Revision of ASR hip arthroplasty: analysis of two hundred and ninety six recalled patients at seven years.

PURPOSE: The aim of this study is to present an algorithm for the evaluation of both symptomatic and asymptomatic patients. METHODS: From November 2004 to May 2010, there were performed 296 operations: 245 total hip arthroplasty and 51 resurfacing arthroplasty with the ASR DePuy system. In April 2010, there was the first Medical Device Alert regarding all MoM hip replacements in the UK and in August 2010, DePuy recall started worldwide. In March 2012, we started our recall. All patients were invited to undergo clinical investigation, X-ray evaluations, and blood chrome and cobalt level determination. For a short period of time, there were performed second level exams and subsequently, we carried out MARS MRI hip study to all symptomatic patients and there was evidence of ALVAL lesions. RESULTS: To the patients with ALVAL lesions were proposed surgical hip revision while the others frequent follow-up controls. One hundred patients underwent hip surgical revision. CONCLUSIONS: We recommend constant MoM THA patients monitoring and early revision if necessary.

Transpedicular Approach to Thoracic Disc Herniaton Guided by 3D Navigation System.

BACKGROUND: The choice of surgical approach for thoracic disc herniation should consider the location on the axial plane and the consistency of the herniated disc. Calcified midline disc herniations are difficult to remove with a transpedicular approach because of limitations due to blind spots; so they are usually treated via a transthoracic approach, although this entails a high risk of thoracopulmonary injuries. METHODS: In this work we present two cases of calcified midline thoracic disc herniations treated with a transpedicular approach, improved by using a three-dimensional (3D) neuronavigation system to verify the extent of removal on the blind side. RESULTS: Postoperative computed tomography (CT) scans demonstrated that this original technical innovation, in the two present cases, allowed us to reach the side opposite the disc herniation and to assess the extent of resection at the end of the procedure. CONCLUSIONS: The employment of a neuronavigation system in the transpedicular approach allowed safe and effective removal of calcified midline thoracic disc herniations. We did not observe any postoperative neurological worsening, onset of spinal instability, or other adverse events.

Burkholderia cepacia lipase is a promising biocatalyst for biofuel production.

Lipases resistant to inhibition and denaturation by methanol are valuable tools for biotechnological applications, in particular for biofuel production. Microbial lipases have attracted a great deal of interest because of their stability at high concentrations of organic solvents. Burkholderia cepacia lipase (BCL) is tested here for robustness towards methanol in terms of conformational stability and catalytic activity in transesterification assays. This lipase turns out to be even more tolerant than the homologous and better characterized enzyme from Burkholderia glumae. BCL unfolding transition, as monitored by far-UV circular dichroism (CD) and intrinsic fluorescence, displays a Tm above 60°C in the presence of 50% methanol. The protein unfolds at low pH, and the organic solvent affects the nature of the denatured state under acidic conditions. The protein performs well in transesterification assays upon prolonged incubations at high methanol concentrations. BCL is highly tolerant to methanol and displays particularly high conformational stability under conditions employed for transesterification reactions. These features depict BCL as a promising enzyme for biofuel industry.

Penile curvature: an update for management from 20 years experience in a high volume centre.

Our aim was to review the literature and discuss about penile curvature in order to have an update for management after 20 years experience in the field.Penile curvature may be congenital or acquired. Congenital penile curvature is a relatively uncommon condition that may present in late adolescent or early adult life. The incidence is estimated to be 0.6 %. On the other side, acquired penile curvature has an overall prevalence of 0.5-13%. Three main factors seem to increase the risk of developing an acquired penile curvature, often related to Peyronie's disease: penile traumatism, genetic and familiar conditions and a history of diseases of the genital tract. In treating Peyronie's disease, no medical therapy is fully effective, and surgery remains the gold standard in cases of severe deformity and/or erectile disfunction. Peyronie's disease is associated with significant psychological stress for patients and their partners. Appropriate treatment should be individualized and tailored to the patient's goals and expectations. There is not the 'best' surgical technique and outcomes are satisfactory when proper treatment decisions are made.

