The Use of Three-dimensional (3D) Printing in Small Animal Surgery

Abstract

Three-dimensional (3D) printing is being used more and more in veterinary medicine. Currently, the most common veterinary applications are medical devices, lab equipment and tools, and teaching models. This chapter will be focusing on medical devices. These devices can be divided into three main categories. The first being metallic printed implants to address specific surgical pathologies in orthopedic and neurosurgery. The second is plastic and metallic guides to facilitate surgical procedures. And third, plastic-printed implants to simulate and plan surgical interventions.

1. Introduction

Three-dimensional (3D) printing is the creation of a 3D object in which a digital model of the object is transformed into a tangible model. The digital model can be created by using dedicated computer-aided design (CAD) software, by rendering a 3D scan of an object, or by using medical images. The medical images can be obtained from the scans of advanced imaging modalities such as computed tomography (CT) or magnetic resonance imaging (MRI). The term additive manufacturing describes the process through which these models are created: layers of material are superposed to create a final 3D model. The term subtractive manufacturing is the process through which material is removed from a raw substrate or block to create a 3D model. This process is also known as milling.

2. Three-dimensional printing: How does it work?

Several strategies can be used to create 3D models. Briefly, these are:

• Fused deposition modeling (FDM): this process uses a continuous filament of thermoplastic which is deposited in layers on top of each other. Figure 1a and b illustrate two types of FDM printers.

• Stereolithography (SLA): the principle behind this mode of 3D printing is photopolymerization of monomers into polymers using light of a definite wavelength. Polyjet printing is an optimization of this principle where multiple printing heads are combined into a larger one.

• Selective laser sintering (SLS): a laser fuses/melts a powder substrate that can be either plastic, metal, ceramic, or glass. Figure 2 illustrates an example of an SLS printer.

• Electron beam melting (EBM): this process is similar to SLS but with two differences. First, an electron beam is used instead of a laser. Second, the raw material does not need to be completely melted in order to be fused.

Figure 1.

Fused deposition modeling (FDM) printers. (a) Shows a low-cost in-house printer (Adventurer 4, Flashforge 3D printers, Zhejiang, China) and (b) shows a high-cost printer (Fortus 350mc, Stratasys, Eden Prairie Mn USA) that uses substrates that resist steam sterilization. (Figures provided by Dr. Dominique Gagnon (a) and Pr Bertrand Lussier (b).

Figure 2.

Illustrates a selective laser sintering (SLS) printer (EOSINT M 280, EOS Gmbh, Krailing, Germany). Figure provided by Pr Bertrand Lussier.

The methods mostly used in veterinary surgery are FDM, for printing plastic models and cutting guides, and SLS for printing metallic implants.

3. What are the applications of 3D printing in veterinary medicine?

Currently, 3D printing applications encompass three major domains in veterinary medicine. It is used in veterinary education, mostly in anatomy (general or surgical), and as aid in the development of surgical skills. Second, it is applied in research, either as specific tools or custom-made jigs. Third, it is also used for the development of surgical skills in animal models. Finally, it is used to create personalized medical devices to treat medical problems or as a tool to plan/simulate surgeries.

4. The use of 3D printing in small animal veterinary surgery

4.1 Introduction

3D printing is becoming increasingly popular in veterinary surgery, mainly in small animals, and is gradually evolving to become the state-of-the-art in patient care. Surgeons face the main challenge of preserving or improving the patient’s quality of life while also managing, meeting, and satisfying client expectations. Custom-designed, patient-specific, or personalized 3D-printed models are a valuable tool for preoperative surgical planning, student training, and client communication. 3D printing has been shown to improve the surgical approach, providing surgeons with a clearer understanding of the procedure, to increase self-confidence, and to reduce surgical and general anesthesia time. Surgeon fatigue is also a critical factor that should not be underestimated, especially during extended and complex surgical procedures. 3D-printed bone models, or biomodels, are used for surgical planning and rehearsal, assisting in surgical decision-making prior to definitive surgery and to improve intraoperative guidance. Figure 3 illustrates biomodels printed in triplicates for surgical planification and teaching. The accuracy of 3D printing in veterinary surgery has been confirmed by research on canine humeral models and pelvic replicas [1, 2]. To date, applications have mainly focused on limb-sparing surgeries [3, 4, 5, 6], correction of angular limb deformities [7, 8, 9, 10, 11], complex fracture management [12, 13, 14], and oral and maxillofacial surgeries in small animals [3, 15, 16, 17, 18, 19, 20]. Other reported indications for the use of this prototype technology are diverse in surgery and include correction of severe pectus excavatum in a 3-month-old kitten [21], exploration of a nasolacrimal duct obstruction in a dog [22], creation of personalized shelf implants for treating canine hip dysplasia [23], development of custom guides for bipolar coxofemoral osteochondral allografts in dogs [24], and assessment of custom cutting jigs and plates for canine cranial cruciate ligament rupture surgery [25, 26].

