Polyethylene Acetabular Component Research Articles

IS IT SAFE TO USE A CERAMIC-ON-POLYETHYLENE BEARING IN REVISIONS FOR CERAMIC FRACTURE?

Ceramic bearing fracture is a rare complication following implantation using modern day ceramic bearing materials. Revision bearing options in such cases is debated, with the choice between ceramic-on-ceramic and ceramic-on-polyethylene bearings. Revision to a hard on soft bearing raises concerns about potential catastrophic wear secondary to a third-body reaction caused by the fractured ceramic particles.Data was collected retrospectively from the NJR, electronic patient records, revision database and picture archiving and communication system. Templating software was used to determine linear wear between first post-operative radiograph and the latest available follow up. Univariate analysis was used to examine patient demographics and the wear rates for revision of ceramic bearing fractures to ceramic on polyethylene components. The intra and inter-rater reliability of wear measurements was calculated.There were twelve patients identified as meeting the inclusion criteria. The average age at revision was 62 years (54–72). There were 6 liner and 6 head fractures revised to delta ceramic heads and cross-linked polyethylene acetabular components. The most frequently used head size was 32mm. At mean follow up of 3.8 years (0.5 6.1 years), median 4.4 years, linear wear rate was calculated at 0.08± 0.06 mm/year. Both intra-rater and inter-rater reliability was excellent with ICC scores of 0.99 at all timepoints.Revision to ceramic on polyethylene (CoP) bearings following ceramic fracture does not cause early catastrophic wear at early follow up. It appears safe to use this hard on soft bearing combination, given that wear rates are comparable to what is expected in a primary hip replacement setting. Longer follow up is required to establish if this trend persists.

Large articulations do not increase wear rates of thin second-generation highly cross-linked polyethylene liners at ten years.

Radiostereometric analysis (RSA) is the most accurate radiological method to measure in vivo wear of highly cross-linked polyethylene (XLPE) acetabular components. We have previously reported very low wear rates for a sequentially irradiated and annealed X3 XLPE liner (Stryker Orthopaedics, USA) when used in conjunction with a 32 mm femoral heads at ten-year follow-up. Only two studies have reported the long-term wear rate of X3 liners used in conjunction with larger heads using plain radiographs which have poor sensitivity. The aim of this study was to measure the ten-year wear of thin X3 XLPE liners against larger 36 or 40 mm articulations with RSA. We prospectively reviewed 19 patients who underwent primary cementless THA with the XLPE acetabular liner (X3) and a 36 or 40 mm femoral head with a resultant liner thickness of at least 5.8 mm. RSA radiographs at one week, six months, and one, two, five, and ten years postoperatively and femoral head penetration within the acetabular component were measured with UmRSA software. Of the initial 19 patients, 12 were available at the ten-year time point. The median proximal, 2D, and 3D wear rates calculated between one and ten years were all less than 0.005 mm/year, with no patient recording a proximal wear rate of more than 0.021 mm/year. Importantly, there was no increase in the wear rate between five and ten years. The very low wear rate of X3 XLPE liners with larger articulations remains encouraging for the future clinical performance of this material.

Analysis of the Risk of Wear on Cemented and Uncemented Polyethylene Liners According to Different Variables in Hip Arthroplasty

Wear debris in total hip arthroplasty is one of the main causes of loosening and failure, and the optimal acetabular fixation for primary total hip arthroplasty is still controversial because there is no significant difference between cemented and uncemented types for long-term clinical and functional outcome. To assess and predict, from a theoretical viewpoint, the risk of wear with two types of polyethylene liners, cemented and uncemented, a simulation using the finite element (FE) method was carried out. The risk of wear was analyzed according to different variables: the polyethylene acetabular component’s position with respect to the center of rotation of the hip; the thickness of the polyethylene insert; the material of the femoral head; and the relationship of the cervical–diaphyseal morphology of the proximal end of the femur to the restoration of the femoral offset. In all 72 simulations studied, a difference was observed in favour of a cemented solution with respect to the risk of wear. With regard to the other variables, the acetabular fixation, the thickness of the polyethylene, and the acetabular component positioning were statistically significant. The highest values for the risk of wear corresponded to a smaller thickness (5.3 mm), and super-lateral positioning at 25 mm reached the highest value of the von Mises stress. According to our results, for the reconstruction of the acetabular side, a cemented insert with a thickness of at least 5 mm should be used at the center of rotation.