The effect of thermodynamic properties of solvent mixtures explains the difference between methanol and ethanol in C.antarctica lipase B catalyzed alcoholysis.

Kinetic modelling, molecular modelling, and experimental determination of the initial reaction velocity of lipase-catalyzed alcoholysis were combined to study the effect of the alcohol substrate to catalytic activity. The model system consisted of methanol or ethanol at varying concentrations, vinyl acetate as ester substrate 15.2% (v/v), toluene as organic solvent, water at a controlled thermodynamic activity of 0.09, and C. antarctica lipase B as enzyme. For both alcohol substrates, the initial reaction velocity increased sharply at low concentrations and reached a maximum at 0.7% (v/v) for methanol and 2% (v/v) for ethanol. For higher concentrations, the reaction rate decreased to a level of 74% and 60% of the peak value, respectively, due to substrate inhibition. The concentration dependency was described by a kinetic model, including a ping-pong bi-bi mechanism and competitive inhibition by the alcohol, and confirmed previous observations that methanol is more efficiently inhibiting the enzyme than ethanol. However, if the initial reaction velocity was expressed in terms of thermodynamic activity of the two alcohol substrates, the maximum of initial reaction velocity was similar for methanol (a MeOH(max)=0.19) and ethanol (a EtOH(max)=0.21). This was confirmed by molecular modelling which resulted in similar KM (0.22 and 0.19) and Ki values (0.44 and 0.49) for methanol and ethanol, respectively, if expressed in thermodynamic activities. Thus, the experimentally observed difference between methanol and ethanol is not due to differences in interaction with the enzyme but is a consequence of the thermodynamics of the substrate-solvent mixture. For low concentrations in toluene, the activity coefficient of methanol is 40% higher than the activity coefficient of ethanol (γ MeOH=8.5, γ EtOH=6.1).

Molecular mechanism of deactivation of C. antarctica lipase B by methanol.

The catalytic activity of Candida antarctica lipase B upon alcoholysis of a constant concentration of 15.2% vinyl acetate (vol/vol) and varying concentrations of methanol (0.7-60%) in toluene was determined experimentally by measuring the initial reaction velocity. The molecular mechanism of the deactivation of the enzyme by methanol was investigated by fitting the experimental data to a kinetic model and by molecular dynamics simulations of C. antarctica lipase B in toluene-methanol-water mixtures. The highest catalytic activity (280 U/mg) was observed at methanol concentrations as low as 0.7% methanol (vol/vol), followed by a sharp decrease at higher methanol concentrations. For methanol concentrations above 10% (vol/vol), catalytic activity was at 30% of the maximum activity. A variation of water activity in the range 0.02-0.09 had only minor effects. These experimental observations are described by a simple kinetic model using three assumptions: (1) a ping-pong bi-bi mechanism of the enzyme, (2) competitive inhibition by the substrate methanol, and (3) by describing enzyme kinetics by the thermodynamic activities of the substrates rather than by their concentrations. Two equilibrium constants of methanol (KM,MeOH=0.05 and Ki,MeOH=0.23) were derived by modeling methanol binding to the substrate binding site of the lipase in molecular dynamics simulations of protein-solvent systems at atomic resolution. Thus, the sharp maximum of catalytic activity of C. antarctica lipase B at 0.7% methanol is a direct consequence of the fact that methanol-toluene mixtures are far from ideal. Understanding the thermodynamics of solvent mixtures is prerequisite to a quantitative model of enzymatic activity in organic solvents.

Sexual outcomes after organ potency-sparing surgery and glans reconstruction in patients with penile carcinoma.

