Posterior urethral injuries associated with pelvic injuries in young adults: computerized finite element model creation and application to improve knowledge and prevention of these lesions

INTRODUCTION

Young adult males involved in motorcycle accidents are particularly at risk for posterior urethral injury whenever pelvic injury occurs. Posterior urethral injuries remain problematic because their diagnosis may be missed, and during the initial treatment response the urethral injury can be aggravated by urethral catheterization. Few anatomical and clinical tools exist that establish a correlation between injuries and fractures of the pelvic ring and the risk of posterior urethral injury.

METHOD

Based on experience with traffic accident modeling, a computerized finite element model was conceived integrating the specific anatomic structures concerned. This model was extrapolated from a CAT scan of a young adult. The anatomic structures concerned in urethral and pelvic ring trauma (PRT) were isolated, placed in 3D and given biomechanical properties. The model was verified according to available experiments on PRT.

RESULTS

To apply the model, we recreated a lateral impact mechanism on the pelvic ring. Stretching between the prostatic and membranous portions of the urethra (before and after visualization of a pelvic fracture) as well as timing of injury was studied.

CONCLUSION

The model's application permitted us to analyze precisely the link between lateral impact trauma of the pelvic ring and lesions of the posterior urethra and to identify an urethra stretching prior to visualization of a pelvic fracture. Utilization of the model with other mechanisms of injury should allow for better comprehension of this associated trauma, improved prevention, iatrogenic aggravation of, and care for, these serious injuries.

[Histological orchiepididymitis discovery in a patient with AIDS]

Incidences of opportunistic infections of the epididymus and the testicule have already been reported in patients suffering from AIDS for over 10 years. Here we have reported the first description of microsporadic orchiepididymitis diagnosed at the university hospital (CHU) of Nice in 2005. We look at the epidemiology, the physiology and the treatment of this extremely rare infection.

Découverte fortuite d’une tumeur vésicale au cours d’une opération de TVT

With the common use of the tension-free vaginal tape (TVT) procedure, we will probably be facing more and more pathologies that will require a transurethral treatment. We report an intra-operative discovery of a bladder tumor during a cystoscopic TVT procedure. The tumor was easily treated by several transurethral resections without any consequences on the result of the TVT procedure.

[Benign testicular tumors in children. Value of simple tumorectomy]

From 1984 to 1999, the authors observed 18 intratesticular tumours, 13 of which corresponded to benign lesions. The objective of this study is to define preoperative and intraoperative criteria of benign lesions in order to allow conservative management (simple excision or enucleation) and to analyse the results of this treatment. The 13 boys of this series were between the ages of 5 months and 14 years (mean: 7.1 years). The lesion presented as scrotal swelling in 12 cases and gynaecomastia in 1 case. Tumour markers (alphafoetoprotein, beta HCG) were at the limit of normal for age. Ultrasonography was performed in every case. In each case, treatment consisted of primary exposure of the pediclc with clamping then exteriorization and macroscopic examination of the lesion. Frozen section examination was performed in 11 cases. Treatment consisted of 9 enucleations and 4 orchidectomies. The final histology concluded on epidermoid cyst or simplified teratoma with exclusively ectodermal development in 4 cases, multi-differentiated teratoma in 2 cases, sex cord tumour in 2 cases, simple cyst in 2 cases, rete testis dysplasia in 1 case, cavernous haemangioma in 1 case, and vestigial cyst in 1 case. There was no discordance between the final histological examination and the frozen section examination. The mean follow-up is 4.4 years. No secondary atrophy and no local or distant recurrence was observed in the 9 cases of enucleation. In conclusion, testicular tumours are often benign in children. Selection based on a body of clinical, laboratory, radiological and frozen section histological evidence should allow carcinologically safe conservative surgery with an aesthetic, psychological and functional benefit for the child.

[Isolated radiocarpal luxation. A case report and general review of the literature]

PURPOSE OF THE STUDY

We describe a case of an isolated radiocarpal dislocation and review the literature.

CASE REPORT

A young 29-year-old male, suffering from a wrist injury after a motor cycle accident, was diagnosed as dorsal radiocarpal joint dislocation with distal radioulnar dislocation and no fracture, close reduction was immediately performed followed by plaster cast immobilisation. After five months satisfactory stability and motion were obtained without signs of carpal instability.

DISCUSSION

This pathology is exceptional with less than 15 published cases. Dislocation is due to wrist hyperextension with ulnar motion but without, probably, intracarpal supination. After immediate treatment, this lesion appeared to have a good prognosis without post-traumatic carpal instability, when compared to the poorer result of perilunar dislocation.

[Mini-invasive surgery of the retroperitoneal space in children]

Although laparoscopic surgery now represents today an essential surgical technique, its use remains limited in urology and especially in pediatric urology for many reasons, main because of the lack of indications. After a large experience acquired in abdominal laparoscopic surgery, and because we were convinced of the advantages offered by this new mini-invasive approach, we have tried to develop it for the retroperitoneal space.

