Objectives. The accuracy and precision of two new methods of model-based radiostereometric analysis (RSA) were hypothesised to be superior to a plain radiograph method in the assessment of polyethylene (PE) wear. Methods. A phantom device was constructed to simulate three-dimensional (3D) PE wear. Images were obtained consecutively for each simulated wear position for each modality. Three commercially available packages were evaluated: model-based RSA using laser-scanned cup models (MB-RSA), model-based RSA using computer-generated elementary geometrical shape models (EGS-RSA), and PolyWare. Precision (95% repeatability limits) and accuracy (Root Mean Square Errors) for two-dimensional (2D) and 3D wear measurements were assessed. Results. The precision for 2D wear measures was 0.078 mm, 0.102 mm, and 0.076 mm for EGS-RSA, MB-RSA, and PolyWare, respectively. For the 3D wear measures the precision was 0.185 mm, 0.189 mm, and 0.244 mm for EGS-RSA, MB-RSA, and PolyWare respectively. Repeatability was similar for all methods within the same dimension, when compared between 2D and 3D (all p > 0.28). For the 2D RSA methods, accuracy was below 0.055 mm and at least 0.335 mm for PolyWare. For 3D measurements, accuracy was 0.1 mm, 0.2 mm, and 0.3 mm for EGS-RSA, MB-RSA and PolyWare respectively. PolyWare was less accurate compared with RSA methods (p = 0.036). No difference was observed between the RSA methods (p = 0.10). Conclusions. For all methods, precision and accuracy were better in 2D, with RSA methods being superior in accuracy. Although less accurate and precise, 3D RSA defines the clinically relevant wear pattern (multidirectional). PolyWare is a good and low-cost alternative to RSA, despite being less accurate and requiring a larger sample size

There is no single standardised method of measuring the orientation of the acetabular component on plain radiographs after total hip arthroplasty. We assessed the reliability and accuracy of three methods of assessing anteversion of the acetabular component for 551 THAs using the PolyWare software and the methods of Liaw et al, and of Woo and Morrey. All measurements of the three methods had excellent intra- and inter-observer reliability. The values of the PolyWare software, which determines version of the acetabular component by edge detection were regarded as the reference standard. Although the PolyWare software and the method of Liaw et al were similarly precise, the method of Woo and Morrey was significantly less accurate (p < 0.001). The method of Liaw et al seemed to be more accurate than that of Woo and Morrey when compared with the measurements using the PolyWare software. If the qualified lateral radiograph was selected, anteversion measured using the method of Woo and Morrey was considered to be relatively reliable. Cite this article: Bone Joint J 2015; 97-B:611–16

Oxidized zirconium (Oxinium) and highly cross-linked polyethylene (HXLPE) were developed with the purpose of minimizing wear, and subsequent osteolysis, in Total Hip Arthroplasty (THA). However, few articles have been published on long-term results of Oxinium on highly cross-linked polyethylene. The purpose of this investigation is to report minimum 10-year HXLPE wear rates and the clinical outcome of patients in this group and compare this population to a control group of cobalt chrome and ceramic. One hundred forty THAs were performed for 123 patients using an Oxinium head with an HXLPE liner. Ninety-seven had 10 years of clinical follow-up (avg. 14.5). Harris Hip Scores (HHS) were collected preoperatively and at the most recent follow-up. Radiographs of 85 hips were available for a minimum 10-year follow-up (avg. 14.5) and used to calculate wear using PolyWare software. Control groups of cobalt chrome and ceramic articulation on HXLPE with a minimum 10-year follow-up were studied. Clinical follow-up of the Oxinium group showed a statistical improvement compared to preoperative and was similar to the control group of patients. Radiographic evaluation found the linear and volumetric wear rates for the Oxinium group of 0.03 mm/year (range 0.00–0.08) and 3.46 mm. 3. /year (range 1.0 to 15.0) respectively. There was no statistically significant difference in linear or volumetric wear rate between the groups (P-value 0.92 and 0.55 respectively). None of these patients underwent revision of their hip for any reason. Oxinium on highly cross-linked polyethylene has performed exceptionally with wear rates comparable to those of cobalt chrome or ceramic on HXLPE