INTRODUCTION: Radical surgery is the "gold standard" for treatment of invasive penile carcinoma but very poor aesthetic, functional and psychological outcomes have been reported. Our purpose was to assess the impact of organ potency-sparing surgery in locally confined carcinoma of the penis. MATERIALS AND METHODS: We evaluated retrospectively 42 patients with early penile cancer (Ta,T1,T2), treated with glandulectomy and glanduloplasty with urethral mucosa and sparing of cavernosal apexes, or glandulectomy and limited apical resection in cases of Stage T2. Sexual function, ejaculation and libido were evaluated with an IIEF-15 questionnaire before the appearance of neoplasia (about three months before the surgery) and six months after surgery. Quality of life was evaluated by the Bigelow-Young questionnaire. The scores relating to two weeks prior to the surgery have been compared to those obtained six months after surgery. The statistical analysis was conducted using t-Student for repeated measures and analysis of variance. RESULTS: Six months after surgery 73% of patients reported spontaneous rigid erections, 60% coital activity while 76% of the group treated with urethral glanduloplasty reported normal ejaculation and orgasm, regained an average of 35 days after surgery. The average IIEF-15 scores reported in the entire series in the domains of erection, libido and coital activity of the pre-cancer period were not statistically different than those recorded six months after surgery. In the group treated with glandular reconstruction, pre-and postoperative IIEF-15 mean scores related to ejaculation and orgasm domains were not significantly different. Mean scores of Bigelow-Young questionnaires related to sexual pleasure, familial, social and professional relationships showed significant improvement after surgery. CONCLUSIONS: Potency sparing-sparing surgical treatments have a positive impact on a wide spectrum of the patient's life including family relationships, and social and working conditions.

Effects of methanol on a methanol-tolerant bacterial lipase.

Methanol is often employed in biocatalysis with the purpose of increasing substrates solubility or as the acyl acceptor in transesterification reactions, but inhibitory effects are observed in several cases. We have studied the influence of methanol on the catalytic activity and on the conformation of the lipase from Burkholderia glumae, which is reported to be highly methanol tolerant if compared with other lipases. We detected highest activity in the presence of 50-70 % methanol. Under these conditions, however, the enzyme stability is perturbed, leading to gradual protein unfolding and finally to aggregation. These results surmise that, for this lipase, methanol-induced deactivation does not depend on inhibition of catalytic activity but rather on negative effects on the conformational stability of the catalyst.

Enzymatic transesterification monitored by an easy-to-use Fourier transform infrared spectroscopy method.

Transesterification of triglycerides with short chain alcohols is the key reaction in biodiesel production, in addition to other applications in chemical synthesis. However, it is crucial to optimize reaction conditions to make enzymatic transesterification a cost-effective and competitive process. In this work, a new, easy Fourier transform infrared (FTIR) spectroscopic approach for monitoring the transesterification reaction is reported and compared with a gas-chromatographic method. The concentration of the total methyl esters in the reaction mixture is determined from the peak intensity at ∼1435 cm(-1) in the second derivatives of the FTIR absorption spectra using a linear regression calibration. Interestingly, we found that the use of second derivatives allows an accurate determination of the methyl esters without the interference of free fatty acids. Moreover, information on substrate hydrolysis can be obtained within the same measurement by the infrared absorption at ∼1709 cm(-1) . We applied this approach to monitor methanolysis and hydrolysis reactions catalyzed by different commercial lipases, which displayed different sensitivities to methanol inhibition. Therefore, the FTIR approach reported in this work represents a rapid, inexpensive, and accurate method to monitor enzymatic transesterification, requiring very limited sample preparation and a simple statistical analysis of the spectroscopic data.

Urological complications following inguinal hernioplasty.

