PSpice simulation of ultrasonic systems.

The usage of electrical analogies for the simulation of wave generation and propagation in ultrasound transducers is well established. In this paper a PSpice approach that includes the temperature and frequency dependency of the transducer performance is proposed. The analogy between acoustic wave propagation and wave propagation in an electric transmission line is given. Further ways to deduce temperature and frequency dependencies are discussed. The simulation approach is applied to a pulse-echo setup for the determination of speed of sound and attenuation in liquids and solids. Experiments and simulations are made for three temperatures and in the frequency range 1-12 MHz using water, glycerine, and polymers (PMMA and PEEK) as test samples. Comparison shows a good agreement between simulation and experiments. Results for glycerine indicates that the available attenuation models for high viscosity liquids is inappropriate.

Major surgery seems not to influence HIV disease progression in haemophilia patients.

The influence of major surgery on HIV disease progression and decline in CD4+ cell count was evaluated in 23 seropositive haemophilia patients. 24 HIV-infected patients served as non-operated controls. In addition, 32 age-matched seronegative subjects were included. The follow-up time was up to 5 years. During the course of the study, eight of the operated (35%) and 11 of the non-operated (48%) subjects developed HIV-related symptoms (P=0.267). The relative risk for developing HIV-related symptoms after surgery was 0.60 (95% CI 0.25; 1.48). A significant decline in CD4+ cell counts was observed in both the surgery (4.0 x 10(6)/l/month, 95% CI 2.0; 6.0 x 10(6), P=0.001) and the non-surgery (4.0 x 10(6)/l/month, 95% CI 2.0; 6.0 x 10(6), P=0.004) seropositive subgroup, but no difference between the two subgroups was seen (P=0.793). HIV (6.0 x 10(6)/l/month, 95% CI 2.1; 9.9 x 10(6), P=0.0005) but not surgery (-1.0 x 10(6)/l/ month, 95% CI -3.0; 0.96 x 10(6), P=0.647) was an independent predictor for the decline in CD34+ cell count. No interaction effect was observed between HIV infection and surgery (P=0.361). The annual amount of factor concentrate used for regular replacement therapy did not influence the decline in CD4+ cell count (P=0.492). We conclude that major surgery may be considered in symptom-free HIV-seropositive haemophilia patients, with CD4+ cell counts > or = 0.20 x 10(9)/l under similar premises as for seronegative subjects.

Radioactive synoviorthesis in patients with hemophilia with factor inhibitor.

In nine patients with hemophilia and factor inhibitor (six with hemophilia A; three with hemophilia B), 19 joints were treated with radioactive synoviorthesis using Au-198. Ages ranged from 3 to 40 years. Synoviorthesis was performed when the antibody titer was low (< 10 Bethesda units), thus making hemostasis possible by factor administration for 2 to 4 days. On five occasions, radioactive synoviorthesis was performed simultaneously with tolerance induction according to the Malmö protocol. A bleeding free interval of more than 6 months was obtained in 11 joints, six of which remained bleeding free for more than a year. At long term followup (range, 18-182 months) five joints were rated good, one joint was fair, and 11 joints were poor. Although the results are inferior to those for patients with hemophilia without inhibitor, radioactive synoviorthesis should be considered because of its ease of performance and the definite decrease in joint bleeding frequency that it brings about. This is of particular interest in patients with hemophilia caused by factor inhibitor who otherwise are difficult to treat.

Haemophilia prophylaxis in young patients--a long-term follow-up.

OBJECTIVES: To review long-term prophylactic factor treatment in young patients with severe haemophilia A and B, focusing on the orthopaedic and radiological outcome. DESIGN: We received 34 patients with severe haemophilia A (n = 29) and B (n = 5), aged 7-22 years. Age at start of treatment was 1-4.5 years. Dosages of factor concentrate (F VIII and F IX, respectively) were 25-40 IU/kg body weight, three times a week for haemophilia A and twice a week for haemophilia B. The patients had been checked annually over a 5-year period (1990-95). Orthopaedic and radiological joint scores were evaluated according to recommendations by the World Federation of Haemophilia. SETTING: All results were obtained at the Department for Coagulation Disorders, University of Lund, Malmö University Hospital, Malmö, Sweden. RESULTS: Orthopaedic and radiological joint scores were found to have remained unchanged during follow-up in almost all patients and to be still zero (i.e. no unaffected joints) in 79% (n = 27) of the patients. CONCLUSION: There is a growing international consensus haemophilic arthropathy can be prevented by administering early high-dose prophylaxis. The results of the present investigation strongly support this opinion.