Figure 3.

Illustrates printed biomodels of a canine pelvis, antebrachium (radius/ulna), and tibia. They are printed in triplicates for planning and simulating corrective surgeries. These models have been printed the low-cost FDM printer outlined in Figure 1(a). Figure provided by Dr. Dominique Gagnon.

4.2 Limb-sparing surgery

Bone neoplasia in dogs, most commonly osteosarcoma, are treated with curative intent by stereotactic radiation therapy or surgical excision of the primary tumor, either by amputation or limb-sparing surgery. It is frequently combined with adjuvant chemotherapy. Distal radial limb-sparing surgery using a commercial 316 L stainless steel endoprosthesis has been reported in dogs [27, 28]. This approach has the advantage of relative simplicity compared with the use of a cortical allograft [27, 29], a vascularized [30, 31], or pasteurized tumoral autograft [32, 33], and other limb-sparing surgical techniques described in the literature. Commercially available endoprostheses are currently limited in geometry and size. This limited selection represents a challenge for veterinary surgeons who must adapt the implant to fit each patient’s unique and distinct bone geometry, osteotomy plane, and required plate length. The adaptability requirement can add complexity to the surgery, occasionally requiring multiple adjustments, such as implant contouring, to achieve an optimal fit and postoperative limb function. Moreover, this approach may be less adaptable to address diverse anatomical differences in some patients [6]. Utilization of 3D-printed implants permits the personalization of devices because they are highly versatile. 3D-printed implants account for the length of the ostectomy, and the normal anatomy of each dog (valgus, cranial curvature, and external rotation). Figure 4 illustrates the differences between the personalized 3D-printed and commercially available implants for limb sparing of the distal radius. The frequency of implant-related complications with commercial endoprostheses is high [27, 28]. Limb-sparing surgery using a custom-made, patient-specific 3D-printed endoprosthesis and cutting guide has been described and is gaining popularity in dogs because the rate of complications is reduced and patient outcomes are improved [3, 4, 5, 6]. A better-fitting implant may contribute to a more stable and functional limb post-surgery, potentially leading to a faster and smoother recovery for the patient. In a study by Timercan et al., the use of personalized endoprostheses resulted in a 25 to 50% reduction in surgery time compared to procedures involving commercial implants [6]. This decrease in surgery duration has the potential to reduce the risk of postoperative surgical site infection, a common occurrence in limb-sparing surgery. A pilot study reported patient-specific 3D-printed endoprosthesis surgery for the treatment of distal radial osteosarcoma in five dogs [5]. Although postoperative infection occurred in all patients, the surgery was successful and the alignment between the cutting guide and the endoprosthesis was rated as good to excellent for each treated bone. Figure 5 illustrates immediate postoperative radiographs of a clinical case of the left antebrachium following limb-sparing surgery for the correction of an osteosarcoma of the distal radius. The time interval between preoperative planning and surgery ranged from 14 to 70 days. As mentioned by these authors, a significant disadvantage of 3D printing in limb-sparing surgery is the time required to design and manufacture the custom implant before the procedure. Delaying surgery could lead to tumor progression and metastatic disease, making planned endoprosthesis an unsuitable option for some patients [5]. Bray et al. evaluated 12 dogs with tumors of the mandible, radius, and tibia and found that 25% of them had their tumor increase in size during the surgical planning period, necessitating a more extensive surgery than originally planned [3].