Aim of this paper is to report a systematic review of the literature about the incidence and putative mechanisms of genital tract injuries following open and laparoscopic herniorraphy and their effects on sexual function and fertility and to point out the measures of prevention and of treatment. The most frequently described events have been intraoperative complications as bladder or spermatic cord structure damage, immediate postoperative complications as ischaemic orchitis, urinary retention, urinary tract infection, hydrocele or scrotal haematoma and bacterial orchitis, or long-term complications as chronic orchialgia, testis atrophy, sexual dysfunction and infertility. The evidence of literature shows that urological complication after hernioplasty are under-reported. Only a small number of studies to date have essentially dealt with sexual quality of life after inguinal hernia surgical repair. The sexual needs of patients with groin hernias are rarely discussed. Extensive laparoscopic procedures, due to the need of learning curve, have increased the risk of vas damage and infertility in young patients candidate to hernioplasty. Early diagnosis prevents urological complication as well as possible legal claims after hernia repair: it should be include careful history, objective and subjective symptoms and signs of uro-genital pathologies, lab data when necessary, immediate eco-color-Doppler imaging and urgent urological consultation. Despite the lack of prospective randomized trials, there is a growing evidence in literature about positive impact of hernioplasty on sexual function, encouraging future studies on this issue.

Microbiological follow-up of nosocomial infections in a single urological center.

BACKGROUND: To analyze data from the cultural examinations of different biological fluids, obtained from urologic patients from January 2007 to April 2010, in order to describe the incidence of infections in our setting. METHODS: In the period of reference a urine culture was carried out for every patient admitted, in case of suspected urinary tract infection, a blood culture in case of suspected sepsis, and a wound culture in case of wound infection. RESULTS: In the period of investigation 321 patients developed some kind of infection: 589 positive isolations obtained from cultural examinations have been diagnosed in urine (63%), blood (6%), surgical wound (6%), venous central catheter (7%) and other sites (18%) (tip of ureteral and bladder catheters). The most commonly isolated pathogenic agent for all the sites of infection has been Escherichia coli (22.5%). In urine, the most frequently isolated species have been Escherichia coli (27.8%), Enterococcus (12.5%), and Candida spp (9.3%). Escherichia coli (22.9%), Pseudomonas (5.7%), and Staphylococcus aureus (3.5%) were the most frequently found pathogenic agents responsible for sepsis, compared to others. In the period of investigation we have recorded 35 episodes of sepsis. CONCLUSIONS: Empiric antibiotic therapy is frequent in cases of clinical evidence of infection, before the identification of the causative microorganism is available; therefore, it is important to know which are the bacterial species mainly responsible for these specific infections. We need continuous surveillance of infections and the improvement in the use of antibiotic therapy in order to limit the antimicrobial resistance.

Late toxicity in Wilms tumor patients treated with radiotherapy at 15 years of median follow-up.

BACKGROUND: We report the radiation-induced late morbidity observed in our prospective series of Wilms tumor patients treated at the Second University of Naples. METHODS: From April 1981 to April 2000, 98 patients were referred at our institution for treatment of Wilms tumor. Among them, 51 underwent radiotherapy and 34 patients had a minimum follow-up of 5 years. Doses of irradiation and treatment portals were those recommended by the guidelines of the Italian Association of Haematology and Paediatric Oncology according to risk stratification. All eligible patients were reviewed for follow-up every 6 months. Median follow-up was 181 months (range 60 to 264 months). RESULTS: Eleven out of 34 patients (32%) did not suffer from any significant late side effect. Out of the remaining 23 (68%), 14 (41%) suffered from scoliosis presenting between 60 and 180 months from completion of treatment. Muscular hypoplasia, length inequality, kyphosis, and iliac wing hypoplasia were seen respectively, in 4 (12%), 4 (12%), 5 (15%), and 3 (9%) patients. The incidence of intestinal occlusion was 20%. One patient had chronic renal insufficiency. Four out of 13 female patients reported ovarian failure. Three out of the 7 patients who had radiotherapy to the lung developed radiation-pneumonitis. Radiation-induced heart disease was seen in 3 (9%) patients. Three patients (9%) suffered from second malignancies arising within the irradiated volume. CONCLUSIONS: Our data confirm the high incidence of late radiation morbidity in patients undergoing adjuvant radiotherapy for Wilms tumor. For most organ systems there is a correlation between total dose, morbidity rates, and degree of severity.

