Biomedical subjects

K Knutson

Publications and source records attributed to K Knutson.

At least 37 records · Page 2Linked to original sources

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↗

PubMed1993

Enhanced permeation and stratum corneum structural alterations in the presence of dithiothreitol.

Stratum corneum protein biochemical and biophysical structural contributions to the barrier properties of human epidermis were determined in the presence of the reducing agent dithiothreitol (DTT). Mannitol and sucrose permeation through human epidermis in the presence of 0 to 50 mM DTT in PBS (pH 7.4) was measured in symmetric, side-by-side diffusion cells (32 degrees C). DTT enhancement ratios, KP(DTT)/KP(PBS), ranging from 1.6 to 32, were dependent on skin donor and DTT concentrations. DTT did not alter stratum corneum uptake of mannitol or sucrose nor mannitol solubility in DTT/PBS solutions. Stratum corneum biophysical structure was ascertained by FTIR in solvent replacement experiments. DTT-induced protein conformational alterations were apparent in the emergence of an Amide I band near 1615 cm-1, which is generally associated with beta-sheet-like conformers. Therefore, DTT alters stratum corneum biophysical structure through interactions with proteins. After exposure of stratum corneum protein sheets to DTT/PBS solutions, the free thiol concentration increased from < 1 nmol SH/mg protein sheet to approx. 130 nmol/mg. The enhanced permeation which increased with increasing concentrations of DTT, was associated with diffusion mechanisms involving the cornified cells of the stratum corneum. These results indicate that corneocyte protein integrity does contribute to barrier function of the skin and influences the transport of polar solutes.

Cell Membrane↗

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

Ethanol effects on the stratum corneum lipid phase behavior.

The stratum corneum is considered to be the diffusional barrier of mammalian skin for water and most solutes. The intercellular lipid multilayer domains of the stratum corneum are believed to be the diffusional pathway for most lipophilic solutes. Fluidization of the lipid multilayers in the presence of ethanol is frequently conceived to result in enhanced permeation. Current investigations address the effect of ethanol on the phase behavior in terms of stratum corneum lipid alkyl chain packing, mobility and conformational order as measured by Fourier transform infrared (FTIR) spectroscopy. Phospholipid multilamellar vesicles were also studied as model systems. There appeared to be no effect of ethanol on either the solid-solid phase transition or the gel phase interchain coupling of the stratum corneum lipids. However, there was a reduction in the mobility of the alkyl chains in the presence of ethanol. Possible mechanistic relationships between the current FTIR spectroscopic results with available literature data of ethanol induced lipophilic solute penetration enhancement through the skin are discussed.

Animals↗

PubMed1992

The stratum corneum lipid thermotropic phase behavior.

The stratum corneum, the outermost layer of mammalian skin, is considered the least permeable skin layer to the diffusion of water and other solutes. It is generally accepted that the intercellular lipid multilayer domain is the diffusional pathway for most lipophilic solutes. Fluidization of the lipid multilayers is believed to result in the loss of barrier properties of the stratum corneum. Current investigations address the lipid thermotropic phase behavior in terms of lipid alkyl chain packing, mobility and conformational order as measured by Fourier transform infrared (FTIR) spectroscopy. A solid-solid phase transition is observed with increased alkyl chain mobility followed by a gel to liquid-crystalline phase transition near 65 degrees C. These results further elucidate the role of lipid fluidity that may contribute to the transport properties of the stratum corneum.

Animals↗

PubMed1992

Duplication of distal 19q: clinical report and review.

We report on a 20-month-old boy with duplication of the distal part of 19q. His karyotype is 46,XY, -22, + der(22),t(19;22)(q13.3;p11.2)mat. The propositus has multiple minor anomalies, congenital heart defects, seizures, profound psychomotor retardation, and growth impairment. These characteristics are similar to those in the other 10 reported cases of distal 19q duplication and help delineate the phenotype. A review of the literature is presented.

Abnormalities, Multiple↗

PubMed1991

The infected knee arthroplasty. A 6-year follow-up of 357 cases.

