Traditional anterior and posterior approaches for the surgical treatment of the thoracic spine are associated with significant morbidity. To address these issues, minimally invasive approaches have been developed. One role has been for treatment of spinal tumors. Whether malignant or benign, one of the key factors is to improve the quality of life, and by decreasing the morbidity associated with the surgery itself, this goal may be more likely achieved.
Spinal tumors are classified as extradural, intradural-extramedullary, or intramedullary. Intradural-extramedullary tumors comprise approximately two-thirds of all primary spinal tumors. These are generally benign in nature, but can cause symptoms by compression of neural elements. On the other hand, intramedullary tumors are rare.1 Tumors can also be categorized as primary or secondary (metastatic). Metastatic tumors most commonly affect the thoracic spine (70%), followed by lumbar (20%), then cervical (10%). Primary osseous tumors of the spine are uncommon in comparison to metastatic disease. They can be classified as benign or malignant.
The most common symptom is pain. Patients will often present with complaints of progressive back and/or radicular pain. Compression of the neural elements may lead to weakness, which, if left unaddressed, could lead to frank paralysis. Treatment options vary based on complete or incomplete deficits.
Treatment for primary or metastatic tumors to the spine includes radiation, radiation plus chemotherapy, stereotactic radiosurgery, hormonal therapy, or surgical decompression followed by radiation. Radiation alone and chemotherapy are options for patients with newly diagnosed disease without neurologic deficit, no evidence of instability, and are relatively asymptomatic; this is especially true for radiosensitive tumors. When surgery is indicated, the goals should include, but are not limited to, palliation, providing stabilization, preventing spinal cord compression, pain control, definitive diagnosis, improvement of the quality of life, and arthrodesis. Factors to consider when planning surgery include the histologic type of tumor and its location(s) within the spine, cord compression, portion of vertebrae involved, anticipated mode of spinal instability, type of prior or subsequent adjuvant treatment, and anticipated life expectancy of the patient.2–4
The surgical treatment of thoracic tumors ranges from percutaneous vertebroplasty to anterior- and posterior-based open procedures.5,6 Anterior-based approaches, such as traditional open thoracotomies, are effective in the treatment of the thoracic spine; however, they are associated with significant access morbidity.7–11 Pain, prolonged chest drainage, pulmonary complications, and extended hospital stays are issues to be further considered after surgery. A lateral retropleural approach aims to be less destructive to the surrounding tissues by not compromising the pleura. To mitigate some of the morbidity associated with open procedures, minimally invasive thoracoscopic methods were developed and have proven to be effective, but challenging in terms of learning curve and application.7–10,12
Open, posterior-based approaches are better suited for lesions that involve the posterior elements or an extension into the anterior column.2 Either the transpedicular or costotransversectomy approach allows for resection of the posterior elements, epidural tumor, and the involved vertebral bodies.13,14 These approaches may be preferential for patients with significant medical comorbidities, multilevel disease, or involvement of upper thoracic lesions.15 The lateral extracavitary approach is similar, but the access portal is more lateral with respect to the paravertebral musculature.
It is evident that there have been many advances in the treatment of pathology located in the thoracic spine. Minimally invasive techniques offer an alternative to traditional, open approaches. In this study, we describe our experience with the mini-open lateral approach for the removal of thoracic tumors.
Materials and Methods
A retrospective review of a prospectively maintained spine tumor database was performed of all consecutive patients who underwent a minimally invasive lateral approach for treatment of a thoracic tumor at 2 institutions between 2007 and 2009. All surgeries were performed by the 2 senior authors (J.S.U. and W.D.S.). The operative side and approach, either transthoracic or retropleural, was dictated by the location of the pathology and the surgeon's preference. Demographic variables such as sex, age, comorbidities, tumor pathology, and presenting symptoms were documented. All patient data were recorded including preoperative evaluation, operative procedure, postoperative follow-up, operative time, blood loss, length of hospital stay, and complications. Clinical outcome scores were also administered, measuring pain and function, before and after the surgery, using the visual analog scale (VAS) and Oswestry disability index (ODI). All patients were scheduled for routine follow-up at 2 weeks, 6 weeks, 3 months, 6 months, 12 months, and 24 months after surgery.
