Development of a geometrically accurate and adaptable finite element head model for impact simulation: the Naval Research Laboratory-Simpleware Head Model.

This study demonstrates a novel model generation methodology that addresses several limitations of conventional finite element head models (FEHM). By operating chiefly in image space, new structures can be incorporated or merged, and the mesh either decimated or refined both locally and globally. This methodology is employed in the development of a highly bio-fidelic FEHM from high-resolution scan data. The model is adaptable and presented here in a form optimised for impact and blast simulations. The accuracy and feasibility of the model are successfully demonstrated against a widely used experimental benchmark in impact loading and through the investigation of potential brain injury under blast overpressure loading.

Survival Outcomes Following Pediatric Liver Transplantation (Pedi-SOFT) Score: A Novel Predictive Index.

A prognostic index to predict survival after liver transplantation could address several clinical needs. Here, we devised a scoring system that predicts recipient survival after pediatric liver transplantation. We used univariate and multivariate analysis on 4565 pediatric liver transplant recipients data and identified independent recipient and donor risk factors for posttransplant mortality at 3 months. Multiple imputation was used to account for missing variables. We identified five factors as significant predictors of recipient mortality after pediatric liver transplantation: two previous transplants (OR 5.88, CI 2.88-12.01), one previous transplant (OR 2.54, CI 1.75-3.68), life support (OR 3.68, CI 2.39-5.67), renal insufficiency (OR 2.66, CI 1.84-3.84), recipient weight under 6 kilograms (OR 1.67, CI 1.12-2.36) and cadaveric technical variant allograft (OR 1.38, CI 1.03-1.83). The Survival Outcomes Following Pediatric Liver Transplant score assigns weighted risk points to each of these factors in a scoring system to predict 3-month recipient survival after liver transplantation with a C-statistic of 0.74. Although quite accurate when compared with other posttransplant survival models, we would not advocate individual clinical application of the index.

An early regional experience with expansion of Milan Criteria for liver transplant recipients.

The Milan Criteria (MC) showed that orthotopic liver transplantation (OLT) was an effective treatment for patients with nonresectable, nonmetastatic HCC. There is growing evidence that expanding the MC does not adversely affect patient or allograft survival following OLT. The adult OLT programs in UNOS Region 4 reached an agreement allowing lesions outside MC (one lesion <6 cm, ≤3 lesions, none >5 cm and total diameter <9 cm-[R4 T3]) to receive the same exception points as MC lesions. Kaplan-Meier curves and log-rank tests were used to compare survival data. Chi-squared and Mann-Whitney U tests were used to compare patient data. A p-value of <0.05 was considered significant. All statistical analyses were performed on SPSS 15 (SPSS, Chicago, IL). Four hundred and forty-five patients were transplanted for HCC (363-MC and 82-R4 T3). Patient demographics were found to be similar between the two groups. Three year patient, allograft and recurrence free survival between MC and R4 T3 were found to be 72.9% and 77.1%, 71% and 70.2% and 90.5% and 86.9%, respectively (all p > 0.05). We report the first regionalized multicenter, prospective study showing benefit of OLT in patients exceeding MC based on preoperative imaging.

Airway injury complicating excision of thyroglossal duct cysts.

OBJECTIVES: We report on four cases of thyroglossal duct cyst (TGDC) excision using the Sistrunk procedure (resection of the mid-portion of the hyoid bone in continuity with a thyroglossal duct cyst tract) in which the airway was significantly injured. The patterns of injury, their treatment and outcomes as well as preventative measures are detailed. METHODS: Retrospective analysis of four patients referred to a tertiary medical center after sustaining injury to the cricothyroid membrane and/or thyroid cartilages while undergoing a Sistrunk excision of a TGDC. RESULTS: Three patients were repaired after a delay; one patient was immediately repaired. All four patients required application of cartilage grafts, and all ultimately required tracheotomy. Decannulation was achieved in the four patients after an average of 4.5 months, and none suffered from aspiration. Voice outcomes were poor in 3/4. CONCLUSIONS: The Sistrunk procedure has been advocated for TGDC excision, citing a low recurrence rate. However, if the thyroid cartilage is mistaken for the hyoid bone, significant airway injury occurs. Urgent laryngotracheoplasty is indicated, but poor voice outcomes are anticipated. SIGNIFICANCE: Surgeons employing the Sistrunk procedure to excise TGDC must remain oriented to midline cervical anatomy, particularly as the hyoid my override the thyroid notch in young children, placing the larynx at risk for significant injury.

