Pancreatic cancer (PC) is one of the most aggressive cancer with high lethality. It was estimated the 5-year survival rate of PC is 6%, and the mortality rate is almost equal to the incident rate ^[1]. The risk factors of PC are included in the smoking, obesity, family history, as well as the enviroDuring the treatment of thoracic intervertebral foramen (TIF) lesions, such as schwannoma and nerve sheath cysts, the ultimate goal of surgery is to achieve complete resection. However, achieving this using posterior approach combined with transforaminal or transthoracic approach is problematic ^[1-3]. In dumbbell-shaped schwannomas, piecemeal excision of tumor, using a combined posterior and transforaminal approach, typically results in incomplete tumor resection and destruction of the intervertebral articular process (IAP), leading to poor neurological outcome and impaired spinal stability. Consequently, the goal in modern surgical management of complex TIF lesions is to achieve total lesion resection and spinal reconstruction ^[4-6].

Due to the high rates of morbidity, virtually all anatomical studies have been concerned with the cervical intervertebral foramen (CIF) ^[7-10]and lumbar intervertebral foramen (LIF) ^[11-14]. Meanwhile, many authors have reported favorable outcomes when treating complex CIF or LIF lesions using anterior, posterior, or transforaminal approaches^[15-17]. Although the anatomical characteristics of TIF are similar to CIF or LIF, careful attention is required for the following reasons: 1) the thoracic spinous process is imbricate; 2) the thoracic canal is very narrow; 3) the IAP is difficult to identify; and 4) the vertebral transverse process, and ribs, partially shield the foramen (Figure 1) ^[18]. All of these considerations preclude the use of traditional approaches aimed to identify and completely expose the TIF.

The posterior approach, combined with TIF posterior wall opening (Figure 2C), allows for complete complex TIF lesion resection in conjunction with fixation techniques and TIF reconstruction in a subsequent procedure. We herein describe the operational steps involved in treating complex TIF lesions, using a posterior approach combined with TIF posterior wall opening, to achieve favorable neurological and spinal outcomes.

Patient Selection and General Information

Between 2013 and 2015, 22 patients presenting with complex TIF lesions underwent total resection and spinal reconstruction at the First Affiliated Hospital, College of Medicine, Zhejiang University (Hangzhou, China). Ten of the patients were female, and twelve were male. Patients ranged between 28 and 72 years of age (mean age = 45 years). No patient had a history of spinal surgery. The details of the complex TIF lesions of our patients are provided in Table 1. In total, 22 patients with 24 lesions underwent 25 TIF posterior wall-opening procedures. All of the TIF lesions were dilated to some degree. Twelve patients were diagnosed with dumbbell-shaped schwannomas, of whom two presented with a destroyed vertebral pedicle. Six patients were diagnosed with nerve sheath cysts, of which one exhibited two nerve sheath cysts at bilateral TIF lesions of the same level (Figure 5A). One patient presented with two nerve sheath cysts at different levels of the homolateral TIF. Two patients were diagnosed with osteochondroma, one of whom had a lesion surrounding a pedicle of vertebral arch involving two adjacent TIFs. The lesion grew posteriorly to the exterior of the lamina (Figure 3A-B). Two patients were diagnosed with TIF hemangioma. The opened TIF was reconstructed in these patients using fixation techniques and bone grafting. Screws and rods were used in the spinal reconstruction of all patients. No patient developed intraspinal infection, incision splits, or cerebrospinal fluid (CSF) leakage in the short-term (between 1 and 3 m), and 16 patients had no fixation loosening or spinal instability in the long-term (between 6 and 24 m).

Anatomical Considerations and Operative Nuances

The vertebral notches of adjacent vertebrae constitute TIF (i.e., the porous channel of spinal nerve roots departing from the spinal cord). It is composed of upper, lower, anterior, and posterior walls. The upper and lower walls represent vertebral pedicle notches; the anterior wall involves the lateral vertebra, intervertebral disc, and posterior longitudinal ligament, whereas the posterior wall involves IAP (Figure 1) ^[19]. The corresponding nerve root is surrounded by cellular tissue and small blood vessels at the point at which it passes through the foramen; the interior section is laterally recessed ^[20]. The presence of IAP, transverse processes, ribs, and visceral structures nearby to the lesion, poses significant challenges to radical lesion excision in the TIF.

