Outcomes in adulthood of gastric transposition for complex and long gap esophageal atresia.

BACKGROUND: Long term outcomes of gastric transposition (GT) for complex esophageal atresia (EA) are poorly reported. We aimed to perform comprehensive long term follow up of adults who had been treated with GT for EA as children. METHODS: Consecutive patients who underwent GT for EA in childhood aged >18 years old were identified alongside age matched patients who had primary repair (PR). Type of EA, comorbidities and details of surgery were recorded. Telephone interviews included medical history, current symptoms - including gastrointestinal symptom rating scale (GSRS), morbidity and health related quality of life (HRQoL) using gastrointestinal quality of life index (GIQLI). RESULTS: 32 participants were interviewed in each group (mean age 29 years). BMI (19.9 ±â€¯3.5) was significantly lower (p = 0.0006) in GT group. 6/32 (19%) still required supplementary feeding. Adult morbidity included anastomotic stricture (34%), chronic respiratory disease (28%), dumping symptoms (25%), anemia (47%) and depression (19%). 3 patients required major revision surgery. Participants in both groups report regular upper gastrointestinal symptoms (GSRS: GT = 2.1, PR = 2.0) and were more symptomatic than the normal population (1.4) but not statistically different from each other. HRQoL (GIQLI = 113) was lower than after PR (122) but not significantly different (p = 0.29) and the normal population (125). 23% of GT participants had higher than normal HRQoL. CONCLUSIONS: GT for EA is associated with significant morbidity and symptoms, including issues previously unreported in adulthood such as mental health problems. This mandates long term follow up and quality transition of these patients into adult care. TYPE OF STUDY: Retrospective study. LEVEL OF EVIDENCE: Level III.

Oesophageal atresia is correctable and survivable in infants less than 1 kg.

INTRODUCTION: Management of oesophageal atresia (OA) and trachea-oesophageal fistula (TOF) in babies of low birth weight is challenging especially when associated with other anomalies. Birth weight of <1500 g has previously formed part of a classification system designed to predict outcome, alongside the cardiac status of the patient. Improvements in neonatal care have led to increasing numbers of premature low birth weight infants surviving. The aim of this study was to look at the experience of our institution in the extremely low birth weight (ELBW) patients. METHODS: A retrospective review of our institutions OA database was performed from 1993 to June 2015. Patients of birth weight less than 1000 g were included. A review of our OA/TOF clinical database and notes review established the following; gestation, birth weight, associated anomalies, operative procedures, morbidity and mortality. RESULTS: Of 349 patients with OA across the 22-year period, 9 ELBW patients were identified (<1000 g). Six males and three females. Gestational age ranged from 23 to 34 weeks and median birth weight was 815 g ranging from 630 to 950 g. Overall survival was 56 % (5/9). There were double the numbers of ELBW OA/TOF patients seen in the second half of the study period presumably the result of improving neonatal care. Seven patients had type C OA with TOF and underwent emergency TOF ligation, two had concomitant oesophageal repair. One of these patients died from NEC; the other survived. Of the five who had isolated TOF ligation three died-two from cardiac disease and one from prematurity. Both type A patients survived and after initial gastrostomy placement one had a primary delayed repair, the other a gastric transposition. All three babies under 800 g died-one from cardiac disease the others from conditions indicative of their prematurity-necrotising enterocolitis and intraventricular haemorrhage. CONCLUSIONS: 50 % survival is achievable in OA/TOF under 1 kg and the Spitz classification is still applicable in this group as a whole. However, none of the current classification systems are applicable in infants <800 g who in our study all had poor outcomes. We suggest these should be considered as separate group when predicting outcomes.

The extramucosal interrupted end-to-end intestinal anastomosis in infants and children; a single surgeon 21year experience.