Multi-body dynamic model of subject specific knee: Utilization of mri images for reconstruction of contact bodies and insertion sites

The aim of the study is to determine failure of the cemented polyethylene acetabular component, which might occur due to excessive bone resorption, cement–bone interface debonding and fatigue failure of the cement mantle. Three-dimensional finite element models of intact and implanted pelvic bone were developed and bone remodeling algorithm was implemented for present analysis. Soderberg fatigue failure diagram was used for fatigue assessment of the cement mantle. Hoffman failure criterion was considered for prediction of cement–bone interface debonding. Results indicate fatigue failure of the cement mantle and implant–bone interface debonding might not occur due to bone remodeling.

The ethylene oxide sterilised Opera acetabular component demonstrates high rates of loosening and revision compared to the gamma irradiated Ogee cup: a cohort study demonstrating potential shortcomings of revision-based registry data.

To evaluate the long-term clinical outcomes of 2 cemented ultra-high molecular weight polyethylene (UHMWPE) acetabular components, with the main difference between the 2 components being their method of sterilisation. Data was collected prospectively on 352 consecutive total hip replacements, performed between March 2000 and July 2004, at a single centre. A posterior approach was used with a cemented C-Stem femoral component (DePuy, Warsaw, IN, USA) in all cases and either the Ogee (DePuy, Warsaw, IN, USA) or the Opera (Smith & Nephew, Memphis, TN, USA) acetabular implant. Patients were reviewed clinically and radiologically with a median 12-year follow-up (6-16 years). The risk of experiencing loosening was 90% lower for the Gamma irradiated implant (GII) group compared to the ethylene oxide sterilised implant (EOSI) group, which was statistically significant (p = 0.003), (HR 0.10; 95% CI, 0.02-0.45). The incidence of cup revision was also lower in the GII group (p = 0.029), but after adjustment for age, gender and BMI was not statistically significant (p = 0.104). 15-year survivorship with failure/loosening as an endpoint was 70.1% for the EOS implant and 92.9% for the GII (OR 4.99; CI 95%, 1.75-14.2) and with revision as an endpoint was 81.4% for the EOSI and 92.9% for the GII (OR 2.60; CI 95%, 0.87-7.75). We report increased rates of loosening, revision and failure for the EOSI compared to the GII at long-term follow-up. This may have been attributable to the different sterilisation methods used.

Anatomical pelvic loading of a monoblock polyethylene acetabular component.

Uncemented metal acetabular components show good osseointegration, but material stiffness causes stress shielding and retroacetabular bone loss. Cemented monoblock polyethylene components load more physiologically; however, the cement bone interface can suffer fibrous encapsulation and loosening. It was hypothesized that an uncemented titanium-sintered monoblock polyethylene component may offer the optimum combination of osseointegration and anatomical loading. A total of 38 patients were prospectively enrolled and received an uncemented monoblock polyethylene acetabular (pressfit) component. This single cohort was then retrospectively compared with previously reported randomized cohorts of cemented monoblock (cemented) and trabecular metal (trabecular) acetabular implants. The primary outcome measure was periprosthetic bone density using dual-energy x-ray absorptiometry over two years. Secondary outcomes included radiological and clinical analysis. Although there were differences in the number of males and females in each group, no significant sex bias was noted (p = 0.080). Furthermore, there was no significant difference in age (p = 0.910) or baseline lumbar bone mineral density (BMD) (p = 0.998) found between any of the groups (pressfit, cemented, or trabecular). The pressfit implant initially behaved like the trabecular component with an immediate fall in BMD in the inferior and medial regions, with preserved BMD laterally, suggesting lateral rim loading. However, the pressfit component subsequently showed a reversal in BMD medially with recovery back towards baseline, and a continued rise in lateral BMD. This would suggest that the pressfit component begins to reload the medial bone over time, more akin to the cemented component. Analysis of postoperative radiographs revealed no pressfit component subsidence or movement up to two years postoperatively (100% interobserver reliability). Medial defects seen immediately postoperatively in five cases had completely resolved by two years in four patients. Initially, the uncemented monoblock component behaved similarly to the rigid trabecular metal component with lateral rim loading; however, over two years this changed to more closely resemble the loading pattern of a cemented polyethylene component with increasing medial pelvic loading. This indicates that the uncemented monoblock acetabular component may result in optimized fixation and preservation of retroacetabular bone stock. Cite this article: Bone Joint J2021;103-B(5):872-880.

