Total Hip Arthroplasty Bearing Surface Trends in the United States From 2007 to 2014: The Rise of Ceramic on Polyethylene

Total Hip Arthroplasty: An Update on Navigation, Robotics, and Contemporary Advancements

While total hip arthroplasty (THA) remains effective for improvement of pain and function in patients with osteoarthritis and avascular necrosis, there remain areas of continued pursuit of excellence, including decreasing rates of dislocation, leg length discrepancy, implant loosening, and infection. This review article covers several bearing surfaces and articulations, computer-assisted navigation and robotic technology, and minimally invasive surgical approaches that have sought to improve such outcomes. Perhaps the most significant improvement to THA implant longevity has been the broad adoption of highly cross-linked polyethylene, with low wear rates. Similarly, navigation and robotic technology has proven to more reproducibly achieve intraoperative component positioning, which has demonstrated clinical benefit with decreased risk of dislocation in a number of studies. Given the projected increase in THA over the coming decades, continued investigation of effective incorporation of technology, soft tissue-sparing approaches, and durable implants is imperative to continued pursuit of improved outcomes in THA.

Ceramic Femoral Heads Exhibit Lower Wear Rates Compared to Cobalt Chrome: A Meta-Analysis

BACKGROUND

Wear between the femoral head and acetabular liners continues to limit the longevity of total hip arthroplasty implants despite advances in implant materials. The purpose of this meta-analysis was to compare linear wear rates of cobalt-chromium (CoCr) and fourth-generation ceramic femoral heads on highly cross-linked polyethylene (XLPE) liners.

METHODS

A systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was conducted to identify all studies between 2003 and 2020 that examined in vivo wear rates of either fourth-generation ceramics or CoCr femoral heads on XLPE liners. Studies were analyzed in a weighted means analysis of wear rates and a random effects meta-analysis.

RESULTS

A total of 36 studies met inclusion criteria (1,657 CoCr and 659 ceramic patients). The pooled, weighted mean wear rate was 0.063 mm/year (standard deviation [SD]: 0.061, confidence interval [CI]: 0.049-0.077) for CoCr and 0.047 mm/year (SD: 0.057, CI: 0.033-0.062; P < .01) for ceramic (P < .01). A meta-analysis of 4 studies directly comparing ceramic and CoCr found that CoCr heads demonstrated 0.029 mm/year more wear than ceramic heads (95% CI: 0.026-0.059, P = .306). Mean wear for 32-mm heads was significantly higher for ceramic (P < .01), while mean wear for 36-mm heads was significantly higher for CoCr (P < .01).

CONCLUSION

Fourth-generation ceramic femoral heads were found to have significantly lower wear rates than CoCr heads. Unlike previous studies, this meta-analysis included only in vivo studies and those with the same generation of highly XLPE liners.

Comparison of Premium Technology Utilization in Total Hip Arthroplasty Between Safety-net Hospitals and Non-safety-net Hospitals

INTRODUCTION

The objective of our study was to investigate the association of safety-net hospital (SNH) status with the use of premium technologies in total hip arthroplasty (THA) using the American Academy of Orthopaedic Surgeons American Joint Replacement Registry.

METHODS

Premium technology was defined as having one or more of the following three characteristics: ceramic femoral head, dual mobility (DM) bearing, or surgery conducted with robotic assistance (RA). Patients of all ages were included and subdivided into ceramic femoral head, DM, and RA cohorts. SNH status (based on disproportionate share data), patient demographics, geographical region, hospital size, and teaching affiliation were assessed. Multivariate regression analysis was conducted to analyze any notable associations.

RESULTS

A total of 624,933 THAs between SNHs and non-SNHs were available for analysis. Based on the three different premium technology categories, there were 551,838 THAs for ceramic femoral head utilization analysis, 601,223 THAs for DM utilization analysis, and 199,250 THAs for RA utilization analysis. SNHs were associated with less use of DM and RA (odds ratio [OR] 0.53 P < 0.0001, 0.39 P < 0.0001, respectively). No difference was observed in ceramic femoral head utilization between SNHs and non-SNHs. Patient age was significantly associated with less utilization of all three premium THA technologies (ceramic: OR 0.43 P < 0.0001; DM: OR 0.93 P < 0.0001, RA: OR 0.89 P < 0.001). Teaching hospitals were significantly associated with increased utilization of premium THA technologies (ceramic: OR 1.23 P < 0.0001, DM: OR 1.62 P < 0.0001, RA: OR 5.33 P < 0.001).

