Polyethylene Wear Debris Research Articles

UHMWPE for Arthroplasty: From Powder to Debris: Editorial Comment: A Perspective on Polyethylene

The success of total joint arthroplasty hinges on a number of factors, including proper surgical technique, appropriate patient selection, and proven implant design. As a well-known component of implant design, ultra-high-molecular-weight polyethylene (UHMWPE) may seem like an unlikely research topic for a special symposium in Clinical Orthopaedics and Related Research (CORR). How could there be anything new or noteworthy to say about this common plastic? As it turns out, plenty. The papers in this symposium cover a broad range of topics related to advances in polyethylene, ranging from their clinical performance, local tissue reactions to wear debris, fracture resistance, and innovations in their formulation. This symposium includes a selection of papers presented at the 4th International Meeting of UHMWPE for Arthroplasty, which was convened in Torino, Italy, on September 16–17, 2009. This international polyethylene meeting was organized by Prof. Luigi Costa starting in 2001 as a forum to discuss vitamin E stabilization. Since that time, the meeting has grown to include over 100 participants and talks on a broad range of topics dealing with medical-grade polyethylene. This CORR symposium represents the first time papers presented at the meeting have been organized as a collection of peer-reviewed publications. With preparations for the 5th International UHMWPE meeting underway for September 2011 in Philadelphia, PA, the present symposium marks an important milestone in the organization of an independent and growing polyethylene research community composed of orthopaedic scientists, surgeons, materials scientists, and biomedical engineers. It is an exciting time, still, to be engaged in both basic science and clinical polyethylene research. Two systematic reviews included with this symposium provide context for the clinical performance of first-generation highly crosslinked and thermally treated polyethylenes and the emerging field of vitamin E-stabilized polyethylene biomaterials, respectively. Polyethylene hip and knee implants containing vitamin E have been cleared by regulatory agencies in Europe, Asia, and the United States. Considering that incorporating reinforced agents and additives into polyethylene became a taboo subject after the controversial introduction of carbon fiber-filled Poly Two in the 1970s, the regulatory clearance of polyethylene containing vitamin E challenges the historical paradigm of additive-free polymer bearings for arthroplasty and has given birth to a new, clinically relevant research topic for polyethylene. As a result, it may seem ironic today that polyethylene was considered obsolete in certain circles during the 1990s. The specter of particle-induced, inflammatory bone loss caused by polyethylene wear debris provided motivation to develop second-generation ceramic and metal bearings. These more expensive alternatives to polyethylene introduced new and unanticipated clinical failure modes, including intolerable bearing noise experienced by certain ceramic bearings and, more troubling, the adverse local tissue reactions reported for certain metal bearings. As populations age, increasing the demand for joint arthroplasty, the limited economic resources for health care will sharply focus technology selection by surgeons on proven value. Polyethylene remains in the spotlight for total joint arthroplasty, in a way that was perhaps inconceivable even 5 years ago. Polyethylene, we should all realize, is here to stay.

Osteolytic Lesion of the Tibial Diaphysis After Cementless TKA

Biomaterial wear debris is a known contributing factor in aseptic loosening of total joint prostheses, particularly when cementless tibial trays are used in total knee arthroplasty (TKA). Local inflammatory response can lead to osteolysis and aseptic loosening of implants. The resulting lesions require careful clinical evaluation. This article presents a case of a 76-year old man with a remote history of prostate cancer and cigarette smoking who presented with acute onset left knee and tibia pain 15 years after TKA. Radiographs showed an osteolytic lesion in the distal tibial diaphysis and magnetic resonance imaging revealed a cystic lesion with evidence concerning for pathologic mid-shaft fracture. Biopsy of the lesion confirmed a foreign body reaction and revision TKA was performed. The patient was seen at 3-year follow-up without complication. The existing literature presents cases reporting osteolytic lesions of the distal femur and proximal tibial metaphysis due to polyethylene wear debris and foreign body reaction following TKA. We are unaware of case reports involving osteolysis of this etiology extending into the distal tibial diaphysis. We conclude that polyethylene wear debris with foreign body reaction should be considered in the differential diagnosis of an osteolytic lesion extending into the tibial diaphysis following TKA.

