Table of Contents
Abstract
Citation: Bessaguet H, Rousseau M-C, Gautheron V, Ojardias E, Dohin B (2024) Impact of spinal fusion on severity health status in scoliotic adolescents with polyhandicap. PLoS ONE 19(3):
e0300065.
doi.org/10.1371/journal.pone.0300065
Editor: Kentaro Yamada, Tokyo Medical and Dental University (TMDU), JAPAN
Received: January 17, 2023; Accepted: February 19, 2024; Published: March 7, 2024
Copyright: © 2024 Bessaguet et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting information files.
Funding: This research did not receive any specific grant from funding agencies in the public, commercial or not-for-profit sectors.
Competing interests: The authors have declared that no competing interests exist.
Abbreviations:
abPSS,
Polyhandicap Severity Scale abilities subscore; BMI,
Body Mass Index; coPSS,
Polyhandicap Severity Scale comorbidities and impairments subscore; CP,
Cerebral Palsy; DWI,
Deep Wound Infection; FB,
Frontal Balance; FCA,
Frontal Cobb Angle; FIM,
Functional Independence Measure; GMFCS,
Gross Motor Function Classification System; ICF,
International Classification of Functioning, disability and health; ICU,
Intensive Care Unit; IT,
Intra Thecal; mCDS,
modified Clavien-Dindo-Sink; OBL,
; PI,
Pelvic Incidence; PLH,
Polyhandicap; PolyQoL,
Quality of life questionnaire for persons with polyhandicap; PSS,
Polyhandicap Severity Scale; PT,
Pelvic Til; QoL,
Quality of life; SB,
Sagittal Balance; SCA,
Sagittal Cobb Angle; SS,
Sacral Slope
Introduction
Polyhandicap (PLH) is currently defined as a complex disability condition corresponding to a chronic affliction occurring in an immature brain [1], leading to the combination of severe/profound mental retardation and serious motor impairment, resulting in an extreme restriction of autonomy and communication [2,3].
As comorbidities accumulate in patients with PLH throughout their lives, impairments, activity limitations and health-related quality of life (QoL) worsen [4]. Among comorbidities in patients with PLH, scoliosis represents one of the most prevalent conditions with chronic respiratory insufficiency [5–7], chronic digestive disorders, or epilepsy [8]. Indeed, Rousseau et al. [9] estimated that the prevalence of severe scoliosis (scoliosis with Cobb angle >50°) prevalence was 60.2%, accounting for a large proportion of deaths induced by respiratory failure. The latter, represents the main cause of death in adults with PLH [9] (63.2%).
Even if the natural history [10], risk factors, treatments [11,12] and complications [13] of scoliosis with Cobb angle >50° are well known in nonambulant cerebral palsy (CP) patients (Gross Motor Function Classification System—GMFCS level 5), few data are available in PLH [3].
Hodgkinson et al. [14] found severe neuro-orthopaedic impairments in adolescents with PLH were associated with poor general condition. They hypothesized that multidisciplinary therapeutic strategies must include surgical scoliosis treatment to improve pain, comfort, and positioning. However, Cassidy et al. [15] found no differences in terms of pain, function, or time for daily care when comparing adolescents with PLH who underwent thoracolumbar spinal fusion with the nonoperated control group. De Lattre et al. [16] also failed to demonstrate improvements in health status between non operated and operated adolescents with PLH. They also reported a high rate of per- and postoperative complications (93,7%). McCarthy et al. [17] reported a rate of perioperative death up to 7% in nonambulant CP patients.
Previous studies estimated that 12% to 32% of subjects with PLH underwent scoliosis surgery [9]. Thus, there is still considerable interest in investigating whether scoliosis surgery truly confers measurable benefits on subsequent health and daily life comfort in adolescents with PLH. If it is hypothesized that surgeries lead to measurable clinical and radiological benefits, valid clinical evaluations are lacking.
The aims of this study were first to evaluate whether the health status variation in adolescents with PLH was improved after scoliosis surgery and second to evaluate the incidence of perioperative complications.
