Fractures of a sandwich ceramic liner at ten year follow-up

Long-term follow-up of total hip arthroplasty using polyethylene-ceramic composite (sandwich) liner

INTRODUCTION

Ceramic-on-ceramic bearings have been widely used since their introduction in the 1970s. First-generation ceramics have very high fracture (breakage) rates. To overcome this, in the 1990s, modular cotyloid insert designs were developed, consisting of a ceramic and polyethylene composite (sandwich-type) liner; however, high implant fracture rates were observed in the medium term. We aimed to estimate the cumulative incidences of revision surgery (implant failure) and implant failure due to fractures, survival rates (time-to-revision surgery and time-to-fracture), and the long-term clinical and radiological outcomes in our series.

METHODS

This was an observational, longitudinal, ambispective, single-centre study based on patients who underwent primary total hip arthroplasty (THA) using a sandwich-type liner (Cerasul), only available in our tertiary hospital between January 1999 and December 2002. Cumulative incidences were estimated and the 95% confidence interval (95% CI) was calculated. The Kaplan-Meier method was used to assess the time-to-revision surgery and time-to-fracture.

RESULTS

54 patients (49 men) were included, accounting for 59 sandwich-type linear implants. The mean (range) age was 47.4 (22-57) years. The primary THA indications were osteoarthritis (28 patients), osteonecrosis (14), childhood pathology sequelae (11), and inflammatory arthritis (6). The cumulative incidence of revision surgery by implants was 8.5% (5/59, 95% CI, 3.5-19.2%), 9.3% by patients (5/54, 95% CI, 4.0-19.9%), and 5.1% by implant fractures (3/59, 95%CI, 1.7-13.9%). The median (Interquartile Range, IQR) time-to-revision surgery was 158 (72.5-161) months, and the time to fracture was 182 (138-215) months. All primary THAs had good clinical and long-term survival outcomes. All implants had signs of solid fixation.

CONCLUSIONS

After a 20-year follow-up period, the polyethylene-ceramic sandwich-type liner showed a long survival rate and low cumulative incidence of implant fracture; however, implant fractures remain the main complication. Orthopaedic surgeons should be aware that some patients still have this type of prosthesis and must be capable of responding quickly if a fracture occurs.

Ceramic fragmentation after total hip arthroplasty: two case reports and literature review

Background

Ceramic fragmentation is a rare but serious complication after total hip arthroplasty (THA). We reviewed the PubMed literature from 1990 to 2023 and found only 31 case reports of ceramic fragmentation after THA. Our case reports help to expand understanding of this rare complication. We shared our surgical experience and identified an ideal material for revision surgery, which can serve as a useful reference for other orthopedic surgeons to perform ceramic fragmentation revision surgery in the future. We also analyzed the possible causes, diagnosis, and treatment opinions of ceramic fragmentation.

Case presentation

This study presents two cases of ceramic fragmentation after THA. One patient had ceramic head fragmentation 10 years after the primary THA, and one patient had ceramic liner fragmentation 5 years after the primary THA. Both patients presented with pain, and one patient also reported a clicking sound in the hip. The two patients described here had BMIs of 23.7 and 23.1, respectively. Both patients' ceramic fragmentation were due to aseptic loosening, not periprosthetic joint infections, as confirmed by negative microbiological cultures. Radiographic examinations of both patients revealed radio-opaque wear debris around the hip joint prostheses and we describe the surgical protocols and intraoperative findings in both cases in detail.

Conclusion

Our cases and the literature suggest that ceramic fragmentation can occur at any time after THA. The most immediate symptoms are pain and noise, but some patients may be asymptomatic. Ceramic on polyethylene bearings is recommended for revision surgery whenever possible; metal bearings should be avoided.

A multi-center retrospective comparative study of third generation Ceramic-on- Ceramic total hip arthroplasty in patients younger than 45 years with or without the sandwich liner: A ten-year minimum

BACKGROUND

Ceramic-on-ceramic couplings are attractive alternative bearing surfaces that have been reported to eliminate or reduce problems related to polyethylene wear debris. However, the material in THA still remains one of the major concerns about the risk of fracture, due to its brittleness.

OBJECTIVE

The present study aims at reporting the fracture rate of a series of ceramic-on-ceramic THAs with use of the sandwich liner combined with a ceramic femoral head, and attempt to detect the relative risk factors, possible cause and assesse the medium-term clinical results.