Wear Rate in a Series of Retrieved RP Knee Bearings

Abstract Rotating platform mobile bearing knees are an appealing approach to the problems of tibial loosening and rotational mal-alignment that are of concern with fixed bearing knees. A potential disadvantage of rotating platform (RP) bearings is ultra-high molecular weight polyethylene (UHMWPE) wear debris from the large additional backside articular surface that accommodates tibio-femoral rotation. The investigation of a series of 76 rotating platform knees (Sigma® RP, DePuy/J&J, Warsaw, IN) indicates that UHMWPE bearing wear, as measured by change in through-thickness dimension, increases monotonically with time in vivo. Total wear penetration rate is 0.023 mm/year and shows a decreasing trend, though this trend is not statistically significant. The current study results are consistent with the decreasing wear rate previously reported in a series of LCS® RP (DePuy/J&J, Warsaw, IN) knee. This decreasing wear rate stands in contrast to an increasing backside-only wear rate reported in fixed bearing knees. An important contribution of the current study is that it provides a conservative measurement of total wear penetration and penetration rate in one mobile bearing design over time out to>8 years.

Damage and Wear: An Important Distinction in Rotating Platform Knee Bearings

Abstract Rotating platform mobile bearing knees are an appealing approach to the problems of tibial loosening and rotational malignment in fixed bearing knees. A potential disadvantage is the additional large articular surface that accommodates tibio-femoral rotation. Accurately assessing the tribological performance of this additional articular surface is important to understanding how mobile bearings perform in terms of generating polyethylene wear debris and associated osteolysis. A series of 76 retrieved Sigma Rotating Platform bearings were assessed for damage rating according to conventional protocol and through-thickness wear measurements were taken. The results show that the rotation surface of these bearings is very commonly subject to moderate and severe damage and that damage can occur early following implantation. The decrease of the through-thickness dimension is strongly correlated with time in vivo. The rotation surface damage rating shows a weak though statistically significant correlation to through-thickness wear. Three dimensional surface profilometry on the bearings illuminates phenomena that can explain the paradoxical observations that severely damaged bearings may not be worn and worn bearing areas are smoother and show less damage than unworn areas. This study finds that bearing damage is distinct from bearing wear and the two terms are not interchangeable in the context of assessing material loss from artificial knee bearings. While both processes are important in the tribology of knee devices, it is not accurate to use damage on ultrahigh molecular weight polyethylene as a proxy for wear.

B219 Co-Cr-Mo合金表面へのテクスチャリングがUHMWPE摩耗粉の形態に及ぼす影響(B2-4 関節のバイオメカニクス3)

B219 Co-Cr-Mo合金表面へのテクスチャリングがUHMWPE摩耗粉の形態に及ぼす影響(B2-4 関節のバイオメカニクス3)

Do Tissues From THA Revision of Highly Crosslinked UHMWPE Liners Contain Wear Debris and Associated Inflammation?

Polyethylene wear debris is a major contributor to inflammation and the development of implant loosening, a leading cause of THA revisions. To reduce wear debris, highly crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE) was introduced to improve wear properties of bearing surfaces. As highly crosslinked UHMWPE revision tissues are only now becoming available, it is possible to examine the presence and association of wear debris with inflammation in early implant loosening. We asked: (1) Does the presence of UHMWPE wear debris in THA revision tissues correlate with innate and/or adaptive immune cell numbers? (2) Does the immune cell response differ between conventional and highly crosslinked UHMWPE cohorts? We collected tissue samples from revision surgery of nine conventional and nine highly crosslinked UHMWPE liners. Polarized light microscopy was used to determine 0.5- to 2-μm UHMWPE particle number/mm2, and immunohistochemistry was performed to determine macrophage, T cell, and neutrophil number/mm2. For the conventional cohort, correlations were observed between wear debris and the magnitude of individual patient macrophage (ρ=0.70) and T cell responses (ρ=0.71) and between numbers of macrophages and T cells (ρ=0.77) in periprosthetic tissues. In comparison, the highly crosslinked UHMWPE cohort showed a correlation between wear debris and the magnitude of macrophage responses (ρ=0.57) and between macrophage and T cell numbers (ρ=0.68). Although macrophages and T cells were present in both cohorts, the highly crosslinked UHMWPE cohort had lower numbers, which may be associated with shorter implantation times. The presence of wear debris and inflammation in highly crosslinked UHMWPE revision tissues may contribute to early implant loosening.

