One-stage (Warsaw) and two-stage (Oslo) repair of unilateral cleft lip and palate: Craniofacial outcomes

Facial growth in patients with unilateral cleft lip and palate at 19 years of age after three different one-stage palatal repairs: a longitudinal study with prediction from cephalograms at 5 years of age

OBJECTIVES

To compare cephalometric long-term outcomes in patients with unilateral cleft lip and palate (UCLP) and treated with three different surgical protocols for palatal repair. Furthermore, to investigate growth longitudinally and evaluate the possibility to predict the outcome at age 19 from cephalometric values at 5 years.

MATERIALS/METHODS

Lateral cephalograms of 68 patients, operated according to the Veau-Wardill-Kilner technique (n = 13), the minimal incision technique (n = 39), or MIT with muscle reconstruction (MITmr) (n = 16) were assessed. At a mean age of 19.0 (SD 0.7) years, 17 skeletal and 6 soft tissue variables were analysed using analysis of variance (ANOVA) with pairwise comparison. Lateral cephalograms at a mean age of 5.1 (SD 0.4) years, from 32 of the 68 patients were used to predict values at 19 years, using a multiple linear regression.

RESULTS

There were statistically significant differences between the three surgical techniques for eight of the skeletal variables and for two of the soft-tissue variables at 19 years. The angle between the sella/nasion plane and the nasion/A plane (SNA) was 74.5 (SD 3.8) after Veau-Wardill-Kilner (VWK), 77.6 (SD 5.3) after minimal incision technique (MIT), and 76.7 (SD 2.6) after MITmr. Adjusted for baseline values, at 5 years, only face height had a significant effect dependent on surgical technique.

LIMITATIONS

Due to the exclusion criteria or missing medical records, only 43% of 157 consecutive patients could be included in the study.

CONCLUSION

MIT and MITmr resulted in better cephalometric results regarding facial growth sagittally and vertically compared to VWK. Most of the cephalometric variables measured showed a strong positive relation between the value at 5 and the value at 19 years of age.

Medial incision approach in modified small double-opposing Z-plasty for Veau II cleft repair

An encouraging outcome was described for the use of modified Furlow small double-opposing Z-plasty (sDOZ) using the medial incision (MIsDOZ) approach in repair of Veau type I cleft palate. This retrospective study assessed early results of using extended indication criterion of MIsDOZ for the management of consecutive non-syndromic patients with Veau II cleft palate treated by a single surgeon. Bardach two-flap plus sDOZ (two-flap approach) or medial incision approach with a tension-driven stepwise application of lateral palatal incisions (soft palate only, von Langenbeck type, or two-flap type) were applied. Surgical (age, cleft width, operative time, hospital stay, and complication)- and auditory-perceptual assessment-related data were collected. Two-flap approach (n = 21) demonstrated a significantly (p < 0.001) increased operative time (132.8 ± 12.2 versus 114.8 ± 19.9 min, respectively) and higher use of lateral incisions (100% versus 44.4%) than medial incision approach (n = 27), with no significant (p > 0.05) difference for age at surgery (13.0 ± 6.1 versus 13.6 ± 5.8 months), cleft width (8.5 ± 4.1 versus 8.7 ± 3.8 mm), hospital stay (1.0 ± 0 versus 1.0 ± 0 day), and complication (0% versus 0%) and hypernasality (9.5% versus 7.4%) rates. In conclusion, the medial incision approach for Veau II cleft repair resulted in reduced need for lateral palatal incision with no increase of complication or hypernasality rates.

Comparison of two surgical protocols for the treatment of unilateral cleft lip and palate: a multidisciplinary systematic review and meta-analysis

There is still no unanimous agreement on the optimal surgical protocol(s) for the treatment of unilateral cleft lip and palate (UCLP), and a huge variety of protocols are employed by cleft centres across the world. The aim of this systematic review and meta-analysis was to compare reported patient outcomes of the Oslo protocol (and modifications) (OP) and delayed hard palate closure protocols (DHPCP) from a multidisciplinary perspective. A systematic search of multiple databases was conducted until September 2023. Studies reporting any patient outcomes of these protocols were included. Random-effects meta-analyses were performed for evidence synthesis, including comparisons of results between the types of protocol. The quality of evidence was evaluated using the ROBINS-I tool. In total, 62 articles (42 studies) reporting patients with UCLP were reviewed, involving 1281 patients following the OP and 655 following DHPCP. Equally poor long-term sagittal maxillofacial growth was found, and similar results for velopharyngeal insufficiency and nasolabial appearance. In contrast, OP was associated with a lower rate of oronasal fistulas. Disregarding the scarcity of comparable evidence for some domains, the results of this review, overall, favour OP over DHPCP. However, caution should be taken when interpreting the results on velopharyngeal insufficiency and oronasal fistulas, since the possibility of confounding and other biases remains.

