The efficacy of bone-anchored hearing implant surgery in children: A systematic review

Long-Term Outcomes of a Percutaneous Wide-Diameter Bone-Anchored Hearing Implant: A Clinical Evaluation of More than 800 Implants

OBJECTIVE

This study evaluates the clinical outcomes of 807 percutaneous wide-diameter bone-anchored hearing implants (BAHIs) in 701 patients. In addition, it compares patient groups and examines bone conduction device (BCD) usage.

STUDY DESIGN

Retrospective cohort study. Mean follow-up period of 3.8 years.

SETTING

Tertiary referral center.

PATIENTS

All patients implanted with a percutaneous wide-diameter BAHI until December 2020 were included. Patients were divided into age groups, "loading-time" groups, and, if applicable, specific subgroups thought to be at risk for complications postsurgery, e.g., intellectual disability and comorbidities.

MAIN OUTCOME MEASURES

Soft tissue reaction, implant survival, revision surgery, and BCD usage.

RESULTS

In 9.1% of the 5,188 observations of 807 implants, an adverse soft tissue reaction was reported according to the Holgers' scale. Significantly more (adverse) soft tissue reactions were observed in children and intellectually disabled (ID) patients (p < 0.05). Comorbidity subgroups showed no significant differences in soft tissue reactions. Implant loss percentage, including explantations, was 6.2%. Implant survival was significantly worse in patients with ID (14.1%; p = 0.021). Pediatric age, early loading, or comorbidities did not significantly influence implant survival. At least 592 implants (73.4%) were used for bone conduction hearing, of which 65.4% were used daily.

CONCLUSION

Both children and ID patients are more prone to (adverse) soft tissue reactions, ID patients only have a higher risk of implant loss. The rate of implant loss in children seemed to be reduced compared to previous studies and thus more comparable to adults since using wide-diameter implants.

Provision of bone conduction hearing implants in England in adults and children: a review of Hospital Episode Statistics data 2012-2021

OBJECTIVE

Bone conduction hearing implants are a well-established method of hearing rehabilitation in children and adults. This study aimed to review any changes in provision in England.

METHODS

The total number of bone conduction hearing implantations performed was analysed from 2012 to 2021 utilising Hospital Episode Statistics data for England.

RESULTS

The total number of procedures has increased by 58 per cent. One-stage bone conduction hearing implantations in adults accounts for the largest proportion of this increase (93 per cent of the total). The number performed in children has remained stable and accounts for 73 per cent (n = 433) of all two-stage procedures.

CONCLUSION

The data show that bone conduction hearing implant surgery is becoming increasingly popular, particularly in adults. This has correlated with the increase in availability, national recommendations and choice of devices.

Paediatric percutaneous bone anchored hearing aid implant failures: Comparing the experience of a tertiary centre with a systematic review of the literature and meta-analysis

BACKGROUND

Despite the proven audiological benefits of Percutaneous Bone Anchored Hearing Aids (BAHAs) in paediatric patients with conductive or mixed hearing loss, their adoption has been limited due to concerns over implant failure and associated complications. This paper conducts a systematic review and meta-analysis to assess the prevalence of implant failure in paediatric populations, combined with a case series from our tertiary referral centre.

METHODS

A comprehensive literature search identified 562 articles, from which 34 were included in the review, covering 1599 implants in 1285 patients. Our retrospective case series included consecutive patients from our tertiary referral centre who underwent percutaneous BAHA implantation from 2003-2019.

RESULTS

Meta-analysis revealed an overall implant failure rate of 11%, predominantly attributed to traumatic extrusion. Our retrospective case series comprised 104 implantations in 76 patients, with a 4.8% failure rate.

DISCUSSION

Factors contributing to the lower-than-expected failure rates in the case series likely included consistent use of 4 mm fixtures from a single manufacturer and older age at implantation. The study underscores the need for standardised reporting formats in bone conduction implants research, given the systematic review's limitations in study design heterogeneity, especially with the expected rise in the adoption of novel active devices.

Bone-anchored hearing aids: Percutaneous versus transcutaneous attachments - a health economics comparison in paediatric patients

INTRODUCTION

Bone anchored hearing aids (BAHA) are a useful support when conventional hearing aids are not suitable. The two types of attachment of the aid are onto a percutaneous abutment or a transcutaneous magnet. Anecdotally, the abutment requires more care, revision procedures and causes more infections than magnet-based devices.

