Life expectancy in pediatric patients with cerebral palsy and neuromuscular scoliosis who underwent spinal fusion

Survival of patients with Duchenne muscular dystrophy who underwent spinal deformity correction

AIM

We investigated survival rates after scoliosis correction in individuals with Duchenne muscular dystrophy (DMD) and evaluated factors that can affect them.

METHOD

This was a retrospective cohort study from 2000 to 2022 with a minimum 2-year postoperative follow-up. We reviewed the hospital records/spinal radiographs and analysed data with XLSTAT. Kaplan-Meier and multivariate Cox regression survival analysis was performed.

RESULTS

Forty-three patients had a mean age at surgery of 14 years 5 months. Mean postoperative follow-up was 10 years 10 months. There was no operative or 30-day postoperative mortality in this group. Twenty-four patients died because of cardiorespiratory failure. Median survivorship was 14 years 2 months, with the longest observed survival being 22 years 6 months given the limitation of the length of postoperative follow-up. The degree of preoperative coronal imbalance and pelvic obliquity, as well as intraoperative blood loss, were factors that significantly affected survival. The impact of preoperative sagittal imbalance and extension of the fusion to the sacrum/pelvis trended towards significance. In contrast, age at surgery, preoperative/postoperative scoliosis, thoracic kyphosis, lumbar lordosis, scoliosis and pelvic obliquity flexibility or correction indices, postoperative coronal/sagittal balance, need of preoperative non-invasive ventilation, preoperative feeding disorders, development of surgical complications, and length of hospital and intensive care unit stay were exposure variables that did not affect postsurgical survival in patients with DMD.

INTERPRETATION

Survival of up to two decades or more was possible among young patients with DMD after scoliosis correction. This was affected by factors that related to disease and deformity severity, as well as surgical morbidity.

WHAT THIS PAPER ADDS

There was no operative or 30-day postoperative mortality in this group of patients with Duchenne muscular dystrophy (DMD) undergoing scoliosis correction. Survival probabilities at 5-year, 10-year, 15-year, and 20-year intervals post-surgery were 92%, 80%, 33%, and 12% respectively. Scoliosis surgery achieved good deformity correction and a balanced spine that was maintained at follow-up. Respiratory failure, severe pneumonia, and left ventricular failure were the leading causes of death in the study participants. Preoperative global coronal imbalance, pelvic obliquity, and intraoperative blood loss significantly predicted survival. Factors that affected survival after scoliosis surgery were associated with perioperative morbidity and disease or deformity severity in the DMD group.

Mortality and Causes of Death in Children With Cerebral Palsy With Scoliosis Treated With and Without Surgery

BACKGROUND AND OBJECTIVES

To compare mortality and causes of death in scoliotic children with cerebral palsy (CP) with and without scoliosis surgery.

METHODS

National population-based registries were searched for children with CP and scoliosis with and without surgery for scoliosis and were analyzed for comorbidities, mortality, and causes of death.

RESULTS

Two hundred thirty-six had not been operated and 238 had been operated on for scoliosis during the median follow-up of 17.8 (interquartile range [IQR] 11.7-25.7) and 23.0 (IQR 18.4-28.2) years, respectively. Both groups had similar comorbidities. During the follow-up, mortality was higher in the nonsurgically treated group than in the surgically treated group (n = 38/236, 16% and 8.7 per 1,000 follow-up years vs n = 29/238, 12% and 5.3 per 1,000 follow-up years, p = 0.047). In patients with nonsurgical treatment, the cause of death was respiratory in 76.3% (29/38) and 37.9% (11/29) in patients with surgical treatment of scoliosis (6.6 and 2.0 per 1,000 follow-up years, p = 0.002). Neurologic causes of death were more common in surgically treated patients than in nonsurgically treated patients, 44.8% (13/29) and 15.8% (6/38), respectively (3.0 and 1.1 per 1,000 follow-up years, p = 0.009).

DISCUSSION

Surgical treatment of scoliosis associates to reduced mortality because of respiratory causes in children with CP and scoliosis.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence of the effects of spinal fusion on mortality of children with severe scoliosis due to CP.

