Relations of the soft structures of the posterior mediastinum in the scoliotic spine

Potential Risk of Thoracic Aorta Injury from Excessively Long Right Pedicle Screws in Patients with Left Thoracic Scoliosis: A Computed Tomography Image Study

OBJECTIVE

We sought to investigate the changed position of thoracic aorta relative to spine in patients with left thoracic scoliosis and to analyze the potential risks of thoracic aorta injury from pedicle screw insertion in these patients.

METHODS

Twenty patients with left thoracic scoliosis (Group A) and 15 normal subjects with a straight spine (Group B) were included. Axial computed tomography images from T5 to T12 of all these subjects were obtained to measure the aorta-vertebral angle. The percentages of thoracic aorta located anteriorly to the screw trajectory were calculated on both the left and right sides.

RESULTS

The average aorta-vertebral angle in Group A was significantly larger than that in Group B at each level (P < 0.05) except T5. In Group A, both left and right pedicle screws might pose threats to the thoracic aorta. The percentages of aortas at risk from the right pedicle screw were high in the apical region. However, in Group B, only the left pedicle screw might pose threats to the aorta. No aorta was found to be at risk of injury from right pedicle screw insertion in Group B.

CONCLUSIONS

The thoracic aorta often lies anteriorly to the left pedicle screw trajectory in normal subjects, especially in the lower thoracic region. However, the thoracic aorta moves to the right side in patients with left thoracic scoliosis, making a large proportion of patients at risk of injury from right pedicle screw insertion in the apical region.

Absence of LTBP-3 attenuates the aneurysmal phenotype but not spinal effects on the aorta in Marfan syndrome

Fibrillin-1 is an elastin-associated glycoprotein that contributes to the long-term fatigue resistance of elastic fibers as well as to the bioavailability of transforming growth factor-beta (TGFβ) in arteries. Altered TGFβ bioavailability and/or signaling have been implicated in aneurysm development in Marfan syndrome (MFS), a multi-system condition resulting from mutations to the gene that encodes fibrillin-1. We recently showed that the absence of the latent transforming growth factor-beta binding protein-3 (LTBP-3) in fibrillin-1-deficient mice attenuates the fragmentation of elastic fibers and focal dilatations that are characteristic of aortic root aneurysms in MFS mice, at least to 12 weeks of age. Here, we show further that the absence of LTBP-3 in this MFS mouse model improves the circumferential mechanical properties of the thoracic aorta, which appears to be fundamental in preventing or significantly delaying aneurysm development. Yet, a spinal deformity either remains or is exacerbated in the absence of LTBP-3 and seems to adversely affect the axial mechanical properties of the thoracic aorta, thus decreasing overall vascular function despite the absence of aneurysmal dilatation. Importantly, because of the smaller size of mice lacking LTBP-3, allometric scaling facilitates proper interpretation of aortic dimensions and thus the clinical phenotype. While this study demonstrates that LTBP-3/TGFβ directly affects the biomechanical function of the thoracic aorta, it highlights that spinal deformities in MFS might indirectly and adversely affect the overall aortic phenotype. There is a need, therefore, to consider together the vascular and skeletal effects in this syndromic disease.

The effect of lateral wall perforation on screw pull-out strength: a cadaveric study

BACKGROUND

Lateral pedicle wall perforations occur frequently during pedicle screw insertion. Although it is known that such an occurrence decreases the screw pull-out strength, the effect has not been quantified biomechanically.

MATERIALS AND METHODS

Twenty fresh cadaveric lumbar vertebrae were harvested, and the bone mineral density (BMD) of each was evaluated with dual-energy radiography absorptiometry (DEXA). Twenty matched, 6.5-mm pedicle screws were inserted in two different manners in two groups, the control group and the experimental group. In the control group, the pedicle screw was inserted in a standard fashion taking adequate precaution to ensure there was no perforation of the wall. In the experimental group, the pedicle screw was inserted such that its trajectory perforated the lateral wall. Group assignments were done randomly, and the maximal fixation strength was recorded for each screw pull-out test with a material-testing system (MTS 858 II).

RESULTS

The average BMD for both groups was 0.850 g/cm(2) (0.788-0.912 g/cm(2)). The average (and standard deviation) maximal pull-out forces were 1,015.8 ± 249.40 N for the experimental group and 1,326.0 ± 320.50 N for the control group. According to a paired t-test, the difference between the two groups was statistically significant (P < 0.001).

CONCLUSION

The results of this study confirm that the maximal pull-out strength of pedicle screws decreases by approximately 23.4% when the lateral wall is perforated.