METHODS

A multicentre, retrospective review was conducted of all patients that underwent a BAHA since our programme began, identified through a prospectively maintained database of patients. Patients' charts were audited for outpatient clinic visits, skin complications and revision surgeries. Developmental delay was also recorded. Patients were censored if the hearing aid was removed, replaced or the patient reached 16 years old. Bilateral or reimplanted patients were recorded as separate implants. Statistical analysis was performed using SAS version 9.4.

RESULTS

150 implants were assessed over 126 patients: 115 transcutaneous and 35 percutaneous. Percutaneous patients had significantly more outpatient clinic attendances (Least square mean 4.19 vs. 1.39 p = 0.00), skin complications (mean 4.82 v 0.11 p = 0.00) and theatre visits (mean 2.8 vs. 1.03 p = 0.00) compared to transcutaneous patients. 77 implants were in patients that had developmental delay; having same made no significant difference to above outcomes.

CONCLUSION

There is a significant difference in healthcare burden between percutaneous and transcutaneous systems in a paediatric population. The increased cost of the percutaneous implant to the healthcare system and inconvenience to the patient is cause to consider a transcutaneous system in the first instance.

An objective bone conduction verification tool using a piezoelectric thin-film force transducer

All hearing aid fittings should be validated with appropriate outcome measurements, whereas there is a lack of well-designed objective verification methods for bone conduction (BC) hearing aids, compared to the real-ear measurement for air conduction hearing aids. This study aims to develop a new objective verification method for BC hearing aids by placing a piezoelectric thin-film force transducer between the BC transducer and the stimulation position. The newly proposed method was compared with the ear canal method and the artificial mastoid method through audibility estimation. The audibility estimation adopted the responses from the transducers that correspond to the individual BC hearing thresholds and three different input levels of pink noise. Twenty hearing-impaired (HI) subjects without prior experience with hearing aids were recruited for this study. The measurement and analysis results showed that the force transducer and ear canal methods almost yielded consistent results, while the artificial mastoid method exhibited significant differences from these two methods. The proposed force transducer method showed a lower noise level and was less affected by the sound field signal when compared with other methods. This indicates that it is promising to utilize a piezoelectric thin-film force transducer as an in-situ objective measurement method of BC stimulation.

Assessment Protocol for Candidates for Bone-Anchored Hearing Devices

Introduction The technology regarding bone-anchored hearing devices has been advancing. Nevertheless, complications are still often reported, which can impair treatment adherence and lead to discontinuation of use. There is a lack of studies conducted in tropical countries, where complications can be even greater, as well as standardized protocols for selection, indication and evaluation.

Objective To characterize implanted patients from a Brazilian public institution and describe the medical and audiological assessment protocols to which they were submitted during the selection process and in the follow-up after surgery.

Method An observational, cross-sectional study evaluating the medical records of patients with hearing loss and ear malformations and describing the care protocol through which they were treated.

Results The medical records of 15 patients were reviewed: 6 received transcutaneous implants, and 9, percutaneous implants; 9 patients reported some type of skin lesion, 2 reported pain on the follow-up visit, and 3 had osseointegration failure. The time between surgery and activation ranged from 2 to 9 months. The median scores on the sentences, Sentences in Noise and Monosyllable tests were 100%, 60% and 80%, respectively.

Conclusion It was possible to characterize the patients who received implants at the institution. The patients performed well in silence and had greater difficulty in noise. Even patients who had complications did not complain about the audibility and sound quality. It is essential to develop a model and to standardize the assessment and follow-up methods aimed at the benefit of users of bone-anchored hearing devices, as well as to enable the technico-scientific development in this field.

9-year follow up on maxillofacial implant-supported framework designed to accommodate childhood growth

This clinical report focuses on the challenges and solutions for a child subjected to craniofacial trauma from a wild hyena biting off his nose and anterior maxilla. Unique considerations in prosthodontics and biomedical engineering were required based on future craniofacial growth and development of the child. The physical requirement of a maximum retentive prosthesis for an active, athletic child required unique engineering designs and executions. The sequence of treatment and prosthesis fabrication are detailed. The patient has been followed for nine years without physiologic complications and only minor prosthodontic complications. This article is protected by copyright. All rights reserved.