The incidence of deep infection after 12,118 primary knee arthroplasties performed in Sweden from October 1, 1975 through 1985 with a median follow-up of 6 years was 1.7 percent for arthrosis and 4.4 percent for rheumatoid arthritis. Risk factors for infection were large prostheses, postoperative wound-healing complications, rheumatoid arthritis, a prior deep infection, and skin infections. We have analyzed the treatment of 357 knee arthroplasties with a deep infection. Systemic antibiotics alone were primarily used in 225 knees, with healing of the infection in 44 knees, 20 of which had a functioning prosthesis at the final follow-up; the treatment did not compromise later revision surgery. Soft-tissue surgery was used in 154 knees--37 healed, 15 of which had a functioning prosthesis. Resection arthroplasty resulted in healing of the infection in 11 of 22 knees. Revision arthroplasty was performed in 107 knees, with eventual healing of the infection in 81 knees, 36 of which had a functioning prosthesis; there were no differences in the outcome of one-stage and two-stage procedures. Arthrodesis was attempted in 135 knees, with eventual healing of the infection in 120 knees and fusion in 105. Twenty-two patients were amputated. Thus, the infection healed in 315 knees (88 percent), but only 71 (20 percent) recovered with a functioning prosthesis, and 8 patients died of the infection. Attention should therefore focus on prophylactic measures directed towards the soft-tissue problems--by avoiding conflicting skin incisions, by gentle handling of the periarticular soft tissues, by avoiding the use of constrained prostheses and oversized compartmental prostheses, by letting wound healing take priority over motion in knees with compromised soft tissues, and by using prophylactic antibiotic treatment for skin ulcers until these have healed.

Adolescent↗

PubMed1990

Poly(dimethylsiloxane)-poly(ethylene oxide)-heparin block copolymers. II: Surface characterization and in vitro assessments.

Amphiphilic block copolymers containing poly(dimethylsiloxane), poly(ethylene oxide), as well as heparin-coated glass beads and tubes were evaluated for the amounts and activities of surface-immobilized heparin. Because the amphiphilic copolymer system is thermodynamically predicted to demonstrate low-energy phase enrichment on the surfaces of air-cast films, studies were also undertaken to understand the in vitro results. Solvent-cast copolymer films have a heterogeneous microphase-separated structure according to transmission electron micrographs. Wilhelmy plate contact angle analysis indicates significant surface restructuring occurs upon hydration. Attenuated total reflectance infrared spectroscopy studies of the desiccated and hydrated films at two different sampling depths show compositional heterogeneity as a function of depth, as well as near surface restructuring allowing surface enrichment of the high-energy segments following contact with water. Significant concentrations of heparin are detected on the surface of these coatings by toluidine blue assays. In addition, a portion of the surface-bound heparin maintains its original bioactivity as determined by recalcification times, thrombin times, and Factor Xa assays. These substrates were also tested for platelet adhesion and activation reactions in vitro using polymer-coated beads in rabbit platelet-rich plasma. Heparinized polymers promoted low levels of platelet adhesion and serotonin release. Surface concentrations of heparin from bioactivity assays were then correlated with platelet adhesion and the extent of platelet release to assess the efficacy of this heparin-immobilized copolymer as a blood-compatible material or coating.

Animals↗

PubMed1990

Mechanism of ethanol-enhanced estradiol permeation across human skin in vivo.

The influence of ethanol on the permeation of 17 beta-estradiol (estradiol) across viable human skin in vivo was investigated with the human skin sandwich flap model. Maintaining continuous delivery of a constant concentration of the solute in phosphate-buffered saline, pH 7.4 (PBS), or mixtures of ethanol in PBS to the skin surface revealed that steady-state flux of estradiol was achieved within 30-60 min and maintained throughout 4 hr. The 10-fold decrease in in vivo flux and permeability coefficient (Kp) of tracer estradiol solutions in ethanol or ethanol solutions compared with PBS vehicle reflected the 10-fold difference in the apparent partition coefficients (Km) of estradiol from the respective vehicles into isolated human stratum corneum. Neither the stratum corneum thickness nor the diffusion coefficient of estradiol was significantly different among the vehicles tested. In vivo flux of estradiol in ethanol or ethanol solutions across viable human skin was increased with saturated solutions of estradiol. Further, in vivo flux of estradiol from vehicles such as PBS, ethanol, and ethanol mixtures, which minimally alter the rate-limiting barrier, can be successfully predicted with knowledge of only two physicochemical parameters, the estradiol concentration in the vehicle and the Km of estradiol from the vehicle into isolated human stratum corneum.

