The incidence of acetabular osteolysis in young patients with conventional versus highly crosslinked polyethylene

Effect of vitamin E-enhanced highly cross-linked polyethylene on wear rate and particle debris in anatomic total shoulder arthroplasty: a biomechanical comparison to ultrahigh-molecular-weight polyethylene

BACKGROUND

Particle-induced osteolysis resulting from polyethylene wear remains a source of implant failure in anatomic total shoulder designs. Modern polyethylene components are irradiated in an oxygen-free environment to induce cross-linking, but reducing the resulting free radicals with melting or heat annealing can compromise the component's mechanical properties. Vitamin E has been introduced as an adjuvant to thermal treatments. Anatomic shoulder arthroplasty models with a ceramic head component have demonstrated that vitamin E-enhanced polyethylene show improved wear compared with highly cross-linked polyethylene (HXLPE). This study aimed to assess the biomechanical wear properties and particle size characteristics of a novel vitamin E-enhanced highly cross-linked polyethylene (VEXPE) glenoid compared to a conventional ultrahigh-molecular-weight polyethylene (UHMWPE) glenoid against a cobalt chromium molybdenum (CoCrMo) head component.

METHODS

Biomechanical wear testing was performed to compare the VEXPE glenoid to UHMWPE glenoid with regard to pristine polyethylene wear and abrasive endurance against a polished CoCrMo alloy humeral head in an anatomic shoulder wear-simulation model. Cumulative mass loss (milligrams) was recorded, and wear rate calculated (milligrams per megacycle [Mc]). Under pristine wear conditions, particle analysis was performed, and functional biologic activity (FBA) was calculated to estimate particle debris osteolytic potential. In addition, 95% confidence intervals for all testing conditions were calculated.

RESULTS

The average pristine wear rate was statistically significantly lower for the VEXPE glenoid compared with the HXLPE glenoid (0.81 ± 0.64 mg/Mc vs. 7.00 ± 0.45 mg/Mc) (P < .05). Under abrasive wear conditions, the VEXPE glenoid had a statistically significant lower average wear rate compared with the UHMWPE glenoid comparator device (18.93 ± 5.80 mg/Mc vs. 40.47 ± 2.63 mg/Mc) (P < .05). The VEXPE glenoid demonstrated a statistically significant improvement in FBA compared with the HXLPE glenoid (0.21 ± 0.21 vs. 1.54 ± 0.49 (P < .05).

CONCLUSIONS

A new anatomic glenoid component with VEXPE demonstrated significantly improved pristine and abrasive wear properties with lower osteolytic particle debris potential compared with a conventional UHMWPE glenoid component. Vitamin E-enhanced polyethylene shows early promise in shoulder arthroplasty components. Long-term clinical and radiographic investigation needs to be performed to verify if these biomechanical wear properties translate to diminished long-term wear, osteolysis, and loosening.

Total hip arthroplasty outcomes in Ehlers-Danlos patients: data from the Statewide Planning and Research Cooperative System

INTRODUCTION

Ehlers-Danlos syndromes (EDS) are genetic connective tissue disorders affecting multiple organ systems that frequently result in connective tissue hyperlaxity and early osteoarthritis. Short- and long-term outcomes after primary total hip arthroplasty (THA) in this patient population remain poorly characterised. The primary purpose of this study is to compare postoperative outcomes and survivorship after primary THA in patients with and without EDS.

METHODS

The New York Statewide Planning and Research Cooperative System (SPARCS) database was queried for all patients undergoing primary elective THA between September 2009 and December 2020. Patients with EDS were identified using ICD9 and ICD10 diagnosis codes. Given the relatively low incidence of EDS in this patient population, the cohort was propensity-matched 1:10 to patients without diagnosis of EDS based on demographics characteristics and medical comorbidities as measured by the Elixhauser Comorbidity Index.

RESULTS

A total of 66 THA patients with and 660 without EDS were included in each group after 1:10 propensity-matching. There were no significant differences in baseline characteristics or THA indications. Early postoperative outcomes such as length of hospital stay and discharge disposition were similar. Emergency Room visits and inpatient readmission rates at 3 months postoperatively did not significantly differ between groups. Patients with EDS had a higher overall revision rate compared to those without (15.0% vs. 3.2%, p < 0.001). Revision free survival after primary THA in patients with EDS was significantly lower than those without EDS at 9-year follow-up. Cox proportional hazard regression demonstrated EDS patients had 7-times higher risk of revision (hazard ratio [HR] 7.43; 95% CI, 3.46-16.00; p < 0.001). Lastly, revision due to instability insignificantly trended higher in the EDS cohort (HR 2.29; 95% CI, 0.95-5.49; p = 0.063).

CONCLUSIONS

EDS patients undergoing primary THA have increased rate of all cause revision and demonstrate decreased revision free survival compared to non-EDS THA patients.

Investigation of contact behavior on a model of the dual-mobility artificial hip joint for Asians in different inner liner thicknesses

BACKGROUND

The four components that make up the current dual-mobility artificial hip joint design are the femoral head, the inner liner, the outer liner as a metal cover to prevent wear, and the acetabular cup. The acetabular cup and the outer liner were constructed of 316L stainless steel. At the same time, the inner liner was made of ultra-high-molecular-weight polyethylene (UHMWPE). As this new dual-mobility artificial hip joint has not been researched extensively, more tribological research is needed to predict wear. The thickness of the inner liner is a significant component to consider when calculating the contact pressure.

AIM

To make use of finite element analysis to gain a better understanding of the contact behavior in various inner liner thicknesses on a new model of a dual-mobility artificial hip joint, with the ultimate objective of determining the inner liner thickness that was most suitable for this particular type of dual-mobility artificial hip joint.

METHODS

In this study, the size of the femoral head was compared between two diameters (28 mm and 36 mm) and eight inner liner thicknesses ranging from 5 mm to 12 mm. Using the finite element method, the contact parameters, including the maximum contact pressure and contact area, have been evaluated in light of the Hertzian contact theory. The simulation was performed statically with dissipated energy and asymmetric behavior. The types of interaction were surface-to-surface contact and normal contact behavior.

RESULTS

The maximum contact pressures in the inner liner (UHMWPE) at a head diameter of 28 mm and 36 mm are between 3.7-13.5 MPa and 2.7-10.4 MPa, respectively. The maximum von Mises of the inner liner, outer liner, and acetabular cup are 2.4-11.4 MPa, 15.7-44.3 MPa, and 3.7-12.6 MPa, respectively, for 28 mm head. Then the maximum von Mises stresses of the 36 mm head are 1.9-8.9 MPa for the inner liner, 9.9-32.8 MPa for the outer liner, and 2.6-9.9 MPa for the acetabular cup. A head with a diameter of 28 mm should have an inner liner with a thickness of 12 mm. Whereas the head diameter was 36 mm, an inner liner thickness of 8 mm was suitable.

CONCLUSION

The contact pressures and von Mises stresses generated during this research can potentially be exploited in estimating the wear of dual-mobility artificial hip joints in general. Contact pressure and von Mises stress reduce with an increasing head diameter and inner liner's thickness. Present findings would become one of the references for orthopedic surgery for choosing suitable bearing geometric parameter of hip implant.

How Research Improves Clinical Care: The Case for Orthopaedic Surgeon Research Leadership and Collaboration: AOA Critical Issues Symposium

ABSTRACT

Improving the performance and impact of orthopaedic research is a critical leadership challenge. Musculoskeletal (MSK) conditions are a leading cause of disability worldwide, for which research investment and performance lags far behind the burden of disease. In the United States, MSK disorders account for the highest health care costs, have increased in incidence at the fastest rate, and exceed the combined costs of cardiovascular diseases and neoplasms. Despite the cost to society, the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), with primary responsibility for MSK research, receives <1.4% of the funds allocated to the National Institutes of Health (NIH). Although orthopaedic surgeons are leading providers of MSK clinical care, the dearth of orthopaedic clinician-scientists also greatly reduces representation of MSK scientific and clinical expertise among academic and scientific leaders. The goals of this symposium were to highlight the critical need for greater prioritization and investment in orthopaedic research and to engage orthopaedic leaders in addressing these needs. Compelling stories of research success from 3 orthopaedic chairs were featured to highlight how orthopaedic surgeon leadership in bench-to-bedside research substantially advances MSK clinical care. Seminar participants also emphasized the need to improve evidence-based clinical practice for which multicenter prospective cohort and registry studies represent opportunities for broader involvement. Prioritization of orthopaedic clinician-scientist development and formation of multidisciplinary partnerships with basic and translational scientists were emphasized as critical needs to advance MSK health. It is critical for orthopaedic chairs to "be invested in" and to "invest in" the success of orthopaedic research. This investment includes developing a professional climate that values research achievement and collaboration as well as implementing strategies to support and sustain research success. Finally, orthopaedic leaders need to advocate for federal research funding to be proportional to the economic burden of disease for which MSK conditions carry the highest current and projected costs. With health-care costs accounting for nearly one-fifth of the U.S. economy, increasing the investment in orthopaedic research to reduce the prevalence, disability, and morbidity from MSK disease needs to be a top orthopaedic and national leadership priority.

