Ann Thorac Surg 2005;80:2057-2062
© 2005 The Society of Thoracic Surgeons
Original article: General thoracic
Tracheal Compression Caused by Straight Back Syndrome, Chest Wall Deformity, and Anterior Spinal Displacement: Techniques for Relief
Hermes C. Grillo, MD
a
,
*
,
Cameron D. Wright, MD
a
,
Philippe G. Dartevelle, MD
b
,
John C. Wain, MD
a
,
Shinya Murakami, MD
b
a Division of General Thoracic Surgery, Massachusetts General Hospital, and the Department of Surgery, Harvard Medical School, Boston, Massachusetts
b Service for Thoracic and Vascular Surgery and Heart-Lung Transplantation, Marie-Lannelongue Hospital, Paris-Sud University, Le Plessis Robinson, France
Accepted for publication May 11, 2005.
* Address correspondence to Dr Grillo, Blake 1570, Massachusetts General Hospital, 55 Fruit St, Boston, MA02114 (Email: pguerriero{at}partners.org).
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Abstract
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BACKGROUND: Straight back syndrome and other causes of extreme narrowing of the space between sternal notch and vertebrae can cause critical tracheal obstruction. Additional points of compression may result from the brachiocephalic artery and from anterior vertebral displacement.
METHODS: Individualized surgical maneuvers are necessary to correct all points of obstruction. Techniques include sternoplasty, sternal division, reimplantation of brachiocephalic artery, correction of severe pectus excavatum, and posterior wall tracheoplasty.
RESULTS: Four patients were successfully treated by individualized techniques with complete long-term relief of critical tracheal obstruction.
CONCLUSIONS: Severe tracheal compression caused by straight back syndrome and other causes of narrowed sternospinal channel is surgically correctable.
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Introduction
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Straight back syndrome is a rare congenital presentation of a vertical cervical and thoracic vertebral spine that lacks normal dorsal curvature and that is sometimes accompanied by a degree of pectus excavatum (Fig 1) [1]. The distance between the posterior aspect of the manubrium sterni and the vertebral spine is usually markedly reduced (Fig 2). Rarely the trachea may be compressed at this point sufficiently to produce marked dyspnea [2]. Additional points of tracheal compression may result from insufficient substernal space for the brachiocephalic artery as it crosses the trachea, and also from splaying of the lower trachea against the vertebral bodies. Other chest wall deformities may similarly compress the trachea against the vertebral column [3, 4]. Restrictive ventilatory defects may also be present, but patients with straight back deformity do not commonly exhibit respiratory complaints [5].
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Fig 1. Straight back syndrome, patient 1. (A) Lateral view shows the narrowness of the patient's chest, and a spine lacking normal curvatures. Mild pectus excavatum is present but not seen. (B) Posterior view. Normal dorsal kyphosis of the vertebral column is absent.
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Fig 2. Chest roentgenogram, patient 1. (A) The flattened trachea appears broad and widens distally even more. (B) Lateral roentgenogram emphasizes the straight vertebral column. Note the narrowness of the thorax.
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Cardiac signs or symptoms are observed in some patients with straight back syndrome. Palpitations and chest pain may be noted, and a systolic murmur may be heard. The heart may be displaced to the left and "pancaked," and so appear enlarged [1, 5–8]. Mitral valve prolapse may be present. Pulmonary hypertension during exercise, secondary to elevated pulmonary venous pressure, may result from compression of the left pulmonary vein against the aorta and the left atrium against the spine [9].
Components causing tracheal compression appear to vary in the few patients who have been seen with symptoms severe enough to require mechanical relief. A variety of corrective surgical techniques have been applied with success in 4 patients. Although no single surgical solution is obviously applicable to each variant, or seems uniformly superior, description of these patients and the successful solutions devised may serve as a guide when such rare problems are encountered.
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Patients and Methods
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Patient 1
A 21-year-old male student had a long history of respiratory problems, believed at first to be asthma. Respiratory infections required several hospitalizations each year. He was found to have decreased anteroposterior diameter of the chest with narrowing of the trachea. He had a mild pectus excavatum. In 1991, his forced expiratory volume in 1 second (FEV1) was 1.66 L (37% predicted). Radiologic diagnosis of straight back syndrome was made. He declined extensive vertebral and costal surgery as had been recommended elsewhere.