The posterior approach towards complex TIF lesions involves ascertaining the precise location, and subsequently confirming it with pre-operative computed tomography (CT), magnetic resonance imaging (MRI), and intraoperative mobile x-ray. Incisions should allow for exposure of the lesion’s adjacent vertebral pedicle screw entry point. Following reconfirmation of the lesion’s location, the adjacent pair of vertebral lamina and spinous processes is typically removed in a single piece, such that the intra-spinal section can be fully exposed. The posterior wall of the TIF is subsequently opened using a high-speed drill, allowing the intra-TIF and extra-spinal sections to be sufficiently exposed.

Although certain complex TIF lesions can be resected using a posterior approach combined with transforaminal or transthoracic approach, this method is inconvenient and often render total resection difficult (see Illustrative Cases, Sec. 3) ^[1-3]. We favor a posterior approach combined with TIF posterior wall opening (Figure 2C), which is particularly useful when the lesion is located nearby to the TIF. The main advantage that this method offers is complete lesion resection and spinal reconstruction in a single incision and direction, thereby reducing the length of the overall operation.

For complex TIF lesions, spinal reconstruction at the appropriate level is required. When the ventral spinal column is intact, dorsal reconstruction is typically performed using the screw and rod fixation technique (SRFT). After the dorsal surface of the spine has been burnished, the removed vertebral lamina and spinous process are rendered granular to allow reconstruction of the TIF and fusion of adjacent vertebrae.

Illustrative Cases

A 37-year-old man presented with numbness and weakness of the right upper extremity, for 1 week, principally in the ulnaris ring finger and little finger. CT and MRI scans of his cervical spine were obtained. CT imaging demonstrated an annulus high-density lesion near the right pedicle of thoracic 1 (T1), involving C7/ T1 and T1/T2 foramen, and leading to spinal stenosis.This lesion also extended posteriorly to the exterior of the T2 lamina (Figure 3C-D). MRI scans demonstrated a complex annulus lesion with heterogeneous enhancement of gadolinium (Gd) near the right pedicle of T1. This lesion extended outward from the right C7/T1 and T1/T2 foramen to the right posterior mediastinum, which also extended posteriorly to the exterior of the T2 lamina (Figure 3A-B). Electromyogram (EMG) revealed that the motor-evoked potential (MEP) and sensory-evoked potential (SEP) of the right ulnar nerve were impaired. Based upon these observations, multiple osteochondromas were considered, and the patient was offered a posterior approach combined with C7/T1 and T1/T2 right intervertebral foramen posterior wall opening to achieve complete resection of the lesion. Spinal reconstruction was achieved using C6/T1/T2 SRFT, and bone granules were implanted to reconstruct the TIF and fuse the adjacent vertebrae. The patient was discharged 8 days post-surgery without any neurological dysfunction. Over the subsequent 15 months, the patient’s incision remained dry, with no fixation loosening or spinal instability. A CT scan obtained 6 months post-surgery revealed that the reconstructed spine was well-fused with the bone granules (Figure 4B-D). MRI indicated no osteochondroma recurrence 12 months post-operatively (Figure 4A). The patient has remained asymptomatic.

