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Biomedical subjects

B M Wroblewski

Publications and source records attributed to B M Wroblewski.

At least 37 records · Page 2Linked to original sources
PubMed2001

The effect of activity levels of total hip arthroplasty patients on socket penetration.

Survivorship of total hip arthroplasties (THAs) has been linked to penetration of the femoral head into the polyethylene acetabular cup and to polyethylene wear. The activity level of patients with THAs is considered to be an important factor affecting wear, and the purpose of this study was to explore the relationship between activity as recorded by pedometers and cup penetration. The measurement of daily activity levels of normal subjects and THA patients of various ages are discussed in another article ([1]). Subjects were monitored continuously during 2- to 4-week periods using simple pedometer devices. Patients (n = 54; mean age, 58 years) from the Centre for Hip Surgery at Wrightington Hospital for whom the penetration data also were available were included in the study. The average activity level for the patient group was 1.426 million loading cycles on each hip joint per year. Radiographic penetration measurements were compared for 81 hips in 54 patients with a mean follow-up of 13.1 years (range, 1.3-26.4 years). The overall correlation of penetration with implantation period is known to be poor, however, and did not improve significantly when the penetration was plotted against a new parameter that took account of not only implant life, but also the level of activity and patient weight. The considerable scatter of penetration levels was noted to increase with increasing implantation period, which indicates that in the multifactorial problem of polyethylene wear, other factors, particularly femoral head surface finish or polyethylene deterioration, may predominate.

Acetabulum↗
PubMed2001

Comparative study of the activity of total hip arthroplasty patients and normal subjects.

The walking activity of normal subjects and total hip arthroplasty (THA) patients from the Wrightington Hospital for Joint Disease and The General Infirmary at Leeds was assessed by means of electronic pedometers. The principal objectives were to establish the extent to which joint arthroplasty patients recover their activity relative to normal subjects and to establish the number of loading cycles to which prostheses should be subjected in joint simulator studies of implant performance. A further objective was to establish an experimental procedure for the assessment of the role of activity in contributing to the well-known scatter in the measurements of femoral head penetration into acetabular cups in in vivo studies of implant performance. The last-mentioned issue is addressed in another article ([1]). The walking activity of 2 normal subjects of disparate ages was assessed during 1 full year. It was concluded that fair estimates of activity could be achieved by recording pedometer readings during successive 2- to 4-week periods. This approach was adopted in the full assessment of the walking activity of cohorts of normal subjects and THA patients. Linear regression expressions relating the number of steps taken daily and the annual number of loading cycles on each leg to age are presented for normal subjects and THA patients. In all cases, activity declines with age, but it is shown that total joint arthroplasty is not at all restrictive on walking activity-a remarkable testimony to the efficacy of total joint arthroplasty. Attention is drawn, however, to different levels of activity of THA patients recorded in the present United Kingdom study and a similar survey conducted in California.

Activities of Daily Living↗
PubMed2001

A comparison of the wear and physical properties of silane cross-linked polyethylene and ultra-high molecular weight polyethylene.

Cross-linked polyethylenes are being introduced widely in acetabular cups in hip prostheses as a strategy to reduce the incidence of wear debris-induced osteolysis. It will be many years before substantial clinical data can be collected on the wear of these new materials. Silane cross-linked polyethylene (XLPE) was introduced into clinical practice in a limited series of acetabular cups in 1986 articulating against 22.225-mm alumina ceramic femoral heads and showed reduced wear rates compared with conventionally sterilized (gamma irradiation in air) ultra-high molecular weight polyethylene (UHMWPE). We compared the wear of XLPE manufactured in 1986 with the wear of UHMWPE manufactured in 1986 in nonirradiated and irradiated forms. In the nonirradiated forms, the wear of XLPE was 3 times less than UHWMPE when articulating against smooth counterfaces. The nonirradiated materials did not show signs of oxidation. In the irradiated forms, only UHMWPE showed high levels of oxidation, and this caused a substantial increase in wear. Antioxidants added to XLPE during processing gave resistance to oxidative degradation. When sliding against scratched counterfaces, the wear of UHMWPE increased by a factor of 2 to 3 times. Against the same scratched counterfaces, the wear of XLPE increased dramatically by 30 to 200 times. This difference may be attributed to the reduction in toughness of XLPE. Clinically, XLPE has been articulated against damage-resistant ceramic heads, and this probably has been an important factor in contributing to reduced wear. New cross-linked polyethylenes differ considerably from XLPE. This study indicates that it is prudent to examine the wear of new polyethylenes under a range of conditions that may occur in vivo.