Current concepts in the treatment of neuromuscular scoliosis: clinical assessment, treatment options, and surgical outcomes

The development of spinal deformity in children with underlying neurodisability can affect their ability to function and impact on their quality of life, as well as compromise provision of nursing care. Patients with neuromuscular spinal deformity are among the most challenging due to the number and complexity of medical comorbidities that increase the risk for severe intraoperative or postoperative complications. A multidisciplinary approach is mandatory at every stage to ensure that all nonoperative measures have been applied, and that the treatment goals have been clearly defined and agreed with the family. This will involve input from multiple specialities, including allied healthcare professionals, such as physiotherapists and wheelchair services. Surgery should be considered when there is significant impact on the patients’ quality of life, which is usually due to poor sitting balance, back or costo-pelvic pain, respiratory complications, or problems with self-care and feeding. Meticulous preoperative assessment is required, along with careful consideration of the nature of the deformity and the problems that it is causing. Surgery can achieve good curve correction and results in high levels of satisfaction from the patients and their caregivers. Modern modular posterior instrumentation systems allow an effective deformity correction. However, the risks of surgery remain high, and involvement of the family at all stages of decision-making is required in order to balance the risks and anticipated gains of the procedure, and to select those patients who can mostly benefit from spinal correction.

Complication rate after scoliosis surgery in children with cerebral palsy

Scoliosis is an important problem in children with cerebral palsy (CP). However, the choice for a spinal fusion has to be weighed against the risks of major surgery in this vulnerable population. Paediatricians are frequently consulted preoperatively to assess the (respiratory) risk involved, but data on this question specific for CP are rare. Therefore, we investigated the complication rate after scoliosis surgery in children with CP, compared to idiopathic scoliosis (IS), and we searched for risk factors for the most common complications. In a retrospective monocenter study we analyzed the medical records from all children with CP and IS undergoing scoliosis surgery from 2010 until 2014. Duration of hospitalization and postoperative complications were compared within a 6-month follow-up. Univariate and multivariate logistic regression models were used to identify risk factors. The study included 44 patients with CP (mean age 15y0mo) and 78 patients with IS (mean age 14y6mo). Children with CP experience a higher rate of complications : respiratory and cardiovascular, as well as wound infections and decubitus ulcers (p<0.05). Postoperative pneumonia was the most frequent complication in both patient groups (43% and 18% in CP and IS respectively), with epilepsy being a significant risk factor (OR 3.85, p= 0.037) in children with CP. Intensive care unit and total hospital stay were longer in the CP group (p<0.001). These results may add information on perioperative care and surgical decision making.

Complications in growth-friendly spinal surgeries for early-onset scoliosis: Literature review

BACKGROUND

The treatments for early-onset scoliosis (EOS), defined as curvature of the spine with onset before 10 years of age, continue to pose a great challenge for pediatric orthopedics. The treatment goals for EOS include minimizing spinal deformity while maximizing thoracic volume and pulmonary function. Different surgical techniques have different advantages and drawbacks; however, the two major concerns in the management of EOS are repeated surgeries and complications.

AIM

To review the current literature to assess the safety of EOS surgical treatment in terms of the rate of complications and unplanned surgeries.

METHODS

In January 2021 two independent reviewers systematically searched three electronic medical databases (PubMed, the Cochrane Library, and Embase) for relevant articles. Every step of the review was done according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Due to the heterogeneity of articles and topics after data analysis, a descriptive (synthetic) analysis was performed.

RESULTS

A total of 2136 articles were found. Forty articles were included in this systematic review, after applying our inclusion and exclusion criteria. EOS surgery has a varying but high rate of complications. The most frequent complications were categorized as implant (54%), general (17%), wound (15%) and alignment (12%). The rate of complications might have been even higher than reported, as some authors do not report all types of complications. About 54% of patients required unplanned surgeries due to complications, which comprised 15% of all surgeries.

CONCLUSION

The literature concerning the definitions, collection, and interpretation of data regarding EOS surgery complications is often difficult to interpret. This creates problems in the comparison, analysis, and improvement of spine surgery practice. Additionally, this observation indicates that data on the incidence of complications can be underestimated, and should be interpreted with caution. Awareness of the high rate of complications of EOS surgery is crucial, and an optimal strategy for prevention should become a priority.

