Hollow Notched K-Wires for Bone Drilling With Through-Tool Cooling

Review on 3D printing techniques for cutting tools with cooling channels

This review paper critically emphasizes the possibilities and recent developments for producing high-performance conventional cutting tools that are in demand in the traditional machining industry. These cutting tools are considered for use in traditional machining of materials that provide a high strength-to-weight ratio for various applications with high precision. This review focuses on the machinability of turning, milling, drilling, and other special tools manufactured using various additive manufacturing methods. The materials and methods used are also studied, enabling us to understand the vast requirements of tool materials and the additive manufacturing methods available for production. The critical suggestions discussed would establish a platform for the selection of printing methods and printing strategies to develop cutting tools with complex internal geometries.

Highly Adhesive Antimicrobial Coatings for External Fixation Devices

Pin site infections arise from the use of percutaneous pinning techniques (as seen in skeletal traction, percutaneous fracture pinning, and external fixation for fracture stabilization or complex deformity reconstruction). These sites are niduses for infection because the skin barrier is disrupted, allowing for bacteria to enter a previously privileged area. After external fixation, the rate of pin site infections can reach up to 100%. Following pin site infection, the pin may loosen, causing increased pain (increasing narcotic usage) and decreasing the fixation of the fracture or deformity correction construct. More serious complications include osteomyelitis and deep tissue infections. Due to the morbidity and costs associated with its sequelae, strategies to reduce pin site infections are vital. Current strategies for preventing implant-associated infections include coatings with antibiotics, antimicrobial polymers and peptides, silver, and other antiseptics like chlorhexidine and silver-sulfadiazine. Problems facing the development of antimicrobial coatings on orthopedic implants and, specifically, on pins known as Kirschner wires (or K-wires) include poor adhesion of the drug-eluting layer, which is easily removed by shear forces during the implantation. Development of highly adhesive drug-eluting coatings could therefore lead to improved antimicrobial efficacy of these devices and ultimately reduce the burden of pin site infections. In response to this need, we developed two types of gel coatings: synthetic poly-glycidyl methacrylate-based and natural-chitosan-based. Upon drying, these gel coatings showed strong adhesion to pins and remained undamaged after the application of strong shear forces. We also demonstrated that antibiotics can be incorporated into these gels, and a K-wire with such a coating retained antimicrobial efficacy after drilling into and removal from a bone. Such a coating could be invaluable for K-wires and other orthopedic implants that experience strong shear forces during their implantation.

Comparison of k-wire insertion using oscillatory and unidirectional drilling modes under constant thrust force

Heat generation during the Kirschner wire (K-wire) insertion process, under either unidirectional or oscillatory drilling mode, places bone at risk of thermal osteonecrosis which can lead to infection. There is a lack of quantitative understanding of the heat generation difference between the two drilling modes and knowledge of optimal thrust force level under each mode is missing. The goal of this study is to investigate the effects of drilling modes and thrust force levels on the bone drilling outcomes. Controlled machine-based constant thrust force K-wire insertion experiments were conducted with key process parameters monitored and compared quantitatively. Statistical analysis showed that the oscillatory mode consumed 2.6 times more electricity than the unidirectional mode but generated 53% less thermal energy and 23% lower peak temperature. However, the oscillation also led to 18% higher peak torque in the transient drilling stage and 23% shallower drilling depth. The optimal choice of the drilling mode depends on specific surgical needs to minimize bone damage (control of peak temperature vs. exposure time and torque control). Heat generation was dominated by the torque and corresponding rotational power under both modes. To minimize the bone temperature while keeping high drilling speed efficiency, a moderate thrust force is preferred under the unidirectional mode to balance between feed force and compressed debris resistance. For oscillatory mode, a small thrust force to keep the K-wire engaged with the bone is optimal.

Surgical Drill Bit Design and Thermomechanical Damage in Bone Drilling: A Review

As drilling generates substantial bone thermomechanical damage due to inappropriate cutting tool selection, researchers have proposed various approaches to mitigate this problem. Among these, improving the drill bit design is one of the most feasible and economical solutions. The theory and applications in drill design have been progressing, and research has been published in various fields. However, pieces of information on drill design are dispersed, and no comprehensive review paper focusing on this topic. Systemizing this information is crucial and, therefore, the impetus of this review. Here, we review not only the state-of-the-art in drill bit designs-advances in surgical drill bit design-but also the influences of each drill bit geometries on bone damage. Also, this work provides future directions for this topic and guidelines for designing an improved surgical drill bit. The information in this paper would be useful as a one-stop document for clinicians, engineers, and researchers who require information related to the tool design in bone drilling surgery.

Thermographic assessment of heat-induced cellular damage during orthopedic surgery

The heat generated during orthopedic surgery can cause thermal damage to bone cells, leading to cell necrosis, death, and bone resorption. In this study, the drill-exit surface in cortical bone drilling was firstly investigated by infrared thermography to understand the thermal characteristics of bone cutting. In order to mimic the short-term thermal condition of high temperature during surgical cutting, the osteoblasts were exposed to heat shock for short periods of time to investigate the effect of cutting heat on the bone. Necrosis and apoptosis were investigated immediately after heat shock for 2 s, 5 s, and 15 s at 50 °C, 60 °C, 70 °C, and 80 °C, respectively. The cells were then incubated for 4 days at 37 °C and analyzed by fluorescein annexin V-FITC/PI double staining. The temperature and heat-duration were precisely controlled by a novel heating approach. In comparison to the control group (37 °C), immediate necrotic and apoptotic response to heat shock was found in cells exposed to 50 °C for 5 s (11.8%, p<0.05); however, the response was negligible in cells exposed to 50 °C for 2 s. In addition, recovery was found in the group exposed to 50 °C and 60 °C for 2 s (p ≤ 0.05) after incubation for 4 days. Cell damage depends on the magnitude and duration of heat exposure. These findings provide fundamental knowledge for future developments of surgical tool design and cutting methods.