Figure 4.

Illustrates the differences between the personalized 3D-printed and the commercially available implants for limb-sparing surgery of the distal radius; (a) cranial and (b) lateral views of the 3D-printed implant (left) and the commercial implant (right). The personalized implant is slightly curvilinear and combines cranial bowing proximally and caudal bowing distally to match the patient’s anatomy. Its total length and the length of the spacer is perfectly adapted to the clinical presentation. The commercial plate and spacer are straight and the plate must be manually bended intraoperatively. Only 2 lengths of plates and spacers are available. Figures provided by Pr Bertrand Lussier.

Figure 5.

Illustrates immediate postoperative radiographs of a clinical case (a) cranio-caudal and (b) medio-lateral views of the left antebrachium following limb-sparing surgery for the correction of an osteosarcoma of the distal radius (courtesy Dr. Bernard Séguin).

4.3 Angular limb deformity correction

Medial patellar luxation is a common cause of pelvic limb lameness in small-breed dogs and is increasingly documented in larger breeds. Distal femoral osteotomy is a surgical treatment for management of femoral varus and torsion in dogs and can be performed as part of patellar luxation correction. The primary challenge in correcting angular limb deformity is accurately determining the nature and extent of the anatomical bone deformation. Careful and meticulous preoperative surgical planning is key to ensure the success of the surgery and an optimal outcome for the patient. Hall et al. compared femoral alignment before and after distal femoral osteotomy using a patient-specific 3D-printed osteotomy and reduction guide system both in vivo and ex vivo. Distal femoral osteotomy was performed in 10 client-owned dogs and their respective 3D-printed plastic bone models using a standard approach. CT imaging was done after surgery, and the femoral varus and femoral torsion angles were measured. In that study, the application of 3D printing increased the accuracy of correction of the femoral torsion angle in vivo, and both the femoral varus angle and femoral torsion angle ex vivo [10]. Information on duration of surgery, perioperative complications, and patient outcomes compared to conventional free-hand techniques was however limited in this study. DeTora and Boudrieau described a surgical technique for correction of complex distal femoral deformity from malunions in four dogs (five limbs) [9]. The procedure involved preoperative surgical planning using 3D-printed epoxy bone biomodels of the affected femurs and contralateral normal limbs in order to match the mirrored orientation. In the one dog with the condition bilaterally, femoral comparison was made from an anatomical specimen from a patient of similar size. Using a guide wire technique, a rehearsal procedure involving corrective femoral osteotomy with precontoured locking plate fixation was performed to ensure accuracy, gain efficiency, and optimize patient outcome. Surgery was guided by the rehearsal procedure for every dog and all precontoured implants were used with minimal modification intraoperatively. A good functional outcome was reported for each dog [9]. Similar results were reported after correction of angular limb deformity of the antebrachium in 11 dogs treated by corrective osteotomy with the assistance of a 3D printer [7, 8, 11].