Clinical Evaluation of a Novel Laser-Ablated Titanium Implant System for Bone Anchored Hearing Systems in a Pediatric Population and the Relationship of Resonance Frequency Analysis With Implant Survival

OBJECTIVE

To evaluate the clinical outcomes of pediatric patients implanted a novel 4.5 mm wide laser ablated titanium bone anchored implant system and to evaluate the implant stability over the first 12-month period.

STUDY DESIGN

A prospective, single-subject, repeated measure, cohort study. Participants served as their own controls.

SETTING

Community and tertiary referral hospital pediatric assessment center.

PATIENTS

A total of 115 consecutive pediatric patients aged 4 to 15 years were implanted with 176 laser ablated titanium bone anchored implants from January 2016 to January 2019.

MAIN OUTCOME MEASURE

Clinical outcomes, implant failure rates, and post implantation implant stability quotient (ISQ) scores were studied over the first 12-month period. Data were analyzed for statistical significance through mixed effect modeling, with the significance level p = 0.01.

RESULTS

A median 12-month survival of 96.6% was observed. Six implants (3.5%) were lost in total, one of these (0.6%) was lost due to trauma. Adverse skin reactions (Holgers grade 2-4) were observed in 4.4% of all postoperative visits, occurring in 22 individuals (19.1%). Neither the ISQ high (ISQH) nor ISQ low (ISQL) values increased significantly between the stage 1 and 2 surgeries. In contrast, the ISQ results, irrespective of abutment size, demonstrated an increasing trend from 49.1 to 57 over the 12 months review period. A statistically significant change was only demonstrated from the 3 months follow up onwards.

CONCLUSION

The use of 4.5 mm wide laser-ablated titanium bone anchored hearing implants resulted in superior survival rates and excellent clinical outcomes compared with previous implant systems.

Systematic and audiological indication criteria for bone conduction devices and active middle ear implants

Certain patients with conductive or mixed hearing loss can benefit from bone-conduction hearing devices or active middle ear implants. Available devices differ in coupling site, energy transfer from the sound processor to the implant, and the active or passive actuator technology. The audiological benefit of those devices depends on the maximum stable power output and the noise floor of the device, the degree and expected stability of the sensorineural hearing loss and the coupling efficiency with the aim on achieving a minumum of 30-35 dB effective dynamic range. The choice of the device is often a trade-off between the optimal audiological solution with respect to the hearing loss, technical device-related parameters and the expected coupling efficiency, the optimal surgical solution with respect to patho-anatomical aspects, device dimensions and the coupling site, invasiveness or surgical risks, and other patient factors with respect to the patients' wish and expectations, social aspects, device usability and connectivity. This review article lists all currently available implantable and conventional bone-conduction hearing devices and active middle ear implants with respect to technical features like maximum power output, market availability, and the expected effective output dynamic range.

The Bonebridge BCI 602 Active Transcutaneous Bone Conduction Implant in Children: Objective and Subjective Benefits

Background: the Bonebridge hearing implant is an active transcutaneous bone conduction implant suitable for various types of hearing loss. It was first launched in 2012 as the BCI 601, with a newer internal part (BCI 602) released in 2019. With the new size and shape, the BCI 602 can be used in patients previously excluded due to insufficient anatomical conditions, especially in patients with congenital defects of the outer and middle ear. Objectives: the purpose of this study is to evaluate the objective and subjective benefits of the new Bonebridge BCI 602 in children who have hearing impairment due to conductive or mixed hearing loss. Safety and effectiveness of the device was assessed. Methods: the study group included 22 children aged 8–18 years (mean age 14.7 years) who had either conductive or mixed hearing loss. All patients were implanted unilaterally with the new Bonebridge BCI 602 implant. Pure tone audiometry, speech recognition tests (in quiet and noise), and free-field audiometry were performed before and after implantation. Word recognition scores were evaluated using the Demenko and Pruszewicz Polish Monosyllabic Word Test, and speech reception thresholds in noise were assessed using the Polish Sentence Matrix Test. The subjective assessment of benefits was carried outusing the APHAB (Abbreviated Profile of Hearing Aid Benefit) questionnaire. Results: after implantation of the Bonebridge BCI 602 all patients showed a statistically significant improvement in hearing and speech understanding. The mean word recognition score (WRS) changed from 12.1% before implantation to 87.3% after 6 months. Mean speech reception threshold (SRT) before implantation was +4.79 dB SNR and improved to −1.29 dB SNR after 6 months. All patients showed stable postoperative results. The APHAB questionnaire showed that difficulties in hearing decreased after implantation, with a statistically significant improvement in global score. Pre-operative scores (M = 35.7) were significantly worse than post-operative scores at 6 months (M = 25.7). Conclusions: the present study confirms that the Bonebridge BCI 602 is an innovative and effective solution, especially for patients with conductive and mixed hearing loss due to anatomical ear defects. The Bonebridge BCI 602 system provides valuable and stable audiological and surgical benefits. Subjective assessment also confirms the effectiveness of the BCI 602. The BCI 602 offers the same amplification as the BCI601, but with a smaller size. The smaller dimensions make it an effective treatment option for a wider group of patients, especially children with congenital defects of the outer and middle ear.

