Survival of hard-on-hard bearings in total hip arthroplasty: a systematic review

Outcome and complication rate of total hip arthroplasty in patients younger than twenty years: which bearing surface should be used?

PURPOSE

Total hip arthroplasty (THA) in younger patients remains controversial due to concerns regarding long-term implant survival and potential complications. This study aimed to evaluate long-term clinical outcomes, complications, differences in complication and revision rates by bearing surfaces, and Kaplan-Meier survival curves for THA in patients under 20 years old.

METHODS

A retrospective review was conducted for 65 patients (78 hips) who underwent THA between 1991 and 2018. Their mean age was 18.9 years. Their clinical outcomes were assessed using the Harris Hip Score (HHS). Radiological outcomes were evaluated based on the presence of loosening, osteolysis, and heterotopic ossification. Complications such as dislocation, periprosthetic fractures, and infections were assessed. The mean follow-up period was 13.2 years (range, 5.0-31.2 years).

RESULTS

The mean HHS improved from 44.6 to 90.1. There were two cases of dislocation. However, no periprosthetic fracture, deep infection, or ceramic component fracture was noted. There were 19 revisions of implants. Eighteen of 19 hips were operated with hard-on-soft bearings in the index surgery (p < 0.01). The 23-year survivorship was 97.8% for THA using ceramic-on-ceramic bearings, while the 31-year survivorship was 36.7% using hard-on-soft bearings.

CONCLUSION

THA in patients under 20 years old yielded promising clinical and radiological outcomes, although polyethylene-bearing-related concerns persisted. Previously operated patients with hard-on-soft bearing should be meticulously examined during the follow-up. As ceramic-on-ceramic bearing showed excellent survivorship in this particular cohort, we recommend the use of this articulation as the bearing of choice.

Long-Term Outcomes of Cementing Highly Cross-Linked Polyethylene Liners Into Well-Fixed Acetabular Shells in Revision Total Hip Arthroplasty

BACKGROUND

Cementing a new liner into a secure, well-positioned metallic shell can be a less-invasive strategy in revision total hip arthroplasty (THA). This study aimed to report the mean 14-year outcomes of cementing highly cross-linked polyethylene (XLPE) liners into well-fixed acetabular shells in revision THAs.

METHODS

This study reviewed a single-surgeon series of cementing XLPE liners into well-fixed acetabular components. Of the 52 hips (51 patients) evaluated, 48 hips (47 patients) that satisfied a minimum follow-up of 10 years were included. The Harris Hip score was used for clinical evaluation. Final hip radiographs were used to determine the extent of acetabular osteolysis and stability of the components. The mean age at index operation was 53 years (range, 32 to 72). The mean follow-up duration was 14 years (range, 10 to 18).

RESULTS

The mean Harris Hip score improved from 58 points (range, 23-81) preoperatively to 91 points (range, 45-100) at the final evaluation (P < .001). A total of 3 acetabular rerevisions were performed, all for aseptic loosening of the outer shell. One postoperative dislocation occurred, but it was successfully treated with a closed reduction. Final radiographs showed a significant reduction in acetabular osteolysis (P < .001). Implant survivorship free from any rerevision was 93.3% (95% confidence interval, 85.9-100%) at 14 years.

CONCLUSION

Cementing an XLPE liner into a well-fixed acetabular shell in revision THA demonstrated excellent clinical and radiographic outcomes at a mean of 14 years postoperatively. This technique could be a safe and durable option in the absence of XLPE liners compatible with preimplanted shells.

Ceramic-on-metal coupling in THA: long term clinical and radiographic outcomes using two different short stems

BACKGROUND

Hip prosthetic replacement surgery is the gold standard for patients affected by symptomatic osteoarthritis. The ceramic-on-metal hybrid hard-on-hard bearing was initially launched on the market with the purpose of reducing adhesive and corrosion wear, loss of metal debris and ions and risk of fracture and squeaking. However, this bearing was withdrawn from the market, in the apprehension of local and systemic toxicity. The aim of this study is to evaluate the reliability and safety of ceramic-on-metal bearing at long term follow-up.

METHODS

From 2 cohorts of patients suffering of hip osteoarthritis who underwent total hip arthroplasty using ceramic-on-metal bearing with two different short stems, 19 of the GROUP A and 25 of the GROUP B were suitable for this study. All patients were compared clinically using the Harris Hip Score (HHS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), visual analogue scale (VAS), 12-item Short Form Health Survey (SF12P/M), and radiographically. Blood samples were collected in order to evaluate chromium and cobalt ions level. The two groups were compared in terms of metal ions blood levels, and finally all the implanted prostheses were compared with a healthy control group.

RESULTS

All the implanted stems were well-positioned and osseointegrated at a mean follow-up of 114 months. Improvements were observed for all clinical scores comparing preoperative and postoperative values in both groups. Radiographic evaluation showed a good ability to restore proper articular geometry. Chromium and cobalt ion analysis revealed values below the safety threshold except for 1 case in GROUP A (cup malposition) and 2 cases in GROUP B (6.1%). No revision occurred.

CONCLUSIONS

Ceramic-on-metal bearing is safe and reliable at long term follow-up in association to short stems arthroplasty, if the implant is correctly positioned. Chromium and cobalt metal ions blood levels evaluation should be performed annually.

Implant factors that might influence components' survival in primary total hip arthroplasty

Primary total hip arthroplasty (THA) is an invaluable surgical procedure that has revolutionised the treatment of various end-stage hip pathologies. Aseptic loosening of either acetabular cup and/or femoral stem as well as components' dislocation are well-known post-operative complications due to so many factors: environmental, surgeon, patient related, disease related or implant design. The aim of this literature review is to look at some relevant implant designs that might influence acetabular and femoral components' survival for primary cementless THA using revision for aseptic loosening and dislocation as criteria for failure. This may also assist the surgeon in making an informed choice of using appropriate implants to match the demographic and disease-specific need of the patients undergoing the surgical procedure. This review article was performed using an online literature search on relevant publications.

Long-Term Outcomes of a Titanium-Encased Ceramic Liner Total Hip Arthroplasty (15 to 21Year Results)

BACKGROUND

Historically, aseptic loosening and osteolysis were responsible for most of the revisions among young and more active patients. Ceramic-on-ceramic bearings reduced wear but presented mechanical issues such ceramic fracture or liner chipping during insertion. To prevent this from happening a titanium-encased alumina liner was developed. The aim of this study is to address long-term results of this specific ceramic design.