Material and methods
Data
Data were collected by independent evaluators using a specific research algorithm corresponding to the French nomenclature of surgically performed acts. All variables of interest were subsequently extracted from the eligible charts. In addition, we contacted families through phone calls to document parent’s feelings about their adolescent’s QoL after surgery. Two independent evaluators (HB and EO) performed X-ray measurements to reduce ascertainment bias. In cases of disagreement (>6° or >7° differences between two measurements, respectively in frontal and sagittal planes), the referring surgeon (BD) arbitrated the decision. For all outcomes, we only considered the earliest preoperative measurements and the latest postoperative ones.
Data extraction was completed from computerized charts by the first author (HB) who was not involved in the surgical procedure nor medical postoperative follow-up. Method for fulfilling evaluation form was as exhaustive as possible to limit risk of bias. Age at surgery, sex, care facility, preoperative FIM, past surgical history, PLH aetiology, type of physical disability, pain, body mass index (BMI), spontaneous posture, communication level, feeding strategies, and presence of medical devices were extracted. These data were compiled to rate the severity health status of each participant [19] according to the Polyhandicap Severity Scale (PSS). The PSS provides an accurate evaluation of health status regarding abilities, comorbidities and impairments, and assesses the level of global severity of the health status of persons with PLH. This scale ranges scores from 0 to 129, from less to higher levels of severity. A global PSS score was calculated as the sum of the two PSS subscores, respectively “comorbidities and impairments” (coPSS, ranging from 0 to 69) and “abilities” (abPSS, ranging from 0 to 60), according to the International Classification of Functioning, Disability and Health (ICF). Semi structured interviews (see Fig 2) were conducted with families to collect verbatim interviews. We also rated pre- and postoperative PolyQoL scores [20]. This validated short-scale is composed of two domains called health and social, ranging QoL scores from 0 (worst) to 100 (better).
X-ray parameters were extracted from pre- and postoperative X-rays (sagittal and frontal). A specific software program (Surgimap Spine® 2021, Nemaris, Inc.) was used for all spinal and pelvic measurements, as it offers semiautomatic procedures with good inter- and intraobserver reliability, even on instrumented spines. Frontal X-ray data included skeletal maturity (Risser test), frontal Cobb angles (FCA), pelvic obliquity (OBL) and frontal balance (FB). Sagittal parameters included sagittal Cobb angles (SCA) and sagittal balance (SB). Using the same software, we measured pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS). Frontal and sagittal curves were added separately to obtain a “full curvature degree” for each participant, reflecting the amount of deformity.
Peri- and postoperative complications ranged according to the modified Clavien-Dindo-Sink classification [21] (mCDS). We collected blood loss data (loss of more than 1 blood volume), deep wound infections (DWI) and operative durations. We also calculated hospital lengths of stay, composed of the sum of paediatric surgery, intensive care unit (ICU), and rehabilitation department stays (days of hospitalization).
Statistical analysis
We first checked if variables followed a normal distribution. Descriptive statistics were reported as means with standard deviation (SD) for quantitative variables and frequencies for qualitative variables (%). We used paired t tests for normally distributed variables for comparison of pre- and postoperative variables. Wilcoxon matched-pairs signed rank tests were used for nonparametric repartitions. Univariate analysis was conducted for postoperative PSS scores and PSS score variations and their related subscores, using Mann-Whitney tests for qualitative variables and Spearman correlation matrices for quantitative data (Prism GraphPad® software for Windows, version 5.03, San Diego California USA, www.graphpad.com). Significance threshold was set at p < 0.05.
Results
Descriptive data
The mean age at surgery was 15 (3) years old. The preoperative mean FIM was 22 (10). PLH aetiology was unknown for 8 adolescents and progressive for 6 adolescents. Twenty patients had undergone previous orthopaedic surgery, mainly multilevel tenotomy surgery (n = 9). The mean BMI before surgery was 17.4 (3.9) kg/m². Descriptive data are reported in Table 1.
The mean preoperative scores were 53 (17), 14 (5), and 39 (13) for PSS (/129), coPSS (/69) and abPSS (/60) respectively. For postoperative scores, we found a score of 49 (16) for PSS, a score of 12 (4) for coPSS and a score of 37 (13) for abPSS. Data were missing in 3 cases: 1 adolescent died during surgery and 2 medical records were insufficient for exhaustive PSS grading before and after surgery. Another adolescent died 7 days after surgery, but postoperative PSS scoring was possible. Seven caregivers agreed to answer semistructured interviews. The mean preoperative PolyQoL score was 64 (12). Mean postoperative PolyQoL score was 77 (10). Pre- and postoperative data, with related means of difference, are shown in Table 2. A scatter plot of individual preoperative versus postoperative PSS scores is provided in Fig 4.
