Introduction: Distraction osteogenesis is an integral part in management of mandibular defects associated with hemifacial microsomia and post-ankylotic mandibular defects. The most difficult part in distraction osteogenesis is the prediction of distraction vector and risk of injury to vital structures as inferior alveolar. The present study aimed to present 3-dimensionally constructed computer-guided splints in distraction osteogenesis to get an ideal vector and minimal risk of vital structures injury. Material and Methods: The technical note presents cases series of 6 patients who had computer-guided distraction osteogenesis surgery using prefabricated splints. Results: The distance between the virtual and physical pins and osteotomy was measured, and the deviation of the vector angle and osteotomy angle was also assessed. Average deviation in pin distance was 3 mm and in vector angle 13.5°. Average deviation in osteotomy distance was 2.6 mm and in osteotomy angle 14.4°. None of the cases had injury to vital structure. There was significant improvement (P = 0.0078) in the medial canthus–buccal commissure distance where the arithmetic mean improved from 59.6 (SD = 10.1) mm pre-distraction in the defective side to 67.1 (SD = 8) mm post-distraction. The degree of correction was 97% compared to the normal side. Conclusion: 3D printed surgical stents were successful in transferring the virtual treatment plan of mandibular distraction osteogenesis into the surgical theatre with an acceptable margin of error and without injury to any vital structures

THE use of diuretics to prevent clot retention following prostatectomy is well known (McKelvie, 1962; Mihailides and Amsler, 1966;Rickwood and Thorne, 1967;Essenhigh and Eustace, 1969). When diuretics are used in this manner there is also an associated reduction in the incidence of urinary infection. It has been suggested that when urea is used to promote diuresis, it exerts a direct bactericidal effect (Schlegel et al., 1961). However, a similar reduction in the incidence of infection is seen when Lasix is used (Essenhigh and Eustace, 1969) and recent observations by O' Grady andCattell (1966), andSylwester (1965) suggest that a high urinary flow rate alone may prevent infection by simple mechanical means.We have used Lasix for some time to prevent clot retention following prostatectomy and felt that it would be worth extending its administration throughout the period of catheterisation in an endeavour to lower the infection rate still further. This paper records our findings in a group of patients treated in this manner. Material andMethod.-A group of 5 1 consecutive patients undergoing prostatectomy was investigated. These patients were unselected, of ages ranging from 45 to 85, and included many with associated disease particularly pulmonary and cardiovascular, and diabetes. No patient was refused operation. One patient died following a cerebrovascular accident 24 hours after operation, and is not included in the series. One patient underwent operation twice; this survey therefore consists of a total of 51 operations on 50 patients.Prostatectomy was performed by one of 3 methods-retropubic, transvesical or transurethral. Free drainage of the bladder into a sterile urine bag was used post-operatively via a Foley or whistle-tipped catheter. Bladder washouts and irrigation were avoided wherever possible, and catheters were removed as soon as the urine was macroscopically free of bloodusualiy 1-3 days post-operatively.Lasix and intravenous fluids were administered according to the scheme shown in Table I. The detailed management of prostatectomy using Lasix has been previously described (Essenhigh and Eustace, 1969), and this system is identical, with the addition of oral Lasix until the catheter is removed.Urine volume was recorded during the period of catheter drainage. Urine cultures were obtained routinely pre-operatively, on removal of the catheter, 2-3 days afterwards, and finally 6 weeks after operation. Antibiotics or sulphonamides were given only if indicated clinically, and were not used routinely.The rate of turnover of urine in the bladder was also investigated in some patients, using radioactive Hippuran. This has proved to be a more complex problem than was originally thought and details of this study are outlined below.Hippuran Study.-Substances such as sodium iodohippurate (Hippuran) do not attach themselves to the bladder wall and so should be cleared from the bladder by purely physical means. A theoretical analysis (similar to that of O'Grady and Cattell) shows that if a bladder

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