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In drilling and cutting processes related to the bone, the temperature of the bone must be kept under control. Studies have shown that the starting threshold of bone necrosis (death of bone cells) is 47 – 50 ° C. (Eriksson AR, Albrektsson T, 1984; Bonfield ve Lı, 1968; Rouiller ve Majno, 1953; Thompson, 1958; Pallan, 1960; Matthews ve Hirsch, 1972; Larsen ve Ryd, 1989) In these studies, also the negative effects of bone necrosis are stated. (Impaired bone regeneration, bone infection, decreased bone mechanical strength and delayed postoperative recovery) In drilling operations, the revolution speed of the surgical power tools (rpm) and the sharpness of the drill bits are among the important factors affecting the heat.
Users and hospital procurement departments may think that high-speed drill handpiece are stronger and facilitate the drilling process. However, some studies show that the speed increases the temperature in the drilling area until it reaches a certain value. This temperature increase can result in the irreversible death of bone cells. This bone necrosis causes the patient to recover delayed, the contact between the bone and the implant (osseointegration) to decrease, and thus the implant to loosen.
Today, the drilling handpiece speeds of the manufacturers producing surgical power tool systems for large bones suitable for trauma operations vary between 500 rpm and 1.500 rpm. The reason for the difference between them is that some manufacturers also introduce high speed as an advantage in their marketing activities.
Thompson (1958) examined low drilling speeds, temperature increase according to the speed and tissue damage in the drilling operations. He tried different drilling speeds on the dog jaw bone and examined bone reactions. While the temperature at 125 rpm was 39 ° C, it exceeded 65.5 ° C at 1000 and 2000 rpm speeds. Therefore, in accordance with Pallan (1960), he proposed a drilling speed of 500 rpm to minimize the thermal damage and histological response of the bone. Abouzgia and James (1997) found that the maximum temperature rise is rapidly decreasing in free running speeds from 27,000 rpm to 97,000 rpm. Apart from Matthews and Hirsch’s studies (1972), there seems to be a general agreement that the temperature rise increases with the piercing speed until about 10,000 rpm. (Parsa, 2006)
Figure 1 – The graphical form of the values given in the studies above is as follows. (It contains approximate values.)
The drill bits used for drilling operations are generally used over and over again until they become blunt and ineffective. Since the sharpness of the drill bit is one of the most important factors in drilling efficiency, blunt drill bits require extra force or more revolution speed. This contributes to the excessive friction heat generated during the preparation of the screw holes. Massive increases in temperature impair bone regeneration around the screws and can cause failure of internal fixation. (W. Allan et al., 2005)
The damages to the drill bits after a certain number of uses can be seen at below.
Click here to see ACF Surgical Drill and its technical specs.
Figure 2 – Photographs of the three drills, side view and tip. The upper photographs are of the new drill, the centre photographs are of the drill that had drilled 600 holes, and the lower photographs are of the drill from theatre.(W. Allan et al., 2005)
Click here to reach more articles about Speed of Surgical Drills via PubMed website.
In researches for surgical drill motors, the temperature rise increases with the piercing speed until about 10,000 rpm. As a result of the research of Palan (1960), he proposed a drilling speed of 500 rpm to prevent the temperature from rising above 47 – 50 ° C. But it is a sufficient drilling speed for orthopedics and trauma operations with a new drill bit.
Considering the economic conditions of the countries, it will be very costly to use a new drilling bit for each operation in all hospitals. Therefore even if these drill bits are disposable, they are sterilized and reused. In addition to disposable drill bits, there are also drill bits released to the market as reusable. But hospitals must have specially created instructions and procedures for reusable drill bits. After each operation the drill bits must be reconditioned in accordance with this procedure and instructions to ensure their first use performance.
When we consider that a new drill bit is not used in every operation, a balance must be established in which the made a drilling process at the lowest possible speed in large bones and the drill bits are changed without waiting for becoming blunt too much. At this balance, the drill speed should be a maximum of 1,000 rpm for not to exceed the critical temperature. Instead of preferring drills above this revolution speed, the drill bits should be changed.
1) Abouzgia, M. B., James, D. F., (1997). Temperature rise during drilling through bone. The International Journal Of Oral & Maxillofacial Implants 12, 342-353.
2) Allan, W., Williams, E. D., Kerawala, C. J., (2005). Effects of repeated drill use on temperature of bone during preparation for osteosynthesis self-tapping screws. British Journal of Oral and Maxillofacial Surgery 43, 314-319.
3) Bonfield, W., Li, C. H., (1968). The temperature dependence of the deformation of bone. Journal of Biomechanics 1, 323-329.
4) Eriksson AR, Albrektsson T. The effect of heat on bone regeneration: an exper-imental study in the rabbit using the bone growth chamber. J Oral MaxillofacSurg 1984;42:705–11.
5) Matthews, L. S., Hirsch, C., (1972). Temperatures measured in human cortical bone when drilling. The Journal Of Bone And Joint Surgery.American Volume 54, 297-308.
6) Larsen, S. T., Ryd, L., (1989). Temperature elevation during knee arthroplasty. Acta Orthopaedica Scandinavica 60, 439-442.
7) Pallan, F. G., (1960). Histological changes in bone after insertion of skeletal fixation pins. Journal Of Oral Surgery, Anesthesia, And Hospital Dental Service 18, 400-408.
8) Parsa, Hamid Khalili. An Investigation into the Temperature Distribution Resulting from Cutting of Compact Bone Using a Reciprocating Bone Saw. 2006: 26-27.
9) Rouiller, C., Majno, G., (1953). Morphologische und chemische Untersuchungen an Knochen nach Hitzeeinwirkung [German] [Morphological and chemical studies of bones after the application of heat].
10) Thompson, H. C., (1958). Effect of drilling into bone. Journal Of Oral Surgery, Anesthesia, And Hospital Dental Service 16, 22-30.