BACKGROUND/PURPOSE: To report outcomes of a standardised technique for intestinal anastomosis in infants and children. METHODS: Data were prospectively collected on all paediatric intestinal anastomosis by a single surgeon over a 21year period. Anastomoses were constructed using an end-to-end extramucosal technique with interrupted polypropylene sutures. Demographic and clinical data were recorded. RESULTS: Six-hundred and thirteen anastomoses were constructed in 550 patients. Median age at time of anastomosis was 6months (range 1day-226months). The most common reason for anastomosis was stoma closure (n=271, 49%). For those patients that required multiple anastomoses the most common pathology was acute NEC (n=22/41, 54%). One-hundred and one (18.4%) patients passed stool within 24hours of surgery, 175 (31.8%) between 24-48 hours and 95 (17.3%) between 48-72 hours. Anastomotic complications occurred in 7 patients (1.3%) including anastomotic leakage (n=5, 0.9%) and anastomotic stricture (n=2, 0.4%). The majority of anastomotic leakages (80%) followed resection of acute NEC. CONCLUSIONS: The interrupted extramucosal anastomosis is safe and effective. The return of bowel function is rapid and the complication rate acceptable. We recommend this technique be used for all intestinal anastomoses in children and infants.

Classification and clinical evaluation.

Conjoined twins represent a great challenge for most pediatric specialists including pediatric surgeons, anesthetists, neonatologists, urologists, neurosurgeons, and orthopedic surgeons. This anomaly can be classified according to the type of twins׳ fusion. Various organs can be fused making the separation difficult. Conjoined twins are usually diagnosed antenatally by ultrasound. Detailed fetal echocardiography is necessary to counsel the parents during pregnancy. Postnatally, the majority of the conjoined twins can be thoroughly investigated using various imaging techniques. This allows careful planning of the operation. However, in approximately one-third of the patients an urgent operation is required at birth without a complete assessment of the joining. This is associated with a poorer outcome.

Planning the operation.

The management of conjoined twins falls into three distinct groups-non-operative, emergency separation and elective separation. Planning meetings involving all the personnel who will be required during the operation are held. The radiological findings are presented and the anaesthetic, nursing and intensive care requirements are highlighted.

Theatre setup.

The theatre staff would have been made aware of the special requirements for the operation at the planning meetings. Two sets of scrubs nurses will be required but only one set will be needed for the actual separation. The second set of scrub nurses will be needed only when both twins have survived the separation and the second twin is moved to another operating room for closure of the wound.

The separation procedure.

The various stages of the separation are carefully planned but despite this, variations which will change the schedule of the procedure may exist. In general the operation commences on the opposite side from the main procedure and then the twins are turned for the remainder of the operation. Each type of conjoined twin is different but basically thoracopagus involves the hearts, omphalopagus involves the liver and small intestine and ischiopagus involves the large intestine and genito-urinary system. Our results are presented together with interesting cases from which lessons have been learned.

Comparison of minimally invasive and open gastric transposition in children.

BACKGROUND: Gastric transposition is an established method of esophageal replacement in children, and the use of minimally invasive techniques avoids the trauma of open access. The objective of this study was to compare outcomes of minimally invasive versus open gastric transposition in children. MATERIALS AND METHODS: All cases of attempted laparoscopic-assisted gastric transposition at Great Ormond Street Hospital (GOSH), London, United Kingdom, between 2003 and 2012 were retrospectively reviewed. A comprehensive literature search was completed on MEDLINE for minimally invasive gastric transposition in children, and postoperative outcomes were collated. The outcomes from the retrospective review (single-center, GOSH) and the literature search (multicenter) were compared with those of the largest study on open gastric transposition consisting of 192 cases performed at GOSH. RESULTS: In this retrospective review of 19 patients (mean age, 3.5 years; range, 0.4-15 years), the indications were long-gap esophageal atresia, postoperative, caustic, and idiopathic esophageal stricture, and esophageal dysmotility. Three cases were converted to laparotomy and excluded from subsequent analysis. There were one anastomotic leak, two strictures, and no deaths in this series. The literature search yielded a further 50 cases for comparison. Single-center (n=16) and multicenter (n=66) comparison of minimally invasive versus open technique (n=192) showed no difference in leak (6.3% and 16.7%, respectively, versus 12.0%; P=.701 and P=.398), stricture (12.5% and 15.2% versus 20.8%; P=.535 and P=.370), and mortality rates (0% and 1.5% versus 4.7%; P=1.000 and P=.461). CONCLUSION: Minimally invasive gastric transposition is a safe and acceptable alternative to open surgery in children.

The outcome of critically ill neonates undergoing laparotomy for necrotising enterocolitis in the neonatal intensive care unit: a 10-year review.

