Bearing Surface Wear Research Articles

Fracture of femoral neck in modular total hip arthroplasty: a systematic review of the literature.

Modular femoral stems have the advantage of anatomic hip reconstruction by restoring the femoral offset thus minimising the bearing surface wear, implant loosening and dislocation. This study aims to investigate the existing literature on modular neck fractures, to identify predisposing factors and guide the decision-making process in the management of these difficult cases. A systematic literature review was conducted until July 2022. PRISMA guidelines were followed, eligibility criteria were set, and methodology assessment of included studies was conducted based on MINORS criteria, size and primary outcome. Data were extracted and analysed thoroughly. 5657 studies were initially screened; the full texts of 124 records were assessed and finally, 32 reports were included. There were 7 clinical studies and 25 case reports. A total of 4825 patients (5204 hips) with a mean age 62.38 years and a mean BMI 29.06 kg/m2 were analysed in the 7 clinical studies. The reported overall weighted revision rate was 0.86%, while the weighted mean modular neck fracture rate was 0.26%. The usual history was sudden experience of hip pain and instability. The average time interval to neck fracture was 4.57 (range 3-4.7) years and a long modular neck was identified in 91.17% of them. Data from case reports showed a mean age and average BMI of 55.85 and 31.63 kg/m2. 82.35% of the patients were male. Necks were fractured after an average time interval of 64.5 ± 8.8 months. The incidence of modular neck fracture is significant. The profile of a male, obese patient with a long modular neck increased risk of neck fracture. Microstructural investigation of the retrieved implants demonstrated a higher incidence of fracture line in the base of the neck junction and at its anterolateral distal part. Surgeons should be aware of this complication while using or revising such protheses.

Cannabis use disorder is not a risk factor for thrombotic events or medical complications following total shoulder arthroplasty

BackgroundIn recent years, there has been an increase in utilization of cannabis. Existing studies have found cannabis use disorder (CUD) to be associated with increased incidence of perioperative complications in lower extremity arthroplasty. However, studies examining CUD following total shoulder arthroplasty (TSA) are limited. The aim of this study was to evaluate the effect of comorbid CUD on 2-year revision and 90-day postoperative outcomes in primary TSA for osteoarthritis. MethodsA retrospective cohort analysis was conducted using the PearlDiver database. Current Procedural Terminology, ICD-9, and ICD-10 codes were used to identify patients undergoing TSA for the indication of osteoarthritis and were divided into a CUD and control group. The primary outcomes of interest were 2-year all-cause revision, 90-day hospital readmission, and 90-day emergency department (ED) visit. Surgical perioperative complications included prosthetic joint infection, periprosthetic fracture, aseptic loosening, articular bearing surface wear, broken prosthesis, and prosthetic dislocation. Univariate analysis and multivariable logistic regression were conducted to analyze the data. ResultsA total of 205,792 patients undergoing TSA were identified. The CUD cohort contained 2058 patients, and the control cohort contained 203,734 patients. After controlling for comorbidities, there were statistically significant differences in 2-year revision outcomes. Multivariable results also showed no association with 90-day medical or surgical complications, with the exception of convulsions, 90-day presentation to an eED, and readmission. Discussion and ConclusionOur study showed that patients with CUD have an increased risk of 2-year all-cause revision, readmission, and ED presentation after undergoing TSA. However, CUD was not found to be an independent risk factor for adverse 90-day medical complications, deep vein thrombosis, or length of stay. The results of this research expand the literature on TSA and comorbid substance use. Further, our findings can assist orthopedic surgeons in counseling patients regarding CUD as a risk factor for complications of TSA.

Design and Optimization of the Surface Texture at the Hydrostatic Bearing and the Spindle for High Precision Machining

Hydrostatic bearing spindles are widely applied in high precision grinding and turning machines due to their good dynamic stability and rotational accuracy. However, under the condition of high-speed rotations, the heat generated by the friction of the oil film will cause the shear thinning effect. It not only reduces the rotation accuracy of the spindle but also reduces the service life of the spindle. The surface texture structure and configuration between the planes play the role of homogenizing oil film temperature and preventing the bearing surface wear caused by excessive concentration of temperature, which can change the relative motion from the inside of the oil film and thus improve the performance of the hydrostatic spindle more effectively. In this paper, the influence of the surface texture shape and height on the thrust bearing performance of the hydrostatic spindle is systematically investigated by comparative analysis. The CFD simulations are developed to analyze the computational results based on the theory of viscosity-temperature characteristics. The results show that when the height of the surface structure is 1 ~ 2 times the oil film thickness, the spindle bearing performance is the best. The average temperature in the bearing region is the lowest and the accuracy of the simulations was verified by experimental results.

Articular geometry can affect joint kinematics, contact mechanics, and implant-bone micromotion in total ankle arthroplasty.

