Biomechanical evaluation of two plating configurations for fixation of a simple transverse caudal mandibular fracture model in cats

Use of a novel three-dimensional anatomical plating system for treatment of caudal mandibular fractures in cats: 13 cases (2019-2023)

CASE SERIES SUMMARY

A total of 13 cases of cats with a caudal mandibular fracture treated with a novel surgical technique using the Ramus Anatomical Plate system were reviewed. Preoperative, immediate postoperative and a minimum of 8 weeks postoperative CT images were required as inclusion criteria. The outcome and complications were determined from clinical data and radiographic follow-up examinations. All cases achieved adequate anatomical reduction, resulting in a functional and atraumatic occlusion postoperatively. No intraoperative complications were reported. Time to voluntary food intake was in the range of 1-25 days. No evidence of disruptions to the implants or screw loosening was observed in the 8-week postoperative CT imaging, with radiographic evidence of complete osseous union in all fractures. The most common postoperative complication was swelling at the surgical site. Two cats had postoperative exophthalmos due to retrobulbar haemorrhage, and one cat exhibited partial wound dehiscence 5 days postoperatively, which resolved with medical management. Longer-term complications included intraoral plate exposure in one cat, which required plate removal 10 months postoperatively.

RELEVANCE AND NOVEL INFORMATION

In this case series, rigid internal fixation of caudal mandibular fractures using the Ramus Anatomical Plate osteosynthesis system was associated with a minimal complication rate, and satisfactory radiographic and clinical outcomes. The reported outcomes of this novel technique are favourable when compared with previous techniques described for the management of these fracture types.

Mandibular fracture repair techniques in cats: a dentist's perspective

PRACTICAL RELEVANCE

Feline head trauma injuries are common in general practice, often resulting in mandibular fracture. An understanding of the recent advances in the field of mandibular fracture repair will facilitate evidence-based decision-making in clinical practice.

CLINICAL CHALLENGES

Feline maxillofacial and oral anatomy brings unique challenges in comparison with dogs. It has been commonplace to adapt techniques and equipment that are better suited to other body regions or are species-inappropriate for use in feline maxillofacial surgery, and this has traditionally resulted in high morbidity.

AIMS

This review presents an overview of the diagnosis of, and decison-making for, maxillofacial trauma in cats, specifically with reference to the feline mandible. The challenges associated with the management of these injuries are presented. Techniques for repair that can be employed in general practice, as well as more advanced surgical options, are discussed, as well as the indications for invasive vs non-invasive management. Underutilised methods involving composite dental materials and their versatility for the repair of mandibular fractures in cats, and miniplates for caudal mandibular fractures in cats, are specifically covered, as well as other recent advances in the field, including three-dimensional printing and custom-printed implants.

EVIDENCE BASE

Management of feline facial fractures is an often neglected topic, with very few published studies choosing to focus on head trauma outcomes in cats. Where available, however, this review draws on the published literature, as well as the authors' own clinical experience.

3D printed plates based on generative design biomechanically outperform manual digital fitting and conventional systems printed in photopolymers in bridging mandibular bone defects of critical size in dogs

Conventional plate osteosynthesis of critical-sized bone defects in canine mandibles can fail to restore former functionality and stability due to adaption limits. Three-dimensional (3D) printed patient-specific implants are becoming increasingly popular as these can be customized to avoid critical structures, achieve perfect alignment to individual bone contours, and may provide better stability. Using a 3D surface model for the mandible, four plate designs were created and evaluated for their properties to stabilize a defined 30 mm critical-size bone defect. Design-1 was manually designed, and further shape optimized using Autodesk ^® Fusion 360 (ADF360) and finite element analysis (FE) to generate Design-2. Design-4 was created with the generative design (GD) function from ADF360 using preplaced screw terminals and loading conditions as boundaries. A 12-hole reconstruction titanium locking plate (LP) (2.4/3.0 mm) was also tested, which was scanned, converted to a STL file and 3D printed (Design-3). Each design was 3D printed from a photopolymer resin (VPW) and a photopolymer resin in combination with a thermoplastic elastomer (VPWT) and loaded in cantilever bending using a customized servo-hydraulic mechanical testing system; n = 5 repetitions each. No material defects pre- or post-failure testing were found in the printed mandibles and screws. Plate fractures were most often observed in similar locations, depending on the design. Design-4 has 2.8-3.6 times ultimate strength compared to other plates, even though only 40% more volume was used. Maximum load capacities did not differ significantly from those of the other three designs. All plate types, except D3, were 35% stronger when made of VPW, compared to VPWT. VPWT D3 plates were only 6% stronger. Generative design is faster and easier to handle than optimizing manually designed plates using FE to create customized implants with maximum load-bearing capacity and minimum material requirements. Although guidelines for selecting appropriate outcomes and subsequent refinements to the optimized design are still needed, this may represent a straightforward approach to implementing additive manufacturing in individualized surgical care. The aim of this work is to analyze different design techniques, which can later be used for the development of implants made of biocompatible materials.

Patient Triage, First Aid Care, and Management of Oral and Maxillofacial Trauma

Maxillofacial trauma is a common presentation in veterinary medical practice. Accurate assessment, diagnostics, pain management, and finally repair are tenants to treatment. In addition to typical tenants for fracture repair, the restoration of occlusion and return to function (eating, drinking, grooming) are unique to trauma management in these patients. Options for repair include conservative management (tape muzzles), noninvasive repair techniques (interdental wiring and composite splinting), and invasive repair techniques (interfragmentary wiring and plate and screw fixation).