Implant Design Influences Tibial Post Wear Damage in Posterior-stabilized Knees

The tibial post in posterior-stabilized total knees is a potential source of polyethylene wear debris, but the relationship between the shape and location of the tibial post in relation to the tibiofemoral bearing surfaces and the subsequent wear damage patterns remains unknown. We used observations made on retrieved implant components from three contemporary posterior-stabilized knee designs to examine how differences in tibial post design affected wear damage on the post. We examined 113 retrieved Zimmer NexGen(®), 103 Exactech Optetrak(®), and 58 Smith and Nephew Genesis(®) II posterior-stabilized inserts using a subjective scale to grade post damage. All 274 inserts demonstrated wear damage. Total wear scores and scores for wear damage on the anterior post differed among designs: Optetrak(®) 20 ± 4 and 5 ± 1, NexGen(®) 13 ± 4 and 3 ± 1, and Genesis(®) II 8 ± 3 and 1 ± 1, respectively. The Optetrak(®) had predominantly anterior wear damage, the NexGen(®) had more global wear damage, and the Genesis(®) II had predominantly posterior wear damage. Tibial post wear damage and anterior post wear damage were primarily determined by implant design and to a lesser extent by length of implantation and revision diagnosis. Although tibial post wear damage is multifactorial, the primary determinant of wear damage, and specifically anterior wear damage, is implant design. The constraint provided by the posterior-stabilized post-cam contact in modern knee arthroplasties is reflected in the wear damage patterns that occur during in vivo use. Unintended constraint such as anterior impingement should be addressed through design modifications for future posterior-stabilized knee arthroplasties.

Electrochemical Instrumentation of a Hip Simulator: A New Tool for Assessing the Role of Corrosion in Metal-On-Metal Hip Joints

Polyethylene wear debris induced osteolysis has triggered investigations to find alternative material combinations to the well-established metal-on-polyethylene hip implants. Owing to some early successful clinical cases, metal-on-metal (MoM) hip replacements have been attracting more and more interest. There is, however, considerable concern about the propensity of MoM hip replacements to release metal ions and fine, nanometre-scale metallic wear debris. The long-term effect from released metal ions and wear particles is still not clear. To date, all the work on hip simulators focused on assessing mass losses damage has been referred to as 'wear'. However, it is known in the field of tribocorrosion that mechanical removal of the passive layer on Co-Cr alloys can significantly enhance corrosion activity. In total joint replacements, it is possible that corrosion plays a significant role. However, no one has ever tried to extract, on a hip simulator, what proportion of the damage is due to mechanical processes and the corrosion processes. This paper describes the first instrumentation of an integrated hip joint simulator to provide in-situ electrochemical measurements in real time. The open circuit potential results are reported to assess the corrosion regime in the absence and presence of movement at the bearing surfaces. The importance of these measurements is that the real damage mechanisms can be assessed as a function of the operating cycle.

In vitro and in vivo evaluation of an alumina–zirconia composite for arthroplasty applications

In order to improve the reliability and the mechanical properties of orthopaedic hip prosthesis, new ceramic composites starting with nanosized powders of alumina and zirconia have been recently developed. The aim of the present study was to investigate the biological tolerance of one of these sintered ceramics and of its alumina and zirconia constitutive nanosized powders with both in vitro and in vivo approaches. At first, osteoblasts and fibroblasts were cultured either upon sintered ceramic discs with polished or rough surfaces or in the presence of the corresponding alumina or zirconia powders at various concentrations. Thereafter, we chronically injected these powders in the knee articulation of rats. In vitro, the materials showed no deleterious effect on cell proliferation, extra-cellular matrix production (human type I collagen and fibronectin) or on cell morphology. In vivo, the histological examination showed only a very moderate and non-specific granulomatous response of the synovial membrane but no major inflammation as clinically described with metals or polyethylene wear debris. Besides its improved physical properties, this recently developed alumina–zirconia composite showed satisfactory biocompatibility.