Head, acetabular liner composition, and rate of revision and wear in total hip arthroplasty: a Bayesian network meta-analysis

Total hip arthroplasty (THA) is a common procedure for patients suffering from hip pain e.g. from osteoarthritis, osteonecrosis, or hip fractures. The satisfaction of patients undergoing THA is influenced by the choice of implant type and material, with one key factor being the selection of the appropriate material combination for the bearing surface. In this Bayesian network meta-analysis, we investigated the impact of material combinations for the bearing surface on the longevity of hip implants. The wear penetration rate per year and the total wear penetration in the liner resulting from different material combinations, as well as the survival rate at last follow-up, were examined. We analyzed a total of 663,038 THAs, with 55% of patients being women. Mean patient age was 59.0 ± 8.1 years and mean BMI 27.6 ± 2.6 kg/m2. The combination of an aluminium oxide (Al2O3) head and an Al2O3 liner demonstrated the lowest wear penetration at last follow-up and the lowest rate of wear penetration per year. Additionally, the combination of a crosslinked polyethylene (XLPE) liner and a zircon oxide (ZrO2) head demonstrated the lowest rate of revision at last follow-up. These findings underscore the importance of careful material selection for hip implant bearing surfaces to optimize their longevity and patient satisfaction after THA.

Risk factors for liner wear and head migration in total hip arthroplasty: a systematic review

Total hip arthroplasty (THA) is a successful orthopaedic surgical procedure, and its longevity depends on bearing components and implant fixation. Optimizing polyethylene and ceramics has led to improved wear parameters and contributed to improved long-term outcomes. The present systematic review investigated whether time span from implantation, patient characteristics and performance status exert an influence on liner wear and head migration in THA. This study was conducted in conformity to the 2020 PRISMA guidelines. All the clinical investigations which reported quantitative data on the amount of liner wear and head migration in THA were considered. Only studies which reported quantitative data at least on one of the following patient characteristics were suitable: mean age, mean BMI (kg/m2), sex, side, time span between the index THA and the last follow-up (months) were eligible. A multiple linear model regression analysis was employed to verify the association between patient characteristics and the amount of liner wear and/or head migration. The Pearson Product-Moment Correlation Coefficient was used to assess the association between variables. Data from 12,629 patients were considered. The mean length of the follow-up was 90.5 ± 50.9 months. The mean age of patients at surgery was 58.4 ± 9.4 years, and the mean BMI was 27.2 ± 2.5 kg/m2. 57% (7199 of 12,629 patients) were women, and in 44% (5557 of 12,629 patients) THAs were performed on the left. The mean pre-operative Harris hip score was 46.5 ± 6.0 points. There was evidence of a moderate positive association between the amount of liner wear and the time elapsed between the index surgery to the follow-up (P = 0.02). There was evidence of a moderate positive association between the amount of head migration and the time elapsed between the index surgery to the follow-up (P = 0.01). No further statistically significant association was found. The time elapsed between the index surgery to the follow-up was the most important factor which influence the head migration and liner wear in THA. Patients' characteristics and preoperative physical activity did not influence the amount of head migration and liner wear.

Mid-Term Survival of Total Hip Arthroplasty in Patients Younger Than 55-year-old

BACKGROUND

Survivorship of total hip arthroplasty (THA) in younger patients is concerning given the inverse relationship between age and lifetime risk for revision. The purpose of this study is to determine if risk of revision has improved for patients aged 55 years or younger who undergo primary THA using modern polyethylene liners.

METHODS

A retrospective review identified 2,461 consented patients (2,814 hips) with minimum 2-year follow-up who underwent primary THA at our institution between September 2007 and August 2014 using components from a single manufacturer (Zimmer Biomet), all with vitamin E-infused highly crosslinked polyethylene acetabular inserts. There were 561 patients (643 THA; 23%) aged 55 or younger and 1,900 (2,171 THA; 77%) older than 55.

RESULTS

Mean follow-up was 5.0 years for both groups. There were more male patients in the younger (55%) than older (41%) group. Body mass index (BMI) was higher in younger patients independent of gender. Improvement in Harris hip score (HHS) was similar between groups. Kaplan-Meier survival to endpoint of all cause revision was similar between groups at 12 years (P = .8808) with 97.5% (95% CI: ±0.7%) for younger versus 97.1% (95% CI: ±0.6%) for older patients. Most frequent reason for revision overall was periprosthetic femoral fracture (21; 0.75%); univariate analysis revealed risk factors were female gender (P = .28) and age ≥65 years (P = .012).

CONCLUSION

Use of modern polyethylene, such as vitamin E-stabilized highly cross-linked, liners during THA may improve survivorship in younger patients undergoing THA. Younger patients undergoing primary THA with highly cross-linked polyethylene liners had no increased rate of revision at mid-term follow-up.

Highly cross-linked polyethylene in primary total knee arthroplasty is associated with a lower rate of revision for aseptic loosening: a meta-analysis of 962,467 cases

BACKGROUND

The evolution in total knee arthroplasty (TKA) includes the highly cross-linked polyethylene (HXLPE) which has been reported as an effective manner to reduce the wear of the polyethylene and the osteolysis. The purpose of the present study is to synthesize the results of comparative studies between HXLPE and conventional polyethylenes and determine their effect in primary TKA.

METHODS

The US National Library of Medicine (PubMed/MEDLINE) and the Cochrane Database of Systematic Reviews were queried for publications utilizing the following keywords: "cross-linked", "polyethylene", "HXLPE", "conventional", "total knee arthroplasty", "TKA", "total knee replacement" and "TKR" combined with Boolean operators AND and OR.

RESULTS

Ten studies met the inclusion criteria and were included in the present meta-analysis with 962,467 patients. No significant difference was found regarding the revision rate for any reason between the patients who received HXLPE and those with conventional liner (OR 0.67; 95% CI 0.39-1.18; I²: 97.7%). In addition, there was no difference regarding the radiolucent lines between the two types of liners (OR 0.54; 95% CI 0.20-1.49; I²: 69.4%). However, with data coming from seven studies enrolling a total of 411,543 patients, it was demonstrated that patients who received HXLPE were less likely to be revised due to aseptic loosening compared to the patients with conventional liners (OR 0.35; 95% CI 0.31-0.39; I²: 0.0%).

CONCLUSION

The present meta-analysis showed that regarding the overall revision rate and radiographic outcomes there was no significant difference between the two types of liners. On the other hand, the significantly less revision rate due to loosening supports the routine continued use of HXLPE in primary TKA.

Incidence of Osteolysis and Aseptic Loosening Following Metal-on-Highly Cross-Linked Polyethylene Hip Arthroplasty: A Systematic Review of Studies with Up to 15-Year Follow-up

BACKGROUND

This study compared the incidence of osteolysis, aseptic loosening, and revision following use of highly cross-linked polyethylene (HXLPE) or conventional polyethylene (CPE) at medium to long-term (>5 to 15 years) follow-up in primary total hip arthroplasty (THA). Incidences were quantified and compared with regard to age and method of implant fixation.

METHODS

Using the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) guidelines, 12 randomized controlled trials and 18 cohort studies were investigated for evidence-based outcomes following HXPLE and CPE use in 2,539 hips over a 5 to 15-year follow-up.

RESULTS

Lower rates of osteolysis, aseptic loosening, and implant revision were reported following use of HXLPE liners. Osteolysis was reduced from 25.4% with CPE to 4.05% with HXLPE in young patients, and from 29.7% to 6.6% in the older patient cohort. Similarities in osteolysis rates were observed when cemented (24.9% for CPE and 6.5% for HXLPE) and uncemented components (32.8% for CPE and 7.1% for HXLPE) were compared. No clear advantage in the type of HXLPE used was observed.

CONCLUSIONS

Over a follow-up period of up to 15 years, when compared with CPE, use of HXLPE liners reduced the incidence of osteolysis, aseptic loosening, and implant revision, regardless of the fixation method and including in younger and potentially more active patients.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Incidence and Characteristics of Osteolysis in HXLPE THA at 16-Year Follow up in Patients 50 Years and Less

INTRODUCTION

Young patients present a challenge for total hip arthroplasty (THA) survivorship. Highly cross-linked polyethylene (HXLPE) liners have decreased the prevalence of osteolysis; however, concerns exist regarding the biologic activity of wear particles. The purpose of this study was to determine the incidence and characteristics of osteolytic lesions in young HXLPE THA patients at an average 16-year follow up and determine the ability to detect osteolysis.

METHODS

We performed a retrospective study involving 22 patients (26 THA) under age 50 at primary THA receiving HXLPE liners coupled with cobalt-chrome (CoCr) femoral heads. Computed tomography (CT) scans were reviewed for osteolysis. Chi-squared analysis was used for categorical variables and unpaired Kruskal-Wallis rank-sum test for continuous variables. Logistic regression was used to compare wear rates between those patients with and without osteolysis.

