Mandibular Reconstruction of a Partial Hemimandibulectomy in a Dog with Severe Malocclusion

A Combined Ventral Extraoral and Intraoral Approach for Mandibulectomy in 9 Cats: A Case Series

This retrospective case series describes a combined ventral extraoral and intraoral approach for mandibulectomy in cats and highlights the importance of prompt management of the postoperative iatrogenic malocclusion through dental extraction, crown height reduction with vital pulp therapy or root canal therapy of the contralateral mandibular canine tooth. Nine cats were reviewed for signalment, history and physical examination, diagnostic workup, tumor type, mandibulectomy extension, lymph node removal as well as both intraoperative and postoperative complications. The performed surgical procedure was a combination of an extraoral approach ventrally to the mandible and an intraoral approach to remove the whole or a part of the mandible. Lymphadenectomy was achieved using the same surgical access. None of the cats had intraoperative complications. Postoperative complications were limited to regional swelling and drooling lasting a week. Seven cats were able to eat immediately after the surgery. Of the other 2 cats, 1 regained the ability to eat within a month and 1 only ate from the owner's hands. The surgical approach for mandibulectomy described allowed better access and visualization of the caudal part of the mandible and direct access to regional lymph nodes. Moreover, if the expected postoperative malocclusion is managed during the same surgical procedure, there is a higher rate of postoperative eating ability compared to what is reported in the literature.

Trends of regenerative tissue engineering for oral and maxillofacial reconstruction in veterinary medicine

Oral and maxillofacial (OMF) defects are not limited to humans and are often encountered in other species. Reconstructing significant tissue defects requires an excellent strategy for efficient and cost-effective treatment. In this regard, tissue engineering comprising stem cells, scaffolds, and signaling molecules is emerging as an innovative approach to treating OMF defects in veterinary patients. This review presents a comprehensive overview of OMF defects and tissue engineering principles to establish proper treatment and achieve both hard and soft tissue regeneration in veterinary practice. Moreover, bench-to-bedside future opportunities and challenges of tissue engineering usage are also addressed in this literature review.

Case report: Spontaneous mandibular body regeneration following unilateral subtotal mandibulectomy in a 3-month-old French bulldog

Objective

To document a case of spontaneous regeneration of the mandibular body following subtotal mandibulectomy in a juvenile dog.

Case summary

A 3-month-old male intact French bulldog was presented with papillary oral squamous cell carcinoma located at the dorsal aspect of the molar region of the left mandible. Initial biopsy of the mass was performed by the primary care veterinarian. Complete clinical staging revealed no signs of metastasis. Computed tomographic images of the head showed minimal contrast enhancement of the mass with no signs of periosteal or bone involvement. Subtotal mandibulectomy was performed. Histopathology indicated complete excision of the tumor. The patient returned 8-weeks later for follow up and cleft palate surgical repair, at which time bone was noted in the mandibulectomy area on palpation. Repeat computed tomography of the head revealed complete regeneration of the left mandibular body from the level of the ramus to the mandibular symphysis. No treatment for malocclusion was necessary due to the reformation of a functional mandible.

Clinical relevance

The present case demonstrates that spontaneous regeneration of the mandibular body is possible following subtotal mandibulectomy in immature dogs. Subtotal mandibulectomy is a radical procedure that can lead to long term complications including mandibular drift, malocclusion, and oral pain. This case report provides evidence that these sequelae may be mitigated or eliminated in young patients undergoing this procedure.

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.

Case report: Reconstruction of a complex maxillofacial gunshot defect using a titanium patient-specific implant in a dog

