Primary tumours of the spine are rare, with a 1 to 2 per cent incidence being reported in most large series. These tumours are frequently diagnosed at an advanced stage of the disease. The diagnosis is often delayed because the most common presenting symptom is back pain, a ubiquitous human complaint. Furthermore, 30 to 50 per cent of the cancellous vertebral body must be involved before the lesion is visible on plain radiographs. Involvement of the pedicle is more readily noted on radiographs due to the lysis of cortical bone. Neurological involvement in these patients can have a slow indolent course or a rapid deterioration. Neoplasms in the thoracic region are prone to rapid neurological progression due to the spinal cord's tenuous vascular supply. Treatment of spinal tumours is aimed at achieving mechanical stability, neurological decompression, and pain relief.

Patients have pain or neurological symptoms, or both. Pain as the primary presenting symptom occurs in 84 per cent of patients. Symptoms from metastases may be a consequence of: (1) an enlarging mass that breaks through the cortex and invades paravertebral soft tissue; (2) compression of nerve roots; (3) pathological fracture; (4) spinal instability secondary to vertebral body destruction; or (5) cord compression. Primary tumours, specifically osteoid osteoma, also present with pain, complaints usually increasing at night. A diagnostic hallmark of osteoid osteoma is the complete abatement of pain symptoms with aspirin therapy. The typical stages of symptom progression start with back pain, followed by radicular pain, and ending with cord compression in 5 per cent of patients. Impingement on the cord most commonly occurs in the thoracic region with the anterior motor tracts being affected first. Loss of sphincter control is usually a late finding. The rate of onset of neurological symptoms is an important prognostic parameter. Rapid deterioration, occurring in less than 24 h, usually implies poor chance for recovery.

These patients also require a thorough laboratory evaluation. Patients with known primary tumours may be on chemotherapy or radiation protocols and their haemoglobin, white cell, and platelet counts may be abnormal. Likewise it is necessary to monitor serum calcium for the development of malignant hypercalcaemia, seen most commonly in myeloma, lymphoma, and breast carcinoma.

Once the suspicion of neoplastic disease has been raised, plain radiographs are the first line of evaluation. Tumours of the spinal column, however, are not always readily identified on plain radiographs. The second line of diagnostic studies includes technetium-99 bone scanning. This has been identified as the most sensitive method for localizing a neoplastic process in the spine. Bone scans are limited, however, by the fact that all processes which result in increased blood flow show as a positive reading. Therefore fractures due to osteoporosis may show an identical picture to that of tumour. One further advantage of bone scanning is the ability to visualize the entire spinal column, thereby identifying non-contiguous lesions with one study. It should be noted, however, that bone scans may be falsely negative in cases of myeloma.

Evaluation of the spinal canal can be undertaken with myelography. If a region of the lumbar spine is being examined it is important to monitor for free flow of dye into the thoracic portion of the spine and thus rule out a second site of cord impingement. A 9 per cent incidence of non-contiguous lesions causing cord compression has been reported. When coupled with computerized axial tomography (CT) scanning not only is the canal thoroughly evaluated but the bony architecture can also be accurately assessed. Furthermore, extension of the tumour into adjacent soft tissue structures or adjacent vertebral levels can be identified.

Magnetic resonance imaging (MRI) is also very helpful in tumour evaluation. Cord compression is clearly delineated with this method as well as bony and soft tissue involvement. One further advantage of MRI is the ability to visualize extensive regions of the spine in a non-invasive study. In some circumstances preoperative angiography and embolization may be warranted. This applies especially to tumours with a rich vascular supply, such as thyroid carcinoma, hypernephroma, and giant cell tumours.

Primary lesions of the spine account for 2 to 10 per cent of all bone tumours. The thoracic region is the most commonly affected site and the vertebral body is affected in two-thirds of cases. Factors which are associated with a malignancy are older age at diagnosis and lesions in the vertebral body.

The most commonly identified benign tumours are osteoblastoma, osteochondroma giant cell tumour, aneurysmal bone cyst, haemangioma, osteoid osteoma, and eosinophilic granuloma. Although categorized as benign tumours these lesions are capable of producing disabling deformity and can be fatal. In particular the aneurysmal bone cyst can present as a explosive and lytic lesion causing widespread bony destruction. Eosinophilic granuloma, also known as vertebra plana, commonly leads to complete vertebral body collapse. This collapse can and does reconstitute in the majority of cases. One other locally aggressive benign lesion is the giant cell tumour. These tumours are well known for their high rate of recurrence.

