Fracture of an alumina ceramic head in total hip arthroplasty

Thirteen-year results of cementless total hip arthroplasty with zirconia heads on highly cross-linked polyethylene

OBJECTIVES

Zirconia ceramic was introduced for femoral heads because of its mechanical strength and fracture toughness. Highly cross-linked polyethylene has been shown to achieve wear reduction compared to conventional polyethylene. The purpose of this study was to investigate the long-term results of cementless total hip arthroplasty with zirconia femoral heads on highly cross-linked polyethylene.

METHODS

Radiographic measurements of two-dimensional femoral head penetration into the polyethylene were performed with a computerized method (PolyWare) in 93 hips at a mean follow-up of 13 years. The steady-state wear rates were measured based on the radiographs from the first year after surgery to the final follow-up.

RESULTS

The mean Merle d'Aubigné and Postel score had improved significantly from 10.9 points preoperatively to 15.3 postoperatively (p < 0.001). Osteolysis was not found around the implant, and no zirconia heads had fractures. The total head penetration rate was 0.04 mm/year, and the steady-state wear rate was 0.02 mm/year. Kaplan-Meier survivorship with the endpoint of revision was 97% (95% confidence interval [CI], 92% to 99%) at 10 years.

CONCLUSION

Zirconia on highly cross-linked polyethylene demonstrated extremely low wear properties at long-term follow-up.

The Influence of Contamination and Cleaning on the Strength of Modular Head Taper Fixation in Total Hip Arthroplasty

BACKGROUND

Intraoperative interface contamination of modular head-stem taper junctions of hip implants can lead to poor fixation strength, causing fretting and crevice corrosion or even stem taper fracture. Careful cleaning before assembly should help to reduce these problems. The purpose of this study was to determine the effect of cleaning (with and without drying) contaminated taper interfaces on the taper fixation strength.

METHODS

Metal or ceramic heads were impacted onto titanium alloy stem tapers with cleaned or contaminated (fat or saline solution) interfaces. The same procedure was performed after cleaning and drying the contaminated interfaces. Pull-off force was used to determine the influence of contamination and cleaning on the taper strength.

RESULTS

Pull-off forces after contamination with fat were significantly lower than those for uncontaminated interfaces for both head materials. Pull-off forces after application of saline solution were not significantly different from those for uncontaminated tapers. However, a large variation in taper strength was observed, pull-off forces for cleaned and dried tapers were similar to those for uncontaminated tapers for both head materials.

CONCLUSION

Intraoperative contamination of taper interfaces may be difficult to detect but has a major influence on taper fixation strength. Cleaning of the stem taper with saline solution and drying with gauze directly before assembly allows the taper strength of the pristine components to be achieved. Not drying the taper results in a large variation in pull-off forces, emphasizing that drying is essential for sufficient and reproducible fixation strength.

Long Term Survivorship of a Severely Notched Femoral Stem after Replacing the Fractured Ceramic head with a Cobalt-Chromium Head

Background:

Although ceramic head fracture occurs infrequently today, in the event of a fracture, the resulting revision surgery can prove very challenging, since the ceramic particles lodge into the surrounding soft tissue and can cause rapid implant failure

Case Presentation:

A case of long term survivorship of a severed notched femoral stem after replacing the fractured femoral head with a cobalt-chromium one is reported in a 40-year old woman with hip dysplasia who underwent an uncomplicated total hip arthroplasty. The incident of ceramic femoral head fracture occurred 14 months postoperatively without reporting any significant trauma. Intraoperative findings at revision were a multifragmented femoral head and a damaged polyethylene insert along with diffuse metallosis and excessive wear of the cone of the stem. Both the stem and the acetabular component were stable. After removal of ceramic fragments, metallotic tissue excision and careful lavage of the joint, the inlay was replaced by a similar one and a cobalt-chromium femoral head was placed to the existing notched taper of the firmly incorporated stem. At the 13^th year follow up examination, the patient had no pain, used no walking aids, and had normal activity with no signs of wearing or loosening in the plain x-rays.

Conclusion:

Despite current recommendations of using ceramic femoral heads in cases of fracture or to revise the severely damaged stems we were able to provide a long term survivorship up to 13 years postoperatively of a cobalt-chromium femoral head applied to a severe damaged stem.