25-year Follow-up of Primary Tibial Periosteal Graft for Hard Palate Repair in Cleft Lip and Palate: Outcomes, Concerns and Controversies

OBJECTIVE

This study evaluates long-term outcomes in adults with Unilateral and Bilateral Cleft Lip and Palate (UCLP/BCLP) treated during the period 1992 to 1995 with tibial periosteal graft in primary repair.

DESIGN

Retrospective study.

SETTING

Department of Plastic and Maxillofacial Surgery, Children's Hospital Bambino Gesù (Italy).

PATIENTS

The study included 52 patients with non-syndromic BCLP/UCLP who met the inclusion criteria.

INTERVENTIONS

All patients underwent a standardized surgical protocol using a tibial periosteal graft as primary repair of the hard palate.

MAIN OUTCOME MEASURE(S)

Long-term outcomes on maxillary growth, residual oronasal fistula, and leg length discrepancy.

RESULTS

About <2% of patients showed oral-nasal communication. Mean value of maxillary depth was 86° ± 4.5°. The lower value for maxillary retrusion was 76.8° in relation to the Frankfurt plane. At the x-ray control, 12.2% of patients showed leg discrepancy with a difference of always <2 cm.

CONCLUSIONS

The rate of maxillary retrusion obtained was the same if compared to other techniques. Tibial periosteal graft reduces the risk of fistula and the need for reintervention after secondary bone graft. The study did not observe negative impacts on leg growth after 25 years.

Maxillary Development and Dental Arch Relationships Following Early Two-Stage Palatoplasty: A Comparative Study

OBJECTIVE

To examine skeletal morphology and dental arch relationships at 8 years of age following early 2-stage palatoplasty, which consists of soft palate plasty at 1 year of age and hard palate closure at 1.5 years of age, and to compare the results with those of conventional pushback palatoplasty.

DESIGN

Retrospective.

SETTING

Single institutional study.

PATIENTS

Eighty-six patients with nonsyndromic complete unilateral cleft lip and palate (UCLP) were selected.

INTERVENTION

The subjects were divided into 2 groups according to the palatoplasty protocols, as follows: 45 patients, who underwent early 2-stage palatoplasty (ETS group), and 41 patients, who underwent 1-stage pushback palatoplasty (PB group).

MAIN OUTCOME MEASURES

Skeletal morphology was assessed using lateral cephalometric analysis, and dental arch relationships were examined using the GOSLON yardstick.

RESULTS

Cephalometric analysis revealed that the anterior-posterior length of the maxilla, measured by PTM-A and PTM-ANS, both projected to the nasal floor (NF) plane, was longer in the ETS group than in the PB group (PTM-A/NF, p = .04; PTM-ANS/NF, p = .03, unpaired t-test), although no significant difference was observed in SNA (p = .09, unpaired t-test). Upper posterior facial height was shorter in the ETS group than in the PB group (p = .02, unpaired t). Assessments with the GOSLON yardstick showed that the ETS group presented better dental arch relationships than the PB group (p = 0.04, Mann-Whitney's U-test).

CONCLUSIONS

The present results suggested that the ETS protocol reduced the negative effects of palatal surgery on facial development and dental arch relationships in patients with complete UCLP at 8 years of age.