4.4 Complex fracture management

3D printing has been shown to be useful for surgical planning and management of complex and challenging fractures in small animals [12, 13, 14]. In treating a traumatic comminuted mid-diaphyseal humeral fracture in a cat, Oxley used a patient-specific 3D-printed reduction guide system to facilitate minimally invasive plate osteosynthesis (MIPO) surgery [13]. In this context, the surgery was expected to be shorter than conventional MIPO, with a mean duration time of 50 minutes, as this approach eliminated the need for intraoperative imaging or the use of other temporary reduction devices during fracture fixation. One of the main technical challenges associated with conventional MIPO surgery for long bone fractures is to achieve the correct spatial orientation of the proximal and distal bone fragments and to maintain this alignment during plate fixation. The use of intraoperative imaging, such as fluoroscopy, is essential to avoid angular limb deformity postoperatively, increasing surgical time. Following the surgery, the cat in this study showed an early return to normal limb function, and advanced healing of the fracture was observed radiographically after 4 months. The author observed a 10% increase in the cost of surgery, attributed to the time invested in designing and producing the guide [13]. Similarly, in a different study, the cost of 3D prints ranged between 20 US$ and 35 US$ each [15]. Easter et al. reported custom-designed 3D-printed drill guides for the treatment of humeral intercondylar fissures in 11 dogs (16 elbows) with a mean body weight of 20.1 kg (range 14.2–25 kg). Postoperative CT data confirmed accurate and consistent placement of a 5-mm locking transcondylar screw, which represents a larger screw size than previously reported in this setting, within each assessed humeral condyle [12]. In a study by Scheuermann et al., the accuracy and efficiency of reduction provided by preoperative plate contouring to 3D-printed mid-diaphyseal femoral bone fracture models using a custom fracture reduction system or intramedullary pin to facilitate MIPO surgery in seven dogs were compared. In this study, femoral alignment was accurate, regardless of the reduction method, and the use of a custom surgical guide and precontoured implant decreased the need for intraoperative fluoroscopy [14]. Deveci et al. demonstrated that a 3D-printed drill guide facilitated precise fluoroscopic-assisted iliosacral Kirchner wire placement through a less invasive incision, when compared to free-hand drilling, in ten cadaveric dogs. This technique appears to be an effective and practical tool applicable to the clinical setting, assisting accurate fluoroscopic-guided iliosacral screw placement during surgical treatment of sacroiliac luxations in dogs [34]. Figure 6 illustrates a clinical case of a complex pelvic fracture (left sacroiliac fracture/luxation and an acetabular fracture) in a dog in which a 3D-printed biomodel was used to comprehend the fracture, plan the reduction by precontouring the implant and practice the surgery beforehand.

Figure 6.

Illustrates a clinical case of a complex pelvic fracture (left sacroiliac fracture/luxation and an acetabular fracture) in a dog in which a 3D-printed biomodel was used to comprehend the fracture, plan the reduction by precontouring the implant and practicing the surgery beforehand. (a) Ventrodorsal and (b) lateral radiographs of the hindquarter at presentation to the emergency service; (c) dorsal and (d) sagittal segmentations from the preoperative CT; (e) implant precontoured on the biomodel; (f) ventrodorsal and (g) lateral postoperative radiographs of the sacroiliac and acetabular fractures.

4.5 Oral and maxillofacial surgery

The application of 3D printing for preoperative planning in oral and maxillofacial surgery in dogs and cats has also been described [3, 15, 16, 17, 18, 19, 20]. Undertaking advanced oral and maxillofacial surgery presents several challenges for veterinary surgeons. This includes navigating the complex and delicate anatomy and geometry of the skull, anticipating potential significant complications such as acute bleeding, nerve damage, or impaired dental occlusion, and considering factors such as functional and esthetic outcomes, quality of life, and alignment with client expectations [16, 19]. Pet owners without medical training or experience, as well as veterinary students, interns and resident trainees, may find traditional 2D or advanced 3D computer-based imaging difficult to understand and interpret. The integration of 3D printing in oral and maxillofacial surgery may enhance veterinary trainee education and improve the client’s understanding of their pet’s medical condition, the recommended treatment plan, and expected outcome, especially when facial and bone structures are changed postoperatively [15, 16, 19, 35]. Preece et al. demonstrated that veterinary students using 3D-printed models performed better and had a more favorable, positive, and effective learning experience compared to those using textbooks or advanced computer-based imaging models [35]. Winer et al. described the application of 3D printing in complex oral and maxillofacial surgery, highlighting the benefits of this technology in surgical planning, student training, and client communication [19]. In this study, 3D printing was performed on 28 dogs and four cats for diverse applications. These included preoperative planning of mandibular reconstruction after mandibulectomy or defect non-union fracture, mapping the location of ostectomy for temporomandibular joint ankylosis/pseudoankylosis, evaluating palatal defects, better understanding of complex anatomy in cases of neoplasia located in challenging locations, and in the event of alteration of the anatomy secondary to trauma. Huang et al. reported similar advantages and indications of 3D-printed models in three dogs for resection of maxillary osteosarcoma, mandibular reconstruction after mandibulectomy, and defect arthroplasty for temporomandibular joint ankylosis [16]. These authors highlighted significant time savings due to the application of 3D printing, ranging from 15 minutes up to an hour of intraoperative time. Furthermore, a study in three dogs with orbital and peri-orbital masses using a preoperatively planned orbitectomy, showed that the procedure was invaluable in reducing morbidity in one case [15].

