The use of a side-opening injection cannula in vertebroplasty: a technical note.

Abstract

A human cadaveric investigation was conducted to determine the effect that a side-opening injection cannula in monopedicular percutaneous vertebroplasty had on the vertebrae filling pattern. To assess the filling pattern in vertebroplasty using a monopedicular technique, and to compare a standard front-opening filling cannula with a side-opening cannula. Vertebroplasty is an effective treatment for osteoporotic vertebral fractures. Clinical and biomechanical investigations show its efficacy even in asymmetrical filling patterns. However, the risk of cement extravasation is a major concern with this technique. Two different bone cement-injecting cannulas were compared: a standard front-opening cannula (8 gauge, 6 inches long) and a cannula of the same dimensions with a side-opening at its distal end. Eight pairs of osteoporotic nonfractured cadaver vertebrae (T10-T11) were augmented with low-viscosity polymethylmethacrylate under axial C-arm control. The filling pattern was assessed semiquantitatively. The cross-section in its lateral extension was divided into four equal bands, and the appearance of the cement in each respective zone was assessed after cement injections of 2, 4, and 8 mL. The extravasation of bone cement also was monitored. With the side-opening cannula, the cement flow reached Zone 3 in six of eight cases, whereas with the front-opening cannula, the polymethylmethacrylate was observed in Zone 3 in only three cases. In no case was the cement observed in Zone 4. In five of eight cases using front-opening cannulas, extravasation into the vessels was observed after 3 to 4 mL of bone cement had been injected. No extravasation was noted with the use of the side-opening cannula unless the amount of cement exceeded 8 mL. A side-opening cannula can improve the cement-filling pattern in monopedicular vertebroplasty, as compared with a standard front-opening cannula. The risk of extravasation is diminished if the cement flow is directed medially.