The primary aim of this study was to determine dislocation and revision total hip replacement (THR) up to ten years following primary THR, as well as rates of polyethylene wear, in patients previously enrolled in a randomised controlled trial (RCT) which compared 28 mm and 36 mm metal on highly cross-linked polyethylene (XLPE) articulations. 328 primary THR patients were enrolled in the RCT in Australia. Dislocation was identified from hip instability and hospital visit questionnaires completed by patients or, if they were unable to do so, by their next of kin or primary carer, or General Practitioner. All reported dislocations were confirmed radiographically. Patients' names were cross-matched with the Australian National Joint Replacement Registry to determine whether the index hip had undergone revision THR. Linear wear was measured on plain radiographs using PolyWare (Rev 5, Draftware Developers, Vevay IN, USA). A separate RCT examined the mean proximal wear rate of 28 and 36 mm articulations using radiostereometric analysis (RSA). At 10 years, 110 patients were deceased and 3 patients were lost to follow-up. Overall, dislocation was identified in 8 of 167 (5%) patients with a 28 mm articulation and 2 of 158 (1%) patients with a 36 mm articulation. Three patients experienced recurrent dislocation; all had a 28 mm articulation. 320 (163 28 mm; 157 36 mm) patients were successfully cross-matched with Registry data to identify revision THR. Three patients, all with a 28 mm articulation, underwent revision because of dislocation. Other reasons for revision were infection (1:2), periprosthetic fracture (0:3), loosening/lysis (1:2) and liner fracture (0:1). Adequate radiographs were available to measure wear in 122 hips (67:55) using PolyWare. Excluding bedding in, the mean annual linear wear rate from 1–10 years was 0.04 mm/yr for both 28 and 36 mm articulations (p=0.48). The more sensitive RSA data indicated that at 7 years following primary THR, the mean annual wear rate did not exceed 0.02 mm/yr with either articulation. Up to 10 years following primary THR, 36 mmm articulations were associated with fewer dislocations and revisions for dislocation and did not increase the mean annual linear wear rate

Aims

Oxidized zirconium (OxZi) and highly cross-linked polyethylene (HXLPE) were developed to minimize wear and risk of osteolysis in total hip arthroplasty (THA). However, retrieval studies have shown that scratched femoral heads may lead to runaway wear, and few reports of long-term results have been published. The purpose of this investigation is to report minimum ten-year wear rates and clinical outcomes of THA with OxZi femoral heads on HXLPE, and to compare them with a retrospective control group of cobalt chrome (CoCr) or ceramic heads on HXLPE.

Aims

The aim of this study was to evaluate the performance of first-generation annealed highly cross-linked polyethylene (HXLPE) in cementless total hip arthroplasty (THA).

Introduction. Highly cross-linked polyethylene (HXLPE) was developed to reduce the wear of articular-bearing surfaces in total hip arthroplasty (THA). This study aimed to compare the mean linear wear of HXLPE with a 22.225 mm diameter zirconia head with that of conventional polyethylene (CPE) with a 22.225 mm diameter ortron head. Materials and Methods. A prospective cohort study performed on 93 patients (113 hips) who had undergone primary cemented THAs at our hospital between January 2001 and December 2003. The subject population included 85 females and 8 males with a mean age of 58.0 years (22 to 78) at the time of surgery. The mean follow-up period was 10.2 years (9 to 12). We randomly used two types of implants: the HXLPE cup with a 22.225 mm diameter zirconia head (Kyocera Medical, Osaka, Japan) in 60 hips (HXLPE group), and the CPE cup with a 22.225 mm diameter ortron head (DePuy International, Leeds, UK) in 53 hips (CPE group). Linear wear (penatration) by computer-assisted method with PolyWare software (Draftware Inc, Indiana, USA) was measured at 10 years. Anteroposterior radiographs were evaluated for osteolysis or component loosening defined by the criteria of Hodgkinson et al. Analysis of covariance using the general linear models procedure was carried out to determine the linear wear rate difference between the groups after adjusting for variables (age at surgery, sex, body mass index, vertical distance, horizontal distance, cup inclination, and cup anteversion) as covariates. The differences were considered significant when the p value was <0.05. Results. The mean linear wear rate of HXLPE was 0.043 mm/year, compared with 0.109 mm/year for CPE (p<0.05). The incidence of osteolysis was 1 hip in the CPE group, compared with none in the HXLPE group. No evidence of revision for any reasons was noted. Statistical analysis revealed no significant differences among any variables. Conclusions. Polyethylene wear of HXLPE with a 22.225 mm zirconia head remains significantly lower than that of CPE with a 22.225 mm ortron head at 10 years after operation. HXLPE has a great advantage but careful continued follow-up will be required

