BACKGROUND

 

Conventionally, curettage or piecemeal excision has been the usual approach to vertebral tumors.

 

These approaches have clear disadvantages, however, including high risk of tumor cell contamination to the surrounding structures and residual tumor tissue at the site due to difficulty in demarcating tumor from healthy tissue.

 

 

These contribute to incomplete resection of the tumor as well as high local recurrence rates of the spinal malignant tumor. To reduce local recurrence and to increase survival, we have developed total en bloc spondylectomy (TES).10,11,14

 

In this method, the entire vertebra or vertebrae containing the malignant tumor are resected, together with en bloc

 

laminectomy, en bloc corpectomy, and bilateral pediculotomy using a T-saw through the posterior approach.9 Using this technique, we are able to excise the tumor mass together with a wide or marginal margin.

ANATOMY

 

The following tissues serve as barriers to spinal tumor progression: the anterior longitudinal ligament (ALL), the posterior longitudinal ligament (PLL), the periosteum abutting the spinal canal, the ligamentum flavum (LF), the periosteum of the lamina and spinous process, the interspinous ligament (ISL), the supraspinous ligament (SSL), the cartilaginous endplate, and the cartilaginous annulus fibrosus. However, both the PLL and the periosteum on the lateral side of the vertebral body are “weak” anatomic barriers. In contrast, the ALL, cartilaginous endplate, and annulus fibrosus are “strong” barriers. In the spine, one vertebra could be regarded as a single oncologic compartment and the surrounding tissues as barriers to tumor spread (FIG

1).5

 

 

 

FIG 1 • Compartment and barrier. SSL, supraspinous ligament; LF, ligamentum flavum; PLL, posterior longitudinal ligament; ALL, anterior longitudinal ligament; CL, capsular ligament; ISL, interspinous ligament.

INDICATIONS

 

Surgical indication for primary tumors

 

The surgical strategy for primary spinal tumors used at the authors' institution is based on Enneking's concept of musculoskeletal tumors3 (Table 1).

 

Surgical indication for metastatic tumors

 

 

 

Surgical strategy for spinal metastases (Table 2) consists of three prognostic factors12: Grade of malignancy

 

Visceral metastases

 

Bone metastases

 

The extent of the spinal metastases is stratified using the surgical classification of spinal tumors (Table 3), and technically appropriate and feasible surgery is employed, such as en bloc spondylectomy, piecemeal thorough excision, curettage, or palliative surgery.

 

 

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Table 1 Surgical Strategy for Primary Spinal Tumors

Surgical Staging

Contamination/Residual

Tumor

Surgical Margin

Spinal Cord Salvage Surgery

Benign tumor

 

1. Latent

Don't touch!

2. Active

OK/OK

Intralesional

Debulking (piecemeal)

3. Aggressive

No/no

Intralesional or

marginal

Thorough excision (piecemeal/en

bloc)

Malignant tumor

 

I. Low grade

No/no

II. High grade

No/no

Marginal or wide

Total en bloc excision

III. With

metastases

No/no

(Radical: impractical)

 

 

 

Table 2 Surgical Strategy for Spinal Metastases

 

 

	Table 2 Appendix Points for Each Primary Tumor
	point = slow growth 4 points = rapid growth Breast cancer* Lung cancer Thyroid cancer* Gastric cancer, esophageal cancer Prostatic cancer, testicular cancer Nasopharyngeal cancer points = moderate growth Hepatocellular cancer Renal cell cancer* Pancreas cancer, etc. Uterus cancer, ovarian cancer Bladder cancer   Colorectal cancer Melanoma   Sarcoma (osteosarcoma, Ewing sarcoma, leiomyosarcoma, etc.) Primary unknown metastasis Other rare cancers   … etc.
	*Rare types of the following cancers should be given 4 points as rapidly growing cancers: breast cancer, inflammatory type; thyroid cancer, undifferentiated type; renal cell cancer, inflammatory type.