Health and Economic Outcomes of Posterior Spinal Fusion for Children With Neuromuscular Scoliosis

OBJECTIVES

Neuromuscular scoliosis (NMS) can result in severe disability. Nonoperative management minimally slows scoliosis progression, but operative management with posterior spinal fusion (PSF) carries high risks of morbidity and mortality. In this study, we compare health and economic outcomes of PSF to nonoperative management for children with NMS to identify opportunities to improve care.

METHODS

We performed a cost-effectiveness analysis. Our decision analytic model included patients aged 5 to 20 years with NMS and a Cobb angle ≥50°, with a base case of 15-year-old patients. We estimated costs, life expectancy, quality-adjusted life-years (QALYs), and incremental cost-effectiveness from published literature and conducted sensitivity analyses on all model inputs.

RESULTS

We estimated that PSF resulted in modestly decreased discounted life expectancy (10.8 years) but longer quality-adjusted life expectancy (4.84 QALYs) than nonoperative management (11.2 years; 3.21 QALYs). PSF costs $75 400 per patient. Under base-case assumptions, PSF costs $50 100 per QALY gained. Our findings were sensitive to quality of life (QoL) and life expectancy, with PSF favored if it significantly increased QoL.

CONCLUSIONS

In patients with NMS, whether PSF is cost-effective depends strongly on the degree to which QoL improved, with larger improvements when NMS is the primary cause of debility, but limited data on QoL and life expectancy preclude a definitive assessment. Improved patient-centered outcome assessments are essential to understanding the effectiveness of NMS treatment alternatives. Because the degree to which PSF influences QoL substantially impacts health outcomes and varies by patient, clinicians should consider shared decision-making during PSF-related consultations.

Major perioperative complications after spine surgery in patients with cerebral palsy: assessment of risk factors

PURPOSE

A prospective, longitudinal cohort was studied to determine the incidence, consequences, and risk factors of major perioperative complications in patients with cerebral palsy (CP) treated with spinal fusion. There is a wide variety of data available on the complications of spine surgery; however, little exists on the perioperative complications in patients with CP.

METHODS

A prospective multicenter dataset of consecutive patients with CP treated with spinal fusion was evaluated. All major perioperative complications were identified and stratified into categories: pulmonary, gastrointestinal, other medical, wound infection, neurological, instrumentation related, and unplanned staged surgery. Univariate and multivariate analyses were performed to identify various risk factors for major perioperative complications.

RESULTS

127 patients were identified with a mean age of 14.3 ± 2.6 years. Overall, 39.4% of the patients had a major perioperative complication. Occurrence of a complication [no complication (NC), yes complication (YC)] resulted in significantly increased intensive care unit (ICU) (NC = 3.2 days, YC = 7.8 days, p < 0.05) and hospital stays (NC = 7.7 days, YC = 15.6 days, p < 0.05). Variables associated with greater risk of a complication included: increased estimated blood loss (EBL) (p < 0.001), larger preoperative kyphosis (p = 0.05), staged procedures (p < 0.05), a lack of antifibrinolytic use (p < 0.05), and a trend toward lower body mass index (BMI) (p = 0.08). Multivariate regression analysis revealed an increased EBL as independently associated with a major perioperative complication (p < 0.05).

CONCLUSIONS

In this cohort of patients with CP who underwent spinal fusion, 39.4% experienced a major perioperative complication, with pulmonary being the most common. The occurrence of a major perioperative complication lengthened both ICU and hospital stay. Risk factors for major perioperative complications included greater preoperative kyphosis, staged procedures, a lack of antifibrinolytic use, and increased EBL, with the latter being an independent predictor of a major perioperative complication.

LEVEL OF EVIDENCE

2.

Surgical correction of scoliosis in children with spastic quadriplegia: benefits, adverse effects, and patient selection

STUDY RATIONALE

Cerebral palsy (CP) is a group of nonprogressive syndromes of posture and motor impairment associated with lesions of the immature brain. Spastic quadriplegia is the most severe form with a high incidence of scoliosis, back pain, respiratory compromise, pelvic obliquity, and poor sitting balance. Surgical stabilization of the spine is an effective technique for correcting deformity and restoring sitting posture. The decision to operate in this group of patients is challenging.

OBJECTIVES

The aim of this study is to determine the benefits of surgical correction of scoliosis in children with spastic quadriplegia, the adverse effects of this treatment, and what preoperative factors affect patient outcome after surgical correction.

