Prediction of thoracic dimensions and spine length based on individual pelvic dimensions in children and adolescents: an age-independent, individualized standard for evaluation of outcome in early onset spinal deformity

Functional Outcomes of Congenital Scoliosis at a Mean 35-Year Follow-up Post In Situ Fusion. Revisiting Patients From the 2002 Goldberg et al Study

BACKGROUND

The management of congenital scoliosis poses a significant challenge for treating surgeons. The aim of our study was to provide insight into the long-term clinical results of spinal fusion in congenital scoliosis.

METHODS

We performed a retrospective review of the scoliosis database in our institution for the period 1976 until 2002 identifying 43 patients with congenital scoliosis who underwent spinal fusion. Patient demographics, diagnosis, levels fused, and radiographs were evaluated. Patients were evaluated for unplanned return to the operating room (UPROR) via SRS 22, EQ5D-5L, and Oswestry Disability Index (ODI).

RESULTS

Of the 43 patients who fulfilled the inclusion criteria, 22 patients agreed to participate, 3 patients were known to be deceased and 18 patients were lost to follow-up or declined to participate and were excluded. The mean age of the respondents was 40.7 years (range, 30 to 47 y) with a mean follow-up from index surgery of 35 years (range, 20 to 44 y). At most recent follow-up, 12 patients (54%) underwent UPROR. The mean age at diagnosis was 3.4 years (range, birth to 11.5 y), and the mean age for first surgery was 5.8 years (range, 1 to 13 y). As regards radiologic follow-up; the mean number of levels fused was 5.2 (range, 2 to 12). Thoracic fusion was performed in 17 patients (77%). The mean T1 to T12 height at index surgery and maturity was 166 mm (range, 130 to 240 mm) and 202 mm (range, 125 to 270 mm), respectively. The mean functional scores at follow-up were SRS 22: 4.5 (range, 2.4 to 5), cumulative EQ5D-5L score 7.2 (range, 5 to 15), and ODI: 8% (range, 2 to 30%). All respondents completed high school, 10 patients (45%) completed university, and 2 patients were awarded doctorates. Currently, 17 patients (77%) are in paid employment.

CONCLUSIONS

This report constitutes the largest series of patients treated by spinal arthrodesis for congenital scoliosis followed into maturity. We demonstrate the thorax continues to grow after index fusion, patient-reported outcomes were satisfactory with superior educational and employment rates and unplanned return to theatre is rare in adult life.

LEVEL OF EVIDENCE

Therapeutic Level IV.

Mortality in Early-Onset Scoliosis During the Growth-friendly Surgery Era

INTRODUCTION

Early-onset scoliosis (EOS) is a spinal deformity that occurs in patients 9 years of age or younger. Severe deformity may result in thoracic insufficiency, respiratory failure, and premature death. The purpose of this study is to describe the modern-day natural history of mortality in patients with EOS.

METHODS

The multicenter Pediatric Spine Study Group database was queried for all patients with EOS who are deceased, without exclusion. Demographics, underlying diagnoses, EOS etiology, operative and nonoperative treatments or observation, complications, and date of death were retrieved. Descriptive statistics and survival analysis with Kaplan-Meier curves were performed.

RESULTS

There were 130/8009 patients identified as deceased for a registry mortality rate of 16 per 1000 patients. The mean age at death was 10.6 years (range: 1.0 to 30.2 y) and the most common EOS etiology was neuromuscular (73/130, 56.2%; P<0.001). Deceased patients were more likely be treated operatively than nonoperatively or observed (P<0.001). The mean age of death for patients treated operatively (12.3 y) was older than those treated nonoperatively (7.0 y) or observed (6.3 y) (P<0.001) despite a larger deformity and similar index visit body mass index and ventilation requirements. Kaplan-Meier analysis confirmed an increased survival time in patients with a history of any spine operation compared with patients without a history of spine operation (P<0.0001). Operatively treated patients experienced a median of 3.0 complications from diagnosis to death. Overall, cardiopulmonary related complications were the most common (129/271, 47.6%; P<0.001), followed by implant-related (57/271, 21.0%) and wound-related (26/271, 9.6%). The primary cause of death was identified for 78/130 (60.0%) patients, of which 57/78 (73.1%) were cardiopulmonary related.

CONCLUSIONS

This study represents the largest collection of EOS mortality to date, providing surgeons with a modern-day examination of the effects of surgical intervention to better council patients and families. Both fatal and nonfatal complications in children with EOS are most likely to involve the cardiopulmonary system.

LEVEL OF EVIDENCE

Level IV-therapeutic.

One-Way Self-Expanding Rod in Neuromuscular Scoliosis: Preliminary Results of a Prospective Series of 21 Patients

Fusionless techniques for the treatment of neuromuscular early-onset scoliosis (EOS) are increasingly used to preserve spinal and thoracic growth and to postpone posterior spinal fusion (PSF). These techniques have greatly improved thanks to magnetically controlled growing rods, which allow the avoidance of repeated surgery. However, the surgery-related complication rate remains high. The objective of the current study was to report the preliminary outcomes of 21 patients with neuromuscular EOS who were treated with a 1-way self-expanding rod (OWSER). This device was designed to avoid repeated surgery and preserve spinal and thoracic growth thanks to its free rod sliding.

Surgical Outcome of Spinal Fusion for Osteogenesis Imperfecta With Scoliosis: Is the Hybrid System With Pedicle Screws Applicable to Weak, Tiny, and Fragile Vertebrae?

INTRODUCTION

Corrective surgery for spinal deformity associated with osteogenesis imperfecta (OI) is challenging due to the severe and rigid deformity combined with extreme bone fragility. However, surgical outcomes still remain unclear. In addition, the applicability of pedicle screws (PSs) to the tiny and fragile vertebrae in patients with OI is poorly understood. This study evaluated the surgical outcome, and the accuracy and safety of PS placement in patients with OI.

METHODS

Twenty-five patients with OI were included in this study. Mean age was 21.0±9.3 (10 to 49) years. Mean follow-up was 5.8±2.0 years. The Sillence classification showed 16 patients had the mildest type I, 1 patient had moderate type IV, and 8 patients had the most severe type III. Fifteen patients underwent anterior release followed by posterior fusion, and 10 patients underwent only posterior fusion. The accuracy of PS placement was evaluated with postoperative computed tomography.