 

 

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Table 3 Surgical Classification of Spinal Tumors

Intracompartmental

Extracompartmental

Multiple

Type 1

Vertebral body

Type 4

Spinal canal extension

Type 7

 

Type 2

Pedicle extension

Type 5

Paravertebral extension

Type 3

Body -lamina extension

Type 6

Adjacent vertebral extension

 

 

 

 

IMAGING AND OTHER STAGING STUDIES

 

Plain radiography

 

 

Computed tomography/magnetic resonance imaging Bone scan

 

 

Angiography and other studies Biopsy

SURGICAL MANAGEMENT

 

The TES operation was designed to achieve complete tumor resection en bloc, including main and satellite microlesions in a vertebral compartment to avoid local recurrence.

 

The primary candidates for TES are primary malignant tumor (stage 1, 2), aggressive benign tumor (stage 3), and isolated metastasis in a patient with long life expectancy (see Tables 1 and 2).

 

From the viewpoint of tumor growth (see Table 3), TES is recommended for types 3, 4, and 5 lesions and relatively indicated for types 1, 2, and 6 lesions.

 

Type 1 or 2 still can be a candidate for radiation therapy, chemotherapy, corpectomy, or hemivertebrectomy.

 

TES is not recommended for type 7 lesions. Systemic treatment or hospice care may be the treatment choice for these lesions.10,11,13 However, the final decision can be made individually based on discussion among the patient and his or her family and doctors.

 

Preoperative Embolization

 

Segmental arteries above and below the feeding artery, as well as the feeding artery itself, should be embolized preoperatively. This embolization technique dramatically reduces intraoperative bleeding without compromising spinal cord function.4,8,15

Positioning

 

The patient is placed prone over the Relton-Hall four-poster frame for the posterior approach to avoid compression to the vena cava.

 

Approach

 

The surgical approach is decided based on the degree of tumor development or affected spinal level.

 

 

Single posterior approach

 

 

For TES above L4, a single posterior approach is preferred rather than a posteroanterior combined approach as long as the tumor does not involve major vessels or segmental arteries.

 

Anteroposterior double approach

 

 

In type 5 or 6 tumors that involve major vessels or segmental arteries, anterior dissection followed by posterior TES is indicated. Currently, a thoracoscopic or mini-open approach is preferred for anterior dissection.

 

Posteroanterior double approach

 

 

Posterior laminectomy and stabilization followed by anterior en bloc corpectomy and placement of a vertebral prosthesis is indicated in spinal tumors at the level of L5 or L4 because of the technical challenge presented by the iliac wing and lumbosacral plexus nerves.

 

 

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TECHNIQUES

• Exposure

A straight vertical midline incision is made over the spinous processes and is extended three vertebrae above and below the involved segment(s).

The paraspinal muscles are dissected from the spinous processes and the laminae and then retracted laterally.

If the patient underwent a posterior route biopsy, the tracts are carefully resected in a manner similar to that used in limbsalvaging procedures.

After a careful dissection of the area around the facet joints, a large retractor, the articulated spinal retractor, which has a uniaxial joint in each limb and was designed for this surgery, is applied.

 

 

 

 

TECH FIG 1 • A. Exposure. B. Ribs on the affected level are transected 3 to 4 cm lateral to the costotransverse joint.

 

 

By spreading the retractor and detaching the muscles around the facet joints, a wider exposure is then obtained.

 

The operative field must be wide enough on both sides to allow dissection under the surface of the transverse processes.

 

In the thoracic spine, the ribs on the affected level are transected 3 to 4 cm lateral to the costotransverse joint, and the pleura is bluntly separated from the vertebra (TECH FIG 1).

 

To expose the superior articular process of the uppermost vertebra, the spinous and inferior articular processes of the neighboring vertebra are osteotomized and removed with dissection of the attached soft tissues, including the ligamentum flavum.

• Introduction of the T-Saw Guide

   

  To make an exit for the T-saw guide through the nerve root canal, the soft tissue attached to the inferior aspect of the pars interarticularis is dissected and removed using utmost care so as not to damage the corresponding nerve root.

   

  A C-curved malleable T-saw guide is then introduced through the intervertebral foramen in a cephalocaudal direction.

   

  In this procedure, the tip of the T-saw guide should be introduced along the medial cortex of the lamina and the pedicle so as not to injure the spinal cord and the nerve root (TECH FIG 2).

   

   

   

  TECH FIG 2 • A. Schematic diagram depicting introduction of the T-saw guide. B. A C-curved malleable guidewire is introduced through the right intervertebral foramen in a cephalocaudal direction.