MATERIALS AND METHODS

A systematic review was undertaken to identify studies describing benefits and adverse effects of surgery in spastic quadriplegia. Factors affecting patient outcome following surgical correction of scoliosis were assessed. Studies involving adults and nonspastic quadriplegia were excluded.

RESULTS

A total of 10 case series and 1 prospective and 3 retrospective cohort studies met inclusion criteria. There was significant variation in the overall risk of complications (range, 10.9-70.9%), mortality (range, 2.8-19%), respiratory/pulmonary complications (range, 26.9-57.1%), and infection (range, 2.5-56.8%). Factors associated with a worse outcome were a significant degree of thoracic kyphosis, days in the intensive care unit, and poor nutritional status.

CONCLUSION

Caregivers report a high degree of satisfaction with scoliosis surgery for children with spastic quadriplegia. There is limited evidence of preoperative factors that can predict patient outcome after scoliosis. There is a need for well-designed prospective studies of scoliosis surgery in spastic quadriplegia.

Prevalence of complications in neuromuscular scoliosis surgery: a literature meta-analysis from the past 15 years

PURPOSE

Our objectives were primarily to review the published literature on complications in neuromuscular scoliosis (NMS) surgery and secondarily, by means of a meta-analysis, to determine the overall pooled rates (PR) of various complications associated with NMS surgery.

METHODS

PubMed and Embase databases were searched for studies reporting the outcomes and complications of NMS surgery, published from 1997 to May 2011. We focused on NMS as defined by the Scoliosis Research Society's classification. We measured the pooled estimate of the overall complication rates (PR) using a random effects meta-analytic model. This model considers both intra- and inter-study variation in calculating PR.

RESULTS

Systematic review and meta-analysis were performed for 68 cohort and case-control studies with a total of 15,218 NMS patients. Pulmonary complications were the most reported (PR = 22.71 %) followed by implant complications (PR = 12.51 %), infections (PR = 10.91 %), neurological complications (PR = 3.01 %) and pseudoarthrosis (PR = 1.88 %). Revision, removal and extension of implant had highest PR (7.87 %) followed by malplacement of the pedicle screws (4.81 %). Rates of individual studies have moderate to high variability. The studies were heterogeneous in methodology and outcome types, which are plausible explanations for the variability; sensitivity analysis with respect to age at surgery, sample size, publication year and diagnosis could also partly explain this variability. In regard to surgical complications affiliated with various surgical techniques in NMS, the level of evidence of published literature ranges between 2+ to 2-; the subsequent recommendations are level C.

CONCLUSION

NMS patients have diverse and high complication rates after scoliosis surgery. High PRs of complications warrant more attention from the surgical community. Although the PR of all complications are affected by heterogeneity, they nevertheless provide valuable insights into the impact of methodological settings (sample size), patient characteristics (age at surgery), and continual advances in patient care on complication rates.