Fig 4. Scatter plot of individual preoperative versus postoperative PSS scores.
Mean PSS evolution with standard error is represented by the large red solid line with error bar. PSS evolution i.e improvement (n = 18; dark solid line), stability (n = 8; grey solid line), worsening (n = 1; grey dashed line) are represented for each individual.
For complications, all the subjects presented at least 1 per- or postoperative complication. Among them, 9 were rated grade 1, and 10 were rated grade 4 according to the mCDS classification (Fig 5). More accurately, 6 presented with a deep wound infection (DWI), and 13 with a major blood loss. Neither neurologic, nor digestive or pancreatic complications were noted postoperatively in the patients. Finally, we found a mortality rate of 6.7% during follow-up: 1 death occurred during the surgical procedure, which was related to heart failure during anaesthesia, and 1 in the ICU due to multisystemic failure 7 days after surgery.
Fig 5. Proportions (%) of complications as classified by mCDS scoring (minor to severe complications, from grade 1 to 5).
Grade 1 (n = 9): Wound leakage, constipation, nonsevere lung infection; Grade 2 (n = 5): Non severe dura mater breach, delayed wound healing; Grade 3 (n = 2): Deep wound infection, treated with second surgery + IV antibiotics; Grade 4 (n = 10): Any complication requiring ICU admission: Complex deep wound infection, renal failure, urinary sepsis, severe lung infection, delayed awakening after anaesthesia, central venous catheter infection; Grade 5 (n = 2): Per operative death or early postoperative death (within 7 days); NA (n = 2): Missing data.
The mean hospital length of stay was 44.7 days (20 to 83 days), respectively comprising 3.6 (2.7) days (1 to 10) in the ICU, 14.3 (8.3) days (1 to 34) in the paediatric surgery department, and 26.9 (12.9) days (0 to 56) in the rehabilitation department.
Discussion
In the present study, we aimed to describe comorbidities, impairments, activity limitations and QoL before and after spinal fusions in adolescents with PLH. We hypothesized that these surgeries lowered the severity health status and conferred clinical benefits. Our hypothesis was confirmed as PSS, coPSS and abPSS scores were significantly improved. We have nevertheless highlighted a 100% rate of complications and 2 deaths, testifying to the complexity of these surgeries.
Comorbidities, impairments, and activity limitations were evaluated, as outlined above, with the PSS. This scale allows us to quantify the severity health status of patients with PLH, providing a new ICF-standardized and exhaustive approach for clinical assessments. We believe in that better preoperative clinical specifications could help in identifying patients who may better tolerate and benefit from spinal fusions. Scoliosis surgery seems to represent a strong contribution to the long-term management of health in persons with PLH [2]. The results of our study demonstrate that spinal fusion surgery in adolescents with PLH leads to a reduction in comorbidities (respiratory, digestive, skin, behavioural, pain, etc.) and seems to allow a slight improvement in neurodevelopmental status.
Moreover in this study, we could interview seven of all families through semistructured questionnaires: witness families reported that spinal fusions conferred a global improvement in QoL. The parents’ statements were mostly positive: during the preoperative period, they had difficulty accepting the vital risk of spinal surgery, but in retrospect, they recognized 1) that the surgery was necessary, and 2) that their child’s health (breathing, posture…) had improved even when peroperative and immediate postoperative complications surrounded. Moreover, we used a validated tool called the PolyQoL questionnaire to objectively document QoL. We did not show any significant improvement regarding PolyQoL scores, but these results must be taken with caution, likely due to our small sample of answers.
Parents and caregivers were particularly attentive to the experience before and during the surgical period and reported having psychologically benefited from preoperative comprehensive explanations. Half of them verbalized the “inevitability” of this surgery. As highlighted by Adams et al. [22], agreements on the goals of surgery between surgeons and caregivers are important. While surgeons and physicians tend to give top priority to sitting considerations, caregivers put head control and physical appearance first. The expected benefits seem to remain superior to the risk of complications, but the therapeutic strategy requires an individualized evaluation rigorously explained to caregivers of PLH adolescents [22,23]. The question of long-term clinical benefits remains important, as follow-up is rarely conducted for more than 1 year [24].