CONCLUSION

Premium THA technologies are becoming increasingly used across the US healthcare system; however, that growth is not equal in hospitals with marginalized patient populations. The utilization of ceramic femoral heads is becoming increasingly common across healthcare systems suggesting that ceramic femoral heads may no longer be considered premium technology but rather standard THA care.

LEVEL OF EVIDENCE

Level III.

Clinical Outcomes, Metal Ion Levels, Lymphocyte Profiles, and Implant Survival Following Five Different Bearings of Total Hip Arthroplasty: A Mean 10-year Follow-up Study

BACKGROUND

Different bearings have been used in total hip arthroplasty (THA), but the long-term performance is still controversial. The purpose of this study was to investigate whether there are differences when comparing THAs with 5 different bearings at a long-term follow-up of more than 10 years.

METHODS

From January 2010 to May 2012, 101 THA patients (134 hips) were divided into metal-on-metal group (MoM, 31 hips), metal-on-polyethylene group (MoP, 23 hips), ceramic-on-metal group (CoM, 21 hips), ceramic-on-ceramic group (CoC, 33 hips), and ceramic-on-polyethylene group (CoP, 26 hips). The mean follow-up period was 10.3 years. The Harris hip score (HSS), Western Ontario and McMaster Universities Osteoarthritis Index scores (WOMAC), range of motion (ROM), blood cell count, and liver-kidney function were measured. Serum and urine metal ion levels were measured using high-resolution inductively coupled plasma-mass spectrometry (ICP-MS) and a blood lymphocytes analysis was counted by flow cytometry.

RESULTS

No difference was observed in the HSS, WOMAC, ROM, blood cell count, or liver-kidney function among any of the 5 groups. Metal ion levels were significantly elevated in metal-containing bearings. Flow cytometry showed that no differences were found. Revision was performed due to pseudotumor in 3 patients. The implant survival rate was 96.7% and 93.3% for the MoM and CoC groups, which was significantly lower compared with other groups.

CONCLUSIONS

Metal ion levels were elevated significantly in metal-containing bearings, especially in MoM THA patients. The implant survival rate was significantly lower in CoC and MoM THAs, which was mainly due to pseudotumor formation.

LEVEL OF EVIDENCE

Therapeutic Level II.

Ceramic-on-polyethylene hip arthroplasty reduces the risk of postoperative periprosthetic joint infection

Metal-on-polyethylene (MoP) total hip arthroplasty (THA) prostheses are known to release metal debris. Basic science studies suggest that metal implants induce a pro-inflammatory response that ultimately chemoattracts leukocytes including macrophages and neutrophils to the surgical site. This raises concern of higher risk of infection with these prostheses through the "trojan horse" mechanism by which neutrophils and macrophages transport intracellular pathogens from a remote site. This study compared the infection occurrence between MoP and ceramic-on-polyethylene (CoP) implants to determine if a higher infection rate in MoP is present. We reviewed a consecutive series of 6052 CoP and 4550 MoP primary THA patients from 2015 to 2019. The occurrence of periprosthetic joint infection at 2 years was defined according to the 2018 ICM definition. Statistical analysis consisted of descriptive statistics, univariate analysis, and regression modeling. When compared to CoP, MoP patients were older, included more females, had a higher body mass index, and more commonly affected by comorbidities according to Elixhauser's score. Total revisions were higher in the MoP group (3.19% vs. 2.41%) The absolute incidence of PJI was higher in MoP (2.40% vs. 1.64%). When we adjusted for confounding factors, MoP was found independently associated with a higher PJI risk. Despite MoP and CoP both being widely used for primary THA, we found a higher incidence of PJI in MoP patients. The association remained significant when controlled for possible confounders. We hypothesize that leukocyte recruitment to these implants may play a role and should be further investigated.