Delta Ceramic-on-Alumina Ceramic Articulation in Primary THA: Prospective, Randomized FDA-IDE Study and Retrieval Analysis

Wear and osteolysis continue to be major reasons for revision surgery in THA. Ceramic-on-ceramic bearings eliminate polyethylene wear debris. The newest generation of these bearings incorporate nanosized, yttria-stabilized tetragonal zirconia particles producing an alumina matrix composite. We asked whether this new material would perform as well as a conventional bearing in terms of functional hip scores, radiographic migration and osteolysis, complications and survival. As part of a US FDA investigational device exemption study (G000075), we conducted an initial prospective safety study of 21 alumina matrix composite femoral heads articulating on alumina liners followed by a prospective, randomized study with 44 more of these articulations and 45 zirconia femoral heads on polyethylene liners. The minimum followup for all patients was 26 months (mean, 73 months; range, 26-108 months). Harris hip scores and radiographic findings were similar in the two groups as was survivorship (trial 95% versus control 93%). There were three reoperations in the trial group and three in the control group. A fractured head retrieval showed a 33% monoclinic transformation with an increase in surface roughness from 3 to 5 nm at the main wear zone. While our numbers were insufficient to compare device-related complications, the trial device performed as well as the control device in terms of reoperation, and clinical and radiographic outcome. The alumina matrix composite femoral head on an alumina liner provided high survivorship. Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Polyethylene wear debris produced in a knee simulator model: Effect of crosslinking and counterface material

Polyethylene (PE) debris has been well studied in clinical retrievals and laboratory wear simulations of total hip replacements. However, little is known about PE debris from total knee replacements. In this study, we investigated the effects of crosslinking PE bearings and alternate counterface material. Mildly (35 kGy) and highly (70 kGy) crosslinked PE were studied in combination with CoCr and zirconia femoral counterfaces. Wear debris was isolated and its morphology characterized. Except for changes in PE debris size with the zirconia bearings, there were no morphological changes greater than 10%. The average submicron volume fraction decreased from about 65% to 45% with both increased crosslinking and changing counterface material from CoCr to zirconia. The averaged number of generated particles decreased by approximately fourfold with increased crosslinking and threefold with changing counterface material from CoCr to zirconia. This showed that the degree of PE crosslinking and the choice of counterface material were important factors in the PE wear debris production in total knee simulator replacements.

Deposition of a-C:H films on UHMWPE substrate and its wear-resistance

In prosthetic hip replacements, ultrahigh molecular weight polyethylene (UHMWPE) wear debris is identified as the main factor limiting the lifetime of the artificial joints. Especially UHMWPE debris from the joint can induce tissue reactions and bone resorption that may lead to the joint loosening. The diamond like carbon (DLC) film has attracted a great deal of interest in recent years mainly because of its excellent tribological property, biocompatibility and chemically inert property. In order to improve the wear-resistance of UHMWPE, a-C:H films were deposited on UHMWPE substrate by electron cyclotron resonance microwave plasma chemical vapor deposition (ECR-PECVD) technology. During deposition, the working gases were argon and acetylene, the microwave power was set to 800 W, the biased pulsed voltage was set to −200 V (frequency 15 kHz, duty ratio 20%), the pressure in vacuum chamber was set to 0.5 Pa, and the process time was 60 min. The films were analysed by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, nano-indentation, anti-scratch and wear test. The results showed that a typical amorphous hydrogenated carbon (a-C:H) film was successfully deposited on UHMWPE with thickness up to 2 μm. The nano-hardness of the UHMWPE coated with a-C:H films, measured at an applied load of 200 μN, was increased from 10 MPa (untreated UHMWPE) to 139 MPa. The wear test was carried out using a ball (Ø 6 mm, SiC) on disk tribometer with an applied load of 1 N for 10000 cycles, and the results showed a reduction of worn cross-sectional area from 193 μm 2 of untreated UHMWPE to 26 μm 2 of DLC coated sample. In addition the influence of argon/acetylene gas flow ratio on the growth of a-C:H films was studied.

