A bone flap is a section of bone, typically from the skull, temporarily removed by surgeons during certain brain operations. This allows access to the brain underneath. Specialized tools are used for its precise removal. It is a foundational step in various neurosurgical procedures.
Surgical Procedures Requiring a Bone Flap
The temporary removal of a bone flap is a key step in a procedure known as a craniotomy. This procedure is performed for various medical reasons, including the removal of brain tumors, the repair of aneurysms, or the evacuation of blood clots (hematomas). During a craniotomy, the bone flap is cut and lifted to expose the brain, allowing surgeons to address the underlying condition.
A related procedure, a decompressive craniectomy, also involves the removal of a bone flap. This is typically performed to relieve severe pressure on the brain, often due to swelling from a traumatic brain injury or stroke. Unlike a standard craniotomy, the bone flap in a decompressive craniectomy is not immediately replaced, allowing the brain room to swell without causing further damage.
Handling and Fate of the Bone Flap
After a craniotomy, the bone flap is typically reattached to the skull at the end of the same surgical procedure. Small plates and screws, often made of titanium, secure it into its original position. Over time, the reattached bone fuses with the surrounding skull, similar to how a fractured bone heals.
In cases of decompressive craniectomy, where the bone flap is not immediately replaced, it must be preserved for later re-implantation. Common methods for preserving the bone flap include cryopreservation in a bone bank, or storing it within a subcutaneous pocket in the patient’s own body, often in the abdomen. This delayed re-implantation procedure is called a cranioplasty, which restores the skull’s protective barrier and can improve the patient’s appearance and neurological function.
Types of Bone Flaps and Their Materials
When a bone flap is used in surgery, the preferred material is usually the patient’s own bone, known as an autologous bone flap. Autologous bone offers excellent compatibility and has the potential to integrate with the surrounding skull.
However, there are instances where the patient’s original bone flap cannot be used for re-implantation, such as if it is damaged, infected, or if there’s a risk of complications like resorption. In these situations, synthetic or alloplastic materials are used for cranioplasty. These materials include titanium mesh, polyetheretherketone (PEEK), or polymethylmethacrylate (PMMA), chosen for their strength, biocompatibility, and ability to be customized to fit the skull defect.