Lower Rates of Ceramic Femoral Head Use in Non-White Patients in the United States, a National Registry Study

BACKGROUND

The purpose of our study was to investigate the association of race and ethnicity with the use of the newest technology and postoperative outcomes in total hip arthroplasty (THA) using the American Academy of Orthopaedic Surgeons (AAOS) American Joint Replacement Registry (AJRR).

METHODS

Adult THA procedures were queried from the AJRR from 2012 to 2020. A mixed-effects multivariate regression model was used to evaluate the association of race and ethnicity with the use of the newest technology (ceramic femoral head, dual-mobility implant, and robotic assist) at 30-day, and 90-day readmission. A proportional subdistribution hazard model was used to model a risk of revision THA.

RESULTS

There were 85,188 THAs with complete data for an analysis of outcomes and 103,218 for an analysis of ceramic head usage. The median length of follow-up was 37.9 months (interquartile range [IQR] 21.6 to 56.3 months). In multivariate models, compared to White non-Hispanic patients, Black (odds ratio [OR] 0.79, 95% confidence interval [CI] 0.69-0.92, P < .001), Hispanic (OR 0.76, CI 0.59-0.99, P = .037), Asian (OR 0.74, CI 0.55-1.00, P = .045), and Native American (OR 0.52, CI 0.30-0.87, P = .004) patients all had significantly lower rates of ceramic head use in THA. Compared to White non-Hispanic patients, Asian (hazard ratio [HR] 0.39, CI 0.18-0.86, P = .008) and Hispanic (HR 0.43, CI 0.19-0.98, P = .043) patients had significantly lower rates of revision. No differences in 30-day or 90-day readmission rates were seen.

CONCLUSION

Black, Hispanic, Native American, and Asian patients had lower rates of ceramic head use in THA when compared to White patients. These differences did not translate into worse clinical outcomes on a short-term follow-up. In fact, Asian patients had lower revision rates compared to non-Hispanic White patients. Additional study is necessary to evaluate the long-term consequence of lower ceramic head use in non-White patients in the United States.

Effect of femoral head material on head-to-trunnion impaction motion and taper

The purpose of this study was to evaluate the effect of femoral head material on the impaction force, relative motion, and stability of the trunnion. There were three groups with different head materials (n = 5 per group)-CoCr Group: 36 mm CoCr heads, Ceramic Group: 36 mm ceramic heads, Ceramic + Sleeve Group: 36 mm ceramic heads with a titanium sleeve-that were all impacted twice and disengaged onto titanium alloy (Ti6al4V) trunnions in in vitro conditions. A high-speed camera system was utilized to characterize relative displacement behavior of the head-trunnion junction motion. The first impact force of Ceramic + Sleeve Group (14,241    SD, 935) was significantly lower than the first impact force in Ceramic Group (14,961 N, SD = 184). Ceramic + Sleeve Group had a lower magnitude bounce-back displacement following the first impact (17.7 μm, SD = 11), p < 0.05) compared to CoCr Group (298.8 μm, SD = 84) and Group 2 (196.5 μm, SD = 31). Ceramic + Sleeve Group sat further on the trunnion (cumulative final displacement, 366.8 μm, SD = 71, p < 0.001) compared to CoCr Group (142.5 μm, SD = 41.8) and Ceramic Group (183.8 μm, SD = 30). Ceramic + Sleeve Group demonstrated two distinct disengagement patterns-(a) the sleeve disengaged from the trunnion (pull-off force 6810 N), and (b) the femoral head disengaged from the sleeve (pull-off force 18,620 N), with large fluctuations in pull-off force. The presence of a titanium sleeve with a ceramic head resulted in significant differences in impaction force on the trunnion, motion and displacement, and unique mechanisms for disengagement. Further investigation is required to determine potential clinical impact.