METHODS

Over a five-year period we performed 88 retroperitoneal procedures in children:--50 nephrectomies (44 total, 10 partial) for the following indications: 15 polycystic dysplastic kidney, 13 kidney destroyed by reflux, 18 by obstruction, hypertensive uropathy 3, pyonephrosis 1.--5 renal cystectomies, 3 pyelolithotomies, 2 pyeloureteral obstructions, 2 adrenalectomies, 1 retrocaval ureter, 25 varicoceles. The age range was 2 months to 16 years (mean: 3.7 years, 25 children under 1 year). The patients were placed in the lateral debubitus. The retroperitoneal space was created by dissection under direct vision, then insufflation was performed directly in the retroperitoneal space without balloon. Three or four ports were used except for varicocelectomy which was performed with only one port and an operating channel telescope.

RESULTS

Follow-up range was 6 months to 5 years. The mean operating time was 96 minutes (35 to 210 min.). Average postoperative stay was 2 days. Conversion was needed in 7 cases (8%). Operative incidents consisted of one duodenal perforation, one ureteral burn, 21 peritoneal perforations (24%). There were 5 postoperative complications (2 urinomas after partial nephrectomy, 1 hydrocele, 1 varicocele recurrence, 1 recurrent stones) not related to the technique. 3 cases needed reoperation (ureteral injury, varicocele recurrence, recurrence of cystine stones) with good result.

CONCLUSION

Like other laparoscopic techniques, retroperitoneoscopy requires a training: it remains delicate in children because of the reduced working space and the fragility of the peritoneum. However the advantages seem sufficiently obvious for us to recommend and promote this procedure.

Combined use of FLUKA and MCNP-4A for the Monte Carlo simulation of the dosimetry of 10B neutron capture enhancement of fast neutron irradiations

Boron neutron capture enhancement (BNCE) of the fast neutron irradiations use thermal neutrons produced in depth of the tissues to generate neutron capture reactions on 10B within tumor cells. The dose enhancement is correlated to the 10B concentration and to thermal neutron flux measured in the depth of the tissues, and in this paper we demonstrate the feasibility of Monte Carlo simulation to study the dosimetry of BNCE. The charged particle FLUKA code has been used to calculate the primary neutron yield from the beryllium target, while MCNP-4A has been used for the transport of these neutrons in the geometry of the Biomedical Cyclotron of Nice. The fast neutron spectrum and dose deposition, the thermal flux and thermal neutron spectrum in depth of a Plexiglas phantom has been calculated. The thermal neutron flux has been compared with experimental results determined with calibrated thermoluminescent dosimeters (TLD-600 and TLD-700, respectively, doped with 6Li or 7Li). The theoretical results were in good agreement with the experimental results: the thermal neutron flux was calculated at 10.3 X 10(6) n/cm2 s1 and measured at 9.42 X 10(6) n/cm2 s1 at 4 cm depth of the phantom and with a 10 cm X 10 cm irradiation field. For fast neutron dose deposition the calculated and experimental curves have the same slope but different shape: only the experimental curve shows a maximum at 2.27 cm depth corresponding to the build-up. The difference is due to the Monte Carlo simulation which does not follow the secondary particles. Finally, a dose enhancement of, respectively, 4.6% and 10.4% are found for 10 cm X 10 cm or 20 cm X 20 cm fields, provided that 100 micrograms/g of 10B is loaded in the tissues. It is anticipated that this calculation method may be used to improve BNCE of fast neutron irradiations through collimation modifications.

Complementary roles of central command and muscular reflex in the regulation of heart rate during submaximal isometric contraction

During submaximal isometric contraction, the heart rate (HR) and the electromyographic activity (EMG) increase continuously. Although activation of the muscle and the cardiovascular center is placed partly under the common control of the central command, the nature of the relationship that may exist between HR and the integrated electromyogram (iEMG) is seldom studied. Seventeen healthy men, 22.4 +/- 0.5 years of age (M +/- SE), performed isometric contractions with the right elbow flexors. Forces of 25, 40, 50 and 65% of the maximum voluntary contraction (MVC) were used, and the contractions were sustained until (isotonic isometric contraction: IIC) and beyond exhaustion (anisotonic isometric contraction: AIC). During IIC, a linear relationship exists between HR and iEMG; the slope of this relationship is independent of the relative force developed, which is in favor of a predominant role played by the central command in HR increase. The increase in the ratio iEMG/HR at the approach of local muscular exhaustion would indicate that at the end of IIC there is an increase in the relative part furnished by the information of peripheral origin in HR regulation. During AIC, the force (F) decreases in an exponential manner and stabilizes at around 25% MVC from tAIC = 70 s on. The iEMG and HR change independently: iEMG decreases like F such that iEMG/F remains constant; HR continues to increase in the first phase corresponding to the rapid decrease in F and iEMG, then in a second phase, it decreases linearly with respect to time. Our results suggest that the action of the central command is dominant during stage 1 of AIC, while during stage 2 the relative part furnished by the muscle reflexes increases. Beyond tAIC = 70 s, there seems to be a certain degree of central fatigue.