Pectus excavatum (PE) is the most frequently observed congenital deformity of the chest which is characterized, in most cases, by a deep depression of the sternum in the anterior thoracic wall. There is a high percentage of scoliosis associated with PE [
Up to now, no comprehensive analysis about the impact that PE has on scoliosis has been performed, although precious research has involved correlation among scoliosis, age, and severity of PE [
The selection of patients was performed by referring to radiographic or computed tomographic images collected preoperatively. From patients of PE who underwent the Nuss procedure at the Military General Hospital of Beijing PLA from February 2009 to March 2014, a total of 37 patients (22 males and 15 females) with an asymmetry of the thorax and a mild to moderate deformity of the spine (with a Cobb angle ≤30°) were selected, and we excluded patients having platy thorax and barrel chest. The patients were between the age of 4 and 44 in this study.
In this study, spiral computerized tomography scan was employed and preoperative CT scans of 37 patients were collected and saved in Digital Imagine and Communication in Medicine (DICOM) format. Then, the preoperative CT images were inputted into the medical image 3D reconstruction software Mimics10.01 (Materialise, Belgium), in which all radiological measurements were conducted.
Cobb angle was defined as a coronal plane deformity on anteroposterior plain radiographs to describe scoliosis. As a general rule, a Cobb angle of 10° is the minimum angulation for scoliosis.
Haller index (HI) was created in 1987 by Drs. Haller, Kramer, and Lietman [
Demonstration of measurements made using Mimics on computer. The Haller index is calculated by T/A and asymmetry index by R/L
For the analysis and investigation of the degree and different types of asymmetric deformity of the chest, symmetry index (SI) and sternal rotation angle have been widely used [
The sternal torsion angle (STA) against the horizontal line was measured. The right-side depression of the chest wall, which indicates the counter clockwise twist of the sternum, is expressed as positive (Figure
In addition, to investigate the degree of asymmetric deformity of PE in the horizontal direction, offset coefficient (OC) was defined to describe the excursion degree of the center of PE apex (Figure
Demonstration of measurements using Mimics on computer. Offset coefficient calculated by A/B
37 patients were divided into two age groups preoperatively—the child group (
According to the severity of PE, 37 patients were divided into two Haller index groups preoperatively—the mild group (
37 patients were divided into 2 offset coefficient groups: the mild group (
37 patients were divided into 2 sternal torsion angle groups: the mild group (
For statistical calculations, SPSS Version 20.0 for Windows (SPSS Inc., IBM Company, Chicago, IL) was used.
This study has obtained approval by the school of mechanical engineering, Tianjin University of Technology and Military General Hospital of Beijing PLA. There is no conflict of interest to be declared.
The results of the scoliosis incidence in the age groups were shown in Table
Age distribution of patients with a Cobb angle greater than 10°.
Child group |
Adult group |
|
|
---|---|---|---|
Scoliosis case (100%) | 8 (53.33%) | 20 (90.91%) | 0.017 < 0.05 |
Further statistics (
Cobb angles of the two age groups. Significant difference was found between the child and adult groups (
In this study, the incidence of scoliosis in the adult group was 90.91% (Table
With regard to the severity of the PE, 25 (89.29%) of the 28 scoliosis patients (
Haller index distribution of patients with a Cobb angle greater than 10°.
Mild group |
Severe group HI ≥ 3.5 ( |
|
|
---|---|---|---|
Scoliosis case (100%) | 3 (60%) | 25 (78.13%) | 0.105 > 0.05 |
Further statistics (
In this study, the incidence and the severity of scoliosis have nothing to do with the Haller index of PE. In the view of mechanics principle, the severity of PE described in the form of Haller index has no impact on the internal force exerted on the thoracic cage, except on the depth of the concavity. It cannot break the balance between PE and the spine. So, it cannot change the incidence and the severity of scoliosis.
The results of the scoliosis incidence in offset coefficient groups were shown in Table
Offset coefficient distribution of patients with a Cobb angle greater than 10°.
