Quadrantectomy for resection of spinal ependymomas with a new classification of unilateral approaches regarding bone drilling and the use of a new tool: The Balak ball-tipped water jet dissector

•The “quadrantectomy approach”, a sub-category of the unilateral approach is described for resection of spinal ependymoma.•A new classification system of the unilateral approach regarding bone drilling is proposed.•A new microsurgical instrument, the Balak ball-tipped water jet dissector, is described.

ObjectiveThe “unilateral approach” is widespread in surgery for spinal degenerative pathologies. However, it is seldom used for resection of spinal intradural lesions. We present two cases where the “quadrantectomy approach”, a sub-category of the unilateral approach, was used for resection of spinal ependymoma and propose a new classification system of the unilateral approach regarding bone drilling and describe the use of the Balak ball-tipped water jet dissector in this procedure.Patients and methodsTwo patients who underwent surgical treatment of spinal intradural tumor are presented. The tumors were resected using microscopic dissection techniques and neuro-monitoring. An instrument specifically designed for the dissection of the cauda equina nerve roots was used. The surgical technique is presented with stepwise photographs.ResultsContrast enhanced magnetic resonance imaging scans obtained on the second day after surgery showed that the tumors in both cases had been totally removed and the nerve roots had regained their natural shape. Histopathological diagnosis was a myxopapillary ependymoma in both cases. There were no postoperative neurological deficits and both patients recovered completely. At two-year and one-year follow-up respectively after surgery, the patients were perfectly well.ConclusionA quadrantectomy approach, which preserves the facet joints and midline structures, should be regarded as a safe subtype of unilateral approaches to spinal intradural lesions. This new terminology will be helpful in proper comparison of the results of various surgical approaches in terms of postoperative spinal instability. The ball-tipped water jet dissector is a beneficial tool for surgery in the cauda equina region.