Implant loosening and bearing surface wear remain the most common failure problems of total ankle arthroplasty (TAA). One of the main factors leading to these problems is the nonphysiologic design of articular surfaces. The goals of this study were to reveal the effects of the anatomical medial-lateral borders height differences, coronal and sagittal radii on the joint kinematics, contact mechanics, and implant-bone micromotion in TAA. A previously developed and validated musculoskeletal (MSK) multibody dynamics (MBD) modeling method of TAA based on AnyBody generic MSK MBD model (five simulations for each implant) was used by combining with a finite element analysis. Five ankle implant models with different articular surface morphologies were created according to the anatomic characteristics of Chinese measurement data, marked as Implant A to E. The total ankle forces and motions during walking simulation were predicted by MSK MBD models and the contact mechanics of the bearing surface and the micromotion of the implant-bone interface of TAA were predicted by FE models. Compared with Implant A, the internal-external rotation in Implant E increased by 12.14%, the maximum of anterior-posterior translation in Implant E increased by 5.62%, the maximum reduction of tibial micromotion in Implant E was 59.98%, and for talar, micromotion was 15.36%. The ankle implant with similar anatomic articular surface has the potential to allow patients to recover better motions and reduce the risk of early loosening. This study would provide design guidance for the development of new ankle implants and further advance the development of TAA. Clinical Significance: This study promoted the improvement of ankle implant design and made contributions to improve the service life of ankle implant and patient satisfaction.

Synchronized acoustic emission and gait analysis of total hip replacement patients

ObjectiveIncreased numbers of joint replacement patients suffering implant wear and/or loosening has created a need for development of non-invasive early diagnosis techniques. Acoustic emission monitoring has shown diagnostic potential for joint replacements, but has not previously been linked to temporal stages of the gait cycle, biomechanical modelling, and hip flexion angles. This combination of acoustic and biomechanics parameters is the novel contribution of this manuscript. MethodsTotal hip replacement acoustic emissions are synchronized with gait data using three-dimensional video motion capture from total hip replacement patients. Hip joint motions are estimated from the motion data, using OpenSim musculoskeletal modelling software, synchronized in time with the recorded acoustic emission data. ResultsSubstantial acoustic emissions have been observed occurring only during the stance phase of the gait cycle in two of three patients. Repeated audible squeaking was observed from one patient during terminal stance. Squeaking was observed to occur from approximately 5°-15° hip extension when high joint loading and rapid changes in hip angle were occurring. These are also the likely conditions of the largest implant bearing surface wear rates. ConclusionSpecific regions within the gait cycle that peak acoustic emission signals occur are identified, providing insight into underlying biomechanics. High implant load and high angular velocity during the stance phase are correlated with peak acoustic emissions. SignificanceThis is one of the first studies to relate recorded in-vivo human implant acoustic emissions with lower-limb biomechanical modelling, providing new insight into in-vivo total hip replacement implant mechanics. Further research is needed to increase patient numbers and verify if these results apply more broadly to a wider cohort.

The in vivo location of edge-wear in hip arthroplasties : combining pre-revision 3D CT imaging with retrieval analysis.

AimsAcetabular edge-loading was a cause of increased wear rates in metal-on-metal hip arthroplasties, ultimately contributing to their failure. Although such wear patterns have been regularly reported in retrieval analyses, this study aimed to determine their in vivo location and investigate their relationship with acetabular component positioning.Methods3D CT imaging was combined with a recently validated method of mapping bearing surface wear in retrieved hip implants. The asymmetrical stabilizing fins of Birmingham hip replacements (BHRs) allowed the co-registration of their acetabular wear maps and their computational models, segmented from CT scans. The in vivo location of edge-wear was measured within a standardized coordinate system, defined using the anterior pelvic plane.ResultsEdge-wear was found predominantly along the superior acetabular edge in all cases, while its median location was 8° (interquartile range (IQR) -59° to 25°) within the anterosuperior quadrant. The deepest point of these scars had a median location of 16° (IQR -58° to 26°), which was statistically comparable to their centres (p = 0.496). Edge-wear was in closer proximity to the superior apex of the cups with greater angles of acetabular inclination, while a greater degree of anteversion influenced a more anteriorly centred scar.ConclusionThe anterosuperior location of edge-wear was comparable to the degradation patterns observed in acetabular cartilage, supporting previous findings that hip joint forces are directed anteriorly during a greater portion of walking gait. The further application of this novel method could improve the current definition of optimal and safe acetabular component positioning.Cite this article: Bone Joint Res 2021;10(10):639–649.