Hip Replacement or Hip Resurfacing with a Highly Cross-Linked Polyethylene Acetabular Bearing

Background:Most surgeons strongly prefer total hip arthroplasty (THA) over hip resurfacing arthroplasty (HRA). However, it is unknown whether patients prefer the results of 1 procedure over the other. The purpose of this study was to answer 3 questions: (1) Do patients with an HRA on 1 side and a THA on the other notice a difference? (2) Do patients have a preference? (3) What are the reasons for their preference?Methods:Between 1998 and 2012, 332 patients underwent staged bilateral hip arthroplasties with cementless THA on 1 side and HRA on the other, with a highly cross-linked polyethylene acetabular component used for both. Patient preferences, Harris hip scores, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were recorded by blinded examiners. Patients provided reasons for their preference in semi-structured interviews using both quantitative and qualitative measures.Results:The mean follow-up was 11 years (range, 7 to 21 years). Of 324 patients with complete data, 279 (86%) preferred the HRA, 19 (6%) preferred the THA, and 26 (8%) had no preference. The most common reasons for preference for the HRA were better balance (n = 143), felt more normal (n = 141), better activity participation/more reliable hip during sports (n = 139), and stronger on stairs (n = 129). A fair or poor outcome was reported by the patient after 4 HRAs and 7 THAs. The remainder of the patients reported improved function and satisfactory pain relief and range of motion for both hips.Conclusions:In conclusion, most patients in this study preferred the side on which the HRA had been done. Since essentially all current hip prostheses perform well, a paired bilateral study may be the optimal way to determine patient preferences and values of HRA compared with THA.Level of Evidence:Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Deformation and Recovery of Thin Metal-Backed, Two-Piece Polyethylene Acetabular Resurfacing Components.

Acetabular underreaming is a bone preservation and fixation strategy in hip resurfacing. Prior reports of acetabular component deformation have been cadaveric studies. In this study, I sought to determine deformation of thin shells and very thin highly cross-linked polyethylene in patients, the effects of increasing underreaming and liner-head clearance, and whether deformation accelerates wear. Overall, 32 two-piece metal-backed polyethylene resurfacing acetabular components placed with 3-4 mm of underreaming were retrieved postmortem or during revision after a mean of 9 years of patient use. Shells were 54-64 mm in external diameter. The components were 2-mm-thick porous-coated shells and 4-mm highly cross-linked polyethylene liners. Deformation was measured during insertion, 30 minutes after implantation, after reducing the hip and testing range of motion, and at retrieval. Standard liner-head clearance was 0.3 mm, and clearances up to 2.8 mm were also used. Acetabular shells deformed a mean of 0.58 mm on insertion and deformed 0.23 mm at retrieval. Initial liner deformation of 0.29 mm decreased to 0.15 mm on retrieval. With liner-head clearance of 2.8 mm, the mean shell and liner deformations at retrieval were 0.36 mm and 0.29 mm, respectively. The calculated insertional force was 367 Nm. No acetabular fractures, shell or liner failures, or adverse clinical consequences were observed. Mean linear wear was 0.005 mm/yr. Thin resurfacing acetabular shells and liners deform when placed with 3-4 mm of underreaming, which lessens with loading, bone relaxation, and clinical use. Bone preservation by underreaming is beneficial during hip resurfacing surgery.