A novel technique for identification of fractured ceramic acetabular liner in total hip arthroplasty: a case report

In total hip arthroplasty ceramic bearings are liable to fracture. We present the case of an 82-year-old male with groin pain and an audible squeak 6 months post ceramic on ceramic hip arthroplasty. Initial plain radiography and examination under anaesthetic (EUA) were normal. Fluoroscopy with normal image exposure was also unremarkable. Over penetration of the image intensifier film demonstrated a fracture of the ceramic acetabular liner. The patient subsequently underwent a revision of both acetabular and femoral bearing surfaces.Displaced ceramic liner fractures are easy to identify with plain radiographs. We recommend the use of over penetration using image intensification as a technique to help identify subtle ceramic liner fractures. To our knowledge this has not been previously reported in the literature.

The Absence of Hydroxyapatite Coating on Cementless Acetabular Components Does Not Affect Long-Term Survivorship in Total Hip Arthroplasty

BACKGROUND

Hydroxyapatite (HA) has been applied to joint prostheses as a bioactive coating to prolong their durability. However, HA benefits for cup survival in total hip arthroplasty (THA) remain controversial. In this study, we compared the survival of cups with and without HA coating during a minimum follow-up of 18 years.

METHODS

In total, 183 THA cases in 163 patients were analyzed, including 73 cups with HA coating (HA(+) group) and 110 without HA coating (HA(-) group); otherwise, the cups had identical titanium-sprayed rough surfaces and were fixed with screws. In both groups, the same conventional polyethylene liners were applied. Zirconia and alumina ceramic heads were used in the HA(+) and HA(-) groups, respectively. We retrospectively analyzed cup survival based on cup revision for any reason or aseptic loosening as end points.

RESULTS

In total, 7 and 8 revisions were performed in the HA(-) and HA(+) groups with survival rates of 86.3% and 90.1%, respectively. Among them, 3 cups in the HA(-) group and 1 cup in the HA(+) group were revised for aseptic loosening in 20 years (survival rates 94.1% and 98.7%, respectively). No significant difference was detected in cup survival rates between the groups based on both end points. There were no stem revisions during the observation period.

CONCLUSION

The results suggested that HA coating did not have either beneficial or adverse effects on the long-term cup survival in primary cementless THA.

Quantification of the Contact Area at the Head-Stem Taper Interface of Modular Hip Prostheses

Corrosion of modular taper junctions of hip implants may be associated with clinical failure. Taper design parameters, as well as the intraoperatively applied assembly forces, have been proposed to affect corrosion. Fretting corrosion is related to relative interface shear motion and fluid ingress, which may vary with contact force and area. It was hypothesised in this study that assembly forces modify the extent and distribution of the surface contact area at the taper interface between a cobalt chrome head and titanium stem taper with a standard threaded surface profile. Local abrasion of a thin gold coating applied to the stem taper prior to assembly was used to determine the contact area after disassembly. Profilometry was then used to assess permanent deformation of the stem taper surface profile. With increasing assembly force (500 N, 2000 N, 4000 N and 8000 N) the number of stem taper surface profile ridges in contact with the head taper was found to increase (9.2±9.3%, 65.4±10.8%, 92.8±6.0% and 100%) and the overall taper area in contact was also found to increase (0.6±0.7%, 5.5±1.0%, 9.9±1.1% and 16.1±0.9%). Contact was inconsistently distributed over the length of the taper. An increase in plastic radial deformation of the surface ridges (-0.05±0.14 μm, 0.1±0.14 μm, 0.21±0.22 μm and 0.96±0.25 μm) was also observed with increasing assembly force. The limited contact of the taper surface ridges at lower assembly forces may influence corrosion rates, suggesting that the magnitude of the assembly force may affect clinical outcome. The method presented provides a simple and practical assessment of the contact area at the taper interface.

The influence of stem taper re-use upon the failure load of ceramic heads

Ceramic components are frequently used in total hip replacement due to their good tribological properties. In revision of broken ceramic heads clinical uncertainties arise, whether the taper of the stem can be re-used with a new ceramic head, especially if the stem is well fixed. Ceramic is a brittle material. Even small damage on the male stem taper can lead to stress concentrations causing premature failure of a new ceramic head. As a consequence, manufactures strictly prohibit stem taper re-use for ceramic heads. The aim of this study was to determine the fracture strength of ceramic heads assembled to re-used male stem tapers, which were subjected to prior head fracture. Five 12/14 Ti6Al4V male tapers and 15 Al2O3 ceramic heads (BIOLOX forte(®); ∅ 28 mm, L) were used for three consecutive fracture tests. Before and after every fracture test, all components were inspected visually and the surface geometry was analyzed. Mean fracture force (52.5 kN) did not decrease with the number of taper re-uses (p ≥ 0.77) but the range increased significantly from initially 4.1 kN to 31.8 kN for the first and 52.6 kN for the second re-use due to some components failing at very low loads. Visual inspection was not sufficient to predict the reduced failure loads. Ceramic heads should therefore not be put on used male tapers without metal adapter sleeves.