Midface Growth Potential in Unoperated Clefts: A Systematic Review and Meta-Analysis

ABSTRACT

Competing hypotheses for the development of midface hypoplasia in patients with cleft lip and palate include both theories of an intrinsic restricted growth potential of the midface and extrinsic surgical disruption of maxillary growth centers and scar growth restriction secondary to palatoplasty. The following meta-analysis aims to better understand the intrinsic growth potential of the midface in a patient with cleft lip and palate unaffected by surgical correction. A systematic review of studies reporting cephalometric measurements in patients with unoperated and operated unilateral cleft lip and palate (UCLP), bilateral cleft lip and palate (BCLP), and isolated cleft palate (ICP) abstracted SNA and ANB angles, age at cephalometric analysis, syndromic diagnosis, and patient demographics. Age and Region-matched controls without cleft palate were used for comparison. SNA angle for unoperated UCLP (84.5 ± 4.0°), BCLP (85.3 ± 2.8°), and ICP (79.2 ± 4.2°) were statistically different than controls (82.4 ± 3.5°), (all P ≤ 0.001). SNA angles for operated UCLP (76.2 ± 4.2°), BCLP (79.8 ± 3.6°), and ICP (79.0 ± 4.3°) groups were statistically smaller than controls (all P ≤ 0.001). SNA angle in unoperated ICP (n = 143) was equivalent to operated ICP patients (79.2 ± 4.2° versus 79.0 ± 4.3° P = 0.78). No unoperated group mean SNA met criteria for midface hypoplasia (SNA < 80). Unoperated UCLP/BLCP exhibit a more robust growth potential of the maxilla, whereas operated patients demonstrate stunted growth compared to normal phenotype. Unoperated ICP demonstrates restricted growth in both operated and unoperated patients. As such, patients with UCLP/BCLP differ from patients with ICP and the factors affecting midface growth may differ.Level of Evidence: IV.

Comparison of recurrence rate and speech outcome between two different techniques for cleft palatal fistula closure: A retrospective cohort study

The aim of this retrospective cohort study was to compare the recurrence rate and speech outcomes between two techniques for palatal fistula closure of cleft palate (CP). Patients with CP who underwent secondary palatal fistula closure using the single hinge-flap method with double-breasted mattress suture (hinge-flap group) and those who were treated with the conventional sliding palatal flap method (sliding-flap group) were retrospectively evaluated for demographic and perioperative variables. Recurrence rate of palatal fistula, perceptual speech outcomes, and nasalance scores were further reviewed in patients who met the inclusion criteria. A total of 31 patients, 21 in the hinge-flap group and 10 in the sliding-flap group, were included in this study. The fistula recurrence rate in the hinge-flap group (0%) was significantly lower than that in the sliding-flap group (30.0%) (P = 0.027). In the speech assessment, hypernasality and nasalance scores decreased post-operatively in both groups and significance was observed in the hinge-flap group (P = 0.013, P < 0.001, respectively). Articulation disorders were significantly improved in the hinge-flap group (P = 0.001). Within the limitations of the study it seems that the single hinge-flap method with double-breasted mattress suture should be preferred whenever appropriate.

Changes in the Transverse Dimension of the Maxillary Arch of 5-Year-Olds Born With UCLP Since the Introduction of Nationwide Guidance

Objective:

To determine whether the transverse dimensions of the maxillary arch of 5-year-old children with unilateral cleft lip and palate (UCLP) have changed following centralization of cleft services in the United Kingdom.

Design:

Retrospective cross-sectional study.

Setting:

Digital analysis of UCLP maxillary dental casts.

Participants:

All available maxillary dental casts from 5-year-old participants of the Clinical Standards Advisory Group (CSAG, N = 114) and Cleft Care UK (CCUK, N = 175) studies.

Interventions:

Quantitative measurements of the intercanine width (ICW), intermolar width (IMW), and the distance from the midline to the greater and lesser side canine (GC/LC) and greater side and lesser side second primary molar (GE/LE). Degree measurements of the greater and lesser arch form angles, arch length, anterior palatal depth (APD), and posterior palatal depth were also measured.

Main outcome:

Differences between the transverse dimensions of the maxillary arch for the CSAG and CCUK cohorts.

Results:

In 5 (ICW, IMW, LC, LE, and APD) of the 11 measurements, there was a statistically significant difference between the CSAG and CCUK cohorts. In all of these, the CCUK values were greater than CSAG.

Conclusions:

There have been small but positive improvements for the transverse maxillary dimensions since centralization of the UK cleft service.