METHODS

All patients received an uncemented acetabular component with ceramic-on-ceramic bearing (94 hips in 77 patients). Patients were prospectively followed over 15 years. Clinical evaluation included the Harris Hip Score and Visual Analog Scale pain scale. Radiographic analysis included integration, osteolysis, and ceramic-related mechanical issues, such as malseating of the insert.

RESULTS

The studied acetabular design survivorship was 98.9% at a mean follow-up of 17.2 years. One arthroplasty was revised secondary to infection but no cup had loosened or migrated during the study. Only 1 cup showed complete radiolucent lines. There was no fracture of any ceramic component in the study group. Malseating was present in 12 acetabular components (12.8%). No osteolysis was observed with over 15 years of follow-up.

CONCLUSION

In conclusion, this acetabular component demonstrates a favorable clinical and radiological outcome with over 15 years of follow-up. Osteolysis was not observed and incomplete seating of the titanium-sleeved ceramic liner did not lead to mechanical problems.

Incidence, Risk Factors, and Outcome of Ceramic-On-Ceramic Bearing Breakage in Total Hip Arthroplasty

BACKGROUND

Ceramic-on-ceramic bearing breakage is a rare but significant complication of total hip arthroplasty. This study aimed to identify risk factors for breakage and to determine the outcome of different revision options.

METHODS

All ceramic-on-ceramic primary total hip arthroplasty procedures reported to the Australian Joint Replacement Registry from September 1999 to December 2019 were included. Procedures were subdivided into alumina or mixed ceramic (alumina/zirconia). All breakages were identified. The association between ceramic type and head size was assessed. Subsequent revision rates were compared and cause of revision assessed.

RESULTS

There were 23,534 alumina and 71,144 mixed ceramic procedures. Breakage was the reason for 1^st revision in 84 alumina (5.27% of all revisions and 0.36% of procedures) and 56 mixed ceramic procedures (2.46% of all revisions; 0.08% of procedures). Alumina had a higher breakage rate than mixed ceramic (HR 2.50 (95% CI 1.75, 3.59), P < .001), and breakage was higher for 36-38mm head sizes using alumina (HR 2.84 (1.52, 5.31), P = .001). 17.8% of 2^nd revisions occur by 3 years, due to dislocation, infection, metal-related pathology, and loosening. A neck adapter sleeve did not reduce 2^nd revisions. Numbers were too low to compare revision bearing surface options.

CONCLUSION

Ceramic breakage has reduced with mixed ceramics but has a 0.79/1000 incidence at 15-year follow-up. It is unclear what the risk factors are for modern ceramics with increasing head size a risk for alumina only. Risk of 2^nd revision is high and occurs early. The optimal revision option is unknown.

Catastrophic failure and metallosis of the acetabular component in total hip arthroplasty

Background

To evaluate the clinical features and results of the revision total hip arthroplasties (THA) in patients with catastrophic failures and metallosis.

Methods

Fifteen hips of 14 patients with catastrophic failure and metallosis in hip arthroplasties were evaluated. They were followed for at least 4.2 years after the revision THA. Clinical evaluation was performed using Harris hip score. Osteolysis, loosening or presence of metallosis was evaluated with standard radiographs. Metallosis was evaluated intraoperatively according to the metallosis severity classification.

Results

The mean time from failure until revision surgery was 9.4 years. It was observed that in the primary THA, metal-on-ceramic (MoC), ceramic-on-ceramic (CoC) and metal-on-conventional polyethylene (MoCPE) bearings were used in 1, 3 and 11 hips, respectively. Grade III metallosis was observed in all patients during revision surgeries. The mean Harris hip score increased from 55 points before revision THA to 75 points at the final follow-up. In revision arthroplasty, MoCPE and CoC bearings were used in 13 and 2 hips, respectively. The femoral stem was replaced in 5 hips. All acetabular cups, except that of one hip, were revised.

Conclusions

Revisions of THAs with catastrophic failures and metallosis are quite challenging. Routine follow-up of arthroplasty patients is beneficial to examine for osteolysis, loosening, and asymmetric wear.

Maximizing the Lubricant Film Thickness Between a Rigid Microtextured and a Smooth Deformable Surface in Relative Motion, Using a Soft Elasto-Hydrodynamic Lubrication Model

We design a pattern of microtexture features to increase hydrodynamic pressure and lubricant film thickness in a hard-on-soft bearing. We use a soft elastohydrodynamic lubrication model to evaluate the effect of microtexture design parameters and bearing operating conditions on the resulting lubricant film thickness and find that the maximum lubricant film thickness occurs with a texture density between 10% and 40% and texture aspect ratio between 1% and 14%, depending on the bearing load and operating conditions. We show that these results are similar to those of hydrodynamic textured bearing problems because the lubricant film thickness is almost independent of the stiffness of the bearing surfaces in full-film lubrication.

Is Oxidized Zirconium Femoral Head Superior to Other Bearing Types in Total Hip Arthroplasty? A Systematic Review and Meta-Analysis

BACKGROUND

Oxidized zirconium (OxZi) is a relatively new type of material that combines the strength of a metal with the surface/wears properties of a ceramic. Our aim was to investigate whether OxZi femoral heads lead to lower polyethylene wear, higher survival rate, and better clinical outcomes than the other bearing types in patients treated with total hip arthroplasty (THA).

METHODS

Two reviewers independently conducted a systematic search according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses using the MEDLINE/PubMed database and the Cochrane Database of Systematic Reviews. These databases were queried with the terms: a. "oxidized" AND "zirconium" AND "total" AND "hip" AND "arthroplasty"; b. "oxinium" AND "total" AND "hip" AND "arthroplasty". The primary outcome measures were the survival rate of the bearing surfaces as well as the polyethylene wear.

RESULTS

The vast majority (85.7%) of the studies, which reported the mean polyethylene wear rate, showed that there was not any significant difference between OxZi and cobalt-chrome (CoCr) femoral heads (rate ratio: 0.836; 95% confidence interval: 0.362-1.928; P = .674). All studies comparing the survival rate of OxZi and CoCr femoral heads illustrated almost excellent survivorship with both implants.