During the next 3 years, his respiratory distress worsened steadily and inspiratory and expiratory stridor became prominent. With rapid progression of symptoms for 2 months, he required emergency intubation to relieve airway obstruction. He was transferred intubated.
Inspiratory and expiratory chest computed tomographic (CT) scans (extubated) and bronchoscopy delineated three points of tracheal compression: (1) anteroposterior compression at the thoracic inlet, (2) similar but eccentric compression by a prominent brachiocephalic artery, and (3) flattening and splaying of the distal trachea over the vertebral bodies (Fig 3). At the thoracic inlet the distance between sternum and spine was 1.5 cm. The Haller index (the ratio of transverse internal thoracic diameter to anteroposterior distance between sternum and vertebrae) was 10.8:1. Normal is less than 3.25. The proximal right and left main bronchi were also flattened on bronchoscopy. His FEV1 was now 1.39 L (31%), his vital capacity was 1.78 L (34%), his FEV1 to forced vital capacity ratio was 0.78, his peak expiratory flow rate was 4.6 L/s, and his maximum breathing capacity was 56 L/min.
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Fig 3. Straight back syndrome, patient 1. (A) Computed tomographic scan at the thoracic inlet. The trachea is flattened to a slit between the manubrium sterni (and also by the brachiocephalic artery) and the vertebral column. Haller's "pectus index" (ratio of transverse internal diameter of the thorax to anteroposterior distance between sternum and vertebra, measured on computed tomographic scan) is 10.8:1 in this patient. Normal is less than 3.25. In Haller's 13- to 18-year-old group of patients selected for pectus repair, the maximum indices were about 5:1 (Haller JA Jr, Kramer SS, Lietman SA. Use of CT scans in selection of patients for pectus excavatum surgery: a preliminary report. J Pediatr Surg 1987;22:904–6). (B) The distal trachea is splayed against the vertebral column, with a widened membranous wall.
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The pectus excavatum defect was so slight that its correction would not have relieved the points of compression listed.
The operation (H.C.G., C.D.W.) was performed through a curved transverse incision over the mid-manubrium, with a vertical extension down over the sternum (Fig 4a). The upper sternum was removed to the second interspace, after reflection of the pectoralis major muscles. Short medial segments of both clavicles and of the first two costal cartilages were excised. The upper half of the manubrium, with its posterior protuberance that was pressing on the trachea, was removed, and the lower half was divided coronally to thin it (Fig 4b). This plate of sternum was later replaced (Fig 4c).
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Fig 4. Surgical correction of tracheal obstruction caused by severe straight back syndrome, with mild pectus excavatum. (a) Diagram of incision, patient 1. In patient 2 the curved incision alone was made to suffice by moving it further caudad for cosmetic reasons. (b) Sagittal diagram illustrating points of tracheal compression. The tracheal lumen is diagrammed at the right of each point of obstruction. The proximal sternum squeezes the trachea against the vertical vertebral column. Note the minimal distance between the sternum and the vertebrae. The brachiocephalic artery compresses the trachea similarly. The lower intrathoracic trachea is splayed against the vertebral column. This was not present in patient 2 or 3. (c) Postoperative correction. The obstructing proximal sternum and compressive brachiocephalic artery have been removed. The artery was transplanted laterally and the lower trachea and bronchi were splinted posteriorly with Marlex [2]. (d) The brachiocephalic artery was lengthened with a graft and rerouted lower and lateral to the trachea in patients 1 and 2. (Reprinted from Grillo HC, Surgery of the trachea and bronchi; 2004:424–7 [2], with permission.)
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The brachiocephalic artery was lengthened with a polyethylene terephthalate fiber (Dacron) graft and relocated to the ascending aorta, crossing the mediastinum low enough to avoid contact with the trachea (Fig 4d). This relieved the second point of tracheal compression.
Through a right thoracotomy, the splayed trachea and main bronchi were restored to a normal contour by posterior membranous wall splinting, using polypropylene mesh strips, thus correcting the distal tracheobronchial obstruction (Fig 4c). Additional anterior vertebral osteotomies were considered, but proved to be unnecessary in this patient.