A 64-year-old woman presented with belt-like numbness and pain in the back and abdomen for 10 months. Bilateral navel levels were principally involved. CT and MRI scans of the thoracal spine were obtained. MRI scans revealed two ovals, hyperintense lesions located at the bilateral TIF of T10/T11 (Figure 5A). CT imaging revealed two ovals, iso-hypodense nodules located at the bilateral TIF of T10/T11; the bilateral TIF were slightly dilated (Figure 5B-C). Systemic workup using whole-spine MRI did not reveal any additional lesions. Based upon these observations, bilateral nerve sheath cysts were considered, and the patient was offered a posterior approach to seal the ventage of the bilateral T10 nerve in the intradural direction. The T10/T11 bilateral intervertebral foramen posterior walls were subsequently opened, and the bilateral nerve sheath cysts were completely aspirated by syringe. Spinal reconstruction was performed using T10/T11 SRFT, and bone granules were implanted to reconstruct the TIF and fuse the adjacent vertebrae. The patient was discharged 7 days post-surgery without any neurological dysfunction. During the following 12 months, the patient’s incision healed well, exhibiting ideal bone fusion and spinal stability. A CT scan obtained 6 months post-operatively indicated that the reconstructed spine was well-fused with bone granules (Figure 6B-D). MRI revealed that the bilateral oval nodules had almost disappeared, except for a small, distal residual cavity (Figure 6A). The patient remains in a healthy condition.

Between 2013 and 2015, 22 patients were successfully treated using a posterior approach combined with TIF posterior wall opening, for total resection and spinal reconstruction. Diagnoses were made according to physical examination, and CT and MRI scans. At the time that this manuscript was written, no patient had experienced any complications arising from SRFT use. Furthermore, no patient suffered intraspinal infection, incision splits, or CSF leakage in the short-term (between 1 and 3 months) or fixation loosening or spinal instability in the long-term (6–24 months). Imaging studies confirmed that the TIF and spinal reconstruction outcomes were favorable (Figure 4 and 6).

Based on the anatomical and biomechanical characteristics of thoracic vertebra, degenerative disease is extremely rare, and few researches concerning TIF has been previously conducted ^[18-20]. The use of a traditional posterior approach could facilitate exposure of intra-spinal, laterally recessed lesions (Figure 2B), but in cases where the lesion is in an intra-TIF location, or has spread to extra-TIF areas, this becomes problematic; we refer to such cases as complex TIF lesions. Partial intra-TIF lesions can be dragged using an angled nerve hook, but nerve root injuries and/or CSF leakage present a significant challenge. Partial, extra-TIF lesions could be exposed in conjunction with a transforaminal approach, but the presence of IAP, transverse processes, and ribs represents a significant obstacle. Certain lesions involving the posterior mediastinum should be subsequently resected in combination with a transthoracic approach ^[18].

However, all of these procedures are relatively inconvenient, and in certain complex cases, a satisfactory resolution is not possible. A posterior approach combined with TIF posterior wall opening, confers significant benefits in such cases. Patient 1 presented with a complex annulus lesion near the right pedicle of T1, involving the right C7/T1 and T1/T2 foramen. The lesion’s hard texture and special location, rendered transforaminal or transthoracic approaches impractical. Patient 2 presented with bilateral intra-TIF nerve sheath cysts at T10/T11. Following the sealing of the bilateral T10 nerve ventage, bilateral cysts should be aspirated to relieve nerve root compression; however, the bilateral IAP obstructs this procedure. In both cases, highly satisfactory results were obtained when the TIF posterior wall was opened. Despite certain large extra-TIF lesions growing in a forward direction, the ribs and transverse processes were amenable to additional expansion (costotransversectomy) to achieve full exposure and resection. Our method simplifies the surgical procedure, and shortens the number of hospital days. Furthermore, all 22 patients achieved a satisfactory clinical outcome.

SRFT is a common technique in spinal surgery. When complex TIF lesions are resected using our method, the IAP is destroyed and spinal instability, or spinal cord compression, will manifest at long-term follow-up. Spinal reconstruction and bone fusion has resolved this problem and therefore complements our method. Although SRFT may increase medical costs, it represents a rapid, effective, and reliable method of reconstructing the spine, and is thus clinically useful for patients with complex TIF lesions.

What’s more, many neurosurgeons, especially in China are lack of spinal anatomic knowledge and training course. Our method could on one side benefits these patients, on the other encourage more neurosurgeons to learn spinal anatomy and spinal fixation technique, so as to engage in more comprehensive spine operations.

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