CONCLUSION

OxZi femoral heads did not lead to lower polyethylene wear rate or higher survival rate, when compared with CoCr femoral heads in patients treated with THA. On the basis of these results and taking into account the higher cost of these implants, we would not recommend the routine use of OxZi femoral heads in primary THAs.

LEVEL OF EVIDENCE

Systematic review and meta-analysis of therapeutic studies I-III.

Increased Serum Ion Levels After Ceramic-on-Metal Bearing Total Hip Arthroplasty: Influence of an Asian Lifestyle

BACKGROUND

Recent clinical studies have suggested that systemic metal ion levels are significantly elevated at midterm follow-up in patients with ceramic-on-metal (COM) bearing. However, it is not clear whether there is a correlation between patient-related factors including the lifestyle and elevated levels of serum metal ions following COM total hip arthroplasty (THA).

METHODS

Serum metal levels were measured in 201 patients (234 hips) including 121 COM patients (140 hips) and 80 non-COM patients (94 hips). The Harris Hip Score, University of California, Los Angeles activity scale score, and Western Ontario and McMaster Universities Osteoarthritis Index score were measured and radiographs were obtained for the analysis.

RESULTS

Significantly higher levels of cobalt (Co) and chromium (Cr) were detected in the serum of the COM THA group (Co: 1.86 ± 4.0 μg/L; Cr: 1.81 ± 2.87 μg/L) than those of the non-COM THA group (Co: 0.27 ± 0.14 μg/L; Cr: 0.19 ± 0.25 μg/L; P < .001). The serum metal levels of patients who achieved the squatting position and the kneeling position were significantly higher than those of patients who could not squat (Co: P = .033; Cr: P = .074) and kneel (Co: P = .049; Cr: P = .031). The metal ion levels of the COM THA group correlated with the total range of motion (Co: P = .0293; Cr: P = .0399).

CONCLUSION

Patients who underwent a 36-mm COM THA showed high serum metal levels although good clinical outcomes at the midterm follow-up. We found that COM THA patients who were capable of greater range of motion, squatting, and kneeling are at risk of metal ion-related problems.

Five-year follow-up of a prospective randomised trial comparing ceramic-on-metal and metal-on-metal bearing surfaces in total hip arthroplasty

AIMS

The primary aim of this independent prospective randomised trial was to compare serum metal ion levels for ceramic-on-metal (CoM) and metal-on-metal (MoM) bearing surfaces in total hip arthroplasty (THA). Our one-year results demonstrated elevation in metal ion levels above baseline with no significant difference between the CoM and MoM groups. This paper reviews the five-year data.

PATIENTS AND METHODS

The implants used in each patient differed only in respect to the type of femoral head (ceramic or metal). At five-year follow-up of the 83 enrolled patients, data from 67 (36 CoM, 31 MoM) was available for comparison.

RESULTS

The mean serum cobalt (Co) and chromium (Cr) ion levels remained above baseline in both groups (CoM: Co 1.16 μg/l (0.41 to 14.67), Cr 1.05 μg/l (0.16 to 12.58); MoM: Co 2.93 μg/l (0.35 to 30.29), Cr 1.85 μg/l (0.36 to 17.00)) but the increase was significantly less in the CoM cohort (Co difference p = 0.001, Cr difference p = 0.002). These medium-term results, coupled with lower revision rates from national joint registries, suggest that the performance of CoM THA may be superior to that of MoM.

CONCLUSION

While both bearing combinations have since been withdrawn these results provide useful information for planning clinical surveillance of CoM THAs and warrants continued monitoring. Cite this article: Bone Joint J 2017;99-B:1298-1303.

Surgical Approach May Influence Survival of Large-Diameter Head Metal-on-Metal Total Hip Arthroplasty: A 6- to 10-Year Follow-Up Study

Large-diameter head (LDH) metal-on-metal (MoM) total hip arthroplasty (THA) has lost popularity because of metal allergy or ALTRs (adverse local tissue reactions) in the past decade. Whether the surgical approach may influence the survival of LDH-MoM-THA has not been reported. From 2006 to 2009, we performed 96 LDH-MoM-THAs on 80 patients using an in situ head-neck assembly technique through a modified Watson-Jones approach. With a mean follow-up of 8.4 years (range, 6.3–10.1 years), the implant survival rate was 100%. All patients were satisfied with the results and the Harris Hip Score improved from 52 points to 98 points. No ALTRs were found, but 17.7% of the 96 hips (17 adverse events) experienced adverse events related to the cup, including 5 cases of outlier cup malposition, 11 cases of inadequate cup seating, and 1 acetabular fracture. The tissue tension that was improved by a muscle-sparing approach might lessen the chance of microseparation or edge-loading that is taken as the major risk for early implant failure. Further investigation of whether these LDH-MoM-THAs would fail or not would require a longer follow-up or even retrieval analysis in the future.

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.

Mid-term results of ReCap/Magnum/Taperloc metal-on-metal total hip arthroplasty with mean follow-up of 7.1 years

INTRODUCTION

Despite enthusiasm for metal-on-metal bearings, disappointing short- to mid-term outcomes has all but halted the use of this bearing articulation. This review presents mid-term results for the ReCap Magnum total hip replacement.

PATIENTS AND METHODS

This prospective study evaluated 79 ReCap/Magnum/Taperloc total hip replacements with mean follow-up of 7.1 (range 3.7-9.2) years. 43 were female and 36 male. Metal ions were measured and radiographic measurement included a 'margin of safety' angle to quantify risk of edge loading. When a clinical suspicion of adverse reaction to metal debris was present, patients had metal artefact reduction sequence MRI. Harris Hip Score and Oxford Hip Score evaluated functional outcome and SF-12 and EQ-5L-5D assessed quality of life at final follow-up.

RESULTS

7 hips were revised indicating 91.1% survivorship at 7.1 years. Postoperative Harris Hip Score and Oxford Hip Score significantly improved. Females and symptomatic patients predicted increased metal ions. Margin of safety correlated with postoperative Oxford Hip Score. Symptomatic hips and positive MRI showed reduced survivorship.