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

BACKGROUND

The 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.

METHODS

The 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.

RESULTS

Different 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.

CONCLUSION

Asymmetric 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.

Retrieval analysis of new-generation yttria-stabilized zirconia femoral heads after total hip arthroplasty

Zirconia femoral heads were introduced for total hip arthroplasty (THA) with the expectation of lower polyethylene (PE) wear and better clinical results. Because several studies reported poor survivorship of yttria-stabilized zirconia-PE THA, we investigated a new-generation yttria-stabilized zirconia head (diameter, 26 mm) manufactured by NGK Spark Plug. We retrieved six zirconia heads at revision THA after they had been in place for a mean of 8.6 years and measured their surface roughness and mean monoclinic content. Although their mean monoclinic content was higher than that of the unused head, surface roughness in the implanted heads was as low as that of the unused head, indicating that wear reduction may be possible with the selection of a suitable zirconia femoral head.

Fracturing of Revision of a Cobalt-chrome Femoral Head after Fracturing of a Ceramic Femoral Head, with Diffuse Metallosis. Case Report

We presente a case of a fracture of a cobalt-chrome femoral head after revision of a hip total prosthesis with ceramic femoral head fracture. During surgery we found the cobalt- chrome femoral head fracture, wear of the polyethylene and massive metallosis in muscular and cartilaginous tissue. Both femoral stem and acetabular cup were stable and without apparent wearing. After surgical debridement, we promoted the substitution of the femoral head and the acetabular polyethylene by similar ones. After 12 months of follow- up, the patient has no pain complaints, function limit or systemic signs associated with malign metallosis.

Fracture of ceramic bearing surfaces following total hip replacement: a systematic review

Ceramic bearing surfaces are increasingly used for total hip replacement, notwithstanding that concern is still related to ceramic brittleness and its possible mechanical failure. The aim of this systematic review is to answer three questions: (1) Are there risk factors for ceramic component fracture following total hip replacement? (2) Is it possible to perform an early diagnosis of ceramic component failure before catastrophic fracture occurs? (3) Is it possible to draw guidelines for revision surgery after ceramic components failure? A PubMed and Google Scholar search was performed and reference citations from publications identified in the literature search were reviewed. The use of 28 mm short-neck femoral head carries an increased risk of fracture. Acetabular component malposition might increase the risk of ceramic liner fractures. Synovial fluid microanalysis and CT scan are promising in early diagnosis of ceramic head and liner failure. Early revision is suggested in case of component failure; no consensus exists about the better coupling for revision surgery. Ceramic brittleness remains a major concern. Due to the increased number of ceramic on ceramic implants, more revision surgeries and reports on ceramic components failure are expected in the future. An algorithm of diagnosis and treatment for ceramic hip failure is proposed.

In vitro evaluation of osteoconductivity and cellular response of zirconia and alumina based ceramics

Developed ceria/yttria stabilized zirconia and ceria/yttria stabilized zirconia toughened alumina supported formation of apatite layer when immersed in simulated body fluid without any prior surface treatment. The formed mineral layer was confirmed as hydroxyapatite through X-ray diffraction patterns. The calcium/phosphate atomic ratio obtained from energy dispersive X-ray spectroscopy was found to be little less (Ca/P=1.5) than that of pure hydroxyapatite (Ca/P=1.7) which indicates the probability of mixed type calcium-phosphate compound formation. The achieved thickness of apatite layer was estimated through a surface profilometer and as high as ~17 μm thickness was found after 28 days of soaking. The biocompatibility of the developed materials was ensured through in vitro human osteoblast like cell (MG63) culture on ceramic discs. The morphology of attached cells was characterized through scanning electron microscopy and fluorescent microscopy which show multilayered interconnected cell growth within 8 days of culture period. Moreover, differentiation of MG63 cells was evaluated through MTT assay, total protein content and alkaline phosphatase activity.

