Pathological anatomy and classification

Dorn Spinal Therapy

Spine Healing Therapy

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Malignant metastatic cells most frequently spread to the spine hematogenously with tumor emboli following the paravertebral plexus (plexus of Batson) [3, 11, 45, 53] that is characterized by a lack of valves. It is postulated that the venous blood return is shifted into the paravertebral plexus via the intervertebral and basivertebral veins due to increased intra-abdominal and intrathoracic pressure. As a result metastases which follow this pathway result in the characteristic pattern of bony spread because tumor cells are seeded by this mechanism into the capillary network of the vertebral bodies. Due to its avascular nature the disc is usually spared from tumor involvement: however, the most frequently and severely affected part of the vertebra is the vertebral body (in about 80%) followed by the pedicles and the posterior elements. This constellation explains why most of the spinal metastasis are located in front of the spinal cord or dural sac ending up with an anterior epidural compression. More than 90% of spinal metastases are extradural and only 5% intradural and less than 1% intramedullar [45]. Less frequently cancer cells spread into the spine through aortic segmental arteries, for example, in lung cancer [45, 49]. Finally there is also the option of direct spread through direct tumor infiltration into the spine, e.g., the Pancoast's tumor of the lung.

There have been several attempts to classify and stage spinal tumors [7, 8, 9, 13, 16, 17, 27, 28, 50, 51]. DeWald et al. [13] suggested a classification system for spinal metastases that is oriented mainly towards surgical treat

Fig. 1 Tokuhashi et al. [50] scoring system to establish preoperative prognosis of metasta-tic spine tumor

Fig. 1 Tokuhashi et al. [50] scoring system to establish preoperative prognosis of metasta-tic spine tumor

ment. They proposed the following five classes with subgroups covering most of the possibilities of spinal metastases appearance:

- Class I: destruction without collapse but with pain.

- Class II: the addition of moderate deformity and collapse with immune competence. This class is considered a good risk for surgery.

- Class III: patients are immunocompromised with moderate deformity and collapse. This class carries greater risk for surgery.

- Class IV: includes patients with paralysis, collapse, and deformity with immune competence. This class is considered a relative surgical emergency.

- Class V:adds immune incompetence to paralysis, collapse, and deformity. This class is not considered a good operative risk.

This classification allows consideration of the tumor, potential instability, and patient physiology, which is a sensible approach to a difficult problem. Enneking et al. [17] developed a staging scheme for malignant tumors of the spine in particular in adaptation to the staging of musculoskeletal tumors in general. The WBB Surgical Staging System was been introduced in 1997 primarily for primary bone tumors of the spine [9]. This can be applied for metastatic spine tumors; however, there are presently few reports on the system's correlation with, for example, outcome when applied for surgical indications. Tokuhashi et al. [50] introduced a scoring system for the preoperative evaluation of metastatic spine tumor prognosis that, instead, allows a correlation of the tumor extent with the prognosis [51]. The system differentiates between intra-compartmental, extracompartmental, and multiple tumor involvement. The first two categories include types 1 - 3 and types 4 - 6, respectively, whereas multiple tumor involvement is categorized as type 7 (Fig. 1). This scoring system found increasing application in recent years as a baseline in publications to make the results comparable among different scientific publications. K. Tomita et al. [51] applied this system to propose their surgical strategy in spinal metastatic disease.

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