Rapid prototyping techniques for anatomical modelling in medicine.

The rapid advances in computer technology, often driven by the demands of industry, have created new possibilities in surgery which previous generations of surgeons could only have imagined. Improved imaging with computerised tomography (CT) has been followed by magnetic resonance imaging (MRI) and, more recently, it has become possible to reformat the data as three-dimensional images. Computer technology has new moved forward with the advent of rapid prototyping techniques (RPT) which allow both the production of models of the hard tissues and custom-made prostheses from computerised scanning data. In this article we review the development and current technologies available in RPT and the applications of this advance in surgery and illustrate this with two case reports.     

Does transcranial stimulation for motor evoked potentials (TcMEP) worsen seizures in epileptic patients following spinal deformity surgery?

Purpose

To investigate the effect of Transcranial Motor Evoked Potentials (TcMEP) in increasing the severity or frequency of post-operative seizures in patients undergoing deformity corrective spine surgery with a known history of seizures pre-operatively.

Methods

The information on all patients with history of epilepsy/seizures who underwent spinal TcMEP cord monitoring for deformity correction surgery was retrospectively collected through a review of the hospital notes. The benefits of TcMEP in the early detection of potential cord ischemia were deemed by the operating surgeon to outweigh the increased risks of seizures, tongue biting, etc. Data on age, gender, pre-operative diagnosis, curve type, intra-operative monitoring alerts, duration of hospital stay, and post-operative in-hospital seizures were collected. Additionally, the patients were contacted following discharge and data on any change in the frequency of the seizures or an alteration in seizure-related medication post-operatively was also collected.

Results

The records of 449 consecutively monitored patients were reviewed and 12 (2.7 %) patients with a history of seizures pre-operatively were identified. The mean age was 23 (9–59) years, 7 females, 11 scoliosis corrections (4 neuromuscular, 1 degenerative, 6 idiopathic adolescent), and one sagittal balance correction surgery. Intra-operatively, all patients had TcMEP monitoring, were catheterised, and had no neuromonitoring alerts or record of tongue biting or laceration. Post-operatively, the mean hospital stay was 12 (4–25) days with no recorded seizures. At a mean of 23 (12–49) months post-discharge, none of the patients reported a worsening of seizures (pattern or frequency) or required an alteration in the seizure-related medications.

Conclusion

TcMEP does not appear to trigger intra-operative or post-operative seizures and is not associated with deterioration in the seizure control of patients suffering seizures pre-operatively.

     

Randomised controlled trial of health assessments for older Australian veterans and war widows

OBJECTIVE: To assess the effect of home-based health assessments for older Australians on health-related quality of life, hospital and nursing home admissions, and death. DESIGN: Randomised controlled trial of the effect of health assessments over 3 years. PARTICIPANTS AND SETTING: 1569 community-living veterans and war widows receiving full benefits from the Department of Veterans' Affairs and aged 70 years or over were randomly selected in 1997 from 10 regions of New South Wales and Queensland and randomly allocated to receive either usual care (n = 627) or health assessments (n = 942). INTERVENTION: Annual or 6-monthly home-based health assessments by health professionals, with telephone follow-up, and written report to a nominated general practitioner. MAIN OUTCOME MEASURES: Differences in health-related quality of life, admission to hospital and nursing home, and death over 3 years of follow-up. RESULTS: 3-year follow-up interviews were conducted for 1031 participants. Intervention-group participants who remained in the study reported higher quality of life than control-group participants (difference in Physical Component Summary score, 0.90; 95% CI, 0.05-1.76; difference in Mental Component Summary score, 1.36; 95% CI, 0.40-2.32). There was no significant difference in the probability of hospital admission or death between intervention and control groups over the study period. Significantly more participants in the intervention group were admitted to nursing homes compared with the control group (30 v 7; P < 0.01). CONCLUSIONS: Health assessments for older people may have small positive effects on quality of life for those who remain resident in the community, but do not prevent deaths. Assessments may increase the probability of nursing-home placement.     

