Platelet-Rich Fibrin, or PRF, is a concentrate made from a patient’s own blood that is used to promote healing. The creation of this material depends entirely on a specific centrifugation process. The speed and duration of the centrifugation are primary variables that determine the quality and viability of the final fibrin clot.
The Science of Centrifugal Separation
Centrifugation is a process that uses centrifugal force to separate components of a fluid. In the context of creating PRF, a blood sample is spun at high speeds, separating its components based on their density. The objective is to concentrate platelets and certain white blood cells (leukocytes) within a fibrin matrix, while separating them from the heavier red blood cells and the lighter, platelet-poor plasma. This separation allows for the formation of a clot rich in growth factors.
The force applied during this process is measured in Relative Centrifugal Force (RCF), also known as G-force. While Revolutions Per Minute (RPM) is a common setting on a centrifuge, RCF is the more scientifically accurate and standardized measurement. This is because the actual force applied (RCF) depends on the radius of the centrifuge’s rotor, meaning the same RPM setting on two different machines can produce different forces. For PRF, lower G-forces are used compared to other blood concentrates like Platelet-Rich Plasma (PRP) to prevent cellular damage and to allow for the natural formation of the fibrin scaffold.
Standard PRF Centrifugation Protocols
The specific speed and time of centrifugation are tailored to create different types of PRF, each with unique clinical applications. The protocols developed by Dr. Joseph Choukroun are widely recognized and serve as a basis for many current practices.
L-PRF (Leukocyte- and Platelet-Rich Fibrin)
The original protocol for L-PRF, sometimes called Choukroun’s PRF, involves centrifuging blood at approximately 2700 RPM for 12 minutes. This speed generates a force of around 700 RCF. This process is designed to create a robust, solid fibrin clot containing a high concentration of both platelets and leukocytes. This clot can be used as a membrane or plug in various surgical sites to aid in tissue regeneration. The 12-minute duration allows for the complete separation of blood layers before the sample fully clots.
A-PRF+ (Advanced-PRF+)
Research revealed that the high G-forces used in the L-PRF protocol could lead to an uneven distribution of cells. In response, the Advanced-PRF (A-PRF) protocol was developed, using a lower centrifugation speed to create a more homogenous clot with better cell preservation. A common A-PRF+ protocol uses a speed of about 1300 RPM for 8 minutes, which corresponds to an RCF of roughly 200g. This gentler process results in a PRF clot where platelets and leukocytes are more evenly distributed throughout the fibrin matrix, theoretically enhancing its regenerative potential.
i-PRF (Injectable-PRF)
To create a liquid, injectable form of PRF, an even gentler and shorter protocol is required. The i-PRF protocol involves spinning blood at a very low speed, around 700 RPM, for just 3 to 4 minutes. This generates a minimal G-force of approximately 60 RCF. This short, slow spin does not allow for the formation of a solid fibrin clot, instead producing a liquid plasma rich in platelets and leukocytes that can be injected directly into tissues.
Critical Factors Beyond Speed and Time
While precise centrifuge settings are foundational, other factors significantly influence the final quality of the PRF clot. The time between drawing the blood and starting the centrifugation, often called the “vein-to-spin” time, is a primary factor. Delays can allow the blood to begin clotting before it is properly separated, compromising the integrity of the final product.
The type of blood collection tube used also plays a direct role. PRF production requires tubes without anticoagulants, as the goal is to facilitate natural clotting. Early protocols used glass tubes, as the glass surface helps to activate the clotting cascade. Newer protocols, such as for A-PRF+, may use silica-coated plastic tubes to achieve a similar effect. Conversely, the production of i-PRF often uses specific plastic tubes that do not have coatings, as their less activating surface helps keep the final product in a liquid state for a short period.
Consequences of Incorrect Centrifuge Settings
Deviating from established protocols can lead to a clinically less effective product. The physical characteristics and biological composition of the PRF clot are directly linked to the precision of the centrifuge settings, and failure to adhere to correct parameters diminishes its healing capabilities.
If the centrifuge is spun too fast or for too long, the resulting G-forces can be excessive. This can physically damage the delicate platelets and leukocytes, rendering them less effective. It also tends to create a small, overly dense, and reddish clot because red blood cells are forced into the fibrin matrix. Many of the desired cells can become pelleted at the very bottom of the tube, separated from the usable clot entirely.
Conversely, spinning the centrifuge too slow or for an insufficient duration leads to incomplete separation of the blood components. This results in a poorly formed, “soupy” clot that lacks structural integrity. The concentration of platelets and growth factors in such a clot is significantly reduced because they have not been adequately separated from the red blood cells and platelet-poor plasma.