Fig. 8.1
WBB Surgical Staging System. (1) On the transverse plane, the vertebra is divided into 12 radiating zones (numbered 1–12 in a clockwise order) and into 5 layers (A to E from the prevertebral to the dural involvement)
WBB Staging System. On the transverse plane, the vertebra is divided into 12 radiating zones (numbered 1–12 in a clockwise order) and into 5 layers (A to E from the prevertebral to the dural involvement). The longitudinal extent of the tumor is recorded by identifying the specific vertebrae involved. This system allowed for a more rational approach to the surgical planning, provided that all efforts are made to perform surgery along the required margins.
8.6 Terminology
The application of a common terminology is mandatory to exchange informations and to compare the results among institutions. The term “vertebrectomy,” as currently used by some, describes both an intralesional eggshell excision [13], and many authors use the term “radical” [14, 15] to mean any surgical margin that does not contain tumor.
Obviously, if the same terms used to describe en bloc resection are also used to describe gross total complete excision, it is difficult and confusing to compare results.
To stress the importance of a common language, the terms proposed by Enneking are recalled.
8.7 Intralesional Excision
Intralesional excision means a piecemeal removal of the tumor (“curettage,” “gross total resection,” “debulking”). It is an intralesional procedure; the tumor is violated, and any chance of obtaining tumor-free margins is lost. This procedure is appropriate for stage 2 benign tumors and for metastases. Anterior and or posterior approach according to the commonly known surgical procedures can be performed at any spine level. Combination of approaches must be considered to maximize the tumor removal (so-called extracapsular excision, i.e., excision of the tumor capsule). Microscopic and possible macroscopic tumor is however always left after these procedures, and local progression can be expected according to the growing potential of the disease. Local adjuvants can be associated. These become mandatory if intralesional surgery is performed in cases where en bloc is the treatment of choice, but it is not feasible due to surgical and anatomical constraints.
The ischemic effect on the tumor mass provoked by selective arterial embolization must be considered to substantially reduce bleeding, thus strongly reducing intraoperative bleeding and associated complications and allowing the surgeon to complete the excision.
8.8 En Bloc Resection
It is the attempt to remove the tumor as a single intact whole, fully encased by a cuff of healthy tissue (a circumferential margin of tumor-free normal tissue). It requires that the pathologist’s confirms the resected tissue around the tumor mass (the so-called margin) is tumor free.
The effectiveness of the margin as a barrier depends on its quality and also on the aggressiveness of the tumor. The margin is defined as “wide” when the plan of dissection has been peripheral to the reactive zone through normal tissue. Quality of the margin and thickness are relevant. A fascial barrier represents a wide margin, whereas 1 cm of muscle or cancellous bone may be inadequate to represent an appropriate barrier. The major issue in the decision-making process of planning en bloc resection concerns the possible functional sacrifices related to the quality of the structure to be resected in a whole with the tumor to achieve a wide margin. Marginal margin means that the plane of dissection has been performed along the reactive zone, very close to the tumor and that satellites of tumor may be left. Intralesional margin means that the tumor periphery is violated, and the tumor specimen is not covered by healthy tissue. Radical: this term should be applied to the en bloc removal of the tumor together with the whole compartment of origin. An example would be a thigh amputation for a tumor arising in the tibia. Or a scapulectomy for a tumor arising and still contained in the scapula. Consequently a radical resection in the spine defines to resect in bloc a full vertebra provided the tumor is fully confined inside the vertebra, including the spinal cord above and below. Even in this dramatic case, if the tumor has grown into the epidural space, the term radical will not be appropriate, as the epidural space is to be considered an extracompartmental area extending from the skull to the sacrum.
8.9 Palliative Procedure
This term describes all the surgical procedures generally directed toward a functional purpose (decompress the thecal sac, stabilize the spine) without any effective surgical removal of the tumor. Partial piecemeal removal of the tumor can be required to release the compression on the cord. An example could be the fixation of a pathologic fracture due to a mechanical collapse of a latent lesion or the decompression and fixation of a myeloma or other radio/chemo-sensitive lesion, later to be submitted for curative purpose to such oncologic treatments.
8.9.1 Surgical Techniques: En Bloc Resections in the Cervical Spine
The techniques of en bloc resection for tumors of the vertebral body in the thoracic and lumbar spine are well known [8–10, 16], while only single case reports of en bloc resections of cervical spine tumors have been published till now [17–20]. WBB staging system can be helpful in standardizing the surgical planning of en bloc resection according to different tumor extension and different spine regions. The great variability of these two parameters dictates that the same surgical procedure cannot be performed in all cases and that surgical planning must be tailored on single case.
Under the guidance of WBB staging system, six different approaches or combinations of approaches have been proposed (ref), ending in a total of ten different types of surgery: only anterior; only posterior; anterior first, posterior second; posterior first, double anterior second and third; posterior first, combined anterior and posterior second; and anterior first, posterior second, combined anterior (contralateral) and posterior.
Three techniques of en bloc resection can be standardized in the cervical spine, considering three possibilities of tumor growing as criteria to achieve a tumor-free margin en bloc resection. In the author’s opinion, different typology of tumor expansion will require violation of the tumor margin to save vital structures.
Single posterior approach is the obvious strategy to remove by en bloc resection a tumor arising in the posterior arch (Fig. 8.2). Criteria to achieve appropriate margins according to the WBB staging system (Fig. 8.1) include sectors 9 and 4 free from tumor. If the tumor grows in layer D, the margin will result intralesional during the release from the dura.
Fig. 8.2
Single posterior approach is the obvious strategy to remove by en bloc resection a tumor arising in the posterior arch. Criteria to achieve appropriate margins according to the WBB staging system (ref) include sectors 9 and 4 free from tumor. If the tumor grows in layer D, the margin will result intralesional during the release from the dura
Three steps must be planned: the first provides the appropriate margin over the tumor posteriorly growing by resecting inside the posterior muscles which cover the tumor mass if it is expanding in layer A (I). The second step is a piecemeal excision of sectors 9 and 4 must be performed by the technique preferred: by high speed burr or ultrasound osteotome or alternatively an osteotomy can be performed by wire saw or chisel (II). Once a transverse laminotomy above and below is performed, the tumor is released from the dura, and the specimen is resected en bloc (III).
In cervical spine tumors partially occupying the vertebral body (not involving sectors 6 and 7, otherwise see Fig. 4) and the posterior arch (at least three sectors not involved) to perform en bloc resection aiming at achieving a tumor-free margin specimen, two approaches should be planned: anterior first and posterior second (Fig. 8.3).
Fig. 8.3
In cervical spine tumors partially occupying the vertebral body (not involving sectors 6 and 7, otherwise see Fig. 4) and the posterior arch (at least three sectors not involved) to perform en bloc resection aiming at achieving a tumor-free margin specimen, two approaches should be planned: anterior first and posterior second
Anterior approach is first performed to leave healthy tissue over the tumor growing in the lateral masses (I) and to perform a sagittal groove till the epidural space in the vertebral body (II). Diskectomies or transversal grooves in vertebral bodies are performed to define the upper and lower margins, including ligation of the vertebral artery.
Related posts:
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Anesthesiological Management and Patient Positioning
Interventional Radiology: Presurgical Selective Angiographic Embolization (SAE) in Hypervascular Cervical Spine Tumours
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Complications of Cervical Spine Surgery
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