Molecular Response to Nanopatterned Implants in the Human Jaw Bone

Implant surface modification by nanopatterning is an interesting route for enhancing osseointegration in humans. Herein, the molecular response to an intentional, controlled nanotopography pattern superimposed on screw-shaped titanium implants is investigated in human bone. When clinical implants are installed, additional two mini-implants, one with a machined surface (M) and one with a machined surface superimposed with a hemispherical nanopattern (MN), are installed in the posterior maxilla. In the second-stage surgery, after 6-8 weeks, the mini-implants are retrieved by unscrewing, and the implant-adherent cells are subjected to gene expression analysis using quantitative polymerase chain reaction (qPCR). Compared to those adherent to the machined (M) implants, the cells adherent to the nanopatterned (MN) implants demonstrate significant upregulation (1.8- to 2-fold) of bone-related genes (RUNX2, ALP, and OC). No significant differences are observed in the expression of the analyzed inflammatory and remodeling genes. Correlation analysis reveals that older patient age is associated with increased expression of proinflammatory cytokines (TNF-α and MCP-1) on the machined implants and decreased expression of pro-osteogenic factor (BMP-2) on the nanopatterned implants. Controlled nanotopography, in the form of hemispherical 60 nm protrusions, promotes gene expressions related to early osteogenic differentiation and osteoblastic activity in implant-adherent cells in the human jaw bone.

Clinical evaluation and resonance frequency analysis of laser-ablated titanium bone-anchored hearing implant system in children with Down Syndrome

OBJECTIVES

To evaluate complication rates and resonance frequency analysis (RFA) of the stability of a new laser-ablated titanium Bone Anchored hearing Implant system in children with Down syndrome.

METHODS

A prospective, single-subject, repeat measure, cohort study in which each participant served as their own control. Consecutive paediatric patients 4yrs- 15 years old, with a primary diagnosis of Down syndrome (trisomy 21) were implanted between January 2015-January 2020 with BHX Oticon wide implants. Evaluation of soft tissue reactions, fixture failure rates and post implantation Implant stability Quotient (ISQ) at both fixtures and abutment levels were studied over a 12-month period. Data was analysed for statistical significance through mixed effect modelling with significance set at p = 0.01.

RESULTS

31 consecutive paediatric patients with a diagnosis of Down syndrome were implanted with 43 Ponto BHX Oticon™ implant system. Twelve children had bilateral implants and nineteen were unilateral. Over the 12 month follow up 2 fixtures (4.6%) were lost, and adverse skin reactions (Holgers >2) were recorded in 3.2% of all clinical reviews. Implant level stability quotient showed no statically significant change between first and second stage 71.1-71.7. Abutment level ISQ increased from 46.2 to 56.7 p = 0.0001 at the 12-month review point as compared to that recorded at loading.

CONCLUSION

Implant survival and adverse skin reactions were found to be in keeping with those in published literature and much improved compared to previous implant systems placed at this centre. Although abutment level ISQ showed an increase over the review period no correlation between this and implant loss can be concluded.

Hearing rehabilitation with osseointegrated hearing implant in bilateral congenital external auditory canal atresia

INTRODUCTION AND OBJECTIVES

Congenital atresia of the external auditory canal (EAC) is a congenital defect present in one in every 10,000-20,000 births. It causes conductive hearing loss, with an air-bone gap of 50-60dB. Early amplification is essential in bilateral cases to ensure normal language development. The aim of this study is to present the osseointegrated hearing implant as a treatment for bilateral EAC atresia, reviewing the audiometric results and the rate of complications.