Early fracture of clavicle following neck dissection

Fracture of the clavicle as a late complication following radical neck dissection is rare, with an incidence of approximately 0.4-0.5 per cent. We report a case where fracture occurred early following a selective neck dissection.     

Acute Babesia bigemina infection: Changes in fibrinogen catabolism

Summary Plasma from cattle infected with Babesia bigemina contained soluble fibrin in monomer and high molecular weight complex forms. Fibrin(ogen) degradation products were not constantly detected and there appeared to be little or no evidence to suggest fibrinolysis or fibrin deposition. It is suggested that classical disseminated intravascular coagulation does not occur during B. bigemina infection.     

Babesia bovis (argentina): Analysis of fibrinogen-like proteins during infection

Summary Fibrinogen and fibrinogen-like proteins (FLP) were isolated from plasma and serum of cattle acutely infected withBabesia bovis. The sizes and chain structures of these proteins were examined and clotting assays performed. The results indicated that the blood was in a hypercoagulable state due mainly to enhanced production of hydrogen bonded fibrin and offset partly by slight inhibition of chain cross-linking. The latter appeared due to a Factor XIII inhibitor. Reduction of A chains of plasma FLP was not evident, nor could lower molecular weight remnants be regularly detected strongly suggesting that fibrin(ogen) lysis rarely occurred. Similarly the size and chain structure of the majority of noncoagulable FLP of serum was consistent with their being the product of coagulation and not fibrinolysis. Only in heavily infected splenectomized cattle were products from lysed cross-linked fibrin detected and these constituted only about 3% of total serum FLP.     

The characterisation of an esterase derived fromBabesia bovis and its use as a vaccine

An esterase was isolated from a crude extract ofBabesia bovis by affinity chromatography, using soy bean trypsin inhibitor as a ligand. In native form this enzyme had a molecular weight greater than 200000, but on denaturing gels major bands were observed with molecular weights of 20000, 10000 and 7000. Western transfer analysis revealed a major band with a molecular weight of 19000–20000. Both bovine and rabbit antisera avidly stained infected red cells, using indirect immunofluorescence. Weak parasite staining was also observed using this test.Two groups of five animals were vaccinated twice 4 weeks apart with esterase derived from 5×10⁹ parasites as water-in-oil emulsions with Freund's complete adjuvant. Two control groups, each of five animals were also included. One group of vaccinates and a control group were challenged with virulent homologousB. bovis, whilst the other vacinated and the remaining control group were challenged with virulent heterologous organisms. In the homologous groups two controls but no vaccinates died, whereas in the heterologous groups four animals in each group died. Significant differences in parasitaemia, temperature rise and total haemolytic complement were observed in the homologous vaccinated group compared to their controls but no differences were observed between heterologous groups.     

Babesia bovis: Vaccination studies with three groups of high molecular weight antigens from lysate of infected erythrocytes

A void volume fraction and fractions of mean sizes 800 kdalton and 300 kdalton were isolated by gel filtration from lysate of bovine erythrocytes infected with Babesia bovis. All fractions had good serological activity, as assayed by ELISA and IFA. Groups of four splenectomized calves were vaccinated with each fraction and then challenged, together with groups of four control calves, with a homologous strain of B. bovis. The group vaccinated with the 300 kdalton fraction showed some protection, as indicated by delayed and significantly lower parasitaemias and by a 75% survival in the group. In contrast, all animals in the relevant control group died from infection. No evident protection was obtained with the other two fractions.     

An enzyme linked immunosorbent assay to diagnose Babesia bovis infection in cattle

The optimum gel filtration fraction from lysate of Babesia bovis infected erythrocytes was determined for use as an antigen in an ELISA to diagnose B. bovis infection in cattle. Of four enzyme labels tested, horseradish peroxidase was the most suitable. The assay is both sensitive and specific in detecting antibody for 2–4 years after a single infection. False positive reactions were obtained only with some sera from some Anaplasma marginale infected cattle.