In vitro macrophage response to polyethylene and polycarbonate‐urethane particles

This study was undertaken to compare macrophage response to polycarbonate-urethane (PCU), a proposed alternative material to polyethylene in acetabular components of total hip arthroplasty to cross-linked ultra-high molecular weight polyethylene (xUHMWPE) in the presence or absence of endotoxin. Polyethylene wear debris that is generated by total hip and knee replacements has been linked to osteolysis and limiting the lifespan of the implant. We added both lipopolysaccharide (LPS)-free and endotoxin-associated xUHMWPE and PCU particles to a human monocyte cell line (TH1) in culture and measured cell viability and tumor necrosis factor (TNF)alpha, interleukin (IL)-1beta, and prostaglandin E(2) (PGE(2)) in the medium after 24 h. Results indicate that particles (both xUHMWPE and PCU) free of endotoxin did not significantly induce secretion of TNFalpha, IL-1beta, or PGE(2) above basal levels. However, endotoxin-exposed PCU particles induced significantly less TNFalpha and IL-1beta than endotoxin-exposed xUHMWPE particles. This indicates that if endotoxin is available for binding to particles in vivo, then xUHMWPE may be more inflammatory to periprosthetic tissue and bone in part because of its affinity/reactivity with endotoxin when compared with PCU.

In vivo response to cross‐linked polyethylene and polycarbonate‐urethane particles

This study was undertaken to examine macrophage response to polycarbonate-urethane, a proposed alternative material to polyethylene in acetabular components of total hip arthroplasty. Polyethylene wear debris from total joint replacements has been linked to osteolysis and implant lifespan. It has been shown in vitro, that polyethylene particles cleaned of endotoxin generate less of an inflammatory cytokine response than endotoxin bound particles. Comparative particle induced effects on implant fixation were tested using endotoxin free cross-linked ultra-high molecular weight polyethylene (x-UHMWPE) and polycarbonate-urethane (PCU) particles with and without intraperitoneal injection (IP) of lipopolysaccharide (LPS) using a Ti-alloy femoral intramedullary nail rat model. MicroCT and mechanical testing assessment of peri-implant bone indicated significantly less bone and lower fixation strength, respectively, when the implant was surrounded by xUHMWPE particles compared to PCU particles (with and without LPS IP). This indicates particles of PCU may be less disruptive to bone-implant fixation than x-UHMWPE in vivo, under both LPS free and challenged conditions.

Comparison of periprosthetic tissue digestion methods for ultra‐high molecular weight polyethylene wear debris extraction

There is considerable interest in characterization of wear debris from polyethylene (UHMWPE) bearing components used in total joint replacement. To isolate UHMWPE wear debris, tissue samples must be excised from regions adjacent to revised UHMWPE implant components, followed by exposure to one of many available tissue digestion methods. Numerous studies demonstrate successful digestion, but the relative efficiency of each method is not clear. The purpose of this study was to evaluate a variety of conditions for tissue digestion to provide a quantitative comparison of methods. Porcine and human hip tissues were exposed for 24 h to basic, acidic or enzymatic agents, filtered and digestion efficiency calculated based on the percentage of initial to final tissue weight. Of the conditions tested, 5 M NaOH, 5 M KOH, 15 M KOH or 15.8 M HNO(3) yielded the most complete porcine hip tissue digestion (<1% residual tissue weight; p < 0.05). Proteinase K and Liberase Blendzyme 3 did not effectively digest tissue in a 24 h period. Similar to results from the porcine dataset, human tissues digestion was most efficient using 5 M NaOH, 5 M KOH or 15.8 M HNO(3) (<1% residual tissue weight; p < 0.05). To verify that particle surface modifications did not occur after prolonged reagent exposure, GUR415 and Ceridust 3715 particles were immersed in each solution for 24 h. Overall, this study provides a framework for thorough and efficient digestive methods for UHMWPE wear debris extraction.

Effect of metallic nanoparticles on the biotribocorrosion behaviour of Metal-on-Metal hip prostheses

Concerns of polyethylene wear debris induced osteolysis has been partially responsible for the renewed interest in the second generation Metal-on-Metal (MoM) hip replacements as an alternative to widely used Metal-on-Polyethylene (MoP) joint prostheses. The total wear loss from MoM is much less than from MoP. However, the number of nano-sized wear particles from MoM is more than a hundred times than from MoP. Some of the particles are released to the surrounding tissues and some remain in the bearing contact area as a third-body. This paper focuses on the third-body particles and their effect on tribology and corrosion processes to themselves and the bearing surfaces. A friction hip simulator was used, integrated with an electrochemical cell to study the biotribocorrosion system. Pre-fabricated cobalt particles (28 nm in diam.) were employed. The diameter of all femoral heads involved in this study was 36 mm. The open circuit potential (OCP) was monitored with and without these nano-size Co particles. After each test, particles were isolated and observed via TEM (Transmission Electron Microscopy). ICP-MS (Inductively Coupled Plasma Mass Spectroscopy) was used to quantify the released metal ions. The friction factor and the rate of metal ion release were influenced by the added nanoparticles and in this paper the role of nanoparticles in the biotribocorrosion process is discussed.