MATERIAL AND METHODS

Retrospective analysis of patients diagnosed with bilateral congenital EAC atresia under follow-up in the pediatric ENT clinic of the ENT and Head and Neck Surgery department of a Portuguese Tertiary Hospital, between 2003 and 2019. We reviewed the medical records and collected information on the assessment of the initial audiometric status. In the cases submitted for implantation with an osseointegrated hearing implant, we analyzed the details of follow-up, including immediate and long-term post-operative complications, as well as the audiometric results.

RESULTS

We present 8 pediatric patients, 6 girls and 2 boys, with a diagnosis of bilateral congenital EAC atresia. The audiometric assessment revealed moderate to severe bilateral conductive hearing loss with a mean speech recognition threshold (SRT) of 51dB. Six patients underwent osseointegrated hearing implantation. All 6 patients showed good audiometric results, with an average SRT of 20dB and closure of the air-bone gap.

CONCLUSIONS

The osseointegrated hearing implant was an effective treatment option in these patients, without significant morbidity or complications. Osseointegrated hearing implantation should be considered first line treatment for children with bilateral congenital EAC atresia, as it presents good functional results and a high level of patient satisfaction.

Cartilage Conduction Hearing and Its Clinical Application

Cartilage conduction (CC) is a form of conduction that allows a relatively loud sound to be audible when a transducer is placed on the aural cartilage. The CC transmission mechanism has gradually been elucidated, allowing for the development of CC hearing aids (CC-HAs), which are clinically available in Japan. However, CC is still not fully understood. This review summarizes previous CC reports to facilitate its understanding. Concerning the transmission mechanism, the sound pressure level in the ear canal was found to increase when the transducer was attached to the aural cartilage, compared to an unattached condition. Further, inserting an earplug and injecting water into the ear canal shifted the CC threshold, indicating the considerable influence of cartilage–air conduction on the transmission. In CC, the aural cartilage resembles the movable plate of a vibration speaker. This unique transduction mechanism is responsible for the CC characteristics. In terms of clinical applications, CC-HAs are a good option for patients with aural atresia, despite inferior signal transmission compared to bone conduction in bony atretic ears. The advantages of CC, namely comfort, stable fixation, esthetics, and non-invasiveness, facilitate its clinical use.

A retrospective evaluation of minimally invasive ponto surgery (MIPS) in two pediatric centers

BACKGROUND

Percutaneous bone anchored hearing systems have been used effectively for over forty years with low rates of complications. Minimally Invasive Ponto Surgery (MIPS) is a surgical technique performed through a puncture hole that has been reported to minimize soft tissue trauma and decrease operative time. Due to it being a relatively new procedure there remains a paucity of pediatric outcomes data.

METHODS

Pediatric patients from two tertiary pediatric otolaryngology centers between 2016 and 2019 who underwent MIPS were included in this study. Charts were retrospectively reviewed for indications for surgery, implant and abutment type, overlying skin thickness, skin-to-skin time, Holgers score at three, six and twelve months, revision surgery and time to abutment fitting.

RESULTS

Fourteen patients, two with bilateral procedures met inclusion criteria (mean age = 8.07 ± 2.87years). The mean overlying skin thickness was 5.13 ± 3.18mm. 9.44% of visits had an adverse skin reactionOne patient required surgery forskin overgrowth. One implant loss (6.3%) was reported, following trauma to the abutment. Mean MIPS skin to skin times were 12.4 ± 2.6 min, markedly different that the Baha^® Attract and Connect which were 56 and 53 min, respectively.

CONCLUSION

This study represents the largest pediatric MIPS cohort to date, and our results are similar to published adult studies.

Hearing rehabilitation with osseointegrated hearing implant in bilateral congenital external auditory canal atresia

INTRODUCTION AND OBJECTIVES

Congenital atresia of the external auditory canal (EAC) is a congenital defect present in one in every 10,000-20,000 births. It causes conductive hearing loss, with an air-bone gap of 50-60dB. Early amplification is essential in bilateral cases to ensure normal language development. The aim of this study is to present the osseointegrated hearing implant as a treatment for bilateral EAC atresia, reviewing the audiometric results and the rate of complications.