4.6 Neurosurgery

The use of 3D printing in neurosurgery mainly applies to surgeries involving the vertebral column and, at least up until now, to a lesser extent, the skull. However, as 3D printing is a rapidly growing research topic, other applications are likely to be developed in the near future.

If, currently, mainly CT imaging is used for designing 3D devices, the use of specific MRI sequences has been reported [36]. So far though, the quality of the models made with MRI images has not shown the same accuracy as with CT images [37] and combination of both techniques is sometimes necessary. The development of new MRI sequences with better bone signals might offer better results in the future.

As for any surgery, the main applications of 3D printing in neurosurgery are:

1. Preoperative planification and teaching,

2. Creation of patient-specific drill and implant guides,

3. Design of custom-made implants, and

4. Assistance in neurooncology.

4.6.1 Preoperative planification and teaching

Preoperative planning and teaching are a common and accessible use of 3D printing technology in veterinary neurosurgery. 3D-printed models allow for a more realistic representation of spinal anatomy compared to 2D images. Printed models of patient-specific spinal anatomy improve visualization of a malformation, anomaly, or fracture and enable the clinician to better prepare for the type of stabilization needed for a particular patient [36]. These models can be used to contour surgical plates preoperatively which helps to reduce the surgical time [36]. These models can also be used to teach anatomy (including vertebral column and skull). Another valuable application is to train residents or less experienced surgeons to drill in the different vertebral corridors. However, the lack of surrounding tissue as well as the polymer consistency, being different than that of normal bone, makes this use less accurate than practicing on cadavers [38].

The 3D-printed models can also be used for client education, to explain the surgical technique and the delicate nature of the procedure, for example in cases of atlantoaxial (AA) subluxation requiring surgical stabilization. Visualization of their animal’s anatomy in 3D may help owners better understand what surgery may entail and help them make a more informed decision for their pet.

4.6.2 Patient-specific drill and implant guides

Patient-specific drill and implant guides are printed, sterilized, and applied to the patient’s spine intraoperatively. For this application, the use of adapted substrates that are resistant to the autoclave and biocompatible is warranted. Fused deposition modeling but also stereolithography can be used for this purpose (Section 2).

In the author’s opinion, the use of patient-specific 3D-printed drills and implant guides is likely to become a “game-changer” for the practice of vertebral stabilization. A major benefit of 3D-printed patient-specific drill guides is their potential to improve the accuracy of implant placement which can be particularly helpful in narrow corridors with small margins of errors such as in AA stabilization in toy-breed dogs [39, 40]. Accurate screw placement, maximization of bone interface, and screw size can significantly increase the strength of the construct while minimizing intraoperative complications including damage to surrounding vulnerable structures such as major blood vessels or neural tissue [40, 41, 42]. For most of the patient-specific drills and implant guides described in the literature, the ideal screw trajectories, length, and optimal diameter can be planned on CT images using a CAD software. The contact surface of the drill guide is then constructed as an inverted representation of the vertebral surface such that the finished guide will fit snuggly onto the cortical bone [39, 43]. Drill tubes (using an inner cylinder shape subtracted from an outer cylinder) are created and oriented based on previously established ideal trajectories with the right angle. All these steps are done while ensuring that the drilling and implant placement will respect safe corridors for each vertebra [44]. Since drill guides are a combination of different guidance sleeves with the diameter respecting the required pilot hole, the drill bit used should fit nicely into it while respecting the selected angle [39, 43, 44].

The use of 3D-printed drill guides has been reported for AA stabilization [39, 45], thoracic vertebrae malformation correction [46], caudal cervical [47], and lumbosacral stabilizations [43]. The use of 3D-printed endoscopy ports for minimally invasive surgery for ventral slot, mini-hemilaminectomy, and corpectomy has also been reported [48, 49].

Zdichavsky classification is used in human neurosurgery and allows to score the accuracy of implant placements into vertebral corridors [50]. This classification has been used to evaluate the performance of patient-specific drill guides to assist surgeons in preventing vertebral corridor violation in both cadaver and in vivo studies [44, 46, 47, 51]. So far, though, it has yet to be validated for canine vertebral column stabilization.