Orthopaedic surgery in hemophilia. 20 Years' experience in Sweden.

At the International Hemophilia Center, Malmö, Sweden, which serves a large proportion of the Swedish hemophilia population, 98 orthopaedic surgical procedures were performed from 1970 to 1989 in 66 patients ranging in age from 6 to 71 years. The most common procedures were knee synovectomy, elbow synovectomy in combination with resection of the radial head, and total hip replacement. Comparing the 2 decades of the period, 3 differences were observed: a decreasing need of surgery, an increasing average age of the patients, and a change in the kinds of operations performed. Knee synovectomy and achillotenotomy were most frequent during the 1970s, whereas elbow synovectomy with resection of the radial head and total hip replacement were most frequent during the 1980s. Owing to the availability of regular factor replacement therapy as practiced at the Malmö Center, the situation of patients with hemophilia has improved dramatically during the last 2 decades. In the authors' opinion, it is now possible to avoid hemophilic arthropathy almost completely by giving effective continuous prophylaxis from an early age. In all likelihood, this is the explanation of the changing picture of orthopaedic surgery in patients with hemophilia today.

Total hip replacement in patients with hemophilia. 13 hips in 11 patients followed for 1-16 years.

During 1973-88, we performed 13 total hip replacements in 11 hemophilia patients, mean age 46 (25-65) years. During the operation, blood loss averaged 920 mL, and a mean of 120,000 units of factor VIII/IX were used. The mean duration of follow-up was 7 (1-16) years. 5 hips became loose within 6 years, and a further one after 13 years. 4 hips were revised, 2 of them due to infection in patients who were also seropositive for HIV. At the latest follow-up, 10 patients were alive. 6 had no hip pain and 7 could walk at least 1,000 meters at a time. Although these results are inferior to those obtained in arthrosis, total hip replacement should be considered in hemophiliac patients.

Twenty-five years' experience of prophylactic treatment in severe haemophilia A and B.

In Sweden, prophylactic treatment of boys with severe haemophilia has been practised since 1958 in an attempt to convert the disease from a severe to a milder form. The present study population consisted of 60 severe haemophiliacs (52 A, 8 B), aged 3-32 years. Treatment is started when the boys are 1-2 years of age, the regimens used being 24-40 IU F VIII kg-1 three times weekly in haemophilia-A cases (i.e. greater than 2000 IU kg-1 annually) and 25-40 IU F IX kg-1 twice weekly in haemophilia-B cases. The orthopaedic and radiological joint scores (maximum scores of 90 and 78, respectively) are evaluated as recommended by the World Federation of Haemophilia. Of those subjects aged 3-17 years, 29 out of 35 individuals had joint scores of zero. The oldest group had only minor joint defects. The VIII:C and IX:C concentrations had usually not fallen below 1% of normal. All 60 patients are able to lead normal lives. In conclusion, it appears to be possible to prevent haemophilic arthropathy by giving effective continuous prophylaxis from an early age, and preventing the VIII:C or IX:C concentration from falling below 1% of normal.

Synoviorthesis in young patients with hemophilia and inhibitory antibodies.

In five patients under the age of 15 with hemophilia and inhibitors, due to frequent joint bleedings, 13 joints were treated with synoviorthesis (intra-articular injection of radioactive gold). The patients received high doses of factor VIII/IX for 2-4 days or were treated simultaneously with tolerance induction according to the Malmö protocol. Of the 13 joints treated, a bleeding-free interval of more than 6 months was obtained in nine of which six remained free from bleedings for more than a year. Ease of performance, the limited requirements of pre- and postoperative care, and a definite decrease in the joint bleeding frequency render synoviorthesis well suited for use in hemophiliacs with inhibitors who are otherwise difficult to treat.