Using a larger diameter femoral head in total hip arthroplasty (THA) has advantages in terms of the increased joint stability and range of motion. And the wear resistance of highly cross-linked polyethylene (HXLPE) even combined with a larger head has already been demonstrated by in vitro studies. The purpose of this study was to compare the in vivo wear of Longevity HXLPE sockets against 32 mm and 26 mm heads at a 5-year follow-up. From November 2000 to November 2001, 51 primary cementless THAs were performed with a 26 mm cobalt-chromium head and a Longevity HXLPE socket (Zimmer). A cohort of 32 mm cobalt-chromium heads was comprised of 51 THAs with the same prosthesis performed from December 2001 to December 2003. No significant differences between the groups were observed in gender, age, and BMI, however, polyethylene liners with 32 mm heads were significantly thinner than those with 26 mm heads. Two-dimensional linear wear was measured using PolyWare software on annual x-rays, and total head penetration rates at postoperative 5-year and steady state wear rates were calculated. In addition, periprosthetic osteolysis was evaluated. At the 5-year follow-up, the total head penetration rates were 0.047±0.022 mm/year with 26 mm heads and 0.048±0.026 mm/year with 32 mm heads. The steady state wear rates were −0.008 mm/year with 26 mm heads and 0.001 mm/year with 32 mm heads. No significant differences were seen between the two groups (p=0.82 and p=0.24). Osteolysis was not observed around pros-theses in any hips. At the 5-year follow-up, the wear rate of Longevity HXLPE was very low. A Longevity HXLPE socket will undergo the same level of wear whether with a 32 mm head or a 26 mm head

To assess if highly cross-linked polyethylene is associated with less linear wear than ultra high molecular weight polyethylene in vivo. To assess whether alteration in biomechanical characteristics of the reconstructed hip influence’s wear patterns. A randomised prospective trial comparing conventional polyethylene with highly cross-linked polyethylene in an acetabular component was designed. Identical cemented stems were used in all cases, with a metal head. The polyethylene thickness was controlled. The trial design required 124 cases to be entered to give the study sufficient power to determine any difference in wear rates. Polyware Auto was used to assess 2D wear rate and volume. This paper presents the preliminary results of the early patients entered into the study and looks at both 2D wear or creep at 18 months post operatively, and seeks to establish any relationships between 2D movement and biomechanical characteristics of the reconstructed hip. There was no significant difference in the 2D wear (or creep) between the two types of polyethylene at 18 months. There was no correlation between femoral offset, cup offset, or centre of rotation offset and 2D wear (or creep). This preliminary data shows no difference in the early wear rate of the two types of polyethylene. This is in contrast to an in vitro wear simulator study that has shown more creep in highly cross-linked polyethylene. The significance of this observation is unclear. We hope to demonstrate that as the trial progresses any difference in the performance of the two types of polyethylene should be evident

Introduction: Ultra high molecular weight polyethylene (UHMWPE) wear debris generated at the articulating interface of total hip arthroplasties continues to be the major cause of early failure of these implants. Aim: To validate the accuracy and reproducibility of the three-dimensional technique (3D) of in vivo measurement of UHMWPE wear using PolyWare ™ when applied to digitised radiographs. The aim was to keep the cumulative errors below the accepted annual linear wear rate of 0.15 mm. Method: Using precision phantoms with known cup and head sizes and known deviation simulating wear, series of x-rays were taken simulating a number of variables. These variables were grouped into: patient variables (centering, exposure, motion artefact, prosthesis orientation), image acquisition variables (film and cassette type, x-ray exposure, non-circularity of the projected image, magnification, image sharpness), digitisation variables (input resolution, sharpness), and errors inherent to the PolyWare™ software analytical process. Results: Patient factors contributed the largest errors to the process – these were highly variable. Exposure and input resolution also contributed errors to a lesser extent. No significant error introduction was found with regard to any of the other above-mentioned factors, in particular the PolyWare™ analysis. Conclusions: The three dimensional method (PolyWare™) is accurate and highly reproducible. Apart from patient factors, which directly and indirectly introduce errors, this method is a satisfactory means of estimating the in vivo wear of UHMWPE