Topical mitomycin application after laryngotracheal reconstruction: a randomized, double-blind, placebo-controlled trial.

OBJECTIVE: To explore the effect of mitomycin treatment on the pediatric airway following laryngotracheal reconstruction. DESIGN: Randomized, double-blind, placebo-controlled trial. PATIENTS: Children aged 2 to 17 years with subglottic or upper tracheal stenosis undergoing laryngotracheal reconstruction at a single, tertiary care, children's hospital. INTERVENTION: At the time of extubation or stent removal, the children underwent bronchoscopy and 0.4 mg/mL (2 mL of a 0.2-mg/mL solution of either mitomycin or an equal volume of isotonic sodium chloride was directly applied to the subglottic region for a single application of 2 minutes. These children then underwent interval endoscopy at 2 weeks, 6 weeks, and 3 months postoperatively for assessment of their airways. RESULTS: Granulation tissue was graded on a scale of 0 (none) to 4 (near-total or total occlusion). Videotapes of endoscopies were independently observed and graded by 3 pediatric otolaryngology fellows with a subsequent interobserver agreement of 91.6%. The results were then dichotomized to represent a single cohort in which further surgical intervention would be required and another separate cohort in which further surgery would not be required. At the 1-year mark, interim analysis was performed by a Data Safety and Monitoring Committee. At this time, 13 children had been randomized to the mitomycin-treated arm of the study and 11 children to the placebo-treated arm. A 2-tailed Fisher exact test revealed a value of 1.00. The Data Monitoring and Safety Committee advised that the trial should be stopped because the distributions between the 2 populations were almost identical. CONCLUSION: We cannot reject the null hypothesis that a single topical dose of mitomycin exerts an equal benefit as does isotonic sodium chloride when applied to the pediatric airway after laryngotracheal reconstruction.

Posttonsillectomy hemorrhage: what is it and what should be recorded?

OBJECTIVES: To report on our incidence of posttonsillectomy hemorrhage and to define what constituted posttonsillectomy bleeding. DESIGN: Retrospective study. SETTING: Tertiary care children's hospital and a local satellite facility. PATIENTS: A series of 1438 consecutive patients who had undergone either tonsillectomy or adenotonsillectomy between January 1, 1999, and December 31, 1999. INTERVENTION: During this period, parents were instructed to return with their children for clinical evaluation if any blood was seen in the postoperative period. MAIN OUTCOME MEASURES: Postoperative day of evaluation, age, sex, location of bleeding, management strategy, length of hospital admission, and any bleeding disorders were noted for each patient. RESULTS: A total of 112 patients underwent evaluation 134 times. Of these patients, 96 required only 1 evaluation and 16 required more than 1 evaluation. All patients who had more than 1 evaluation required intervention. The total number of children requiring intervention for posttonsillectomy hemorrhage was 51 (3.5%) of the 1438 patients. Female patients were more likely than male patients to return for evaluation. Patients who were 12 years and older were the most likely and those 3 years and younger were the least likely to have posttonsillectomy hemorrhage. The most common time from surgery to initial evaluation for hemorrhage was 6 days. CONCLUSIONS: By reviewing our own criteria for defining and recording posttonsillectomy hemorrhage, we conclude that posttonsillectomy hemorrhage is defined differently in the literature. This supports the need for a standard definition to allow for direct comparisons.

Duration of stenting in single-stage laryngotracheal reconstruction with anterior costal cartilage grafts.

In single-stage laryngotracheal reconstruction (ss-LTR), the endotracheal tube is used as a stent. The optimal duration of stenting is not known. The stenting period requires a stay in the intensive care unit, as the patient is intubated. Sedation and, rarely, paralysis may be required. An analysis from a prospectively collected database was performed to investigate the effect of length of stenting on the outcome of ss-LTR. The outcomes used were reintubation rate and postoperative tracheostomy rate. Patients with anterior costal graft ss-LTR were selected, as they had undergone similar procedures and have similar stenosis types and grades. In 101 patients, the duration of stenting ranged from 2 to 14 days (mean, 7 days; SD, 2.6 days). No significant correlation was found between the number of days stented and the reintubation rate or the postoperative tracheostomy rate. Patients stented for longer than I week were an average of 15 months younger than those stented for less than 1 week; however, the stenosis grades for the two populations were equivalent. The differences in rates of reintubation (p = .68) and postoperative tracheostomy (p = .52) in these 2 groups were not significant. For patients undergoing ss-LTR with anterior costal cartilage grafts, no correlation was found between the number of days stented (intubated) and the reintubation rate or the postoperative tracheostomy rate.