   

  After passing the T-saw guide, its tip at the exit of the nerve root canal can be found beneath the inferior border of the pars interarticularis.

   

   

   

  A T-saw is passed through the hole in the wire guide and is clamped with a T-saw holder at each end. The T-saw guide is removed, and tension on the T-saw is maintained.

   

• Cutting the Pedicles and En Bloc Laminectomy

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  While tension is maintained, the T-saw is placed beneath the superior articular and transverse processes with a specially designed T-saw manipulator. With this procedure, the T-saw placed around the lamina is wrapped around the pedicle.

   

  With a reciprocating motion of the T-saw, the pedicles are cut, and then the whole posterior element of the spine (the spinous process, the superior and inferior articular processes, the transverse process, and the pedicle) is removed in one piece (TECH FIG 3).

   

  The cut surface of the pedicle is sealed with bone wax to reduce bleeding and to minimize contamination by tumor cells.1

   

   

   

  TECH FIG 3 • A,B. Right pedicle is cut with a reciprocating motion of the T-saw. C. Schematic drawing of the pediculotomy.

   

  To maintain stability after segmental resection of the anterior column, a temporary posterior instrumentation (“two above and two below” segmental fixation) is performed.

  Blunt Dissection around the Vertebral Body

   

  The spinal branch of the segmental artery, which runs along the nerve root, is ligated and divided. In the thoracic spine, the nerve root is cut on the side from which the affected vertebra is removed.

   

  The blunt dissection is done on both sides through the plane between the pleura (or the iliopsoas muscle) and the vertebral body (TECH FIG 4).

   

   

  Usually, the lateral aspect of the body is easily dissected with a curved vertebral spatula. Then the segmental artery should be dissected from the vertebral body.

   

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  By continuing dissection of both lateral sides of the vertebral body anteriorly, the aorta is carefully dissected posteriorly from the anterior aspect of the vertebral body with a spatula and the surgeon's fingers.

   

  When the surgeon's fingertips meet with each other anterior to the vertebral body, a series of spatulas, starting from the smallest size, are inserted sequentially to extend the dissection.

   

  A pair of the largest spatulas is kept in the dissection site to prevent the surrounding tissues and organs from iatrogenic injury and to make the surgical field wide enough for the surgeon to manipulate the anterior column.

   

   

   

  TECH FIG 4 • A. Schematic drawing of anterior dissection around the vertebral body. Segmental arteries on the right (B) and left (C) sides. D,E. Schematic drawings of anterior finger dissection around the vertebral body show the posterior (D) and axial (E) views. (continued)

   

   

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  TECH FIG 4 • (continued) F. Anterior finger dissection around the vertebral body. G. A pair of spatulas is kept around the affected vertebral body to protect the surrounding tissues and organs from iatrogenic injury and to make the surgical field wide enough for manipulation of the anterior column.

• Dissection of the Spinal Cord and En Bloc Corpectomy

   

  Using a cord spatula, the spinal cord (dura mater) is mobilized from the surrounding venous plexus and the ligamentous

  tissue.

   

  T-saws are inserted at the proximal and distal cutting levels of the vertebral bodies after confirmation of the disc levels with needles. Recently, a diamond T-saw is now available for corpectomy.

   

  The teeth-cord protector, which has teeth on both edges to prevent the T-saw from slipping, is then applied.

   

  The anterior column of the vertebra is cut by the T-saw, together with the anterior and posterior longitudinal ligaments (TECH FIG 5).

   

  The freed anterior column is rotated around the spinal cord and removed carefully to avoid injury to the spinal cord.

   

  With this procedure, a complete anterior and posterior decompression of the spinal cord (circumspinal decompression) and total en bloc resection of the vertebral tumor are achieved.

   

   

   

  TECH FIG 5 • A. A temporary posterior instrumentation is performed to maintain stability after segmental resection of the anterior column. B,C. The anterior column of the vertebra is cut by the T-saw, together with the anterior and posterior longitudinal ligaments. The teeth-cord protector, which has teeth on both edges to prevent the T-saw from slipping, is then applied. (continued)

   

   

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  TECH FIG 5 • (continued) D. Schematic drawing of cutting the anterior column. E. Diagram of en bloc corpectomy. F. Intraoperative photograph of specimen from the resected T7 vertebra. G. Specimens resected along with the compartment and barrier concept. H,I. Radiographs of resected specimens from metastatic tumor of T7 showing the complete vertebra in horizontal (H) and lateral (I) views.