RESULTS

The mean age at surgery was 38.5 years. The mean time from surgery to CT scan was sixteen years (range 14.25-19.5 years). Nine of the 26 THA showed osteolysis. The mean volume of the lesions was 2.8 cm3. Linear (mean 0.008 mm/y) and volumetric (mean 4.5 mm3/year) wear rates were negligible. One-third of osteolytic lesions were visible on radiographs. Logistic regression failed to demonstrate a correlation between wear rates or UCLA activity score and osteolysis.

CONCLUSION

We observed osteolysis in 35% of HXLPE THA in young patients at mean 16-year follow up despite zero revisions for wear-related problems and clinically insignificant wear rates.

LEVEL OF EVIDENCE

IV.

Revision rate of THA in patients younger than 40 years depends on primary diagnosis - a retrospective analysis with a minimum follow-up of 10 years

Background

Treating osteoarthritis in elderly patients with THA is very successful. However, surgeons hesitate to recommend THA in younger patients. The spectrum of etiologies for end stage hip disease in the younger population is diverse and therefore different courses may be assumed. Our objective was to evaluate THA revision rate within a minimum follow-up period of 10 years in young patients and to analyze the difference between different primary diagnoses.

Methods

We included 144 consecutive hips in 127 patients younger than 40 years, who received a primary THA from 01/1996 to 12/2007. Operative reports, clinical and radiographic documentation were reviewed to determine primary diagnosis, prior hip surgery, component specifications and revision surgery. 111 hips in 97 patients were available for outcome analysis with a minimum follow-up of 10 years.

Results

The mean age was 33 years (range 15–40 years) at the time of the index THA, 68 patients were female and 59 were male. Ten years revision rate on the prosthetic components was 13%. The most common primary diagnosis was DDH. DDH was associated with a risk of 17% for requiring a reoperation on the prosthetic components because of mechanical fatigue and therefore, significantly higher than for any other primary diagnosis (p = 0.005).

Conclusion

THA in young patients is associated with a high revision rate of 13% in 10 years. 17% of patients with DDH required revision surgery for mechanical fatigue within 10 years, which was significantly higher than for any other primary diagnosis (1.2%, OR 16.8).

Reasons for Revision: Primary Total Hip Arthroplasty Mechanisms of Failure

BACKGROUND

This study aimed to examine the major reasons for total hip arthroplasty (THA) failure and temporal patterns in THA revisions.

METHODS

A retrospective chart review was conducted on 535 revisions performed on 444 THAs from January 2010 to May 2019 at our institution.

RESULTS

The average time to revision THA was 8.51 ± 8.38 years, with 136 cases (30.9%) occurring within 2 years after primary THA. The major mechanisms of failure that resulted in revision surgery were mechanical failure (162, 36.5%), metallosis (95, 21.4%), dislocation or instability (65, 14.6%), periprosthetic fracture (46, 10.4%), infection (44, 9.9%), hematoma or poor wound healing (15, 3.4%), and pain or other (17, 3.8%).

CONCLUSION

Based on our institutional experience over the past decade, mechanical failure without dislocation, metallosis, dislocation, periprosthetic fracture, and infection are typical reasons patients present for primary THA revision. Revisions within 2 years after primary THA are more likely to be the result of infection and periprosthetic fracture. Mechanical failure is the most common reason for revision THA overall, and mechanical failure and metallosis are more likely to be the reason revision is necessary 2 or more years after primary THA.

Results of primary THA using 36 mm femoral heads on first-generation highly cross-linked polyethylene in patients less than 60 years of age: Minimum 10-year follow-ups

PURPOSE

Long-term results of total hip arthroplasty (THA) using highly cross-linked polyethylene (HXLPE) and metal femoral head with more than 10 years of follow-up have already been reported. However, most studies included results with a head size of 28 mm that could affect wear rates. The aim of this study was to evaluate the results of 36-mm metallic femoral heads on first-generation HXLPE in patients less than 60 years of age with a minimum follow-up of 10 years.

METHODS

Retrospective analysis included 54 cases from 47 patients. The mean age at the time of surgery was 47.22 years and the mean follow-up period was 131.04 months. Porous-coated cementless acetabular cups (Trilolgy®; Zimmer Inc., Warsaw, Indiana, USA) and HXLPE acetabular liners (Longevity®; Zimmer Inc.) were used for all cases. Acetabular cup abduction angles, anteversion angles, and wear rates of liner were measured using polyWare pro 3D distal version 5.10.

RESULTS

The average modified Harris hip score at the final follow-up was 88.48 (range 80-96). Average Merle d'Aubigne and Postel score was 15.57 (range 14-18). There was no acetabular cup or femoral stem failing due to aseptic loosening. The average steady-state wear rate determined using radiographs taken at 1 year postoperatively and at the latest follow-up was 0.053 ± 0.025 mm/year. There were no statistically significant differences in liner wear rate with respect to age, variety of the femoral stem, or liner thickness.

CONCLUSION

Results of THA with 36-mm metallic femoral heads on first-generation HXLPE in patients less than 60 years of age were satisfactory.

A potential need for surgeon consensus: Cementation techniques for total knee arthroplasty in orthopedic implant manufacturers' guidelines lack consistency

AIM

Given recent concerns regarding the influence of different cements and implants on the rate of aseptic failures in total knee arthroplasty (TKA), we wondered if cementation technique could play a role. The primary aim of this review was to collect and compare the surgeon education materials from eight orthopedic implant manufacturers to evaluate the manufacturers' recommended cementation technique in TKA and identify if there was any consistency in these readily available guides as to the best practices of cementation of their implants.

MATERIALS AND METHODS

We reviewed contemporary surgeon education guidelines for all TKA systems available from eight manufacturers. Variables included: cement type, batches prepared, surface preparation prior to application, cleaning and/or drying the bone surface, mixing the cement, the waiting phase after the cement has been mixed prior to application, pressurizing the cement, location of cement application, and the curing time. Data were recorded and organized for qualitative comparisons.

RESULTS

We identified a total of 43 guides covering 38 implants from eight different manufacturers. There were 41 surgical technique guides and two general brochures regarding cementation techniques available from the manufacturers. Even within the manufacturers' own guidelines for the different implants, there was a wide variety of differing guidelines on many aspects of the cementation technique.

CONCLUSION

There is clearly no consensus for a preferred cementation technique both within and among manufacturers' surgeon education materials regarding tibial baseplate cementation during TKA. Efforts may be needed to identify a best-practice cementation technique in an effort to reduce the number of TKA failures associated with aseptic loosening.

Computed Tomographic Osteolytic Analysis of a First-Generation Remelted Highly Cross-Linked Polyethylene in Total Hip Arthroplasty-At a Minimum of 15-Year Follow-Up

BACKGROUND

Low polyethylene wear rate and low incidence of osteolysis have been reported after total hip arthroplasty (THA) using first-generation remelted highly cross-linked polyethylene (HXLPE). However, osteolysis has not been evaluated in long-term studies of these patients (15 years or more). The present study assessed computed tomography (CT) images to determine the incidence of osteolysis associated with HXLPE in THA during at least 15 years of follow-up.

METHODS

We evaluated 105 primary THAs in 84 patients (77 women and 7 men). Mean follow-up was 15.9 years (range, 15-18 years). All THAs used a Longevity HXLPE liner and a 26-mm zirconia femoral head. Areas of osteolysis were identified from CT images using 3D and multiplanar reconstruction views.

RESULTS

CT 3D multiplanar reconstruction images at 15-year follow-up showed no obvious osteolysis in the acetabulum or femur of any patient. No patients developed cup loosening or liner breakage.

CONCLUSION

Our study indicates that first-generation remelted HXLPE liners do not increase the risk of osteolysis during 15-year follow-up and suggests that the wear particles from first-generation remelted HXLPE are less biologically active than those generated by conventional polyethylene devices.

Quantitative Measurements of Backside Wear in Acetabular Hip Joint Replacement: Conventional Polyethylene Versus Cross-Linked Polyethylene

As shown in previous studies, the modification of conventional polyethylene (CPE) to cross-linked polyethylene (XLPE) and the contribution of antioxidants result in a reduction in total wear. The aim of this study was to evaluate XLPE inserts with vitamin E and CPE regarding their resistance to the backside wear mechanism. A cementless hip cup system (Plasmafit^® Plus 7, Aesculap) was dynamically loaded using CPE and XLPE inserts. The backside wear was isolated, generated and collected using the two-chamber principle. The chambers were filled with ultrapure water. After 2 × 10⁶ cycles, the fluids were examined for wear particles according to a particle analysis. Using XLPE inserts, the backside wear was significantly reduced by 35%. While XLPE backside wear particles are significantly larger than CPE particles, they do not differ in their morphology. This study confirms the greater resistance to backside wear of XLPE compared to CPE. It can be assumed that the improved fatigue resistance of the vitamin E-stabilized XLPE inserts demonstrates XLPE’s effectiveness against micro-motion and the resulting changing tensions in interface areas like surface breakdown, pitting and the release of very small particles.

High risk of hip dislocation following polyethylene liner exchange in total hip arthroplasty-is cup revision necessary?

