Bone wax

Bone wax is a waxy substance used to help mechanically control bleeding from bone surfaces during surgical procedures.

It is generally made of beeswax with a softening agent such as paraffin or petroleum jelly and is smeared across the bleeding edge of the bone, blocking the holes and causing immediate bone hemostasis through a tamponade effect. Bone wax is most commonly supplied in sterile sticks, and usually requires softening before it can be applied.

History
A note by Victor Horsley published in the British Medical Journal in 1892, described a formulation of “antiseptic wax” having seven parts beeswax, one part almond oils, and 1% salicylic acid. The material was useful for bleeding control in cut or damaged bone where it could be pressed into bleeding pores and channels. The wax was sterilized by boiling and kept in stoppered bottles. This material soon became the standard of care for bleeding control in bone for general orthopedics, craniomaxillofacial and cardio-thoracic surgery where the sternum is often split longitudinally to provide access to the heart.

Action
Ordinary bone wax is effective by virtue of its tamponade action, but is considered to have no active hemostatic properties (i.e. does not activate the blood clotting cascade). In addition, bone wax is not soluble in the bodily fluids and thus remains at the site of implantation for long periods of time if not indefinitely. The portion of traditional bone wax which departs the implant site is most likely carried away through the action of the foreign body response and is associated with  a low grade inflammatory response  at and near the implant site. The residual product can also potentially serve as a nidus for post-operative infection.

Modern formulations
Modern day bone wax is commercially available in substantially non-absorbable formulations similar to Horsley’s original composition, as well as in absorbable/resorbable formats. Most of these waxes are available as a firm wax in stick form that must be softened by kneading prior to use. More recent advances have led to the introduction of a bone hemostat in putty format. Hemostatic putties act via tamponade in the same way as the stick waxes, but are ready to use and eliminate the requirement to soften the product prior to use.

Absorbable bone wax
Hemasorb Resorbable Hemostatic Bone Putty is a sterile, soft, moldable, biocompatible, absorbable material of putty-like consistency. The material is a mixture of calcium stearate, Vitamin E acetate, and liquid surfactant. It is virtually odorless, off-white in color and can be spread easily with minimal adhesion to surgical gloves. The bone putty requires no kneading prior to application and does not soften appreciably at body temperature.

The FDA has recently approved a new water soluble bone hemostasis material called Ostene, which is designed to look and feel like bone wax. This material comprises a sterile mixture of water-soluble alkylene oxide copolymers, derived from ethylene oxide and propylene oxide. These copolymers have a long history in the medical and pharmaceutical fields, and they are considered inert. These compounds are not metabolized, but eliminated from the body unchanged.