Mild OC group OC ≤ 10 ( |
Severe OC group OC > 10 ( |
|
|
---|---|---|---|
Scoliosis case (100%) | 5 (66.67%) | 23 (76.67%) | 1.000 > 0.05 |
Further statistics (
Offset coefficient describes the excursion degree of PE apex in the horizontal direction, which represents the horizontal parameter of the PE position. Different offset coefficients contribute nothing to the generation and change of the horizontal internal force which is exerted to the spine. So, it can not have any effect on the incidence and severity of scoliosis.
The cases of vertical position distribution of PE in the high group (
Vertical position distribution of pectus excavatum of patients with a Cobb angle greater than 10°.
High group |
Low group |
|
|
---|---|---|---|
Scoliosis case (100%) | 16 (88.89%) | 12 (63.16%) | 1.000 > 0.05 |
The results of the scoliosis direction in different vertical position of PE group were shown in Table
Vertical position distribution of patients with different scoliosis directions.
High group |
Low group |
|
|
---|---|---|---|
Scoliosis bent to the right (100%) | 13 (72.22%) | 7 (36.84%) | 0.027 < 0.05 |
Scoliosis bent to the left (100%) | 3 (16.67%) | 5 (26.32%) | |
No scoliosis | 2 (11.11%) | 7 (36.84%) |
Vertical position distribution describes the parameter in the vertical direction of PE, and it does not change the horizontal internal force which can make the thoracic vertebra stable in the horizontal direction. So, it has nothing to do with the incidence and the severity of scoliosis. But different vertical positions can affect the direction of scoliosis. We noticed that scoliosis is almost located at the same horizontal level with PE (Figures
Distribution of the scoliosis vertical position in 37 patients in the form of thoracic vertebra number.
Distribution of the PE vertical position in 37 patients in the form of thoracic vertebra number.
The results of the scoliosis incidence in two sternal torsion angle groups were shown in Table
Sternal torsion angle distribution of pectus excavatum of patients with a Cobb angle greater than 10°.
Mild group |
Severe group |
|
|
---|---|---|---|
Scoliosis case (100%) | 11 (64.71%) | 17 (85.00%) | 0.251 > 0.05 |
Further statistics (
The results of the scoliosis incidence in the two symmetric index groups were shown in Table
Asymmetric index distribution of pectus excavatum of patients with a Cobb angle greater than 10°.
Mild group |
Severe group |
|
|
---|---|---|---|
Scoliosis case (100%) | 19 (86.36%) | 9 (60.00%) | 0.118 > 0.05 |
Further statistics (
Sternal torsion angle and symmetric index describe the asymmetric degree of the chest, and they do not correlate with the incidence and severity of scoliosis because they cannot break the balance of the horizontal internal force between PE and scoliosis. Hence, they devote nothing to the generation and change of the horizontal internal force and have no effect on the incidence and severity of scoliosis.
The incidence and severity of scoliosis in PE patients with scoliosis correlate with age. The scoliosis will aggravate with the increase of age, which suggests that once the scoliosis is diagnosed, treatment should be conducted as soon as possible.
The incidence and severity of scoliosis do not correlate with the Haller index, offset coefficient, vertical position of pectus excavatum, asymmetric index, and sternal torsion angle, which means that the severity of pectus excavatum and the horizontal and vertical positions of pectus excavatum have nothing to do with the geometric parameters of PE and do not have any effects on the incidence and severity of scoliosis. Namely, three-dimensional positional parameters and the symmetry of pectus excavatum in the human chest have no impact on scoliosis.
The heart may provide an asymmetric horizontal force to push the spines to the right, which means the mechanical factor may be the pathogenesis in pectus excavatum patients with scoliosis.
Pectus excavatum
Computed tomography
Digital Imaging and Communications in Medicine
Haller index
Offset coefficient
Sternal torsion angle
Asymmetric index.
The authors declare that they have no competing interests.
WeiHong Zhong sorted the data and wrote the manuscript. JiFu Liu led and performed all the surgeries. Other authors collected and sorted the data. All authors read and approved the final manuscript.
This study was supported by the National Nature Science Foundation of China (11372221, 11432016, and 11402172).