Computational method for bearing surface wear prediction in total hip replacements

Total hip replacement (THR) is a revolutionary treatment when a hip joint becomes severely damaged. Wear is known as one of the main reasons for THR failure. Current experimental techniques to investigate the wear at the bearing surfaces of THRs are time-consuming, complicated and expensive. In this study, an in-house fretting wear algorithm has been further developed to investigate the wear damage that occurs on bearing surfaces of THRs and its consequence on the longevity of the implants. A 3D finite element model has been created with a 36 mm diameter Cobalt–Chromium femoral head and a 4 mm thick cross-linked polyethylene bearing liner. A gait loading cycle was used to simulate walking for up to 5 million cycles (Mc). The wear algorithm extracts relative displacements and contact shear stresses from the finite element package to predict the linear and volumetric wear rates. This method is shown to have modelled the evolution of wear effectively and found it to be similar to those from experimental analyses. The linear and volumetric wear per million cycles predicted in this study were 0.0375mm/Mc and 33.6mm3/Mc which are comparable to those measured in-vivo THRs. The wear patterns obtained from this study are also comparable to the wear patterns shown on available conventional polyethylene liners. This method can be used to further aid in the design and clinical technique to reduce wear rate in THRs.

Metal-on-metal total hip arthroplasty: does increasing modularity affect clinical outcome?

Modularity of metal-on-metal (MoM) implants has come under scrutiny due to concerns regarding additional sources of metal debris. This study is a retrieval analysis of implants from the same manufacturer with the same MoM bearing surface. The difference between the implants was presence or absence of modular junctions. This is a retrospective study of 31 retrieved implants from 31 patients who received a Conserve Wright Medical MoM hip prosthesis. The 31 implants consisted of 16 resurfacings and 15 implants with modular junctions; 4 conventional THAs and 11 modular-neck THAs. 43% of pre-revision MRI scans performed on resurfacing implants and 91% performed on the modular implants illustrated evidence of an adverse local tissue reaction. There was no difference in pre-revision blood metal ion levels or bearing surface wear between the resurfacings and modular implants. The neck-head tapers of the modular group showed low levels of material loss. However, the neck-stem tapers showed increased severity of corrosion and material loss. The modular implants had an increased incidence of adverse local tissue reaction. This could be related to the presence of modular junctions, particular the neck-stem junction which showed increased susceptibly to corrosion.

Transitioning the total hip arthroplasty technique from posterior approach in lateral position to direct anterior approach in supine position-risk factors for acetabular malpositioning and the learning curve.

Cup positioning is important for optimum hip stability, avoiding component impingement and decreasing both bearing surface wear and revision rate. Transitioning from posterior approach in a lateral position to direct anterior approach (DAA) in a supine presents unique challenges for surgeons. The aim of this study was to examine the learning curve when using standard instrumentation that was not specific to DAA. A consecutive retrospective series of 537 total hip arthroplasty by DAA from May 2013 to December 2017. Cup positioning was analysed on radiographs and classified whether inside or outside two safe zones (inclination 30-50° and anteversion 10-30°). The demographic data (age, BMI, gender, neck shaft angle (NSA)), surgeon's dominant side and experience were assessed as risk factors. Eighty per cent of cups (n = 426) were in the combined safe zones. Eighty-eight per cent (n = 470) were in appropriate anteversion and 87% (n = 463) abduction. Two factors that were significant were identified: Cups of left hips operated by right-handed surgeons were more anteverted (OR = 4.06) and more vertical (OR = 2.23); females had a higher anteversion of the cup (OR = 2.42). Obesity, age and NSA were not risk factors for cup malposition. There was a spike of cups too horizontal at the beginning of the experience (OR = 3.86), and no learning curve was observed in the other orientations. With our DAA technique using standard instrumentation, there were no risk factors linked to the patient identified for cup malposition. DAA-specific instrumentation is not required to achieve optimum positioning of the cup. Surgeon has to be aware of an excess of abduction at the beginning of his experience and an excess of anteversion and adduction when performing THA on the opposite side of his dominant hand.