PURPOSE

Polyethylene (PE) wear remains a common reason for revision surgery following total hip arthroplasty (THA). An established treatment method is isolated liner exchange in a well-fixed acetabular cup and entails a known high risk of hip dislocation after revision surgery. The purpose of this retrospective study was to determine the rate of hip dislocation after liner exchange.

METHODS

Patients were included if (1) the PE liner was removable, (2) the acetabular shell was stable with acceptable orientation, (3) no osteolysis around the acetabular cup was found and (4) no dislocation of the THA occurred before revision surgery. We reviewed medical histories and performed radiological measurements using Einzel-Bild-Röntgen-Analyse (EBRA) software. EBRA measurements and statistical investigations were performed by two independent investigators.

RESULTS

A total of 82 patients were included in our study. Mean follow-up was six (range: 3.6-9.9) years. In 13 (15.8%) patients THA dislocations occurred at a mean postoperative period of 20.2 (range: 1-44) weeks after revising the PE liner. This is equivalent to an absolute risk increase of 16% after revision surgery, which results in a number needed to harm of 6. This means that every sixth patient with isolated liner exchange can expect to experience dislocation due to wear.

CONCLUSION

In conclusion, isolated exchange of the polyethylene liner because of wear showed a high risk of dislocation and further cup revision. Our results suggest that the threshold for revising well-fixed components in the case of liner wear should be lowered.

TRIAL REGISTRATION NUMBER AND DATE OF REGISTRATION

Number: 20140710-1012 and Date: 2016-03-09.

Titanium acetabular cementless cups combined with highly crosslinked polyethylene liner have very low rates of aseptic loosening

BACKGROUND

There is a clear tendency towards cementless acetabular components in primary total hip arthroplasty.

OBJECTIVE

The aim of this study was to assess the long-term clinical and radiological outcome of titanium cementless acetabular cups when combined with a highly crosslinked polyethylene liner.

METHODS

This study is a retrospective follow-up of 67 cups in 64 patients. Clinical outcomes were assessed using the Harris Hip Score. Radiolucent lines, osteolysis and loosening were assessed radiologically. Implant survival was determined using the Kaplan-Meier analysis.

RESULTS

The average Harris Hip Score at follow-up was 80.3 ± 14.5. Signs of osteolysis were observed in 7.1% of the radiographs. No aseptic loosening of the cup was reported. Survival of the cup with aseptic loosening as an endpoint was 100%. A comparison with 19 other studies using the same material combination demonstrated very similar results. All manufacturers with available studies have at least one report of 100% survivorship at 10-year follow-up for their titanium cup and highly crosslinked polyethylene acetabular component combination with aseptic loosening as an endpoint.

CONCLUSIONS

The data suggests that the rate of aseptic loosening of a titanium cup combined with a highly-crosslinked polyethylene liner at 10-year follow-up could be as low as 0%.

Cross-Linked Versus Conventional Polyethylene for Long-Term Clinical Outcomes After Total Hip Arthroplasty: A Systematic Review and Meta-Analysis

Background: Cross-linked polyethylene (HXLPE) liners have been used for total hip arthroplasty (THA) to address the problem of osteolysis and revision surgery associated with conventional polyethylene (CPE) liners. This systematic review and meta-analysis investigated the long-term efficacy of HXLPE in preventing revision surgery and radiological osteolysis in comparison to CPE. Materials and Methods: A comprehensive search of PubMed, Embase, and the Cochrane Library from their respective inception to September 2018 was conducted to identify potential candidate articles. Data were pooled using Stata software 14.0. The quality of randomized controlled trials (RCTs) and observational studies was assessed by two different authors using the Cochrane risk-of-bias tool and the Newcastle-Ottawa scale (NOS), respectively. Results: Eight RCTs and six observational studies were included in this review. The pooled results significantly favored HXLPE over CPE in terms of total number of revisions and radiological osteolysis, with a risk reduction of 78% (95% confidence interval [CI] 0.13-0.36; p < 0.001) and 80% (95% CI 0.13-0.29; p < 0.001), respectively. Additionally, subgroup analyses of pooled data from RCTs and observational studies both showed the efficacy of HXLPE in the prevention of revision and osteolysis. Polyethylene wear in the HXLPE group was significantly less than that in the CPE group in terms of linear wear rates and head penetration rates (both p < 0.001). No significant differences were observed with regard to functional outcomes. Conclusions: The current evidence shows that HXLPE significantly improved the clinical and radiographic outcomes, but not the functional outcomes, in comparison to CPE in long-term follow-up.

Fifteen-Year Results of Total Hip Arthroplasty With Cobalt-Chromium Femoral Heads on Highly Cross-Linked Polyethylene in Patients 50 Years and Less

BACKGROUND

Highly cross-linked polyethylene (HXLPE) is the most commonly used bearing surface in total hip arthroplasty (THA) because of its superior wear properties, but long-term results in young patients are limited. Mid-term survivorship has been promising; however, polyethylene wear rates and need for revision surgeries remain a concern in this population. The purpose of our study is to investigate polyethylene wear rates, implant survivorship, wear-related revisions, and patient-reported outcomes in a young patient cohort at 15-year follow-up.

METHODS

We performed a retrospective study of a prospective longitudinal cohort of 82 consecutive patients (89 hips) who underwent primary THA with an HXLPE acetabular liner and a cobalt-chromium femoral head. The mean age at the time of surgery for the cohort was 38.8 years (range 12-50). All patients received HXLPE liners with a cementless acetabular component coupled with a cobalt-chrome femoral head through a posterior approach with a cementless femoral component. All components were from a single manufacturer. We recorded University of California, Los Angeles Activity, and modified Harris Hip Scores. Wear calculations were made using the Martell Hip Analysis Suite (Version 8.0.4.3).

RESULTS

At average 15 years (range 13.1-18.5), there was a revision-free survivorship of 97.8% in our HXLPE group with no wear-related revisions. We observed a linear wear rate of 0.0185 mm/y (standard deviation 0.05) after accounting for a 1-year bedding-in period. The volumetric wear rate was found to be 12.80 mm³/y (standard deviation 22.69). These numbers are registered as clinically undetectable and are comparable to steady state wear rates in the same cohort of patients at earlier time points. We found no radiographic changes concerning osteolysis. We observed excellent patient-reported outcomes at this time point with improvements in modified Harris Hip Scores (35.3 [22.5], P < .0001) and University of California, Los Angeles Activity Scores (median 6.0, P < .0001).

CONCLUSION

At 15-year follow-up, we demonstrated that HXLPE bearings in this young cohort had excellent wear properties, maintained superior clinical improvements, and underwent no wear-related revision operations. The HXLPE and cobalt-chrome bearing couple continues to be extremely effective 15 years after primary THA in patients less than 50 years.

LEVEL OF EVIDENCE

IV.

Evaluation and Treatment of Patients With Acetabular Osteolysis After Total Hip Arthroplasty

As the demand for total hip arthroplasty (THA) continues to increase, the burden of revision THA is also expected to increase. Although the quality of polyethylene has improved markedly, osteolysis continues to be a risk for older designs and younger, active patients. Although progressive but typically asymptomatic in early stages, osteolysis can result in component failure and complicate revision surgery. Serial radiographs are paramount for monitoring progression. Although select cases may be treated with observation, surgery should be considered based on age, activity level, and projected life span. Well-fixed, noncemented modular acetabular components may be treated with curettage and bone grafting, as well as having to bear liner exchange with retention of the acetabular shell. However, in the setting of osteolysis, it is controversial whether bone grafting and component retention is superior to cup revision. This review explores the pathophysiology of osteolysis after THA and provides a comprehensive analysis of the evaluation and treatment of patients with osteolysis.

Backside wear in acetabular hip joint replacement

INTRODUCTION

Besides head-insert articulation in hip joint replacements, micro-motions between the backside of assembled polyethylene acetabular liners and the metal cup may cause additional wear. Pelvic osteolysis frequently occurs in the region of screw holes, and cup loosening hints to clinically relevant amounts of polyethylene backside wear. It has yet to be confirmed whether backside wear particles differ in size and morphology compared to articulating wear. Previous methods have been limited to subjective assessment of backside surface damages without consideration of wear debris. The aim of this study was to develop and validate a method for quantitative in vitro measurements of polyethylene backside wear in artificial hip cups and to characterize these wear particles for the first time.

METHODS

Titanium cup-systems (Plasmafit®Plus7, Aesculap, UHMWPE liner) were sinusoidally loaded (2.5 kN) and a torque of 5 Nm was simultaneously applied. The front and rear side of the cup were separated to isolate backside wear. After 2 × 10⁶ cycles the surrounding fluid was filtered and a particle analysis was performed.

RESULTS

Backside wear had a particles size of 64.1 ± 1.9 nm and was verified as round and oval particles with partly rough outlines. An estimated total number of particles of 1.26 × 10⁹ ± 1.67 × 10⁸ per 10⁶ cycles was determined.

CONCLUSION

Backside wear was estimated to be several times lower than published values of articulating wear. However, polyethylene backside wear particles represented significantly smaller particles with partly roughened outlines than articulating wear particles and may therefore cause higher biological response in macrophage-mediated bone resorption compared to articulated particles.

