to evaluate cellular response to particulate debris is between 15 and 24 h of incubation. Results also showed that phagocytosis increases with concentration for particles up to 2 microns. For larger particles (up to 4.5 microns), phagocytosis seems to reach a plateau independent of size and concentration, which suggests a saturation of phagocytosis that is most likely dependent on overall particle volume ingested. We did not detect any significant difference in phagocytosis between Al2O3 and ZrO2 at 0.6 microns. Al2O3 seems to be more easily phagocytosed than HDP at the same size (4.5 microns) and concentrations. Cytotoxicity studies revealed that macrophage mortality increases with particle size and concentration for sizes greater than 2 microns. Smaller particles (0.6 microns) cause cell mortality only at higher concentrations (from 1,250 particles per cell), but the mortality is still very low (10%). No significant difference in cell mortality and TNF-alpha release was found between Al2O3 and ZrO2. Effects of Al2O3 and HDP at 4.5 microns were compared by measuring TNF-alpha release. Results showed that TNF-alpha release increases with particle concentrations and is higher with HDP than with Al2O3.