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Query: UNIPROT:P50502 (Hip)
 7,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Femoral component fracture is a documented but an uncommon complication of total hip arthroplasty. A retrospective survey conducted by the American Association of Hip and Knee Surgeons estimated the prevalence of femoral component fractures at 0.27% (172 of 64483 implants over a 5-year period ending in 1993) . There have been several case reports of fatigue fractures of the prosthetic neck distal to the Morse taper in modular implants with a cobalt alloy head and a cobalt alloy stem. Here, we present a case report of stem fracture within the Morse taper of a cobalt alloy stem coupled with a cobalt alloy head.
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PMID:Trunion fracture of a fully porous-coated femoral stem. Case report. 1623 Feb 51

Highly cross-linked ultra-high molecular weight polyethylene (UHMWPE) decreases wear at the hip by more than 50% compared with conventional UHMWPE. However, melted highly cross-linked polyethylene may be susceptible to fatigue cracking, and annealed highly cross-linked polyethylene may be susceptible to in vivo oxidation. The second-generation highly cross-linked UHMWPE (X3 HXPE) uses a sequential irradiation and annealing process. It preserves mechanical strength properties and has the highest survivorship in functional fatigue testing. The free radical content is low, and its performance under accelerated aging is the same as virgin UHMWPE. Hip simulator studies with 32-mm acetabular components demonstrated 97% wear reduction compared with conventional UHMWPE, and 62% compared with a clinically successful first-generation annealed highly cross-linked polyethylene. The crystallinity, density, and tensile strength of the X3 HXPE material was unchanged by oxidative challenge. X3 HXPE material articulating on cobalt-chromium alloy yields a volumetric wear rate very similar to that of metal-on-metal articulations, but eliminates the concerns of metal ion release. Wear particles generated from the X3 HXPE were the same size as those produced from conventional UHMWPE. Preliminary results suggest X3 HXPE can be used for cups larger than 36 mm.
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PMID:The basis for a second-generation highly cross-linked UHMWPE. 1701 28

Many techniques have been advanced to achieve reliable femoral stem fixation in revision total hip arthroplasty. In a cross-sectional study, we compared quality of life in 220 patients with two femoral stem designs: a modular tapered and fluted titanium stem design and a cylindrical extensively coated chrome-cobalt stem with single modularity (head size and neck length alone). We matched cohorts based on age decade and gender. The minimum followup was 1 year with a median of 2 years. Subjective outcome assessment and patient satisfaction were measured using the WOMAC Osteoarthritis Index, the Oxford Hip Score, the SF-12, and the Arthroplasty Satisfaction Scale. At followup, all quality of life measures favored the tapered titanium stem. WOMAC pain, function, and overall scores all were higher in this group. The Oxford Hip Score and the Satisfaction score reflected a greater difference in outcome between the two stem designs. We presume reduced stiffness of the titanium stem, coupled with the intraoperative modularity, resulted in the improved patient outcomes observed in this study.
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PMID:Improved outcome in femoral revision arthroplasty with tapered fluted modular titanium stems. 1731 93

High levels of cobalt and chromium ions are detected in the blood and urine of patients with metal-on-metal (MoM) hip replacement. These elements are released as a result of wear at the bearing surfaces. Wear rates depend on a multitude of factors, which include the bearing geometry, carbon content, manufacturing processes, lubrication, speed and direction of sliding of the surfaces, pattern of loading, and orientation of the components. In-vivo wear of MoM bearings cannot be reliably measured on X-rays because no distinction can be made between the bearing surfaces. Hip simulator studies have shown that wear rates are higher during the initial bedding-in phase and subsequently drop to very low levels. Accordingly, metal ion levels would be expected to decrease with the use of the bearing, measured as implantation time following surgery. However, several clinical studies have found that metal ion levels either gradually rise or fluctuate instead of decreasing to lower levels. Moreover, hip simulator studies predict that large-diameter bearings have lower wear rates than small-diameter bearings. In clinical studies, however, metal levels in patients with large-diameter bearings are unexpectedly higher than those in patients with small-diameter bearings. As a consequence, high cobalt ion levels in patients do not necessarily imply that their MoM bearings produce much wear debris at the time that their levels were measured; it may simply be due to accumulation of wear debris from the preceding time. Exercise-related cobalt rise may overcome this limitation and give a better assessment of the current wear status of a MoM bearing surface than a measure of cobalt levels only.
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PMID:Can cobalt levels estimate in-vivo wear of metal-on-metal bearings used in hip arthroplasty? 1816 Dec 53