   

   

   

• Anterior Reconstruction and Posterior Instrumentation

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An anchor hole on the cut end of the remaining vertebra is made on each side to seat the graft. A vertebral spacer such as a titanium mesh cylinder cage with autograft, allograft, or cement (TECH FIG 6) is properly inserted to the anchor holes within the remaining healthy vertebrae.

 

After checking the appropriate position of the vertebral spacer radiographically, the posterior instrumentation is adjusted to slightly compress the inserted vertebral spacer.

 

By this “spinal shortening” procedure, the block cylinder is caught tightly, and the anteroposterior 360-degree spinal reconstruction is completed. 2,7

 

If two or three vertebrae are resected, it is recommended that the connector device be applied between the posterior rods and anterior spacer (artificial pedicle).

 

 

 

TECH FIG 6 • A. A vertebral spacer is properly inserted to the anchor holes within the remaining healthy vertebrae. B. Schema of reconstruction (lateral view). C,D. After checking the appropriate position of the vertebral spacer radiographically, the posterior instrumentation is adjusted to slightly compress (10 mm in this case) the inserted vertebral spacer. E,F. Postoperative radiograph after spinal column shortening shows three pairs of preoperative embolization coils. (continued)

 

 

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TECH FIG 6 • (continued) G-I. Resection of two vertebrae. G. Bilateral artificial pedicles are placed. H,I. Postoperative radiographs of reconstruction with artificial pedicle.

 

 

 

PEARLS AND PITFALLS

 

Bleeding from the epidural venous plexus12

• Fibrin glue 1.5 mL that is injected manually into the epidural space in both the cranial and caudal direction of the targeted vertebra after en bloc laminectomy helps reduce oozing from the epidural venous plexus.

 

Blunt dissection around the vertebral body

• Careful step-by-step dissection with anatomic consideration is an important fundamental.

• Preceding TES by a posterior approach, vessels around the vertebral body are managed anteriorly using thoracoscopy or a minimally open approach. This is safer than performing TES by a single posterior approach in a patient in whom the segmental artery(ies) may be involved by the tumor.

• At lesions of L1 and L2, the diaphragm insertions should be dissected from the vertebral body before the lumbar arteries are dissected because the segmental arteries run between the vertebral body and diaphragm insertion.6

   

  Ligation of the segmental arteries

• Ligation of the segmental arteries up to three vertebral levels, even including a branch of the artery of Adamkiewicz, may not affect the spinal cord evoked potentials and spinal cord function.4,8,15

   

  Spinal cord injury ▪ Mechanical damage to the neural structures, especially shifting aside, twisting, and hanging down or upward of the cord, should be avoided.

  • Spinal cord stretching causes irreversible mechanical damage. Excessive nerve root traction also damages the cord due to the root avulsion mechanism.

     

    Risk of tumor cell contamination13

• Double rinsing with distilled water and highly concentrated cisplatinum is recommended to eradicate contaminated cancer cells.

   

  Spinal shortening ▪ The posterior instrumentation is adjusted to compress the inserted vertebral prosthesis slightly (5-10 mm) to secure it as a final step of spinal reconstruction using TES.

  • This process of spinal shortening provides two important advantages: (1) increased spinal stability of the anterior and posterior spinal column and (2) increased spinal cord blood flow, which is desirable to improve spinal cord function.7

 

 

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POSTOPERATIVE CARE

 

Suction drainage is used for 3 to 5 days after surgery.

 

The patient is allowed to start walking within 1 week after surgery.

 

The patient wears a thoracolumbosacral orthosis for 3 to 6 months until bony union is attained.

 

 

OUTCOMES

From 1989 to 2003, 284 patients with spinal tumors (primary, 86 patients; metastasis, 198 patients) were surgically treated and followed for a minimum of 2 years.

