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Bone cutting and drilling are important clinical applications that may affect the health and recovery process of patients after their operation. Today, bone cutting and drilling procedures in orthopedic operations are performed with battery and electric surgical motor systems. In this article, we’ll try to explain to you “Heat in Bone Cutting and Drilling. “
During cutting, a heat is generated due to friction between the surgical saw blade / drill bit and the bone. It is known that this heat on the bone negatively affects the healing process after the operation. Obvious side effects of increases in the temperature of the bone during cutting or drilling; impaired bone regeneration (Eriksson AR, Albrektsson T, 1984), bone infection, decreased bone mechanical strength (Christie, 1981) and delayed postoperative recovery. (Pallan, 1960)
Eriksson and Albrektsson found that heating the rabbit cortical bone to 50 ° C for 1 minute caused the loosening implant and significantly reducing osseointegration[1]. (Eriksson AR, Albrektsson T, 1984
[1] * Osseointegration is the direct contact observed between the live bone tissue and the functioning titanium implant material at a light microscope at 100 times magnification.
Heat generation changes according to the speed of the cutting tool and the force applied by the user and this heat has harmful effects on bone tissue. (Thompson, 1958; Pallan, 1960; Matthews and Hirsch, 1972; Larsen and Ryd, 1989). This warming can lead to infection and a decrease in the mechanical strength of the bone (Christie, 1981). Irreversible changes were observed in the mechanical properties of the bone when the bone was heated to 50 ° C (Bonfield and Lı, 1968). The heat of friction that occurs between the saw blade and bone after orthopedic surgery may cause delayed postoperative recovery (Pallan, 1960). Due to the temperature arising from the drilling to the cortical bone, no evidence of repair was seen in the bone even 5 weeks after surgery (Collins,1953). The effect of temperature on the bone has been more clearly defined by Rouiller and Majno (1953) (German article reported in Homer 1961). They exposed the rabbit bones to various temperatures for different periods of time. When exposed to 55 ° C for 1 minute, necrosis of osteocytes was observed within 24 hours. In addition, mechanical deformation with a saw can cause microcracks that can lead to osteocyte apoptosis (cell deaths). (Noble B., 2003)
The most important factors affecting the heat generated are;
– Oscillation / Drilling speed provided by the surgical power tools,
– The force applied by the user,
– Saw blade tooth design and sharpness of tooth / sharpness of drill bit
Matthew P. Kelly et al. (2011) conducted an experiment where the thrust was held constant to see the relationship between the cut speed and the cut volume. According to this experiment, after the blade begins to oscillate, it makes n cut of approximately 3.4 mm3 / s at low speeds such as 80Hz (4800 cpm) and 110Hz (6600 cpm). As soon as the speed increases from 112 Hz (6720 cpm) to 145 Hz (8700 cpm), the cutting volume is doubled from 3.5 to 6.9 mm3 / s. From these data, it can be seen that the relevant speed range is a threshold range for the starting point of the cut. As the speed increases in the cutting process, the cutting volume also increases. Afterwards, James T.P. et al. (2013) also found that increased cutting speed and thrust force decreased the heat generated in the bone.
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)
Krause et al. (1982) conducted a series of clinical studies using a reciprocating saw to measure the force and temperature response on the saw blades during knee and hip arthroplasty. A thermocouple is securely attached to the saw blade to record the saw temperature. They recorded temperatures exceeding 200 ° C without any irrigation. The vertical force exerted by the surgeon is between 4.5 and 7.5 N (Parsa, 2006). James T.P. et al. (2013), in their experiments, applied 15 N and 30 N force and proved that the increase in the force applied together with the speed significantly reduces the heat generated in the bone. When the applied force is high, the temperature decreases because the blade is in contact with the bone for less time.