RESULTS

Scoliosis was corrected from 95.6 to 65.8 degrees after surgery (correction rate 32.5%) and 68.1 degrees at final follow-up (both, P<0.01). Space available for the lung was improved from 76.3% to 84.9% (P<0.05). No implant dislodgement occurred after surgery. A total of 290 screws were placed, of which 213 screws (73.4%) were placed completely. However, 30 screws (10.3%) penetrated >2 mm. In particular, rates of >2 mm penetration was much higher in type III than type I and IV (27.8% vs. 3.0%; P<0.01). Complications related to spinal surgery included 2 transient neurological disturbances.

CONCLUSIONS

PSs were applicable to spinal fusion surgery in patients with OI. However special care should be taken in placing PSs because of the weakness of the pedicle cortex, which was easily penetrated especially in Sillence type III.

LEVEL OF EVIDENCE

Level IV.

Can distraction-based surgeries achieve minimum 18 cm thoracic height for patients with early onset scoliosis?

PURPOSE

Karol et al. introduced the concept that 18 cm thoracic height is the critical point where a patient with early onset scoliosis (EOS) can maintain adequate pulmonary function. Our purpose was to determine if distraction-based surgeries will increase thoracic spine height to at least 18 cm in patients with EOS.

METHODS

Patients with EOS treated with distraction-based systems (minimum 5 years follow up, minimum five lengthenings). Radiographic analysis of thoracic spine height (T1-T12) at the last lengthening procedure.

RESULTS

One hundred and fifty-three patients (67 congenital, 21 neuromuscular, 38 syndromic, 27 idiopathic) with pre-operative mean age 4.6 years, scoliosis 75°, kyphosis 47° were evaluated. Their mean age at final lengthening procedure was 11 years (6-16), average number of lengthening procedures was 10.5 (4-21), mean final scoliosis was 53°, and mean final kyphosis was 58°. Final thoracic height was > 18 cm in 65% and was > 22 cm in 31% of patients. Based on etiology, only 48% of the congenital patients reached 18 cm compared to 81% neuromuscular, 84% syndromic and 67% idiopathic. This height gain was closely related to the percentage of scoliosis correction achieved for each etiology. Comparing congenital etiology to other etiologies, there was a lower percentage of patients in the congenital group that passed the 18 cm threshold (48% vs. 78%) (p < 0.05).

CONCLUSION

At minimum 5 years follow up, distraction-based surgeries increased thoracic height for patients with EOS to greater than 18 cm in 65% of patients; however, only 48% of congenital patients reached this thoracic height threshold.

DESIGN

Retrospective review of prospectively collected registry data. LOI III.

Congenital lung abnormality quantification by computed tomography: The CLAQ method

INTRODUCTION

To date, no consensus has been reached on the optimal management of congenital lung abnormalities, and factors predicting postnatal outcome have not been identified. We developed an objective quantitative computed tomography (CT) scoring method, and assessed its value for clinical decision-making.

METHODS

Volumetric CT-scans of all patients born with a congenital lung abnormality between January 1999 and 2018 were assessed. Lung disease was quantified using the newly-developed congenital lung abnormality quantification (CLAQ) scoring method. In 20 equidistant axial slices, cells of a square grid were scored according to the abnormality within. The scored CT parameters were used to predict development of symptoms, and SD scores for spirometry and exercise tolerance (Bruce treadmill test) at 8 years of age.

RESULTS

CT-scans of 124 patients with a median age of 5 months were scored. Clinical diagnoses included congenital pulmonary airway malformation (49%), bronchopulmonary sequestration (27%), congenital lobar overinflation (22%), and bronchogenic cyst (1%). Forty-four patients (35%) developed symptoms requiring surgery of whom 28 (22%) patients became symptomatic before a CT-scan was scheduled. Lesional hyperdensity was found as an important predictor of symptom development and decreased exercise tolerance. Using receiver operating characteristic analysis, an optimal cut-off value for developing symptoms was found at 18% total disease.

CONCLUSION

CT-quantification of congenital lung abnormalities using the CLAQ method is an objective and reproducible system to describe congenital lung abnormalities on chest CT. The risk for developing symptoms may increase when more than a single lung lobe is affected.

Image Distortion in Biplanar Slot Scanning: Patient-specific Factors

BACKGROUND

Error within imaging measurements can be due to processing, magnification, measurement performance, or patient-specific factors. Previous length measurement studies based on radiographs have shown good intraclass correlation coefficients (ICCs) on single images; but have not assessed interimage distortion. In our study, "image distortion in biplanar slot scanning: technology-specific factors" we determined that there is minimal image distortion due to the image acquisition when using biplanar slot scanning. In this study, we aim to determine the role of patient-specific factors in image distortion, specifically evaluating interimage distortion.

METHODS

Digital radiographs and biplanar slot scanner images were reviewed in 43 magnetically controlled growing rod (MCGR) patients. Fifty-five postoperative anteroposterior digital radiographs, 184 follow-up biplanar slot-scanner scanner posteroanterior and 76 biplanar slot-scanner scanner laterals were measured by 2 residents and 1 attending. The manufacturer reported average actuator diameter of 9.02 mm was used as our reference width.

RESULTS

Overall, within image interobserver ICC were moderate to excellent (0.635 to 0.983), but the interimage ICCs were poor (0.332). Digital radiographs consistently overestimated the MCGR actuator width (mean=9.655) and biplanar slot-scanner scanner images underestimated it (mean=8.935). The measurement range was large with biplanar slot-scanner scanner posteroanterior (up to 15%) and lateral (22%) measurements and with digital radiographs (39%). Patients with abnormal muscle tone had higher degrees of measurement variability.

CONCLUSIONS

We found that neither biplanar slot scanning nor digital radiography was precise or accurate. Digital radiographs consistently overestimated MCGR actuator width and biplanar slot scanning underestimated it. The poor ICC's within and between image subtypes and large standard error of measurement reflected a magnitude of distortion that needs to be accounted for when using length measurements clinically. Unlike the clinically insignificant error that we noted in our previous study "image distortion in biplanar slot scanning: technology-specific factors" (0.5% to 1.5% of the measurement), the error noted in this study (0.2% to 38.5% of the measurement) has the potential to be clinically significant. Patients who have abnormal muscle tone had larger measurement errors, likely stemming from motion during the slot scanning process.

LEVEL OF EVIDENCE

Level III.