TES was performed in 33 of the 86 patients with a primary tumor; 17 patients with malignant tumors (3 osteosarcoma, 3 Ewing sarcoma, 3 plasmocytoma, 2 chondrosarcoma, and 1 case each of 6 other tumors) and 16 patients with aggressive benign tumors (4 patients with giant cell tumor, 3 patients with osteoblastoma, 3 patients with symptomatic hemangioma, and 1 case each of 6 other tumors).

Five-year survival of the 17 patients with primary malignant spinal tumors (stages 1 and 2) who underwent TES was 67% and that of the 16 patients with aggressive benign tumors (stages 2 and 3) was 100%.

In the same periods, TES was performed in 64 of 198 patients with spinal metastases. Of the 64 cases with a metastatic tumor, the primary organs were as follows: kidney, 18 cases; breast, 15 cases; thyroid, 9 cases; lung, 4 cases; liver, 4 cases; and other carcinoma, 14 cases.

Forty-three patients with the 2, 3, and 4 points out of 64 patients who underwent TES resulted in 2-year survival of 66.6% and 5-year survival of 46.6%.

Ninety-two of 97 patients (95%) had no tumor recurrence until death or last follow-up.

Five of 97 patients (5%) had local recurrence; the mean length of the recurrence was 22.1 months after operation. In all five patients with local recurrence, the recurrence arose from residual tumor tissue.

 

COMPLICATIONS

 

Excessive bleeding

Injury of the major vessels during blunt dissection of the vertebral body Spinal cord injury

Injury of lung or pleura Postoperative hematoma Liquorrhea

Pleural effusion Chylothorax Instrumentation failure

Infection, especially after preoperative radiation therapy

 

 

REFERENCES

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2. Akamaru T, Kawahara N, Sakamoto J, et al. The transmission of stress to grafted bone inside a titanium mesh cage used in anterior column reconstruction after total spondylectomy: a finite-element analysis. Spine 2005;30:2783-2787.

    

    

3. Enneking WF, Spanier SS, Goodmann MA. A system for the surgical staging of musculoskeletal sarcoma. Clin Orthop 1980;153:106-120.

    

    

4. Fujimaki Y, Kawahara N, Tomita K, et al. How many ligations of bilateral segmental arteries cause ischemic spinal cord dysfunction? An experimental study using a dog model. Spine 2006;31: E781-E789.

    

    

5. Fujita T, Ueda Y, Kawahara N, et al. Local spread of metastatic vertebral tumors. A histologic study. Spine 1997;22:1905-1912.

    

    

6. Kawahara N, Tomita K, Baba H, et al. Cadaveric vascular anatomy for total en bloc spondylectomy in malignant vertebral tumors. Spine 1996;21:1401-1407.

    

    

7. Kawahara N, Tomita K, Kobayashi T, et al. Influence of acute shortening on the spinal cord: an experimental study. Spine 2005;30:613-620.

    

    

8. Numbu K, Kawahara N, Murakami H, et al. Interruption of bilateral segmental arteries at several levels. Influence on vertebral blood flow. Spine 2004;29:1530-1534.

    

    

9. Tomita K, Kawahara N. The threadwire saw: a new device for cutting bone. J Bone Joint Surg Am 1996;78A:1915-1917.

    

    

10. Tomita K, Kawahara N, Baba H, et al. Total en bloc spondylectomy. A new surgical technique for primary malignant vertebral tumors. Spine 1997;22:324-333.

     

     

11. Tomita K, Kawahara N, Baba H, et al. Total en bloc spondylectomy for solitary spinal metastasis. Int Orthop 1994;18:291-298.

     

     

12. Tomita K, Kawahara K, Kobayashi T, et al. Surgical strategy for spinal metastases. Spine 2001;26:298-306.

     

     

13. Tomita K, Kawahara N, Murakami H, et al. Total en bloc spondylectomy for spinal tumors: improvement of the technique and its associated basic background. J Orthop Sci 2006;11:3-12.

     

     

14. Tomita K, Toribatake Y, Kawahara N, et al. Total en bloc spondylectomy and circumspinal decompression for solitary spinal metastasis. Paraplegia 1994;32:36-46.

     

     

15. Ueda Y, Kawahara N, Tomita K, et al. Influence on spinal cord blood flow and spinal cord function by interruption of bilateral segmental arteries at up to three levels: experimental study in dogs. Spine 2005;30:2239-2243.