Object. The use of polymethylmethacrylate (PMMA) cement by percutaneous injection in cases requiring vertebroplasty provides pain relief in the treatment of osteoporotic vertebral compression fractures. A retrospective study was performed to assess what caused PMMA cement to leak into the epidural space and to determine if this leakage caused any changes in its therapeutic benefits. Methods. Polymethylmethacrylate was injected into 347 vertebral compression fractures in 159 patients. The cement leaked into the epidural space in 92 (26.5%) of 347 treated vertebrae in 64 (40.3%) of the 159 patients, as demonstrated on postoperative computerized tomography scanning. Epidural leakage of PMMA cement occurred more often when injected above the level of T-7 (p = 0.001) than below. The larger the volume of PMMA injected the higher the incidence of epidural leakage (p = 0.03). Using an injector also increased epidural leakage (p = 0.045). The position of the needle tip within the vertebral body and the pattern of venous drainage did not affect epidural leakage of the cement. Leakage of PMMA into the epidural space reduced the pain relief expected after vertebroplasty. The immediate postoperative visual analog scale scores were higher (and therefore reflective of less pain relief) in patients in whom epidural PMMA leakage occurred (p = 0.009). Three months postoperatively, the authors found the highest number of patients presenting with pain relief, including those in the group with epidural leakage, and at this follow-up stage there were no significant differences between the two groups. Conclusions. The authors found that epidural leakage of PMMA after percutaneous vertebroplasty was dose dependent. The larger amount of injected PMMA, the higher the incidence of leakage. Injecting vertebral levels above T-7 also increased the incidence of epidural leakage. Epidural leakage of PMMA may attenuate only the immediate therapeutic effects of vertebroplasty.

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