A Meta-Analysis of Palatal Repair Timing

ABSTRACT

Developing midface hypoplasia is common after palatoplasty and has been hypothesized to be influenced by the timing of hard palate repair. This meta-analysis assesses the risk of developing midface hypoplasia based on age at hard palate repair. A Pubmed PRISMA systematic review and meta-analysis was completed for literature focused on palatoplasty and midface hypoplasia published between 1970 and 2019. Cephalometric data were extracted and categorized by age at hard palate repair: <6, 7 to 12, 13 to 18, 19 to 24, and 25 to 83 months. Analysis of these groups and a control were compared using independent T-tests and Spearman correlation coefficients. SNA angles for each group were 77.9 ± 3.1° (<6 months), 77.7 ± 4.2° (7-12 months), 78.7 ± 4.2° (13-18 months), 75.1 ± 4.2° (19-24 months), 75.5 ± 4.8° (25-83 months), and were statistically different than the control group 82.4 ± 3.5° (P < 0.0001). Hard palate repair at 13 to 18 months had a statistically significant greater SNA angle than all other groups except for the repair at <6 months group (P = 0.074). As age at hard palate closure increased beyond 18 months, the SNA decreased, corresponding to a more hypoplastic maxilla (Spearman's correlation coefficient -0.381, P = 0.015). Analysis suggests that younger age at the time of repair is less likely to create in midface hypoplasia in adulthood. Minimizing midface hypoplasia in cleft palate patients by optimizing algorithms of care is a practical way to decrease the burden of disease on patients, families and medical systems. Further studies are needed to evaluate the role of technique on outcomes.Level of Evidence: IV.

Speech and Audiology Outcomes After Single-Stage Versus Early 2-Stage Cleft Palate Repair

PURPOSE

The timing and management of patients with cleft palates have been controversial. Early soft palate closure at the time of cleft lip repair followed by hard palate closure at a second stage has been hypothesized to improve speech and audiology outcomes. This study compares cleft palate patients who have undergone single-stage versus 2-stage cleft palate repairs and the outcomes on speech and hearing.

METHODS

A retrospective chart review identified patients with diagnosis of cleft lip with complete cleft palate who underwent either single or 2-stage repair from 2006 to 2012. Data collected included age at each surgery, necessity of further speech surgery for velopharyngeal insufficiency, frequency of tympanostomy tube placement, presence of hearing loss, and speech assessment data graded per the validated Americleft speech scale.

RESULTS

A total of 84 patients were identified and subdivided into groups of single-stage and 2-stage repair. The mean age at the time of single-stage palate repair was 13.3 months. For the 2-stage group, the mean ages were 4.2 and 11.8 months for the soft palate and hard palate repairs, respectively. Comparing the single-stage versus 2-stage palate repairs, there was no significant difference in all speech parameters including hypernasality, hyponasality, nasal air emission, articulation, expressive language, receptive language, speech intelligibility, and speech acceptability for both unilateral and bilateral cleft lip/palate patients. Two-stage repair was associated with increased number of tympanostomy tube placement compared with single-stage repair (relative risk, 1.74; P = 0.009), and the first set of tubes was performed at a statistically significantly younger age, 4.5 months in the 2-stage repair compared with 16.9 months in the single-stage (P = 0.012) with 87.5% performed with first stage of repair. However, there was no difference in the types, degrees of hearing loss, or the presence of at least mild conductive hearing loss at latest follow-up audiograms between the groups.

CONCLUSIONS

There was no significant benefit with respect to speech or hearing outcomes between single-stage and 2-stage cleft palate repairs. This advocates for surgeon and family preference in the timing of cleft palate repair.

Cost Utility Analysis of Staged Versus Single-Stage Cleft Lip and Palate Repair

PURPOSE

As one of the most common congenital craniofacial deformities, cleft lip and palate repair is a complex and much published topic. Proper treatment can require a multitude of appointments and operations and can place a significant burden on both the patients' families and the health care system itself. One proposed solution has been to combine multiple cleft procedures. However, these more complex operations have drawn concerns from institutions and providers regarding increased cost. This study provides a cost utility analysis between single-stage and staged unilateral cleft lip and palate repairs.

METHODS

A retrospective review was conducted via current procedural terminology code identification of all cleft-related operations performed between 2013 and 2018. Patients were screened according to diagnosis, and only analysis on unilateral cleft lip and palate patients was performed. Patients were split into 2 cohorts: those that underwent a single-stage complete cleft repair, which includes palate, lip, alveolus, and nasal repair-termed "PLAN" at our institution, and those that underwent more traditional staged lip and palate repairs. Demographic and billing data were collected for any procedure performed between patient ages 0 and 24 months. χ, t-tests, and parametric regression analyses were performed to compare the cohorts.

