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Biomedical subjects

L Lidgren

Publications and source records attributed to L Lidgren.

At least 55 records · Page 3Linked to original sources
PubMed1995

Effects of particulate high-density polyethylene and titanium alloy on tissue ingrowth into bone harvest chamber in rabbits.

The purpose of this study was to determine whether small, phagocytosable particles of titanium alloy (Ti) and high-density polyethylene (HDPE) have an adverse effect on bone ingrowth. The bone harvest chamber (BHC) was implanted bilaterally in the proximal tibial metaphysis of six mature rabbits. The BHC has a transverse 1-mm wide pore providing a continuous canal through the chamber for tissue ingrowth. After an initial 6-week period for osseointegration of the BHC, the contents of the canal were harvested repeatedly at 3 weekly intervals. This could be done with the chamber in place, without disturbing its exterior surface or the surrounding bone. The carrier solution, 1% sodium hyaluronate (Healon) was implanted first. In subsequent implantations, Healon was mixed with particles of HDPE or Ti averaging 4.7 +/- 2.1 and 3.0 +/- 2.6 microns, respectively. The contralateral chamber was left empty and served as a control. The chambers were harvested repeatedly, alternating experimental and control sides. The sections from the control side, and those containing Healon alone demonstrated extensive trabecular bone in a fibrovascular stroma. The sections containing Ti alloy particles were qualitatively and quantitatively similar to the control sections and those containing Healon, except for the presence of small black granules of Ti alloy, dispersed in the fibrovascular stroma or phagocytosed by scattered macrophages. The sections containing HDPE particles were infiltrated and engulfed by mononuclear and multinuclear histiocytic cells in a highly fibrous stroma. The majority of the multinucleated cells present were interpreted as being foreign body giant cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alloys↗
PubMed1995

Does vacuum mixing of bone cement affect heat generation? Analysis of four cement brands.

Four different brands of bone cement (Palacos R, Simplex P, Sulfix, CMW 1) were tested for exothermic changes during polymerization at atmospheric pressure and under partial vacuum of 0.2 bar. Palacos R was also mixed at four pressure levels (1.0, 0.2, 0.12, and 0.05 bar). The peak temperature in the bone cement was 46 to 124 degrees C, depending on the measuring point. There was no difference in peak temperature or duration of temperature increase above 50 degrees C during the curing of cement whether mixed at atmospheric pressure or under partial vacuum at different pressure levels.

Biocompatible Materials↗
PubMed1995

Intermittent micromotion and polyethylene particles inhibit bone ingrowth into titanium chambers in rabbits.

We performed a histomorphological and morphometric analysis of the effects of short daily periods of micromotion and phagocytosable particles of high density polyethylene (PE) on bone ingrowth into a 1 x 1 x 5 mm canal within a titanium chamber in rabbits. The micromotion chamber (MC) was implanted in the tibia of nine mature New Zealand white rabbits. After osseointegration and first harvest of tissue, 40 micromotions (amplitude = 0.5 mm) were applied daily at a rate of 1 Hz for a 3-week period. The tissue within the chamber was then harvested. For the second treatment, PE particles (10(8)/mL) were placed within the canal. The tissue in the chamber was harvested 3 weeks later. The next treatment was a 3-week rest period, in which neither micromotion nor particles were utilized; a harvest followed. The final treatment combined PE particles and micromotion, followed by a harvest 3 weeks later. Sections from control harvests contained extensive trabecular bone arranged longitudinally throughout the canal in a fibrovascular stroma. Micromotion produced longitudinally oriented fibrous tissue within the chamber. PE particles were associated with macrophages, surrounding and engulfing the birefringent particles. The combination of particles and micromotion produced a fibrous stroma laden with macrophages. PE particles and micromotion, alone or together, produced a similar effect in inhibiting bone ingrowth, compared to nonmoved chambers without particles. In this short-term experiment, no additive or potentiating effect of these two stimuli could be demonstrated.

Animals↗
PubMed1995

Oxford meniscal bearing knee versus the Marmor knee in unicompartmental arthroplasty for arthrosis. A Swedish multicenter survival study.

