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Biomedical subjects

K G Nilsson

Publications and source records attributed to K G Nilsson.

At least 19 recordsLinked to original sources
PubMed2004

All-poly tibial component better than metal-backed: a randomized RSA study.

The quality of the fixation of the tibial component in 21 patients (23 knees) undergoing a cemented total-knee arthroplasty of the Profix design was investigated using radiostereometric analysis during 24 months. The patients were randomized to either an all-polyethylene (AP) or a metal-backed (MB) tibial component. The articulating geometry and the stem design of the implants were identical, as were the operative technique and the postoperative regimen. The results showed no negative consequences as regards fixation using AP tibial components. In all aspects, the AP components displayed magnitudes of migration on par with, or sometimes even lower than their MB counterparts. Five of 11 MB components displayed continuous migration between 1 and 2 years, compared to none of the AP implants, a finding known to be of positive prognostic significance when predicting future aseptic loosening.

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PubMed2001

No relationship between postoperative changes in bone density at the proximal tibia and the migration of the tibial component 2 years after total knee arthroplasty.

The relationship between changes in bone mineral density (BMD) in the proximal tibia and fixation of the tibial component during 2 years postoperatively was investigated in 28 knees. BMD was measured using dual-energy x-ray absorptiometry, and fixation was determined using radiostereometric analysis. BMD decreased at 3 months and returned to baseline level at 24 months, but with large variations on an individual basis. Most of the prosthetic migration occurred within the initial 3 months. The results show that the bone remodeling that occurs during the 2 years after operation has no relation to the migration of the tibial component. The early migration seems to be related more to local activities at the interface rather than to changes in BMD assessed below the interface. The changes in BMD during 2 years reflect the bone remodeling caused by the normalization of alignment after operation and are not related to the implant fixation.

Absorptiometry, Photon↗
PubMed2001

All-polyethylene versus metal-backed and stemmed tibial components in cemented total knee arthroplasty. A prospective, randomised RSA study.

We studied the quality of fixation of the tibial component using radiostereometric analysis (RSA) in 40 patients who had undergone a cemented Freeman-Samuelson total knee arthroplasty. They were prospectively randomised to either a stemmed metal-backed (MB) or non-stemmed all-polyethylene (AP) tibial component. The articulating geometry of the implants was identical, as was the operative technique and the postoperative regime. The study showed no complications of fixation using AP tibial components, and the migration was the same as that of their metal-backed counterparts. There was no bony collapse or increased subsidence of any part of the tibial component or increased incidence of radiolucent lines in the knees with AP components. Most AP implants were stable between one and two years after surgery, a finding known to be of positive prognostic significance when predicting future aseptic loosening.

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PubMed2000

Changes in bone mineral density at the proximal tibia after total knee arthroplasty: a 2-year follow-up of 28 knees using dual energy X-ray absorptiometry.

The change in bone mineral density at the proximal tibia during 2 years after total knee arthroplasty was studied in 28 knees (28 patients: 10 men and 18 women; median age: 71 years) with dual energy x-ray absorptiometry. Bone mineral density was measured at the proximal tibia at nine regions of interest below the tibial component within 1 week after the operation (baseline); measurements were repeated at 3, 6, 12, and 24 months. All but one knee was malaligned before the operation, and all but three were corrected to within the normal range of alignment after it. The mean bone mineral density of all nine regions of interest at the proximal tibia temporarily decreased by 13% (p = 0.001) during the initial 3 months, probably due to a general metabolic reaction of the skeleton to the operative trauma combined with the effect of the postoperative immobilization, and then the initial level was regained for as long as 2 years. The overall changes in mean bone mineral density to 2 years were insignificant (p > 0.05); however, a great variation (43.9% decrease to 98.0% increase) was observed on an individual basis. This change over time was significantly associated (R2 = 0.36, p = 0.002) with the level of the baseline bone mineral density, which in turn was partly related (R2 = 0.24, p = 0.009) to the amount of malalignment of the knee before the operation. Knees with high baseline levels (n = 14: 11 with varus and three with valgus alignment) displayed a decrease of 10.0 +/- 14.0% (mean +/- SD, p > 0.05) for as long as 2 years, whereas those with low baseline levels (n = 14: seven with varus and six with valgus alignment and one neutrally aligned) had an increase of 19.1 +/- 38.2% (p = 0.038). In both groups, the mean bone mineral density converged to a level of 0.75-0.95 g/cm2 at 2 years.

Absorptiometry, Photon↗
PubMed2000

The effect of the preoperative bone quality on the fixation of the tibial component in total knee arthroplasty.