Primary Total Hip Arthroplasty in Patients 20 Years Old and Younger

Historically, total hip arthroplasty (THA) performed in patients ≤20 years old has been associated with poor survivorship because of bearing-surface wear with conventional polyethylene, acetabular loosening with cemented sockets, and liner fracture in ceramic-on-ceramic (CoC) THA. For this population, there is a paucity of data regarding outcomes of THAs performed with use of modern implants and bearing surfaces. The purpose of the present study was to examine the mid- to long-term outcomes of modern THA in patients ≤20 years old. Utilizing a single-institution, prospectively collected total joint registry, we retrospectively identified 91 primary THAs performed in 78 patients ≤20 years old from 1998 to 2016. The average patient age was 17 years (range, 11 to 20 years), and the average body mass index was 26 kg/m (range, 16 to 49 kg/m). Forty-eight THAs (53%) were performed in male patients, and 47 (52%) were performed on the right hip. Bearing surfaces included CoC (53 THAs, 58%), metal-on-highly cross-linked polyethylene (MoP; 28 THAs, 31%), and ceramic-on-highly cross-linked polyethylene (CoP; 10 THAs, 11%). Outcome measures included reoperations, revisions, complications, clinical outcome scores, and bearing-surface wear. At an average follow-up of 8 years (range, 2 to 18 years), the average modified Harris hip score was 92 (range, 54 to 100), and 95% of patients reported feeling "much better" following the surgical procedure. Survivorship at 2, 5, and 10 years postoperatively was 96.7%, 96.7%, and 95.0% for reoperation; 98.9%, 98.9%, and 97.2% for revision; and 91.2%, 91.2%, and 89.5% for complications, respectively. The most common complications were instability (3 THAs, 3%), aseptic acetabular loosening (2 THAs, 2%), and postoperative foot drop (2 THAs, 2%). Linear articular wear averaged 0.019 mm/yr. There were no correlations between age, sex, body mass index, bearing surface, femoral head size, use of cement, or operative time and survivorship from complications, reoperations, or revisions. There were no differences in linear wear among CoC, CoP, and MoP bearing surfaces. In patients ≤20 years old, THAs performed with use of modern implants exhibit excellent clinical outcome scores and survivorship at mid- to long-term follow-up. CoC, CoP, and MoP bearing surfaces have similar survivorship, clinical outcomes, and bearing-surface wear in this population. Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Adverse Local Tissue Reactions in Total Hip Arthroplasty: Who, When, and How to Revise

Adverse local tissue reaction (ALTR) has initially been described as a complication in metal-on-metal total hip arthroplasty (THA) [ 1 Kwon Y.-M. Glyn-Jones S. Simpson D.J. Kamali A. McLardy-Smith P. Gill H.S. et al. Analysis of wear of retrieved metal-on-metal hip resurfacing implants revised due to pseudotumours. J Bone Joint Surg Br. 2010; 92: 356-361https://doi.org/10.1302/0301-620X.92B3.23281 Crossref PubMed Scopus (185) Google Scholar , 2 Kwon Y.-M. Fehring T.K. Lombardi A.V. Barnes C.L. Cabanela M.E. Jacobs J.J. Risk stratification algorithm for management of patients with dual modular taper total hip arthroplasty: consensus statement of the American Association of Hip and Knee Surgeons, the American Academy of Orthopaedic Surgeons and the Hip Society. J Arthroplasty. 2014; 29: 2060-2064https://doi.org/10.1016/j.arth.2014.07.029 Abstract Full Text Full Text PDF PubMed Scopus (64) Google Scholar , 3 Liow M.H.L. Kwon Y.-M. Metal-on-metal total hip arthroplasty: risk factors for pseudotumours and clinical systematic evaluation. Int Orthop. 2017; 41: 885-892https://doi.org/10.1007/s00264-016-3305-1 Crossref PubMed Scopus (37) Google Scholar , 4 Kwon Y.-M. Cross-sectional imaging in evaluation of soft tissue reactions secondary to metal debris. J Arthroplasty. 2014; 29: 653-656https://doi.org/10.1016/j.arth.2014.02.007 Abstract Full Text Full Text PDF PubMed Scopus (20) Google Scholar , 5 MacDonald S.J. Brodner W. Jacobs J.J. A consensus paper on metal ions in metal-on-metal hip arthroplasties. J Arthroplasty. 2004; 19: 12-16https://doi.org/10.1016/j.arth.2004.09.009 Abstract Full Text Full Text PDF PubMed Scopus (131) Google Scholar ]. However, there have recently been increasing concerns regarding the occurrence of ALTR in metal-on-polyethylene THA due to corrosion at the head-neck taper junction in a process described as mechanically assisted crevice corrosion [ [6] Jacobs J.J. Gilbert J.L. Urban R.M. Corrosion of metal orthopaedic implants. J Bone Joint Surg Am. 1998; 80: 268-282https://doi.org/10.2106/00004623-199802000-00015 Crossref PubMed Scopus (743) Google Scholar ]. The generation of biologically active, nanometer-sized metal particles and metal ions from the arthroplasty bearing surfaces and taper junctions has been associated with the occurrence of localized, adverse periprosthetic soft tissue response, which has been recently recognized as an important emerging mode of failure in THA patients [ 7 Liow M.H.L. Urish K.L. Preffer F.I. Nielson G.P. Kwon Y.-M. Metal ion levels are not correlated with histopathology of adverse local tissue reactions in taper corrosion of total hip arthroplasty. J Arthroplasty. 2016; 31: 1797-1802https://doi.org/10.1016/j.arth.2016.01.041 Abstract Full Text Full Text PDF PubMed Scopus (28) Google Scholar , 8 Kwon Y.-M. MacAuliffe J. Arauz P.G. Peng Y. Sensitivity and specificity of metal ion level in predicting adverse local tissue reactions due to head-neck taper corrosion in primary metal-on-polyethylene total hip arthroplasty. J Arthroplasty. 2018; 33: 3025-3029https://doi.org/10.1016/j.arth.2018.04.007 Abstract Full Text Full Text PDF PubMed Scopus (30) Google Scholar , 9 Cooper H.J. Urban R.M. Wixson R.L. Meneghini R.M. Jacobs J.J. Adverse local tissue reaction arising from corrosion at the femoral neck-body junction in a dual-taper stem with a cobalt-chromium modular neck. J Bone Joint Surg Am. 2013; 95: 865-872https://doi.org/10.2106/JBJS.L.01042 Crossref PubMed Scopus (296) Google Scholar , 10 Vendittoli P.-A. Roy A. Mottard S. Girard J. Lusignan D. Lavigne M. Metal ion release from bearing wear and corrosion with 28 mm and large-diameter metal-on-metal bearing articulations: a follow-up study. J Bone Joint Surg Br. 2010; 92: 12-19https://doi.org/10.1302/0301-620X.92B1.22226 Crossref PubMed Scopus (100) Google Scholar , 11 Seon J.-K. Park J.-K. Shin Y.-J. Seo H.-Y. Lee K.-B. Song E.-K. Comparisons of kinematics and range of motion in high-flexion total knee arthroplasty: cruciate retaining vs. substituting designs. Knee Surg Sports Traumatol Arthrosc. 2011; 19: 2016-2022https://doi.org/10.1007/s00167-011-1434-z Crossref PubMed Scopus (51) Google Scholar ]. At the 2019 Annual Meeting of American Association of Hip and Knee Surgeons, the symposium on ALTRs with particular focus on “who, when, and how to revise” patients with ALTR was presented. The objectives of this symposium were to summarize clinical challenges in optimizing patient evaluation and revision surgery outcome. Specifically, the symposium presentations highlighted that there is a spectrum of clinical presentations of ALTRs due to taper corrosion and metal bearing surface wear, reflecting a complex interplay of implant, surgical, and patient factors. The current state of knowledge on the importance of various taper material combinations and taper design geometry on taper corrosion is evolving. A systematic risk stratification approach based on currently available data is critical in optimizing evaluation and revision surgery indications. The utility and limitations of specialized diagnostic tests including metal ion levels and cross-sectional imaging studies such as metal artifact reduction sequence magnetic resonance imaging in the clinical decision-making process is important in evaluation of these patients. Furthermore, optimizing revision surgery outcome for ALTRs involves careful preoperative planning, implant selection, and surgical techniques to overcome challenges associated with soft tissue necrosis.