Analysis of Variance↗
PubMed2001

Triple taper polished cemented stem in total hip arthroplasty: rationale for the design, surgical technique, and 7 years of clinical experience.

Successful long-term clinical results with the Charnley low-friction torque arthroplasty have identified proximal femoral strain shielding as a long-term problem to be addressed. The problem has arisen because of the load transfer by a distally supported stem that is no longer subject to fracture. To overcome this problem and improve proximal load transfer to the femur, a continuous triple-tapered stem--the C stem--was designed. This article describes the first 500 primary hip arthroplasties at a mean follow-up of 3 years, 5 months (range, 1-7 years). There have been no revisions for aseptic stem loosening, and no stem is considered to be at risk for loosening. In 20% of cases, there was subjective radiologic improvement of the bone-cement interface.

Adolescent↗
PubMed2001

Incidence of loose bodies in an osteoarthritic hip.

In a prospective study of 75 consecutive primary Charnley low friction arthroplasties carried out for osteoarthritis, loose bodies were found in nine hip joints; an incidence of 12%. Whether their presence is the cause or the effect of the condition remains unclear. Their discoid or spherical shape suggests that they were free and had been subjected to sliding or rolling motion. Those of irregular shape may have remained partly attached within the capsule, or become confined to a space.

Adult↗
PubMed2000

Evaluation of the response of primary human peripheral blood mononuclear phagocytes to challenge with in vitro generated clinically relevant UHMWPE particles of known size and dose.

The response of primary human peripheral blood mononuclear phagocytes to challenge with clinically relevant ultra-high molecular weight polyethylene (UHMWPE) wear debris of known particle size and dose was evaluated. Particles with a mean size of 0.24, 0. 45, 1.7, 7.6, and 88 microm were cocultured with cells for 24 h before assessment of cell viability and production of the osteolytic cytokines interleukin (IL)-1 beta, IL-6, tumor necrosis factor-alpha, and granulocyte macrophage colony-stimulating factor, and prostaglandin E(2). All particle fractions were evaluated at particle volume (microm(3)) to cell number ratios of 10:1 and 100:1, which had been previously identified as being the most stimulatory and clinically relevant. None of the test fractions had an effect on cell viability. Whereas the heterogeneity of human individuals was clearly evident in the responses of the donors evaluated in this study (the response of donor 3 was between 5 and 20 times greater than the other donors), the most biologically active particles were found to be submicrometer in size. Stimulation with phagocytosable particles (0.24, 0.45, and 1.7 microm) resulted in enhanced levels of cytokine secretion. Macrophages stimulated with particles outside this size range produced considerably less cytokines at the volumes tested. These results confirm earlier findings and suggest that the size and volume of UHMWPE particles are critical factors in macrophage activation. Furthermore, they suggest that the heterogeneity of human individuals may be another important factor in determining implant life.

Biocompatible Materials↗
PubMed2000

Comparison of the response of primary human peripheral blood mononuclear phagocytes from different donors to challenge with model polyethylene particles of known size and dose.

The response of primary human peripheral blood mononuclear phagocytes to challenge with polyethylene particles of known size and dose was evaluated. Particles with mean sizes of 0.21, 0.49, 4.3, 7.2, and 88 microm were co-cultured with cells for 24 h prior to the assessment of cell viability and production of the osteolytic mediators IL-1beta, IL-6, TNFalpha, GM-CSF and PGE2. All particle fractions were evaluated at particle volume (microm3) to cell number ratios of 10:1 and 100:1 which were previously identified as being the most biologically active and clinically relevant. The heterogeneity of human individuals was clearly evident both in the profile and the magnitude of the response of the donors evaluated in this study (the response of donor 5 being 2- to 15-fold lower than that of the other donors). Only the sub-micrometre particles stimulated significantly enhanced cytokine secretion at the ratios tested: mean particle sizes of 0.49 and 0.21 microm being the most biologically active. Macrophages stimulated with particles outside this size range produced considerably lower levels of mediator. These results compared favourably with the results of earlier studies, which demonstrated that particles within the phagocytosable size range (0.1-10 microm) were the most biologically active. These results, therefore, confirm earlier findings and suggest that the size and volume of polyethylene particles are critical factors in macrophage activation. Furthermore, they suggest that the heterogeneity of human individuals may be another important factor in determining implant life and could provide the basis for a valuable diagnostic tool to identify those patients most at risk of implant loosening.

