A bone mill processes bone tissue into small, uniform particles for use in grafting procedures. Surgeons use this tool to prepare harvested bone material, known as a bone graft, which is introduced into a patient’s body to repair or augment existing bone structure. The mill transforms solid bone into a granular consistency, making the material suitable for filling defects and promoting biological integration. This preparation is a standard step in reconstructive surgeries requiring the patient’s own bone (autograft) or donor bone (allograft).
Why Bone Graft Material Needs Processing
Large, solid pieces of bone are inadequate when a surgeon needs to fill an irregular defect or promote bone fusion across a joint. Unprocessed bone does not pack efficiently, leaving gaps that compromise the repair site’s structural integrity. Furthermore, a large solid piece of bone has a limited surface area for contact with the surrounding host tissue.
Milling the bone creates morselized bone, a collection of small, uniform particles. This granular material can be tightly impacted into an irregularly shaped void, allowing for complete filling and mechanical stability. Reducing the bone to small particles significantly increases the overall surface area, which is important for the biological mechanisms of healing, including osteoconduction and osteoinduction. The increased surface area allows cells and blood vessels to more easily penetrate and integrate with the graft material, promoting new bone growth.
The Mechanics of Bone Milling
The process of bone milling involves several components working together to achieve a consistent particle size. The mill typically consists of a housing, a cutting mechanism, and a collection tray. A solid piece of bone is placed into the mill’s hopper.
The cutting mechanism, often a rotating drum or set of blades, reduces the bone into small fragments. These elements are designed to mill the bone rather than crush it, ensuring the particles retain an intact trabecular structure beneficial for grafting procedures. Modern mills often use a single-pass cutting action to minimize heat generation and preserve the biological viability of the graft material.
Bone mills can be either manually operated with a hand crank or powered by a dedicated motor or surgical console. Manual mills often employ a double-action mechanism to provide mechanical advantage for grinding dense cortical bone. The milled particles pass through a sizing mechanism, such as a sieve or interchangeable milling drum, which ensures the final product is a consistent, clinically useful size. Different drum sizes customize the particle size for various surgical indications, such as spinal fusion or hip revision surgery.
Surgical Procedures Utilizing Milled Bone
Milled bone is used across several surgical disciplines where bone volume restoration or structural fusion is necessary. In orthopedics, morselized bone graft is frequently used in revision joint replacement surgeries, particularly in the hip, to address bone loss within the acetabulum. The granular graft is tightly impacted into the defect to restore bone stock and provide a stable foundation for the new implant. Spinal fusion procedures also rely on milled bone, which is packed around the vertebrae to promote a solid bony bridge and stabilize the spinal segment.
Milled bone plays a role in dental and maxillofacial surgery, where the goal is to build up the jawbone to support dental implants. Procedures such as ridge augmentation, which corrects height or width deficiencies in the jaw, and sinus lifts, which add bone to the upper jaw, utilize morselized grafts as a scaffold. The prepared graft material fills the space, enabling the patient’s natural bone to grow into the matrix and create a strong foundation for future dental work.