The patient was fully relieved of obstructive symptoms. Anatomic correction was demonstrated on CT scan (Fig 5). Tracheal collapse was no longer evident on expiratory CT scan.
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Fig 5. Postoperative computed tomography scans in patient 1 showing a very adequate lumen in both the upper [A] and lower [B] trachea. Note the sternal alteration in A, compared with Figure 3A, and the thickened membranous wall of the trachea in B, compared with Figure 3B.
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He continued to have some limitation of exercise performance but no longer suffered stridor or airway obstruction. Pulmonary function tests 4 months after operation showed improvement: FEV1 was 1.89 L (43%), vital capacity was 2.21 L (43%), FEV1 to forced vital capacity ratio was 0.82, peak expiratory flow rate was 3.93 L/s, and maximum breathing capacity was 76 L/min. The restrictive pulmonary defect was consistent with the chest wall deformities, confirmed by exercise study. A cardiovascular limit to exercise tolerance was also documented, as might be expected. The patient completed university studies and maintains healthy status 10 years later.
Patient 2
A 36-year-old woman underwent surgical treatment for severe scoliosis 22 years earlier, and had removal of a spinal rod 13 years before her current admission. For years she has had respiratory limitation on exercise, which was attributed to restriction as a result of scoliosis. She was also believed to have asthma. For several months, she had worsening dyspnea on exercise and a sense of airway blockage. Sometimes she experienced difficulty in passage of food in her throat and below. On physical examination, the vertebral column was deeply depressed when viewed dorsally, and exhibited reversed dorsal thoracic curvature.
Chest CT and magnetic resonance imagining showed a straight anteriorly displaced vertebral column with marked decrease in the anteroposterior diameter of the thoracic inlet. The trachea was markedly narrowed at this level from anterior to posterior. Bronchoscopically a compressed mid trachea further narrowed abruptly to a slit on expiration (Fig 6). The overall anteroposterior diameter of her chest between the sternum and vertebrae was diminished. The brachiocephalic artery crossed the trachea adjacent to the area of narrowing. The lowermost trachea and main bronchi appeared normal. Thus, she seemed to present an acquired straight back syndrome.
The operation (H.C.G., C.D.W.) was performed through a curved transverse incision over the sternal angle. The upper sternum was removed through the second interspace as described in case 1, the upper 2 cm was removed, and the balance was thinned and later replaced. The brachiocephalic artery arose from a common origin with the left carotid. It was detached at its origin from the carotid artery and relocated to the right of the trachea using a Dacron graft from the ascending aorta. The compressed segment of trachea was malacic. Tracheal resection was deferred to avoid danger of contaminating the vascular graft.
She improved after the operation, but continued to have episodic dyspnea, especially on raising her arms or folding them over her chest. Further radiologic studies and bronchoscopy confirmed a malacic, easily collapsing segment of trachea 3 cm in length located 2 cm above the carina. The trachea could be severely but not completely compressed by rotating the clavicular heads inward. The segment of trachea was resected, and the heads of both clavicles were removed at a second procedure.
The patient's breathing thereafter was much improved. The cross-sectional area of her trachea could still be reduced by extreme crossing of her arms in front of her chest, although not as completely as before. Tracheal narrowing or malacia were not demonstrated with stress positioning on inspiratory and expiratory chest CT scan.
Patient 3
This 21-year-old man with straight back syndrome became troubled with dyspnea on exertion, worsening during the course of 2 years, especially when he bent forward. Marked pectus excavatum was present, and the sternum was rotated toward the right. The anteroposterior dimension of the thorax was 3.6 cm. At the xiphoid, the distance to the vertebral bodies was 6.5 cm. The heart was displaced to the left. A CT chest scan showed that the tracheal anteroposterior dimension was 1.9 cm on inspiration, but only 0.8 cm on expiration. Bronchoscopy demonstrated mid-tracheal narrowing to 30% of resting anteroposterior diameter with respiration.