Blood Donors↗
PubMed2000

Quantitative analysis of polyethylene wear debris, wear rate and head damage in retrieved Charnley hip prostheses.

Submicrometer- and micrometer-sized ultra-high molecular weight polyethylene (UHMWPE) wear particles have been associated with osteolysis and failure of total artificial joints. Previous studies have isolated predominantly submicrometer-sized particles at the expense of larger particles (>10 microm). This study aimed to isolate and characterize quantitatively all sizes of UHMWPE wear particles generated in 18 Charnley hip prostheses. In addition, to analyze the wear debris with respect to the total volumetric wear of the cup and damage to the femoral head. Particle size distributions ranged from 0.1 to ->1000 microm. A significant proportion (3-82%) of the mass of the wear debris isolated was>10 microm. The mode of the frequency distribution of the particles was in the range 0.1-0.5 microm for all patients. However, analysis of the mass of wear debris as a function of its size allowed differentiation of the wear debris from different patients. Femoral head damage was associated with high volumetric wear and increased numbers of biologically active submicrometer-sized particles.

Journal Article↗
PubMed2000

Fatal pulmonary embolism and mortality after revision of failed total hip arthroplasties.

To assess the effect of extensive surgery and delayed mobilization on postoperative incidence of fatal pulmonary embolism, we reviewed the mortality rate in 1,294 patients undergoing 1,483 revisions of failed total hip arthroplasties, in which mobilization of the patients was delayed for up to 3 weeks. There were 6 deaths (mortality rate, 0.4%). All were submitted to autopsy; only 1 death was the result of pulmonary embolism. The results of our review do not support the view that more extensive surgery and delayed mobilization of the patient, as in revision of failed total hip arthroplasties, carries a high incidence of fatal pulmonary embolism.

Arthroplasty, Replacement, Hip↗
PubMed2000

Influence of gelatin and bovine serum lubricants on ultra-high molecular weight polyethylene wear debris generated in in vitro simulations.

Ultra-high molecular weight polyethylene (UHMWPE) wear debris induced osteolysis has a major role in the late aseptic loosening and ultimate failure of total hip replacements (THR). Clinically relevant in vitro simulations of wear are essential to predict the osteolytic potential of bearing surfaces in artificial hip joints. Newborn calf or bovine serum has been accepted as a boundary lubricant for such in vitro tests, but its biological stability has been questioned. This study compared the wear factors, number of wear particles and levels of microbial contamination produced in bovine serum and a gelatin-based lubricant. The wear factors produced by the two lubricants were not significantly different, however the wear debris morphology produced was substantially different. The bovine serum became contaminated with micro-organisms within 28 h, whereas the protein-based lubricant remained uncontaminated. The results showed that bovine serum was not a stable boundary lubricant. They also showed that although the wear factors for the two solutions were not significantly different, the protein-based lubricant was not a suitable alternative to bovine serum because the wear debris produced was not clinically relevant.

Animals↗
PubMed2000

Charnley low-friction arthroplasty with an autograft of the femoral head for developmental dysplasia of the hip. The 10- to 15-year results.

Between 1983 and 1988 we carried out 45 Charnley low-friction arthroplasties with autografts from the femoral head in 41 patients for developmental dysplasia of the hip. The preoperative radiographs were assessed for the severity of DDH according to the classifications of Crowe et al, Hartofilakidis et al and Sharp. The postoperative and follow-up radiographs were analysed for coverage of the socket by the graft, for loosening and for the outcome of the fixation of the bone graft. Two patients died (two hips) at four and seven years after THR from causes unrelated to the surgery and were excluded from the final radiological analysis. The mean age of the patients at the time of operation was 46 years 3 months. The autograft of the femoral head covered a mean 26% (16 to 35) of the acetabular component. All the grafts united. Some degree of resorption of the bone graft occurred in 27 patients, and always involved the lateral part of the graft, which was beyond the margin of the socket. After a mean follow-up of 11 years there had been no revisions and 38 patients had no pain or only slight discomfort. One socket migrated and four others were fully demarcated. Our findings indicate that the Charnley LFA with an autograft of the femoral head for DDH remains successful at a follow-up of 15 years.

