Injectable bone cements for use in vertebroplasty and kyphoplasty: state-of-the-art review.

Vertebroplasty (VP) and kyphoplasty (KP) are minimally invasive surgical procedures that have recently been introduced for the medical management of osteoporosis-induced vertebral compression fractures. The aim of VP is to stabilize the fractured vertebral body, while the goals of KP are to stabilize the fractured vertebral body and to restore its height to as near its prefracture level as possible. Both procedures involve injection of the setting dough of an injectable bone cement (IBC) into the fractured vertebral body, thereby highlighting the indispensable role that the IBC plays. Although there is a very large literature on IBCs, no detailed critical review of it has been published. Such a review is the subject of the present work, which is in seven parts. The review opens with a succinct introduction to VP and KP. The topics covered in the parts that follow are: (1) a listing of the 18 most desirable properties of an IBC (e.g., easy injectability, high radiopacity, and a resorption rate that is neither too high nor too low); (2) descriptions of the four classes of IBCs (calcium phosphates, acrylic bone cements, calcium sulfates, and composites); (3) concerns that have been raised with regard to the use of IBCs (such as the potential for thermal necrosis of tissue at the peri-augmentation site, when an acrylic bone cement is used); (4) explicative summaries of the main findings of literature studies on the influence of nine factors (such as powder particle size, powder-to-liquid ratio, and the method used to mix the powder and the liquid) on the values of various properties of IBCs; (5) explicative summaries of the main findings of literature studies on five fundamental matters, such as the aging mechanism of the powder, the thermokinetics of a setting dough, and the influence of the type of IBC used on various ex vivo biomechanical performance measures of VP- and KP-augmented vertebral bodies; and (6) descriptions of topics in six areas for future research, such as the determination of an overall index of the fatigue performance of an IBC and the development of internationally recognized standardized testing protocols to employ when a synthetic cancellous bone void model is used in the rapid in vitro screening of IBCs. The review ends with a summary of the most salient points and observations made. Copyright 2005 Wiley Periodicals, Inc.