In the Swedish Knee Arthroplasty Study, all 699 Oxford meniscal bearing cemented unicompartmental prostheses (Biomet, Bridgend, UK) were identified and analyzed regarding failure pattern and compared with all Marmor prostheses (Smith & Nephew Richards, Orthez, France) and with a time-, age-, and sex-matched subset of Marmor prostheses using survival statistics expressed as cumulative revision rates. After 1 year there was already a higher rate, and after 6 years the rate of the Oxford group was more than twice that of the Marmor group. There were 50 revisions in the Oxford group: dislocating meniscus in 16, loosening of the femoral component in 6, tibial component in 4, both components in 4, contralateral arthrosis in 10, infection in 4, and technical failure with instability, pain, and/or impingement of the meniscal bearing anterior in the femoral condyle in 6. It is still unclear if the design with the sliding menisci will, in the long turn, reduce wear and loosening, thereby compensating for the initially inferior results. It is recommended that until this question is clarified, the Oxford knee should be used on a limited scale for long-term comparative studies only.

Adult↗
PubMed1995

Tissue ingrowth and differentiation in the bone-harvest chamber in the presence of cobalt-chromium-alloy and high-density-polyethylene particles.

Particulate wear debris from joint replacements has been implicated in the etiology of periprosthetic bone resorption. However, the effect of high-density-polyethylene or cobalt-chromium-alloy particles on osteoclastic bone resorption in vivo has not been studied previously, to our knowledge. Therefore, we examined the effect of these particles on tissue ingrowth, net bone formation (per cent trabecular bone), and osteoclastic bone resorption (osteoclasts per unit of bone surface) with use of a bone-harvest chamber that had a transverse one-millimeter channel for tissue ingrowth. After an initial six-week period for incorporation of the chamber into the proximal part of the tibia of rabbits, the contents of the channel were harvested repeatedly at three-week intervals. The carrier solution, 1 per cent sodium hyaluronate, was implanted first. In subsequent implantations, the hyaluronate was mixed with high-density-polyethylene or cobalt-chromium particles at concentrations of 10(8) particles per milliliter. The tissue harvested from the chambers that contained no particles was composed of longitudinally oriented trabecular bone in a fibrovascular stroma. Particulate high-density polyethylene evoked a moderate foreign-body reaction and a chronic inflammatory response and decreased net bone formation. When cobalt-chromium particles had been implanted, the tissue exhibited a more florid foreign-body reaction and a chronic inflammatory response, often in a nodular arrangement, in a background of dense connective tissue. Bone was sparse, and areas of cell necrosis and hyaline degeneration were noted. Histomorphometric analyses were carried out to determine the amount of net bone formation and osteoclastic bone resorption in the presence or absence of high-density-polyethylene or cobalt-chromium particles. The amount of bone was greatest in the control specimens, moderately decreased in the presence of high-density-polyethylene particles, and greatly decreased in the presence of cobalt-chromium particles. The number of osteoclasts in Howship lacunae per unit of trabecular bone surface was increased in the presence of high-density polyethylene, indicating that these particles stimulate osteoclastic bone resorption.

Animals↗
PubMed1995

Early migration of femoral components revised with impacted cancellous allografts and cement. A preliminary report of five patients.

We report the preliminary findings of the use of roentgen stereophotogrammetric analysis to evaluate the early migration of five femoral components after revision for mechanical loosening using impacted cancellous allograft and cement. All hips were examined at one week, four to six months and one year after surgery. All the components subsided by 0.4 to 4.9 mm during the first year. In four hips the prosthetic head was displaced 1.1 to 6.9 mm posteriorly. Fixation of the femoral components was less secure than after primary arthroplasty but the incidence and magnitude of early migration were similar to those after revision with cement alone.

Aged↗
PubMed1994

The Swedish knee arthroplasty register. A nation-wide study of 30,003 knees 1976-1992.