Role of laryngoscopy, dual pH probe monitoring, and laryngeal mucosal biopsy in the diagnosis of pharyngoesophageal reflux.

There is no standard for determining significant pharyngoesophageal reflux. This prospective blind comparison study compared dual pH probe studies, direct laryngoscopy, and mucosal biopsy in children without symptoms of gastroesophageal reflux who underwent airway evaluation. Significant reflux to the lower esophageal probe did not correlate with statistical significance with reflux to the upper probe. In this group of asymptomatic patients, a positive lower pH probe finding did not correlate with upper or lower esophageal mucosal inflammation. Eosinophilia in the esophageal mucosa is diagnostic of gastroesophageal reflux disease, and was seen in 5 of the laryngeal biopsies. A weak correlation was seen between positive findings at laryngoscopy and positive posterior cricoid biopsy in this group. There may be no consistent way to predict significant pharyngoesophageal reflux in asymptomatic patients. Single-probe pH testing will not predict significant pharyngoesophageal reflux with mucosal changes. Laryngoscopy and upper pH probe findings only weakly correlate with significant histologic findings. Laryngeal and posterior cricoid biopsy may be the only sensitive test for mucosal injury. Clinical trials of empiric antireflux therapy should be used to determine whether the laryngeal changes seen in these patients are reversible.

Cricotracheal resection in children.

OBJECTIVE: To review our experience with cricotracheal resection in a pediatric population. DESIGN: Prospective case review of a cohort of patients undergoing cricotracheal resection. SETTING: Tertiary care pediatric hospital. PATIENTS: Forty-four consecutive patients undergoing cricotracheal resection between January 1, 1993, and December 31, 1998. MAIN OUTCOME MEASURES: Decannulation rates. RESULTS: Thirty-eight (86%) of the 44 children are decannulated. The ultimate decannulation rate was independent of the presenting grade of subglottic stenosis. Fourteen children (100%) had a primary cricotracheal resection; all are decannulated. Twenty-one children had a salvage cricotracheal resection, and 19 (90%) are decannulated. Nine children had an extended cricotracheal resection, of whom 5 (56%) are decannulated. A primary cricotracheal resection was performed on a child on whom no previous open airway procedure had been performed. A salvage cricotracheal resection was performed on a child on whom previous open airway reconstruction had not resulted in an adequate airway. An extended cricotracheal resection was performed on a child on whom the cricotracheal resection was combined with a second procedure, either additional expansion cartilage grafting or an open arytenoid procedure. Most of these children had complex airway pathologic conditions. CONCLUSION: Cricotracheal resection complements standard laryngotracheal reconstruction techniques in a pediatric population.

Arytenoid prolapse as a consequence of cricotracheal resection in children.

Cricotracheal resection (CTR) is a technique introduced comparatively recently for treating severe laryngotracheal stenosis in children. The recognized complications of CTR include recurrent laryngeal nerve damage, anastomotic dehiscence, and restenosis. We describe a further complication of CTR, namely, prolapse of the arytenoid cartilage. The presentation may be late, with symptoms of shortness of breath on exertion and nocturnal stertor with a poor sleep pattern, or the prolapse may be an asymptomatic incidental finding. The diagnosis is performed with flexible nasopharyngoscopy with the patient unanesthetized, or with rigid endoscopy with the patient lightly anesthetized and spontaneously ventilating. The affected arytenoid cartilage is noted to prolapse anteriorly and medially with inspiration, partly obstructing the airway. If treatment is required, endoscopic laser partial arytenoidectomy is effective. In a series of 44 children who underwent CTR, 20 were noted to develop arytenoid prolapse after operation. Twelve were asymptomatic, and 8 required laser arytenoidectomy, 2 of whom now require continuous positive airway pressure for moderate supraglottic collapse.

Postoperative management of children after single-stage laryngotracheal reconstruction.