Families are often afraid when scoliosis surgery is considered for their adolescent [25]. The postoperative complication rate (100%) and perioperative mortality rate (6,7%) must be included in the decision and balanced with improvements in severity health status. In our study, the DWI rate was 20%, which is almost twice the rate as previous studies reported in CP [26] (but CP adolescents present a less severe health status than PLH adolescents we analysed). Nutritional status of patients with PLH could be questioned to explain the difference.
Geometric spine readjustment could be one of the reasons for pain alleviation by costo-pelvic impingement prevention and sitting comfort improvement [27]. We observed a reduction in bed sore frequency and gluteal erosions after surgery. We confirmed a significant improvement in BMI after surgery (mean variation of +1,37 kg/m²). As presumed in some studies, straightening the thoracolumbar spine could increase the abdominal space, allowing better peristalsis and less regurgitation [28]. However, severe postoperative pancreatitis cases have been reported after extensive arthrodesis, but we did not report any case in our population.
Regarding medical devices, we observed that IT baclofen pumps did not increase the complication rate, which is consistent with previous studies [29]. Similarly, gastrostomies were not associated with a major complication occurrence in our PLH patients, unlike CP GMFCS V patients in whom an increased risk has been shown previously [30]. Except for DWI, severe complications were mostly respiratory. Lung developmental defects, impaired neurologic command over added lung restrictive syndromes and postoperative intensive care with lung infection risks can partially explain our findings [6]. Preoperative breathing hyper insufflation strategies could be worthwhile as they demonstrated interest in spinal fusions in children with neuromuscular flaccid scoliosis [31]. As preoperative primary care visits led to lower costs and shorter hospitalizations in complex scoliosis surgeries, we support the idea of efficient preoperative rehabilitation programs before spinal fusions. Rehabilitation modalities could be determined according to the domains impacted in the preoperative PSS scoring.
Cobb corrections were 58% for FCA and 30% for SCA. Spinal fusions in adolescents with PLH provide comparable results to those found in GMFCS IV and V adolescents with CP (50 to 68% as reported). A mean PT variation of -7.8° (22.4) was observed, corresponding to a significant reduction in pelvis back-tilting. The mean correction for OBL was 47%. This X-ray parameter was correlated with the postoperative PSS score and PSS variations induced by surgery.
Strengths and limitations
Our study demonstrates for the first time, that spinal fusions reduce the global severity of adolescents with polyhandicap. However, it contains several limitations: our study was monocentric and retrospective data collection may have provided methodological bias. Broadening inclusions to various specialized centers could be of interest in a prospective approach. Longer follow-up (2–5 years) would enable us to assess the long-term effect of spinal fusion surgery on the severity health status of patients with PLH, thus further prospective studies with a longer follow-up are needed (therefore, the present one-year follow-up evaluation should not be considered as the final evaluation). By increasing the duration of follow-up and through the methodical use of standardized tools such as PSS [19] and PolyQoL [20], establishing accurate and repeatable ICF-based descriptions in patients with PLH appears to be easier. An increased sample size could also help in analysing predictive factors of clinical improvement after spinal fusions, keeping in mind the potential confounding factors we highlighted.
One of the main issues when performing spinal fusions in patients with PLH is the assessment of predicted benefits. This study aimed to support the rationale for spinal fusion, acknowledging the already known complication rates and risks in PLH adolescents. Considering the severity of the health status evaluation of these patients and the expected improvement of the global health status and comfort after spine surgery for scoliosis, each case requires careful consideration and evaluation. We support that, under the condition of acceptable preoperative health status, the indication for spinal fusion in that population could be relevant and reasonable. While retrospective evaluation is questionable, the rigorous method used during data collection should limit this bias. The PolyQoL questionnaire has been supported by the verbatim collected in a part of the population, and obviously the good health status of the patients at final follow-up confirms our hypothesis.
References
- 1.
Chabrier S, Pouyfaucon M, Chatelin A, Bleyenheuft Y, Fluss J, Gautheron V, et al. From congenial paralysis to post-early brain injury developmental condition: Where does cerebral palsy actually stand? Ann Phys Rehabil Med. 2019 Aug;S1877065719301137. pmid:31421273 - 2.