Quantifying the bearing surface wear of retrieved hip replacements

Accurate quantification of bearing material loss from retrieved metal-on-metal (MOM) hip replacements is key to understanding their failure. Geometric methods are currently the only means of estimating volumetric wear from retrieved implants and numerous contrasting approaches to obtain these measures have been published. Data collection strategies have been thoroughly discussed and refined to minimise the effect of error incurring factors; however, there is an opportunity to optimise the current methods of estimating the pre-wear geometry and, therefore, improve the accuracy of wear volume measurements. An automated analysis strategy to quantify volumetric wear is proposed in this study, which utilises the entire bearing surface to determine the implants pristine geometry. This involves the iterative removal of geometrically effected data points to optimise the fit and size of a perfect sphere. Once fitted, this reference geometry is compared with the measured data, in its entirety, to calculate the volume change representative of the quantity of material lost. Improving the reliability of this parameter could influence the care of a million patients that remain with MOM hip implants. Rigorous validation of this method will dominate future work, ensuring that the accuracy and reliability of this approach are sufficient to provide clinically meaningful data.

Analysis of bearing wear, whole blood and synovial fluid metal ion concentrations and histopathological findings in patients with failed ASR hip resurfacings

BackgroundAdverse Reaction to Metal Debris (ARMD) is still a major reason for revision surgeries in patients with metal-on-metal (MoM) hip replacements. ARMD consists of a wide range of alterations in periprosthetic tissues, most important of which are metallosis, inflammation, pseudotumors and necrosis. Studies investigating histopathological findings and their association to implant wear or indirect measures of wear have yielded inconsistent results. Therefore, we aimed to investigate bearing surface wear volume, whole blood and synovial fluid metal ion concentrations, histopathological findings in periprosthetic tissues and their associations.MethodsSeventy-eight patients with 85 hips revised for ARMD were included in the study. Prior to revision surgery, all patients had whole blood chromium and cobalt ion levels assessed. In revision surgery, a synovial fluid sample was taken and analyzed for chromium and cobalt. Periprosthetic tissue samples were taken and analyzed for histopathological findings. Explanted implants were analyzed for bearing wear volume of both acetabular cup and femoral head components.ResultsVolumetric wear of the failed components was highly variable. The total wear volume of the head and cup had a strong correlation with whole blood chromium and cobalt ion concentrations (Cr: ρ = 0.80, p < 0.001 and Co: ρ = 0.84, p < 0.001) and a bit weaker correlation with fluid chromium and cobalt ion concentrations (Cr: ρ = 0.50, p < 0.01 and Co: ρ = 0.41, p = 0.027). Most tissues displayed only low-to-moderate amounts of macrophages and lymphocytes. Total wear volume correlated with macrophage sheet thickness (ρ = 0.25, p = 0.020) and necrosis (ρ = 0.35, p < 0.01). Whole blood chromium and cobalt ion concentrations had similar correlations. Lymphocyte cuff thickness did not correlate with either total wear volume or whole blood metal ion concentrations, but correlated with the grade of necrosis.ConclusionsBearing wear volume correlated with blood metal ion levels and the degree of necrosis and macrophage infiltration in periprosthetic tissues suggesting a dose-response relationship. Whole blood metal ion levels are a useful tool for clinician to estimate bearing wear and subsequent tissue response.