Intra-articular hip spacers for infection: Fabrication and use

The rate of periprosthetic joint infections (PJI) after primary total hip arthroplasty is between 0.5% and 2% in most series. In North America, the gold standard for chronic PJI continues to be a two-stage exchange. Hip spacers are broadly classified as being articulating or non-articulating; prefabricated or fabricated intraoperatively (handmade custom spacers); hemi-arthroplasty or used in conjunction with a cemented polyethylene acetabular component. There are a multitude of hip spacers to choose from, there has been a trend towards using an antibiotic coated prosthesis (ACP). In this review, we will discuss the fabrication, usage as well as advantages and disadvantages of currently available hip spacers.

Polyethylene Hip Resurfacing to Treat Arthritis and Severe Acetabular Insufficiency

BackgroundHip dysplasia is the leading cause of hip arthritis in young adults. These patients often participate in active lifestyles that require a full and stable range of motion. MethodsBetween 2001 and 2011, 232 consecutive polyethylene resurfacing arthroplasties were performed in 201 patients with advanced arthritis from severe acetabular insufficiency due to dysplasia. All patients had Crowe II or III disease. Their mean age at surgery was 43 years. A 2-piece cementless acetabular resurfacing shell with dome screws and a highly cross-linked polyethylene liner were implanted to provide secure fixation, early weight bearing, and a stable hip. Additional structural bone grafts and/or fixation were not used. A cemented or cementless resurfacing prosthesis was used on the femur. ResultsDuring a mean follow-up of 10 years, 8 hips (3.5%) were converted to a total hip arthroplasty due to acetabular loosening (1), femoral neck fracture (2), femoral osteonecrosis (2), infection (2), or persistent pain (1), resulting in a mean survival of the resurfacing prostheses of 96% (95% confidence interval 89-98). There were no pending revisions and no dislocations. At 2 years postoperative, Harris Hip Scores improved from a preoperative mean of 55 to 97 and University of California Los Angeles activity scores improved from 5 to 8. ConclusionHip resurfacing using a 2-piece polyethylene acetabular component for advanced dysplasia has resulted in excellent function and implant survivorship with a low rate of complications at mid-term follow-up.

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

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. 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. 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. 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.

Vitamin E-stabilized highly crosslinked polyethylenes: The role and effectiveness in total hip arthroplasty.

Morphology and design of ultra-high molecular weight polyethylene (UHMWPE or simply PE) acetabular components used in total hip arthroplasty (THA) have been evolving for more than half a century. Since the late-1990s, there were two major technological innovations in PE emerged from necessity to overcome the wear-induced periprosthetic osteolysis, i.e., the development of highly crosslinked PEs (HXLPEs). There are many literaturereporting that radiation crosslinked and remelted/annealed (first-generation) HXLPEs markedly reduced the incidence of osteolysis and aseptic loosening. Regardless of such clinical success in the first-generation technologies, there were some recent shifts in Japan toward the use of new second-generation HXLPEs subjected to sequential irradiation/annealing or antioxidant vitamin E (α-tocopherol) incorporation. Although the selection rate of first-generation liners still account for more than half of all the PE THAs (∼58% in 2015), the use of vitamin E-stabilized liners has been steadily growing each year since their clinical introduction in 2010. In these contexts, it is of great importance to evaluate and understand the real clinical benefits of using the new second-generation liners as compared to the first generation. This article first summarizes structural evolution and characteristic features of first-generation HXLPEs, and then provides a detailed description of second-generation antioxidant HXLPEs in regard to the role of vitamin E incorporation on their chemical and mechanical performances in THA.

Reconstruction of non-contained acetabular defects with impaction grafting, a reinforcement mesh and a cemented polyethylene acetabular component

This review summarises the technique of impaction grafting with mesh augmentation for the treatment of uncontained acetabular defects in revision hip arthroplasty. The ideal acetabular revision should restore bone stock, use a small socket in the near-anatomic position, and provide durable fixation. Impaction bone grafting, which has been in use for over 40 years, offers the ability to achieve these goals in uncontained defects. The precepts of modern, revision impaction grafting are that the segmental or cavitary defects must be supported with a mesh; the contained cavity is filled with vigorously impacted morselised fresh-frozen allograft; and finally, acrylic cement is used to stabilise the graft and provide rigid, long-lasting fixation of the revised acetabular component. Favourable results have been published with this technique. While having its limitations, it is a viable option to address large acetabular defects in revision arthroplasty. Cite this article: Bone Joint J 2017;99-B(1 Supple A):25-30.