Impact of Thoracic Cage Dimension and Geometry on Cardiopulmonary Function in Patients With Congenital Scoliosis: A Prospective Study

STUDY DESIGN

A prospective study of cardiopulmonary function in patients with congenital scoliosis (CS).

OBJECTIVE

To investigate the relationship of thoracic cage deformity and exercise tolerance in CS patients.

SUMMARY OF BACKGROUND DATA

Congenital thoracic scoliosis and chest deformity lead to restrictive pulmonary dysfunction and in some severe cases cause cardiopulmonary failure. However, it is still unknown the relationship between thoracic deformity and exercise performance.

METHODS

Patients with congenital thoracic spinal deformity were included and had radiological assessment of thoracic cage, pulmonary function testing, and cardiopulmonary exercise testing. Thoracic dimension including height, width, and depth were measured and geometry parameters were calculated. Two-tailed Pearson and Spearman correlation test and linear regression analysis were performed to investigate correlation of radiographic parameters, pulmonary function, and physical capacity.

RESULTS

Sixty patients (41 females and 19 males) were included, with an average age of 18.9 years. Patients with smaller thoracic height (P < 0.001) and width (P < 0.01) and larger depth (P < 0.05) had significantly worse static pulmonary function. In exercise testing, these patients showed significant tendency of ventilation insufficiency, including lower minute ventilation (P < 0.05), faster breathing frequency (P < 0.05), and smaller tidal volume (P < 0.01). Thoracic depth was negatively correlated to exercise capacity, reflected by work rate (P < 0.001), peak oxygen intake (P < 0.001), and heart rate (P = 0.043). Patients with abnormal thoracic geometry, especially a lower ratio of height to depth and a lower ratio of width to depth, have significantly worse static pulmonary function and exercise capacity (all P < 0.05).

CONCLUSION

Decreasing thoracic height and width results in restrictive pulmonary dysfunction. Distortion and asymmetry of the thoracic cage are associated with abnormal breathing pattern and reduction of exercise capacity.

LEVEL OF EVIDENCE

3.

Thoracic proportions in children without scoliosis

PURPOSE

Scoliosis is a condition of abnormal growth resulting in 3D deformity of both the spine and thoracic cage. The aim of this study is to use chest radiographs of healthy children to define normal thoracic proportions so as to provide a useful normal reference range against which children with spinal deformity can be compared.

METHODS

Three independent reviewers assessed posteroanterior and lateral chest radiographs of 184 normal children aged between two and 15 years. Duplicate assessments were undertaken by all three raters on 36 of these radiographs. We measured the T1 to T12 length, sternal length, chest depth at T6, chest width at T3, chest width at T6 and maximum chest width. Ratios of thoracic dimensions were calculated to define the normal proportions of the thorax. Inter- and intra-rater variance was estimated for all dimensions and dimension ratios.

RESULTS

The intra-rater and inter-rater reliability was excellent with intra-class-correlation coefficients values > 80% and both intra- and inter-rater coefficients of variance < 9% for all parameters. All measured dimensions of the thorax and spine progressed linearly with respect to age. The mean proportions of T1 to 12 length of the sternal length, chest depth at T6, chest width at T3, chest width at T6 and maximum chest width were 0.5, 0.4, 0.7, 0.9 and 1.0, respectively.

CONCLUSION

It is possible to accurately and reproducibly measure the dimensions of the thoracic cage and spine on plain film radiology. The ratios of T1 to T12 length with respect to sternal length, chest depth at T6, chest width at T3, chest width at T6 and maximum chest remain constant with increasing age. Thoracic dimensions in children progress linearly with increasing age.

LEVEL OF EVIDENCE

V.

Prediction of respiratory function in patients with severe scoliosis on the basis of the novel individualized spino-pelvic index

OBJECTIVE

Our study aimed to evaluate the pulmonary function of patients with severe scoliosis after correcting standing height with spino-pelvic index (SPI).

METHODS

Inclusion criteria: (1) with a coronal Cobb angle of more than 90°; (2) diagnosed as congenital (CS) or idiopathic scoliosis (IS); (3) aged between ten and 20 years; (4) with pulmonary function test (PFT) at the primary consultation. Patients with previous surgical intervention, with angular kyphosis, and with neuromuscular disease were excluded. Length of spine (LOS), height of spine (HOS), and height of pelvis (HOP) were measured on coronal films. SPI was defined as the ratio between LOS and HOP. The corrected body height was calculated: corrected body height = body height + (SPI × HOP - HOS). The PFTs included the following parameters: VC_max, FVC, FVC% predicted, FEV1, FEV1% predicted, PEF, and MVV. PFT results were recalculated using the corrected body height.

RESULTS

Thirty patients were diagnosed as IS and 27 as CS with average Cobb angles of 99.88° ± 11.83 and 98.06° ± 14.27, respectively. Significant differences were observed in VC_max and FVC between IS and CS patients (P < 0.05). All the corrected PFT parameters were significantly lower than the original PFT parameters (P < 0.05).

CONCLUSION

For the first time, this study proposed a method to predict pulmonary function of patients with severe scoliosis using SPI, as an age-independent parameter in normal adolescents. After body height correction, pulmonary function of patients with severe scoliosis was found to be significantly decreased, indicating that pulmonary function impairment was underestimated in patients with severe scoliosis when evaluating pulmonary function with arm span.

Spine and Thoracic Height Measurements Have Excellent Interrater and Intrarater Reliability in Patients With Early Onset Scoliosis

STUDY DESIGN

Reproducibility of measurements.

OBJECTIVE

This study investigates the reliability and standard error of measurement of spine and thoracic height radiographic measurements in patients with early onset scoliosis (EOS).

SUMMARY OF BACKGROUND DATA

Spine and thoracic height radiographic measurements are often used as a surrogate for pulmonary development in patients with EOS. There is limited literature validating the reliability of spine and thoracic height measurements in the EOS population.

METHODS

Using pilot data, we determined measuring 49 unique radiographs would provide 80% power to obtain a 95% confidence interval (CI) width of 0.05 for the interclass correlation coefficients (ICCs). A random sampling strategy, stratified by underlying diagnosis from the Classification of Early Onset Scoliosis (C-EOS), was used to distribute the diagnoses in the study sample. Two attending pediatric spine surgeons, two pediatric orthopedic fellows, and two research assistants measured coronal spine (T1-S1) and thoracic (T1-T12) height on digital radiographs using imaging software (Surgimap; Nemaris, Inc, New York) on two separate occasions at least 3 weeks apart. Order of images was randomized for the second iteration. Linear mixed model regression analyses were used to estimate interrater and intrarater reliability.