The relationship between the preoperative level of bone mineral density (BMD) in the proximal tibia and the migration of the tibial component 2 years after total knee arthroplasty was investigated in 28 knees with osteoarthrosis (10 men, 18 women; mean age, 71). Sixteen components were inserted uncemented and 12 were cemented. Mean average BMD measured 10 mm below the joint level was 0.81 g/cm2 (range, 0.15-1.33 g/cm2) and was not influenced by gender, age, weight, or preoperative alignment. Local BMD measured in the medial and lateral condyles was influenced by the preoperative alignment. In knees with uncemented fixation, most of the tibial component migration (ie, subsidence and lift-off) occurred within the first months, and thereafter the implants seemed to stabilize. In the uncemented implants, there was a significant relationship between average BMD and migration (regression analysis with curve-fit estimation). The least migration was seen when average BMD was 0.6 to 1.0 g/cm2. Beyond this range, increased subsidence and lift-off was seen. There was no relationship between BMD and the change in maximum migration between 1 and 2 years postoperatively, however. In knees with cemented fixation, subsidence was initially small but continuously increasing. There were no relationships between BMD and subsidence, lift-off, and maximum migration, indicating that bone-cement can compensate for variations in bone quality, at least in the early period after operation.

Absorptiometry, Photon↗
PubMed2000

Low-conforming all-polyethylene tibial component not inferior to metal-backed component in cemented total knee arthroplasty: prospective, randomized radiostereometric analysis study of the AGC total knee prosthesis.

In a prospective, randomized study of 40 patients, the quality of fixation of cemented metal-backed versus all-polyethylene tibial components of the unconstrained anatomic graduated component total knee arthroplasty design was studied during 2 years using radiostereometric analysis (RSA). The shape, as well as the articulating geometry, of the implants was identical, as was the operative technique and the postoperative regimen. In this study, no negative consequences regarding the quality of fixation using an all-polyethylene tibial component with unconstrained articulating surfaces could be identified. In all aspects, the all-polyethylene tibial components displayed migration on par with, or sometimes lower than, their metal-backed counterparts. The rotations of the all-polyethylene components were equally low as for the metal-backed components, and maximum lift-off was significantly lower than for the metal-backed implants. We could not identify any collapse of the bone at the medial condyle or increased subsidence at the medial part of the tibia or increased rates of radiolucent lines in the knees with all-polyethylene components. All all-polyethylene implants seemed to be stable within the resolution of RSA between 1 and 2 years, a finding known to be of positive prognostic significance regarding future aseptic loosening.

Aged↗
PubMed1999

Analysis of human serum antibody-carbohydrate interaction using biosensor based on surface plasmon resonance.

Surface plasmon resonance (SPR) was used to monitor the interaction of alphaGal-antibodies from human blood group O serum with linear blood group B-saccharides, employing Galalpha1-3Galbeta1-4GlcNAc-HSA immobilised on a sensor chip surface. Strong binding of antibodies, as evident from high relative response values exceeding 200 RU, was observed. The interaction was influenced by the nature of the oligosaccharide that was added to the antibody sample prior to measurement. For example, the addition of either of the linear B-saccharides Galalpha1-3Gal and Galalpha1-3Galbeta1-4GlcNAc produced complete inhibition of antibody binding to the sensor surface, whereas the addition of the related but non-specific blood group A saccharide, GalNAcalpha1-3(Fucalpha1-2)Gal, had little effect on binding. The technique was used for the rapid monitoring of the removal of alphaGal-antibodies from human serum by affinity columns, which contained either Galalpha1-3Gal or Galalpha1-3Galbeta1-4GlcNAc as ligand. The above carbohydrates are currently evaluated as inhibitors or as affinity ligands, in the prevention of hyperacute rejection during xenotransplantation.

Antigen-Antibody Reactions↗
PubMed1999

Hydroxyapatite coating versus cemented fixation of the tibial component in total knee arthroplasty: prospective randomized comparison of hydroxyapatite-coated and cemented tibial components with 5-year follow-up using radiostereometry.