Investigation of Taper Failure in a Contemporary Metal-on-Metal Hip Arthroplasty System Through Examination of Unused and Explanted Prostheses

Large-diameter (≥36-mm) metal-on-metal (MoM) total hip replacements have been shown to fail at an unacceptably high rate. Globally, the DePuy Pinnacle prosthesis was the most widely used device of this type. There is evidence to suggest that one of the main reasons for the poor clinical performance of large-diameter MoM prostheses is the metal debris released from the head-stem taper junction-i.e., taper junction failure. The aim of this study was to investigate variation in the as-manufactured finish of the female taper surface and to determine its influence on material loss. We hypothesized that rougher surfaces with higher relative material peaks would be significantly associated with greater taper wear rates. We analyzed 93 Articul/eze femoral head tapers with a 36-mm bearing diameter that had been used in combination with a Corail titanium uncemented stem. The influence of the surface topography of the as-manufactured female taper surface on taper wear was examined by means of a multiple regression model, taking into account other known variables. We identified great variation in the as-manufactured surface finish of the female taper surface, with a range of measured Ra values from 0.14 to 4.20 μm. The roughness of the female taper surface appeared to be the most important variable associated with taper wear (p < 0.001). The best-fitting regression model, including duration in vivo, head offset, reduced peak height (Rpk) value, stem shaft angle, and bearing surface wear rate, explained approximately 44% of the variation in taper wear rates. We concluded that the roughness of the female taper surface appears to be a significant factor in metal debris release from head-stem taper junctions. This study shows evidence that previously unappreciated variations in manufacturing processes may have a major impact on the clinical outcomes of patients.

Factors Associated With Trunnionosis in the Metal-on-Metal Pinnacle Hip

BackgroundTrunnionosis of the tapered head-stem junction of total hip arthroplasties, either through corrosion or mechanical wear, has been implicated in early implant failure. Retrieval analysis of large numbers of failed implants can help us better understand the factors that influence damage at this interface. MethodsIn this study, we examined 120 retrieved total hip arthroplasties of one bearing design, the 36-mm diameter metal-on-metal, DePuy Pinnacle, that had been paired with 3 different stems. We measured material loss of the bearing and head-trunnion taper surfaces and collected clinical and component data for each case. We then used multiple linear regression analysis to determine which factors influenced the rate of taper material loss. ResultsWe found 4 significant variables: (1) longer time to revision (P = .004), (2) the use of a 12/14 taper for the head-trunnion junction (P < .001), (3) decreased bearing surface wear (P = .003), and (4) vertical femoral offset (P = .05). These together explained 29% of the variability in taper material loss. ConclusionOur most important finding is the effect of trunnion design. Of the 3 types studied, we found that S-ROM design was the most successful at minimizing trunnionosis.

Adoption of Robotic vs Fluoroscopic Guidance in Total Hip Arthroplasty: Is Acetabular Positioning Improved in the Learning Curve?