RESULTS

The study sample included subjects (N = 48) with idiopathic (N = 17, 35%), congenital (N = 16, 33%, 1 patient excluded), neuromuscular (N = 11, 23%), and syndromic (N = 4, 8%) scoliosis. Overall interrater reliability estimates for spine height (ICC: 0.894, 95% CI: 0.847-0.932) and thoracic height (ICC: 0.890, 95% CI: 0.844-0.929) were excellent. Intrarater reliability estimates for spine height (ICC: 0.906, 95% CI: 0.830-0.943) and thoracic height (ICC: 0.898, 95% CI: 0.817-0.938) were also excellent.

CONCLUSION

There is excellent interrater and intrarater reliability for radiographic measurements of spine and thoracic height in the EOS population at our institution.

LEVEL OF EVIDENCE

2.

Functional and Radiographic Outcomes Following Growth-Sparing Management of Early-Onset Scoliosis

BACKGROUND

In this study, we sought to evaluate radiographic, functional, and quality-of-life outcomes of patients who have completed growth-sparing management of early-onset scoliosis.

METHODS

This prospective study involved patients with early-onset scoliosis who underwent growth-sparing treatment and either "final" fusion or observation for ≥2 years since the last lengthening procedure. Demographics, radiographic parameters, pulmonary function test (PFT) values, and scores of patient-reported assessments (Early-Onset Scoliosis Questionnaire [EOSQ] and Scoliosis Research Society [SRS]-30) were obtained. At the most recent follow-up, patients performed 2 additional functional outcome tests: step-activity monitoring and a treadmill exercise-tolerance test.

RESULTS

Twelve patients were evaluated as "graduates" of growth-sparing management of early-onset scoliosis (mean of 37 months since the most recent surgery). The major scoliosis curve measurement averaged 88° before treatment and 47° at the most recent follow-up. T1-S1 height increased from a mean of 22.3 cm to 34.7 cm and T1-T12 height, from 13.3 to 22.3 cm. At the most recent follow-up, the mean forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) as a percentage of the predicted volume were 52.1% and 55.3%, respectively, and were essentially unchanged from the earliest PFT that patients could perform (FEV1 = 53.8% of predicted and FVC = 53.5% of predicted). There was no difference between graduates and controls with respect to activity time or total steps in step-activity monitoring, and in the exercise-tolerance test, graduates walked at the same speed but at a higher heart rate and at a significantly higher (p <0.001) VO2 cost (rate of oxygen consumed per distance traveled). The EOSQ mean score was 102.2 of a possible 120 points, and the SRS mean score was 4.1 of a possible 5 points.

CONCLUSIONS

A realistic long-term goal for the management of early-onset scoliosis appears to be spine elongation and maintenance of pulmonary function at a level that is no less than the percentage of normal at initial presentation. Functional testing and patient-reported outcomes at a mean of 3 years from the last surgery suggest that activity levels were generally equal to those of controls but required greater physiologic demand. General health and physical function outcomes revealed continued impairment in these domains.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The effect of growing Rod treatment on coronal balance during serial lengthening surgeries in early onset scoliosis

Background

Gaining and maintaining spinal balance after surgery is of great importance for early onset scoliosis (EOS). However, tendency of balance on the coronal plane after growing rod surgery has not been studied before. This study evaluated the effect of growing rod treatment on coronal balance (CB) during serial lengthening surgeries in EOS.

Methods

All EOS patients treated with growing rod technique in our hospital from August 2002 to June 2014 were retrospectively reviewed. Radiographic data before the sixth lengthening surgery were measured on the posteroanterior X-ray images, including global CB (C7 plumbline-central sacral vertical line, C7PL-CSVL), regional CB (apical vertebrae-CSVL), Cobb angle of the main curve and pelvic inlet width (PIW). Global CB index and regional CB index were calculated as dividing global CB and regional CB by PIW, respectively. The changes of these parameters during repeated lengthening surgeries were analyzed.

Results

Five hundred seventy Radiographs of 67 patients, including 134 images before and after growing rod insertion surgeries and 436 images pre- and post-lengthening surgeries were measured. Global CB and global CB index did not show significant differences between every two set points during lengthening procedures (P > 0.05). The percentage of patients with C7PL-CSVL distance more than 20 mm roughly ranged from 30 to 45 % during the lengthening process. With regards to regional CB and main curve Cobb angles, there were significant differences between every two adjacent set points during the first five lengthening surgeries (P < 0.05).

Conclusions

Global CB did not significantly change during serial lengthening surgeries and C7PL-CSVL distances of greater than 20 mm comprised of over one third of patients during growing rod treatment. However, worsening regional CB and Cobb angles of the main curve during lengthening intervals were corrected by lengthening manipulation and maintained at a stable level.

The effect of vertical expandable prosthetic titanium rib on growth in congenital scoliosis

Aims:

In the treatment of thoracic insufficiency syndrome, the main aim is to maintain spinal and thoracic growth in order to continue respiratory functions. Vertical expandable prosthetic titanium rib (VEPTR) device application is a method of choice especially in the congenital cases with a thoracic deformity. In our study, we evaluated the effect of VEPTR on growth in congenital scoliosis.

Materials and Methods:

Four female patients in whom VEPTR was applied were retrospectively evaluated. Anteroposterior (AP) and lateral Cobb angles that were measured preoperatively and during the last control, space available for lung (SAL), T1-S1 and T1-T12 distances, coronal and sagittal balances were compared.

Results:

Four female patients in whom VEPTR was applied were retrospectively evaluated. AP and lateral Cobb angles that were measured preoperatively and during the last control, SAL, T1-S1, and T1-T12 distances, coronal and sagittal balances were compared.

Conclusions:

VEPTR may provide a good correction, and we observed a growth in the spine height and SAL following the treatment of congenital deformities. Long-term, multicenter, prospective studies that compare the spinal height, respiratory functions, the severity of the deformity, and the spinal balance are required in order to evaluate the efficacy of VEPTR.