OBJECTIVE: To report the safety and efficacy of a postoperative approach that avoids pharmacologic and physical restraints and allows liberal physical activity after single-stage laryngotracheal reconstruction in children. DESIGN: Retrospective study. SETTING: Tertiary care pediatric intensive care unit. PATIENTS: One hundred thirty-three children who underwent single-stage laryngotracheal reconstruction, including laryngotracheoplasty, tracheal resection, and cricotracheal resection. INTERVENTIONS: Five-year period of data collection regarding postoperative care and complications. MEASUREMENTS AND MAIN RESULTS: The medical records of all patients (age range, 2-336 months; mean age +/- SEM, 66 +/- 5 months) who underwent single-stage laryngotracheoplasty, tracheal resection, or cricotracheal resection between 1993 and 1998 were reviewed. Tracheally intubated, awake, and unrestrained patients (group 1, n = 54; mean age, 113 +/- 8 months) were compared with tracheally intubated, sedated, and restrained patients (group 2, n = 79; mean age, 33 +/- 3 months). Pediatric intensive care unit length of stay was less in group 1 in comparison with group 2 patients (11.2 +/- 0.5 days vs. 13.7 +/- 0.6 days; p = .007). Hospital length of stay was less in group 1 than group 2 patients (16.7 +/- 1.0 days vs. 21.1 +/- 1.1 days; p = .01). Adverse events were fewer in group 1 compared with group 2 patients: atelectasis, 44% vs. 73% (p < .001); postextubation stridor, 22% vs. 53% (p < .001); and withdrawal syndromes, 0% vs. 43% (p < .001). The occurrence of pneumonia, airleak syndromes, unplanned extubation, and aspiration events was not different between groups. CONCLUSIONS: For developmentally appropriate children, postoperative management after single-stage laryngotracheal reconstruction does not require the use of physical and pharmacologic restraints. Older children who are not sedated or restrained and who are allowed liberal physical activity have shorter pediatric intensive care unit and hospital lengths of stay, and a decreased incidence of postoperative adverse events. Centers performing single-stage laryngotracheal reconstruction should consider a postoperative management strategy that avoids sedatives, muscle relaxants, and physical restraints, and allows liberal bedside physical activity in developmentally appropriate children.

Primary neurilemoma of the thyroid gland: a case report.

Primary nonepithelial tumors of the thyroid gland are rare. We present the case of a neurilemoma of the right lobe of the thyroid gland in a 20-year-old female patient. The tumor was asymptomatic and measured 2.5 x 1.2 cm in size. Histologic examination was consistent with an Antoni A-type neurilemoma. The tumor was excised without difficulty. Only 12 other cases of neurilemomas of the thyroid gland have been reported in the literature. We discuss the clinical, radiologic, and pathologic findings of this rare tumor.

Acquired total (grade 4) subglottic stenosis in children.

Pediatric acquired total subglottic stenosis (SGS) is a challenging problem. The management of these patients has evolved at our institution over the past 25 years. We conducted a retrospective study to evaluate the surgical management and outcomes of children with grade 4 SGS. Fifty-six patients have presented with acquired grade 4 SGS since 1981. The causes included previous surgery (34), prolonged intubation (15), bums (1), and unknown causes (6). Of the 56 patients, 44 (79%) were decannulated; 120 total procedures were performed, and 39 patients (70%) required more than 1 procedure for decannulation. The decannulation rate has risen from 67% in the 1980s to 86% in the 1990s. Patients who underwent cricotracheal resection (CTR) had a higher decannulation rate than patients who underwent laryngotracheal reconstruction (LTR) with anterior and posterior costal cartilage grafting (CCG) (92% versus 81%), and were less likely to need additional open procedures to achieve decannulation (18% versus 46%). The decannulation rate for children with grade 4 SGS has improved because of advances in surgical technique. Currently, the principal operations used at our institution are 1) CTR and 2) LTR with anterior and posterior CCG. There was a trend toward a higher decannulation rate in patients who underwent CTR, and they were less likely to require further reconstructive surgery before decannulation.

Laryngotracheoplasty for subglottic stenosis in Down Syndrome children: the Cincinnati experience.