Cotrel-Dubousset instrumentation in neuromuscular scoliosis

The study design is retrospective. The aim is to describe our experience about the treatment of patients with neuromuscular scoliosis (NMS) using Cotrel-Dubousset instrumentation. Neuromuscular scoliosis are difficult deformities to treat. A careful assessment and an understanding of the primary disease and its prognosis are essential for planning treatment which is aimed at maximizing function. These patients may have pelvic obliquity, dislocation of the hip, limited balance or ability to sit, back pain, and, in some cases, a serious decrease in pulmonary function. Spinal deformity is difficult to control with a brace, and it may progress even after skeletal maturity has been reached. Surgery is the main stay of treatment for selected patients. The goals of surgery are to correct the deformity producing a balanced spine with a level pelvis and a solid spinal fusion to prevent or delay secondary respiratory complications. The instrumented spinal fusion (ISF) with second-generation instrumentation (e.g., Luque-Galveston and unit rod constructs), are until 1990s considered the gold standard surgical technique for neuromuscular scoliosis (NMS). Still in 2008 Tsirikos et al. said that "the Unit rod instrumentation is a common standard technique and the primary instrumentation system for the treatment of pediatric patients with cerebral palsy and neuromuscular scoliosis because it is simple to use, it is considerably less expensive than most other systems, and can achieve good deformity correction with a low loss of correction, as well as a low prevalence of associated complications and a low reoperation rate." In spite of the Cotrel-Dubousset (CD) surgical technique, used since the beginning of the mid 1980s, being already considered the highest level achieved in correction of scoliosis by a posterior approach, Teli et al., in 2006, said that reports are lacking on the results of third-generation instrumentation for the treatment of NMS. Patients with neuromuscular disease and spinal deformity treated between 1984 and 2008 consecutively by the senior author (G.D.G.) with Cotrel-Dubousset instrumentation and minimum 36 months follow-up were reviewed, evaluating correction of coronal deformity, sagittal balance and pelvic obliquity, and rate of complications. 24 patients (Friedreich's ataxia, 1; cerebral palsy, 14; muscular dystrophy, 2; polio, 2; syringomyelia, 3; spinal atrophy, 2) were included. According the evidence that the study period is too long (1984-2008) and that in more than 20 years many things changed in surgical strategy and techniques, all patients were divided in two groups: only hooks (8 patients) or hybrid construct (16 patients). Mean age was 18.1 years at surgery (range 11 years 7 months-max 31 years; in 17 cases the age at surgery time was between 10 and 20 years old; in 6 cases it was between 20 and 30 and only in 1 case was over 30 years old). Mean follow-up was 142 months (range 36-279). The most frequent patterns of scoliosis were thoracic (10 cases) and thoracolumbar (9 cases). In 8 cases we had hypokyphosis, in 6 normal kyphosis and in 9 hyperkyphosis. In 8 cases we had a normal lordosis, in 11 a hypolordosis and in 4 a hyperlordosis. In 1 case we had global T4-L4 kyphosis. In 8 cases there were also a thoracolumbar kyphosis (mean value 24°, min 20°-max 35°). The mean fusion area included 13 vertebrae (range 6-19); in 17 cases the upper end vertebra was over T4 and in 11 cases the lower end vertebra was over L4 or L5. In 7 cases the lower end vertebra was S1 to correct the pelvic obliquity. In 5 cases the severity of the deformity (mean Cobb's angle 84.2°) imposed a preoperative halo traction treatment. There were 5 anteroposterior and 19 posterior-only procedures. In 10 cases, with low bone quality, the arthrodesis was performed using iliac grafting technique while in the other (14 cases) using autologous bone graft obtained in situ from vertebral arches and spinous processes (in all 7 cases with fusion extended until S1, it was augmented with calcium phosphate). The mean correction of coronal deformity and pelvic obliquity averaged, respectively, 57.2% (min 31.8%; max 84.8%) and 58.9% (mean value preoperative, 18.43°; mean value postoperative, 7.57°; mean value at last follow-up, 7.57°). The sagittal balance was always restored, reducing hypo or hyperkyphosis and hypo or hyperlordosis. Also in presence of a global kyphosis, we observed a very good restoration (preoperatory, 65°; postoperatory, 18° kyphosis and 30° lordosis, unmodified at last f.u.). The thoracolumbar kyphosis, when present (33.3% of our group) was always corrected to physiological values (mean 2°, min 0°-max 5°). The mean intraoperative blood lost were 2,100 cc (min 1,400, max 5,350). Major complications affected 8.3% of patients, and included 1 postoperative death and 1 deep infection. Minor complications affected none of patients. CD technique provides lasting correction of spinal deformity in patients with neuromuscular scoliosis, with a lower complications rate compared to reports on second-generation instrumented spinal fusion.

Development and treatment of spinal deformity in patients with cerebral palsy

Scoliosis is a common deformity in children and adolescents with cerebral palsy. This is usually associated with pelvic obliquity due to extension of the curve to the sacrum. Sagittal plane deformity is less common and often develops along with scoliosis. Spinal deformity in patients with severe neurological handicaps can affect their ability to sit and cause significant back pain or pain due to rib impingement against the elevated side of the pelvis on the concavity of the curvature. Surgical correction followed by spinal arthrodesis is indicated in patients with progressive deformities which interfere with their level of function and quality of life. Spinal deformity correction is a major task in children with multiple medical co-morbidities and can be associated with a high risk of complications including death. A well-coordinated multidisciplinary approach is required in the assessment and treatment of this group of patients with the aim to minimize the complication rate and secure a satisfactory surgical outcome. Good knowledge of the surgical and instrumentation techniques, as well as the principles of management is needed to achieve optimum correction of the deformity and balancing of the spine and pelvis. Spinal fusion has a well-documented positive impact even in children with quadriplegia or total body involvement and is the only surgical procedure which has such a high satisfaction rate among parents and caregivers.