METHODS

We retrospectively evaluated 282 patients (300 hips) with use of the sandwich liner ceramic-on-ceramic THA between 2001 and 2009 at three-centers. Patient assessment was based on demographic factors, including age, weight, gender and body-mass index. All patients were evaluated clinically and radio-graphically or computed tomography in consideration of dislocation, osteolysis, periprosthetic fracture, infection, loosening and implant fracture.

RESULTS

five ceramic sandwich liners fracture (1.7%) were observed at an average of 7.3 years follow-up. These factors were irrelevant to the ceramic liner fracture, including age (p = 0.205), weight (p = 0.241), gender (p = 0.553), body-mass index (p = 0.736), inclination (p = 0.727), and anteversion (p = 0.606). The overall survival was 91.4% at 12 years with revision as the endpoint. Other complications included dislocation in two, perprosthetic fracture in two and osteolysis in eight hips. No hip had aseptic loosening of the implants was seen.

CONCLUSIONS

We found that the sandwich liner may be lead to a high rate of alumina fracture and osteolysis. We have discontinued the use of sandwich liner with THA since 2009.

Metasul vs Cerasul bearings: a prospective, randomized study at a mean eighteen years

BACKGROUND

The aims of our study were to compare the clinical, radiographic outcomes and survivals between second-generation metal-on-metal (Metasul) and ceramic-on-ceramic (Cerasul) bearings at a very long-term follow-up.

METHODS

A prospective, randomized study was originally performed on a consecutive series of 250 cementless, 28-mm head and primary total hip arthroplasties between 1999 and 2002. For each bearing (Metasul or Cerasul), 125 THAs were initially included. All cases were evaluated both clinically and radiographically, and survival was assessed, considering revisions for aseptic loosening or for any reason as the end points for failure.

RESULTS

At a mean 18-year follow-up, clinical and radiographic outcomes were similar. Harris Hip Score increased 30% in the Metasul group and 32% in the Cerasul group (p = 0.6). Survival free of aseptic loosening was higher for Cerasul (100%), than for Metasul (94% [CI 88-99.9]) (p = 0.04). Survival free of any revision was 91% ([CI 84-98%]) for Cerasul and 91% ([CI 84-98%]) for Metasul. Fractures of Cerasul insert occurred in four cases (3%) at a mean 12.5 ± 3.3 years (range, 6 to 17 years).

CONCLUSION

At 18 years, Cerasul demonstrated higher survivorship than Metasul considering aseptic loosening as an end point. However, Cerasul liners had high rate of fracture because of its sandwich design (thin ceramic liner into polyethylene). These implants are no more available on the market.

Stress and strain distribution in femoral heads for hip resurfacing arthroplasty with different materials: A finite element analysis

Femoral bone loss due to stress and strain shielding is a common problem in hip resurfacing arthroplasty (HRA), which arises from the different stiffness of implant materials and the adjacent bone. Usually, the implants used in HRA are made of cobalt-chromium alloy (CoCr). As a novel concept, implants may also be made of ceramics, whose stiffness exceeds that of the adjacent bone by a multiple. Therefore, this computational study aimed to evaluate whether poly (ether-ether-ketone) (PEEK) or a hybrid material with a PEEK body and ceramic surface made of alumina toughened zirconia (ATZ) might be more suitable implant alternatives for HRA, as they can avoid stress and strain shielding. A reconstructed model of a human femur with an HRA implant was simulated, whereby the material of the HRA was varied between CoCr, ATZ, zirconia toughened alumina (ZTA), PEEK, and a hybrid PEEK-ATZ material. The implant fixation method also varied (cemented or cementless). The simulated models were compared with an intact model to analyze stress and strain distribution in the femoral head and neck. The strain distribution was evaluated at a total of 30,344 (cemented HRA) and 63,531 (uncemented HRA) nodes in the femoral head and neck region and divided into different strain regions (<400 µm/m: atrophy; 400-3000 μm/m: bone preserving and building; 3000-20,000 μm/m: yielding and >20,000 μm/m fracture). In addition, the mechanical stability of the implants was evaluated. When the material of the HRA implant was simulated as metal or ceramic while evaluating the strains, it was seen that around 22-26% of the analyzed nodes in the femoral head and neck were in an atrophic region, 47-51% were in a preserving or building region, and 27-28% were in a yielding region. In the case of PEEK implant, less than 0.5% of the analyzed nodes were in an atrophic region, 66-69% in a preserving or building region, and 31-34% in a yielding region. The fixation technique also had a small influence. When a hybrid HRA was simulated, the strains at the analyzed nodes depended on the thickness of the ceramic material. In conclusion, the material of the HRA implant was crucial in terms of stress and strain distribution in the adjacent bone. HRA made of PEEK or a hybrid material leads to decisively reduced stress and strain alteration compared to stiffer materials such as CoCr, ATZ, and ZTA. This confirms the potential for reduction in stress and strain shielding in the femoral head with the use of a hybrid material with a PEEK body for HRA.