STATEMENT OF SIGNIFICANCE

Within this study, an analytical method for quantitative measuring polyethylene backside wear of artificial hip cups was successfully developed and validated for the first time. It could be shown that backside wear is still present, even in modern cup-systems. These findings can be further used for investigations of the osteolytic potential of polyethylene particles, for evaluating and improving new implant systems and to evaluate the effectiveness of screw hole plugs to prevent the particle migration to the acetabulum.

Manufacturing, oxidation, mechanical properties and clinical performance of highly cross-linked polyethylene in total hip arthroplasty

Ultra-high molecular weight polyethylene (UHMWPE) continues to be the gold standard bearing surface in total hip arthroplasty (THA) for nearly 5 decades. Highly cross-linked UHMWPE (HXLPE) was adapted for routine use in the early 2000s to reduce the revision rates related to wear, osteolysis, and aseptic loosening resulting from conventional UHMWPE wear. Since its inception, consistent evidence showing reduced wear rates and osteolysis supports the use of HXLPE in THA. High quality studies demonstrating the advantage in long term survivorship of HXLPE over conventional UHMWPE are emerging. Though retrieval studies have demonstrated evidence of in vivo oxidation and fatigue related damage at the rim of the first generation HXLPE liners, clinical significance of this remains to be seen. Second-generation sequentially annealed and vitamin E containing HXLPE liners demonstrate improved mechanical properties, resistance to oxidation, and equivalent wear rates in comparison to their first-generation counterparts, but long term success remains to be seen.

Up to 18-Year Follow-Up Wear Analysis of a First-Generation Highly Cross-Linked Polyethylene in Primary Total Hip Arthroplasty

BACKGROUND

The advent of highly cross-linked polyethylene (HCLPE) has significantly improved total hip arthroplasty survivorship. HCLPE has been shown to improve wear properties in midterm outcomes when compared to traditional polyethylene liners; however, there is a paucity of studies evaluating long-term outcomes. In addition, there is concern that wear rates may accelerate as the implant ages. Thus, the aims of this study are to report on the longest-to-date follow-up of a specific first-generation HCLPE liner and to determine whether there is a change in the annual wear rate over time.

METHODS

Forty hips in 38 patients which were previously reported on in a midterm study were included in this long-term follow-up study. Patients in this cohort all received total hip arthroplasty between March 1999 and August 2004 using the Crossfire HCLPE liner. Annual wear rates (mm/y) were calculated for this cohort. Patients were contacted and asked about complications or revision procedures they may have had since the index procedure.

RESULTS

Clinical follow-up averaged 12.9 years with a range of 7-18 years. The average follow-up duration was 12.5 years with a range of 10-17 years. Linear wear was found to be 0.056 ± 0.036 mm/y. Osteolysis was not observed in any of the patients with greater than 10-year radiographic follow-up. Furthermore, only 1 patient required revision surgery following a mechanical fall.

CONCLUSION

Our study demonstrates the long-term wear rates associated with HCLPE liners continue to match rates published in midterm studies. Previously, we have reported that this cohort had an average annual wear rate of 0.05 mm/y over 10 years. This most recent report demonstrates a similar wear rate with up to 18-year follow-up.

Hip resurfacing with a highly cross-linked polyethylene acetabular liner and a titanium nitride-coated femoral component

AIMS

This study evaluated a specific hip resurfacing system to determine the: (1) function and complications, (2) implant survivorship, (3) acetabular bone conservation and joint biomechanics and (4) osteolysis and polyethylene wear.

METHODS

I performed 234 resurfacing procedures (192 patients) using a two-piece titanium acetabular component with a 4 mm highly cross-linked polyethylene liner and a cementless titanium nitride-coated titanium femoral component. Function was assessed with Harris Hip, WOMAC, SF-12, and UCLA scores. Radiography and CT scans were used to evaluate bone retention, component position, joint biomechanics, and osteolysis. Retrieved polyethylene liners were analyzed for wear.

RESULTS

Median follow-up was 8 years and patients averaged 48 years of age at surgery. The mean Harris Hip Score was 96 and all scores improved significantly. Kaplan-Meier survivorship was 97%. The mean medial acetabular thickness was 9 mm postoperatively versus 14 mm preoperatively ( p = 0.019). Femoral bone conservation (head:neck ratio) was 1.36 postoperatively versus 1.42 preoperatively ( p = 0.02). There was no polyethylene wear through or osteolysis. Eight polyethylene retrievals had a mean wear of 0.05 mm/yr.

CONCLUSIONS

Resurfacing with a highly cross-linked polyethylene acetabular component and a titanium nitride-coated titanium cementless femoral component is a reliable and bone-conserving procedure at mid-term.

Large Metal Heads and Highly Cross-Linked Polyethylene Provide Low Wear and Complications at 5-13 Years

BACKGROUND

Highly cross-linked polyethylene (XLPE) is reported to have low rates of linear and volumetric wear at 10-14 years. In a prior study, larger (36 and 40 mm) femoral heads were associated with more volumetric wear, but there were only 12 hips with these heads.

METHODS

We evaluated 107 hips (93 patients, with a mean age of 76 years) with one design of uncemented acetabular component, a 36 (90 hips) or 40 mm (17 hips) metal femoral head, and one electron beam 100 kGy irradiated and remelted XLPE at a mean follow-up of 8 years (range 5-13 years). Selection of these femoral heads was based on several factors, including the perceived risk of dislocation, the outer diameter size of the acetabular component, and liner availability. Measurements of linear and volumetric wear were performed in one experienced laboratory by the Martell method and analyzed using the first-to-last method. Standard radiographs, with additional Judet views, were used to detect periprosthetic osteolysis. Clinical records were used to determine the complications of dislocation, liner fracture, and painful trunnion corrosion.

RESULTS

For the entire cohort, the median linear wear rate was 0.041 mm/y (95% confidence interval, 0.031-0.057) and the median volumetric wear rate was 34.6 mm³/y (95% confidence interval, 31.4-53.5). With the numbers available, there was no difference in linear or volumetric wear between the 36 and 40 mm head sizes. Small, asymptomatic osteolytic lesions were noted in 3 hips (2%). There were 3 patients (3%) with dislocation (2 early and 1 late), but these have not had a revision. There were no revisions for loosening, no liner fracture, and no patient with symptomatic trunnion corrosion.

CONCLUSION

This acetabular component and XLPE with large metal heads had low rates of linear and volumetric wear. Large metal femoral heads did not lead to liner fracture, loosening, or symptomatic trunnion corrosion in this patient population. However, we recommend longer clinical follow-up studies and caution in the routine use of larger metal femoral heads in other, younger patient populations.

Estimating the osteolysis-free life of a total hip prosthesis depending on the linear wear rate and head size

We present a model to estimate the osteolysis-free life of total hip arthroplasty, depending on linear wear rate and femoral head size. An estimate of the radiologic osteolysis threshold was calculated, which was based on volumetric wear. The osteolysis-free life of the cup was estimated from the quotient of the osteolysis threshold and volumetric wear rate, which was calculated from the linear wear rate. The impact of the direction of linear wear was determined by sensitivity analysis. From our review, we calculated a weighted mean polyethylene volume of approximately 670 mm³ as osteolysis threshold. Osteolysis-free life of less than 20 years was estimated for linear wear rates of 50 µm/year for head sizes of 32 mm or more, or for linear wear rates of 100 µm/year for any head size. For head sizes of 36 and 40 mm with a linear wear rate of 50 µm/year, the osteolysis-free period is estimated to be only 14.10 and 11.42 years, respectively. Sensitivity analysis showed reasonably robust results. With the aim of osteolysis-free life of more than 20 years, our study presents a viable model to determine maximum possible head size for articulations. Osteolysis-free period for 36 and 40 mm head sizes are far too low for conventional polyethylenes. As the threshold wear volume for highly crosslinked polyethylene is, as of yet, unknown, more research is warranted before our model can be generalized to XLPE.

Bearing surfaces in primary total hip arthroplasty

Total hip arthroplasty (THA) is widely considered one of the most successful surgical procedures in orthopaedics. It is associated with high satisfaction rates and significant improvements in quality of life following surgery. On the other hand, the main cause of late revision is osteolysis and wear, often a result of failure of bearing surfaces.Currently, several options are available to the surgeon when choosing the bearing surface in THA (ceramic-on-ceramic (CoC), ceramic-on-polyethylene (CoPE), metal-on-polyethylene (MoPE)), each with advantages and drawbacks.Very few studies have directly compared the various combinations of bearings at long-term follow-up. Randomized controlled trials show similar short- to mid-term survivorship among the best performing bearing surfaces (CoC, CoXLPE and MoXLPE). Selection of the bearing surface is often 'experience-based' rather than 'evidence-based'.The aim of this paper is therefore to evaluate the main advantages and drawbacks of various types of tribology in THA, while providing practical suggestions for the surgeon on the most suitable bearing surface option for each patient. Cite this article: EFORT Open Rev 2018;3 DOI: 10.1302/2058-5241.3.180300.