Hip simulator studies have been carried out extensively to understand and test artificial hip implants in vitro as an efficient alternative to obtaining long-term results in vivo. Recent studies have shown that a ceramic-on-metal material combination lowers the wear by up to 100 times in comparison with a typical metal-on-metal design. The reason for this reduction remains unclear and for this reason this study has undertaken simple tribometer tests to understand the fundamental material loss mechanisms in two material combinations: metal-on-metal and ceramic-on-ceramic. A simple-configuration reciprocating pin-on-plate wear study was performed under open-circuit potential (OCP) and with applied cathodic protection (CP) in a serum solution using two tribological couples: firstly, cobalt-chromium (Co-Cr) pins against Co-Cr plates; secondly, Co-Cr pins against alumina (Al2O3) plates. The pin and plate surfaces prior to and after testing were examined by profilometry and scanning electron microscopy. The results showed a marked reduction in wear when CP was applied, indicating that total material degradation under the OCP condition was attributed to corrosion processes. The substitution of the Co-Cr pin with an Al2O3 plate also resulted in a dramatic reduction in wear, probably due to the reduction in the corrosion-wear interactions between the tribological pair.
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PMID:Understanding the differences between the wear of metal-on-metal and ceramic-on-metal total hip replacements. 1849 98

The most appropriate blood fraction for the measurement of metal ions in patients with metal-on-metal implants is controversial. We compared chromium (Cr) and cobalt (Co) ion levels in 29 patients after unilateral hip resurfacing with a size 54-mm femoral Birmingham Hip Resurfacing Prosthesis (Smith and Nephew, London, UK). All had well-functioning arthroplasties between 5 and 59 months after implantation. Ion levels were measured in serum, plasma, red cells, and whole blood in each patient. Our results indicate that only very minor amounts of Cr and Co are associated with red blood cells, with most being associated with serum/plasma. Previous studies using corrosion to produce the ion load have showed a predominance of Cr in the red blood cells. They have also shown that the cellular uptake of Cr is an indicator of its valence. This difference in distribution with our results is indirect evidence that the Cr released from wear of this implant is probably in the more benign trivalent form. It also suggests that most of the metal loss from a normally wearing bearing may be from wear rather than corrosion. If blood is to be used to assess rates of wear and systemic ion levels, then serum gives a better reflection of the true levels than red blood cells.
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PMID:Distribution of chromium and cobalt ions in various blood fractions after resurfacing hip arthroplasty. 1853 45

A cup inclination angle greater than 45 degrees is associated with increased wear rates of metal on polyethylene (MOP) hip replacements. The same maybe true for metal on metal (MOM) hips yet this has not been clearly shown. We measured the acetabular inclination angle from plain radiographs, and whole blood metal ion levels using Inductively Coupled Plasma Mass Spectrometry of 26 patients (mean Harris Hip Score 94 and mean time post op of 22 months) with Birmingham Hip Resurfacings. We identified a threshold level of 50 degrees cup inclination. Below this threshold, the mean whole blood cobalt and chromium were 1.6 ppb and 1.88 ppb respectively; above this threshold, the mean blood cobalt and chromium were 4.45 ppb and 4.3 ppb respectively. These differences were significant cobalt (p<0.01) and chromium (p=0.01). All patients above the threshold had metal levels greater than any of the patients below the threshold. For 14 patients, who returned one year later for a repeat blood metal level measurement, cobalt and chromium levels were very similar. The effect of an acetabular inclination angle of greater than 50 degrees on wear rates of MOM hips, as measured through blood metal ion levels, appears to be similar to that seen with MOP hips. Additionally, our new analytical methods may allow blood metal levels to be used as a realistic biomarker of in vivo wear rate of MOM hips. The implication is that metal levels can be minimised with optimal orientation of the acetabular component.
Hip Int
PMID:Cup inclination angle of greater than 50 degrees increases whole blood concentrations of cobalt and chromium ions after metal-on-metal hip resurfacing. 1892 77