Initial treatment of benign primary tumours requires an accurate diagnosis, often achievable with CT-scan guided needle biopsy. Once the histology of the benign primary tumour is established attention is turned to neurological compromise and structural stability of the spine. If surgery is not indicated on the basis of either of these factors then the lesion can be monitored with serial examination. Radiation and chemotherapy have no role in the treatment of these benign lesions.

Malignant primary tumours most frequently in the spine are solitary plasmacytoma, chordoma, chondrosarcoma, lymphoma, Ewing's sarcoma, osteosarcoma, and fibrosarcoma. As with benign lesions it is necessary to start with an accurate tissue diagnosis. Once the diagnosis of malignant primary is made, either with needle or open biopsy, the best prognosis will be obtained with complete excision of the lesion. Curettage is ineffective in controlling these lesions. The mean 5-year survival rate for these patients is related to tumour type and extent of initial excision. Lesions amenable to total excision can be followed by 75 per cent 5-year survival as compared with 0 per cent for curettage. Plasmacytoma and chondrosarcoma have the best prognosis for survival (30 per cent 5-year survival), whereas osteosarcoma and lymphoma have the lowest survival rates (15 per cent 5-year survival).

Regardless of the primary tumour, the spine is the most common site for skeletal metastases. Some 35 to 70 per cent of patients who die of cancer have evidence of metastases to the spine. The vertebral body with its well vascularized sinusoids, acting like a blood sieve, is affected seven times more frequently than the posterior elements. Many of these metastases are not identifiable on plain radiographs and go unnoticed until autopsy.

Three-quarters of all spinal metastases originate from primaries in the breast, prostate, kidney, thyroid, or as lymphoma or myeloma (Fig. 1) 2509,2510. Batson's paravertebral plexus acts as a valveless conduit for metastases from the breast and prostate to reach the vertebral column. Metastases from the breast and prostate are further differentiated from other metastatic lesions by presenting frequently as osteoblastic tumours.

Class I lesions have no significant neurological involvement and Class II lesions have involvement of bone without collapse or instability. Patients with Class I or Class II lesions can generally be treated with chemo- or hormonal therapy or with localized radiation and followed closely for progression of the tumour.

Class III lesions have major neurological compromise but without significant involvement of bone. The initial line of treatment for these patients is radiation augmented with systemic steroid administration. Decompressive laminectomy is not recommended in this situation and indeed may do more harm than good. When the neurological deficit is of a rapid onset (less than 24 h) the prognosis for recovery no matter what treatment is undertaken is grim. If surgical treatment is contemplated in this category the precise location of the offending lesion should be ascertained and the approach should be planned in such a way that the neural elements can be thoroughly decompressed.

Class IV lesions exhibit vertebral collapse with associated pain due to a mechanical cause or instability without neurological compromise, and Class V lesions show vertebral collapse or instability with associated major neurological impairment. Patients who fall within the last two categories are considered candidates for surgical decompression and stabilization. Class IV and Class V lesions represent end-stage tumour progression or bony destruction that cannot be expected to respond to non-operative measures.

Preoperative planning in these cases requires knowledge of the primary neoplasm, the exact location and extent of the tumour, the structural integrity of all three spinal columns, and in certain cases the vascular supply to the lesion. Armed with this information the spine surgeon can confidently approach the lesion with the goal of decompressing the neural elements and providing a structurally stable spine. The spinal column can be stabilized in these cases with the aid of rods, plates, allograft bone, and PMMA bone cement.

Pain without fracture or objective evidence of neural compromise may be treated with endocrine manipulation. The patient may be placed on oestrogen or testosterone or an orchiectomy may be performed.

Treatment of painful lesions or lesions without deformity may consist of bracing and irradiation. Once pathological fracture occurs the spine may be stabilized with constructs incorporating PMMA. Cement augmentation should be reserved as a means of last resort since these fractures generally heal through callus formation.

Patients with skeletal metastases from thyroid carcinoma have a good prognosis. The bony lesion may be treated with radiation, endocrine, or chemotherapy with expectation for spontaneous ossification of the lesion.

Metastatic hypernephroma can present with extremely painful lesions. These tumours are vascular and appear as aggressive and explosive lesions. Early stabilization is appropriate before extensive bony destruction occurs. An anterior approach to the thoracic spine may frequently be required in this situation.

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