The aim was to review patients that had single stage bilateral total hip joint replacements (SSBTHJR) of two surgeons in the Wellington area, to assess symptomatic relief and overall quality of life before and after surgery. To also review xrays of this population to assess acetabular component orientation. Fifty patients from two hospitals, with minimum follow up of two years, who had SSBTHJR, were reviewed for duration of stay, time to mobilisation, and complications (eg. wound infections, venous thrombus and embolism (VTE), gastrointestinal ileus, and cardiac events). Patient opinions on hip joint function (Oxford Hip Score) and overall quality of life (EQ-5D Score) were performed (37/50 patients could participate). Patient’s postoperative radiographs were analysed with Polyware Auto Version 6.00 to measure acetabular cup orientation for both sides. Oxford Hip Score mean was 20.5 (range 12 – 56), compared to the national mean 19.3. The median score was 14. Most patients (65%) had no symptoms of pain, difficulty in mobilising, or performing activities of daily living (ADL). 19% of patients had mild to moderate symptoms/difficulty, and 16% had significant pain/difficulty On average, using a visual analogue scale, patients felt their health was 42% better after having their surgery. Complication rates were minimal, and were primarily superficial wound infections. Hip acetabular cup positioning analysis was performed (statistical analysis pending). Patients undergoing SSBTHJR have comparable results for Oxford Hip Scores compared to unilateral THJR patients, improved lifestyle, but not increased complications

Background. An increasing number of hip prostheses are inserted without bone cement. Experimental research has shown that hydroxyapatite (HA) coated implants are strongly fixated in the bone, which is believed to reduce the likelihood of prosthetic loosening. However, in recent years, there has been much debate about the role of HA particles in third-body polyethylene (PE) wear and formerly we have shown the revision rate to be high among older-design HA coated cups. Purpose. We hypothesized increased PE wear-rate using HA coated acetabular components in comparison with non-HA coated components (control group). Materials and Methods. We performed a retrospective comparative clinical study based on two patient populations identified in the Danish Hip Arthroplasty Registry (October 2006). All patients had primary total hip arthroplasty (THA) between 1997 and 2001 with cementless Mallory-Head acetabular components. One group received HA coated acetabular components (75 patients, 77 hips). The other group received identical components without HA (70 patients, 73 hips). In all cases the liner was similar and 28 mm metal femoral heads were used. All patients were invited for a radiographic follow-up in 2007. The AP radiographs were analysed for two-dimensional (2D) polyethylene wear using the semi-automated PolyWare software. All cases of non-responders, stem revisions, hip dislocations and patients with less than 5 years of follow-up were excluded from the analysis. Findings/Results. The 2D linear PE wear-rate of 0.18 mm/year (SD 0.09) was higher (P<0.001) in the group with HA coated cups (n = 54) compared with 0.12 mm/year (SD 0.07) in the group of non-HA coated cups (n = 35). The Effect size of the difference in linear PE wear-rate, established as Cohen's d, was large (0.9). The time of follow-up was similar (p = 0.11) in the HA group (7.2 years) versus the non-HA group (7.6 years). There was no case-mix concerning distribution of gender and operated side in the groups; however, the mean age was lower (P = 0.001) in the HA group (57 years) compared with the non-HA group (63 years). Conclusions. We found a significantly increased PE wear rate in HA coated acetabular components at midterm follow-up. The patients with HA coated cups were younger on average, and this might partly explain the findings because the activity level expectedly is higher in younger patients. Still an effect size of 0.9 is large and should raise concern and supplement considerations in future clinical decisions on component selection. A randomized (RSA) study on newer type crosslinked polyethylene liners is recommended to bring about more information on the clinical performance and longevity of HA coated acetabular components

INTRODUCTION. Cementless Total Hip Replacement surgery is a well established procedure for relative young patients with severe hip disease. Excellent long term clinical results have been published on the performance of the femoral component. With growing clinical experience, our concern focused on excessive wear of the Ultra High Molecular Weight Polyethylene (UHMWPE) ringloc liner of the Mallory Head cementless Total Hip Prosthesis. After its introduction in our clinic in 1997, this implant is still in use without any modification. We were concerned that due to premature liner wear, the performance of this implant would not be compliant with the international guideline on implant survival (NICE guidelines: at 10 year follow up, 90% of all implants should still be in situ). Our objective was to establish the amount of liner wear in our first 200 MH implants. METHODS. Our first 200 patients consecutively treated with Mallory Head prostheses were followed up to obtain a recent digital image. Follow up was complete for 181 (90.5%) of our 200 patients. Ten had died and nine were not able or willing to come for follow up. The mean duration of follow up was 8.3 years (range: 8–13). The 181 recent digital images were classified as either excessive wear or no excessive wear by two independent orthopedic surgeons. Next, liner wear was measured in the 2D frontal plane using PolyWare Pro/3D Digital Version Rev 5.1 software (Draftware Developers, Conway, USA). A threshold for excessive liner wear was set at 0.2mm/year, according to literature. RESULTS. Using software for measuring PE wear, 46.7% of all patients had excessive UHMWPE wear (> 0.2mm/yr). There was no relation between the amount of wear and BMI, gender, component size or the acetabular inclination angle. Thirteen patients (6.5%) were revised. Nine of these revisions were for excessive liner wear or aseptic loosening (4.5%). For now, our series of cementless Mallory Head prostheses is compliant with the NICE guideline on implant survival. However, with the measured amount of wear we expect to see a significant increase in the number of revisions for liner wear in the near future. DISCUSSION. Our clinical observation of premature UHMWPE wear proved correct. The measured amount of UHMWPE wear is consistent with the few other studies published on this subject. Although we present a retrospective study, limiting the strength of our results, we have included a large group of patients with acceptable loss to follow up. It is unclear if the observed wear will lead to a sharp increase in the number of revisions within the next few years. Possibly, future revisions will be complicated by loss of acetabular bone stock following the pathofysiological reaction to wear particles. Our results can probably be generalised for any district hospital

