Personalized Surgical Instruments

Additive Manufacturing (AM) has been called the Second Industrial Revolution [1]. This technology allows a three dimensional shape defined in digital space to be directly rendered into a tangible object. The transformation from virtual object to tangible object by AM is fast and inexpensive compared to most traditional fabrication approaches. Thus, the revolutionary aspect of additive fabrication is not uniform mass production of the first Industrial Revolution, but mass customization of manufactured devices [2].The history of surgical instruments, such as the forceps, shows an evolution of devices meant to augment the dexterity of the human hand [3]. Materials used for these instruments followed the technology of the era, bronze instruments in the Bronze Age giving way to iron instruments in the Iron Age. By the 17th Century surgical instruments were constructed by skilled smiths and were often adorned with custom decoration [4]. Instruments were customized to the feel and tastes of the commissioning surgeon. In the 19th century, surgical instruments became catalogued and standardized in form. With consideration of sepsis, instruments evolved into the present stainless steel designs in the early 20th century [4].Through mass customization, surgical instruments can be inexpensively tailored to the specific needs and tastes of a surgeon. Instruments can be quickly and economically printed in a biocompatible polymer using AM technology. Conceivably, a surgeon would have their hand dimensions digitized for reference, and then standard instrument designs could be digitally generated for a custom tailored fit. Furthermore, as a surgeon gained experience or developed new procedures, the instruments could be customized to suit their individual needs. As opposed to mass produced instruments in a medical supply catalog, a surgeon would call upon a personal catalog of unique instruments in virtual representation, and produced on demand.This concept of personalized surgical instruments was investigated as a pilot demonstration of mass customization and on-demand fabrication by a team from the Naval Postgraduate Dental School (Bethesda, MD), Stratasys (Eden Prairie, MN), and the Service Chiefs Fellowship Program from the Defense Advanced Research Projects Agency (Arlington, VA). Custom spring forceps and pivot forceps devices were digitally designed, fabricated, and then evaluated using a surgical simulator.Digital models of a spring forceps and a central pivot forceps were created in SolidWorks 2012 computer aided design (CAD) software (Dassault Systèmes SolidWorks Corp., Waltham, MA), running on a Microsoft Windows 7 based workstation. The models were parameterized with key dimensions (arm lengths, finger loop positions, etc.). Custom designs were generated by simply changing values of the key dimensions within the CAD application.Instruments were sized to fit the hands of a clinician and tailored to expressed personal tastes and preferred technique. Driving dimensions were modified in the CAD model to generate a unique embodiment of an instrument. Figure 1 shows the CAD model with driving dimensions for tailoring a hemostat. Once modified to the clinician's requests, the digital CAD model was exported, and saved, in the AM standard.STL file format.Instruments were printed in a modified ABS thermoplastic using a material extrusion 3D printer. The basic instrument designs were modified to replicate the mechanical performance of standard instruments (usually fabricated from stainless steel). Adaptation of the designs was necessary to accommodate the properties of presently available materials; these involved thickening of the crossection of the forceps arms, and redesign of simple pivot hinges, to provide adequate mechanical strength and stiffness.Instruments were fabricated directly from the.STL digital files using a Dimension uPrint Plus SE desktop material extrusion 3D printer (Stratasys, Eden Prairie, MN). Files were prepared for fabrication using CatalystEX 4.3 (Stratasys, Eden Prairie, MN) 3D printing software running on a Microsoft Windows 7 based laptop computer. A developmental ABSi-Ag material from Stratasys was used to print examples of the instruments. This material is currently under development as a potentially biocompatible and bacteriostatic material for medical applications.A customized tissue forceps and needle driver were designed to a single test clinician's personal specifications, fabricated, and tested. A subjective evaluation was performed by performing surgical procedures and suturing an incision on a Cut Suit surgical simulator (Strategic Options, San Diego, CA).A one piece, spring style tissue forceps design was created in CAD. The design was tailored to fit the hand of a clinician, and further tailored in stiffness to provide the desired feel during closure. A desire was expressed for an instrument that could be effectively manipulated by palm pressure. Interlocking triangular teeth were added to the tip of the instrument, at the preference of the clinician. The final instrument design is depicted in Figure 2.Simple gripping and holding tests were performed to evaluate the design; feedback from the clinician drove further modifications. The stiffness of the arms, length of the arms and the angle of the arms at closure were modified as per request of the clinician. Initially, the forceps were judged to be too stiff. Compliance was increased by narrowing the crossection of the loop end. Forceps arm stiffness was increased by thickening the arm crossection near the tip and teeth. The length of the forceps arms was customized to leave approximately 1 inch length beyond the tips of the fingers, and the angle between the arms at closure was also opened. Changing the pattern of material stand deposition in the material extrusion process affected the instrument feel reported by the clinician. Special toolpaths were developed by Stratasys to improve the durability and feel of the tissue forceps.A two piece, hinge pivot forceps design was also created in CAD. A standard pivoting arm design, common to hemostats, was modified for production in ABS plastic. A tapered