Fifty-three consecutive patients (57 knees; mean age, 69 years) entered a prospective randomized study to compare the fixation of hydroxyapatite (HA)-coated (29 knees) with cemented (28 knees) tibial components in the Tricon II total knee arthroplasty. The quality of the fixation during 5 years postoperatively was evaluated with radiostereometric analysis (RSA). Three HA-coated implants were revised: 2 owing to infection, and 1 owing to early delamination of the coating and clinical loosening. Eight patients (9 knees) died, 1 patient sustained a stroke, and 1 patient refused investigations after 1 year. In the 40 patients (19 HA-coated, 21 cemented) remaining at 5 years, the magnitude of the micromotion between the HA-coated and cemented groups did not differ. The HA-coated implants displayed most of the migration within the initial 3 months then stabilized, whereas the cemented implants showed an initially lower, but over time continuously increasing migration. Between 1 and 2 years, 4 of 24 HA-coated and 10 of 23 cemented implants migrated >0.2 mm and were categorized unstable, which has been shown to have a prognostic value as regards future aseptic loosening. Progressive radiolucent lines developed in 2 cemented knees, which both were categorized unstable. If HA-coated implants can sustain the forces that threaten the fixation in the early period after implantation, a strong and enduring fixation may be obtained.

Adult↗
PubMed1999

Stability assessment of a moderately conforming all-polyethylene tibial component in total knee arthroplasty: a prospective RSA study with 2 years of follow-up of the Kinemax Plus design.

The magnitude and pattern of the migration of an all-polyethylene tibial component with moderately conforming articular surfaces in total knee arthroplasty was analyzed in 20 patients > or =60 years during a 2-year follow-up using radiostereometry (RSA). Most of the migration occurred during the initial 4 months, whereafter the migration diminished, reaching a mean maximum migration of 0.75 mm at 2 years. Similar patterns were found for rotation of the implant. Maximum subsidence at 2 years was 0.7 mm and was most commonly located at the posteromedial part of the tibial component. These results indicate that an all-polyethylene tibial component with moderately conforming articular geometry and with a thickness of 10-12 mm demonstrated migration patterns compatible with a favorable prognosis in regard to future aseptic loosening.

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PubMed1998

Inferior performance of Boneloc bone cement in total knee arthroplasty: a prospective randomized study comparing Boneloc with Palacos using radiostereometry (RSA) in 19 patients.

We compared Boneloc bone cement with conventional cement (Palacos) in fixating the tibial component during 2-5 years in 19 patients with gonarthrosis undergoing total knee arthroplasty in a prospective randomized study. Boneloc displayed significantly larger migration, subsidence and lift-off than Palacos. The difference was identifiable already within 3 months postoperatively, but became significant at 12 months. In the Boneloc group, all components showed subsidence of the posterior part and lift-off of the anterior part of the tibial component, whereas in the Palacos group, the locations of subsidence and lift-off were evenly distributed about the edge of the implant. At 5 years, both Boneloc knees so far investigated were clinical failures with high migration rates. We conclude that, even in total knee arthroplasty, there is a substantial risk that Boneloc leads to inferior clinical results, but later than in hip replacements.

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PubMed1996

A new device combining laser Doppler perfusion imaging and digital photography.

We describe a new method for acquisition and analysis of skin perfusion images acquired by laser Doppler scanning and digital photographs of the area scanned. Photographs are obtained with a commercial digital still video camera. A commercial software package is used to handle the perfusion image file and the digital photo. We describe software developed to assess blood flow distribution in detail in relation to the visual appearance of the skin, palpatory findings and other clinical signs. Possible clinical applications of the method described by case reports are post-operative evaluation of vascularized grafts and monitoring of treatment of chronic skin ulcers.

Blood Flow Velocity↗
PubMed1995

Femoral component migration in total knee arthroplasty: randomized study comparing cemented and uncemented fixation of the Miller-Galante I design.

The Miller-Galante I knee replacement was inserted in 25 women and three men (33 knees) with osteoarthrosis. All patients received a TiAlV femoral component with a commercially pure titanium fiber-mesh undersurface. Cemented or cementless fixation was used based on a randomization protocol. Micromotions of the femoral components were recorded with roentgen stereophotogrammetric analysis during the first 2 postoperative years. The magnitude of migration did not differ between cemented and uncemented fixation. The number of nonmigrating prostheses decreased from 21 (12 cemented and nine uncemented) at 3 months to six (three cemented and three uncemented) at 24 months. In both groups, the magnitude of prosthetic tilting about the longitudinal axis (internal-external rotation) was as large as that about the transverse axis (flexion-extension). Rotation into extension was as common as rotation into flexion. The largest translations were recorded at either of the posterior condyles. In 10 uncemented components, radiolucent lines were seen at the distal interface postoperatively. Proximal migration of the femoral component was recorded in these knees, and the width of the lines decreased or the lines disappeared totally at 24 months. After 2 years, lines were noted around four cemented and four uncemented replacements, mainly anteriorly or distally. All of these prostheses migrated. One prosthesis, revised because of malalignment, displayed pronounced migration after an initial period of stability. Bone ingrowth was observed anteriorly and anterodistally despite the presence of motions of 1 mm or more.