Rousseau MC, Baumstarck K, Auquier P, Billette de Villemeur T. Health characteristics and health care trajectory of polyhandicaped person before and after 1990. Rev Neurol (Paris). 2020 Jan-Feb;176(1–2):92–99. Epub 2019 Jun 27. pmid:31255322. - 3.
Maes B, Nijs S, Vandesande S, Van Keer I, Arthur-Kelly M, Dind J, et al. Looking back, looking forward: Methodological challenges and future directions in research on persons with profound intellectual and multiple disabilities. J Appl Res Intellect Disabil. 2021 Jan;34(1):250–62. pmid:33073444 - 4.
Mensch SM, Echteld MA, Lemmens R, Oppewal A, Evenhuis HM, Rameckers EAA. The relationship between motor abilities and quality of life in children with severe multiple disabilities: Motor abilities and quality of life in children with SMD. J Intellect Disabil Res. 2019 Feb;63(2):100–12. - 5.
Gautheron V, Mathevon L, Bayle B, Boulard C, Paricio C, Seeman E, et al. Problèmes respiratoires des personnes polyhandicapées: le point de vue du médecin de médecine physique et de réadaptation. Mot Cérébrale Réadapt Neurol Dév. 2015 Jun;36(2):49–53. - 6.
Proesmans M, Vreys M, Huenaerts E, Haest E, Coremans S, Vermeulen F, et al. Respiratory morbidity in children with profound intellectual and multiple disability: Respiratory Morbidity and Neurocognitive Impairment. Pediatr Pulmonol. 2015 Oct;50(10):1033–8. - 7.
Boel L, Pernet K, Toussaint M, Ides K, Leemans G, Haan J, et al. Respiratory morbidity in children with cerebral palsy: an overview. Dev Med Child Neurol [Internet]. 2018 Oct 15 [cited 2019 Jan 23]; doi.wiley.com/10.1111/dmcn.14060 pmid:30320434 - 8.
Arvio M, Sillanpää M. Prevalence, aetiology and comorbidity of severe and profound intellectual disability in Finland. J Intellect Disabil Res. 2003 Feb;47(Pt 2):108–12. pmid:12542576 - 9.
Rousseau MC, Mathieu S, Brisse C, Motawaj M, Grimont E, Auquier P, et al. Aetiologies, comorbidities and causes of death in a population of 133 patients with polyhandicaps cared for at specialist rehabilitation centres. Brain Inj. 2015 Jul 3;29(7–8):837–42. pmid:25950262 - 10.
Saito N, Ebara S, Ohotsuka K, Kumeta H, Takaoka K. Natural history of scoliosis in spastic cerebral palsy. Lancet Lond Engl. 1998 Jun 6;351(9117):1687–92. pmid:9734885 - 11.
Tsirikos A. Development and treatment of spinal deformity in patients with cerebral palsy. Indian J Orthop. 2010;44(2):148. pmid:20419001 - 12.
Dohin B. The spastic hip in children and adolescents. Orthop Traumatol Surg Res. 2019 Feb;105(1):S133–41. pmid:30056240 - 13.
Jain A, Sponseller PD, Shah SA, Samdani A, Cahill PJ, Yaszay B, et al. Subclassification of GMFCS Level-5 Cerebral Palsy as a Predictor of Complications and Health-Related Quality of Life After Spinal Arthrodesis: J Bone Jt Surg. 2016 Nov;98(21):1821–8. pmid:27807115 - 14.
Hodgkinson I, Jindrich ML, Metton G, Berard C. Bassin oblique, luxation de hanche et scoliose dans une population de 120 adultes polyhandicapés. Étude descriptive. Ann Réadapt Médecine Phys. 2002 Feb;45(2):57–61. - 15.
Cassidy C, Craig CL, Perry A, Karlin LI, Goldberg MJ. A reassessment of spinal stabilization in severe cerebral palsy. J Pediatr Orthop. 1994 Nov 1;14(6):731–9. pmid:7814585 - 16.
de Lattre C, Hodgkinson I, Bérard C. Retentissement de la scoliose chez les patients polyhandicapés: étude descriptive de 61 enfants et adultes polyhandicapés avec ou sans arthrodèse vertébrale. Ann Réadapt Médecine Phys. 2007 May;50(4):218–24. - 17.