4.6.2.1 Application for cervical vertebral column procedures

4.6.2.1.1 AA stabilization

AA stabilization is a challenging surgery given the risk of possible damage to important structures (major blood vessels, recurrent laryngeal nerve, and vagosympathetic trunk, thyroid gland) but also because of the very narrow corridors for screw placement in the atlas and axis because most affected dog breeds are toy dogs. In a cadaveric study, accurate screw placement in C1-C2 pedicles was achieved 92% of the time with 3D-printed guides compared to 56% without [51]. A case series with 12 dogs undergoing stabilization showed that adequate implant placement was achieved [39]. Using the Zdichavsky classification, the screws were contained within the pedicle 93% of the time and with minor penetration of the medial pedicle wall in the remaining 7%.

4.6.2.1.2 Pedicle screw placement for caudal cervical stabilization

A high pedicle screw placement accuracy (90% ideal placement) was reported with 3D patient-specific drill guides in a case series with three large breed dogs with little to no vertebral canal violation with this technique [47].

One major limitation of these studies is that there was no comparison with free-hand placing and surgeon experience might have influenced the high success rate. Therefore, the true benefits of the drill guides have not been objectively proven so far.

4.6.2.2 Application for thoracolumbar (TL) vertebral column procedures

For this type of surgery, safe implant placement can be challenging because of the small size of the vertebrae and the difficult surgical access (most anomalies affecting thoracic vertebrae which also implies a higher risk of pneumothorax associated with the approach). Abnormal anatomy makes proper corridor determination even more complex.

Comparison of two designs for TL placement (unilateral vs. bilateral) showed a low incidence of corridor violation (less than 4%) [44]. In this study, the authors found a difference only for exit point deviation between unilateral vs. bilateral drill guides with the first being more accurate. They provided the recommendation that safety margins of 1 mm at entry point, 2 mm at exit point and 4% angle deviation should be considered when designing drill guides for thoracolumbar implants.

Clinical application and successful use of similar guides were reported in six dogs with thoracic vertebral deformities associated with kyphosis and spinal cord compression [46]. In this study, the vast majority of implants placed were given a score of I in the Zdichavsky classification, which represents an optimal placement. The rest were given a score of IIa, corresponding to partial penetration of the medial pedicle wall [50]. The screws with the less optimal placement were placed in a dog with the most severe kyphosis and on the concave side of the curve, which is known to be more challenging [46]. In a more recent study from the same group, they looked at the post-surgical outcome in 22 dogs compiling 196 pedicle screw placement: 82% of screws had optimal placement and 55% of dogs had a stable neurological status while 33% improved post-surgery [52].

4.6.2.3 Application for lumbosacral vertebral column stabilization

The accuracy and repeatability of implant placement with 3D guides are likely influenced by the design of the guides and the influence of the surgeon’s experience. So far, their superiority due to free-hand placement is questionable [53]. In cadaveric studies, the accuracy of screw placement for LS stabilization using pedicle screws was shown to be similar when using 3D-printed drill guides compared to free-hand drilling [53, 54]. Furthermore, the variability of screw placements was higher when using 3D-printed guided compared to free-hand drilling for an expert surgeon but not for a novice surgeon in one of these studies. Conversely, in a retrospective study in five dogs, 3D-printed drill guides allowed ideal screw placement (i.e., fully contained inside the pedicle) in more than 90% of the cases, but no comparison was made between free-hand placement and the experience of the surgeon [43].

4.6.3 Patient-specific implants

The use of 3D-printed custom-made implants, although in its infancy in veterinary neurosurgery, will very likely gain in popularity in the next few years.

Currently, the main limitation is that it does require a more costly 3D printer using technologies such as SLS that can be used on different types of materials including stainless steel and titanium. The application of patient-specific implants has been reported for stabilization of AA luxation [45], skull defect and craniocervical malformation correction [55, 56], and even reconstruction after vertebrectomy for tumor removal [57]. Although only a few case reports have been published, it is possible that the application of patient-specific implants will eventually replace the use of polymethyl methacrylate which has a high risk of infection and of breakage and can be harder to remove if revision surgery is needed. Larger studies, ideally prospective and randomized, are needed to objectively evaluate the pros and cons of patient-specific implants and compare them to current methods.