Endovascular aortic injury repair after thoracic pedicle screw placement

Our objective was to describe the management and prevention of thoracic aortic injuries caused by a malposition of pedicle screws in corrective surgery of major spine deformities. Positioning pedicle screws in thoracic vertebras by posterior approach exposes to the risk of injury of the elements placed ahead of the thoracic spine, as the descending thoracic aorta. This complication can result in a cataclysmic bleeding, needing urgent vascular care, but it can also be totally asymptomatic, resulting in the long run in a pseudoaneurysm, justifying the systematic removal of the hardware. We report the case of a 76-year-old woman who underwent spinal correction surgery for thoraco-lumbar degenerative kypho-scoliosis. Immediately after the surgery, a thoracic aortic injury caused by the left T7 pedicle screw was diagnosed. The patient underwent a two-step surgery. The first step was realized by vascular surgeons and aimed to secure the aortic wall by short endovascular aortic grafting. During the second step, spine surgeons removed the responsible screw by posterior approach. The patient was discharged in a rehabilitation center 7 days after the second surgery. When such a complication occurs, a co-management by vascular and spine surgeons is necessary to avoid major complications. Endovascular management of this kind of vascular injuries permits to avoid an open surgery that have a great rate of morbi-mortality in frail patients. Nowadays, technologies exist to prevent this kind of event and may improve the security when positioning pedicle screws.

Periaortic pedicle screw removal with endovascular control of the aorta and intraoperative aortography: a case report and review of the literature

Study Design  Case report and review of the literature.

Objective The objective of the article is to report the case of a 20-year-old patient with a threatened aortic injury from pedicle screw instrumentation successfully managed without aortic grafting.

Methods The patient's clinical course is retrospectively reviewed. The offending hardware was removed after gaining endovascular control of the aorta.

Results Intraoperative aortography was normal and no graft was placed. The patient remains asymptomatic at 2 years after surgery.

Conclusions Hardware impinging on the aorta can safely be removed by gaining endovascular control of the aorta. In the setting of normal intraoperative aortography in a young patient, we recommend against further intervention to avoid the known morbidity of aortic grafting.

Hiatal hernia and disorders of the spine: a historical perspective

Our understanding of esophageal disease and the foregut has evolved over the past 100 years, especially in recent times. Modern diagnostic technologies and new management paradigms have provided progressive insights into the anatomy, physiology, and normal and abnormal function of the esophagus, as well as improving patient care. Yet, the relationship between the esophagus and its close neighbor, the spine, is rarely discussed and likely underappreciated. Anatomic proximity and intertwined pathophysiology led early investigators to postulate relationships between esophageal disease and spinal abnormalities. More recent studies have illustrated a link between spinal disease and hiatal hernias. Objective radiographic measurements of kyphoscoliosis have correlated with increased hiatal hernia formation. Spinal abnormalities and disease of the esophageal hiatus are becoming more common in our aging population, with each carrying significant risk of morbidity and decreased quality of life. Operative planning and subsequent hiatal hernia repair must be undertaken in the context of these spinal abnormalities. A historical review of past publications related to the subject forms the basis for this publication, thus revealing insight and improving our understanding of the association between spinal abnormalities and hiatal hernias.

Combined endovascular and neurosurgical approach to the removal of an intraaortic pedicle screw

Iatrogenic aortic injuries are a potentially devastating complication of spine surgery. In instrumented cases, injuries may occur in the perioperative period due to iatrogenic vessel injury, or they may occur years later as prominent implants erode or penetrate major vessels. The authors present a case of a 71-year-old man in whom a thoracic pedicle screw was found perforating the thoracic aorta during routine follow-up 6 months after surgery. Due to the risk of future complications, the screw was removed while simultaneously delivering an endovascular aortic stent to gain vascular control. Surgical considerations and potential technical limitations are discussed.

Late diagnosis of pedicle screw malplacement with perforation of the thoracic aorta after posterior stabilization in a patient with multiple myeloma: case report

STUDY DESIGN

A case report.

OBJECTIVE

To demonstrate delayed diagnosis of screw malpositioning with perforation of the thoracic aorta after posterior stabilization of a Th7-vertebral collapse due to multiple myeloma. Relevant diagnostic and therapeutic strategies are outlined in the context of a rather unfortunate series of interventional events.

SUMMARY OF BACKGROUND DATA

Pedicle screw instrumentation has become a well-established standard in the surgical treatment of various disorders of the spinal column. Particularly at the upper-thoracic level, the close anatomic relationship of the spine to the aorta places it and other major structures at high risk. Although iatrogenic vascular injuries are rare, a few cases have been described.

