Technical Note – Friction at Surgical Instrument and Bone Interface

Testing rig on Bose ElectroForce

Jugal Parekh, one of JJD’s directors, recently published a technical note in the Journal of Engineering in Medicine. Click here to be redirected to the article page.

The purpose of the research was to select the most appropriate material for the base of an orthopaedic surgical instrument, which is placed on the curved bone surface during the surgical procedure. The instrument was being redesigned to improve its usability.

An interesting aspect of the research, apart from synthetic blood solution, and the novelty of the study itself, was the custom designed testing rig – two nylon pulleys were utilised, and fixed on an adjustable platform. The platform was connected to a Bose ElectroForce testing machine, and the bone was pulled using a nylon fishing line. The testing protocol was in compliance with ASTM.

The abstract of the article is available below, and you may find the article here

Title – In vitro investigation of friction at the interface between bone and a surgical instrument

Abstract – This study investigated the friction between surgical instruments and bone to aid improvements to instrument design. The bases of orthopaedic surgical instruments are usually made of metal, especially stainless steel. Silicone elastomer was chosen as an alternate biocompatible material, which would be compliant on the bone surface when used as the base of an instrument. The coefficient of static friction was calculated at the bone/material interface in the presence of a synthetic solution that had a comparable viscosity to that of blood, to assess the friction provided by each base material. Three types of silicone elastomers with different hardnesses (Shore A hardness 23, 50 and 77) and three distinct stainless steel surfaces (obtained by spark erosion, sand blasting and surface grinding) were used to assess the friction provided by the materials on slippery bone. The bone specimens were taken from the flattest region of the femoral shaft of a bovine femur; the outer surfaces of the specimens were kept intact. In general, the stainless steel surfaces exhibited higher values of coefficient of static friction, compared to the silicone elastomer samples. The stainless steel surface finished by spark erosion (surface roughness Ra  = 8.9 ± 1.6 µm) had the highest coefficient value of 0.74 ± 0.04. The coefficient values for the silicone elastomer sample with the highest hardness (Dow Corning Silastic Q7-4780, Shore A hardness 77) was not significantly different to values provided by the stainless steel surface finished by sand blasting (surface roughness Ra  = 2.2 ± 0.1 µm) or surface grinding (surface roughness Ra  = 0.1 ± 0.0 µm). Based on the results of this study, it is concluded that silicone could be a potentially useful material for the design of bases of orthopaedic instruments that interface with bone.

Testing rig on Bose ElectroForce

 

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