Influence of the Acetabular Cup Material on the Shell Deformation and Strain Distribution in the Adjacent Bone-A Finite Element Analysis

In total hip arthroplasty, excessive acetabular cup deformations and altered strain distribution in the adjacent bone are potential risk factors for implant loosening. Materials with reduced stiffness might alter the strain distribution less, whereas shell and liner deformations might increase. The purpose of our current computational study was to evaluate whether carbon fiber-reinforced poly-ether-ether-ketones with a Young´s modulus of 15 GPa (CFR-PEEK-15) and 23 GPa (CFR-PEEK-23) might be an alternative shell material compared to titanium in terms of shell and liner deformation, as well as strain distribution in the adjacent bone. Using a finite element analysis, the press-fit implantation of modular acetabular cups with shells made of titanium, CFR-PEEK-15 and CFR-PEEK-23 in a human hemi-pelvis model was simulated. Liners made of ceramic and polyethylene were simulated. Radial shell and liner deformations as well as strain distributions were analyzed. The shells made of CFR-PEEK-15 were deformed most (266.7 µm), followed by CFR-PEEK-23 (136.5 µm) and titanium (54.0 µm). Subsequently, the ceramic liners were radially deformed by up to 4.4 µm and the polyethylene liners up to 184.7 µm. The shell materials slightly influenced the strain distribution in the adjacent bone with CFR-PEEK, resulting in less strain in critical regions (<400 µm/m or >3000 µm/m) and more strain in bone building or sustaining regions (400 to 3000 µm/m), while the liner material only had a minor impact. The superior biomechanical properties of the acetabular shells made of CFR-PEEK could not be determined in our present study.

Midterm outcome of fourth-generation ceramic-on-ceramic bearing surfaces in revision total hip arthroplasty

PURPOSE

The purpose of this study is to evaluate the clinical and radiologic outcomes after revision total hip arthroplasty (THA) using fourth-generation ceramic-on-ceramic (CoC) bearing surfaces.

METHODS

A total of 52 revision THAs (28 men and 19 women) using the fourth-generation CoC bearing surfaces were retrospectively evaluated. Both acetabular cup and femoral stem were revised in all cases. The mean follow-up period was 7.3 years (range, 4.0-9.9 years). The clinical results with Harris hip score (HHS), Western Ontario McMaster Osteoarthritis Index (WOMAC), and radiologic outcomes were evaluated.

RESULTS

At the final follow-up examination, the average HHS was 90.4 (range, 67-100). The average WOMAC pain and physical function score were 2.8 (range, 0-12) and 16.4 (range, 0-42), respectively. Complications were observed in 10 hips (19.2%). However, there were no bearing surface-related complications, and no cases of dislocation and squeaking. Retroacetabular pelvic osteolysis without cup loosening was observed in one hip at the final follow-up. However, no hip showed radiographic signs of cup loosening, vertical or horizontal acetabular cup migrations, and changes of inclinations during the follow-up period.

CONCLUSION

Our data showed that clinical and radiologic outcomes after revision THA using fourth-generation CoC bearing were favorable. Hence, revision THA with the use of CoC bearing surfaces can be preferentially considered. Further studies with long-term follow-up data are warranted.

Biomechanical behavior of modular acetabular cups made of poly-ether-ether-ketone: A finite element study

