Ex Vivo Experiments of a New Injection Cannula for Vertebroplasty

Abstract

An experimental study using cadaveric vertebrae. To measure the injection pressure in an ex vivo model and determine whether the redesigned cannula, featuring 2 distinct sections of different diameters, significantly reduces the injection pressure. An important limitation of vertebroplasty is the excessive pressure required to inject sufficient cement. The redesigned cannula accounts for the "bottleneck" of the injection previously identified. It has a distal section that is adapted to the pedicles and a proximal section with a larger diameter. Two cannulas were tested, a conventional 8-gauge and the redesigned cannula. There were 3 mL of cement injected in small strokes of 0.75 mL into the left and right hemivertebrae. A custom-made injection device monitored the injection pressure and cement volume. Average injection pressure was 2.3 MPa, often approaching the human physical limit and resulting in insufficient filling. The average pressure of the redesigned cannula was 44% lower than that of the conventional cannula, a highly significant result (P < 0.001). The new cannula may improve vertebroplasty by significantly easing cement injection. It is cost effective and can be easily integrated into the existing procedure.