PURPOSE: To evaluate outcomes in critically ill neonates with necrotising enterocolitis (NEC) undergoing a laparotomy in the neonatal intensive care unit (NICU). METHODS: This is a retrospective review of neonates diagnosed with NEC who underwent a laparotomy on NICU between 2001 and 2011. Demographic, diagnostic, operative and outcome data were analysed. Nonparametric comparison was used. Data are reported as median (range). RESULTS: 221 infants with NEC were referred for surgical evaluation; 182 (82%) underwent surgery; 15 (8%) required a laparotomy on NICU. Five had NEC totalis, 4 multifocal disease and 6 focal disease. Five had an open and close laparotomy, 8 stoma with/without bowel resection and 2 bowel resection and primary anastomosis. Ten (67%) died at a median of 6.5-hours (2-72) postoperatively; 2 died at 72 and 264-days. The 30-day mortality rate was higher (p=0.01) among infants undergoing a laparotomy on NICU (10/15; 67%) than in theatre (54/167; 32%). There was no significant difference in mean Paediatric Index of Mortality 2 Scores between survivors and nonsurvivors (p=0.55). Three (20%) infants remain alive with no or minimal disability at 1.4 (0.5-7.5) years. CONCLUSION: Laparotomy for NEC on NICU is a treatment option for neonates who are too unstable to transfer to theatre. However, with 67% dying within 6.5-hours and a further 13% after months in hospital, we must consider whether surgery is always in their best interests. Development of a prediction model to help distinguish those at highest risk of long-term morbidity and mortality could help with decision making in this difficult situation.

Four year follow-up of a randomised controlled trial comparing open and laparoscopic Nissen fundoplication in children.

OBJECTIVE: To evaluate the 4-year results following a randomised controlled trial (RCT) comparing open (ONF) and laparoscopic (LNF) Nissen fundoplication in children. BACKGROUND: It is assumed that long-term results of ONF and LNF are comparable. No randomised studies have been performed in children. METHODS: A follow-up study was performed in children randomised to ONF or LNF (clinicaltrials.gov identifier NCT00259961). Recurrent gastro-oesophageal reflux (GER) was documented by upper gastrointestinal contrast study and/or 24-h pH study. Nutritional status, retching and other symptoms were investigated. A questionnaire was used to assess the quality of life before and after surgery. RESULTS: Thirty-nine children were randomised to ONF (n=20) or LNF (n=19). There were 15 ONF and 16 LNF neurologically impaired children. One patient (ONF group) was lost to follow-up. Follow-up was 4.1 years (3.1-5.3) for ONF group and 4.1 years (2.6-5.1) for LNF group (p=0.9). Seven neurologically impaired children had died by the time of follow-up (3 ONF, 4 LNF). Incidence of recurrent GER was 12.5% in the ONF and 20% in the LNF (p=ns). One patient in each group underwent redo-Nissen fundoplication. Nutritional status improved in both groups, as indicated by a significant increase in weight Z-score (p<0.01). Gas bloat and dumping syndrome were present in both groups (p=ns). Incidence of retching was lower in the laparoscopic group (p=0.01). Quality of life improved in both groups (p=ns). CONCLUSIONS: Open and laparoscopic Nissen provide similar control of reflux and quality of life at follow-up. LNF is associated with reduced incidence of retching persisting at 4-year follow-up. TRIAL REGISTRATION NUMBER: NCT00259961.

Paediatric laparoscopic Heller's cardiomyotomy: a single centre series.

BACKGROUND: The optimal management of oesophageal achalasia remains unclear in the paediatric population due to the rarity of the disease. This study reviews the institutional experience of the laparoscopic Heller's cardiomyotomy (HC) procedure and attempts to define the most appropriate treatment. METHODS: A retrospective review of children undergoing HC at a single institution was performed. Demographics, pre-operative investigations, and interventions were reviewed. Post-operative outcomes and follow up were evaluated. Data is expressed as median (range). RESULTS: Twenty-eight children were included (13 male, 15 female) whose median age was 13 (3.2-17.4) years. Nine children underwent a pre-operative oesophageal balloon dilatation (OBD) a median of 1(1-6) times. Others included botulinum toxin injection (n=1) and Nifedipine (n=1). All had a pre-operative upper gastrointestinal contrast series, and twenty-five had upper gastrointestinal endoscopy and manometry. All had laparoscopic HC with no conversions, and ten had a concomitant fundoplication. Post-operative intervention occurred in eight (28%) incorporating OBD (n=7), of whom four required a redo HC. One patient underwent a redo without intervening OBD. Follow-up was for a median of 0.83 (0-5) years with fourteen children discharged from surgical follow-up. Twenty-seven have thus far had a good outcome. CONCLUSION: This study comprises the largest series of paediatric laparoscopic HC reported to date. It is effective with or without a fundoplication and is the best long term treatment modality available. OBD for persisting symptoms following HC may obviate the need for redo myotomy.