Sorafenib's inhibition of prostate cancer growth in transgenic adenocarcinoma mouse prostate mice and its differential effects on endothelial and pericyte growth during tumor angiogenesis.

OBJECTIVE: To evaluate Sorafenib's efficacy (60 mg/kg/d per os) in preventing the transformation of high grade prostate intraepithelial neoplasia (HGPIN) into adenocarcinoma (ADC) and in inhibiting the onset and progression of poorly differentiated carcinoma (PDC) in transgenic adenocarcinoma mouse prostate (TRAMP) mice. STUDY DESIGN: Forty-four TRAMP mice were randomly divided into 2 groups of 22 and assigned to daily treatment by gavage with vehicle only or Sorafenib from the 10th to the 26th week of age. At 26 weeks of age the mice were killed, and their genitourinary apparatus was removed and examined by histology, immunohistochemistry and confocal microscopy. RESULTS: Sorafenib reduced HGPIN growth and progression to ADC and was probably also effective in PDC inhibition. The major effect of Sorafenib was on tumor angiogenesis. Interestingly a dissociation between endothelial cells and pericytes was noted in treated PDC since inhibition of pericyte recruitment was less complete than that of endothelial cells. CONCLUSION: Sorafenib's potent antiangiogenic action may be supposed to be exerted primarily by inhibiting endothelial proliferation and sprouting, whereas its inhibition of pericyte recruitment and maturation is less complete. These observations suggest that Sorafenib's effects could be improved by the joint employment of substances capable of interfering with the recruitment and organization of pericytes.

Paraneoplastic syndromes in patients with urological malignancies.

INTRODUCTION: Paraneoplastic syndromes (PNS) may represent the main clinical problem in cancer patients; however, the knowledge of their clinical aspect remains quite poor among urologists. OBJECTIVE: To provide urologists with an overview on main clinical aspects of PNS that have been reported to be associated to urological cancers. METHODS: Literature search of peer-reviewed papers published by July 2008. RESULTS: All genitourinary tumors can cause a PNS, and renal cell carcinoma is the most frequent urological malignancy involved. Prostate cancer is the second urological tumor associated with PNS which, conversely, are uncommon in bladder cancer and rare in testicular cancer. Tumor neuroendocrine differentiation is involved in most endocrine PNS. Neurologic PNS are very uncommon but may dominate the clinical picture and need a high suspicion index to be recognized. Important advances have been made on radionuclide scan methods in order to detect the primary tumor. The most effective treatment strategy is always represented by the radical therapy of the underlying cancer, but specific therapeutic options are sometimes available. CONCLUSIONS: Endocrine PNS are frequently associated with urological cancers, especially renal and prostate carcinoma. PNS have been rarely reported in association with cancers of bladder, urethra and testicle.

Scintigraphic evaluation of oesophageal transit during radiotherapy to the mediastinum.