The Wear Rate and Survivorship in Total Hip Arthroplasty Using a Third-generation Ceramic Head on a Conventional Polyethylene Liner: A Minimum of 15-year Follow-up

Purpose

Materials and Methods

Results

Conclusion

Survivorship of Ceramic-on-Ceramic Total Hip Arthroplasty With Metal-Backed Acetabular Liners at 10 Years

BACKGROUND

Ceramic-on-ceramic bearings are becoming increasingly popular in primary total hip arthroplasty (THA). To enhance ceramic-on-ceramic liner exchange in case of revision surgery, metal-backed liner systems have been proposed. Little is known about the clinical performance of these implants. The purpose of this study is to evaluate a metal-backed liner implant system for primary THA.

METHODS

A total of 422 patients (with 468 consecutive THAs) were followed over a mean period of 10 years. All arthroplasties were performed with a cementless stem, a press-fit cup, and a metal-backed liner system. Surgical and clinical data, complications, and revisions were analyzed. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) before surgery and at 1 and 10 years after surgery were compared.

RESULTS

The overall 10-year implant survival rate was 93.8%. The survival rate was 97.0% for heads and liners, 97.5% for stem, and 99.3% for acetabular cup. The most common reason for revision was ceramic breakage (2.4%) of the third-generation (BIOLOX forte) acetabular liner. Mean WOMAC score improved significantly from 50.1 before surgery to 13.2 at 1 year after surgery. There was no difference in WOMAC scores between surgical approach and type of bearing at 1 and 10 years after surgery.

CONCLUSION

THA using cementless stem, press-fit cup, and metal-backed liner system provides satisfactory long-term outcomes, with revision rate comparable to that with other systems available in the market. The metal-backed liner system has low risk of mal-seating. Third-generation ceramic liners should be avoided as they seem to be more prone to breakage.

Assessing Taper Geometry, Head Size, Head Material, and Their Interactions in Taper Fretting Corrosion of Retrieved Total Hip Arthroplasty Implants

BACKGROUND

Decreased fretting and corrosion damage at the taper interface of retrieved ceramic-on-polyethylene total hip arthroplasty (THA) implants has been consistently reported; however, resultant fretting corrosion as a function of femoral head size and taper geometry has not been definitively explained.

METHODS

Eight cohorts were defined from 157 retrieved THA implants based on femoral head composition (n = 95, zirconia-toughened alumina, ZTA vs n = 62, cobalt-chromium alloy, CoCr), head size (n = 56, 32mm vs n = 101, 36mm), and taper geometry (n = 84, 12/14 vs n = 73, V40). THA implants were evaluated and graded for taper fretting and corrosion. Data were statistically analyzed, including via a 2³ factorial modeling.

RESULTS

Factorial-based analysis indicated the significant factors related to both resultant (summed) fretting and corrosion damage were head material and taper geometry; head material-taper geometry interaction was also a significant factor in resultant corrosion damage. Lower rates of moderate-to-severe fretting and corrosion damage were exhibited on ZTA heads (ZTA = 13%, CoCr = 38%), smaller heads (32mm = 18%, 36mm = 26%), and 12/14 tapers (12/14 = 13%, V40 = 35%). ZTA+32mm heads demonstrated the lowest rates of moderate-to-severe fretting and corrosion damage (12/14 = 2%, V40 = 7%), whereas CoCr heads with V40 tapers demonstrated the greatest rates of moderate-to-severe damage (32mm = 47%, 36mm = 59%).

CONCLUSION

In this series, retrieved implants with ZTA, 32-mm heads paired with 12/14 tapers exhibited lower rates of moderate-to-severe damage. Factorial analysis showed head material, taper geometry, and their interactions were the most significant factors associated with resultant damage grades. Isolating implant features may provide additional information regarding factors leading to fretting and corrosion damage in THA.

LEVEL OF EVIDENCE

IV (case series).

The contribution of the histopathological examination to the diagnosis of adverse local tissue reactions in arthroplasty

The histopathological examination of the periprosthetic soft tissue and bone has contributed to the identification and description of the morphological features of adverse local tissue reactions (ALTR)/adverse reactions to metallic debris (ARMD). The need of a uniform vocabulary for all disciplines involved in the diagnosis and management of ALTR/ARMD and of clarification of the parameters used in the semi-quantitative scoring systems for their classification has been considered a pre-requisite for a meaningful interdisciplinary evaluation.