Understanding polyethylene wear mechanisms by modeling of debris size distributions

The bioreactivity of UHMWPE (PE) wear debris from artificial hip joints can result in considerable bone loss. Even with four decades of study a better understanding is needed for the debris/wear relationships. Therefore, we developed a methodology and mathematical model to represent the size distributions for polyethylene (PE) wear debris from hip simulator models. Since the diameter of a debris particle represents a positive number, only distributions bounded by 0 and ∞ were investigated. Also, the model needed to fit the distributions for both the particle number and particle volume fractions. Single and mixture distribution schemes were examined. Debris data from PE hip simulator wear studies of crosslinking and surface roughness effects were used to evaluate the models. Single, uni-modal distributions did not adequately represent the number or volume fraction data. A mixture distribution model best represented the size distributions for both number and volume fractions. Crosslinking and surface roughness affects were reflected in the model with specific regions of the debris distribution (sub-distributions) being influenced more than others. For the first time it has been demonstrated that wear debris data is more complex than it appears. Debris morphology data represents several processes and a factor such as crosslinking PE or changing the counterface surface roughness may be reflected only in a small proportion of the total data set.

Application of principal component analysis and a fuzzy C-means clustering algorithm to wear debris morphology classification

The application of principal component analysis (PCA) and fuzzy C-means clustering algorithm to the classification of ultrahigh molecular weight polyethylene (UHMWPE) wear debris from artificial joints has been described in this article. Wear particles were extracted and isolated from peri-prosthetic tissues collected during revision surgery, which was revised for loosening. The implant life of the hip prosthesis was 12 years. The particles were examined by scanning electron microscopy. Digitized particle images were analysed on a computer by specially developed software ‘Image-Pro Plus’. The following 19 numerical descriptors were used to characterize the particles: particle area, length, width, perimeter, boundary fractal dimension, and shape parameters such as form factor, roundness, convexity, aspect ratio, and others. PCA algorithm was applied to reduce the amount of parameters to simplify the following calculation. Furthermore, main factors and important parameters such as mean diameter, equivalent circle diameter, and perimeter were found out by PCA. However, C-means clustering algorithm was applied to classify the UHMWPE wear debris into 4–7 clusters. The Xie—Beni index was introduced to determine the optimal number of clusters and illuminate the clustering validity. The result of the calculation indicates that five clusters is the optimal clustering number. The feature of the debris in each cluster is also described in this article.

Migration of wear debris of polyethylene depends on bone microarchitecture

The mechanism of hip arthroplasties loosening is related to the migration of wear debris throughout the implant environment. In vivo, polyethylene particles (PE) were shown to infiltrate the bone implant interface and the medullary spaces of the cancellous bone. Our test hypothesis was that polyethylene particle migration is correlated to bone porosity. Bone samples with a high or low trabecular volume and microarchitecture were harvested in 20 calves and 20 human cadavers. They were extensively washed to remove marrow cells. Bone cylinders were filled with a light-curing monomer having the same viscosity as bone marrow. PE particles (7 and 33 microm) were deposited at the surface of the polymer. The bone cylinders were agitated during 7 days on an orbital shaker and the gel was left to polymerize at day light. X-ray microtomography was performed to characterize bone volume and microarchitecture. Cylinders were sectioned and observed under polarized light. The migration distance and rate were determined. Migration of PE particles strongly depended on trabecular bone volume and microarchitecture. We found a linear relationship (r = 0.61) between speed migration and bone volume and an exponential relationship between speed migration and bone architecture. The present in vitro model confirmed our hypothesis about the key role of bone microarchitecture in the migration of large PE wear particles. This is an explanation for the development of inflammatory reaction at distance from a prosthesis although our study did not include submicron particles.

Metal Ion Measurement as a Diagnostic Tool to Identify Problems with Metal-on-Metal Hip Resurfacing

De Smet, K. MD1; De Haan, R. MD2; Calistri, A. MD1; Campbell, P.A. PhD3; Ebramzadeh, E. PhD3; Pattyn, C. MD4; Gill, H.S. DPhil5 Author Information