Why customisation and speed are top additive manufacturing benefits for orthopaedics
The American College of Surgeons has called for hospitals to “minimise, postpone or even cancel” elective procedures until the coronavirus (Covid-19) outbreak slows down. Hospitals and surgical centres are beginning to embrace this idea as a way to effectively deal with the impact of this unprecedented global pandemic on society. This response may significantly affect the orthopaedic surgery community and its suppliers, as many orthopaedic procedures are considered elective. However, it is likely too soon to fully understand the impact this crisis will ultimately have on the orthopaedics market. Despite this situation, device manufacturers still need to explore new, inventive and cost-effective ways to continue moving the industry forward.
One such opportunity is to drive innovation and improve medical outcomes with additive manufacturing of surgical instruments and implants using thermoplastics. The two methods – Fused Filament Fabrication (FFF) and Selective Laser Sintering (SLS), offer complementary approaches. The first is ideal for low volume, customised parts with complex geometries that can be produced at or close to the point of care. The second lends itself to centralised production of higher-volume components with complex geometries. Together, these technologies offer the orthopaedic industry the proven advantages of polymers over traditional metal (lighter weight, high-performance properties, support for bone ingrowth) plus the unique capabilities of additive manufacturing, including patient/surgeon personalisation and production of complex designs.
Printing surgical instruments
Additive manufacturing of orthopaedic components offers the ability to move beyond standard designs to provide instruments that are customised to the surgeon, the procedure and/or the patient. Templates, guides and fixtures can potentially be designed and printed at or near the point of care using small FFF printers. These machines build a part in layers through the deposition of heated, extruded plastic filament.
In SLS, a laser heats a powdered material to just above its melting point, bonding it to create a 3D structure. SLS equipment typically can print multiple components simultaneously, making it a good choice for producing complex instruments when intermediate volumes are required, such as for orthopaedic trials.
Using specialty polymers, alone or with metal for these applications, allows manufacturers to reduce the overall weight of individual instruments as well as the total set weight of surgical trays. These materials also enable improved ergonomics to reduce surgeon fatigue and build in functionality through part consolidation for enhanced designs and faster production.
High-performance thermoplastics such as PolyEther Ether Ketone (PEEK) and PolyPhenylSUlfone (PPSU) deliver unique properties including high strength and stiffness, resistance to aggressive medical disinfectants and cleaning agents, and part stability under repeat steam autoclaving. Although these specialty polymers can be more expensive than some metals on a bulk basis, additive (vs. subtractive) manufacturing minimises material waste, often yielding cost reductions.
Printing orthopaedic implants
While metals such as titanium and cobalt chrome continue to be widely used in orthopaedic implants, specialty thermoplastics offer several advantages over metal, including radiolucency. PEEK is particularly suitable for load-bearing applications due to its outstanding fatigue or repeat loading performance. Unlike metal, PEEK is similar to cortical bone in terms of density, stiffness and weight.
PolyLactic Acid (PLA) and related chemistries, in combination with a ceramic, are being used to replace titanium screws in knee ligament surgery. The PLA compound is bioresorbable, avoiding the need to remove the metal screws in a second procedure.
Using additive manufacturing to create thermoplastic implants offers further benefits. Intricate new implant designs can be created to optimise osseointegration – permanent fixation of the implant via bone ongrowth and ingrowth without fibrous tissue interference at the implant/bone interface.
Advanced materials for additive manufacturing
To take full advantage of additive manufacturing methods, the healthcare industry requires specialised thermoplastics in the form of filaments and powders. Solvay’s high-performance medical-grade KetaSpire PEEK and Radel PPSU filaments are designed for printing limited-exposure applications (having less than 24 hours contact with bodily fluids and tissue) such as surgical instruments and devices, including cutting guides and personalised surgical instruments.
To support these products, Solvay offers comprehensive regulatory resources, including ISO 10993 limited contact testing with Master Access File (MAF) support. Global regulatory specialists can assist with medical device submissions and data requests.