Bone wax is a fundamental surgical material used to control bleeding that originates directly from cut or damaged bone surfaces. This material has been a staple in operating rooms for over a century, providing surgeons with a simple, immediate solution for persistent blood loss. Controlling osseous hemorrhage is challenging because the small blood vessels within the bone are encased in rigid tissue, preventing them from constricting naturally. Applying bone wax helps maintain a clear surgical field, allowing for greater precision and reduced overall blood loss.
Defining Bone Wax and Its Composition
Traditional bone wax is a sterile, non-absorbable mixture of ingredients, primarily consisting of purified beeswax. Beeswax typically makes up the largest portion, generally ranging from 70% to 88% of the total composition. The remaining percentage is usually a softening agent, such as isopropyl palmitate, paraffin, or petroleum jelly (Vaseline).
This combination is formulated for malleability. The wax is supplied in a firm stick or patty form and must be softened by kneading before application. The resulting material is chemically inert, meaning it does not participate in biological reactions. Its physical properties allow it to adhere to the bone surface, withstand internal fluids, and remain indefinitely at the implantation site.
How Bone Wax Achieves Hemostasis
The mechanism by which bone wax stops bleeding is purely mechanical, functioning as a physical sealant rather than a biological agent. Unlike many other hemostatic products, it does not rely on or promote the body’s natural blood clotting cascade. When a bone is cut, tiny blood vessels within the bone structure, specifically in the cancellous (spongy) bone, are severed, causing a persistent ooze of blood.
These vessels, which include the Haversian canals and medullary channels, cannot be easily sealed by traditional methods like cautery or suture ligation. The surgeon presses the softened bone wax directly into the bleeding bone surface, physically blocking the open vascular channels. This mechanical plugging creates a physical barrier, or tamponade effect, which prevents blood from flowing out of the bone, achieving immediate hemostasis.
Typical Surgical Applications
Bone wax is widely used across several surgical disciplines where cutting through bone is necessary and bleeding from the cut surface is a concern.
- Cardiothoracic Surgery: Used during a median sternotomy, where the sternum is split to access the heart and lungs, to control bleeding from the cut edges.
- Orthopedic Surgery: Utilized in procedures like total joint replacements, spinal fusions, and fracture fixations where large areas of cancellous bone are exposed.
- Neurosurgery: Relied upon during cranial procedures, such as craniectomy or craniotomy, to manage bleeding from the skull bone edges. It also seals bleeding from emissary and diploic veins in the skull.
Limitations and Non-Absorbable Concerns
Despite its immediate effectiveness, the non-absorbable nature of traditional bone wax presents significant biological drawbacks. Since the body cannot break down the beeswax and its components, the material remains permanently implanted at the surgical site. This foreign substance can mechanically inhibit the process of osteogenesis, which is the formation of new bone tissue. The presence of bone wax acts as a physical barrier to bone-forming cells, osteoblasts, which can delay or prevent proper bone healing and fusion.
The retained material can also trigger a foreign body reaction, leading to chronic inflammation and the formation of granulomas. The inert wax can serve as a potential breeding ground for bacteria, increasing the risk of surgical site infections. Some studies demonstrate a marked increase in infection rates when bone wax is used.
These limitations have prompted the development of modern, bio-absorbable alternatives that aim to provide the same mechanical hemostasis without the long-term complications. One alternative, Ostene, is composed of water-soluble alkylene oxide copolymers designed to dissolve within 24 to 48 hours, allowing the natural bone healing process to begin sooner. Other agents use different resorbable polymers and materials, often designed to be osteoconductive by promoting bone regeneration while they dissolve. These newer materials seek to maintain the benefits of rapid hemostasis while eliminating the biological interference associated with traditional bone wax.