Abrasive wear and metallosis associated with cross-linked polyethylene in total hip arthroplasty

A 34-year-old female patient received a cobalt-chromium (CoCr) alloy femoral head on cross-linked polyethylene total hip replacement for the revision of her fractured ceramic-on-ceramic total hip replacement. The CoCr alloy femoral head became severely worn due to third-body abrasive wear by ceramic particles that could not be removed by synovectomy or irrigation at revision surgery. Ceramic particles were found embedded in the cross-linked polyethylene liner. The CoCr alloy femoral head exhibited a total mass loss of 14.2 g and the generated wear particles triggered metallosis in the patient. The present case study suggests not revising a fractured ceramic-on-ceramic total hip replacement with a CoCr alloy femoral head and a cross-linked polyethylene liner to avoid metallosis due to third-body abrasive wear.

Wear resistant performance of highly cross-linked and annealed ultra-high molecular weight polyethylene against ceramic heads in total hip arthroplasty

The purpose of this study was to examine the effects of ceramic femoral head material, size, and implantation periods on the wear of annealed, cross-linked ultra-high molecular weight polyethylene (UHMWPE) (XLPE) in total hip arthroplasty compared to non-cross-linked conventional UHMWPE (CPE). XLPE was fabricated by cross-linking with 60 kGy irradiation and annealing. Femoral heads made from zirconia and alumina ceramics and cobalt-chrome (CoCr) of 22 or 26 mm diameter were used. In this retrospective cohort study, the femoral head penetration into the cup was measured digitally on radiographs of 367 hips with XLPE and 64 hips with CPE. The average follow-up periods were 6.3 and 11.9 years, respectively. Both XLPE creep and wear rates were significantly lower than those of CPE (0.19 mm vs. 0.44 mm, 0.0001 mm/year vs. 0.09 mm/year, respectively). Zirconia displayed increased wear rates compared to alumina in CPE; however, there was no difference among head materials in XLPE (0.0008, 0.00007, and -0.009 mm/year for zirconia, alumina, and CoCr, respectively). Neither head size or implantation period impacted XLPE wear. In contrast to CPE, XLPE displayed low wear rates surpassing the effects of varying femoral head material, size, implantation period, and patient demographics. Further follow-up is required to determine the long-term clinical performance of the annealed XLPE.

Wear comparison between a highly cross-linked polyethylene and conventional polyethylene against a zirconia femoral head: minimum 5-year follow-up

Highly cross-linked polyethylene (HXLPE) was developed to reduce wear of articular bearing surface in total hip arthroplasty patients. Several studies have shown reduced wear of HXLPE compared with conventional polyethylene; however, these studies had used HXLPE in combination with a Co-Cr metal head. The purpose of this study was to compare the 5-year in vivo wear of HXLPE with that of conventional PE using a zirconia femoral head. Forty-five hips with a Trilogy HXLPE (Zimmer, Warsaw, Ind) were matched and compared with a control group of 20 conventional Trilogy PE hips. The 2-dimensional linear wear rate was significantly less in the HXLPE group between 1 and 5 years postoperation (P < .001). The results show that HXLPE reduces short-term polyethylene wear against not only a Co-Cr head but also a zirconia head.

Revision total hip arthroplasty for ceramic head fracture: a long-term follow-up

The results of revision total hip arthroplasty (THA) for ceramic head fracture have generally been disappointing, largely due to third body wear after incomplete synovectomy. We have followed 8 patients who sustained ceramic head fractures and were subsequently revised to a metal-on-polyethylene articulation. There were no revisions for osteolysis or aseptic loosening at a mean follow-up of 10.5 years. The yearly wear rates of each of 5 of these THAs after revision were compared with 6 matched metal-on-polyethylene THAs; there were no significant differences in wear rates. Greater than 10-year survivorship with a metal-on-polyethylene bearing couple is possible after revision THA for a ceramic head fracture if a complete and thorough synovectomy can be performed. Our technique of synovectomy will be described.