After total hip arthroplasty, stress-shielding is a potential risk factor for aseptic loosening of acetabular cups made of metals. This might be avoided by the use of acetabular cups made of implant materials with lower stiffness. The purpose of this numerical study was to determine whether a modular acetabular cup with a shell made of poly-ether-ether-ketone or poly-ether-ether-ketone reinforced with carbon fibers might be an alternative to conventional metallic shells. Therefore, the press-fit implantation of modular cups with shells made of different materials (Ti6Al4V, poly-ether-ether-ketone, and poly-ether-ether-ketone reinforced with carbon fibers) and varying liner materials (ceramics and ultra-high-molecular-weight polyethylene) into an artificial bone cavity was simulated using finite element analysis. The shell material had a major impact on the radial shell deformation determined at the rim of the shell, ranging from 17.9 µm for titanium over 92.2 µm for poly-ether-ether-ketone reinforced with carbon fibers up to 475.9 µm for poly-ether-ether-ketone. Larger radial liner deformations (up to 618.4 µm) occurred in combination with the shells made of poly-ether-ether-ketone compared to titanium and poly-ether-ether-ketone reinforced with carbon fibers. Hence, it can be stated that conventional poly-ether-ether-ketone is not a suitable shell material for modular acetabular cups. However, the radial shell deformation can be reduced if the poly-ether-ether-ketone reinforced with carbon fiber material is used, while deformation of ceramic liners is similar to the deformation in combination with titanium shells.

Ceramic-on-ceramic bearing fractures in total hip arthroplasty

Aims

Ceramic-on-ceramic (CoC) bearings in total hip arthroplasty (THA) are commonly used, but concerns exist regarding ceramic fracture. This study aims to report the risk of revision for fracture of modern CoC bearings and identify factors that might influence this risk, using data from the National Joint Registry (NJR) for England, Wales, Northern Ireland and the Isle of Man.

Patients and Methods

We analysed data on 223 362 bearings from 111 681 primary CoC THAs and 182 linked revisions for bearing fracture recorded in the NJR. We used implant codes to identify ceramic bearing composition and generated Kaplan-Meier estimates for implant survivorship. Logistic regression analyses were performed for implant size and patient specific variables to determine any associated risks for revision.

Results

A total of 222 852 bearings (99.8%) were CeramTec Biolox products. Revisions for fracture were linked to seven of 79 442 (0.009%) Biolox Delta heads, 38 of 31 982 (0.119%) Biolox Forte heads, 101 of 80 170 (0.126%) Biolox Delta liners and 35 of 31 258 (0.112%) Biolox Forte liners. Regression analysis of implant size revealed smaller heads had significantly higher odds of fracture (chi-squared 68.0, p < 0.001). The highest fracture risk was observed in the 28 mm Biolox Forte subgroup (0.382%). There were no fractures in the 40 mm head group for either ceramic type. Liner thickness was not predictive of fracture (p = 0.67). Body mass index (BMI) was independently associated with revision for both head fractures (odds ratio (OR) 1.09 per unit increase, p = 0.031) and liner fractures (OR 1.06 per unit increase, p = 0.006).

Conclusions

We report the largest independent study of CoC bearing fractures to date. The risk of revision for CoC bearing fracture is very low but previous studies have underestimated this risk. There is good evidence that the latest generation of ceramic has greatly reduced the odds of head fracture but not of liner fracture. Small head size and high patient BMI are associated with an increased risk of ceramic bearing fracture. Cite this article: Bone Joint J 2017;99-B:1012–19.

Revision of ceramic fracture with ceramic-on-polyethylene in total hip arthroplasty: Medium-term results

There is no consensus on the bearing of choice in revision for ceramic fracture after total hip arthroplasty (THA). The aim of this study was to evaluate the outcomes using ceramic-on-polyethylene (CoP) articulation in revision for ceramic breakage. Twelve patients who underwent revision hip surgery between 2002 and 2013 were followed-up. Appropriate surgical technique, including accurate synoviectomy, was used. The cup and the head were changed in four patients and only the liner and the head were replaced in the remaining eight patients. At the final follow-up there were no cases of re-revision due to tribological reasons, and only one case of polyethylene (PE) wear and osteolysis was scheduled for a new revision because of clear cup malposition. Complications were four cases of dislocation, one case of loosening and one case of infection. Revision of fractured ceramic is a challenging situation with a high risk of early complications. Using CoP liners with accurate synoviectomy and correction of misalignment can be considered a valuable bearing option at medium-term follow-up.

Ceramic-on-ceramic bearings total hip arthroplasty in young patients

Background

The results of ceramic-on-ceramic (CoC) total hip arthroplasty (THA) in younger patients were not univocal. This study aims to evaluate the results of CoC bearing THA in patients younger than 50 years.

Methods

A total of 90 younger patients performed CoC THAs during March 2003 and May 2008 were included in this study. Hip function and activity were evaluated with Harris hip score and University of California Los Angeles activity score. We had discussed survival rates, radiological findings of component loosening or osteolysis, and ceramic-related complications in these patients.