Previous studies from our institution have noted difficulties in the surgical repair of subglottic stenosis (SGS) in children with Down Syndrome. The objectives of this paper were to update our 15 year experience in the Down Syndrome patient population, compare our results with our overall series of laryngotracheoplasty for SGS, and to report on the increased incidence of posterior glottic stenosis (PGS) within this group of patients. Medical records of all children with SGS and Down Syndrome evaluated between 1982 and 1997 were reviewed for history of prior intubation, tracheotomy, gastroesophageal reflux disease (GERD), pre-operative SGS grade, and decannulation. From this review several conclusions have been drawn. First, the risk factors for SGS appear to be the same in the Down Syndrome group as the general population. Second, SGS continues to be more prevalent among children with Down Syndrome than among children in the general population. Third, we have now found a higher rate of PGS within these patients when compared to our overall series. Finally, it now seems that our decannulation rates in Down Syndrome children are approaching our overall series results.

Surgery for pediatric subglottic stenosis: disease-specific outcomes.

To set the foundation to develop a disease-based, operation-specific model to predict the outcome of pediatric airway reconstruction surgery, we performed a retrospective database review of children operated on at a single, tertiary-care children's hospital. Over the 12-year period 1988 to 2000, a total of 1,296 airway reconstruction procedures were performed. Out of these, charts were identified for 199 children who underwent laryngotracheal reconstruction for a sole diagnosis of subglottic stenosis. Children were excluded from the study if their disorder included supraglottic, glottic, or upper tracheal disease. The main outcome measures were Myer-Cotton grade-specific decannulation and extubation rates, including both operation-specific and overall results. There were 101 children who underwent double-stage laryngotracheal reconstruction. The operation-specific decannulation rates for Myer-Cotton grades 2, 3, and 4 were 85% (18/21), 37% (23/61), and 50% (7/14) (chi2 analysis, p = .0007). The overall decannulation rates were 95% (20/21), 74% (45/61), and 86% (12/14) (chi2 analysis, p = .04). There were 98 children who underwent single-stage laryngotracheal reconstruction. The operation-specific extubation rates for Myer-Cotton grades 2, 3, and 4 were 82% (37/45), 79% (34/43), and 67% (2/3) (chi2 analysis, p = .63). The overall extubation rates were 100% (45/45), 86% (37/43), and 100% (3/3) (chi2 analysis, p = .03). Logistic regression analysis showed no effect of age (less than or greater than 2 years of age) on operation-specific or overall outcome parameters. We conclude that laryngotracheal reconstruction for pediatric subglottic stenosis remains a challenging set of procedures in which multiple operations may be required to achieve eventual extubation or decannulation. Children with Myer-Cotton grade 3 or 4 disease continue to represent a significant challenge, and refinements of techniques are being examined to address this subset of children. Disease-based, operation-specific outcome statistics are the first step in the development of a meaningful predictive model.

Laryngotracheal reconstruction and the hidden airway lesion.

OBJECTIVE: Single-stage laryngotracheal reconstruction (SSLTR) is an increasingly common technique to achieve decannulation of patients with laryngotracheal stenosis. In a proportion of cases airway distress on extubation may be attributed to a dynamic second airway lesion not diagnosed before surgery. Our aim is to describe our recent experience with these frustrating patients. METHODS: Between July 1997 and July 1999 we prospectively followed patients who underwent SSLTR and experienced difficulty after extubation owing to an unsuspected second airway lesion. RESULTS: During this 24-month period we performed 80 SSLTRs. In six surgeries performed on five patients, a second airway lesion complicated extubation. In five patients the second lesion was not diagnosed before surgery because there was significant airway stenosis and tracheotomy. The sixth patient was transferred to our care intubated. In all cases the airway surgery for the dominant lesion was technically successful, but revealed a second dynamic lesion. There were three cases of tracheomalacia, two cases of laryngomalacia, and one case of arytenoid prolapse. All patients required intervention. Tracheotomy was required in four patients. CONCLUSIONS: Failure to achieve extubation after SSLTR may be caused by a dynamic second airway lesion that was previously disguised by a more dominant airway lesion. Surgical repair of the dominant lesion will allow manifestation of the dynamic lesion due to the Bernoulli effect. The combination of a tracheotomy and a dominant airway lesion limits airflow and potentially disguises the situation.

Pediatric laryngopharyngeal sensory testing during flexible endoscopic evaluation of swallowing: feasible and correlative.