Adult↗
PubMed2000

Revision of failed total hip arthroplasty with a proximal femoral modular cemented stem.

We have designed a modular cemented femoral component for revision of failed total hip arthroplasty in which deficiency of the proximal femur is such as to require a variable extrafemoral portion of the stem. We present the results of the first 74 operations in 72 patients; 56 of the patients had grade-3 or grade-4 femoral deficiency as defined by Gustilo and Pasternak and 24 had fractures of the proximal femur, of which 22 were periprosthetic. There was or had been infection in 19 hips. At a mean follow-up of 5 years 9 months (1 to 12 years) nine stems were radiologically loose of which three had been revised. There were no failures in 45 cases in which there was fixation of the distal stem of 10 cm or more. Dislocation occurred in nine patients and there were four cases of infection in the 19 which were, or had been, infected previously. There were no neurovascular complications and no intraoperative femoral fractures. The femoral bone stock improved radiologically in 45 hips of which 29 showed considerable reformation of the proximal femur; 27 remained unchanged and two showed increasing osteoporosis.

Adult↗
PubMed2000

The calcar femorale in cemented stem fixation in total hip arthroplasty.

The calcar femorale is a vertical plate of bone lying deep to the lesser trochanter and is formed as a result of traction of the iliopsoas which separates the femoral cortex into two distinct layers, the calcar femorale and the medial femoral cortex. They fuse together proximally to form the medial femoral neck. A stem placed centrally will abut against the calcar femorale with little or no space for cement. Clearing of the calcar will offer space for a cement layer, which will support the stem proximally on the posterior aspect. We compared two consecutive groups of Charnley low-friction arthroplasties, with and without clearing of the calcar. In 330 patients who had an arthroplasty without clearing the calcar, there were ten revisions for aseptic loosening of the stem and six other stems were considered 'definitely loose', giving a rate of failure of 4.8%. In 111 patients in whom the calcar was cleared there was only one revision for aseptic loosening and no stems were classed as 'definitely loose', giving a rate of failure of 0.9%. Survivorship analysis has again shown the need for long-term follow-up; the differences became clear after ten years but because of the relatively small numbers, statistical analysis is not yet applicable. We now clear the calcar femorale routinely and advocate optimal access to the medullary canal and insertion of the stem in the area of the piriform fossa.

Adolescent↗
PubMed2000

Comparison of the response of primary murine peritoneal macrophages and the U937 human histiocytic cell line to challenge with in vitro generated clinically relevant UHMWPE particles.

The response of primary murine macrophages and the U937 human histiocytic cell line to challenge with clinically relevant UHMWPE wear debris of known particle size and dose was evaluated. Particles with mean sizes of 0.24, 0.45, 1.71, 7.62 and 88 microm were co-cultured with cells for 24 hours prior to assessment of cell viability and production of the osteolytic mediators IL-1beta, IL-6, TNFalpha and, in supernatants from murine phagocytes, PGE2 and GM-CSF. All particle fractions were evaluated at particle volume (microm3) to cell number ratios of 10 : 1 and 100 : 1 (and, additionally, 0.1 : 1 and 1 : 1 for U937 cells). These ratios had previously been identified as the most stimulatory and clinically relevant. Although the results for the cell line were highly variable, stimulation with phagocytosable particles (range 0.1 to 15 microm) resulted in enhanced levels of cytokine secretion by both murine macrophages and U937 histiocytes. The most biologically active particles were sub-micrometre in size. However, U937 cells responded to wear debris at much lower particle volume to cell number ratios (>0.1 microm3 per cell) than the murine cells (> 10 microm3 per cell). No GM-CSF was produced by particle or LPS stimulated murine macrophages. Similarly, U937 histiocytes failed to secrete any IL-1beta. Neither macrophage population responded to stimulation with the largest (88 microm) particles. These results confirm earlier findings and suggest that the size of UHMWPE wear particles is a critical factor in macrophage activation. Moreover, primary murine macrophages have been demonstrated to be a suitable model for studying cell-particle interactions in vitro.

Animals↗