Results

The mean Harris hip score increased from 46.3 ± 12.0 points (range, 28-70 points) before surgery to 92.5 ± 5.6 points (range, 78-100 points) at the final follow-up. The mean preoperative University of California Los Angeles activity score was 4.2 ± 1.1 points (range, 2-6 points), which improved to a mean of 7.2 ± 1.3 points (range, 4-10 points). At the time of the last follow-up, there was found to be 1 occurrence of hip dislocation, 1 squeaking, and 2 “sandwich” ceramic liners fractured during normal activity of daily living. No hips showed osteolysis or required revision for aseptic loosening. Kaplan-Meier survivorship with revision due to loosening or osteolysis was 100% and with revision due to ceramic fracture was 97.3% (95% confidence interval, 93.7%-100%) at a mean of 9.4 years.

Conclusions

This study with the use of CoC bearings THAs in younger patients have shown promising results and higher rate of survivorship without evidence of osteolysis.

Is there any difference in survivorship of total hip arthroplasty with different bearing surfaces? A systematic review and network meta-analysis

PURPOSE

Although many total hip bearing implants are widely used all over the world, simultaneous comparisons across the numerous available bearing surfaces are rare. The purpose of this study was to compare the survivorship of total hip arthroplasty (THA) with six available bearing implants.

METHODS

We conducted a systematic review of randomized controlled trials (RCTs) reporting survivorship or revision of ceramic-on-ceramic (CoC), ceramic-on-conventional polyethylene (CoPc), ceramic-on-highly-crosslinked polyethylene (CoPxl), metal-on-conventional polyethylene (MoPc), metal-on-highly-crosslinked polyethylene (MoPxl), or metal-on-metal (MoM) bearing implants. The synthesis of present evidence was performed by both the traditional direct-comparison meta-analysis and network meta-analysis.

RESULTS

In total, 40 RCTs involving a total of 5321 THAs were identified. The pooled data of network meta-analysis showed no difference in relative risk (RR) of revision across CoC, CoPc, CoPxl and MoPxl bearings. However, the MoM bearing was demonstrated with a significant higher risk of revision compared with CoC (RR 5.10; 95% CI=1.62 to 16.81), CoPc (RR 4.80; 95% CI=1.29 to 17.09), or MoPxl (RR 3.85; 95% CI=1.16 to 14.29), and the MoPc bearing was indicated with a higher risk of revision compared with CoC (RR 2.83; 95% CI=1.20 to 6.63). The ranking probabilities of the effective interventions also revealed the inferiority of the MoM and MoPc implants in survivorship (both 0%, 95% CI=0% to 0%) compared with CoC (39%, 95% CI=0% to 100%), CoPc (33%, 95% CI=0% to 100%), CoPxl (7%, 95% CI=0% to 100%) or MoPxl (21%, 95% CI=0% to 100%).

CONCLUSIONS

The present evidence indicated the similar performance in survivorship among CoC, CoPc, CoPxl and MoPxl bearing implants, and that all likely have superiority compared with the MoM and MoPc bearing implants in THA procedures. Long-term RCT data are required to confirm these conclusions and better inform clinical decisions.

There Are No Differences in Short- to Mid-term Survivorship Among Total Hip-bearing Surface Options: A Network Meta-analysis

BACKGROUND

Total hip arthroplasty (THA) is increasingly being performed in patients with long life expectancies and active lifestyles. Newer implant bearing surfaces, with superior wear characteristics, often are used in this cohort with the goal of improving longevity of the prosthesis, but comparisons across the numerous available bearing surfaces are limited, so the surgeon and patient may have difficulty deciding which implants to use.

QUESTIONS/PURPOSES

The purpose of this study was to answer the following question: Is there a short- to mid-term survivorship difference between common THA bearings used in patients younger than age 65 years?

METHODS

We conducted a systematic review to identify randomized clinical trials (RCTs) published after 2000 that reported survivorship of ceramic-on-ceramic (CoC), ceramic-on-highly crosslinked polyethylene (CoPxl), or metal-on-highly crosslinked polyethylene (MoPxl) bearings. To qualify for our review, RCTs had to have a minimum 2-year followup and study patients were required to have an average age younger than 65 years. Direct-comparison meta-analysis and network meta-analysis were performed to combine direct and indirect evidence.