Proof testing of ceramic femoral heads for hip joint implants

A proof test procedure for the rejection of defective ceramic hip ball heads in the production line is presented. The procedure consists of applying a load to each ceramic ball head. This load, being somewhat higher than the maximum physiological load, should not cause any damage in cases where the highly stressed areas are free of flaws. In this procedure, a polymer ring is positioned inside the ball head bore between a socket and the head of a tie bolt. Once the tie bolt is pulled downwards, the ring creates a radial pressure on the inner bore surface of the ball head. With an iterative approach based on finite element analysis, the proof test design was optimized in order to obtain a stress distribution in the ball head similar to that resulting in in vivo conditions. The calculated results were validated by strain gauge measurements performed on an assembled proof test apparatus. Several polymers were considered for the ring. Ultrahigh-molecular-weight polyethylene (UHMWPE grade RCH 1000) showed the best durability properties and lowest wear rates. The requirement to perform 1000 reruns without significant reduction of stress in the ball head was fulfilled. Although other proof test procedures for ceramic femoral heads already exist, the procedure presented in this article shows advantages concerning maintenance and operating costs.

Manufacturers affect clinical results of THA with zirconia heads: a systematic review

In the 1980s, zirconia was introduced for THA with the expectation of lower polyethylene wear and better clinical results. However, several studies have reported poor survivorship of zirconia-polyethylene THA. We performed a systematic review and meta-analysis of zirconia-polyethylene THA to confirm or refute the theoretical advantages of this combination. Of 163 studies identified by a comprehensive search, seven met our selection criteria. These involved 769 hips of 586 patients with a mean age of 56.8 years and a minimum followup of 60 months (mean, 89.2 months; range, 60-155 months). The consolidated revision rate of zirconia-polyethylene THA at 89.2 months was higher than that of nonzirconia-polyethylene THA by 5% (risk difference, 0.05; 95% confidence interval, 0.02-0.08). Subgroup meta-analysis suggested THAs with zirconia heads from Ceraver had more revision surgery than nonzirconia heads (risk difference, 0.08; 95% confidence interval, 0.03-0.14), whereas zirconia heads from DePuy did not (risk difference, 0.02; 95% confidence interval, -0.01-0.06). The meta-analysis for annual linear polyethylene wear (which did not involve zirconia heads from Ceraver because of insufficient descriptions) showed no difference between zirconia and control groups. Collectively, THAs with high-quality zirconia heads appear to have prosthesis survivorship and polyethylene wear equivalent to those of THAs with traditional materials, but differing quality among zirconia heads could lead to poor survivorship of prostheses.

Extremely high fracture rate of a modular acetabular component with a sandwich polyethylene ceramic insertion for THA: a preliminary report

Improvements of ceramic components and design changes have reduced failure rates over the past 30 years in total hip arthroplasty. We present a series of n = 11 cases with ceramic failure out of n = 113 implantations, from which n = 66 were ceramic-on-ceramic (n = 50 with ceramic insert with sandwich in polyethylene and n = 16 with directly fixed ceramic inlay) and n = 47 ceramic on polyethylene bearings, between 1999 and 2001 after introduction of a new implantation system to the market. The overall fracture rate of ceramic for the whole series (n = 113) was 9.7%. For the combination ceramic head with UHMW-PE (n = 47) the fracture rate was 2.1%. For the combination ceramic with ceramic (n = 66) the fracture rate was 15.2%. For the combination ceramic with ceramic sandwich in PE (n = 50) the failure rate was 18%. Only three patients experienced a trauma. Demography of patients (age, gender, body weight and BMI) was not statistically different between patients with failed ceramics and the rest of the patients making patient-specific risk factors unlikely to be an explanation for the failures. Retrospective X-ray analysis of the cup positioning did not show significant difference between failed and non-failed implants in terms of mean cup inclination and version making also operation-specific factors unlikely to be the only reason of this high failure rate. Therefore, manufacturer-specific factors such as design features may have contributed to this high failure rate. Further analysis of the whole series with biomechanical testing of the retrieved material needs to be performed.

Optimization of the stress distribution in ceramic femoral heads by means of finite element methods

Ceramic ball heads for total hip replacement are highly loaded in vivo and must meet the sternest requirements concerning strength and safety. High stresses inside the ball head originate from the press fit between the conical stem (made of titanium alloy or steel) and the borehole of the ball. The aim of this study was the development of an optimized contour at the fillet inside the ball head by means of numerical methods, in order to reduce local stress concentrations. The computer-aided optimization method was applied on the customary engineering fillet radius to reduce local stress peaks. The local notch stress of the examined ball head design was reduced by up to 27 per cent for the relevant load cases. Verification by rupture testing of prototypes turned out to be difficult for axisymmetric load cases, since the static fracture load is governed by the hoop stresses in the contact area of the taper (global maximum), thus making it difficult to prove a local improvement. The sensitivity of the design to asymmetric loading was clearly shown (varying the load angle and bearing type). Stress relocation in the ball—stem interface at higher burst loads indicated the necessity of optimizing each ceramic femoral head design individually (i.e. for different borehole depths).