Genetic linkage localizes an adolescent idiopathic scoliosis and pectus excavatum gene to chromosome 18 q

STUDY DESIGN

A single large family, in which adolescent idiopathic scoliosis (AIS) and pectus excavatum (PE) segregate as an autosomal dominant condition, was evaluated. Genome-wide linkage analysis and candidate gene sequencing were performed.

OBJECTIVE

To map the disease-causing locus in a large white family in which AIS and PE cosegregate.

SUMMARY OF BACKGROUND DATA

AIS and PE are common musculoskeletal conditions known to have a genetic component, though few genes have been identified for either. Genetic studies have been confounded by a lack of large families in which the disorders segregate.

METHODS

Clinical examinations were performed on the proband, who underwent posterior spinal fusion, and 12 additional affected family members. To map a gene causing AIS and PE, a genome-wide linkage analysis was performed with the Affymetrix Mapping 10 K XbaI array on 13 affected and 10 unaffected family members. Candidate genes were sequenced.

RESULTS

AIS was present in 13 female family members and PE was present in 3 males and 1 female. Genome-wide linkage analysis resulted in a linkage peak on chromosome 18 q with a maximum parametric multipoint logarithm of the odds score of 3.86. Recombinants delineated the critical genetic region to an interval of 6.4 cM between SNP_A-1519369 and SNP_A-1507702, corresponding to a 7.06-Mb region (hg18: chr18:26342508-34395660). The chromosome 18 q linkage region contains more than 30 genes. Resequencing of the coding regions of 21 candidate genes in the region did not reveal any causative mutation.

CONCLUSION

Linkage analysis in this large family demonstrated a novel locus for AIS and PE on chromosome 18 q. Because of the increased frequency of PE in family members of AIS patients, consideration of family members with PE as affected may increase the power of AIS genetic linkage studies.

Rate of complications in scoliosis surgery - a systematic review of the Pub Med literature

Background

Spinal fusion surgery is currently recommended when curve magnitude exceeds 40–45 degrees. Early attempts at spinal fusion surgery which were aimed to leave the patients with a mild residual deformity, failed to meet such expectations. These aims have since been revised to the more modest goals of preventing progression, restoring 'acceptability' of the clinical deformity and reducing curvature.

In view of the fact that there is no evidence that health related signs and symptoms of scoliosis can be altered by spinal fusion in the long-term, a clear medical indication for this treatment cannot be derived. Knowledge concerning the rate of complications of scoliosis surgery may enable us to establish a cost/benefit relation of this intervention and to improve the standard of the information and advice given to patients. It is also hoped that this study will help to answer questions in relation to the limiting choice between the risks of surgery and the "wait and see – observation only until surgery might be recommended", strategy widely used. The purpose of this review is to present the actual data available on the rate of complications in scoliosis surgery.

Materials and methods

Search strategy for identification of studies; Pub Med and the SOSORT scoliosis library, limited to English language and bibliographies of all reviewed articles. The search strategy included the terms; 'scoliosis'; 'rate of complications'; 'spine surgery'; 'scoliosis surgery'; 'spondylodesis'; 'spinal instrumentation' and 'spine fusion'.

Results

The electronic search carried out on the 1^st February 2008 with the key words "scoliosis", "surgery", "complications" revealed 2590 titles, which not necessarily attributed to our quest for the term "rate of complications". 287 titles were found when the term "rate of complications" was used as a key word. Rates of complication varied between 0 and 89% depending on the aetiology of the entity investigated. Long-term rates of complications have not yet been reported upon.

Conclusion

Scoliosis surgery has a varying but high rate of complications. A medical indication for this treatment cannot be established in view of the lack of evidence. The rate of complications may even be higher than reported. Long-term risks of scoliosis surgery have not yet been reported upon in research. Mandatory reporting for all spinal implants in a standardized way using a spreadsheet list of all recognised complications to reveal a 2-year, 5-year, 10-year and 20-year rate of complications should be established. Trials with untreated control groups in the field of scoliosis raise ethical issues, as the control group could be exposed to the risks of undergoing such surgery.