RESULTS

Direct-comparison meta-analysis found no differences among the bearing surfaces in terms of the risk of revision; this approach demonstrated a risk ratio for revision of 0.65 (95% confidence interval [CI], 0.19-2.23; p = 0.50) between CoC and CoPxl and a risk ratio for revision of 0.40 (95% CI, 0.06-2.63; p = 0.34) between CoC and MoPxl. Network meta-analysis (with post hoc modification) likewise found no differences in survivorship across the three implant types, demonstrating the following probabilities of most effective implant with 95% credible intervals (CrI): CoC = 64.6% (0%-100%); CoPxl = 24.9% (0%-100%); and MoPxl = 9.9% (0%-100%). The CrIs ranged from 0% to 100% for all three bearing surfaces. Direct-comparison meta-analysis allowed for pooling of five RCTs, including 779 THAs, whereas network meta-analysis (before post hoc analysis) enabled pooling of 18 RCTs, including 2599 THAs.

CONCLUSIONS

Current published evidence does not support survivorship differences among commonly used bearing surfaces in patients younger than age 65 years undergoing THA at short- to mid-term followup. Long-term RCT data will be needed to determine if a survivorship benefit is realized in younger, more active patients over time.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Ceramic-on-ceramic versus ceramic-on-polyethylene bearing surfaces in total hip arthroplasty

The choice between ceramic-on-ceramic (COC) and ceramic-on-polyethylene (COP) in primary total hip arthroplasty (THA) remains controversial. The purpose of this study was to evaluate the reliability and durability of COC vs COP bearing surfaces in THA. Based on published randomized, controlled trials (RCTs) identified in PubMed, Embase, and the Cochrane Central Register of Controlled Trials, the authors performed a meta-analysis comparing the clinical and radiographic outcomes of COC with those of COP. Two investigators independently selected the studies and extracted the data. The methodological quality of each RCT was assessed using the Physiotherapy Evidence Database (PEDro) scale. Relative risks and 95% confidence intervals from each trial were pooled using random-effects or fixed-effects models depending on the heterogeneity of the included studies. Nine RCTs involving 1575 patients (1747 hips) met the predetermined inclusion criteria. Eight of 9 included RCTs had high methodological quality. The heterogeneity was not significant, and all the results were pooled using a fixed-effects model. The results demonstrated that COC significantly increased the risks of squeaking and total implant fracture compared with COP. No significant differences with respect to revision, osteolysis and radiolucent lines, loosening, dislocation, and deep infection were observed between the COC and COP bearing surfaces. This meta-analysis resulted in no sufficient evidence to identify any clinical or radiographic advantage of COC vs COP bearing surfaces in the short- to mid-term follow-up period. Long-term follow-up is required for further evaluation.

Nine year follow-up of a ceramic-on-ceramic bearing total hip arthroplasty utilizing a layered monoblock acetabular component

INTRODUCTION

Early ceramic bearing systems in total hip arthoplasty (THA) sought to provide long term wear improvement over traditional metal on polyethylene systems. However, previous designs exhibited fractures of the ceramic acetabular liner, leading to the development of the Implex Hedrocel ceramic bearing THA system where the ceramic liner was supported on a layer of polyethylene intended to transition liner loads to the metal shell, a so-called "sandwich" design. Unfortunately, the device trial was stopped to further enrollment when liner fractures were reported. The current study examines nearly 10-year follow-up on 28 devices implanted by two surgeons at one institution in order to document ceramic bearing system performance over a longer time period.

METHODS

Radiographic and patient reported outcomes, in the form of Harris Hip Scores (HHS) and 12-Item Short Form Health Survey (sF-12), were collected.

RESULTS

During the study period two cups were replaced, one at three years and a second at seven years. At the five year follow-up HHS were similar to those reported in the literature for devices with traditional metal-on-polyethylene bearing surfaces and for other sandwich ceramic bearing designs. At the nine year follow-up, the HHS had not changed significantly and SF-12 scores measuring overall physical and mental health were higher than age matched national norms (p<0.001). There were no signs of cup migration, stem subsidence, osteolysis or cup loosening at any time up to the last follow-up in this patient cohort. The 89% survivorship rate and device revisions due to delamination of the liner observed in this group were similar to those reported earlier for this device and for other "sandwich design" ceramic bearing systems.

DISCUSSION

This cohort did not exhibit new failure modes and HHS and SF-12 scores indicated high functionality for the majority of patients. These data suggest that a focus on preventing ceramic liner fracture through design and/or materials improvements may result in a device with long-term functionality.