Concerns now exist about the long-term biological effects of exposure to orthopaedic metal alloys, particularly serum cobalt and chromium ions derived from metal-on-metal wear debris in these patients. A pseudotumour mass complicating metal-on-metal resurfacing arthroplasty has been recognized by orthopaedic oncologists and specialist hip units. Pseudotumours may also present with a major nerve palsy. Two cases of femoral neuropathy due to pseudotumour masses caused by metal-on-metal resurfacing arthroplasty are presented. Preoperative neurophysiological studies showed severe and irreversible pathological changes to nerve function with neurohistopathological evidence of complete nerve destruction with a previously unreported pathological appearance. This may represent a previously unrecognized pathological process, possibly 'toxic' in nature, resulting from metal-on-metal wear debris. Prolonged follow-up and detailed clinical assessment of patients after hip resurfacing arthroplasty is advocated with planned and expeditious revision of any patient in whom evidence of femoral neuropathy develops.
Hip Int
PMID:The treatment of femoral neuropathy due to pseudotumour caused by metal-on-metal resurfacing arthroplasty. 1909 10

We describe the findings at six years in an ongoing prospective clinicoradiological and metal ion study in a cohort of 26 consecutive male patients with unilateral Birmingham Hip Resurfacing arthroplasties with one of two femoral head sizes (50 mm and 54 mm). Their mean age was 52.9 years (29 to 67). We have previously shown an early increase in the 24-hour urinary excretion of metal ions, reaching a peak at six months (cobalt) and one year (chromium) after operation. Subsequently there is a decreasing trend in excretion of both cobalt and chromium. The levels of cobalt and chromium in whole blood also show a significant increase at one year, followed by a decreasing trend until the sixth year.
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PMID:Six-year results of a prospective study of metal ion levels in young patients with metal-on-metal hip resurfacings. 1919 49

Bearings made of ceramics have ultra-low wear properties that make them suitable for total hip arthroplasty (THA) and total knee arthroplasty (TKA). When compared to cobalt chrome (CoCr)-on-polyethylene (PE) articulations, ceramics offer drastic reductions in bearing wear rates. Lower wear rates result in fewer wear particles produced by the articulating surfaces. In theory, this should reduce the risk of periprosthetic osteolysis and premature implant loosening, thereby contributing to the longevity of total joints. In addition to ceramics, other alternative bearing couples, such as highly cross-linked PE (XLPE) and metal-on-metal also offer less wear than CoCr-on-PE articulations in total joint arthroplasty. Alumina and zirconia ceramics are familiar to orthopaedic surgeons since both materials have been used in total joints for several decades. While not new in Europe, alumina-on-alumina ceramic total hips have only recently become available for widespread use in the United States from various orthopaedic implant manufacturers. As the search for the ideal total joint bearing material continues, composite materials of existing ceramics, metal-on-ceramic articulations, and new ceramic technologies will offer more choices to the arthroplasty surgeon. The objective of this paper is to present an overview of material properties, clinical applications, evolution, and limitations of ceramic materials that are of interest to the arthroplasty surgeon.
Hip Int
PMID:A review of ceramic bearing materials in total joint arthroplasty. 1919 39


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