This review of key terms used for ALTR/ARMD has resulted in the following outcomes: (a) pseudotumor is a descriptive term for ALTR/ARMD, classifiable in two main types according to its cellular composition defining its clinical course; (b) the substitution of the term metallosis with presence of metallic wear debris, since it cannot be used as a category of implant failure or histological diagnosis; (c) the term aseptic lymphocytic-dominated vasculitis- associated lesion (ALVAL) should be replaced due to the absence of a vasculitis with ALLTR/ALRMD for lymphocytic-predominant and AMLTR/AMRMD for macrophage-predominant reaction.

This review of the histopathological classifications of ALTR/ARMD has resulted in the following outcomes: (a) distinction between cell death and tissue necrosis; (b) the association of corrosion metallic debris with adverse local lymphocytic reaction and tissue necrosis; (c) the importance of cell and particle debris for the viscosity and density of the lubricating synovial fluid; (d) a consensus classification of lymphocytic infiltrate in soft tissue and bone marrow; (e) evaluation of the macrophage infiltrate in soft tissues and bone marrow; (f) classification of macrophage induced osteolysis/aseptic loosening as a delayed type of ALTR/ARMD; (g) macrophage motility and migration as possible driving factor for osteolysis; (h) usefulness of the histopathological examination for the natural history of the adverse reactions, radiological correlation, post-marketing surveillance, and implant registries.

The review of key terms used for the description and histopathological classification of ALTR/ARMD has resulted in a comprehensive, new standard for all disciplines involved in their diagnosis, clinical management, and long-term clinical follow-up.

Cite this article: EFORT Open Rev 2021;6:399-419. DOI: 10.1302/2058-5241.6.210013

Surface Texturing of Prosthetic Hip Implant Bearing Surfaces: A Review

More than 300,000 total hip replacement surgeries are performed in the United States each year to treat degenerative joint diseases that cause pain and disability. The statistical survivorship of these implants declines significantly after 15-25 years of use because wear debris causes inflammation, osteolysis, and mechanical instability of the implant. This limited longevity has unacceptable consequences, such as revision surgery to replace a worn implant, or surgery postponement, which leaves the patient in pain. Innovations such as highly cross-linked polyethylene and new materials and coatings for the femoral head have reduced wear significantly, but longevity remains an imminent problem. Another method to reduce wear is to add a patterned microtexture composed of micro-sized texture features to the smooth bearing surfaces. We critically review the literature on textured orthopedic biomaterial surfaces in the context of prosthetic hip implants. We discuss the different functions of texture features by highlighting experimental and simulated results documented by research groups active in this area. We also discuss and compare different manufacturing techniques to create texture features on orthopedic biomaterial surfaces and emphasize the key difficulties that must be overcome to produce textured prosthetic hip implants.

The Effect of Texture Floor Profile on the Lubricant Film Thickness in a Textured Hard-On-Soft Bearing With Relevance to Prosthetic Hip Implants

Polyethylene wear debris limits the longevity of prosthetic hip implants. We design a pattern of axisymmetric texture features to increase hydrodynamic pressure and lubricant film thickness and, thus, reduce solid-on-solid contact, friction, and wear in hard-on-soft prosthetic hip implant bearings. Specifically, we study the effect of the texture floor profile on the lubricant film thickness using a soft elastohydrodynamic lubrication model. We compute the optimum texture parameters that maximize the lubricant film thickness for different texture floor profiles, as a function of bearing operating conditions. Flat texture floor profiles create thicker lubricant films than sloped or curved texture floor profiles for their respective optimum texture design parameters. We find that the texture feature volume is the most important parameter in terms of maximizing the lubricant film thickness, because a linear relationship exists between the texture feature volume with optimum texture parameters and the corresponding optimum lubricant film thickness, independent of the texture floor profile.