BackgroundAcetabulum positioning affects dislocation rates, component impingement, bearing surface wear rates, and need for revision surgery. Novel techniques purport to improve the accuracy and precision of acetabular component position, but may have a significant learning curve. Our aim was to assess whether adopting robotic or fluoroscopic techniques improve acetabulum positioning compared to manual total hip arthroplasty (THA) during the learning curve. MethodsThree types of THAs were compared in this retrospective cohort: (1) the first 100 fluoroscopically guided direct anterior THAs (fluoroscopic anterior [FA]) done by a surgeon learning the anterior approach, (2) the first 100 robotic-assisted posterior THAs done by a surgeon learning robotic-assisted surgery (robotic posterior [RP]), and (3) the last 100 manual posterior (MP) THAs done by each surgeon (200 THAs) before adoption of novel techniques. Component position was measured on plain radiographs. Radiographic measurements were taken by 2 blinded observers. The percentage of hips within the surgeons’ “target zone” (inclination, 30°-50°; anteversion, 10°-30°) was calculated, along with the percentage within the “safe zone” of Lewinnek (inclination, 30°-50°; anteversion, 5°-25°) and Callanan (inclination, 30°-45°; anteversion, 5°-25°). Relative risk (RR) and absolute risk reduction (ARR) were calculated. Variances (square of the standard deviations) were used to describe the variability of cup position. ResultsSeventy-six percentage of MP THAs were within the surgeons’ target zone compared with 84% of FA THAs and 97% of RP THAs. This difference was statistically significant, associated with a RR reduction of 87% (RR, 0.13 [0.04-0.40]; P < .01; ARR, 21%; number needed to treat, 5) for RP compared to MP THAs. Compared to FA THAs, RP THAs were associated with a RR reduction of 81% (RR, 0.19 [0.06-0.62]; P < .01; ARR, 13%; number needed to treat, 8). Variances were lower for acetabulum inclination and anteversion in RP THAs (14.0 and 19.5) as compared to the MP (37.5 and 56.3) and FA (24.5 and 54.6) groups. These differences were statistically significant (P < .01). ConclusionAdoption of robotic techniques delivers significant and immediate improvement in the precision of acetabular component positioning during the learning curve. While fluoroscopy has been shown to be beneficial with experience, a learning curve exists before precision improves significantly.

Clinical significance of corrosion of cemented femoral stems in metal-on-metal hips: a retrieval study.

The clinical significance of corrosion of cemented femoral stems is unclear. The purpose of this retrieval study was to: (1) report on corrosion at the stem-cement interface and (2) correlate these findings with clinical data. We analysed cemented stems (n = 36) composed of cobalt-chromium (CoCr) and stainless steel (SS) in a series of revised metal-on-metal hips. We performed detailed inspection of each stem to assess the severity of corrosion at the stem-cement interface using a scale of 1 (low) to 5 (severe). We assessed the severity of corrosion at each stem trunnion and measured wear rates at the head taper and bearing surfaces. We used non-parametric tests to determine the significance of differences between the CoCr and SS stems in relation to: (1) pre-revision whole blood Co and Cr metal ion levels, (2) trunnion corrosion, (3) bearing surface wear and (4) taper material loss. The corrosion scores of CoCr stems were significantly greater than SS stems (p < 0.01). Virtually all stem trunnions in both alloy groups had minimal evidence of corrosion. The median pre-revision Co levels of implants with CoCr stems were significantly greater than the SS stems (p < 0.01). There was no significant difference in relation to pre-revision Cr levels (p = 0.521). There was no significant difference between the two stem types in relation to bearing wear (p = 0.926) or taper wear (p = 0.148). Severe corrosion of cemented femoral stems is a common finding at our retrieval centre; surgeons should consider corrosion of CoCr stems as a potential source of metal ions when revising a hip.

CORR Insights(®): oxidized zirconium head on crosslinked polyethylene liner in total hip arthroplasty: a 7- to 12-year in vivo comparative wear study.

Where Are We Now? Hip surgeons and material scientists agree that while reducing bearing-surface wear after THA is important, the real goals are to prevent osteolysis and aseptic loosening. Most hip replacements are performed using highly crosslinked polyethylene (XLPE) liners, since many surgeons are concerned about problems associated with ceramic-on-ceramic and metal-on-metal (MoM) bearings, including squeaking and ceramic fractures for the former [1], and elevated serum ion levels from (MoM) couplings with the latter [6]. However, although a metaanalysis of randomized trials confirmed that XLPE decreased linear and volumetric wear rates [11], it remains unclear whether XLPE actually reduces the likelihood of aseptic loosening after THA [10]. Recommended as an alternative bearing surface, oxidized zirconium was developed to reduce the wear rates of cobalt-chrome heads against polyethylene bearings. The linear wear rate for oxidized zirconium with XLPE liners has been shown to be 4 μm/year [4]. However, in a 5-year followup of a randomized controlled trial, no difference in wear rates was noted between cobalt-chrome and oxidized zirconium heads with XLPE [9]. Crosslinked polyethylene liners seem to make a larger difference in wear than does the head surface against which the polyethylene is placed. Where Do We Need To Go? With the number of primary and revision THAs rising, it is crucial that we produce reliable implants with excellent long-term durability and biocompatability. Further study on the long-term data associated with oxidized zirconium on XLPE bearings is warranted. In their paper, Karidakis and colleagues report lower wear rates of oxidized zirconium heads on XLPE liners when compared to ceramic heads. We need solid long-term data reflecting not only the survival of the implant and the wear rates of bearing surfaces, but also the effects of the wear debris on our patients’ bodies. Because some reports have found that XLPE liners produce wear particles in the submicron range, which can be phagocytosed by human monocytes and so may over longer time periods yet result in osteolysis [12, 14], longer-term studies are needed. The production of rather round shaped submicron wear particles by XLPE liners is a concern that has not been adequately adressed by in vivo studies. Phagocytosed wear particles have the capability to get to the liver, spleen, and other organs [13]. As orthopaedic surgeons, we often rely on radiographs to follow our patients; while perhaps adequate to identify major problems like wear or loosening, I believe we have to do a better job of considering the impact of orthopaedic implants on the whole patient, and not just the hip. We need to learn more about the systemic effects of the arthroplasties we perform. How Do We Get There? To get these answers, we need carefully conducted, long-term clinical followup studies that evaluate THA bearings. Digitized radiographs with computer-aided wear analysis or radiostereometry [5, 10] can provide us with data about the rate of wear at the hip, but as I have suggested here, we need to begin to answer some larger questions about corrosion products and wear debris created by THAs in vivo. Ideally, future investigations will develop methods that can properly identify the fate of these wear particles. Autopsies of patients with THA could provide us with sections of liver, spleen, and other organs. Previous studies [2, 3, 13] have shown mostly metal but also ultrahigh molecular weight polyethylene particle dissemination to those organs. The detected polyethylene particles were in the submicron range. The increased production of such wear particles by XLPE calls for more and larger postmortem studies in order to rule out accumulation of wear debris in parenchymatous and lymphoreticular tissues. Flow cytometry could be a tool to identify monocytes loaded with polyethylene particles in vivo. Laser-scanning microscopy could potentially identify human monocytes containing wear particles. Wear debris from orthopaedic implants is present in lymphoreticular tissue. An increase in wear particle load of human monocytes could reduce the capacity of the immune system. Therefore, we must check the immune system for activity of interleukins, interferone, and tumor necrosis factor, as XLPE wear particles have been shown to induce an increased inflammatory response in vitro [7, 8]. We still have a great deal to learn about the wear particles generated by oxidized zirconium heads on XLPE liners, both at the local and systemic levels.