The effect of bearing type on the outcome of total hip arthroplasty

Background and purpose - Alternative bearing surfaces such as ceramics and highly crosslinked polyethylene (HXLPE) were developed in order to further improve implant performance of total hip arthroplasties (THAs). Whether these alternative bearing surfaces result in increased longevity is subject to debate. Patients and methods - Using the Dutch Arthroplasty Register (LROI), we identified all patients with a primary, non-metal-on-metal THA implanted in the Netherlands in the period 2007-2016 (n = 209,912). Cumulative incidence of revision was calculated to determine differences in survivorship of THAs according to bearing type: metal-on-polyethylene (MoPE), metal-on-HXLPE (MoHXLPE), ceramic-on-polyethylene (CoPE), ceramic-on-HXLPE (CoHXLPE), ceramic-on-ceramic (CoC), and oxidized-zirconium-on-(HXL)polyethylene (Ox(HXL)PE). Multivariable Cox proportional hazard regression ratios (HRs) were used for comparisons. Results - After adjustment for confounders, CoHXLPE, CoC, and Ox(HXL)PE resulted in a statistically significantly lower risk of revision compared with MoPE after 9 years follow-up (HR =0.8-0.9 respectively, compared with HR =1.0). For small (22-28 mm) femoral head THAs, lower revision rates were found for CoPE and CoHXLPE (HR =0.9). In the 36 mm femoral head subgroup, CoC-bearing THAs had a lower HR compared with MoHXLPE (HR =0.7 versus 1.0). Crude revision rates in young patients (< 60 years) for CoHXLPE, CoC, and Ox(HXL)PE (HR =0.7) were lower than MoPE (HR =1.0). However, after adjustment for case mix and confounders these differences were not statistically significant. Interpretation - We found a mid-term lower risk of revision for CoHXLPE, CoC, and Ox(HXL)PE bearings compared with traditional MoPE-bearing surfaces.

Polyethylene and highly cross-linked polyethylene for cemented total hip arthroplasty: A comparison of over ten-year clinical and radiographic results

INTRODUCTION

We investigated the long-term tribological outcomes of conventional polyethylene (CPE) and highly cross-linked polyethylene (HXLPE).

METHODS

Ninety-four consecutive primary cemented THAs were performed using either HXLPE or CPE at our hospital. CPE sockets were used in 26 hips, and HXLPE sockets were implanted in 68 hips.

RESULTS

A 10-year follow-up was completed for 69 cases. Linear wear rates of 0.138 ± 0.074 mm/year for CPE and 0.011 ± 0.020 mm/year for HXLPE were calculated. Osteolysis was identified in 10 cases (CPE group, 7; HXLPE group, 3).

CONCLUSION

HXLPE had significantly less wear than CPE, and polyethylene wear was associated with osteolysis.

Wear of XLPE liner against zirconium heads in cementless total hip arthroplasty for patients under 40 years of age

INTRODUCTION

Total hip arthroplasty (THA) in the young is challenging. The purpose of this study was to retrospectively determine the clinical, radiographic, and polyethylene wear rate of relatively young patients.

METHODS

We evaluated the outcome of consecutive patients receiving primary THA who were under 40 years of age with a minimum 10-year follow-up. Indications for THA in these patients were osteoarthritis due to developmental dysplasia of the hip joint (9 hips), osteonecrosis of the femoral head (7 hips), juvenile idiopathic arthritis (2 hips), and osteoarthritis due to Perthes disease (1 hip). All THA were performed with a cross-linked ultra-high-molecular-weight polyethylene (XLPE) liner against zirconium heads with cementless implants.

RESULTS

The average Japanese Orthopaedic Association hip score significantly improved from 42 to 93 points at the latest follow-up. The mean steady wear was 0.015 mm/year (maximum 0.033 mm/year), and the mean creep wear was 0.111 mm (maximum 0.4 mm). Osteolysis was observed around 1 acetabular component and 2 stems. 1 femoral component had subsidence over 5 mm. All of the femoral components achieved fixation with an optimal interface with spot welds at the latest follow-up. Stress shielding was observed in all hips.

CONCLUSIONS

THA using an XLPE liner against zirconium heads appeared to have improved THA longevity. However, the imaging findings in some cases were suggestive of wear debris. A rigorous continual follow-up is required for relatively young patients undergoing THA.

Effects of pulsed electromagnetic fields and platelet rich plasma in preventing osteoclastogenesis in an in vitro model of osteolysis

Osteolysis is the main limiting cause for the survival of an orthopedic prosthesis and is accompanied by an enhancement in osteoclastogenesis and inflammation, due by wear debris formation. Unfortunately therapeutic treatments, besides revision surgery, are not available. The aim of the present study was to evaluate the effects of Pulsed Electro Magnetic Fields (PEMFs) and platelet rich plasma (PRP), alone or in combination, in an in vitro model of osteolysis. Rats peripheral blood mononuclear cells were cultured on Ultra High Molecular Weight Polyethylene particles and divided into four groups of treatments: (1) PEMF stimulation (12 hr/day, 2.5 mT, 75 Hz, 1.3 ms pulse duration); (2) 10% PRP; (3) combination of PEMFs, and PRP; (4) no treatment. Treatments were performed for 3 days and cell viability, osteoclast number, expression of genes related to osteoclastogenesis and inflammation and production of pro-inflammatory cytokines were assessed up to 14 days. PEMF stimulation exerted best results because it increased cell viability at early time points and counteracted osteoclastogenesis at 14 days. On the contrary, PRP increased osteoclastogenesis and reduced cell viability in comparison to PEMFs alone. The combination of PEMFs and PRP increased cell viability over time and reduced osteoclastogenesis in comparison to PRP alone. However, these positive results did not exceed the level achieved by PEMF alone. At longer time points PEMF could not counteract osteoclastogenesis increased by PRP. Regarding inflammation, all treatments maintained the production of pro-inflammatory cytokines at low level, although PRP increased the level of interleukin 1 beta.

Polyethylene and highly cross-linked polyethylene for cemented total hip arthroplasty: A comparison of over ten-year clinical and radiographic results

INTRODUCTION

We investigated the long-term tribological outcomes of conventional polyethylene (CPE) and highly cross-linked polyethylene (HXLPE).

METHODS

Ninety-four consecutive primary cemented THAs were performed using either HXLPE or CPE at our hospital. CPE sockets were used in 26 hips, and HXLPE sockets were implanted in 68 hips.

RESULTS

A 10-year follow-up was completed for 69 cases. Linear wear rates of 0.138 ± 0.074 mm/year for CPE and 0.011 ± 0.020 mm/year for HXLPE were calculated. Osteolysis was identified in 10 cases (CPE group, 7; HXLPE group, 3).

CONCLUSION

HXLPE had significantly less wear than CPE, and polyethylene wear was associated with osteolysis.

The Relationship Between Polyethylene Wear and Periprosthetic Osteolysis in Total Hip Arthroplasty at 12 Years in a Randomized Controlled Trial Cohort

BACKGROUND

Polyethylene acetabular components are common in hip arthroplasty. Highly cross-linked polyethylene (HXLPE) has lower wear than ultra-high molecular weight polyethylene (UHMWPE). Evidence suggests that wear particles induce inflammation causing periprosthetic osteolysis contributing to implant loosening with wear rates of 0.05 mm/y were considered safe. We aimed to compare incidence and volume of periacetabular osteolysis between HXLPE and UHMWPE using computed tomography.

METHODS

Initially, 54 hips in 53 patients were randomized to HXLPE or UHMWPE acetabular liner. At 10 years, 39 hips in 38 patients remained for the radiostereometric analysis' demonstrating significantly lower wear in the HXLPE group. At 12 years, 14 hips in 13 patients were lost to follow-up leaving 25 hips for computed tomography assessment. Images were reconstructed to detect osteolysis and where identified, areas were segmented and volumized.

RESULTS

Osteolysis was observed in 8 patients, 7 from the UHMWPE group and only 1 from the HXLPE group (Fisher exact, P = .042). There was no correlation between the amount of polyethylene wear and osteolysis volume; however, the radiostereometric analysis-measured wear rate in patients with osteolysis from both groups was significantly higher than overall average wear rate.

CONCLUSION

This data demonstrates lower incidence of periacetabular osteolysis in the HXLPE group of a small cohort. Although numbers are too low to estimate causation, in the context of lower wear in the HXLPE group, this finding supports the hypothesis that HXLPE may not elevate osteolysis risk, and hence does not suggest that HXLPE wear particles are more biologically active than those generated by earlier generations of polyethylene.

Wear Rates of Larger-Diameter Cross-Linked Polyethylene at 5 to 13 Years: Does Liner Thickness or Component Position Matter?

BACKGROUND

Cross-linked polyethylene (XLPE) has demonstrated significantly reduced wear and osteolysis into the second decade for total hip arthroplasty. There is a relative paucity of data with ≥36-mm bearings. Issues include potential effects of reduced liner thickness and component position on wear, osteolysis, and mechanical failure of the bearing.

