We have developed a technique for total en bloc spondylectomy through a posterior approach and now report our experience of 20 patients with a solitary or localised metastasis in the thoracic or lumbar vertebrae. There are two steps: an en bloc laminectomy, followed by en bloc resection of the vertebral body with an oncological wide margin and the insertion of a vertebral prosthesis. Pain was relieved in the 17 patients who could be assessed; 11 of the 15 patients with a neurological deficit were much improved, impending paralysis being prevented in 5 patients. There have been no local recurrences. Nine patients are at present alive with a mean follow up of 17.4 months.

We have developed a new surgical technique, 'total en bloc spondylectomy' (TES), to treat a solitary metastasis in the thoracic or lumbar vertebra. This operation is designed as a local cure for the metastatic site and involves the radical resection of the affected vertebra with a wide margin. The spondylec tomy consists of two steps: en bloc laminectomy with posterior spinal instru ments for stabilisation (first step) and en bloc corporectomy and replacement using a vertebral prosthesis (second step) . TES makes it possible to remove the affected vertebra extracompartmentally with its tumour barrier and accomplishes circumferential decompression of the spinal cord. Before clinical practice, we constructed experimental models using cats to examine spinal cord blood flow (SCBF) after ligation of the nerve roots and circumspinal decompression. The changes of SCBF were negligible, so it was proved that TES on one vertebra has little effect on spinal cord circulation. This method was used in 24 patients. Fourteen of the 18 patients with neurological deficits improved remarkably, and the 23 evaluable cases experienced pain relief. Impending paralysis was pre vented in all six patients by this surgical intervention. There has been no recurrence of the local tumour after surgery. After a median follow up period of 14. 1 months, 12 patients have survived. These data suggest that TES may have a significant clinical value in the treatment of spinal metastasis.

The advantages of total en bloc spondylectomy include resection of the involved vertebra(e) in two major blocs, rather than in a piecemeal pattern, and completion of the procedure during one surgical session posteriorly. The "total en bloc spondylectomy" offers one of the most aggressive modes of therapy for primary spinal malignancy.

Hydrostatic pressure directly affects the synthesis of collagen and proteoglycan by the intervertebral disc cells.