CONCLUSIONS

Compared to more traditional bearings like metal or ceramic on polyethylene the overall outcome of this ReCap/Magnum/Taperloc study cohort is modest. It is felt that further failures will occur in this group therefore cautious interpretation of the results is justified given the potential for reduced survival outcomes.

Corrosion and surface modification on biocompatible metals: A review

Corrosion prevention in biomaterials has become crucial particularly to overcome inflammation and allergic reactions caused by the biomaterials' implants towards the human body. When these metal implants contacted with fluidic environments such as bloodstream and tissue of the body, most of them became mutually highly antagonistic and subsequently promotes corrosion. Biocompatible implants are typically made up of metallic, ceramic, composite and polymers. The present paper specifically focuses on biocompatible metals which favorably used as implants such as 316L stainless steel, cobalt-chromium-molybdenum, pure titanium and titanium-based alloys. This article also takes a close look at the effect of corrosion towards the implant and human body and the mechanism to improve it. Due to this corrosion delinquent, several surface modification techniques have been used to improve the corrosion behavior of biocompatible metals such as deposition of the coating, development of passivation oxide layer and ion beam surface modification. Apart from that, surface texturing methods such as plasma spraying, chemical etching, blasting, electropolishing, and laser treatment which used to improve corrosion behavior are also discussed in detail. Introduction of surface modifications to biocompatible metals is considered as a "best solution" so far to enhanced corrosion resistance performance; besides achieving superior biocompatibility and promoting osseointegration of biocompatible metals and alloys.

Tribological characterization of zirconia coatings deposited on Ti6Al4V components for orthopedic applications

One of the most important issues leading to the failure of total joint arthroplasty is related to the wear of the plastic components, which are generally made of ultra high molecular weight polyethylene (UHMWPE). Therefore, the reduction of joint wear represents one of the main challenges the research in orthopedics is called to address nowadays. Surface treatments and coatings have been recognized as innovative methods to improve tribological properties, also in the orthopedic field. This work investigated the possibility to realize hard ceramic coatings on the metal component of a prosthesis, by means of Pulsed Plasma Deposition, in order to reduce friction and wear in the standard coupling against UHMWPE. Ti6Al4V substrates were coated with a 2 μm thick yttria-stabilized zirconia (YSZ) layer. The mechanical properties of the YSZ coatings were assessed by nanoindentation tests performed on flat Ti6Al4V substrates. Tribological performance was evaluated using a ball-on-disk tribometer in dry and lubricated (i.e. with fetal bovine serum) highly-stressing conditions, up to an overall distance of 10 km. Tribology was characterized in terms of coefficient of friction (CoF) and wear rate of the UHMWPE disk. After testing, specimens were analyzed through optical microscopy and SEM images, in order to check the wear degradation mechanisms. Progressive loading scratch tests were also performed in dry and wet conditions to determine the effects of the environment on the adhesion of the coating. Our results supported the beneficial effect of YSZ coating on metal components. In particular, the proposed solution significantly reduced UHMWPE wear rate and friction. At 10 km of sliding distance, a wear rate reduction of about 18% in dry configuration and of 4% in presence of serum, was obtained by the coated group compared to the uncoated group. As far as friction in dry condition is concerned, the coating allowed to maintain low CoF values until the end of the tests, with an overall difference of about 40% compared to the uncoated balls. In wet conditions, the friction values were found to be comparable between coated and uncoated materials, mainly due to a premature delamination of the coating. Scratch tests in wet showed in fact a reduction of the critical load required to a complete delamination due to a formation of blister, although no change or damage occurred at the coating during the soaking period. Although conditions of high values of contact pressure were considered, further analyses are however required to fully understand the behavior of YSZ coatings in wet environment and additional research on the deposition process will be mandatory in order to improve the coating tribological performance at long distances addressing orthopedic applications.

Halo and spillover effect illustrations for selected beneficial medical devices and drugs

BACKGROUND

Negative news media reports regarding potential health hazards of implanted medical devices and pharmaceuticals can lead to a 'negative halo effect,' a phenomenon whereby judgments about a product or product type can be unconsciously altered even though the scientific support is tenuous. To determine how a 'negative halo effect' may impact the rates of use and/or explantation of medical products, we analyzed the occurrence of such an effect on three implanted medical devices and one drug: 1) intrauterine contraceptive devices (IUDs); 2) silicone gel-filled breast implants (SGBI); 3) metal-on-metal hip implants (MoM); and 4) the drug Tysabri.

METHODS

Data on IUD use from 1965 to 2008 were gathered from the Department of Health and Human Services Vital and Health Statistics and peer-reviewed publications. Data regarding SGBI implant and explantation rates from 1989 to 2012 were obtained from the Institute of Medicine and the American Society of Plastic Surgeons. MoM implant and explantation data were extracted from the England and Wales National Joint Registry and peer-reviewed publications. Tysabri patient data were reported by Elan Corporation or Biogen Idec Inc. Data trends for all products were compared with historical recall or withdrawal events and discussed in the context of public perceptions following such events.

RESULTS

We found that common factors altered public risk perceptions and patterns of continued use. First, a negative halo effect may be driven by continuing patient anxiety despite positive clinical outcomes. Second, negative reports about one product can spill over to affect the use of dissimilar products in the same category. Third, a negative halo effect on an entire category of medical devices can be sustained regardless of the scientific findings pertaining to safety. Fourth, recovery of a product's safety reputation and prevalent use may take decades in the U.S., even while these products may exhibit widespread use and good safety records in other countries.

CONCLUSIONS

We conclude that the 'negative halo effect' associated with a stigma, rather than an objective risk-benefit assessment of medical products can increase negative health outcomes for patients due to reduced or inappropriate product usage.

National Trends in Primary Total Hip Arthroplasty in Extremely Young Patients: A Focus on Bearing Surface Usage From 2009 to 2012

BACKGROUND

The ideal bearing surface for primary total hip arthroplasty (THA) in young patients remains a debate. Data on recent national trends are lacking. The purpose of this study is to provide an analysis on the national epidemiologic trends of bearing surface usage in patients aged ≤30 years undergoing THA from 2009 through 2012.

METHODS

Using the Healthcare Cost and Utilization Project Nationwide Inpatient Sample from 2009 to 2012, 9265 THA discharges (4210 coded by bearing surface) were identified in patients aged ≤30 years. Prevalence of surface type was analyzed along with patient and hospital demographic data. Statistical analysis was performed using SAS (SAS version 9.1; SAS, Inc, Cary, NC). Significance was set at P < .05.