All patients were placed and secured in a true lateral position on a radiolucent table. Under fluoroscopic guidance, the index level and pathology were located and marked on the skin. In all cases, the side of the approach was chosen according to the vertebral level and the location of the abnormality. If a transthoracic approach was selected, then a 3- to 4-cm oblique incision was made parallel to and between the ribs. The intercostal muscles and parietal pleura were then incised as well to enter the thoracic cavity. If a larger exposure was required, then a portion of the rib was resected. When a retropleural approach was selected, a 6-cm long oblique incision (following the trajectory of the rib at the index level) was made at the midaxillary line. Approximately 5 cm of the rib immediately overlying the target level was dissected subperiosteally from the underlying pleura and neurovascular bundle and removed. The portion of resected rib was set aside for use as autograft in the setting of arthrodesis. Once the parietal pleura was exposed, the plane between the endothoracic fascia and the pleura was developed. The pleura was then mobilized anteriorly until the lateral side of the vertebral body, pedicle, and adjacent discs were exposed. During a left-side approach, the aorta and hemiazygos vein were also retracted anteriorly. An expandable retractor system (MaXcess®, NuVasive®, San Diego, CA) was then inserted and secured with a flexible table-mounted arm assembly. Once the retractor was placed and adequate exposure was obtained, the goals of the operation were performed using standard surgical techniques. A combination of high-speed drills, curettes, rongeurs, and osteotomes were used for bony removal. Through this approach the tumors were resected, the neural elements were decompressed, and the spine was stabilized when necessary.
In the event of a corpectomy, ventral reconstruction was performed using expandable titanium cages and bone autograft (rib). Spinal instrumentation was completed by ventrolateral plate/screw fixation (Traverse®, NuVasive, Inc) through the expandable retractor, and/or percutaneous posterior pedicle screw/rod fixation (SpheRx® DBR®, NuVasive, Inc). In instances where the dura was opened for resection of the tumor, it was repaired in a primary fashion with a running 5–0 stitch. Fibrin glue was then applied to the dural incision for reinforcement and a lumbar drain was placed.
In the event of a pleural violation or transthoracic approach, a red rubber catheter may be used to remove all air from the thoracic cavity as long as the visceral pleura has not been violated. The red rubber catheter is placed in the pleural space, out through the wound and into a water filled container with the end submerged under water. The wound is closed in the standard fashion including all the layers of muscle and fascia. A purse string stitch is placed around the red rubber catheter. A valsalva is performed, end inspiratory hold, until no more air bubbles are seen coming from the red rubber end under water. This signifies that all the air has been removed from the thoracic cavity. The red rubber catheter is removed as the purse string stitch is tied. This obviated the need for a chest tube.
Between 2007 and 2009, 21 consecutive patients (14 males, 7 females) were identified who underwent a minimally invasive lateral approach to the thoracic spine for tumor removal. Sixteen patients underwent a left-sided approach, while 5 were from the right. The mean age was 57 years with a range of 30 to 80 years. The indications for surgery included pain, instability, spinal cord compression, and neurologic deficit. All patients successfully underwent a minimally invasive lateral approach without conversion to an open procedure. The mean operative time was 117 minutes. The mean total blood loss was 291 mL and ranged from 25 to 1650 mL. The average length of stay in the hospital was 2.9 days. Mean follow-up was 21 months with a range of 6 to 24 months. Of the 21 patients, 5 presented with neurologic deficit which improved after surgery. All other patients remained neurologically stable. Resection of the thoracic tumors necessitated a range of bony removal from minimal to a complete corpectomy depending on the goals of surgery. Assessment of the degree of resection was based on tumor histology. Subtotal resection of metastatic tumors was not considered a failure of the approach. In this series, 13 patients required a corpectomy for tumor resection. The tumors resected included both primary and secondary types, histologically consisting of neurofibromas, meningiomas, osteosarcomas, and other metastases. Complete demographic and diagnosis information is included in Table 1. The number of transthoracic and retropleural approaches were 16 and 5, respectively. Resection of a portion of a rib was performed in all patients. No patient required single-lung ventilation during the procedure.
Data collected were then subjected to statistical analysis. Comparison of outcome data for each patient was performed with a paired t test. Outcome measures assessed include the VAS pain score and the ODI measure of disability. There was a mean improvement of 4.8 in VAS scores and 27.8% in ODI. VAS before surgery averaged 7.7 ± 1.68 and improved to 2.9 ± 1.42 at the last follow-up visit, a 62.3% improvement. ODI before surgery averaged 52.7% ± 15% and improved to 24.9% ± 14% at the last follow-up visit, representing a 52.8% improvement (Figure 1).