RESULTS

Between 2013 and 2018, 968 (n = 968) cleft-related operations were conducted at Loma Linda University Children's Hospital. Seven hundred ninety-six (n = 796) noncleft lip/palate repairs and 38 (n = 38) bilateral cleft lip repairs were excluded. Of the remaining 135 (n = 135) patients with unilateral cleft lip and palate, detailed cost data were available for 86 single-stage and 28 staged repairs. The average combined total cost for single-stage repairs was US $80,405 compared with US $109,473 for staged repairs (P < 0.001). The average total intraoperative cost for single-stage repairs was US $60,683 versus US $79,739 for staged repairs (P < 0.001), and the average total postoperative cost for single-stage repairs versus staged repairs was US $19,776 and US $29,703, respectively (P < 0.001).

CONCLUSIONS

This analysis suggests that single-stage PLAN repair, provides an effective, cost-efficient solution to unilateral cleft lip and palate care, reducing burden on patients' families and the health care system at large.

Growth and Development of Craniofacial Structures in Patients at Different Ages With Unrepaired Submucous Cleft Palate

PURPOSE

Submucous cleft palate (SMCP) is a particular subtype of cleft palate deformity; research related to the craniofacial features of patients with SMCP is comparatively rare. The study objective was to perform a cephalometric comparison of the craniofacial features of patients with SMCP and non-cleft controls at different ages.

MATERIALS AND METHODS

The sample in this cross-sectional study was composed of 2 groups: SMCP patients and non-cleft controls. The primary predictor variables were study group (cleft and non-cleft) and age. Age was divided into 3 groups. The outcome variables of interest were craniofacial measurements. The measurements used reflect cranial length, cranial angle, maxillary sagittal length and protrusion, maxillary vertical height, pharyngeal depth, facial height, mandibular length and protrusion, mandibular plane angle, and intermaxillary relation. Adjusted cephalometric craniofacial measurements between the groups were compared in 3 age groups using generalized linear models after being adjusted for age and gender.

RESULTS

The study included 60 SMCP patients and 60 non-cleft controls. SMCP patients and non-cleft controls were divided into 3 subgroups: those aged 5 to 7 years, those aged 9 to 11 years, and those aged 18 to 30 years. Patients with SMCP at age 5 to 7 years showed a shortened cranial base length, maxillary sagittal length and height, and bony pharynx depth. Patients with SMCP at age 9 to 11 years showed a smaller maxillary sagittal length and bony pharynx depth and an inharmonious jaw relationship. Patients with SMCP at age 18 to 30 years showed a smaller maxillary sagittal length and height and an inharmonious jaw relationship.

CONCLUSIONS

SMCP is associated with progressive maxillary retrognathism and reduced profile convexity from childhood to adulthood.

Long-term mid-facial growth of patients with a unilateral complete cleft of lip, alveolus and palate treated by two-stage palatoplasty: cephalometric analysis

OBJECTIVES

The aim of this study is to evaluate long-term facial growth in adults previously treated for an isolated unilateral complete cleft lip, alveolus and palate by two-stage palatoplasty.

MATERIALS AND METHODS

Unilateral cleft lip and palate (UCLP) patients of 17 years and older treated by two-stage palatoplasty were invited for long-term follow-up. During follow-up, lateral cephalograms were obtained (n = 52). Medical history was acquired from their medical files. Outcome was compared to previously published normal values and the Eurocleft study.

RESULTS

Soft and hard palate closure were performed at the age of 8 (SD 5.9) months and 3 (SD 2.2) years, respectively. The mean maxillary and mandibular angle (SNA, SNB) were 74.9° (SD 4.2) and 75.8° (SD 3.8). Maxillary and maxillomandibular relationships (SNA, ANB) were comparable to all Eurocleft Centres, except for Centre D. We observed a significantly steeper upper interincisor angle compared to the Eurocleft Centres.

CONCLUSIONS

This study describes the long-term craniofacial morphology in adults treated for a UCLP with hard palate closure at a mean age of 3 years. The mean maxillary angle SNA and mandibular angle SNPg were comparable to previous studies both applying early and delayed hard palate closure. The observed upper incisor proclination is likely caused by orthodontic overcorrection in response to the unfavourable jaw relationships. No clear growth benefit of this protocol could be demonstrated.