MATERIAL AND METHODS

Retrospective analysis of patients diagnosed with bilateral congenital EAC atresia under follow-up in the pediatric ENT clinic of the ENT and Head and Neck Surgery department of a Portuguese Tertiary Hospital, between 2003 and 2019. We reviewed the medical records and collected information on the assessment of the initial audiometric status. In the cases submitted for implantation with an osseointegrated hearing implant, we analyzed the details of follow-up, including immediate and long-term post-operative complications, as well as the audiometric results.

RESULTS

We present 8 pediatric patients, 6 girls and 2 boys, with a diagnosis of bilateral congenital EAC atresia. The audiometric assessment revealed moderate to severe bilateral conductive hearing loss with a mean speech recognition threshold (SRT) of 51dB. Six patients underwent osseointegrated hearing implantation. All 6 patients showed good audiometric results, with an average SRT of 20dB and closure of the air-bone gap.

CONCLUSIONS

The osseointegrated hearing implant was an effective treatment option in these patients, without significant morbidity or complications. Osseointegrated hearing implantation should be considered first line treatment for children with bilateral congenital EAC atresia, as it presents good functional results and a high level of patient satisfaction.

Five year clinical outcomes and evaluation following implantation of the Oticon™ wide bone anchored hearing system in 47 children

OBJECTIVES

The Oticon™ wide implant system was launched in 2009 and used at Birmingham Children's Hospital from 2014. To evaluate clinical outcomes of the Oticon™ wide implant (Oticon Medical), with a focus on skin complication rates and fixture loss over a 5-year period in a tertiary paediatric hospital in the UK.

METHODS

Retrospective 5-year longitudinal case record review of 47 children who were implanted with the Oticon™ wide implant system at Birmingham Children's Hospital (BCH) between January 2014 and January 2016.

RESULTS

47 children (27 M:20F) were implanted with 70 Oticon wide implants 23 bilateral, 27 unilateral. Mean age at the time of implantation was 9y 6 m. The follow up was for a mean of 5.4 years. Significant soft tissue complications requiring treatment was found in 11% (n = 8) of loaded fixtures, abutment tightening on two patients, abutment exchange 6% (n = 4) and a 10% (n = 7) fixture failure.

CONCLUSION

The Oticon™ wide implant system produces favourable results with regards to peri-abutment skin complications, fixture stability and revision surgery rates when compared to similar cohorts of children studied at Birmingham Children's Hospital.

Outcomes of BAHA connect vs BAHA attract in pediatric patients

INTRODUCTION

Two of the most commonly employed bone-anchored hearing implant (BAHI) systems are the BAHA Connect and BAHA Attract. The BAHA Connect uses a skin-penetrating titanium abutment. The BAHA Attract uses an implanted magnet, leaving the overlying skin intact. Limited data is available on the difference in complication rates between the two systems. Our hypothesis was that there would be no difference in complications and audiologic data.

METHODS

Retrospective chart review was performed of patients who had BAHA Connect vs. Attract at our tertiary care pediatric hospital from 2006 to 2018. Pre- and post-operative information, including demographics, related diagnoses, outcomes and complications were compared between the systems using Mann-Whitney U tests and Firth logistic regression for one year post-implant. Audiology data was analyzed with Wilcoxon rank-sum and Wilcoxon matched pairs signed rank tests.

RESULTS

Twenty-four Attract and 18 Connect BAHA surgeries were identified from 37 patients. Eleven Connect patients had the surgery completed in two stages. Connect patients followed up an average of 6.5 years post-implant and 15 months for Attract. A total of 58.8% of patients with Connect surgeries had complications within a year and 82.4% had a complication by their last follow-up. Aside from magnet strength related issues, there were no major complications with Attract surgery at any time point. Patients with Connect surgeries had significantly more skin overgrowths, cultured infections, times on antibiotics, nursing phone calls, and ENT visits within the first year and for all records, p < .05. The pure-tone average was significantly lower for both Connect [unaided-M(SD) = 61.7(9.8); aided-M(SD) = 26.4(5.5) and Attract (unaided-M(SD) = 66.0(22.5); aided-M(SD) = 25.6(6.1)] after implant, p < .001.

CONCLUSION

Implantation of both systems lead to improved hearing outcomes with profoundly different complication rates.