This report describes the surgical reconstruction of large maxillofacial defect caused by a short-range gunshot injury in a dog using titanium patient-specific implant (PSI). A 3-year-old male Wolf Shepherd was admitted for a large right facial defect with right nasal cavity exposure caused by a gunshot injury. Radiographic examination revealed severe loss of the right maxillary, nasal, and incisive bones, multiple fractures of both left and right palatine bones, and a comminuted fracture of the right mandible. Initial surgical procedure included computed tomography (CT) imaging for three-dimensional (3D) implant design. Open wound management was maintained for 18 days until the fresh granulation tissue fully covered the wound bed. The implant was designed in a “hand grasping shape” to cover the defect, align multiple fractured palatine bones, and make a snap fit function. Multiple holes, including cortical screw holes, were added to the final design. The implant was printed on a titanium alloy. Surgical application of titanium PSI was performed 19 days after the primary surgery. A free sublingual mucosal graft was used to reconstruct the mucosal layer of the right nasal cavity. The mucosa was then covered with collagen membrane to strengthen the structure of the nasal cavity. Blunt dissection of the hard palate mucoperiosteum above the palatine process and palatine bones, soft tissue above the maxilla was performed, and the 3D printed titanium implant was fastened in a preplanned position. The facial soft tissue defect was reconstructed, and the titanium PSI was covered using an angularis oris cutaneous flap. Partial flap necrosis occurred in the rostral aspect, and the wound was managed to heal by a second intension. Flap dehiscence at the junction of the flap and hard palate mucoperiosteum occurred with exposure of the implant 2 days postoperatively. Multiple attempts to close the defect failed, and the owner wanted to stop treatment. Healthy granulated tissue was observed proximal to the implant. The defect no longer increased in size and did not show any noticeable complications related to the defect at 60 days after titanium PSI application, and the dog was discharged. Six months post-operatively, the dog remained active with great appetite, gained weight, and showed acceptable facial symmetry without enlargement of the implant exposure or any implant-related problems.

A Retrospective Study on Mandibular Reconstruction Following Excision of Canine Acanthomatous Ameloblastoma

The successful excision of a locally invasive tumor such as canine acanthomatous ameloblastoma (CAA) typically results in a mandibular contour-derforming, critical-size defect that alters the jaw kinematics, and may affect the patient's quality of life. In this case series, we describe our experience using the regenerative approach of a titanium locking plate and compression resistant matrix infused with rhBMP-2 for the immediate or delayed reconstruction following mandibulectomy for the excision of mandibular CAA in 11 dogs. Surgical planning included computed tomography (CT), with and without contrast, in all cases, and 3D-printed models in four cases. Tumor-free surgical margins were achieved in all dogs. Clinical and diagnostic imaging follow-up (mean, 23.1 months) were performed in-person (11 cases) and with CT/cone-beam computed tomography in most cases, with standard radiography (3 cases) and telemedicine being utilized in 5 cases. At 2 weeks postoperatively, hard tissue was palpable at the defect. Follow-up imaging at 1 month postoperatively revealed evidence of bridging new bone with a heterogeneous appearance, that remodeled over 3–6 months to bone of a similar size, shape and trabecular pattern as native bone. Histological evaluation of regenerated bone was available in two cases, and was supportive of our clinical and imaging findings of normal remodeled bone. Clinically, all dogs returned to a normal lifestyle, rapidly resumed eating and drinking, and exhibited normal occlusion. Complications included wound dehiscence in one dog and self-limiting exuberant bone formation in two dogs. Tumor regrowth, failure of the implant or fracture of the regenerated bone were not observed. We conclude that the mandibular reconstruction using a regenerative approach is safe, feasible, and results in restoration of mandibular contour in dogs following segmental and bilateral rostral mandibulectomy for benign but invasive oral tumors such as CAA.

The oromaxillofacial region as a model for a one-health approach in regenerative medicine

The concept of a one-health approach in regenerative medicine has gained tremendous momentum in the scientific and public communities in recent years. Knowledge derived from this approach informs innovative biomedical research, clinical trials, and practice. The ultimate goal is to translate regenerative strategies for curing diseases and improving the quality of life in animals and people. Building and fostering strong and enthusiastic interdisciplinary and transdisciplinary collaboration between teams with a wide range of expertise and backgrounds is the cornerstone to the success of the one-health approach and translational sciences. The veterinarian's role in conducting clinical trials in client-owned animals with naturally occurring diseases is critical and unique as it may potentially inform human clinical trials. The veterinary regenerative medicine and surgery field is on a steep trajectory of discoveries and innovations. This manuscript focuses on oromaxillofacial-region regeneration to exemplify how the concept of interdisciplinary and transdisciplinary collaboration and the one-health approach influenced the authors' work experience at the University of California-Davis.

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).