Evaluating hip implant wear measurements by CMM technique

Wear of the bearing components is a major factor affecting the performance of hip implants. Wear analysis is thus one of the most important processes for understanding of how wear occurs and its location and development, with an aim to improve the success rate and longevity of total hip replacements. This study presents wear measurement and analysis of polyethylene acetabular components using a coordinate measuring machine (CMM). An uncertainty analysis was performed to validate CMM wear measurements. Measurements were made with an increasing number of scanning points on retrieved ex vivo implants to investigate the effect of the number of scanning points on wear measurements. CMM wear measurements were compared to in vivo radiographic measurements (RSA) and volumetric wear estimates made using well-established analytical formulae. The number of scanning points has insignificant effect on wear quantity and measurement uncertainty. CMM linear wear measurements closely match those made using RSA, whereas theoretical volumetric formulae applied to CMM and RSA measurements both appear to overestimate wear volume. The findings further emphasize potential benefit of using CMM ex vivo and RSA in vivo to assess polyethylene wear after total hip replacement surgery. Further, it is shown that identifying key components of the measurement uncertainty are important to improve the accuracy and the reliability of CMM wear measurement.

A pilot trial comparing the tear-out behavior in screw-sockets and cemented polyethylene acetabular components – a cadaveric study

BackgroundThe removal of well-fixed acetabular components following THA (total hip arthroplasty) is a difficult operation and could be accompanied by the loss of acetabular bone stock. The optimal method for fixation is still under debate. The aim of this pilot study was to compare the tear-out resistance and failure behavior between osseo-integrated and non-integrated screw cups. Furthermore, we examined whether there are differences in the properties mentioned between screw sockets and cemented polyethylene cups. HypothesisTear-out resistance and related mechanical work required for the tear-out of osseo-integrated screw sockets are higher than in non-integrated screw sockets. Patients and methodsTen human coxal bones from six cadavers with osseo-integrated screw sockets (n=4), non-integrated (implanted post-mortem, n=3) screw sockets and cemented polyethylene cups (n=3) were used for tear-out testing. The parameters axial failure load and mechanical work for tear-out were introduced as measures for determining the stability of acetabular components following THA. ResultsThe osseo-integrated screw sockets yielded slightly higher tear-out resistance (1.61±0.26kN) and related mechanical work compared to the non-integrated screw sockets (1.23±0.39kN, P=0.4). The cemented polyethylene cups yielded the lowest tear-out resistance with a failure load of 1.18±0.24kN. Compared to the screw cups implanted while alive, they also differ on a non-significant level (P=0.1). Osseous failure patterns differed especially for the screw sockets compared to the cemented polyethylene cups. DiscussionOsseo-integration did not greatly influence the tear-out stability in cementless screw sockets following axial loading. Furthermore, the strength of the bone-implant-interface of cementless screw sockets appears to be similar to cemented polyethylene cups. However, given the high failure load, high mechanical load and because of the related bone failure patterns, removal should not be performed by means of tear-out but rather by osteotomes or other curved cutting devices to preserve the acetabular bone stock. Level of evidenceLevel III, case-control-study.

Post-deformation shape-recovery behavior of vitamin E-diffused, radiation crosslinked polyethylene acetabular components

The in-vivo progression of creep and wear in ultra-high molecular weight polyethylene (UHMWPE) acetabular liners has been clinically evaluated by measuring radiographic penetration of femoral heads. In such clinical assessments, however, viscoelastic strain relaxation has been rarely considered after a removal of hip joint loading, potentially leading to an underestimation of the penetrated thickness. The objective of this study was to investigate shape-recovery behavior of pre-compressed, radiation crosslinked and antioxidant vitamin E-diffused UHMWPE acetabular liners, and also to characterize the effects of varying their internal diameter (ID) and wall thickness (WT). We applied uniaxial compression to the UHMWPE specimens of various ID (28, 32, 36mm) and WT (4.8, 6.8, 8.9mm) for 4320min under the constant load of 3000N, and subsequently monitored the strain-relaxation behavior as a function of time after unloading. It was observed that there was a considerable shape recovery of the components after removal of the external static load. Reducing ID and WT significantly accelerated the rate of creep strain recovery, and varying WT was more sensitive to the recovery behavior than ID. Creep deformation of the tested liners recovered mostly within the first 300min after unloading. Note that approximately half of the total recovery amount proceeded just within 5min after unloading. These results suggest a remarkably high capability of shape recovery of vitamin E-diffused highly crosslinked UHMWPE. In conclusion, the time-dependent shape recovering and the diameter-thickness effect on its behavior should be carefully considered when the postoperative penetration is quantified in highly crosslinked UHMWPE acetabular liners (especially on the non-weight bearing radiographs).