Influence of contaminants in the stem—ball interface on the static fracture load of ceramic hip joint ball heads

The probability of in-vivo failure of ceramic hip joint implants is very low (0.05–0.004 per cent). Besides material flaws and overloading, improper handling during implantation may induce fractures of the ceramic ball head in the long term. This study focuses on the influence of contaminants located in the stem—ball interface and on the use of damaged metal tapers on the strength of ceramic ball heads. Mechanical tests on alumina ball heads according to the standard ISO 7206-10 were performed to identify their effect on the static fracture load. A decrease of up to 90 per cent with respect to the reference static fracture load was found when contaminants such as bone chips, soft tissue, or blood were present. Reductions of 57 per cent and 27 per cent were observed for deformed stem cross-sections (from circular to elliptical) and for flattened stems respectively, making deformed stems another influential parameter. Since any alteration of the interface between the metal taper and the ceramic ball head yields a non-uniform load introduction and hence results in stress concentrations, its presence has to be avoided.

Alumina femoral head fracture in uncemented total hip arthroplasty with a ceramic sandwich cup

In total hip arthroplasty, insertion of a UHMWPE-coated ceramic sandwich liner dramatically reduces any risk related to the stiffness of the ceramic-ceramic coupling. We present a case of an alumina ceramic head fracture with a ceramic sandwich cup. The fracture occurred 16 months after the initial operation, without trauma. Impingement between the neck and posteroinferior portion of the liner rim had occurred. This was related to the traditional cross-legged sitting position of Koreans, which caused impingement between the neck and liner rim. Consequently, the taper became loose, and the resulting force bent the taper and fractured the head. We examined a peculiar case of ceramic femoral head fracture after implantation of an uncemented total hip arthroplasty with a ceramic sandwich cup and investigated the underlying cause.

Extensive intrapelvic granuloma formation caused by ceramic fragments after revision total hip arthroplasty

Ceramic debris embedded in a polyethylene liner was identified as the cause for rapid metal wear after revision total hip arthroplasty when a broken ceramic head was replaced by a metal head. Removal of an intrapelvic foreign body granuloma and rerevision hip arthroplasty had to be performed within 2 years after the first revision.

Zirconia versus Co-Cr femoral heads in total hip arthroplasty: early assessment of wear

Polyethylene wear and associated osteolysis are major limitations to the long-term success of total hip arthroplasty. In vitro laboratory studies suggest polyethylene wear in THA may be substantially reduced with ceramic femoral heads. We evaluated the potential value of zirconia ceramic on conventional polyethylene as an "alternative bearing" for total hip arthroplasty in a prospective, randomized clinical trial in comparison with femoral heads made of Co-Cr-Mo. Patients were evaluated with standardized clinical outcome instruments, and measurement of head penetration was performed with computerized wear measurement software. Study enrollment was halted because of a recall of the zirconia heads. At that time, 30 total hip arthroplasties with Co-Cr-Mo heads and 30 total hip arthroplasties with zirconia heads had been performed. Mean followup was similar for both groups (Co-Cr- Mo = 51.7 months; zirconia = 51.2 months). The mean annual head penetration rate was low and similar for both groups (Co-Cr-Mo = 0.060 mm/year; and zirconia = 0.055 mm/year). In view of the recently reported potential for zirconia ceramics to undergo monoclinic phase transformation in vivo, with resultant increased fracture risk and degradation of wear properties, we do not recommend use of zirconia femoral heads as an "alternative bearing" for total hip arthroplasty.

Fracture of a ceramic femoral head after ceramic-on-ceramic total hip arthroplasty

A case of fracture of the ceramic head of a total hip arthroplasty is presented, which was a total cementless arthroplasty with ceramic-on-ceramic articulation. No history of trauma was observed. The arthroplasty was revised, and a new cementless arthroplasty with a polyethylene insert and a metal head was inserted. The result has been satisfactory.