Disproportionate growth between the spine and pelvis in patients with thoracic adolescent scoliosis

A self-control ratio, the spine-pelvis index (SPI), was proposed for the assessment of patients with adolescent idiopathic scoliosis (AIS) in this study. The aim was to evaluate the disproportionate growth between the spine and pelvis in these patients using SPI. A total of 64 female patients with thoracic AIS were randomly enrolled between December 2010 and October 2012 (mean age 13 years, standard deviation (sd) 2.17; 9 to 18) and a further 73 healthy female patients with a mean age of 12.4 years (mean age 12.4 years, sd 2.24; 9 to 18), were randomly selected from a normal control database at our centre. The radiographic parameters measured included length of spine (LOS), height of spine (HOS), length of thoracic vertebrae (LOT), height of thoracic vertebrae (HOT), width of pelvis (WOP), height of pelvis (HOP) and width of thorax (WOT). SPI was defined as the ratio LOS/HOP. The SPI and LOT/HOP in patients with AIS showed a significant increase when compared with normal girls (p < 0.001 and p < 0.001 respectively), implying an abnormal pattern of growth of the spine relative to the pelvis in patients with AIS.

No significant difference in SPI was found in different age groups in the control group, making the SPI an age-independent parameter with a mean value of 2.219 (2.164 to 2.239). We also found that the SPI was not related to maturity in the control group.

This study, for the first time, used a self-control ratio to confirm the disproportionate patterns of growth of the spine and pelvis in patients with thoracic AIS, highlighting that the SPI is not affected by age or maturity.

Cite this article: Bone Joint J 2015;97-B:1668–74.

Early-onset scoliosis: current treatment

Early-onset scoliosis, which appears before the age of 10, can be due to congenital vertebral anomalies, neuromuscular diseases, scoliosis-associated syndromes, or idiopathic causes. It can have serious consequences for lung development and significantly reduce the life expectancy compared to adolescent scoliosis. Extended posterior fusion must be avoided to prevent the crankshaft phenomenon, uneven growth of the trunk and especially restrictive lung disease. Conservative (non-surgical) treatment is used first. If this fails, fusionless surgery can be performed to delay the final fusion procedure until the patient is older. The gold standard delaying surgical treatment is the implantation of growing rods as described by Moe and colleagues in the mid-1980s. These rods, which are lengthened during short surgical procedures at regular intervals, curb the scoliosis progression until the patient reaches an age where fusion can be performed. Knowledge of this technique and its complications has led to several mechanical improvements being made, namely use of rods that can be distracted magnetically on an outpatient basis, without the need for anesthesia. Devices based on the same principle have been designed that preferentially attach to the ribs to specifically address chest wall and spine dysplasia. The second category of surgical devices consists of rods used to guide spinal growth that do not require repeated surgical procedures. The third type of fusionless surgical treatment involves slowing the growth of the scoliosis convexity to help reduce the Cobb angle. The indications are constantly changing. Improvements in surgical techniques and greater surgeon experience may help to reduce the number of complications and make this lengthy treatment acceptable to patients and their family. Long-term effects of surgery on the Cobb angle have not been compared to those involving conservative "delaying" treatments. Because the latter has fewer complications associated with it than surgery, it should be the first-line treatment for most cases of early-onset scoliosis.

Computed Tomography Lung Volume Changes After Surgical Treatment for Early-Onset Scoliosis

STUDY DESIGN

Single-center review of prospectively collected data.

OBJECTIVES

To document anatomic lung volume and thoracic parameter changes in early-onset scoliosis patients undergoing rib-based (RB), or spine-based (SB) distraction surgical treatment who were too young to perform pulmonary function tests.

METHODS

Twenty patients undergoing growth-sparing treatment had computed tomography lung volumes (CTvol) determined by controlled-ventilation CT scanning preoperatively and at a mean of 2.7 years later under an institutional review board (IRB)-approved protocol. Twelve patients had non-congenital curves and 8 had congenital curves. Eleven patients had SB constructs and 9 had RB ones. Computed tomography lung volumes were correlated to T1-12 length, T6 coronal width, pelvic width, and curve magnitude, and were normalized by comparison with age standards and pelvic width.

RESULTS

All patients had increased CTvol at follow-up (RB 51%, SB 46%; p < .001). All increased T1-12 length from 128 mm (range, 39-160 mm) preoperatively to 154 mm (range, 61-216 mm) at follow-up. Both RB and SB gained 2.6 cm; this measurement was significant in RB (p < .001) owing to the shorter preoperative length. The T1-12 length correlated well with CTvol preoperatively (p = .002) and at follow-up (p = .007). The T6 width correlated best with CTvol (r = 0.76; p < .001 preoperatively and at follow-up). Main thoracic curves improved 21° in SB (preoperatively, 78°) versus 1.5° correction in RB (preoperatively, 60.2°). There was no correlation between curve magnitude and CTvol preoperatively or at follow-up. Follow-up CTvol percentile decreased in 10 patients, increased in 6, and was unchanged in 4. The T1-12 length was less than the fifth percentile in all patients preoperatively and increased in 9 patients at follow-up, whereas 11 remained at less than the fifth percentile.

CONCLUSIONS

The CTvol quantitates anatomic results of early-onset scoliosis growth-sparing surgery in patients too young for standard pulmonary function tests. Thoracic length and width correlate well with absolute CTvol and are possible surrogate measures. Curve magnitude and correction correlate poorly and assume less importance in outcome evaluation. Thoracic volume and length gains exceeded normal growth in about half of the patients.

Is there a relationship between thoracic dimensions and pulmonary function in early-onset scoliosis?

STUDY DESIGN

Cross-sectional retrospective analysis.

OBJECTIVE

To examine the degree of correlation between thoracic dimension outcome measures and pulmonary function in early-onset scoliosis (EOS).

SUMMARY OF BACKGROUND DATA

Change in thoracic dimension (TD) measurements and spine length are commonly reported outcome measures after treatment for EOS. Although ultimately improving or maintaining pulmonary function is the goal of EOS treatment strategies, it is unclear whether commonly reported 2-dimensional TD measurements represent good predictors of pulmonary function.

METHODS

A cross-sectional analysis of patients including all diagnoses obtained from 2 EOS databases containing TD measurements and pulmonary function data was performed. Relationships between individual TD measurements and pulmonary function measurements were assessed using the Pearson correlation analysis. TD measurements (pelvic inlet width, T1-T12 height, T1-S1 height, and coronal chest width) and standard pulmonary function measurements were compared. TD percentiles normalized for pelvic inlet width were also calculated and correlated with pulmonary function measurement percentiles. Univariate and multivariate linear regression analyses determined whether TD measurements could predict pulmonary function.