Aims

Highly cross-linked polyethylene (HXLPE) has greatly improved the durability of total hip arthroplasty (THA) in young patients because of its improved wear characteristics. Few studies have followed this population into the second decade, and therefore the purpose of this investigation was to evaluate the clinical outcome for THA patients 50 years of age and younger at a minimum of 15 years postoperatively. The second purpose was to evaluate the radiological findings secondary to wear or mechanical failure of the implant.

Aims

This paper describes the methodology, validation and reliability of a new computer-assisted method which uses models of the patient’s bones and the components to measure their migration and polyethylene wear from radiographs after total hip arthroplasty (THA).

Aims

We present the ten-year data of a cohort of patients, aged between 18 and 65 years (mean age 52.7 years; 19 to 64), who underwent total hip arthroplasty. Patients were randomised to be treated with a cobalt-chrome (CoCr) femoral head with an ultra-high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (XLPE) or ceramic-on-ceramic (CoC) bearing surface.

Polyethylene wear debris can cause osteolysis and the failure of total hip arthroplasty. We present the five-year wear rates of a highly cross-linked polyethylene (X3) bearing surface when used in conjunction with a 36 mm ceramic femoral head.

This was a prospective study of a cohort of 100 THAs in 93 patients. Pain and activity scores were measured pre- and post-operatively. Femoral head penetration was measured at two months, one year, two years and at five years using validated edge-detecting software (PolyWare Auto).

At a mean of 5.08 years (3.93 to 6.01), 85 hips in 78 patients were available for study. The mean age of these patients was 59.08 years (42 to 73, the mean age of males (n = 34) was 59.15 years, and females (n = 44) was 59.02 years). All patients had significant improvement in their functional scores (p < 0.001). The steady state two-dimensional linear wear rate was 0.109 mm/year. The steady state volumetric wear rate was 29.61 mm³/year. No significant correlation was found between rate of wear and age (p = 0.34), acetabular component size (p = 0.12) or clinical score (p = 0.74).

Our study shows low steady state wear rates at five years in X3 highly cross-linked polyethylene in conjunction with a 36 mm ceramic femoral head. The linear wear rate was almost identical to the osteolysis threshold of 0.1 mm/year recommended in the literature.

Cite this article: Bone Joint J 2015;97-B:1470–4.

We conducted a systematic review and meta-analysis of randomised controlled trials comparing cross-linked with conventional polyethylene liners for total hip replacement in order to determine whether these liners reduce rates of wear, radiological evidence of osteolysis and the need for revision. The MEDLINE, EMBASE and COCHRANE databases were searched from their inception to May 2010 for all trials involving the use of cross-linked polyethylene in total hip replacement. Eligibility for inclusion in the review included the random allocation of treatments, the use of cross-linked and conventional polyethylene, and radiological wear as an outcome measure. The pooled mean differences were calculated for bedding-in, linear wear rate, three-dimensional linear wear rate, volumetric wear rate and total linear wear. Pooled risk ratios were calculated for radiological osteolysis and revision hip replacement. A search of the literature identified 194 potential studies, of which 12 met the inclusion criteria. All reported a significant reduction in radiological wear for cross-linked polyethylene.

The pooled mean differences for linear rate of wear, three-dimensional linear rate of wear, volumetric wear rate and total linear wear were all significantly reduced for cross-linked polyethylene. The risk ratio for radiological osteolysis was 0.40 (95% confidence interval 0.27 to 0.58; I² = 0%), favouring cross-linked polyethylene. The follow-up was not long enough to show a difference in the need for revision surgery.