BACKGROUND: To quantitatively evaluate radiation-induced impaired oesophageal transit with oesophageal transit scintigraphy and to assess the relationships between acute oesophagitis symptoms and dysmotility. METHODS: Between January 1996 and November 1998, 11 patients affected by non-small-cell carcinoma of the lung not directly involving the oesophagus, requiring adjuvant external beam radiotherapy (RT) to the mediastinum were enrolled. Oesophageal transit scans with liquid and semisolid bolus were performed at three pre-defined times: before (T0) and during radiation at 10 Gy (T1) and 30 Gy (T2). Two parameters were obtained for evaluation: 1) mean transit time (MTT); and 2) ratio between peak activity and residual activity at 40 seconds (ER-40s). Acute radiation toxicity was scored according to the joint EORTC-RTOG criteria. Mean values with standard deviation were calculated for all parameters. Analysis of variance (ANOVA) tests and paired t-Tests for all values were performed. RESULTS: An increase in the ER-40s from T0 to T1 or T2 was seen in 9 of 11 patients (82%). The mean ER-40s value for all patients increased from 0.8306 (T0) to 0.8612 (T1) and 0.8658 (T2). These differences were statistically significant (p < 0.05) in two paired t-Tests at T0 versus T2 time: overall mean ER-40s and upright ER-40s (p = 0.041 and p = 0.032, respectively). Seven patients (63%) showed a slight increase in the mean MTT value during irradiation but no statistically significant differences in MTT parameters were found between T0, T1 and T2 (p > 0.05). CONCLUSION: Using oesophageal scintigraphy we were able to detect early alterations of oesophageal transit during the third week of thoracic RT.

Extracorporeal shockwave lithotripsy in pediatrics.

Since its introduction in 1980, extracorporeal shockwave lithotripsy (SWL) has become the first therapeutic option in most cases of upper-tract urolithiasis, and the technique has been used for pediatric renal stones since the first report of success in 1986. Lithotripter effectiveness depends on the power expressed at the focal point. Closely correlated with the power is the pain produced by the shockwaves. By reducing the dimensions of the focus, it becomes possible to treat the patient without anesthesia or analgesia but at the cost of a higher re-treatment rate. Older children often tolerate SWL under intravenous sedation, and minimal anesthesia is applicable for most patients treated with second- and third-generation lithotripters. Ureteral stenting before SWL has been controversial. Current data suggest that preoperative stent placement should be reserved for a few specific cases. Stone-free rates in pediatric SWL exceed 70% at 3 months, with the rate reaching 100% in many series. Even the low-birth-weight infant can be treated with a stone-free as high as 100%. How can one explain the good results? Possible explanations include the lesser length of the child's ureter, which partially compensates for the narrower lumen. Moreover, the pediatric ureter is more elastic and distensible, which facilitates passage of stone fragments and prevents impaction. Another factor is shockwave reproduction in the body: there is a 10% to 20% damping of shockwave energy as it travels through 6 cm of body tissue, so the small body volume of the child allows the shockwaves to be transmitted with little loss of energy. There are several concerns regarding the possible detrimental effect of shockwaves on growing kidneys. Various renal injures have been documented with all type of lithotripters. On the other hand, several studies have not shown adverse effects. In general, SWL is considered to be the method of choice for managing the majority of urinary stones in children of all ages. Re-treatments improve the stone-free rate, often raising it to 100%. Among the predictors of success, stone size seems to be the most important. In the absence of guidelines, selecting the appropriate treatment modality for each child requires planning and depends on instrument availability and local expertise.

A visual query-by-example image database for chest CT images: potential role as a decision and educational support tool for radiologists.

Primary reading or further evaluation of diagnostic imaging examination often needs a comparison between the actual findings and the relevant prior images of the same patient or similar radiological data found in other patients. This support is of clinical importance and may have significant effects on physicians' examination reading efficiency, service-quality, and work satisfaction. We developed a visual query-by-example image database for storing and retrieving chest CT images by means of a visual browser Image Management Environment (IME) and tested its retrieval efficiency. The visual browser IME included four fundamental features (segmentation, indexing, quick load and recall, user-friendly interface) in an integrated graphical environment for a user-friendly image database management. The system was tested on a database of 2000 chest CT images, randomly chosen from the digital archives of our institutions. A sample of eight heterogeneous images were used as queries and, for each of them a team of three expert radiologists selected the most similar images from the database (a set of 15 images containing similar abnormalities in the same position of the query). The sensitivity and the positive predictive factor, both averaged over the 8 test queries and 15 answers, were respectively 0.975 and 0.91 The IME system is currently under evaluation at our institutions as an experimental application. We consider it a useful work-in-progress tool for clinical practice facilitating searches for a variety of radiological tasks.