Effect of alumina femoral head on clinical results in cemented total hip arthroplasty: old versus current alumina

BACKGROUND

The wear rate of polyethylene against alumina was demonstrated to be lower than against metal, and the results of early clinical studies of alumina-on-polyethylene combination were as good as expected, but the long-term results of alumina ceramic heads were not as good, as reported by several authors. The purpose of this study was to assess the clinical results over 10 years of cemented total hip arthroplasty (THA) with two types of alumina head: old and current alumina.

METHODS

We compared the clinical results of these two types of alumina used for cemented THA. The first type was old alumina (containing 7% yttria), and 77 hips with a 28-mm head (group I) were included. The second type was current alumina (highly purified alumina), and 50 hips with a 26-mm head (group II) and 88 hips with a 22-mm head (group III) were included. The mean follow-up was 17 years 4 months in group I, 12 years 3 months in group II, and 10 years in group III.

RESULTS

The Kaplan-Meier survival analysis, with revision for any reason as the endpoint, predicted 10-year survival rates of 90.8%, 100%, and 97.5% for groups I, II, and III, respectively. The survival curves differed significantly only between groups I and II. The probabilities of 10-year survival of the pros-theses with radiological loosening as the endpoint were 77.2%, 91.6%, and 96.5%, respectively. The survival curves showed significant differences only between groups II and III.

CONCLUSIONS

The old alumina showed a higher wear rate and rougher surface on the femoral head than did the current alumina in our previous study. The clinical results also indicated superiority of current alumina over old alumina. The difference in the size of the femoral head (26 vs. 22 mm) did not affect the clinical results.

Fractures of ceramic bearings: history and present status

During a period of 25 years (1977 to 2001), 13 fractures of an alumina component were recorded retrospectively. During the same period, approximately 5500 alumina components were implanted (3300 with all-alumina bearings and 1200 with alumina-on-polyethylene). These events occurred in seven women and six men, with a mean age of 59 years and a mean weight of 71 kg. There were eight fractures of the femoral head and five fractures of the socket component. Three fractures clearly were related to trauma (two fractures of the socket and one fracture of the head) and two were related to an abnormal design (one 22-mm head and one extra-long neck). Five fractures occurred without any rational explanation, but two fractures that occurred in the early phase could have been caused by a weaker alumina material. Finally three recent fractures of the liner were related to a change in the design of the material. This has been corrected and no additional fractures were observed. Although this dramatic event is of concern, it is infrequent and easy to solve by a limited revision procedure if done emergently. This rare complication should be balanced with the other complications of THR, including mechanical failures and osteolysis, often described with metal-on-polyethylene prostheses.

Ceramic acetabular liner fracture in total hip arthroplasty with a ceramic sandwich cup

In total hip arthroplasty, a modular acetabular component with a sandwich insertion (alumina ceramics/polyethylene/titanium) was proposed. The polyethylene layer might reduce the rigidity of the ceramics and prevent an impingement between the ceramic liner rim and the femoral neck. A case of an acetabular liner fracture of the ceramic sandwich cup was presented. The fracture occurred 1.4 years after the operation without trauma. Because the ceramic liner rim was hit by the head following the impingement between the neck and the polyethylene, the cause of the fracture might be the stress concentration at the rim of the ceramic liner, of which the thickness was only 4 mm. At revision surgery, the fractured ceramic liner was replaced with a polyethylene liner without inner ceramic liner.

Revision total hip arthroplasty performed after fracture of a ceramic femoral head. A multicenter survivorship study

BACKGROUND

The alumina ceramic femoral head was introduced for total hip arthroplasty approximately thirty years ago. One of its main drawbacks was the risk of implant fracture. The aim of this study was to examine the results of revision total hip replacement performed specifically to treat a fracture of a ceramic femoral head and to identify technical factors that affected the outcomes.

METHODS

One hundred and five surgical revisions to treat a fracture of a ceramic femoral head, performed at thirty-five institutions, were studied. The patients were examined clinically by the operating surgeon at the time of the last follow-up. The surgeon provided the latest follow-up radiographs, which were compared with the immediate postoperative radiographs. The success of the revisions was assessed with Kaplan-Meier survivorship analysis, with the need for repeat revision as the end point. We evaluated the complication rate and radiographic changes indicative of implant loosening. The average duration of follow-up between the index revision and the last clinical and radiographic review was 3.5 years (range, six months to twenty years).