RESULTS

There were 121 patients (65 females, 56 males) in the study. Mean age at evaluation was 9.3 years (range, 2.7-18.1 yr). T1-T12 height, T1-S1 height, maximal chest width, and pelvic inlet width were all significantly correlated with forced air volume expelled in 1 second, total forced air volume, and total lung capacity (correlation coefficients [r] 0.33-0.61; all P<0.001). T1-T12 predicted percentile (normalized for pelvic width) was significantly correlated with forced air volume expelled in 1 second and total forced air volume predicted percentiles (r=0.32, P<0.001 and r=0.27, P=0.004, respectively). Regression analysis determined that T1-T12 percentile was a significant predictor of forced air volume expelled in 1 second percentile and total forced air volume percentiles. Regression analysis found no predictive factors of total lung capacity percentile.

CONCLUSION

Traditional 2-dimensional TD measurements (T1-T12 height) used to measure outcomes in EOS can be used as weak predictors of pulmonary function outcome. However, better outcome measures need to be developed, such as 3-dimensional and dynamic measurements.

LEVEL OF EVIDENCE

3.

Distraction-Based Treatment Maintains Predicted Thoracic Dimensions in Early-Onset Scoliosis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Examination of distraction-based treatment effect on thoracic dimensions in patients compared to predicted individual normal values, at initial treatment and subsequent follow-up after lengthenings.

SUMMARY OF BACKGROUND DATA

Change in thoracic dimensions and spine length is an important outcome measure in treatment of children with early-onset scoliosis; however, it is difficult to use to make comparisons between patients and the normal population because of the heterogeneous nature of early-onset scoliosis.

METHODS

Early-onset scoliosis patients treated with distraction-based therapy who had radiographic parameters (pelvic inlet width, chest width, and thoracic height) preoperatively, immediately postoperatively, and at a minimum 5-year follow-up were included. Individual thoracic measurements were compared with predicted normal measures based on pelvic inlet width, and expressed as a percentile of predicted measure.

RESULTS

Comparisons were made in 41 patients; mean age at time of primary surgery was 4.5 years, and median follow-up was 6.5 years. Thoracic height percentile increased from a mean preoperative value of .78 to a postoperative percentile of .88 (p < .001); at long-term follow-up, it was .85. Absolute thoracic height increased at all 3 time points: 141.6, 159.79, and 203.45 mm, respectively Mean chest width was similar preoperatively (170 mm) and immediately postoperatively (166.5 mm) but increased at latest follow-up (206.9 mm). Chest width percentile was similar at all 3 times (.93, .90, and .91).

CONCLUSIONS

Distraction-based treatment increases absolute thoracic height over time. There is significant improvement in the thoracic height percentile normalized after initial surgery, which was maintained over time. Measuring expected gains as a percentile normalized for pelvic width may be a more relevant outcome measure compared with measuring only absolute values.

Prediction of thoracic dimensions and spine length on the basis of individual pelvic dimensions: validation of the use of pelvic inlet width obtained by radiographs compared with computed tomography

STUDY DESIGN

Retrospective review.

OBJECTIVE

To validate the pelvic inlet width (PIW) measurement obtained on radiograph as an independent standard used to correlate with thoracic dimensions (TDs) in treated and untreated patients with early-onset scoliosis.

SUMMARY OF BACKGROUND DATA

In children with early-onset scoliosis, the change in TD and spine length is a key treatment goal. Quantifying this change is confounded by varied growth rates and differing diagnoses. PIW measured on computed tomographic (CT) scan in patients without scoliosis has been shown to correlate with TD in an age-independent manner.

METHODS

The first arm included 49 patients with scoliosis who had both a CT scan and pelvic radiograph. Agreement between PIW measurements on CT scan and radiograph was analyzed. The second arm consisted of 163 patients (age, 0.2-18.7 yr), with minimal spinal deformity (mean Cobb, 9.0°) and radiographs in which PIW was measurable. PIW was compared with previously published CT-based TD measurements; maximal chest width, T1-T12 height, and T1-S1 height. Linear regression analysis was used to develop and validate sex-specific predictive equations for each TD measurement on the basis of PIW. Interobserver reliability was evaluated for all measurements.

RESULTS

Bland-Altman analysis indicated agreement with no dependence on observed value, but a consistent 8.5 mm (95% CI: 7.2-9.9 mm) difference in CT scan measurement compared with radiographical PIW measurement. Sex and PIW were significantly correlated to each TD measurement (P < 0.01). Predictive models were validated and may be used to estimate TD measurements on the basis of sex and radiographical PIW. Intraclass correlation coefficients for all measurements were between 0.978 and 0.997.

CONCLUSION

PIW on radiographs and CT scan correlate in patients with deformity and with spine and TD in patients with minimal deformity. It is a fast, reliable method of assessing growth while lowering patient's radiation exposure. It can be reliably used to assess patients with early-onset scoliosis and the impact surgical treatment has on chest and spinal growth.

LEVEL OF EVIDENCE

3.

The growing spine: how spinal deformities influence normal spine and thoracic cage growth

PURPOSE

This article aims to provide an overview of how spinal deformities can alter normal spine and thoracic cage growth.

METHODS

Some of the data presented in this article are gathered from studies performed in 1980 and 1990, and their applicability to populations of different ethnicity, geography or developmental stage has not yet been elucidated. In the present article, older concepts have been integrated with newer scientific data available to give the reader the basis for a better understanding of both normal and abnormal spine and thoracic cage growth.

RESULTS

A thorough analysis of different parameters, such as weight, standing and sitting height, body mass index, thoracic perimeter, arm span, T1-S1 spinal segment length, and respiratory function, help the surgeon to choose the best treatment modality. Respiratory problems can develop after a precocious vertebral arthrodesis or as a consequence of pre-existing severe vertebral deformities and can vary in patterns and timing, according to the existing degree of deformity. The varying extent of an experimental arthrodesis also affects differently both growth and thoracopulmonary function.

CONCLUSIONS

Growth is a succession of acceleration and deceleration phases and a perfect knowledge of normal growth parameters is mandatory to understand the pathologic modifications induced on a growing spine by an early onset spinal deformity. The challenges associated with the growing spine for the surgeon include preservation of the thoracic spine, thoracic cage, and lung growth without reducing spinal motion.