Animals↗

PubMed1990

Percutaneous absorption enhancement of an ionic molecule by ethanol-water systems in human skin.

Ethanol-water systems enhance permeation of ionic solutes through human stratum corneum. Optimum enhancement of salicylate ion permeation has been observed with ethanol volume fractions near 0.63. The mechanism of action of ethanol-water systems enhancing skin permeation was investigated by in vitro skin permeation studies combined with Fourier transform infrared spectroscopy experiments. The increased skin permeation of the ionic permeant by the ethanol-water systems may be associated with alterations involving the polar pathway. Polar pathway alterations may occur in either or both the lipid polar head and proteinaceous regions of the stratum corneum. Ion-pair formation may also contribute to increased permeation. However, the decreased permeation of salicylate ion observed at higher volume fractions of ethanol may be attributed to decreased uptake of permeant into the stratum corneum.

Adult↗

PubMed1990

Revision after osteotomy for gonarthrosis. A 10-19-year follow-up of 314 cases.

During a 10-year period, 314 tibial osteotomies were performed for medial gonarthrosis. At follow-up after 10-19 years, 62 knees had been revised by arthroplasty (52 cases) or reosteotomy (10 cases). The revision rate was 54/170 in undercorrected knees and 8/144 in knees with normalization or overcorrection of the hip-knee-ankle angle. Our results confirm that tibial osteotomy for gonarthrosis requires proper indications and precise surgery. Perhaps, given another 10 years, our osteotomies will have outlived contemporary arthroplasties.

Female↗

PubMed1989

Effects of long-term hydration leading to the development of polar channels in hairless mouse stratum corneum.

Dramatic increases in in vitro permeability coefficients have been observed following the long-term hydration (days) of hairless mouse skin. The effect is greatest for extremely polar or ionized solutes. Differential scanning calorimetry has been utilize in complementary studies in an attempt to assess if the altered permeability may be due to the irreversible alteration of lipid fluidity or keratin structure. The melting range of the lipid endotherms appears to be unaffected when stratum corneum is subjected to hydration conditions similar to those in the permeability experiments. Endotherms attributed to keratin appear to be altered by long-term hydration. However, no quantitative correlation was found between the keratin endotherm area and the permeabilities. The permeability data fit a model where the total permeability coefficient at a given time is the sum of the permeability coefficients associated with the lipid route and the polar route. Permeation increases with hydration time due primarily to alteration of the polar route. Based on molecular weight, no limitation of diffusion in the polar pathway was detected.

Animals↗

PubMed1989

Dose-dependent enhancement effects of azone on skin permeability.

In vitro permeability experiments have been combined with differential scanning calorimetry (DSC) studies in an attempt to address the dose-dependent influence of Azone on the permeability coefficients of solutes for hairless mouse stratum corneum. A spray technique was developed to deliver uniformly and quantitatively small amounts of Azone to the stratum corneum. Permeability data obtained for several model solutes of varying lipophilicity suggest lipid fluidization and polar route enhancement as the mechanisms of action for Azone. Alkanols and steroids, both of which are enhanced primarily by lipid fluidization, had different degrees of relative enhancement. This provides evidence that the stratum corneum barrier is heterogeneous, rather than a homogeneous slab barrier. Two effects of Azone on the stratum corneum were detected by DSC. A decrease in the area and a shift to lower temperatures were noted for the lipid endotherms with increasing doses of Azone. A lipid fluidizing effect would qualitatively account for the increases in the permeability coefficients noted for more lipophilic solutes. The stratum corneum keratin endotherm also appears to be altered in the presence of Azone. It is possible that alteration of the keratin structure could lead to the development of polar routes in the stratum corneum.

Animals↗

PubMed1989

Treatment of infected knee arthroplasty.