RESULTS

Following the revisions, radiographic evidence of cup loosening was seen in twenty-two hips (21%) and radiographic evidence of femoral loosening was seen in twenty-two (21%). One or several repeat revisions were necessary in thirty-three patients (31%) because of infection (four patients), implant loosening (twenty), osteolysis (eight), or fracture of the revision femoral head component (one). The survival rate at five years was 63% (95% confidence interval, 51% to 75%). The survival rate was significantly worse when the cup had not been changed, when the new femoral head was made of stainless steel, when a total synovectomy had not been done, and when the patient was less than fifty years old.

CONCLUSIONS

Fracture of a ceramic femoral head component is a rare but potentially serious event. A suitable surgical approach, including total synovectomy, cup exchange, and insertion of a cobalt-chromium or new ceramic femoral ball minimizes the chance of early loosening of the implants and the need for one or more repeat revisions.

LEVEL OF EVIDENCE

Therapeutic study, Level IV (case series [no, or historical, control group]).

[Fracture analysis of a ceramic liner. Is in hip endoprosthesis replacement of ceramic on ceramic components with only one of the corresponding partners justified?]

The good biomechanical and tribological properties, together with the excellent biocompatibility, of ceramic-on-ceramic components, make them a preferential choice for total hip replacement surgery, at least in Europe. We report on a man admitted as an outpatient with painless grating in the hip one year after replacement of a ceramic femoral head, but not of the ceramic inlay. Clinical and radiological findings were indicative of a broken liner. This was confirmed during revision surgery, during which it was replaced by a polyethylene inlay; although the ceramic head appeared intact, it was replaced by a metal head. Inspection of the surface of the broken liner in the scanning electron microscope (SEM) revealed signs of material failure. We recommend careful inspection of ceramic-on-ceramic articulating components during total hip revision surgery and if there is any uncertainty, replacement of both so as to avoid premature failure.

The wear of a polyethylene socket articulating with a zirconia ceramic femoral head in canine total hip arthroplasty

Wear of yttria-zirconia (zirconia) in the femoral head was investigated in mature mongrel dogs weighing 10 to 13 kg. Two dogs, which were used as a control group, were sacrificed 18 months after implantation of the uncemented modular hip system with an alumina ceramic (alumina) femoral head. A zirconia femoral head was implanted in five dogs: one was sacrificed 12 months after implantation, two at 18 months, and two at 24 months. In each femoral head and polyethylene (PE) socket, the surface was observed by means of scanning electron microscopy (SEM); the mean articulation surface roughness on the femoral head and PE socket and the thickness of the PE socket were measured. Wear was not seen on the surface of either the zirconia or the alumina heads. In both groups, minute white spots on the smooth surface of the PE socket were visible by SEM. In the alumina and zirconia groups the mean roughness was 0.1 microm. The mean thickness of the PE socket was reduced by 0.2 mm in the alumina group. In the zirconia group it was reduced by 0.2 to 0.3 mm. However, the mechanical strength of zirconia is known to be greater than that of alumina and it may be possible to reduce the diameter of the femoral head. The smaller zirconia head may contribute to the reduction of the wear of the PE socket in an uncemented modular total hip system.

Cementless bulk alumina socket: preliminary results at 6 years

To avoid polyethylene wear observed in total hip replacement, an alumina-alumina combination has been used since 1977. The aim of this study is to report the results of a hybrid alumina-alumina total hip arthroplasty with a cementless press-fit bulk alumina socket and a cemented titanium alloy stem in 55 patients (62 hips) operated on between 1982 and 1990. The bearing surfaces were a 32-mm alumina head articulating within the alumina socket. Four failures occurred: 3 aseptic loosenings of the socket and 1 femoral head fracture. Considering aseptic loosening as the endpoint, the survival rate was 93.2% after 6 years. At a mean of 72.1 months' follow-up, 92.4% of the surviving hips were graded as very good or good using the Merle d'Aubigné-Postel hip score. Radiolucent lines were observed on the acetabular side in 68.1 of the hips. The future of this interface, which is probably fibrous, remains questionable. With the exception of 1 femoral head fracture, all revisions were related to failure of the bony fixation of the socket, and no problem was encountered related to the alumina-alumina friction coupling. Alumina sockets with other types of cementless fixation have therefore been designed and are presently under clinical investigation.