Preoperative medical and surgical planning for early onset scoliosis

STUDY DESIGN

A review of current medical and surgical preoperative planning knowledge and protocols for children with early-onset scoliosis (EOS; onset less than 5 years of age).

OBJECTIVE

To describe the preoperative planning process to undertake safe and effective treatment for the EOS patient.

SUMMARY OF BACKGROUND DATA

Children with EOS present with a myriad of medical and orthopedic conditions associated with their specific diagnosis, and frequently require intensive preoperative evaluation and nutritional, pulmonary, and other support to prepare them for safe and effective treatment of the spinal/chest wall deformity. Such patients are among the most difficult and complex to treat effectively.

METHODS

A literature review of known conditions associated with EOS, and a summary of current surgical techniques to maintain deformity control while promoting spine and thoracic growth, was undertaken. Current recommendations for preoperative support and postoperative management of these complex patients are summarized, drawn from the experiences of the author and members of study groups focusing on EOS.

RESULTS

Preoperative assessment of respiratory function, potential for respiratory failure, and determination of objective criteria to indicate surgical management (deformity progression, lack of growth of spine and/or thoracic volume, lack of weight gain) are weighed against the potential for development of thoracic insufficiency syndrome. Magnetic resonance imaging evaluation for neuraxis abnormalities is considered on the basis of diagnosis. Nutritional status, osteopenia, and airway management are evaluated to minimize postoperative complications. Current general recommendations for implants and constructs for specific deformities are reviewed.

CONCLUSION

Thorough preoperative evaluation of EOS patients provides the surgeon with the knowledge to produce a sound surgical plan for this difficult and complex to treat patient population.

Comparison of the immature sheep spine and the growing human spine: a spondylometric database for growth modulating research

STUDY DESIGN

A comparative study on growth of the sheep and human spine.

OBJECTIVE

To validate the immature sheep spine as model for the growing human spine and to yield a database for planning and interpretation of future animal experiments.

SUMMARY OF BACKGROUND DATA

With the current change of paradigm to nonfusion strategies for pediatric spine deformities, experimental surgery on spines of growing goats, sheep, and pigs has gained importance as preclinical proof-of-concept test. However, despite the proceeding use of animals, there is a lack of knowledge regarding the growth of the sheep spine and the relation to the human spine.

METHODS

Thoracic and lumbar cadaver spines were harvested from 50 Swiss alpine sheep. Specimens were obtained from newborn, 1, 3, 6, 9 and 12, 15 and 18 months old female sheep. Direct spondylometry yielded vertebral body heights, widths, and depths and spinal canal size, which were compared to pooled data on human spine growth retrieved from the literature.

RESULTS

Sheep spine growth ceases at age 15 to 18 months, which corresponds to a time-lapse model of human growth. Main growth occurs within the first 3 to 6 months of life, as opposed to human spines with maximal growth during the first 4 years and puberty. The relation between sheep and human vertebral shape is continuously changing with growth: at birth, sheep vertebrae are twice as tall, but equally wide and deep. At skeletal maturity, height is 15% to 25% bigger in sheep, but width 15% to 30% and depth 30% to 50% are smaller.

CONCLUSION

The immature sheep spine offers fast effects if growth-modulating interventions are performed within the first 3 to 6 months of age. The differences in vertebral shapes and further distinctions between human and sheep spines such as biomechanics, facet anatomy, and rib cage morphology have to be considered when interpreting results after experimental surgery.

Dorsal arthrodesis in prepubertal New Zealand white rabbits followed to skeletal maturity: Effect on thoracic dimensions, spine growth and neural elements

BACKGROUND

Several studies have shown that severe spinal deformity and early arthrodesis can adversely affect the development of the spine and thorax by changing their shape and reducing their normal function. This article analyzes the consequences of posterior fusion on the growth of spine, thorax and neural elements in New Zealand white rabbits and compares with similar human data.

MATERIALS AND METHODS

The first section of the article analyzes the consequences of T1-T6 dorsal arthrodesis on the growth of the spine, sternum, thorax volume and neural elements in 12 prepubertal female New Zealand white rabbits, through a study of CT scans and histology specimens. The second part, evaluates thoracic dimensions in 21 children with spinal arthrodesis for treatment of deformity performed prior to nine years of age.

RESULTS

Dorsal arthrodesis in prepubertal rabbits changes thoracic growth patterns. In operated rabbits thoracic depth grows more slowly than thoracic width. The sternum as well as length of thoracic vertebral bodies in the spinal segment T1-T6 show reduced growth. Children undergoing spinal arthrodesis before nine years of age were noted to have shortened height, short trunk and disproportionate body habitus at skeletal maturity. Observed spine height and chest dimension values were reduced compared to the expected norms. The ratio between chest width and chest depth was below normal values.

CONCLUSIONS

The first part of the study shows that thoracic dorsal arthrodesis in prepubertal New Zealand white rabbit influences thoracic, spine growth and affects the shape of pseudo unipolar neurons of the dorsal root ganglia. The second part demonstrates that children treated before nine years of age have significantly reduced spine height and thoracic dimensions. The thorax becomes elliptical as chest depth grows less than chest width. Both experimental and clinical findings contribute to explain reduced chest growth and subsequent thoracic growth disturbance in patients treated with early arthrodesis.

Pathogenesis of adolescent idiopathic scoliosis in girls - a double neuro-osseous theory involving disharmony between two nervous systems, somatic and autonomic expressed in the spine and trunk: possible dependency on sympathetic nervous system and hormones with implications for medical therapy