1976 through 1992, 30,003 primary knee arthroplasties and their revisions have been recorded in a nation-wide Swedish study. We report on the structure of the register, demographic data and survivorship. We found that operations for osteoarthrosis (OA) counted for the increase in number of arthroplasties in contrast to rheumatoid arthritis (RA), where the number had slightly declined. For primary operations, the total knee prostheses have practically eliminated other types in RA and are steadily gaining popularity in OA at the expense of the unicompartmental prostheses. Total knee replacements showed gradually improving survival even in unchanged designs while the unicompartmental prostheses don't, partly because of newly introduced inferior designs. We also found that failed unicompartmental prostheses were best replaced with a tricompartmental prosthesis and that a total revision was to be preferred when a tricompartmental tibial component failed. The risk of the most devastating complications, e.g., infection, leading to extraction of the prosthesis or arthrodesis has decreased considerably also in the last years.

Adult↗
PubMed1994

Assessment at CT of the rheumatoid shoulder with surgical correlation.

Eleven shoulders in 10 patients with rheumatoid arthritis were examined by conventional radiography and CT prior to cup hemiarthroplasty of the humeral head and the results were compared with the surgical findings. There was good agreement between preoperative CT and surgical findings. Humeral head cavities and erosions, with cortical boundaries, could be seen more accurately at CT than at conventional radiography. The HU of their contents corresponded to those of soft tissue, being granulomatous in nature at surgery. In 8 humeral heads CT disclosed large areas of fatty degeneration of bone marrow with HU between -10 HU and -76 HU that were not visible on the conventional radiographs. These "fatty cysts" had no cortical boundaries, unlike inflammatory granulomas, but both lesions may influence the surgical approach to hemiarthroplasty.

Adult↗
PubMed1993

Porosity of bone cement reduced by mixing and collecting under vacuum.

Palacos R bone cement was mixed in a commercial vacuum mixing system (MITAB), and in an experimental system allowing evacuating air from the powder before mixing and collecting the cement under partial vacuum. The effect on the porosity of mixing at different pressure levels was tested. The effect of evacuating air from the powder before mixing was also analyzed. The numbers and sizes of the voids in the cement samples were measured in radiographs and under the microscope. Also, the density of the cement was measured. Vacuum mixed samples had a substantial reduction of voids, as well as an increase in density compared to mixing at atmospheric pressure. After vacuum mixing and collection, a further reduction of the porosity and increased density were seen; all the large voids within the cement were eliminated at 0.05 bar absolute pressure.

Bone Cements↗
PubMed1993

Cement particles inhibit bone growth into titanium chambers implanted in the rabbit.

Particles of bone cement have been shown previously to stimulate the resorption of bone. The purpose of this study was to determine whether particles of bone cement (BC) have an adverse effect on bone ingrowth. The bone harvest chamber was implanted bilaterally in the proximal tibial metaphysis of 6 mature rabbits. Both the fixed outer cylinder and the inner removable core of the chamber have a transverse 1 mm wide pore providing a continuous canal for tissue ingrowth. After an initial 6-week period for osseointegration of the outer cylinder, the contents of the inner core were harvested repeatedly at 3 weekly intervals. In the first series of rabbits, the carrier solution, 1% sodium hyaluronate (Healon) was implanted first. In subsequent implantations, Healon was mixed with small fabricated particles of BC (averaging 3.54 mm in diameter) to fill the channel of the core. The contralateral chamber was left empty and served as a control. In the second series of rabbits, implantation was carried out sequentially using the same material bilaterally. The sections from the control harvests, and those with Healon alone contained extensive trabecular bone arranged longitudinally in the canal, in a fibrovascular stroma. The sections containing BC particles were infiltrated by foamy, mononuclear and multinuclear histiocytic cells. Less trabecular bone was seen in the sections containing BC particles compared to the control sections or those containing Healon alone. Previous studies have shown that particles of bone cement stimulate bone resorption. In this study, BC particles have also been shown to diminish the formation of new bone.

Animals↗
PubMed1993

Technetium-99m-nanocolloid scintigraphy in orthopedic infections: a comparison with indium-111-labeled leukocytes.

