• Gábor Kasó, Zsolt Horváth, Katalin Szenohradszky, János Sándor, and Tamás Dóczi.
• Department of Neurosurgery, University of Pécs, Pécs, Hungary.
• Acta Neurochir (Wien). 2008 Jul 1;150(7):677-83; discussion 683.

ObjectiveThis study was intended to assess the results of post-operative CT scans in three groups of patients following percutaneous vertebroplasty (VP) using different navigation and injection methods, in an attempt to explain the radiological characteristics of extravertebral cement leakage with relation to needle placement and focused on the ventral epidural accumulation of bone cement. Furthermore, we have suggested a morphological (and functional) classification of the types of cement leakage.MethodsBetween July 2001 and February 2005, 123 percutaneous VP procedures were performed during 75 sessions in 65 patients for treatment of painful osteoporotic vertebral body compression fractures. These included:- Group I: 28 patients, 33 sessions; 50 right sided unilateral VP under fluoroscopic control with central position of the tip of the needle within the bone marrow. Group II: 27 patients, 28 sessions; 50 bilateral VP under fluoroscopic control with separate cement injections into both "hemivertebrae". Group III: 14 patients, 14 sessions; 23 bilateral VP navigated by frameless stereotaxy (neuronavigation). Needles were positioned strictly into the lateral thirds of the vertebral bodies. Leakages were classified as epidural, foraminal, intradiscal, venous paravertebral, compact extravertebral on the post-operative CT scans, and their frequency was compared in relation to the navigation method and the position of the tip of the needle.ResultsGroup I: extravertebral cement was detected in 23 patients (82%), and in 35 (70%) of the 50 vertebrae treated (ventral epidural: 23 vertebrae = 46%; intradiscal: 12 vertebrae = 24%; venous paravertebral: 8 vertebrae = 16%; intraforaminal: 7 vertebrae = 14%; and compact extravertebral: 3 vertebrae = 6%). Group II: extravertebral cement was detected in 20 patients (74%), and in 38 (76%) of the 50 vertebrae treated (ventral epidural: 12 vertebrae = 24%; intradiscal: 12 vertebrae = 24%; venous paravertebral: 9 vertebrae = 18%; and foraminal: 1 vertebra = 2%). Group III: extravertebral cement could be detected in 10 patients (71%), and in 10 (43%) of the 23 vertebrae treated (ventral epidural: 3 vertebrae = 13%; intradiscal: 8 vertebrae = 34%; venous paravertebral: 4 vertebrae = 17%).ConclusionThe incidence of epidural accumulation of bone cement may be concluded to be closely correlated with the position of the tip of the needle. Centrally injected bone cement may easily invade into the basivertebral system, and the material can then be transferred via these veins toward the ventral epidural space, and result in canal compromise and/or compression of the neural elements. The results of statistical analysis (Chi-square test) revealed that injection of bone cement into the lateral third of the vertebral body significantly decreases the extent of ventral epidural leakage. Therefore, a strictly lateral injection is advised, when the tip of the needle is placed into the lateral third of the vertebral body. Frameless stereotaxy navigation improves achievement of accurate needle placement and decreases the frequency of ventral epidural leakage. It is a safe and very accurate method for positioning of the injecting needles.

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