Anthropometric data from three groups of adolescent girls - preoperative adolescent idiopathic scoliosis (AIS), screened for scoliosis and normals were analysed by comparing skeletal data between higher and lower body mass index subsets. Unexpected findings for each of skeletal maturation, asymmetries and overgrowth are not explained by prevailing theories of AIS pathogenesis. A speculative pathogenetic theory for girls is formulated after surveying evidence including: (1) the thoracospinal concept for right thoracic AIS in girls; (2) the new neuroskeletal biology relating the sympathetic nervous system to bone formation/resorption and bone growth; (3) white adipose tissue storing triglycerides and the adiposity hormone leptin which functions as satiety hormone and sentinel of energy balance to the hypothalamus for long-term adiposity; and (4) central leptin resistance in obesity and possibly in healthy females. The new theory states that AIS in girls results from developmental disharmony expressed in spine and trunk between autonomic and somatic nervous systems. The autonomic component of this double neuro-osseous theory for AIS pathogenesis in girls involves selectively increased sensitivity of the hypothalamus to circulating leptin (genetically-determined up-regulation possibly involving inhibitory or sensitizing intracellular molecules, such as SOC3, PTP-1B and SH2B1 respectively), with asymmetry as an adverse response (hormesis); this asymmetry is routed bilaterally via the sympathetic nervous system to the growing axial skeleton where it may initiate the scoliosis deformity (leptin-hypothalamic-sympathetic nervous system concept = LHS concept). In some younger preoperative AIS girls, the hypothalamic up-regulation to circulating leptin also involves the somatotropic (growth hormone/IGF) axis which exaggerates the sympathetically-induced asymmetric skeletal effects and contributes to curve progression, a concept with therapeutic implications. In the somatic nervous system, dysfunction of a postural mechanism involving the CNS body schema fails to control, or may induce, the spinal deformity of AIS in girls (escalator concept). Biomechanical factors affecting ribs and/or vertebrae and spinal cord during growth may localize AIS to the thoracic spine and contribute to sagittal spinal shape alterations. The developmental disharmony in spine and trunk is compounded by any osteopenia, biomechanical spinal growth modulation, disc degeneration and platelet calmodulin dysfunction. Methods for testing the theory are outlined. Implications are discussed for neuroendocrine dysfunctions, osteopontin, sympathoactivation, medical therapy, Rett and Prader-Willi syndromes, infantile idiopathic scoliosis, and human evolution. AIS pathogenesis in girls is predicated on two putative normal mechanisms involved in trunk growth, each acquired in evolution and unique to humans.

Does early thoracic fusion exacerbate preexisting restrictive lung disease in congenital scoliosis patients?

BACKGROUND

Congenital thoracic scoliosis is associated with diminished pulmonary function. Early posterior thoracic spinal fusion surgery may additionally impact pulmonary function beyond the natural history of the disease by further inhibiting thoracic growth. The primary study aim is to determine if early thoracic spine fusion patients have diminished pulmonary function versus untreated patients at a similar age. The secondary study aim is to determine how plain radiographic measurements of thoracic deformity change over time and correlate to pulmonary function in these patients.

METHODS

Sequential spinal radiographs and one-time pulmonary function tests were performed in 43 consecutive congenital thoracic scoliosis patients with either a history of early posterior thoracic fusion or no surgery. Multiple stepwise t testing compared the patient-related and radiographic variables in the early surgery and no surgery groups. Multiple stepwise linear regression analysis examined the effect of the variables at final follow-up on forced vital capacity and forced expiratory volume.

RESULTS

All patients exhibited decreased forced vital capacity, but there was no difference between early surgery and no surgery groups at an average follow-up age of 10.5 years. A mid- (versus low) thoracic apex, decreased space available for the lung, and decreased age-corrected thoracic width correlated with decreased forced vital capacity. Between initial and final radiographic follow-up, the rate of change in thoracic height and width was decreased in the early surgery versus no surgery group.

CONCLUSIONS

Early posterior spinal fusion decreases radiographic measures of thoracic growth over time, but pulmonary function was similar to untreated patients at 10.5 years of age. The data suggest pulmonary function and thoracic size as measured on plain radiographs correlate directly. Therefore, pulmonary function testing at the end of growth should be performed to determine the ultimate pulmonary consequences of early surgery.

Developing outcome measures for pediatric deformity surgery

STUDY DESIGN

: Review article regarding the development of outcome measures for pediatric spinal deformity.

OBJECTIVE

: To discuss the role of patient-based outcomes and process measures in pediatric spinal deformity patients.

SUMMARY OF BACKGROUND DATA

: A number of health-related quality of life (HRQOL) questionnaires assess, from patients' perspectives, the effectiveness of spinal deformity correction. The SRS instrument is the most prominent HRQOL tool used in North American adolescent scoliosis studies today. However, these patient-based outcomes and perceptions do not necessarily correlate with process measurements, particularly in the area of increase spinal deformity correction being achieved with newer, more powerful, pedicle screw instrumentation. Furthermore, spinal deformity presenting during infancy or early childhood poses a particular challenge for developing useful evidence-based outcomes tools.

METHODS

: The rationale for patient-based outcome development in pediatric spinal deformity is discussed, along with its important association with process measures.

RESULTS

: Newer HRQOL tools are under development that may better recognize and differentiate changes in adolescent patients' appearances before and after surgery. For early-onset spinal deformity patients, newer process measures for periodic outcome assessment, such as volume measurement of lung parenchyma and spine/chest cage measurement, are being developed.

CONCLUSION

: Ultimately, both patient and process measures are necessary to fully evaluate the results of pediatric spinal deformity surgery.

A segmental radiological study of the spine and rib--cage in children with progressive infantile idiopathic scoliosis

BACKGROUND

The role of rib cage in the development of progressive infantile idiopathic scoliosis (IIS) has not been studied previously. No report was found for rib growth in children with IIS. These findings caused us to undertake a segmental radiological study of the spine and rib-cage in children with progressive IIS. The aim of the present study is to present a new method for assessing the thoracic shape in scoliotics and in control subjects and to compare the findings between the two groups.

MATERIALS AND METHODS

In the posteroanterior (PA) spinal radiographs of 24 patients with progressive IIS, with a mean age of 4.1 years old, the Thoracic Ratios (TRs) (segmental convex and concave TRs), the Cobb angle, the segmental vertebral rotation and vertebral tilt were measured. In 233 subjects, with a mean age of 5.1 years old, who were used as a control group, the segmental left and right TRs and the total width of the chest (left plus right TRs) were measured in PA chest radiographs. Statistical analysis included Mann-Whitney, Spearman correlation coefficient, multiple linear regression analysis and ANOVA.

RESULTS

The comparison shows that the scoliotic thorax is significantly narrower than that of the controls at all spinal levels. The upper chest in IIS is funnel-shaped and the vertebral rotation at T4 early in management correlates significantly with the apical vertebral rotation at follow up.

CONCLUSION

The IIS thorax is narrower than that of the controls, the upper chest is funnel-shaped and there is a predictive value of vertebral rotation at the upper limit of the thoracic curve of IIS, which reflects, impaired rib control of spinal rotation possibly due to neuromuscular factors, which contribute also to the funnel-shaped chest.