Fluoroscopic balloon dilation of esophageal atresia anastomotic strictures in children and young adults: single-center study of 103 consecutive patients from 1999 to 2011.

PURPOSE: To determine whether fluoroscopic balloon dilation (FBD) is a safe and effective method of treating esophageal anastomotic stricture after surgical repair in an unselected patient population. MATERIALS AND METHODS: With ethics committee approval, records for 103 consecutive patients who underwent FBD with our interventional radiology service (1999-2011) were reviewed retrospectively. Patients underwent diagnostic contrast material-enhanced study prior to the first dilation. Dilations were performed by using general anesthesia. Outcomes were number and/or frequency of dilations, clinical effectiveness and response to dilations, esophageal perforation, requirement for surgery, and mortality. Data were expressed as mean ± standard deviation (with range). Comparisons were conducted by using the Fisher exact test and log-rank test. The significance level was set at P < .05. RESULTS: One hundred three patients (61 male patients, 59%) underwent 378 FBD sessions (median, two dilations per patient; range, 1-40 dilations). The median age at first FBD was 2.2 years (range, 0.1-19.5 years). The balloon catheter diameters ranged from 4 to 20 mm. FBD was successful in 93 patients (90%): 44 (47%) after single dilation and 49 (53%) after multiple dilations. There was no difference in the proportion of patients who required one dilation and were younger than 1 year versus those who were 1 year of age and older (P > .99; odds ratio, 1.07 [range, 0.43-2.66]). Ten patients (10%) required further procedures: Three underwent stent placement, three underwent esophageal stricture resection, and four underwent esophageal reconstruction. Four esophageal perforations (1%) developed after FBD. Antireflux surgery was performed in 18 patients (17%). There were no deaths. CONCLUSION: FBD for anastomotic strictures after esophageal atresia repair is feasible and acceptably safe and provides relief of symptoms in most patients (90%); however, about half require more than one dilation, and surgery is best predicted if more than 10 dilations are required.

A standardised investigative strategy prior to revisional oesophageal surgery in children: High incidence of unexpected findings.

BACKGROUND/PURPOSE: Revisional oesophageal reconstructive surgery carries uncommon and unusual risks related to previous surgery. To provide maximum anatomical detail and facilitate successful outcome, we report a standardised pre-operative investigative strategy for all such patients. METHODS: Prospective 8-month cohort study following the introduction of this strategy. All patients underwent high resolution thoracic contrast CT scan and micro-laryngo-bronchoscopy by a paediatric ENT surgeon in addition to upper gastrointestinal contrast study, oesophagoscopy, and echocardiogram. RESULTS: Seven children (median age 5.6 months [range 2.2-60]) completed the pathway. Four were referred with recurrence of a previously divided tracheo-oesophageal fistula (3 congenital, 1 acquired) and 3 (all with oesophagostomy) for oesophageal replacement for congenital isolated oesophageal atresia (OA, n=1) and failed repair of OA with distal TOF with wide gap (n=2). Overall, unanticipated findings were demonstrated in 6/7 children and comprised severe tracheomalacia and right main bronchus stenosis requiring aortopexy (n=1), vocal cord palsy (n=2), extensive mediastinal rotation (n=1), proximal tracheal diverticulum (n=1), severe subglottic stenosis requiring airway reconstruction (n=1), proximal tracheal diverticulum (n=1), right sided aortic arch (n=1) and left sided aortic arch (previously reported to be right sided, n=1). CONCLUSIONS: This standardised approach for this complex group of patients reveals a high incidence of unexpected anatomical and functional anomalies with significant surgical and possible medico-legal implications. We recommend these investigations during the pre-operative work-up prior to all revisional oesophageal surgery.

Hypercapnia and acidosis during open and thoracoscopic repair of congenital diaphragmatic hernia and esophageal atresia: results of a pilot randomized controlled trial.

