Effect of tool and drilling parameters on surface topography of bone drilled holes: An in vitro study

Abstract

Background: Orthopedic bone drilling is one of the major mechanical process performed by the orthopedic surgeons during the orthopedic surgery. It is a necessary action to fixate the implants during the direct method of fracture treatment. The bone encountered some extra mechanical forces and residual stresses during drilling which can harm the already damaged bone. The Non-favorable combination of drilling parameters affect the surface topography of the drilled walls holes. The surface around the drill site is the crucial part which need to be focused for the better bone screw joint. Methodology: Heavy rough surface, having more Rmax value definitely give lower pull-out strength because of loose grip of screw and bone. So the surface properties of bone drilled samples with different combination of drilling parameters (rotational speed, Feed rate and type of tool) is to be studied, targeting the lower surface roughness and better surface topography. The parameters i.e. rotational speed (600, 1200, 1800, 2400 rpm) and feed rate of tools (10, 20, 30, 40 mm/min) are studied at four levels and type of tool at two levels (standard twist drill and cylindrical abrasive tool). Experimental design matrix of mixed array L16 employed for better observation of results using less attempts. Results: These value of surface roughness use to solve taguchi technique for lower-the better results. Results of taguchi show that with rpm 600, feed rate 10mm/min and standard drill bit tool gives the best results Analysis of variance for measured surface roughness describes the percentage contribution of each parameters and significance on the results. The results have been confirmed by finding confidence interval for optimize results and scanning electron microscopy (SEM) supports the roughness results. Conclusion: Surface roughness is influenced by all the contributing parameters very significantly. Drilling with standard drill bit, steady and slow rotational speed with controlled feed rate gives better surface roughness and topography.