Analysis of the Anatomic Relationship Between the Mandibular First Molar Roots and Mandibular Canal Using Cone-Beam Computed-Tomography in 101 Dogs

The mandibular first molar (M1) tooth of the dog is commonly involved in dental procedures. Tooth roots and the mandibular canal can vary in location, which has not been described on a large scale. The objective of this study was to describe the three-dimensional anatomic relationship of the mandibular M1 tooth roots and the mandibular canal in dogs. Cone-beam computed tomography (CBCT) was used to evaluate the anatomic relationship between the M1 tooth roots and the mandibular canal. CBCT images were collected from 101 canine cadaver heads from a variety of unknown breeds. All skulls used in this study were mesaticephalic, confirmed by facial index calculations. The position of the apex in relation to the mandibular canal and in relation to the buccal and lingual cortices was recorded and analyzed in relation to mandibular bone height: root length ratio. When evaluating the apex in a buccal-lingual relationship, the tooth roots were found to be located closer to the lingual cortex in 73.3% of M1 roots. Tooth root apical positions were found to be symmetric between the right and left side of the mouth in 93% of mesial roots and 95% of distal roots. Apical positions relative to the mandibular canal within the same tooth were found to be consistent in 52% of teeth. Teeth with roots dorsal to the mandibular canal were associated with the largest mandibular bone height: root length ratio. CBCT provides a more precise overview than dental radiographs of three-dimensional anatomy. The tooth root position can be estimated in a clinical setting based on the ratio of mandibular bone height to tooth root length obtained from intraoral radiographs. Understanding the relative location of important anatomic structures is key to avoiding complications associated with various dental procedures. This study has documented that assessing anatomic structures with 2D imaging alone is flawed, and the large majority of dogs have M1 roots closer to the lingual aspect than the buccal aspect of the mandible.

Kinematic analysis of mandibular motion before and after mandibulectomy and mandibular reconstruction in dogs

OBJECTIVE

To evaluate and quantify the kinematic behavior of canine mandibles before and after bilateral rostral or unilateral segmental mandibulectomy as well as after mandibular reconstruction with a locking reconstruction plate in ex vivo conditions.

SAMPLE

Head specimens from cadavers of 16 dogs (range in body weight, 30 to 35 kg).

PROCEDURE

Specimens were assigned to undergo unilateral segmental (n = 8) or bilateral rostral (8) mandibulectomy and then mandibular reconstruction by internal fixation with locking plates. Kinematic markers were attached to each specimen in a custom-built load frame. Markers were tracked in 3-D space during standardized loading conditions, and mandibular motions were quantified. Differences in mandibular range of motion among 3 experimental conditions (before mandibulectomy [ie, with mandibles intact], after mandibulectomy, and after reconstruction) were assessed by means of repeated-measures ANOVA.

RESULTS

Both unilateral segmental and bilateral rostral mandibulectomy resulted in significantly greater mandibular motion and instability, compared with results for intact mandibles. No significant differences in motion were detected between mandibles reconstructed after unilateral segmental mandibulectomy and intact mandibles. Similarly, the motion of mandibles reconstructed after rostral mandibulectomy was no different from that of intact mandibles, except in the lateral direction.

CONCLUSIONS AND CLINICAL RELEVANCE

Mandibular kinematics in head specimens from canine cadavers were significantly altered after unilateral segmental and bilateral rostral mandibulectomy. These alterations were corrected after mandibular reconstruction with locking reconstruction plates. Findings reinforced the clinical observations of the beneficial effect of reconstruction on mandibular function and the need for reconstructive surgery after mandibulectomy in dogs.

Successful Treatment of Mandibular Nonunion With Cortical Allograft, Cancellous Autograft, and Locking Titanium Miniplates in a Dog

Discontinuities of the mandible can occur for a variety of reasons including primary pathology of bone, pathologic fracture secondary to periodontal disease, and segmental resection for the treatment of neoplasia. Surgical intervention is necessary in many cases to establish normal occlusion and normal mandibular function. Rigid stabilization and treatment of these defects can be challenging due to the limited availability of bone for fixation as well as limited soft tissue coverage. This case report describes successful treatment of a nonunion fracture using cortical allograft and locking titanium miniplates. Complete osseointegration and bone healing were achieved, allowing for complete return to normal occlusion and function.