Three Femoral Stem Designs Without Corrosion: A Review of 2095 Stems

Introduction

Corrosion at the head-neck interface of modular components in total hip arthroplasty (THA) has been reported as a cause of failure of modern total hip replacement implants. While this method of failure has been well described, it remains poorly understood. The purpose of this study is to review the three most commonly used uncemented femoral stems at our institution over the last fifteen years and to correlate any established risk factors with rates of revision, particularly corrosion.

Methods

We reviewed 2095 patients from March 2000 to September 2015 who underwent total hip arthroplasty with one of three uncemented femoral stem designs. All stems were made of a Ti6Al4V alloy with a 12/14 taper design. We included only those stems coupled with a CoCr head and a highly crosslinked polyethylene liner. We evaluated age, gender, body mass index (BMI), femoral head size, head length, neck angle and offset and correlated these to the incidence of all cause revision, as well as revision excluding infection.

Results

There were no recognized corrosion-related revisions identified. There was no association between age, BMI, gender, head length, neck angle and offset to all cause revision or revision with infection excluded (p>0.05). Femoral head size less than 32mm was associated with higher all cause revision rates (OR 4.60 (95% CI 1.8, 11.8)) and when excluding infection as a reason for revision (OR 4.94 (95% CI 1.7, 14.41)).

Conclusion

Over the last fifteen years, we have not identified any cases of corrosion with the three most commonly used femoral stems used at out institution. While we acknowledge that no femoral stem is immune to corrosion, certain femoral stem designs may be uniquely resistant to this mode of failure.

Level of Evidence

III.

Korean epidemiology and trends in hip joint replacements

This study aimed to analyze the epidemiologic characteristics of patients who underwent hip arthroplasty using the Korean nationwide database and investigate the recent trends in implant fixation methods and bearing surface selection. We aimed to compare clinical characteristics and differences with the results from the registry of other western countries. We analyzed the data collected by the Health Insurance Review and Assessment Service database of Korea from 2007 to 2011 and the Main Surgery Statistical Yearbook from 2014 to 2018, published by the National Health Insurance Service. The number and rate of patients who underwent hip joint arthroplasty per 10,000 persons have been steadily increasing since 2007. There was a big difference in mean age and preoperative diagnosis of patients between the bipolar hemiarthroplasty and total hip arthroplasty groups. Most patients underwent surgery using a cementless biological fixation method, and the cemented fixation method was selectively used for a small portion of old aged osteoporotic patients. In relation to the use of bearing surfaces, the registry data showed that ceramic-ceramic bearings were used at an overwhelmingly high rate (81%) in Korea compared to other countries. The reason was attributable to various factors, such as patient’s age or economic status, differences in the health insurance system between countries, and recently reported complications, such as ceramic fracture or noise.

High Revision Rates of a Cementless Beta-Titanium Alloy Stem with Contamination-Free Roughened Surface in Primary Total Hip Arthroplasty

Optimal osseointegration of cementless total hip arthroplasty is essential for high stability and long-term survival. The purpose of this follow-up study was to evaluate the clinical and radiological outcome, the complications, and survival rates of a beta-titanium alloy stem with a specific grit-blasted-free surface. In 192 patients (mean age of 64.4 years), 202 consecutive primary total hip arthroplasties were performed using a cementless Hipstar^® stem (Stryker, Duisburg, DE). The Harris Hip Score (HHS) was assessed pre-operatively and post-operatively. Radiolucent lines were evaluated and the implant survival rate was calculated using Kaplan-Meier analysis. The mean follow-up was 7.71 years (range of 5.0–14.0 years). Overall, 15 revisions were performed. Early aseptic stem loosening was observed in six cases (2.97%). Radiolucent-lines adjacent to the stem were detected in 73 cases (83.02%), especially (70.46%) in the Gruen zones 1, 7, 8, and 14. The mean postoperative HHS was 92.65 points (range 42–100). The cumulative survival probability of the stem was 94.4% (95% CI 90.3 to 98.5%). Considering aseptic failure as an endpoint, the cumulative survival rate of the stem was 95.3% (95% CI 0.914 to 0.992) at six years of follow-up. Overall, an inferior mid-term implant survival was observed in comparison to well-established cementless stem designs.