Laryngopharyngeal sensory testing can predict aspiration risk in adult patients. Its feasibility and potential role in the evaluation of pediatric swallowing is undetermined. The goals of this study were to determine the feasibility of performing laryngopharyngeal sensory testing in awake pediatric patients and to assess whether the sensory testing results correlated with aspiration during a feeding assessment or correlated with a history of pneumonia. Fiberoptic endoscopic evaluation of swallowing with sensory testing was performed in 100 pediatric patients who were evaluated for feeding and swallowing disorders. The swallowing function parameters evaluated were pooled secretions, laryngeal penetration, and aspiration. The laryngopharyngeal sensory tests were performed by delivering a pressure-controlled and duration-controlled air pulse to the aryepiglottic fold through a flexible laryngoscope to induce the laryngeal adductor response (LAR). The air pulse stimulus ranged in intensity from 3 to 10 mm Hg. The patients tested ranged from 1 month to 24 years of age, with a median age of 2.7 years. Sensory testing was completed in 92% of patients. Patients who had an LAR at less than 4 mm Hg rarely if ever had episodes of laryngeal penetration or aspiration. Those with an LAR at 4 to 10 mm Hg had variable amounts of aspiration and laryngeal penetration. The LAR could not be elicited at the maximum level of intensity (10 mm Hg) in 22 patients, who demonstrated severe laryngeal penetration and/or aspiration. Elevated laryngopharyngeal sensory thresholds correlated positively with previous clinical diagnoses of recurrent pneumonia, neurologic disorders, and gastroesophageal reflux, and correlated positively with findings of pooled secretions, laryngeal penetration, and aspiration. Laryngopharyngeal sensory testing in children is feasible and correlative.

Single-stage laryngotracheal reconstruction in children: a review of 200 cases.

OBJECTIVE: We reviewed our experience with pediatric single-stage laryngotracheal reconstruction (SSLTR) to identify factors that affect postoperative outcomes, including the need for reintubation and tracheostomy. STUDY DESIGN: Retrospective chart review was done. RESULTS: In total, 190 children underwent 200 SSLTRs; 29% were reintubated, and 15% required postoperative tracheostomy. Currently, 96% are decannulated. The use of anterior and posterior costal cartilage grafting, age less than 4 years, sedation for more than 48 hours, a leak pressure around the endotracheal tube at greater than 20 cm H2O, and moderate/severe tracheomalacia significantly increased the rate of reintubation. The duration of stenting did not affect outcomes. Children with anterior and posterior grafts and those with moderate or severe tracheomalacia were more likely to need a postoperative tracheostomy. CONCLUSION: SSLTR can be effective for the treatment of pediatric laryngotracheal stenosis. Diligent preoperative assessment of the patient and the patient's airway and close postoperative care are important to the success of this operation.

Cricotracheal resection as a primary procedure for laryngotracheal stenosis in children.

OBJECTIVE: Cricotracheal resection (CTR) is being increasingly used in the treatment of children with severe laryngotracheal stenosis. In this institution the majority of children are treated with CTR as a salvage procedure having undergone previous unsuccessful laryngotracheal reconstruction (LTR). Selected children have undergone CTR as a primary procedure (without previous LTR). The objective of this study is to examine the outcome for children undergoing cricotracheal resection as a primary procedure for severe laryngotracheal stenosis. METHOD: analysis from prospectively collected database. RESULTS: 17 patients underwent CTR without previous LTR or anterior cricoid split between October 1994 and September 1998. All the patients had grade 3 or 4 stenosis. After a minimum of 1 year follow up 15 children are decannulated. Five children required further surgery to achieve this. Two children still have tracheostomies. Both had extended procedures. One included bilateral arytenoid abduction for bilateral vocal cord paralysis in a patient with quadraparesis following transverse myelitis. The other child, who suffered from multiple congenital anomalies, underwent a concurrent posterior cricoid cartilage graft. Nine patients had good voice post-operatively, five had acceptable voice and three had weak or no voice. CONCLUSION: the early experience for CTR in children as a primary procedure achieved an overall decannulation rate of 88% after 1 year follow up in children with severe laryngotracheal stenosis. Five children required further surgery to achieve this. The voice outcome was variable. CTR is an alternative primary procedure to LTR for severe laryngotracheal stenosis in children. The relative indications for these procedures are discussed.