METHODS

Radiographs of 48 primary total hip arthroplasties with ≥36-mm modular XLPE bearings were analyzed at a minimum 5 years postoperative on serial radiographs using a validated, edge-detection-based algorithm. Subgroups were examined to assess the effect of bearing diameter, liner thickness, acetabular abduction angle, and acetabular anteversion on XLPE wear.

RESULTS

There was no significant difference in volumetric wear when subgroups were stratified by component factors: liner thickness (<6.5 mm vs ≥6.5 mm) 40.69 mm³/y vs 24.47 mm³/y, respectively (P = .315); acetabular component abduction angle (<45° vs ≥45°): 38.68 mm³/y vs 27.8 mm³/y, respectively (P = .522); acetabular anteversion (<20° vs ≥20°): 41.32 mm³/y vs 31.79 mm³/y, respectively (P = .521). There were no dislocations, mechanical failures, or revisions. There were 7 hips with volumetric wear rates ≥80 mm³/y; 1 had possible osteolysis.

CONCLUSION

Larger-diameter XLPE wear was not measurably affected by liner thickness, acetabular abduction angle, or acetabular anteversion. However, there is a trend for increasing volumetric wear with increasing bearing size. Wear outliers do occur, and continued follow-up of larger-diameter XLPE bearings is warranted.

Hip Resurfacing Using Highly Cross-linked Polyethylene: Prospective Study Results at 8.5 Years

BACKGROUND

Hip resurfacing is an option to consider when treating younger, more active patients. Advantages over total hip arthroplasty include a more normal gait and a lower incidence of thigh pain.

METHODS

In this prospective study, 190 hip resurfacing procedures (164 participants) were performed using a cobalt-chromium femoral component and a cementless acetabular cup with a 3.8-mm highly cross-linked polyethylene acetabular liner.

RESULTS

The mean follow-up was 8.5 (range, 7-10) years. Two participants were lost to follow-up and 2 died. One participant underwent successful revision surgery for acetabular loosening. Four participants underwent successful revision to a total hip arthroplasty because of femoral neck fracture (2), femoral loosening, or infection. The Kaplan-Meier survivorship was 97%. Acetabular bone conservation was assessed using computed tomography by measuring the medial acetabular wall. The mean thickness was 9 mm. Femoral bone was well preserved with a mean head:neck ratio of 1.37. There were 4 (2%) osteolytic defects up to 0.9 cm(3) on computed tomography and no instances of impending polyethylene wear-through. Seven polyethylene retrievals had a measured wear rate of 0.05 mm/y.

CONCLUSION

Hip resurfacing using a highly cross-linked polyethylene acetabular component is a reliable procedure. Both femoral and acetabular bones are reasonably preserved compared with prior resurfacing methods. The low incidence of osteolysis and the low rate of wear found on retrievals suggest that many years of use in highly active patients is possible.

Highly Cross-linked Polyethylene Provides Decreased Osteolysis and Reoperation at Minimum 10-Year Follow-Up

BACKGROUND

Highly cross-linked polyethylene was introduced to decrease periprosthetic osteolysis and reoperation, but this has not been conclusively proven.

METHODS

One surgeon performed 513 consecutive primary total hip arthroplasties (450 patients) using 1 modern, cementless, titanium-mesh acetabular component with screw fixation. This study analyzed the differences in the rate of reoperation and incidence of osteolysis between 133 hips with standard and 112 hips with highly cross-linked polyethylene at minimum 10-year follow-up time.

RESULTS

Of the entire cohort of 513 hips, no acetabular component was removed or revised for aseptic loosening. There were significantly more reoperations in the cohort with standard polyethylene (11 of 133, 8%) than highly cross-linked polyethylene (1 of 112, 1%; P = .03). Osteolysis was seen in 24% (32 of 133 hips) with standard polyethylene, compared with 13% (15 of 112 hips) with highly cross-linked polyethylene (P = .02). These differences occurred despite the presence of patients with greater BMI and higher activity in the cohort with highly cross-linked polyethylene.

CONCLUSION

We continue to use this acetabular component with highly cross-linked polyethylene. Longer follow-up is required to determine the progression of osteolysis.

Cross-linked versus conventional polyethylene for total knee arthroplasty: a meta-analysis

BACKGROUND

Highly cross-linked polyethylene (HXLPE) has been reported as an effective material for decreasing polyethylene wear and osteolysis in total knee arthroplasty (TKA). Because no single study to date has been large enough to definitively determine the benefit of HXLPE in TKA, we conducted a meta-analysis to pool the results from randomized controlled trials (RCTs) and non-RCTs to make such a determination.

METHODS

Potential candidate articles were identified by searching the Cochrane Library, Medline (1966-2015.10), PubMed (1966-2015.10), Embase (1980-2015.10), ScienceDirect (1985-2015.10), and other databases. "Gray studies" were identified from the included articles' reference lists. Pooled data were analyzed using RevMan 5.1.

RESULTS

Three RCTs and three non-RCTs were included in the meta-analysis. There were no significant differences between the groups in the total number of reoperations (P = 0.11), reoperations for prosthesis loosening (P = 0.08), radiolucent line (P = 0.20), osteolysis (P = 0.38), prosthesis loosening (P = 0.10), and mechanical failures related to the tibial polyethylene (P = 1.00). Similarly, no significant differences between the two groups were found in postoperative total knee score (P = 0.18) or functional score (P = 0.23).

CONCLUSIONS

The meta-analysis showed that compared with conventional polyethylene, HXLPE did not improve the clinical and radiographic outcomes in mid-term follow-up after TKA. Additional high-quality multicenter prospective RCTs with good design, large study populations and long-term follow-up will be necessary to further clarify the effect of HXLPE in TKA.

Wear and Osteolysis of Highly Crosslinked Polyethylene at 10 to 14 Years: The Effect of Femoral Head Size

BACKGROUND

Highly crosslinked polyethylene (XLPE) was introduced to decrease periprosthetic osteolysis related to polyethylene wear, a major reason for revision of total hip arthroplasty. However, there are few reports of wear and osteolysis at 10 years postoperatively.

QUESTIONS/PURPOSES

(1) What are the linear and volumetric wear rates of XLPE at 10 to 14 years? (2) What is the relationship among linear wear, volumetric wear, and femoral head size? (3) What proportion of hips developed osteolysis and was there a relationship between osteolysis and femoral head size or polyethylene wear?

METHODS

We evaluated a previously reported cohort of 84 hips (72 patients) with one design of an uncemented acetabular component and one electron beam 10-kGy irradiated and remelted XLPE at a mean followup of 11 years (range, 10-14 years). The choice of femoral head size was based on several factors, including the outer diameter size of the acetabular component implanted, the perceived risk of dislocation (including the history of alcohol abuse and patient age), and liner availability from the manufacturer. The femoral head sizes used were 26 mm in 10 hips (12%), 28 mm in 31 hips (37%), 32 mm in 31 hips (37%), 36 mm in eight hips (10%), and 40 mm in four hips (5%). Measurements of linear and volumetric wear were performed in one experienced laboratory by the Martell method and analyzed using the first-to-last method. Standard radiographs, with additional Judet views, were used to detect periprosthetic osteolysis. Statistical analysis of wear and osteolysis compared with head size was performed.

RESULTS

For the entire cohort, the median linear wear rate as 0.024 mm/year (95% confidence interval [CI], 0.016-0.030) and the median volumetric wear rate was 12.19 mm(3)/year (95% CI, 6.6-15.7). With the numbers available, we found no association between femoral head size and linear wear rate. However, larger femoral heads were associated with more volumetric wear; 36/40-mm femoral heads had higher volumetric wear (median 26.1; 95% CI, 11.3-47.1) than did 26-mm heads (median 3.1; 95% CI, 0.7-12.3), 28-mm heads (median 12.3; 95% CI, 3.0-19.3), and 32-mm heads (median 12.9; 95% CI, 6.6-16.8; p = 0.02). Small osteolytic lesions were noted in 12 hips (14%), but with the numbers available, there was no association with head size or volumetric wear rates.

CONCLUSIONS

This uncemented acetabular component and this particular XLPE had low rates of linear and volumetric wear. Small osteolytic lesions were noted at 10 to 14 years but were not related to femoral head size or linear or volumetric wear rates. We recommend additional longer-term clinical followup studies and perhaps alternative imaging studies of patients with XLPE and osteolysis.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Comparison of 10-year clinical wear of annealed and remelted highly cross-linked polyethylene: A propensity-matched cohort study

No previous studies comparing the clinical wear rates of the two different kinds of cross-linked ultra-high-molecular-weight polyethylene (XLPE), annealed and remelted, are available. We compared the creep and steady wear rates of 36 matched pairs (72 hips in total) adjusting for baseline characteristics with propensity score matching techniques. Zirconia femoral heads with 26-mm diameter were used in all cases. The femoral-head cup penetration was measured digitally on radiographs. Significantly greater creep (p=0.006) was detected in the remelted (0.234mm) than annealed (0.159mm) XLPE. However, no significant difference (p=0.19) was found between the steady wear rates (0.003 and 0.008mm/year, respectively) of the annealed and remelted XLPE. Multiple regression analyses showed that remelted XLPE is significant independent variable (p<0.001) that is positively associated with creep. However, the patient age and body weight, cup size, the liner thickness, cup inclination, follow-up periods, and postoperative Merle d'Aubigné hip score had no significant effects (p>0.05) on the steady wear rates. No patients exhibited above the osteolysis threshold of 0.1mm/year, progressive radiolucencies, osteolysis, or polyethylene fracture. This　propensity-matched cohort study document no significant difference in wear resistant performances of annealed and remelted XLPE over an average period of 10 years.