Complications of Total Hip Arthroplasty: Standardized List, Definitions, and Stratification Developed by The Hip Society.

Reporting of complications after total hip arthroplasty (THA) is not standardized, and it is done inconsistently across various studies on the topic. Advantages of standardizing complications include improved patient safety and outcomes and better reporting in comparative studies. The purpose of this project was to develop a standardized list of complications and adverse events associated with THA, develop standardized definitions for each complication, and stratify the complications. A further purpose was to validate these standardized THA complications. The Hip Society THA Complications Workgroup proposed a list of THA complications, definitions for each complication, and a stratification scheme for the complications. The stratification system was developed from a previously validated grading system for complications of hip preservation surgery. The proposed complications, definitions, and stratification were validated with an expert opinion survey of members of The Hip Society, a case study evaluation, and analysis of a large administrative hospital system database with a focus on readmissions. One hundred five clinical members (100%) of The Hip Society responded to the THA complications survey. Initially, 21 THA complications were proposed. The validation process reduced the 21 proposed complications to 19 THA complications with definitions and stratification that were endorsed by The Hip Society (bleeding, wound complication, thromboembolic disease, neural deficit, vascular injury, dislocation/instability, periprosthetic fracture, abductor muscle disruption, deep periprosthetic joint infection, heterotopic ossification, bearing surface wear, osteolysis, implant loosening, cup-liner dissociation, implant fracture, reoperation, revision, readmission, death). Acceptance and use of these standardized, stratified, and validated THA complications and adverse events could advance reporting of outcomes of THA and improve assessment of THA by clinical investigators. Level V, therapeutic study.

Predictive value of robotic-assisted total hip arthroplasty.

Acetabular cup positioning, leg-length discrepancy, and global offset are important parameters associated with outcomes following total hip arthroplasty (THA). Deviation from an accepted range of values can lead to significant complications, including dislocation, leg-length discrepancy, impingement, accelerated bearing surface wear, and revisions. The purpose of this study was to assess whether robotic-assisted THA was reliable in predicting radiographic measurements of cup inclination and anteversion, leg-length change, and global offset change. All 61 robotic-assisted THAs that met the inclusion and exclusion criteria were performed by a single surgeon through a mini-posterior approach. Data provided by the robot were collected prospectively, and radiographic data were collected retrospectively by 2 blinded independent reviewers. The cohort in this study consisted of 27 male and 34 female patients, with an average age of 60.5 years. A strong inter- and intraobserver correlation was found for the radiographic measurements of cup inclination, cup anteversion, leg-length discrepancy, and global offset (r>0.8 with P<.001 for all). Ninety-six point seven percent of robotic-measured inclination angles and 98.4% of robotic-measured anteversion angles were within 10° of radiographic measurements. One hundred percent of robotic-measured leg-length change and 91.8% of robotic-measured global offset change were within 10 mm of radiographic measurements. Robotic-assisted THA showed good predictive value for cup inclination and anteversion angles and measurements of leg-length change and global offset change done postoperatively on plain radiographs. Further refinement of the robotic system would make it more accurate in predicting the postoperative parameters mentioned.