Anterior cruciate ligament reconstruction: bone-patellar tendon-bone compared with double semitendinosus and gracilis tendon grafts. A prospective, randomized clinical trial.

BACKGROUND: The choice of graft for anterior cruciate ligament reconstruction is a matter of debate, with patellar and hamstring tendons being the two most popular autologous graft options. The objective of this study was to determine in a prospective, randomized clinical trial whether two grafts (bone-patellar tendon-bone or doubled hamstring tendons) fixed with modern devices affect the two-year minimum clinical and radiographic outcomes of anterior cruciate ligament reconstruction. METHODS: One hundred and twenty patients with a chronic unilateral rupture of the anterior cruciate ligament underwent arthroscopically assisted reconstruction with use of either autologous bone-patellar tendon-bone or doubled hamstring tendon grafts, in a strictly alternating manner. Both groups were comparable with regard to demographic data, preoperative activity level, mechanism of injury, interval between the injury and the operation, and the amount of knee laxity present preoperatively. The same well-proven surgical technique and aggressive controlled rehabilitation was used. An independent observer, who was blinded with regard to the involved leg and the type of graft, performed the outcome assessment with use of a visual analog scale, the new International Knee Documentation Committee form, the Knee Injury and Osteoarthritis Outcome Score, the Functional Knee Score for Anterior Knee Pain, and an arthrometric and an isokinetic dynamometric evaluation. Radiographs were also made. RESULTS: At the two-year follow-up evaluation, no differences were found in terms of the visual analog score, the Knee Injury and Osteoarthritis Outcome Score, the new International Knee Documentation Committee subjective and objective evaluation scores, the KT-1000 side-to-side laxity measurements, the Functional Knee Score for Anterior Knee Pain, muscle strength recovery, or return to sports activities. In the bone-patellar tendon-bone group, we found a higher prevalence of postoperative kneeling discomfort (p < 0.01) and an increased area of decreased skin sensitivity (p < 0.001). In the hamstring tendon group, we recorded a higher prevalence of femoral tunnel widening (p < 0.01). In this group, a correlation was also found between medial meniscectomy and an increased prevalence of pivot-shift glide (p = 0.035). CONCLUSIONS: We believe that, with use of accurate and proven surgical and rehabilitation techniques, both grafts are an equivalent option for anterior cruciate ligament reconstruction.

Multi-detector row CT for depicting anatomic features of cephalothoracopagus varieties: revised approach.

Conjoined twins can be classified on the basis of the site of union; thus, three main types can be described: (a) ventral union, (b) dorsal union, and (c) rarer forms of union. Ventral union is characterized by the fusion of the two embryos on the ventral side (eg, the abdomen). Dorsal union twins are joined on the dorsal aspect (eg, the vertebral column or occipital bone). Ventral union twins include the group of crucipage twins (ventral midline structures at 90 degrees to the dorsal midline structures), which show interesting features in the organization of the midline. Twins conjoined at the head and chest are called cephalothoracopagus twins. The cephalothoracopagus variety called "Janus" is characterized by the presence of two opposite faces, which are composite structures half of which belong to one twin and half to the other. A complete set of five variants of cephalothoracopagus is presented and, to the authors' knowledge, analyzed for the first time with multi-detector row helical computed tomography. This modality is an invaluable tool for obtaining high-resolution images of the brain, chest, abdomen, and spine and for demonstrating organ position, shared viscera, and limited vascular anatomy. In addition, data acquired in three-dimensional volumes can further be manipulated and then reconstructed. For this purpose, the authors developed dedicated software for three-dimensional reconstruction to analyze data from specimens preserved in formalin. The anatomic findings are discussed here for their embryologic value and to revise the classification of cephalothoracopagus twins. These data offer detailed information for accurate comprehension of imaging studies and for theoretical studies concerning the formation of several anatomic structures.