4.6.4 Applications in neurooncology

The use of patient-specific 3D-printed devices has applications in neurooncology. For example, protocols to print brain tumors have been described using a combination of CT (for osseous structures) and MRI (for soft tissue and tumor details) images. This allows better evaluation of tumor size, anatomical location, and potentially plan surgery. This technique also allows preoperative delineation of the craniotomy landmarks and precontouring of surgical implants (titanium mesh, plates, or 3D-printed) to cover the bone defect at the end of the surgical procedure [36].

Furthermore, research is ongoing to develop 3D-printed stereotactic brain biopsy devices to improve accuracy and minimize complications associated with brain biopsies in small animals [58]. The use of 3D-printed drill guides has been reported to facilitate transsphenoidal hypophysectomy in dogs, which is a very challenging surgery relying upon precise knowledge and respect for anatomical landmarks [59]. Refinement of some of these techniques and development of new applications is likely to happen in the next few years.

4.6.5 Advantages and disadvantages of patient-specific 3D printed devices in veterinary neurosurgery

The perceived advantages of 3D printing models include decreased number of complications associated with poor implant placement, reduced surgical time, and improved patient outcome.

Some of the disadvantages of using patient-specific 3D-printed devices are: It requires some expertise to make the guides and additional time for preoperative surgical planning to design and print them.

Guide designing requires proper knowledge of the anatomy. To optimize the device, particularly for more complex procedures, a trial-and-error approach can be used with cadavers [44, 48, 49, 59].

During surgery, it is important to remove all the soft tissue to ensure perfect fitting of the guide on the bone otherwise inaccurate implant placement may ensue [39].

The cost of acquiring the equipment plays a role in deciding which type of printer is selected. In one study using SLA to print implant guides, the cost of the procedure was reported to increase by 10 to 15% when this technology was used [43]. In another study, there was an added cost of 10% for a transsphenoidal hypophysectomy which can probably be justified by greater precision and lower morbidity and mortality associated with the use of 3D-printed drill guides [59].

As for the timeline, one pilot study reported that the time to plan, create, process, ship, and sterilize patient-specific titanium implants for cranioplasty in dogs with a cranial tumor was approximately 2 weeks [55]. In this study, plate design and exportation for design took 15 minutes. The longer delay was for printing and post-processing which lasted 2 weeks. Another study reported a duration of 1 week to design and produce a guide after initial optimization on cadavers [59]. Designing drill guides for one vertebra was reported to take about 20 minutes in a third study [44]. Planning and designing implant guides or plates for more complex procedures, such as vertebral malformation and multiple sites, can take a lot of time. A learning curve for all new “creators” after each patient was observed. This additional time might be charged to the owner of the patient. Some companies have started to offer the service of designing and shipping patient-specific guides which might be an option for busy practitioners and might avoid the purchase of equipment that might not be used as often as necessary to justify its cost. Currently, any delay in designing and shipping might be problematic for rapidly growing tumors and spinal fracture repairs requiring timely intervention. As 3D printing becomes more widely available, it is very likely that the turnover time will be shortened. Some companies will probably even offer to remotely design a device that will be printed on a printer onsite potentially loaned by the company.

Currently, there has been no prospective and randomized study comparing neurosurgical procedures performed with and without 3D-printed devices to demonstrate the claimed benefits of 3D printing. These benefits could include a lower complication rate, decreased surgical and anesthesia time, and lower implant failure rate. Long-term follow-up of patients with 3D-printed implants is also needed to compare the rate of infection and the rate of implant failure in comparison with more conventional methods.

5. Conclusion

In summary, 3D printing in veterinary surgery has been shown to improve the diagnosis and treatment of complex pathologies. Their 3D visualization permits the clinician to proceed to more accurate and precise preoperative planning, providing valuable assistance to surgeons in decision-making. The creation of 3D-printed specific devices opens new avenues in veterinary surgery. However, further evaluation and exploration of many other applications of this technology in this specialty is warranted.