Trends in the use of dual mobility bearings in hip arthroplasty

Aims

Dual mobility (DM) bearings are an attractive treatment option to obtain hip stability during challenging primary and revision total hip arthroplasty (THA) cases. The purpose of this study was to analyze data submitted to the American Joint Replacement Registry (AJRR) to characterize utilization trends of DM bearings in the USA.

Methods

All primary and revision THA procedures reported to AJRR from 2012 to 2018 were analyzed. Patients of all ages were included and subdivided into DM and traditional bearing surface cohorts. Patient demographics, geographical region, hospital size, and teaching affiliation were assessed. Associations were determined by chi-squared analysis and logistic regression was performed to assess outcome variables.

Results

A total of 406,900 primary and 34,745 revision THAs were identified, of which 35,455 (8.7%) and 8,031 (23.1%) received DM implants respectively. For primary THA, DM usage increased from 6.7% in 2012 to 12.0% in 2018. Among revision THA, DM use increased from 19.5% in 2012 to 30.6% in 2018. Patients < 50 years of age had the highest rates of DM implantation in every year examined. For each year of increase in age, there was a 0.4% decrease in the rate of DM utilization (odds ratio (OR) 0.996 (95% confidence interval (CI) 0.995 to 0.997); p < 0.001). Females were more likely to receive a DM implant compared to males (OR 1.077 (95% CI 1.054 to 1.100); p < 0.001). Major teaching institutions and smaller hospitals were associated with higher rates of utilization. DM articulations were used more commonly for dysplasia compared with osteoarthritis (OR 2.448 (95% CI 2.032 to 2.949); p < 0.001) during primary THA and for instability (OR 3.130 (95% CI 2.751 to 3.562) vs poly-wear; p < 0.001) in the revision setting.

Conclusion

DM articulations showed a marked increase in utilization during the period examined. Younger patient age, female sex, and hospital characteristics such as teaching status, smaller size, and geographical location were associated with increased utilization. DM articulations were used more frequently for primary THA in patients with dysplasia and for revision THA in patients being treated for instability. Cite this article: Bone Joint J 2020;102-B(7 Supple B):27–32.

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.

Total Hip Arthroplasty: Past, Present, and Future. What Has Been Achieved?

In the 1960s, Sir John Charnley introduced to clinical practice his concept of low-friction total hip arthroplasty (THA). Although early designs were plagued by poor performance and even failure, there have been steady advances in implant designs, biomaterials, surgical techniques and an understanding of the biomechanical restoration of the hip; these advances have contributed to improvements in implant survival and clinical outcomes of THA in the past three decades. With improved wear resistance and mechanical reliability, a potential to last for at least 25 to 30 years are now available for THA. In this review, we focus on the evolution of THA and review current controversies and future directions of this procedure based on a single surgeon's 29-year of experience at a single institution.

Effects of vitamin E incorporation in polyethylene on oxidative degradation, wear rates, immune response, and infections in total joint arthroplasty: a review of the current literature

Highly cross-linked ultrahigh molecular weight polyethylene (UHMWPE) was introduced to decrease wear debris and osteolysis. During cross-linking, free radicals are formed, making highly cross-linked polyethylene vulnerable to oxidative degradation. In order to reduce this process, anti-oxidant vitamin E can be incorporated in polyethylene. This review provides an overview of the effects of vitamin E incorporation on major complications in total joint arthroplasty: material failure due to oxidative degradation, wear debris and subsequent periprosthetic osteolysis, and prosthetic joint infections. Secondly, this review summarizes the first clinical results of total hip and knee arthroplasties with vitamin E incorporated highly cross-linked polyethylene. Based on in vitro studies, incorporation of vitamin E in polyethylene provides good oxidative protection and preserves low wear rates. Incorporation of vitamin E may have the beneficial effect of reduced inflammatory response to its wear particles. Some microorganisms showed reduced adherence to vitamin E-incorporated UHMWPE; however, clinical relevance is doubtful. Short-term clinical studies of total hip and knee arthroplasties with vitamin E-incorporated highly cross-linked UHMWPE reported good clinical results and wear rates similar to highly cross-linked UHMWPE without vitamin E.