OBJECTIVE: We aimed to evaluate the effect of thoracoscopy in neonates on intraoperative arterial blood gases, compared with open surgery. BACKGROUND: Congenital diaphragmatic hernia (CDH) and esophageal atresia with tracheoesophageal fistula (EA/TEF) can be repaired thoracoscopically, but this may cause hypercapnia and acidosis, which are potentially harmful. METHODS: This was a pilot randomized controlled trial. The target number of 20 neonates (weight > 1.6 kg) were randomized to either open (5 CDH, 5 EA/TEF) or thoracoscopic (5 CDH, 5 EA/TEF) repair. Arterial blood gases were measured every 30 minutes intraoperatively, and compared by multilevel modeling, presented as mean and difference (95% confidence interval) from these predictions. RESULTS: Overall, the intraoperative PaCO2 was 61 mm Hg in open and 83 mm Hg [difference 22 mm Hg (2 to 42); P = 0.036] in thoracoscopy and the pH was 7.24 in open and 7.13 [difference -0.11 (-0.20 to -0.01); P = 0.025] in thoracoscopy. The duration of hypercapnia and acidosis was longer in thoracoscopy compared with that in open. For patients with CDH, thoracoscopy was associated with a significant increase in intraoperative hypercapnia [open 68 mm Hg; thoracoscopy 96 mm Hg; difference 28 mm Hg (8 to 48); P = 0.008] and severe acidosis [open 7.21; thoracoscopy 7.08; difference -0.13 (-0.24 to -0.02); P = 0.018]. No significant difference in PaCO2, pH, or PaO2 was observed in patients undergoing thoracoscopic repair of EA/TEF. CONCLUSIONS: This pilot randomized controlled trial shows that thoracoscopic repair of CDH is associated with prolonged and severe intraoperative hypercapnia and acidosis, compared with open surgery. These findings do not support the use of thoracoscopy with CO2 insufflation and conventional ventilation for the repair of CDH, calling into question the safety of this practice. The effect of thoracoscopy on blood gases during repair of EA/TEF in neonates requires further evaluation. (ClinicalTrials.gov Identifier: NCT01467245).

Management of a complication of percutaneous gastrostomy in children.

AIM: "Buried bumper" is a complication of percutaneous gastrostomy related to the internal flange getting buried into the wall of the stomach. The aim of this study is to evaluate the management of this complication. METHODS: The surgical and interventional radiology database in our hospital from August 1999 to May 2011 was analyzed. There were 2,007 patients who underwent percutaneous gastrostomy insertion. Notes for patients with buried bumper were reviewed. A telephonic interview with the parents of these children was performed with focused assessment of the care of the gastrostomy tube before the episode of buried bumper. Continuous data are reported as median (range). RESULTS: Twenty children developed buried bumper after gastrostomy insertion. They had a primary diagnosis of neurological (n = 14), metabolic (n = 3), or endocrine (n = 3) disorders. The age at presentation was 5.7 years (2 to 18 years); 2.5 years (1 month to 5 years) after gastrostomy insertion. Ten children (50%) presented with symptoms related to buried bumper which included leakage around the gastrostomy (n = 4), pus, discharge or bleeding from the site (n = 5), stiffness on feeding (n = 3), and unable to push the flange (n = 1) (three children had more than one symptom). Ten children (50%) were asymptomatic and underwent routine change or removal of gastrostomy. In nine children, there was an attempt to remove the flange by interventional radiology but this was successful only in one. In the remaining 19 children, 4 had endoscopic removal while 15 children developed an inflammatory mass and required a laparotomy (n = 12) or laparoscopic-assisted excision (n = 3). CONCLUSION: Buried bumper is a rare complication of percutaneous gastrostomy. Inadequate postoperative care without appropriate mobilization is a factor leading to this preventable complication. Endoscopic removal is possible, failing which laparoscopic surgery should be considered.

Recurrence rate of Morgagni diaphragmatic hernia following laparoscopic repair.