In a study testing low piercing forces, cortical temperatures increased as the forces increased from 1.5 to 4 N (Abouzgia and James, 1997). After that they discovered that as the forces continued to increase from 4 N to 9 N, cortical temperatures decreased. However, various researchers such as Matthews and Hirsch (1972), Abouzgia and Symington (1996), Abouzgia and James (1997) and Brisman (1996) have reported that cortical bone temperatures are inversely related to drilling force. All of them observed a significant decrease in maximum cortical temperatures as a result of the increase in force. Matthews and Hirsch (1972) tested forces ranging from 20 N to 118 N and found that by increasing the force, bone temperatures and their duration above 50°C decreased, in agreement with Bachus et al (2000). Although the exact reason for this temperature decrease is vague, a higher force may reduce the time required to penetrate the cortex of the bone (Parsa, 2006).
A multi-factor study of drilling parameters shows that an increase in drilling speed to a certain level is associated with a higher temperature increase in bone, while an increase in feed force generally resulted in a lower temperature increase. (Augustin G. et al, 2008)
Toksvig-Larsen et al. (1992) compared different saw blades (Figure 1) with different designs and showed that the saw geometry is not decreasing the temperature to below the critical level (47 – 50 ° C). Table 1 shows the results for cutting bovine bone using different saw blades.
Regardless of the extensive usage of saw blades and surgical power tools in surgeries, there are few researchers investigating saw blade performance in experimental models (Krause et al., 1982; Wevers et al., 1987; Toksvig-Larsen et al., 1990; 1992; Ark et al., 1997a; 1997b; 1997c). For any orthopedic operation, the durability of the blade has been a major concern for all surgeons (Ark ve diğerleri, 1997b). In addition, blunt blades require the application of extra force, which can contribute to excessive friction heat (Allan et al., 2005). The abrasion of the saw blade has been linked to two different criteria. Firstly, it is assumed that the reuse of the blade blunts the blade, and secondly, it is assumed that the accidental contact of the blade with a metal jig or cutting guide during surgery may be the main cause of the blunt blade. Wevers et al. (1987) found that half of the saw blades taken from the operating room were seriously damaged. They stated that reuse of saw blades may decrease cutting efficiency. They also found that the force required to cut the cortical bone using a blunt saw blade (32.08 N) was about five times higher than the force required with new blades (6.75 N). This result is consistent with the findings of Matthews and Hirsch (1972) investigating the in vitro drilling process in the human cortical femoral bone. (Worn drill bits cause huge temperature increases compared to new drill bits)
The use of a new drill bit is one of the most important factors to consider in drilling efficiency in any orthopedic surgery as much higher temperature increase were recorded when a worn drill bit was used (Matthews and Hirsch, 1972). Allan et al. (2005) recommend that the cutting blade be examined with shadow chart or SEM after each use. In their study, they examined the effect of drilling bit abrasion on the temperature and concluded that the tips should be discarded after a single use. But when we bring back to reality, most hospitals do not discard saw blades and drills bits after one use simply from an economic point of view. (Parsa, 2006)
In the study of Hamid Khalili Parsa (2016), he shows the abrasion of the saw blade and the damage in the cutting tooth after 5 and 15 trials (number of cuts). (Figures 2,3,4,5 and 6)
Read the article What Are The Advantages Of Computer-Assisted Orthopedic Surgery (CAOS) Systems?
Click here to read more articles about Heat in Bone Cutting and Drilling via PubMed website.
Figure 1. Different Saw Blade Designs, Parsa (2006)
Figure 2. SEM image of new unused blade in view adjacent to the cutting edge (Parsa, 2006)
Figure 3. SEM image of cutting edge of new unused blade (Parsa, 2006)
Figure 4. SEM image of used blade (5 trials) in view adjacent to the cutting edgeKullanılmış bıçağın (5 kesi) kesme ucunun karşıdan SEM fotoğrafı (Parsa, 2006)
Figure 5. SEM image of cutting edge of used blade (5 trials) (Parsa, 2006)
Figure 6. Cutting edge after 15 trials (Parsa, 2006)
Table 1. Maximumtemperature recorded while using various saw blades in bovine bone cutting, Parsa (2006)