The Cat Mandible (II): Manipulation of the Jaw, with a New Prosthesis Proposal, to Avoid Iatrogenic Complications

Simple Summary

The small size of the feline mandible makes its manipulation difficult when fixing dislocations of the temporomandibular joint or mandibular fractures. In both cases, non-invasive techniques should be considered first. When not possible, fracture repair with internal fixation using bone plates would be the best option. Simple jaw fractures should be repaired first, and caudal to rostral. In addition, a ventral approach makes the bone fragments exposure and its manipulation easier. However, the cat mandible has little space to safely place the bone plate screws without damaging the tooth roots and/or the mandibular blood and nervous supply. As a consequence, we propose a conceptual model of a mandibular prosthesis that would provide biomechanical stabilization, avoiding any unintended (iatrogenic) damage to those structures. The improvement of imaging techniques and a patient-specific prosthesis made of full biocompatible material are part of the future trends to improve patients’ recovery.

Abstract

The cat mandible is relatively small, and its manipulation implies the use of fixing methods and different repair techniques according to its small size to keep its biomechanical functionality intact. Attempts to fix dislocations of the temporomandibular joint should be primarily performed by non-invasive techniques (repositioning the bones and immobilisation), although when this is not possible, a surgical method should be used. Regarding mandibular fractures, these are usually concurrent with other traumatic injuries that, if serious, should be treated first. A non-invasive approach should also first be considered to fix mandibular fractures. When this is impractical, internal rigid fixation methods, such as osteosynthesis plates, should be used. However, it should be taken into account that in the cat mandible, dental roots and the mandibular canal structures occupy most of the volume of the mandibular body, a fact that makes it challenging to apply a plate with fixed screw positions without invading dental roots or neurovascular structures. Therefore, we propose a new prosthesis design that will provide acceptable rigid biomechanical stabilisation, but avoid dental root and neurovascular damage, when fixing simple mandibular body fractures. Future trends will include the use of better diagnostic imaging techniques, a patient-specific prosthesis design and the use of more biocompatible materials to minimise the patient’s recovery period and suffering.

Biphasic Calcium Phosphate Microparticles Mixed With Autologous Blood: Application for the Reconstruction of a Large Mandibular Bone Defect in a Dog

Large mandibular bone defects can be difficult to treat in dogs, with a high risk of mal or nonunion due to instability and risk of infection. This case report describes the use of autologous clotted blood mixed with biphasic calcium phosphate microparticles to fill a defect in a nonunion fracture and promote bone regeneration in a dog using a 2-stage surgical approach. This new method was designed and tried in a dog with a chronic, unstable mandibular fracture associated with a large sequestrum. Initial treatment involved debridement of the lesion, then the oral wound and oral vestibule were reconstructed in 2 layers. Four weeks later a second stage surgery allowed placement of a pre-contoured maxillofacial plate to bridge the defect, which was filled with a blood/biphasic calcium phosphate compound implant. Cone-beam computed tomography was used prior to the initial surgery for preoperative planning and 3-D printing of a mandibular template for plate contouring. CT was subsequently used to document the healing process, using a bone density measurement tool to assess bone regeneration. Radiographic evidence suggestive of osseointegration was observed within 6 months with effective filling of the defect and restoration of alveolar ridge continuity. A return to normal and atraumatic occlusion was considered excellent. Cone-beam computed tomography was found useful to document radiographic evidence of osseointegration, bone regrowth and remodeling. This case report is to serve as a proof-of-concept study and should be followed by a prospective evaluation.

Biomechanical Testing of a Calcium Phosphate-Phosphoserine-Based Mineral-Organic Adhesive for Non-invasive Fracture Repair of Mandibular Fractures in Dogs

Mandibular fracture repair is complicated by limited availability of bone as well as the presence of the neurovascular bundle and an abundance of tooth roots. Fractures at the location of the mandibular first molar teeth are common and it can be particularly challenging to apply stable fixation. Non-invasive fracture repair techniques utilize intraoral placement of fixation devices typically involving polymerized composites and/or interdental wiring. A novel calcium phosphate-phosphoserine–based mineral–organic adhesive was tested ex vivo to determine its effects on augmenting strength of different non-invasive fracture fixation techniques. This study both tested the use of mineral–organic adhesive for the purpose of stabilizing currently used non-invasive fracture repair constructs (intraoral composite splinting ± interdental wiring) and evaluated adhesive alone or with subperiosteally placed plates on buccal cortical bone surface. Aside from controls, not receiving an osteotomy along the mesial root of the mandibular first molar tooth, six treatment groups were tested to evaluate ultimate strength, stiffness, angular displacement, bending moment, and application time. All forms of fixation were found to be significantly weaker than control (p < 0.001). Only the control (p < 0.001) and mineral–organic adhesive and composite (P = 0.002) groups were found to be significantly stronger than wire and composite. No difference was noted in stiffness between any groups with control or wire and composite. Application times varied from the mineral–organic adhesive group (mean = 206 s) to mineral–organic adhesive and composite (mean = 1,281 s). Twenty-three fixation devices exhibited adhesive failure, 20 demonstrated cohesive failure, and 5 failed by cohesive and adhesive failure. When evaluating the ultimate strength of the fixation device groups, mineral–organic adhesive, and composite was shown to be the strongest construct. The use of resorbable bone adhesive and composite may provide a stronger fixation construct over interdental wire and composite for mandibular fracture repair in dogs.