Aerosol morphology and particle size distribution in orthopaedic bone machining: a laboratory worst-case contamination simulation. Is high-speed bone machining potentially harmful by pollution and quality schemes and what measures could be taken for prevention?

AIM OF THE STUDY: High-speed bone machining devices with irrigation fluid were used in surgery to spread aerosols and toss tissue particles of varying morphology into the operating room. Based on measurements taken on a phantom object, the shape, size, and spatial contamination distribution of such particles were assessed. METHOD: Cadaveric femoral heads were continuously machined with a spherical bur, manually held at a fixed attack angle. The irrigation fluid used during bone machining was enriched with bacteria to act as a tracer to quantify the spatial contamination. A vertical board equipped with snippets served as a phantom object to assess contamination load and morphology of airborne particles. RESULTS: Eight-nine percent of the particles had a non-circular cross section. The detected particle size ranged across six orders of magnitude, from 0.006 to 4 mm2 with a median particle size of 0.125 mm2. The CFU counts observed after the standard machining time ranged from 7 to 240, with a median of 2 CFUs. The highest median contamination was seen at the upper right corner of the phantom. DISCUSSION: The experiments show that contaminating particles of a wide variety of shapes and sizes are part of the aerosol created by high-speed burring. While protection of personnel and equipment is always important, surgical helmets should be worn, especially at contamination hotspots, and gloves should be replaced at the end of machining. Sensitive instruments and measuring devices-such as optical sensors-should also be protected effectively, as the optical measurement may be obstructed by aerosol particles.

The spatial distribution of aerosols in high-speed bone burring with external irrigation.

It is well-known that the use of high-speed burring devices with irrigation used in bone surgery produces aerosols, and can toss tissue particles into space. The aim of this study was to assess the spatial vertical contamination in the sterile operation field while using a high-speed cutting device at various locations. A fresh porcine knee was resected for 10 min with a high-speed burring device. To determine the spatial contamination distribution bacteria were used as a tracer. In this novel method for detecting environmental contamination droplets of the contaminated irrigation solution were collected on vertically mounted Petri dishes and the number of colony-forming units was counted. Contamination of varying intensity was observed throughout the room. The highest contamination was found perpendicular to the bur rotation axis in a distance 0.5 m from the bur, at a height of 1.4 m. Around this spot, colony-forming units count isotropically drops to less than 100 CFUs at an area of 0.5 m in diameter. The contamination decreases with increasing distance to the bur head and a main direction of contamination was identified. Placing critical sterile objects in the highly contaminated space during and after bone resection procedures should be avoided whenever possible.