In Vivo Oxidative Stability Changes of Highly Cross-Linked Polyethylene Bearings: An Ex Vivo Investigation

The development of highly cross-linked UHMWPEs focused on stabilizing radiation-induced free radicals as the sole precursor to oxidative degradation. However, secondary in vivo oxidation mechanisms have been discovered. After a preliminary post-operative analysis, we subjected highly cross-linked retrievals with 1-4 years in vivo durations and never-implanted controls to accelerated aging to predict the extent to which their oxidative stability was compromised in vivo. Lipid absorption, oxidation, and hydroperoxides were measured using infrared spectroscopy. Gravimetric swelling was used to measure cross-link density. After aging, all retrievals, except vitamin E-stabilized components, regardless of initial lipid levels or oxidation, showed significant oxidative degradation, demonstrated by subsurface oxidative peaks, increased hydroperoxides and decreased cross-link density, compared to their post-operative material properties and never-implanted counterparts, confirming oxidative stability changes.

[Possibilities and limits of modern polyethylenes. With respect to the application profile]

BACKGROUND

Polyethylene is still one of the most important materials in the field of hip and knee arthroplasty. The clinical results of the last decades have helped to further develop polyethylene into a high-tech material. Progress in the development of new materials must be compared with the tried and tested ones to provide optimal and most individual patient care.

OBJECTIVES

This article gives an overview of the history and current application profile of the material ultra-high molecular weight polyethylene (UHMWPE) in hip and knee arthroplasty.

MATERIAL AND METHODS

With the aid of the current literature, new developments in the field of the material UHMWPE, also with respect to the biological activity of wear, the particular biomechanics of the knee joint as well as alternative hard-hard bearing surfaces in the hip, are represented in terms of implant safety.

RESULTS

The problems concerning polyethylene are now well recognized. The disadvantages of the material UHMWPE could be consistently reduced based on material research so that modern polyethylenes have gradually been shown in clinical trials that they can be reliably used.

CONCLUSION

Despite this the potential for improvement has still not yet been fully exploited. Any further development must be extensively tested both biomechanically and biologically before the material can be used in vivo. Long-term results are still necessary before a material can be accepted as being clinically safe.

Highly crosslinked polyethylene improves wear but not surface damage in retrieved acetabular liners

BACKGROUND

Highly crosslinked polyethylene (XLPE) is believed to demonstrate better wear resistance than conventional polyethylene (CPE) in total hip arthroplasty.

QUESTIONS/PURPOSES

The purpose of this study was to compare visual damage scores and micro-CT measurements of penetration, a surrogate for wear, between matched retrieved XLPE and CPE acetabular liners.

METHODS

Thirteen XLPE acetabular liners were matched in terms of implant design (all were of the same design), patient age, sex, liner dimensions, duration of implantation, and reason for revision to a group of CPE liners that were retrieved in the same time period. Penetration resulting from the combination of wear and creep in the two groups of liners was measured with micro-CT. Surface damage was scored by two blinded observers using a surface damage system that considers the seven common damage modes: pitting, scratching, burnishing, abrasions, impingement, embedded debris, and delamination, and wear patterns were documented.

RESULTS

There was no difference (p=0.32) in total damage score between the XLPE group (14±4) and the CPE group (15±5). However, there was three times greater penetration (odds ratio, 3.1; confidence interval, 2.3-5.1; p<0.001) in the CPE group (0.18±0.09 mm/year) than in the XLPE group (0.05±0.07 mm/year). There was less volumetric loss in XLPE (82±SD 134 mm3) versus the CPE group (350±SD 342 mm3; p=0.017).

CONCLUSIONS

XLPE liners undergo less penetration as a result of creep and wear than CPE liners based on quantitative measurements provided by micro-CT, which was not apparent using damage scoring alone. This demonstrates the use of three-dimensional imaging techniques such as micro-CT for quantifying wear in retrieval studies.

CLINICAL RELEVANCE

In this study, XLPE had less wear but similar damage scores than CPE, allaying concerns that the beneficial wear properties of XLPE might come with a tradeoff arising from the increased brittleness of that material.

Vitamin E-diffused highly cross-linked UHMWPE particles induce less osteolysis compared to highly cross-linked virgin UHMWPE particles in vivo

Recent in vitro findings suggest that UHMWPE wear particles containing vitamin E (VE) may have reduced biologic activity and decreased osteolytic potential. We hypothesized that particles from VE-stabilized, radiation cross-linked UHMWPE would cause less osteolysis in a murine calvarial bone model when compared to virgin gamma irradiated cross-linked UHMWPE. Groups received equal amount of particulate debris overlaying the calvarium for 10 days. Calvarial bone was examined using high resolution micro-CT and histomorphometric analyses. There was a statistically significant difference between virgin (12.2%±8%) and VE-UHMWPE (3%±1.4%) groups in regards to bone resorption (P=0.005) and inflammatory fibrous tissue overlaying the calvaria (0.48 vs. 0.20, P<0.0001). These results suggest that VE-UHMWPE particles have reduced osteolytic potential in vivo when compared to virgin UHMWPE.

Polyethylene wear and osteolysis is associated with high revision rate of a small sized porous coated THA in patients with hip dysplasia

The outcome of 25 primary THAs in patients with hip dysplasia using the AML Bantam femoral stem (DePuy) is reported. Age at operation averaged 43 ± 10 years. Twenty-two of 25 stems were cementless. All cementless acetabular components had conventional or cross-linked polyethylene and screws. Follow-up averaged 11 ± 5 years (range 4-18). Four cementless stems were revised after 3, 4, 8, and 9 years; 2/3 cemented stems were revised at 8 and 18 years. Femoral revisions demonstrated extensive conventional polyethylene wear, periprosthetic osteolysis and loosening. Five entire cups were revised for wear and loosening; four liners were replaced. Harris Hip Scores for patients with retained stems went from 43 ± 12 to 85 ± 13. High revision rates with the proximally porous coated Bantam stem are due to loss of fixation, often associated with polyethylene wear and osteolysis.

Biotribology of a vitamin E-stabilized polyethylene for hip arthroplasty - Influence of artificial ageing and third-body particles on wear

The objective of our study was to evaluate the influence of prolonged artificial ageing on oxidation resistance and the subsequent wear behaviour of vitamin E-stabilized, in comparison to standard and highly cross-linked remelted polyethylene (XLPE), and the degradation effect of third-body particles on highly cross-linked remelted polyethylene inlays in total hip arthroplasty. Hip wear simulation was performed with three different polyethylene inlay materials (standard: γ-irradiation 30 kGy, N2; highly cross-linked and remelted: γ-irradiation 75 kGy, EO; highly cross-linked and vitamin E (0.1%) blended: electron beam 80 kGy, EO) machined from GUR 1020 in articulation with ceramic and cobalt-chromium heads. All polyethylene inserts beneath the virgin references were subjected to prolonged artificial ageing (70°C, pure oxygen at 5 bar) with a duration of 2, 4, 5 or 6 weeks. In conclusion, after 2 weeks of artificial ageing, standard polyethylene shows substantially increased wear due to oxidative degradation, whereas highly cross-linked remelted polyethylene has a higher oxidation resistance. However, after enhanced artificial ageing for 5 weeks, remelted XLPE also starts oxidate, in correlation with increased wear. Vitamin E-stabilized polyethylene is effective in preventing oxidation after irradiation cross-linking even under prolonged artificial ageing for up to 6 weeks, resulting in a constant wear behaviour.

Dimensional analysis of total hip arthroplasty polyethylenes

Objective

This paper performs a dimensional analysis of different total hip arthroplasty polyethylenes, cemented and non-cemented, Brazilian made and imported.

Methods

It was considered acetabular components with 50 mm for the 28 mm femoral heads. Dimensional analysis was performed on a 3D coordinate Carl-Zeiss robotic device. Polyethylene thickness and its external measurements (maximum diameter and diameter for the femoral head) were measured.

Results

The minimum thickness of the polyethylene was guaranteed on all tested components. The thickness of cemented acetabular varied from 19.185 mm to 25.358 mm, while the thickness of the non-cemented acetabular varied from 12.451 mm to 19.232 mm. The thickness was 27.96% lower in non-cemented acetabular components. With respect to the polyethylene acetabular cavity that receives the femoral head, all internal diameters exhibit at least 28 mm. In relation to the maximum outer diameter of the polyethylene, only one cemented acetabular component reached 50 mm in diameter.

Conclusions

There are large differences in measurements between brands and models analyzed. Cementless acetabular components have the smaller thickness. The diameters of non-cemented acetabular were also lower than those cemented at the expense of their need to insert into the metal-back.