PURPOSE: Morgagni diaphragmatic hernia can be repaired laparoscopically. The aim of this study is to evaluate the outcome of this minimally invasive approach. METHODS: A retrospective review was conducted on all consecutive children who underwent repair of Morgagni hernia from January 2002 to December 2011 in our hospital. Data are expressed as median (range). RESULTS: There were 12 children with Morgagni hernia. Age at surgery was 7.5 months (2-125). Associated malformations were present in 7 children (58 %). All children underwent initial laparoscopic approach. Two children (16 %) underwent conversion to open surgery. The hernia was closed primarily in 11 children (92 %), using a polyester patch in 1 (8 %). There were no intraoperative or immediate postoperative complications. Five children (42 %), all repaired initially without a patch, had a recurrence of the Morgagni hernia. The repair of the recurrent hernia was performed laparoscopically in four out of the five children, and a patch was used in two patients with no further recurrences or complications. CONCLUSIONS: There is a high rate of recurrence after laparoscopic Morgagni hernia repair. This is exclusively associated with laparoscopic repair without patch, and it is in contrast with the low recurrence rate reported previously. More frequent use of patch may be beneficial.

Outcomes following laparoscopic inguinal hernia repair in infants compared with older children.

PURPOSE: Indications for laparoscopic inguinal hernia repair in infants and children remain controversial. The purpose of this study is to compare clinical features and outcome of laparoscopic inguinal hernia repair in infants with older children. METHODS: Retrospective single centre review of all patients <16 years of age (n = 380) undergoing laparoscopic inguinal hernia repair over a 5-year period (Jan 2005-Dec 2009). Outcomes were compared between infants (≤ 12 months of age) with older children (1-15 years). RESULTS: There was a trend towards higher recurrence rate in older children than in infants (4 % vs. 1 %; p = 0.17). Total complications and complications requiring surgery were similar in both age groups. There was one testicular atrophy in an infant who had an incarcerated inguinal hernia. The incidence of bilateral inguinal hernia and contralateral patent processus vaginalis (PPV) were both significantly higher in infants (total 61 % compared with 35 % in older children). CONCLUSIONS: Laparoscopic inguinal hernia repair in infants is safe and carries acceptable complication and recurrence rates. The laparoscopic approach may be particularly beneficial in infants since it allows simultaneous closure of a contralateral PPV and bilateral herniae. The outcome of laparoscopic inguinal hernia repair in older children requires further evaluation.

Clot dissolution: a novel treatment of midgut volvulus.

Midgut volvulus due to malrotation may result in loss of the small bowel. Until now, after derotation of the volvulus, pediatric surgeons do not deal with the mesenteric thrombosis, which causes continuing ischemia of the intestine. On occasion, a "second look" laparotomy is performed in the hope that some improvement in blood supply to the intestine has occurred. We describe a new combined treatment to restore intestinal perfusion based on digital massage of the superior mesenteric vessels after derotation and systemic infusion of tissue-type plasminogen activator. This new therapy has been successful in 2 neonates with severe intestinal ischemia due to volvulus.

Cost-effectiveness of laparoscopic versus open pyloromyotomy.

BACKGROUND: Infantile hypertrophic pyloric stenosis can be corrected by either open (OP) or laparoscopic pyloromyotomy (LP). LP may provide clinical benefits of reduced time to postoperative full feeds and reduced postoperative inpatient stay, but the cost effectiveness is not known. Our aim was to compare the cost effectiveness of laparoscopic and open pyloromyotomy. METHODS: OP and LP were compared in a multicenter randomized double-blind controlled trial, for which the primary outcomes were time to full feeds and time to discharge. In order to undertake a detailed cost analysis, we assigned costs, calculated on an individual patient basis, to laboratory costs, imaging, medical staff, medication, ward, operative, and outpatient appointments for 74 patients recruited from one of the participating centers. Data (mean ± SEM) were compared using linear regression analysis, adjusting for the minimization criteria used in the trial. RESULTS: Operation costs were similar between the two groups ($3,276 ± $244 LP versus $3,535 ± $152 OP). A shorter time to full feeds and shorter hospital stay in LP versus OP patients resulted in a highly significant difference in ward costs ($2,650 ± $126 LP versus $3,398 ± $126 OP; P = .001) and a small difference in other costs. Overall, LP patients were $1,263 (95% confidence interval $395-$2,130; P = .005) less expensive to treat than OP patients. Sensitivity analyses of laparoscopic hardware usage and of incomplete pyloromyotomy indicated that LP was consistently less expensive than OP. CONCLUSIONS: LP is a cost-effective alternative to OP as it delivers improved clinical outcome at a lower price.