Perioperative complications occurred in 1 patient (4.8%) who developed pneumonia after surgery. There were no intraoperative complications noted. No postoperative pneumothoraces were identified. There were no postoperative pseudomeningoceles or cerebrospinal fluid leaks. There was no injury to the lung or vascular structures during the approach. No evidence of infections or hardware failure was identified. Two patients were noted to have residual tumor on follow-up imaging. The tumor types were multiple myeloma and meningiomas. These patients were asymptomatic and did not require any further surgical intervention. Two patients, in whom the spinal lesion was a secondary metastasis, died secondary to their primary cancer at 6 and 12 months postoperative. They both remained neurologically intact at the time of their death. Individual treatment and complication variables are included in Table 2. Two representative case examples are shown in Figures 2 to 5.
Surgical approaches for disorders of the thoracic spine have traditionally included anterior- and posterior-based approaches, or a combination of them.16–20 When indicated, the goals of surgery for the treatment of tumors are to provide pain relief, decompress the neural elements, realign, and provide stability. The affected spinal level, pathologic process, as well as surgeon's preference often determines the technique used.
The posterior approaches (lateral extracavitary, transpedicular, and costotransversectomy), first introduced by Capener and later modified by Larson, have become popular and are frequently used routes to access the spine in multiple different areas.17,21 These approaches avoid the morbidities associated with entry into the chest and provide adequate exposure for neural decompression, corpectomy, vertebral reconstruction, and simultaneous posterior spinal fixation.16,22 However, these approaches require extensive muscle dissection and typically result in copious amounts of blood loss. The disadvantages of the posterior approaches include an oblique view of the dural elements and possibly requiring sectioning of nerve roots for placement of interbody device. The posterior correction of a kyphotic deformity also requires multiple fixation points both cranially and caudally. Surgical decompression of ventrally located cord-compressive lesions and the durability of kyphosis correction in patients with significant ventral column destruction from a solely posterior approach have been unsatisfactory.18,23 The size (or footprint) of the interbody device that can be placed from posterior is limited secondary to constraints of the approach. This may lead to an increased rate of subsidence. Due to the unfavorable results obtained from posterior-only approaches, anterior-based approaches have been developed.24–26
Anterior transthoracic approaches have long been established in the management of many pathologic conditions of the anterior thoracic spine.27 Anterior approaches provide adequate access to the ventral aspect of the spine and allow decompression without the associated risks of spinal cord or nerve root manipulation.24–26 However, a thoracotomy requires a large skin incision, lung and rib retraction, and muscle dissection. These all can contribute to postoperative pulmonary dysfunction (such as pulmonary contusions, atelectasis, pleural effusions, hemothorax, and chylothorax), as well as significant peri- and postoperative pain from extensive rib resection. Major complications with use of the thoracotomy approach have been shown in as many as 79% of patients,28,29 tend to extend hospitalizations, and increase medical resource utilization.30
To reduce the morbidity associated with thoracotomy, less invasive thoracoscopic techniques have been developed and refined for performing a thoracic corpectomy and reconstruction.10,31,32 Thoracoscopy is capable of producing the same exposure as that with the transthoracic route without the need for a large incision or rib resection. Although the incidence of complications is considered to be lower than open in thoracotomies, rates have been reported to be as high as 14.1% to 29.4%.31,33,34 Complications include transient intercostal neuralgia, postoperative atelectasis, pneumothorax, pleural effusion, and hemothorax.31,33,34 Additionally, there is a steep learning curve for thoracoscopic procedures.12,35,36
One major disadvantage of anterior-based approaches is that in some instances the pathologic process is faced first and the neural elements are not visualized until the anterior decompression is completed. In select cases, the anterior longitudinal ligament may need to be resected and this may lead to destabilization.