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PubMed1994

Kinematics of successful knee prostheses during weight-bearing: three-dimensional movements and positions of screw axes in the Tricon-M and Miller-Galante designs.

Using roentgen stereophotogrammetric analysis we recorded the three-dimensional movements in six knees with implanted Tricon-M prostheses and ten knees with Miller-Galante prostheses as the patients ascended a platform. Fourteen patients with normal knees were used as controls. The two prosthetic designs displayed decreased internal tibial rotation and the Tricon-M increased valgus rotation. A central point on the tibial articular surface had a more lateral position in the Tricon-M design and a more distal one in the Miller-Galante design compared to normal knees. Increased posterior displacement with increasing flexion was observed in both designs. When the normal knees were extended at full weight-bearing the helical axes mainly shifted inclination in the frontal plane. In the prosthetic knees there was a tendency to anterior-posterior displacement of the axes as extension proceeded, especially in the Miller-Galante design. Translations along the helical axes were larger than normal in the Miller-Galante and smaller in the Tricon-M knees, reflecting differences in constraint of the two designs.

Aged↗
PubMed1994

A carbohydrate biosensor surface for the detection of uropathogenic bacteria.

We have developed a new surface for use in biosensors that is based on a gold plate covered with a specific carbohydrate receptor structure. The carbohydrate, Gal alpha 1-4Gal, was bound covalently via a thioalkylcarboxy-spacer, or adsorbed as a neoglycoprotein, to a two-dimensional gold surface. Both types of surfaces showed high specificity in the binding of the uropathogenic bacteria P-fimbriated Escherichia coli compared to the binding of non-infectious bacteria. The signal to noise ratio is sufficiently high to allow specific detection of the bacteria in biosensor applications.

Adsorption↗
PubMed1994

Increased metal release from cemented femoral components made of titanium alloy. 19 hip prostheses followed with radiostereometry (RSA).

In 19 patients the concentrations of metal were measured in serum, urine and joint fluid 2 years after implantation of uncemented commercially pure titanium acetabular cups and cemented or uncemented femoral components made of titanium alloy. A ceramic against the polyethylene articulation was used. The fixation of the components was followed with radiostereometry (RSA). Samples from 12 patients scheduled for hip or knee prostheses and without any metallic implant were used as controls. High levels of titanium were found in cemented hips and when large acetabular cups had been inserted. Increased aluminum levels were also noted in the cemented hips. Vanadium was not detected in any of the samples. Micromotions were detected in most of the implants, but the magnitude of these movements could not be used to predict the release of metal into the synovial fluid.

Adult↗
PubMed1994

Early failure of hydroxyapatite-coating in total knee arthroplasty. A case report.

We observed early loosening of a hydroxyapatite-coated tibial component in a total knee arthroplasty in a randomized study comparing HA-coating with cement fixation. Symptoms of loosening started 8 weeks after surgery. Roentgen stereophotogrammetric analysis revealed stability during the initial 6 weeks followed by a pronounced subsidence up to 6 months after surgery when revision was done. At revision, the HA-coating was found to have separated from the medial part of the tibial component. The synovium was abundant with macrophages and multinucleated giant cells containing HA-crystals. Overloading of the prosthesis and suboptimal quality of the HA-coating was believed to have caused the loosening process.

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PubMed1993

Increased varus-valgus tilting of screw-fixated knee prostheses. Stereoradiographic study of uncemented versus cemented tibial components.

Twenty-six women and three men (34 knees) with osteoarthrosis were operated with the Miller-Galante I (Zimmer, Warsaw, IN) knee prosthesis. The patients were randomized to either cemented or uncemented fixation of the tibial component. All patients received a TiVaAl alloy tibial plate with four pegs and titanium fiber-mesh undersurface. In the uncemented knees four screws were added. The fixation of the tibial component was determined by roentgen stereophotogrammetric analysis during the first 2 postoperative years. Rotations of the entire tibial component were recorded, as well as proximal or distal translation of various parts of the prosthetic edge corresponding to subsidence and lift-off. The uncemented components displayed almost all rotation and translation during the first 6 weeks, whereas the cemented ones displayed a more gradually increasing migration during the 2 years. Tibial component rotation about the sagittal axis was significantly increased in the uncemented knees throughout the investigation period. This corresponded to increased subsidence medially or laterally in the uncemented knees, whereas lift-off was equal in the two groups. Thin (8.5 mm) uncemented tibial components displayed more subsidence than the thicker ones at the medial or lateral edge 3 months after surgery.

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