CLINICAL RELEVANCE

The present study shows the long-term craniofacial morphology of UCLP adults after the Utrecht treatment protocol which includes two-stage palate closure.

[Three-dimensional analysis of alveolar changes of complete unilateral cleft lip patients after presurgical nasoalveolar molding treatment]

OBJECTIVE

This study analyzed the alveolar changes of complete unilateral cleft lip (UCCL) patients after pre-surgical nasoalveolar molding (PNAM) treatment using a three-dimensional method.

METHODS

Palate impressions of thirty UCCL patients who underwent PNAM treatment in the Affiliated Stomatology Hospital of Guangxi Medical University were taken pre- and post-PNAM. The plaster impressions were scanned using cone beam computed tomography (CBCT). The DICOM files were exported and 3D models reconstructed in Mimics 15.0. The following parameters were analyzed in SPSS 17.0: cleft alveolar gap width, alveolar arch end width, upper lip frenulum-median plane distance, alveolar shift distance, and length of alveolar section.

RESULTS

After PNAM treatment, the cleft alveolar gap width and upper lip frenulum-median plane distance decreased significantly (P<0.05). No statistically significant change was observed in the alveolar arch end width (P>0.05). Alveolar shift distances for both sides increased significantly (P<0.05), and the shift distance of major alveolar sec-tion had a more significant increase than the minor alveolar section. The lengths of the alveolar section of both sides increased significantly (P<0.05) with the length of the major alveolar section increasing more significantly than the minor alveolar section.

CONCLUSIONS

The impression-CBCT method supply accurate three-dimensional data of the alveolar process. The PNAM treatment can significantly correct alveolar deformity and improve appearance.

Treatment outcome after neonatal cleft lip repair in 5-year-old children with unilateral cleft lip and palate

INTRODUCTION

The aim of this study was to assess speech outcomes and dental arch relationship of 5-year-old Czech patients with unilateral cleft lip and palate (UCLP) who have undergone neonatal cleft lip repair and one-stage palatal closure.

METHODS AND MATERIALS

Twenty-three patients with UCLP, born between 2009 and 2010, were included in the study. Three universal speech parameters (hypernasality, articulation and speech intelligibility) have been devised for speech recordings evaluation. Outcomes of dental arch relationship were evaluated by applying the GOSLON Yardstick and subsequently compared with the GOSLON outcome of other cleft centers.

RESULTS

Moderate hypernasality was present in most cases, the mean value for articulation and speech intelligibility was 2.07 and 1.93, respectively. The Kappa values for inter-examiner agreement for all the three speech outcomes ranged from 0.786 to 0.808. Sixty-three percent of patients were scored GOSLON 1 and 2, 26% GOSLON 3, and 10% GOSLON 4. GOSLON mean score was 2.35. Interrater agreement was very good, represented by kappa value of 0.867.

CONCLUSION

The treatment protocol, involving neonatal cleft lip repair and one-stage palatal repair performed up to the first year of UCLP patient's life, has shown good speech outcomes and produced very good treatment results in regard to maxillary growth, comparable with other cleft centers.

The Slav-cleft: A three-center study of the outcome of treatment of cleft lip and palate. Part 1: Craniofacial morphology

Results of a comparison of the outcomes of treatment of cleft lip and palate can be affected by growth characteristics of populations from which subjects with the clefts are derived. Moreover, conventional cephalometric techniques used in cleft studies for analysis of facial morphology provide only a partial description of shape and are confounded by biases regarding the reference structures. In this retrospective comparison, craniofacial morphology of preadolescent patients with unilateral cleft lip and palate treated in Warsaw (n = 35, age = 10.6 years, SD = 1.2), Prague (n = 38, age = 11.6 years, SD = 1.4), and Bratislava (n = 26, age = 10.5 years, SD = 1.6) were evaluated on cephalograms with the cephalometric method used in the Eurocleft study and geometric morphometrics. We found that patients treated in Warsaw showed slightly more favorable outcomes than in Prague and Bratislava. The differences were related primarily to the position of maxillary alveolar process, cranial base, mandibular angle, and soft tissues. Although no association between a component of treatment protocol and the outcome was found, it is possible that organizational factors such as participation of high-volume, experienced surgeons contributed to these results.