Twenty-three patients with clinically suspected acute or chronic osteomyelitis and 21 patients with suspected joint prosthetic infection underwent scintigraphy using both 99mTc-nanocolloid and 111In-labeled leukocytes. The scintigrams of the two tracers were blindly interpreted by three independent observers. Their evaluations showed high correspondence. Patients were classified as having no infection, probable infection or proven infection according to specific criteria which included results of bacteriological cultures and histopathological examinations. For proven and probable infection taken together, the sensitivity with 99mTc-nanocolloid was 94%, the specificity 84% and the accuracy 87%, compared with 75%, 90% and 85% with 111In-labeled leukocytes. We conclude that 99mTc-nanocolloid scintigraphy is at least equivalent with 111In-leucocyte scintigraphy, and its additional advantages are shorter examination time, less complexity and better radiation dosimetry.

Adolescent↗
PubMed1993

Reduced failure rate in knee prosthetic surgery with improved implantation technique.

From the Swedish Knee Arthroplasty project, started in 1975, types of relatively unmodified knee prostheses were chosen for analysis of time-dependent changes in the failure rate. One thousand nine hundred sixty-nine Marmor unicompartmental and 376 Total Condylar arthroplasties, all cemented, were followed until the end of 1989. The cumulative revision rates calculated with survival statistics showed a continuous improvement with time. The five-year revision rate was reduced from 11% to 5% for the Marmor prosthesis and from 10% to 2% for the Total Condylar prosthesis. This indicates that factors other than improved design are important. Such factors could include improved guide instruments, better surgical and cementing technique, influence of a learning curve, and patient selection.

Follow-Up Studies↗
PubMed1992

Polyethylene wear in unicondylar knee prostheses. 106 retrieved Marmor, PCA, and St Georg tibial components compared.

106 unicondylar knee replacement tibial components were retrieved and analyzed for the amount and type of polyethylene wear. Three different designs were retrieved which had essentially the same femorotibial conformity. Each design showed a characteristic failure pattern. The polyethylene of PCA tibial components showed serious delamination after only short durations, as a result of heat pressing. St Georg sledge prostheses showed some delamination after 4 years' duration due to sub-surface cracks which were initiated by fusion defects in the polyethylene; metal backing of the components did not affect delamination of this prosthesis. The Marmor designs showed the least wear, with shiny depressions and surface pitting; no delamination was observed in the Marmor prosthesis. Molecular weight determination by gel permeation chromatography and analysis of crystallinity using Fourier transformation infra-red spectroscopy demonstrated that St George polyethylene had higher molecular weight and crystallinity than Marmor polyethylene. In some of the components investigated, crystallinity and molecular weight of the polyethylene were reduced under the wear track when compared with the unworn polyethylene. Since fusion defects may cause delamination of polyethylene we urge manufacturers to reduce the number of such defects.

Corrosion↗
PubMed1990

Improved positioning of the femoral stem with a centralizing device.

Two series of patients operated on with total hip replacements for arthrosis are reported. The same prosthesis and operative and cementing techniques were used in both series, except that in Series 2 a centralizing device consisting of four triangular fins passed over the tip was also used to improve the positioning of the femoral stem. It was found that the position of the tip was more central in Series 2. No drawbacks were associated with the use of the device. We concluded that the centralizing device facilitated the positioning of the femoral stem tip.

Adolescent↗
PubMed1990

Hip arthroplasty infection. Current concepts.

Due to systemic or local antibiotic treatment and other preventive procedures, the incidence of deep hip-prosthetic infections in Scandinavia is less than 1 percent, with the majority hematogenous. Coagulase-negative staphylococci and anaerobes are involved in more than half of the cases. The diagnosis is sometimes difficult; preoperative aspiration often gives misleading results; and granulocyte scanning usually adds valuable information. In deep infection the current strategy is to revise with a two-stage procedure. Revisions should be carried out at specialized centers with bacteriologic competence and sufficient experience with implants.

Bacterial Infections↗