RESULTS

Ceramic-on-polyethylene (CoP) bearing surfaces were most commonly used, representing 35.6% of cases, followed by metal-on-polyethylene (MoP; 28.0%), metal-on-metal (MoM; 19.3%), and ceramic-on-ceramic (CoC; 17.0%) bearing surfaces. Hard-on-hard bearing surfaces (MoM and CoC) represented only 36.4% of cases, a significant decrease from previously reported findings (2006-2009) where hard-on-hard bearing surfaces were the majority (62.2%; P < .05). Hard-on-hard bearing surface usage decreased from 2009 to 2012 (MoM: 29.7% to 10.2%; CoC: 20.0% to 14.7%), whereas hard-on-soft bearing surface usage (MoP and CoP) increased. CoP bearing surfaces saw the most significant increase from 25.7% in 2009 to 48.2% in 2012. A cost analysis revealed that CoP discharges were associated with higher hospital charges than other surface types, with an average charge of $66,457 (P < .05).

CONCLUSION

Use of hard-on-hard surfaces has decreased significantly in this population, whereas CoP and MoP surfaces have become increasingly common. Determining the optimal bearing surface for extremely young patients continues to be a challenge for orthopedic surgeons as they weigh the risks and benefits of each.

Chemistry-driven structural alterations in short-term retrieved ceramic-on-metal hip implants: Evidence for in vivo incompatibility between ceramic and metal counterparts

Ceramic-on-metal (CoM) hip implants were reported to experience lower wear rates in vitro as compared to metal-on-metal (MoM) bearings, thus hinting metal-ion release at lower levels in vivo. In this article, we show a spectroscopic study of two short-term retrieval cases of zirconia-toughened alumina (ZTA) femoral heads belonging to CoM hip prostheses, which instead showed poor wear performances in vivo. Metal contamination and abnormally high fractions of tetragonal-to-monoclinic (t→m) polymorphic transformation of the zirconia phase could be found on both ZTA heads, which contrasted with the optimistic predictions of in vitro experiments. At the molecular scale, incorporation of metal ions into the ceramic lattices could be recognized as due to frictionally assisted phenomena occurring at the ceramic surface. Driven by abnormal friction, diffusion of metal ions induced lattice shrinkage in the zirconia phases, while residual stress fields became stored at the surface of the femoral head. Diffusional alterations destabilized the chemistry of the ceramic surface and resulted in an abnormal increase in t→m phase transformation in vivo. Frictionally driven metal transfer to the ceramic lattice thus hinders the in vivo performance of CoM prostheses. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1469-1480, 2017.

Squeaking and microcracks in a delta-delta ceramic coupling: pin-on-disc study

There is a rising concern about squeaking in ceramic-on-ceramic total hip arthroplasty (THA). In pin-on-disc testing of a delta-delta coupling, we reproduced squeaking and observed microcracks on worn surfaces. We used a pin-on-disc machine and made discs and pins by cutting delta ceramic to a diameter of 40 mm (D-D). Cross-linked polyethylene was used for a comparison disc (D-P). We performed the same test using another D-D coupling specimen to confirm reproducibility. Squeaking in the D-D specimen was reproduced in wet conditions, though it was not found in the D-P specimen. Fast Fourier transform analysis showed a peak frequency for squeaking of 2794 Hz. The noise occurred at about 6.6 km of sliding distance. Scanning electron microscopy revealed that the worn surface of the pin in D-D at 10.8 km of sliding distance had some microcracks. However, there was no obvious damage to the worn surface of the pin in D-P at the same sliding distance. We confirmed the reproducibility of these findings, obtaining similar results, including squeaking, from another D-D coupling specimen. Our findings show that squeaking may occur in THA using delta ceramic bearings even if implants are placed to avoid extra-articular impingement of the femoral neck. Although the clinical relevance of microcracks is unknown, they may affect long-term outcomes in THA using delta ceramic bearings.

Biphasic and boundary lubrication mechanisms in artificial hydrogel cartilage: A review

Various studies on the application of artificial hydrogel cartilage to cartilage substitutes and artificial joints have been conducted. It is expected in clinical application of artificial hydrogel cartilage that not only soft-elastohydrodynamic lubrication but biphasic, hydration, gel-film and boundary lubrication mechanisms will be effective to sustain extremely low friction and minimal wear in daily activities similar to healthy natural synovial joints with adaptive multimode lubrication. In this review article, the effectiveness of biphasic lubrication and boundary lubrication in hydrogels in thin film condition is focused in relation to the structures and properties of hydrogels. As examples, the tribological behaviors in three kinds of poly(vinyl alcohol) hydrogels with high water content are compared, and the importance of lubrication mechanism in biomimetic artificial hydrogel cartilage is discussed to extend the durability of cartilage substitute.

NANOMECHANICAL CHARACTERIZATION OF ZIRCONIA THIN FILMS DEPOSITED ON UHMWPE BY PULSED PLASMA DEPOSITION

Plastic deformation and wear of the ultra-high molecular weight polyethylene (UHMWPE) insert have been pointed out as major issues relating to the long-term stability of an orthopaedic implant. The deposition of protective hard, tough and well-adhered zirconia ( ZrO 2) thin films directly on the surface of the UHMWPE component via the Pulsed Plasma Deposition (PPD) technique has been already demonstrated to be a feasible way to approach this problem. In the current study, the tribo-mechanical properties of ZrO 2-coated UHMWPE with respect to pristine UHMWPE were investigated in detail. Specifically, strength to local plastic deformation, indentation work portioning and creep behavior were evaluated through nanoindentation and micro-scratch tests. Further, preliminary wear data (i.e., rate and volume) were obtained by tribology tests mating coated and pristine UHMWPE with an alumina ball under dry conditions. The results of the mechanical tests evidenced a strong reduction of plastic deformation under both normal and tangential local loads and a drop of the 80% of the creep phenomenon for coated UHMWPE compared to pristine UHMWPE. Despite tribological tests showed similar wear data for coated and pristine UHMWPE, a different wear mechanism was detected between the two groups. The reported results supported the possibility to pursue this novel approach of depositing ZrO 2 thin film to protect the UHWMPE insert and enhance the long-term stability of the orthopaedic implants.

