En bloc resection with posterior release and anterior tumor delivery (L1 to L5)
En bloc resection of a primary tumor is a significant undertaking, even in the most experienced hands. We therefore recommend referring these cases to quaternary centers with experience in primary spine tumor surgery.
En bloc resections
Terminology is essential in primary tumor management.
An en bloc resection refers to a surgical attempt to remove a tumor in one piece without violating it.
On the other hand, an intralesional resection or a curettage refers to a deliberate intralesional resection.
An en bloc resection needs to be associated with a pathological margin description to be correctly defined.
Four types of margins are described:
Intralesional – resection margin is within tumoral tissue
Marginal – resection margin is within a reactional zone or pseudocapsule (in the spine, the epidural margin is often marginal)
Wide – resection margin is within normal tissue
Radical – this is extracompartmental resection and, as such, does not apply to spine tumors
Two conditions need to be met for an en bloc resection to be deemed possible:
If we consider the spinal canal as a ring, there needs to be enough circumference of that ring to be removed piecemeal to allow delivery of the neural element
Access to the nerve root sleeve at its dural origin is required
If these conditions are not met, an en bloc resection will not be possible without a planned transgression of the tumor.
In this illustration, the spinal canal is circumferentially surrounded by a tumor. There is not enough uninvolved portion of the ring to allow an en bloc resection.
Proper planning is instrumental in the management of primary spine tumors. A multidisciplinary approach may be required depending on the localization of the tumor.
Embolization procedures are recommended to reduce operative blood loss in hypervascular tumors, especially during more extensive resections.
Embolization should be considered for hypervascular tumors, such as giant cell tumors, aneurysmal bone cysts, and hemangiomas.
The role of the embolization is:
To reduce the vascularity of the tumor
To facilitate dissection around the tumor
Mapping of spinal cord vascular supply
Embolization on its own may also have a therapeutic effect.
This image shows the embolization of a hypervascular tumor.
A posterior tumor release followed by anterior delivery is generally recommended for a lumbar tumor involving the vertebral body.
During the posterior approach, the uninvolved part of the spinal ring will be resected in a piecemeal fashion, and osteotomies and soft tissue dissections will be performed.
A wide visualization is essential in these cases, and a laminectomy involving half a level above and below the tumor is recommended.
The goal is to achieve:
Good visualization of normal and abnormal anatomy
Safe decompression of the neural elements
Appropriate posterior tumor mobilization allows the tumor to be delivered during the anterior approach.
En bloc resection is a destabilizing procedure. As such, long constructs are required.
Generally, two to three vertebrae above and below the tumor are included in the construct. In multilevel tumors, or when there is poor bone quality, this construct can be extended.
The risk of implant failure may be decreased by using cemented fenestrated screws in patients with poor bone quality. Alternatively, other techniques like hooks or sublaminar wires can be used.
As the procedure is often curative, it is important to verify that the spine is reconstructed in good alignment, and a solid bony union should be attempted.
Every case is unique.
To illustrate the surgical principle of an en bloc resection with posterior release and anterior delivery in the lumbar spine, we will use an L2 tumor located in segments 4–8 of the WBB classification.
3. Patient preparation and surgical access for posterior release
A wider dissection will typically be performed for primary tumors compared to a trauma case.
Great care should be taken not to enter the tumor during exposure.
Review preoperative images to verify whether the tumor invades the lamina. In such cases, exposure of the posterior elements should be performed with great care, and the use of Cobb elevators should be avoided.
The incision may need a caudal extension when the tumor involves the lower lumbar spine.