In an effort to avoid the drawbacks and morbidity related to a thoracotomy/thoracoscopic approach or the extensive tissue dissection associated with posterior approaches, the retropleural thoracotomy was developed and popularized by McCormick.18 Unlike posterior approaches, a retropleural thoracotomy permits a direct view of the dura/neural elements and allows the surgeon to expose the lateral canal without the need to dissect or potentially sacrifice the intercostal nerve or intraforaminal radiculomedullary artery.10,32 In contrast to the transthoracic approach, the dissection remains extrapleural and potentially poses less risk of injury to the aorta, vena cava, and sympathetic plexus, while decreasing the chance of developing a duropleural cerebrospinal fluid fistula.18,37,38 This approach allows the surgeon to have direct visualization of the dura and any anterior-based pathology simultaneously. There is preservation of the anterior longitudinal ligament, posterior ligamentous structures, and PLL, which is less destabilizing biomechanically. However, this approach requires a relatively large incision and extensive rib resection.18
MIS Lateral Approach
Traditional approaches to the thoracic spine have been associated with a significant amount of morbidity.19,39–42 To address these issues, minimally invasive techniques have been developed. Minimally invasive surgery (MIS) aims to decrease muscle and tissue disruption, postoperative pain, blood loss, time to mobilization, and length of stay, without compromising the goals of surgery.43 Many reports in the literature have already demonstrated the benefit of MIS techniques.35,44–46
With the advent of expandable and tubular retractors, specialized instruments, and fiber optic light sources, we are now able to perform a minimally invasive lateral approach (transthoracic or retropleural). As with all MIS, this approach is a technical variation that aims to achieve the same goals of surgery while decreasing the morbidity associated with the standard techniques.18,20,47 This procedure combines all the advantages of the lateral approach with the benefits of MIS techniques. In the current series, the perioperative complication rate was 4.8% (1/21 patients) (pneumonia), which was considerably lower than reported rates in the literature, that is, 6.9% and 11.1% for posterior- and anterior-based approaches, respectively.48 In our series of patients, we did not encounter any wound-related complications or infections. Street et al reported a 16.7% wound-related complication rate when using the posterolateral vertebrectomy approach.49 The MIS lateral approach provided exposure to meet the goals of surgery (i.e., tumor resection, decompressing the neural elements, and stabilization), while decreasing the approach-related morbidity. This approach avoids the extensive muscle dissection associated with the posterior approaches and provides a direct view of the pathology. It provides the same exposure as the anterior approaches but does not require single-lung ventilation, a large incision, or extensive rib resection. In the current series, patients of all ages (30–80 years) and both benign and malignant pathologies were able to be treated successfully.
Patients with metastatic cancer have multiple comorbidities, higher perioperative complication rates, are immunocompromised, and have a higher incidence of wound infection/dehiscence secondary to adjuvant therapy.49,50 In this subset of patients, MIS offers the advantages of using smaller incisions leading to less wound-related complications and somatic pain. This may lead to an improvement in patient's health-related quality of life outcomes and hasten the initiation of adjuvant therapy. In fact, early mobilization has been shown in other spine indications to increase pulmonary and metabolic function, decrease the risk of medical complications related to inactivity, and decrease overall recovery time.36 When a retropleural approach is used, there is an added benefit of preventing or limiting tumor cell dissemination into the chest cavity when compared with open thoracotomy.
One drawback of the minimally invasive retropleural approach to the thoracic spine is that if posterior instrumentation is required, then a second incision must be made. Also, when using the lateral approach, there is a long working distance in a relatively narrow working space. Surgeons attempting this approach should be familiar with MIS and working through an MIS retractor. Retropleural dissections may not be feasible after a previous ipsilateral thoracotomy secondary to adhesions. Patients with osteomyelitis of the spine and spinal metastases can have marked paraspinal pleural reactions with adhesive thickening of the parietal pleura and infiltration of the pleura by tumor or inflamed fibrous tissue.
In our series, no patient required conversion from a MIS approach to a standard open procedure. However, in certain instances, we would recommend and/or choose other approaches to the thoracic spine. For example, secondary to the constraints of the mediastinum anteriorly and the axilla laterally, in upper thoracic levels (T1–T4), we would recommend using a posterior approach. If there is primary involvement of the posterior elements with bilateral pedicle invasion, then we would also choose a posterior-based approach. In the event of any recurrences, either the same side or contralateral side may be used.
The surgical treatment of tumors located in the thoracic spine has been accomplished from the anterior, posterior, lateral, or a combination of these approaches. The MIS lateral approach to the thoracic spine achieves the same goals of surgery with the hope of decreasing the approach-related complications and morbidity of the traditional approaches. Whether benign or malignant, intradural or osseous, the MIS lateral approach was successful for the surgical treatment of various histologic types of tumors in all ages of patients. It is an excellent alternative and should be in the armamentarium of all spine surgeons.
- The treatment of thoracic tumors can be performed by many different approaches, both anterior and posterior, which carry significant associated morbidities that increase frequency of complications, increase recovery time, and decrease the quality of recovery.
- Minimally invasive (endoscopic) approaches have been used for removal of thoracic tumors with varying efficacy, but without the morbidities commonly associated with open techniques.
- A mini-open, lateral technique may provide certain benefits, including direct visualization and the use of traditional techniques, without the difficulties of endoscopic and morbidities of open techniques.
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