3D-printing: A new frontier in veterinary orthopaedics

The basic principle of 3D-printing is these days familiar to most; very thin layers of material are sequentially printed, building up a potentially complex 3D object. An astonishing range of materials can be 3D-printed including most surgically implanted metals (for example stainless steel, titanium, titanium alloys and cobalt-chrome), many plastics (including biocompatible and autoclavable forms), and biological materials (such as cells and scaffolds including hydrogels hydroxyapatite). In veterinary orthopaedics 3D-printing is currently used predominantly for the creation of printed bone models and surgical guides, and in the manufacture of patient-specific or complex implants. There is immense potential for tissue engineering applications, although in veterinary orthopaedics these techniques are not widely clinical available at present

3D-printed bone models and surgical guides

The most basic application of 3D-printing in veterinary orthopaedics is the creation of printed bone models. The ability to directly visualise for example a bone deformity can facilitate surgical planning, as well as permitting surgical rehearsal. CT data is the starting point for model creation. The 3D data describing the bone itself is extracted from the complete data set, some CAD processing performed, with the 3D virtual bone model then exported to the 3D printer. Since the thickness of the 3D-printed layers is much less than that of a CT scanner (25-100µm vs. >600µm) the accuracy of the model is determined by the CT data rather than the printer, although this remains very high.

The ability to manipulate 3D virtual bone models in CAD software allows planning of surgical interventions including deformity corrections, vertebral stabilisations and complex fracture alignments. Patient-specific surgical guides can then be created which permit translation of the surgical plan to the patient in theatre. These guides typically incorporate a bone contact surface that accurately reflects the contours of the cortex beneath; the guide therefore fits onto the bone in a unique location, allowing accurate localisation of osteotomy guide planes and drill hole trajectories. Guides are typically printed in biocompatible, autoclavable plastic. Clinical benefits include consistent, accurate surgical outcomes, reduced surgical time, and the ability to place implants into narrow safe corridors.

3D-printed implants

3D-printing in metal remains a specialist process, requiring a significant investment in hardware as well as engineering skills and facilities. Patient-specific metal implants can be printed which fit uniquely into position in much as the same way as plastic surgical guides. Such implants are rarely necessary for routine interventions such as deformity corrections, but have significant potential advantages in more complex applications such as limb-sparing surgery and reconstruction of other large bone deficits. 3D-printed patient-specific joint replacement prostheses are used in human orthopaedics and have been applied in specific veterinary applications.

The second key use of 3D metal printing in veterinary orthopaedics is in the production of generic, but complex, implants. The key advantage over traditional manufacturing techniques is the ability to easily create complicated 3D shapes, and to incorporate specialised surfaces (e.g. for bone ingrowth) without the need for multiple engineering processes.

The future

What is the future of 3D-printing in veterinary medicine? As with all new technologies costs will come down, and accessibility to non-specialist users improve. Already dentists can use cloud-based software to create their own patient-specific drill guides which are printed and arrive a few days later; maybe before long vets will be doing the same. And the list of applications continues to grow, both in other surgical fields (e.g. 3D-printing of portosystemic shunts and tumours) and in non-surgical areas (e.g. customisable 3D-printed drugs). Will 3D printing alter the face of veterinary medicine? Not in the foreseeable future, especially in the context of high-tech applications such as tissue engineering. However, especially in specific areas such as orthopaedics many existing applications are already resulting in improved patient care at accessible cost, a trend that will certainly continue.

Bill graduated in 1997, and after a period in general practice undertook an orthopaedic Residency at Willows Referral Service between 2009 and 2011. Bill gained his RCVS Diploma in Orthopaedics in 2013, and RCVS Specialist status the following year. Bill founded Vet3D in 2015 to provide access for orthopaedic surgeons to CAD based surgical planning and patient-specific orthopaedic and neurosurgical guide systems.

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