McCarthy JJ, DʼAndrea LP, Betz RR, Clements DH. Scoliosis in the Child With Cerebral Palsy: J Am Acad Orthop Surg. 2006 Jun;14(6):367–75. pmid:16757676 - 18.
Rousseau M-C, Winance M, Baumstarck K. Polyhandicap, profound intellectual multiple disabilities: Concept and definition of a highly specific public health issue. Rev Epidemiol Sante Publique 2023;71:102184. - 19.
Rousseau MC, Baumstarck K, Hamouda I, Valkov M, Felce A, Khaldi-Cherif S, et al. Development and initial validation of the polyhandicap severity scale. Rev Neurol (Paris). 2021 Jun;177(6):683–9. pmid:33069376 - 20.
Hamouda I, Rousseau MC, Aim MA, Anzola AB, Loundou A, De Villemeur TB, et al. Development and initial validation of the quality of life questionnaire for persons with polyhandicap (PolyQoL). Ann Phys Rehabil Med. févr 2023;66(1):101672. pmid:35490967 - 21.
Dodwell ER, Pathy R, Widmann RF, Green DW, Scher DM, Blanco JS, et al. Reliability of the Modified Clavien-Dindo-Sink Complication Classification System in Pediatric Orthopaedic Surgery. JBJS Open Access. 2018 Dec 20;3(4):e0020. pmid:30882054 - 22.
Adams AJ, Refakis CA, Flynn JM, Pahys JM, Betz RR, Bastrom TP, et al. Surgeon and Caregiver Agreement on the Goals and Indications for Scoliosis Surgery in Children With Cerebral Palsy. Spine Deform. 2019 Mar;7(2):304–11. pmid:30660226 - 23.
Tsirikos AI, Chang WN, Dabney KW, Miller F. Comparison of parents’ and caregivers’ satisfaction after spinal fusion in children with cerebral palsy. J Pediatr Orthop. 2004 Jan-Feb;24(1):54–8. pmid:14676534. - 24.
Miyanji F, Nasto LA, Sponseller PD, Shah SA, Samdani AF, Lonner B, et al. Assessing the Risk-Benefit Ratio of Scoliosis Surgery in Cerebral Palsy: Surgery Is Worth It. J Bone Jt Surg. 2018 Apr;100(7):556–63. pmid:29613924 - 25.
Rousseau MC, Billette de Villemeur T, Khaldi-Cherif S, Brisse C, Felce A, Baumstarck K, et al. Adequacy of care management of patients with polyhandicap in the French health system: A study of 782 patients. Simeoni U, editor. PLOS ONE. 2018 Jul 6;13(7):e0199986. pmid:29979745 - 26.
Sponseller PD, Shah SA, Abel MF, Newton PO, Letko L, Marks M. Infection Rate after Spine Surgery in Cerebral Palsy is High and Impairs Results: Multicenter Analysis of Risk Factors and Treatment. Clin Orthop. 2010 Mar;468(3):711–6. pmid:19543779 - 27.
Roberts SB, Tsirikos AI. Factors influencing the evaluation and management of neuromuscular scoliosis: A review of the literature. J Back Musculoskelet Rehabil. 2016 Nov 21;29(4):613–23. pmid:26966821 - 28.
DeFrancesco CJ, Miller DJ, Cahill PJ, Spiegel DA, Flynn JM, Baldwin KD. Releasing the tether: Weight normalization following corrective spinal fusion in cerebral palsy. J Orthop Surg. 2018 May;26(2):230949901878255. pmid:29938586 - 29.
Buxton K, Difazio R, Morgan A, McCabe M, Forbes PW. Intrathecal Baclofen Therapy Prior to Spinal Fusion for Patients With Gross Motor Function Classification System IV-V Cerebral Palsy: Orthop Nurs. 2018;37(2):136–43. pmid:29570548 - 30.
Nishnianidze T, Bayhan IA, Abousamra O, Sees J, Rogers KJ, Dabney KW, et al. Factors predicting postoperative complications following spinal fusions in children with cerebral palsy scoliosis. Eur Spine J. 2016 Feb;25(2):627–34. pmid:26410446 - 31.
Mills B, Bach JR, Sabharwal S. Posterior Spinal Fusion in Children with Flaccid Neuromuscular Scoliosis: The Role of Noninvasive Positive Pressure Ventilatory Support. J Pediatr Orthop. 2013;33(5):6. pmid:23752144