Five-year comparison of wear using oxidised zirconium and cobalt–chrome femoral heads in total hip arthroplasty

Oxidised zirconium (OxZi) has been developed as an alternative bearing surface for femoral heads in total hip arthroplasty (THA). This study has investigated polyethylene wear, functional outcomes and complications, comparing OxZi and cobalt–chrome (CoCr) as part of a three-arm, multicentre randomised controlled trial. Patients undergoing THA from four institutions were prospectively randomised into three groups. Group A received a CoCr femoral head and highly cross-linked polyethylene (XLPE) liner; Group B received an OxZi femoral head and XLPE liner; Group C received an OxZi femoral head and ultra-high molecular weight polyethylene (UHMWPE) liner. At five years, 368 patients had no statistically significant differences in short-form-36 (p = 0.176 mental, p = 0.756 physical), Western Ontario and McMaster Universities Osteoarthritis Index (p = 0.847), pain scores (p = 0.458) or complications. The mean rate of linear wear was 0.028 mm/year (standard deviation (sd) 0.010) for Group A, 0.023 mm/year (sd 0.010) for Group B, and 0.09 mm/year (sd 0.045) for Group C. Penetration was significantly higher in the UHMWPE liner group compared with both XLPE liner groups (p < 0.001) but no significant difference was noted between CoCr and OxZi when articulating with XLPE (p = 0.153). In this, the largest randomised study of this bearing surface, it appears that using a XLPE acetabular liner is more important in reducing THA component wear than the choice of femoral head bearing, at mid-term follow-up. There is a non-significant trend towards lower wear, coupling OxZi rather than CoCr with XLPE but long-term analysis is required to see if this observation changes with time and becomes significant.

Cite this article: Bone Joint J 2015;97-B:883–9.

Severe Wear and Pseudotumor Formation Due to Taper Mismatch in a Total Hip Arthroplasty: A Case Report

CASE

We describe the case of a seventy-six-year-old woman who had undergone bilateral total hip arthroplasty with Zweymüller-Metasul prostheses in 1996. After a fall sixteen years after the index procedures, radiographs suggested a taper fracture of the left total hip arthroplasty. However, revision surgery showed pseudotumor formation, with no evidence of taper fracture. Analysis of the prosthesis showed massive wear of the male stem taper caused by a mismatch between the stem taper and the head taper.

CONCLUSION

This case vividly demonstrates how taper size mismatch can cause dramatic metal wear and increased release of metal ions, resulting in pseudotumor formation.

Tough and adhesive nanostructured calcium phosphate thin films deposited by the pulsed plasma deposition method

Calcium phosphate thin films were deposited at room temperature by the pulsed plasma deposition method. After annealing at 600 °C, film mechanical properties and adhesion to the titanium substrate strongly improved.

Ceramic-on-ceramic total hip arthroplasty in patients younger than 55 years

PURPOSE

To review the outcomes of 65 patients younger than 55 years who underwent uncemented total hip arthroplasty (THA) using third-generation ceramic-on-ceramic prostheses.

METHODS

Medical records of 30 men and 35 women (80 hips) aged 18 to 55 (mean, 39) years who underwent uncemented THA using third-generation ceramic-onceramic prostheses by a single surgeon were reviewed. 61 THAs used the Reflection cup with the Synergy stem (n=49), Spectron stem (n=7), or Anthology stem (n=5), and 19 THAs used the Trident cup with the Secur-Fit stem. Outcomes were assessed based on the UCLA Activity Score and Harris Hip Score, as well as radiolucency around the implants, malposition, and subsidence on radiographs. Patients were asked about their satisfaction with current activity level (yes/no), activity limitation (no limitation, musculoskeletal limitation, psychological impediments and lack of motivation, and pain or disability of the operative hip), and change in occupational activity level (same or similar, more active, and less active or disability).

RESULTS

The mean follow-up period was 54 (range, 24-110) months. Six patients were excluded from the analysis owing to prosthetic failure secondary to ceramic liner fracture after falling (n=2), acetabular component loosening (n=1), intolerable squeak (n=1), periprosthetic fracture (n=1), and instability (n=1). The mean UCLA Activity Score improved from 4.0 (range, 1-10) to 7.7 (range, 2-10) [p<0.001], and the mean Harris Hip Score improved from 52.8 (range, 25-69) to 91.0 (range, 38-100) [p<0.001]. No hip had evidence of subsidence, loosening, or osteolysis. 52 (80%) patients were satisfied with their activity level; 28 (43%) patients reported no activity limitation; and 57 (88%) patients kept the same or similar occupation.

CONCLUSION

Ceramic-on-ceramic THA achieved acceptable clinical and radiographic outcomes.

An estimation of the incidence of squeaking and revision surgery for squeaking in ceramic-on-ceramic total hip replacement: a meta-analysis and report from the Australian Orthopaedic Association National Joint Registry

Squeaking arising from a ceramic-on-ceramic (CoC) total hip replacement (THR) may cause patient concern and in some cases causes patients to seek revision surgery. We performed a meta-analysis to determine the incidence of squeaking and the incidence of revision surgery for squeaking. A total of 43 studies including 16,828 CoC THR that reported squeaking, or revision for squeaking, were entered into the analysis. The incidence of squeaking was 4.2% and the incidence of revision for squeaking was 0.2%. The incidence of squeaking in patients receiving the Accolade femoral stem was 8.3%, and the incidence of revision for squeaking in these patients was 1.3%.

Unusual prosthetic femoral head fracture in total hip arthroplasty: ceramic on polyethylene articulation

A 68-year-old man with a previous right total hip arthroplasty presented with acute pain in the right hip, and no associated trauma was reported. The previous hybrid arthroplasty consisted of a ceramic femoral head articulating on an ultra-high-molecular-weight polyethylene liner. The unusual diagnosis of fractured ceramic femoral head was made and an urgent revision arthroplasty was performed to remove the ceramic bearing as well as all implants that may have come into contact with the ceramic. This case report highlights the material properties of ceramics in total hip arthroplasties as well as the importance of regular follow-up in these patients.