Pectus excavatum repair (J.C.W.) was performed, with excision of costal cartilages three through six bilaterally, division of both second cartilages, and two transverse osteotomies of the sternum. The depressed right side of the sternum was detached from all cartilages, and its prominent portion was removed and used as bone grafts in the osteotomies. An Adkins bar was positioned at the level of the fourth rib to stabilize the sternoplasty. Bronchoscopy then and 6 months later showed a greatly improved tracheal lumen.
The patient has remained vastly improved in symptoms for 7 years.
Patient 4
A 28-year-old man with Strümpell's familial spastic paraplegia, who had suffered multiple episodes of asphyxia, showed marked anterior displacement of the thoracic spine and costovertebral joints, with narrowing of the upper mediastinum. The distance between the sternal notch and the spine was 2.8 cm. The trachea was markedly compressed, and the left brachiocephalic vein was obstructed between the upper sternum and the vertebral bodies (Fig 7). Compression extended to the carina because of protruding vertebrae, with carina and mainstem bronchi entrapped between the spine and the aorta. Bronchoscopy confirmed severe extrinsic mid-tracheal compression for a distance of 5 cm. He required intubation.
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Fig 7. Preoperative thoracic computed tomographic scan in patient 4 showing marked anteroposterior narrowing of the upper mediastinum that compressed the trachea. An endotracheal tube is necessarily in place.
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Partial upper sternotomy (P.G.D., S.M.) permitted the flattened trachea to regain normal size when the manubrial edges were distracted. To maintain a distance of 5 cm between the sternoclavicular joints, a plate of methylmethacrylate was wedged into the inferior angle of the partial sternotomy. The defect was covered with mobilized pectoralis major muscles, sutured in the midline. Bronchoscopy demonstrated an enlarged and stable tracheal lumen. Postoperative CT scan confirmed this correction (Fig 8).
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Fig 8. Postoperative thoracic computed tomographic scan, patient 4, showing the distracted sternum and a very adequate tracheal lumen. Contrast is present in the superior vena cava.
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The patient has not experienced further respiratory distress or dyspnea in 9 years since the operation. Recent CT shows a patent airway with slight asymptomatic indentation of the trachea by the head of the right clavicle.
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Comment
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Abnormalities of the spine and bony thorax can narrow the anteroposterior dimension of the mediastinum sufficiently to affect pulmonary function [3] and cause tracheal or bronchial compression [4]. Straight back syndrome has chiefly been noted for its cardiovascular manifestations and as a cause of "pseudo heart disease," ie, clinical signs simulating organic heart disease [1, 5–9]. The syndrome has not previously been reported to be associated with tracheal compression [1, 5–8], although a patient attributed to have unusual ossification of the retrosternum with "insufficient kyphosis" may also show this abnormality [10]. Pectus excavatum (patients 1 and 3) may work in concert with the vertebral deformity in straight back syndrome to narrow the thoracic inlet sufficiently to cause tracheal obstruction. This was mimicked in part by an acquired anterior and vertical displacement of the spine (patient 2). The narrowing in patients 1 and 2 also limited the domain of the brachiocephalic artery, adding another point of compression. The mechanics of compression are sufficiently varied that a variety of surgical solutions were individually directed to the specific problems.
In patients 1 and 2, obstructions attributable to the superior margin of the sternum and to the brachiocephalic arteries were removed, respectively, by resection and repositioning, and the lower tracheal flattening in patient 1 was corrected by posterior wall tracheal splinting. In the second patient, residual tracheal malacia dictated a second corrective procedure. In patient 3, the point of compression by the markedly deformed midsternum was relieved by modified pectus repair alone. In patient 4, a paraplegic, a simple solution of wedging the sternum apart was elected, using a methyl methacrylate plate [11, 12]. Tracheal and bronchial compression as a result of shortened distance between spine and sternum has also been described in patients with severe motor and intellectual disabilities [13].
After recognition of tracheal obstruction of this type, each patient merits individual analysis, principally with dynamic imaging and bronchoscopy, to provide the basis for surgical correction.
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References
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- Jazzar AS, Dalton WE, Bradley NE, et al. Methyl methacrylate plate to prevent compression after heart transplantation Ann Thorac Surg 1993;55:1242-1243.[Abstract]
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Abstract
Introduction