Forty-eight patients with 51 infected knee arthroplasties were treated at the authors' institution between 1973 and 1986 and followed for 5.5 (range, 0-14) years. Six methods to treat the infections were employed: antibiotics only, soft-tissue surgery, removal of the prosthesis, revision arthroplasty, arthrodesis, and amputation. Failure of the initial surgical treatment led to second revision surgery in 20 patients. At the follow-up examination, three patients (five knees) had died from septic complications and two patients had had above-knee amputation. Two of 32 patients had been successfully treated with antibiotics with no additional surgery. Four patients had successful soft-tissue surgery. Following removal of the prosthesis, the infection healed in four patients. In 12 of 19 patients (13 knees) with revision arthroplasty the infection healed, but only seven of these had functioning prostheses. The infection healed in all but one of the 21 patients with arthrodeses, and all but two were fused. Infected compartmental prostheses with good bone stock can be treated with an exchange arthroplasty using a two-stage procedure with tricompartmental revision prostheses. Otherwise, an arthrodesis using a two-stage procedure is recommended for the treatment of infected knee arthroplasty.

Adult↗

PubMed1987

Hematogenous infection after knee arthroplasty.

Twenty-five hematogenously infected knee arthroplasties in 20 patients (17 with rheumatoid arthritis and 3 with arthrosis) were followed for 3 years. Staphylococcus aureus was the major infecting organism. Three patients with four arthroplasties died of sepsis. Two patients had removal of the arthroplasty, one of which resulted in an above-the-knee amputation. Four out of five arthrodeses fused. Two knees healed after early debridement and two healed without surgery. Ten knees had successful revision arthroplasty. Rheumatoid arthritis and constrained prostheses increase the risk of hematogenous infection. Any infection and especially cutaneous lesions in a patient with a knee arthroplasty should be treated vigorously.

Adult↗

PubMed1987

Treatment of the exposed knee prosthesis.

Ten knees with early tissue breakdown after knee arthroplasty resulting in exposed prostheses were treated with different plastic surgical techniques. Six knees were successfully covered: four using a gastrocnemius musculocutaneous flap, one using a fasciocutaneous flap, and one using split-skin grafts. Four knees failed: two using local skin flaps and two using split-skin grafts. A gastrocnemius musculocutaneous flap seems to provide a reliable coverage of the exposed knee joint.

Aged↗

PubMed1987

Revision knee arthroplasty in rheumatoid arthritis.

Seventy-six revised total knee arthroplasties (TKAs) performed for mechanical, nonseptic failure of the primary arthroplasty in 62 rheumatoid arthritis patients were investigated. The revisions were performed with McIntosh, Marmor, Attenborough, Guepar, and various types of tricompartmental prostheses. Twenty-one of the 76 revisions subsequently failed. Fifteen were mechanical failures and six were deep infections. Thirteen of the 21 failures were treated with another arthroplasty, six with arthrodesis, and two with antibiotics only. After an average of 60 months, 48 of the surviving arthroplasties were examined clinically and roentgenographically. At follow-up examination, eight were clinical failures. One-half of the McIntosh and Marmor arthroplasties and one-third of the Attenborough and Guepar arthroplasties, altogether 17 cases, showed signs of potential roentgenographic failure. The majority of the revised TKAs classified as roentgenographic failures were clinically successful or acceptable. Revision of TKAs in noninfected rheumatoid patients can be performed with acceptable clinical results but with a significantly higher failure rate than after primary procedures.

Arthritis, Rheumatoid↗

PubMed1986

Survival of knee arthroplasties. A nation-wide multicentre investigation of 8000 cases.

A prospective nation-wide study of knee arthroplasty has been under way in Sweden since October 1975. By the end of 1983, 4505 arthroplasties for osteoarthritis and 3495 for rheumatoid arthritis had been recorded and reviewed one, three and six years after the operation. Using actuarial methods, the probability of the prosthesis remaining in situ after six years was calculated. In osteoarthritis this probability ranged from 65% for hinged prostheses to 90% for medial compartment prostheses. Two-and three-compartment prostheses produced intermediate results with 87% survival. In rheumatoid arthritis the probability varied from 72% for medial compartment prostheses to 90% for two- and three-compartment prostheses. The main reason for failure was loosening of the components, the second most common was infection. The probability of revision for infection by six years was 2% in osteoarthritis and 3% in rheumatoid arthritis. Most revisions were to a three-compartment prosthesis. Knee fusion at primary revision was required in 2% of the cases at six years.

Arthritis, Rheumatoid↗