METHODS

A 64-year-old female patient remarked progressive back pain after 2 years of uneventful recovery from a multilevel posterior stabilization by pedicle screw and rod instrumentation because of an osteolytic collapse of the Th7 vertebra. The subsequent computed tomographic scan demonstrated kyphotic deformity of the thoracic spine with transspinal and periaortic screw malplacement.

RESULTS

The revision strategy was an interdisciplinary single session two-phase operation. The primary phase included a left-sided thoracotomy, mobilization of the thoracic aorta, and posterior implant removal under vascular monitoring in right lateral position. The initially planned corporectomy of Th7 and subsequent vertebral body replacement by cage implantation via the anterior approach was dismissed because of critical tissue adhesions of the thoracic aorta to the anterior vertebral column. Finally, the thoracotomy was closed, the patient transferred into prone position and stabilized by a multilevel posterior reinstrumentation under fluoroscopy guidance.

CONCLUSION

Although the clinical course in malpositioned pedicle screw instrumentation may stay unremarkable, this case illustrates that in a proven injury to the thoracic aorta revision is mandatory to prevent further vascular damage. The appropriate strategy demands exact and provident planning using a preferably interdisciplinary approach.

Screw position after double-rod anterior spinal fusion in idiopathic scoliosis: an evaluation using computerized tomography

STUDY DESIGN

A retrospective evaluation of screw position after double-rod anterior spinal fusion in idiopathic scoliosis using computerized tomography (CT).

OBJECTIVE

To evaluate screw position and complications related to screw position after double-rod anterior instrumentation in idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Anterior instrumentation and fusion in idiopathic scoliosis is gaining widespread use. However, no studies have been published regarding the accuracy of screw placement and screw-related complications in double-rod and double-screw anterior spinal fusion and instrumentation in idiopathic thoracolumbar scoliosis surgery.

METHODS

CT examinations were performed after surgery in 17 patients with idiopathic scoliosis. At each instrumented level, the position of the screw and the plate relative to the spinal canal, relative to the neural foramen, and relative to the aorta was measured. Complications related to screw position were registered.

RESULTS

A total of 189 screws in 17 patients were evaluated. Malposition occurred in 23% (16 patients) of the total number of screws. Three screws (2 patients) were partially in the spinal canal (1%). This resulted in pain in the right leg in 2 patients. However, electromyography showed no abnormalities. At three levels (3 patients), there was contact between the instrumentation and the aorta. However, no vascular complications occurred. A total of 113 screws (10 patients) were placed under fluoroscopic control and 76 screws (7 patients) were placed without use of fluoroscopy. Less screw malposition was observed in the group in which fluoroscopic control was used (19% vs. 30%, not significant).

CONCLUSIONS

Screw placement in double-rod anterior spinal fusion in idiopathic scoliosis seems to be technically demanding, and the use of fluoroscopic control results in less frequent malposition. The risk of neurologic and vascular complications is low.

Endovascular treatment of an iatrogenic thoracic aortic injury after spinal instrumentation: case report

Iatrogenic aortic injuries after spinal surgery have been described, but are rare. We describe a case of a 77-year-old woman who underwent surgical correction of a debilitating spinal deformity at an outside institution. Postoperative thoracic spine radiographs and computed tomography scans revealed a misplaced pedicle screw at T5, which was impinging on the descending thoracic aortic wall. The patient was brought to the operating room, where a thoracic stent graft was deployed under fluoroscopic guidance as the malpositioned screw was manually retracted. The patient had an uneventful postoperative course, and was discharged within 24 hours. This case represents a rare but potentially morbid vascular complication of spinal instrumentation surgery that was successfully treated without the need for thoracotomy.

High level cross of the esophagus with the descending aorta in scoliosis: CT study

OBJECTIVE

The esophagus occasionally crosses the descending aorta at an unusually high level (3-5 cm inferior to the carina) in right-sided scoliosis. The purpose of this study was to analyze the mechanism of this finding.

MATERIALS AND METHODS

We prospectively evaluated thoracic CT scans in 30 patients with right-sided scoliosis. We assessed the alterations in the positions of the esophagus and the descending aorta by the thoracic deformity.

RESULTS

The descending aorta followed the scoliotic curve of the spine in 26 (87%) patients. The esophagus followed the scoliotic curve of the spine in 14 (47%) patients and did not in 16 (53%). The anteroposterior diameter of the thorax in the former group was significantly smaller than that in the latter (p < 0.01). High level cross of both structures was identified in 14 (47%) patients, and all of them belonged to the group in which the esophagus did not follow the scoliotic curve of the spine.

CONCLUSION

The unusual high level cross of the esophagus with the descending aorta occasionally seen in scoliosis is due to a difference in the positional alterations of the two structures resulting from the scoliosis.