Stability and trunnion wear potential in large-diameter metal-on-metal total hips: a finite element analysis

BACKGROUND

Large-diameter femoral heads for metal-on-metal THA hold theoretical advantages of joint stability and low bearing surface wear. However, recent reports have indicated an unacceptably high rate of wear-associated failure with large-diameter bearings, possibly due in part to increased wear at the trunnion interface. Thus, the deleterious consequences of using large heads may outweigh their theoretical advantages.

QUESTIONS/PURPOSES

We investigated (1) to what extent femoral head size influenced stability in THA for several dislocation-prone motions; and the biomechanics of wear at the trunnion interface by considering the relationship between (2) wear potential and head size and (3) wear potential and other factors, including cup orientation, type of hip motion, and assembly/impaction load.

METHODS

Computational simulations were executed using a previously validated nonlinear contact finite element model. Stability was determined at 36 cup orientations for five distinct dislocation challenges. Wear at the trunnion interface was calculated for three separate cup orientations subjected to gait, stooping, and sit-to-stand motions. Seven head diameters were investigated: 32 to 56 mm, in 4-mm increments.

RESULTS

Stability improved with increased diameter, although diminishing benefit was seen for sizes of greater than 40 mm. By contrast, contact stress and computed wear at the trunnion interface all increased unabatedly with increasing head size. Increased impaction forces resulted in only small decreases in trunnion wear generation.

CONCLUSIONS

These data suggest that the theoretical advantages of large-diameter femoral heads have a limit. Diameters of greater than 40 mm demonstrated only modest improvement in terms of joint stability yet incurred substantial increase in wear potential at the trunnion.

CLINICAL RELEVANCE

Our model has potential to help investigators and designers of hip implants to better understand the optimization of trunnion design for long-term durability.

Failure analysis of alumina on alumina total hip arthroplasty with a layered acetabular component: minimum ten-year follow-up study

This prospective study reports the outcome of total hip arthroplasty (THA) performed in a consecutive series of patients using an alumina ceramic on a ceramic-layered component (Alumina-Bearing-Surface system). The cohort consisted of 270 hips in 229 patients. The study evaluated the clinical and radiological results over a mean follow-up of 11.4 years. Revision THA was performed on 58 hips, including alumina alternative failure in 50 hips, loosening in 4 hips, recurrent dislocation in 2 hips, stem neck fracture in 1 hip and hematoma in 1 hip. The survival rate was 68% with revision for any reason as the end point. The risk factors of implant failure are the preoperative range of motion of the hip joint and postoperative dislocation.

Alternative bearings in total hip arthroplasty in the young patient

Total hip arthroplasty is an effective treatment option for advanced hip arthritis in elderly patients. Studies in young patients have traditionally shown less durable results. With current implants, surgical technique, and cementless fixation methods, the durability of total hip arthroplasty may now be related to the wear performance of the bearing surfaces. To improve implant longevity, there are several bearing surface choices currently available for this demanding group of patients. Alternatives must be evaluated in terms of the risks and benefits associated with each articulation, and all new technologies must be carefully monitored over the long term.

Wear performance of ceramic-on-metal hip bearings

Ceramic-on-metal (CoM) bearings are considered to be a promising alternative to polyethylene-based bearings or hard-on-hard bearings (Ceramic-on-Ceramic (CoC) and Metal-on-Metal (MoM)). Although, CoM shows lower wear rates than MoM, in-vitro wear testing of CoM shows widely varying results. This may be related to limitations of wear-measuring methods. Therefore, the aim of this study was to improve the gravimetric measurement technique and to test wear behaviour of CoM bearings compared to CoC bearings. Level walking according to ISO-14242 was simulated for four CoM and four CoC bearings. Prior to simulation, errors in measurement of gravimetric wear were detected and improvements in measurement technique incorporated. The results showed no differences in mean wear rates between CoM and CoC bearings. However, the CoM bearings showed wear results over a wide range of wear performance. High reliability of wear results was recorded for the CoC bearings. Material transfer was observed on the ceramic heads of the CoM bearings. Therefore, for level walking a partial mixed or boundary lubrication has to be assumed for this type of bearing. CoM is a highly sensitive wear-couple. The reasons for the observed behaviour cannot be clarified from this study. Simulator studies have to be considered as an ideal loading condition. Therefore, high variations in wear rates as seen in this study, even at low levels, may have an adverse effect on the in-vivo wear behavior. Careful clinical use may be advisable until the reasons for the variation are fully clarified and understood.

Clinical failure analysis of contemporary ceramic-on-ceramic total hip replacements

The present study investigates the performance of ceramic-on-ceramic total hip replacements by combining a retrieval analysis with a survivorship analysis to elucidate mechanisms that led to clinical failure. Semiquantitative surface damage assessment, contact profilometry, contour measurements, and scanning electron microscopy were performed to characterize the types and quantify the extent of surface damage on the retrieved ceramic components. The implantation period was positively correlated with both damage scores of the femoral heads (R = 0.573, p < 0.001) and the acetabular cups (R = 0.592, p < 0.001). Increased maximal out-of-roundness values of the femoral heads correlated with both increased metal transfer damage score (R = 0.384, p = 0.023) and increased stripe damage score (R = 0.729, p ≤ 0.001) of the acetabular liners. The damage rate (damage score/year) for both the retrieved heads and acetabular liners was at least 2.2-fold greater at inclination angles of >45° than the damage rate at inclination angles of ≤45°. For the retrieved femoral heads only, the linear wear rate of 25.5 ± 21.3 µm/year at inclination angles of >45° was 6-fold greater than the linear wear rate of 4.2 ± 2.3 µm/year at inclination angles of ≤45°. Metal transfer on the ceramic bearing surface could possibly contribute to fluid-film starvation and, in combination with an increased inclination angle, may facilitate an adhesive wear mechanism associated with stripe surface damage. At our institution, the clinical survivorship of ceramic-on-ceramic total hip replacements was 98.9% (a total of 9 out of 815 patients were revised within 10 years after total hip arthroplasty) with revision as the end point, suggesting their safe use in younger patients.