Assessment of failure of cemented polyethylene acetabular component due to bone remodeling: A finite element study

The aim of the study is to determine failure of the cemented polyethylene acetabular component, which might occur due to excessive bone resorption, cement–bone interface debonding and fatigue failure of the cement mantle. Three-dimensional finite element models of intact and implanted pelvic bone were developed and bone remodeling algorithm was implemented for present analysis. Soderberg fatigue failure diagram was used for fatigue assessment of the cement mantle. Hoffman failure criterion was considered for prediction of cement–bone interface debonding. Results indicate fatigue failure of the cement mantle and implant–bone interface debonding might not occur due to bone remodeling.

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

BackgroundHip 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. MethodsIn 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. ResultsThe 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 cm3 on computed tomography and no instances of impending polyethylene wear-through. Seven polyethylene retrievals had a measured wear rate of 0.05 mm/y. ConclusionHip 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.

Wear of highly crosslinked polyethylene acetabular components

Background and purpose — Wear rates of highly crosslinked polyethylene (XLPE) acetabular components have varied considerably between different published studies. This variation is in part due to the different techniques used to measure wear and to the errors inherent in measuring the relatively low amounts of wear in XLPE bearings. We undertook a scoping review of studies that have examined the in vivo wear of XLPE acetabular components using the most sensitive method available, radiostereometric analysis (RSA).Methods — A systematic search of the PubMed, Scopus, and Cochrane databases was performed to identify published studies in which RSA was used to measure wear of XLPE components in primary total hip arthroplasty (THA).Results — 18 publications examined 12 primary THA cohorts, comprising only 260 THAs at 2–10 years of follow-up. The mean or median proximal wear rate reported ranged from 0.00 to 0.06 mm/year. However, differences in the manner in which wear was determined made it difficult to compare some studies. Furthermore, differences in RSA methodology between studies, such as the use of supine or standing radiographs and the use of beaded or unbeaded reference segments, may limit future meta-analyses examining the effect of patient and implant variables on wear rates.Interpretation — This scoping review confirmed the low wear rates of XLPE in THA, as measured by RSA. We make recommendations to enhance the standardization of reporting of RSA wear results, which will facilitate early identification of poorly performing implants and enable a better understanding of the effects of surgical and patient factors on wear.

A patterned microtexture to reduce friction and increase longevity of prosthetic hip joints

More than 285,000 total hip replacement surgeries are performed in the US each year. Most prosthetic hip joints consist of a cobalt–chromium (CoCr) femoral head that articulates with a polyethylene acetabular component, lubricated with synovial fluid. The statistical survivorship of these metal-on-polyethylene prosthetic hip joints declines significantly after 10–15 years of use, primarily as a result of polyethylene wear and wear debris incited disease. The current engineering paradigm to increase the longevity of prosthetic hip joints is to improve the mechanical properties of the polyethylene component, and to manufacture ultra-smooth articulating surfaces. In contrast, we show that adding a patterned microtexture to the ultra-smooth CoCr femoral head reduces friction when articulating with the polyethylene acetabular liner. The microtexture increases the load-carrying capacity and the thickness of the joint lubricant film, which reduces contact between the articulating surfaces. As a result, friction and wear is reduced. We have used a lubrication model to design the geometry of the patterned microtexture, and experimentally demonstrate reduced friction for the microtextured compared to conventional smooth surrogate prosthetic hip joints.