A randomized trial of ceramic-on-ceramic bearing versus ceramic-on-crossfire-polyethylene bearing in total hip arthroplasty: five-year outcomes

This study determined how ceramic-on-ceramic bearing THA affected joint-specific pain, function and stiffness in the first five postoperative years compared with ceramic-on-highly-crosslinked-polyethylene bearing THA. Subjects less than 61 years of age were randomized to ceramic-on-ceramic (CERAMIC) [n = 48] or ceramic-on-highly-crosslinked-polyethylene (POLYETHYLENE) [n = 44] bearing THA. Subjects were assessed using the Western Ontario McMaster Osteoarthritis Index (WOMAC) and the RAND 12-Item Health Survey (RAND-12) preoperatively, and at one and five years postoperatively. 92 subjects(50 (54%) males; average age = 52 (SD 6.6) years) were enrolled. 78 (85%) subjects returned five years postoperatively. All subjects reported improvements at one and five years in all measured indices with no group differences detected. Seven (8%) subjects experienced postoperative THA complications, none related to bearing surfaces; two subjects (POLYETHYLENE) required revision for instability. Both bearing surfaces provided excellent short-term results in younger subjects.

Catastrophic failure of ceramic-on-ceramic total hip arthroplasty presenting as squeaking hip

A 68-year-old woman with osteoarthritis had a ceramic-on-ceramic left total hip arthroplasty, including ceramic femoral head and acetabular liner. At 5 years after surgery, the patient developed onset of a very loud squeaking noise, which could be heard 25 m from her, associated with limited hip movement. Findings at revision surgery included a broken ceramic femoral head component, complete wear of the ceramic acetabular component, and black wear debris. Squeaking hip after ceramic-on-ceramic total hip arthroplasty may be associated with catastrophic failure of the arthroplasty components.

Metal-on-metal vs conventional total hip arthroplasty: a systematic review and meta-analysis of randomized controlled trials

Metal-on-metal (MOM) hip articulations represent a potential alternative to conventional metal-on-polyethylene total hip arthroplasty (THA). We performed a systematic review of the peer-reviewed literature in search of studies comparing MOM with conventional primary THA with regard to functional outcomes, radiographic outcomes, and complication rates. Four Level I randomized controlled trials remained following our screening process. The data published in these studies were extracted and aggregated using a Mantel-Haenszel cumulative fixed effects meta-analysis. We found no significant difference between MOM and conventional THA with regard to functional outcomes as measured by Harris hip scores and radiographic outcomes as measured by radiolucent lines. Patients with MOM THA did however demonstrate a 3.37 times greater complication rate (1.57, 7.26). In light of the lack of superiority, the increased complication rate, the greater cost, and the potential for adverse medical consequences associated with MOM THA, these bearing surfaces should be used with caution.

Bursa over K nail presenting as pseudo tumor in gluteal region

We present a case of enlarged bursa with calcified/ossified walls presenting as pseudo tumor in the left gluteal region over an indwelling protruded tip of a K nail implanted 18 years back in a 35 years old male. The patient had received initial treatment from a quack and subsequently from a qualified physician before coming to us and was referred to us with a provisional diagnosis of some soft tissue tumor. Removal of the nail and the bursa resulted in complete recovery and full function.

Alumina-on-alumina THA performed in patients younger than 30 years: a 10-year minimum followup study

BACKGROUND

THA in patients younger than 30 years presents challenges because of uncertainties regarding the long-term survivorship of prostheses. Alumina-on-alumina bearings, which exhibit little long-term wear, may be a reasonable option but the long-term survivorship is unknown.

QUESTIONS/PURPOSES

We determined (1) the survival rate of alumina-on-alumina bearings in patients younger than 30 years after a 10-year followup, (2) the incidence of audible hip clicking and squeaking, (3) radiographic evidence of osteolysis, and (4) the effects on pregnancy, childbirth, and career choice.

METHODS

We retrospectively reviewed 62 patients who had 75 THAs with alumina-on-alumina bearings followed more than 10 years (average, 11.5; range, 10-13.5 years). Mean patient age at the time of surgery was 24 years (range, 18-30 years). All operations were performed using the same cementless implant at a single center. We determined survival, presence of osteolysis, and function (Harris hip score, WOMAC).

RESULTS

The 10-year survival rate of alumina-on-alumina bearings in THAs, with revision for any reason as the end point, was 98.9%. Audible hip clicking and squeaking were identified in 10 hips and two hips, respectively. No osteolysis was detected. None of the 11 patients who became pregnant had been affected by their THA during pregnancy or childbirth. Seven of the 14 patients who were unemployed at the time of index surgery stated that their THA affected their job choice.

CONCLUSIONS

We found a high 10-year survival of cementless alumina-on-alumina bearings in THAs in patients younger than 30 years. Lifetime events such as job choice, pregnancy, and childbirth should be considered when choosing THA for patients younger than 30 years.

LEVEL OF EVIDENCE

Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Pulsed plasma deposition of zirconia thin films on UHMWPE: proof of concept of a novel approach for joint prosthetic implants

Wear of ultra-high molecular weight polyethylene (UHMWPE) has been recognized as the main cause for long-term revision in joint arthroplasty. A new approach to overcome this detrimental issue is here presented: zirconia (ZrO₂) thin films were directly deposited onto the surface of UHMWPE by Pulsed Plasma Deposition (PPD) technique. The obtained films were structurally, morphologically and mechanically characterized by X-ray diffraction, scanning electron microscopy and nanoindentation tests, respectively. The critical fracture load was estimated by the analysis of the indenter footprints, while the adhesion degree was evaluated by a cross-cut tape test. Zirconia films exhibited a fully cubic structure, with densely packed grains, whereas mechanical tests showed that hard, tough and well-adherent films were deposited. These preliminary results suggested the feasibility of pursuing this alternative route to improve UHMPWE performances while preserving its well-established mechanical properties.

Revision total hip arthroplasty in younger patients: indications, reasons for failure, and survivorship

Increasing numbers of total hip arthroplasty (THA) procedures are being performed on younger patients, and the incidence of revision THA in this population is also increasing. The goals of our retrospective study were to survey the surgical indications and reasons for failure and survivorship of revision THA in patients aged < 50 years. We identified 139 cases of revision THA performed over a 6-year period in patients aged < 50 years. The most common reason for revision was aseptic loosening, followed by acetabular liner wear with or without osteolysis. We found an overall 10-year survivorship of 76%. When survivorship was stratified by the indication for revision surgery, revision for wear demonstrated the best 10-year survivorship, while revision for instability or infection exhibited poor survivorship.