Mandibular Reconstruction by Using a Liquid Nitrogen-Treated Autograft in a Dog with an Oral Tumor

A 10 yr old intact female German shepherd dog presented with a large peripheral odontogenic fibroma and malignant melanoma on her lower jaw. The tumor was resected with a unilateral subtotal rostral hemimandibulectomy. After the mandible was removed, it was devitalized intraoperatively by freezing it in liquid nitrogen. It was subsequently reimplanted. New bone tissue formed in the gap between the frozen bone and the host bone. The regenerated bone contained osteocytes, osteoblasts, and blood vessels. The cosmetic appearance of the dog was preserved. The dog had normal mastication. The malignant melanoma recurred rostral of the left canine tooth at 159 days after the reconstruction surgery. A subtotal hemimandibulectomy was consequently performed. This is the first reported case of mandibular reconstruction using a liquid nitrogen-treated autograft in a dog with oral tumors.

Bridging Plate Development for Treatment of Segmental Bone Defects of the Canine Mandible: Mechanical Tests and Finite Element Method

With regard to the canine mandible, a mistaken concept of application is to assume that systemic plate-bone resistance is provided by the implant so that biomechanical position could be ignored. Because the alveolar border of the mandible is a tensile zone, the plate would ideally be positioned near this area while avoiding important structures. The aim of this study was to develop 2 bridging plates for the treatment of a segmental bone defect of the canine mandible using monocortical screws to avoid damage to the tooth roots and remaining neurovascular structures. Computed tomography images of the heads of 4 dogs (rottweiler, Doberman, boxer, and miniature poodle breeds) were used as models to develop the project. The images were reconstructed in 3-dimensional (3D) format. For each dog breed, 6 mandible prototypes were produced, each with a segmental bone defect in the right mandible. The mandibular reconstruction was performed with pure titanium bridging plate and locking screws. One plate model was developed for medium- and large-breed dogs and another for small-breed dogs. Mechanical testing showed the platemandible system resists the bite forces in all dog breeds. All safety factors were greater than I in the platemandible system for medium- and large-breed dogs and greater than 10 in the plate-mandible system for small-breed dogs. Thus, bridging plates designed with differentiated geometry and monocortical locking screws showed mechanical resistance to support simulated induced bone model defects and were able to support at least 5 times the value of bite force for each evaluated dog.

Regenerative Approach to Bilateral Rostral Mandibular Reconstruction in a Case Series of Dogs

Extensive rostral mandibulectomy in dogs typically results in instability of the mandibles that may lead to malocclusion, difficulty in prehension, mastication, and pain of the temporomandibular joint. Large rostral mandibular defects are challenging to reconstruct due to the complex geometry of this region. In order to restore mandibular continuity and stability following extensive rostral mandibulectomy, we developed a surgical technique using a combination of intraoral and extraoral approaches, a locking titanium plate, and a compression resistant matrix (CRM) infused with rhBMP-2. Furthermore, surgical planning that consisted of computed tomographic (CT) scanning and 3D model printing was utilized. We describe a regenerative surgical technique for immediate or delayed reconstruction of critical-size rostral mandibular defects in five dogs. Three dogs had healed with intact gingival covering over the mandibular defect and had immediate return to normal function and occlusion. Two dogs had the complication of focal plate exposure and dehiscence, which was corrected with mucosal flaps and suturing; these dogs have since healed with intact gingival covering over the mandibular defect. Mineralized tissue formation was palpated clinically within 2 weeks and solid bone formation within 3 months. CT findings at 6 months postoperatively demonstrated that the newly regenerated mandibular bone had increased in mineral volume with evidence of integration between the native bone, new bone, and CRM compared to the immediate postoperative CT. We conclude that rostral mandibular reconstruction using a regenerative approach provides an excellent solution for restoring mandibular continuity and preventing mandibular instability in dogs.

Initial Experience With rhBMP-2 Delivered in a Compressive Resistant Matrix for Mandibular Reconstruction in 5 Dogs

OBJECTIVE

To document cumulative initial experience and long-term follow-up of the use of rhBMP-2/CRM for reconstruction of large mandibular defects (≥5 cm) in dogs.

STUDY DESIGN

Retrospective case series.

ANIMALS

Dogs (n = 5).

METHODS

Medical records (October 1999-April 2011) of dogs that had mandibular reconstruction for defects/resections of ≥5 cm using rhBMP-2/CRM were reviewed. Signalment, preoperative assessment/rationale for mandibular reconstruction, surgical methods, postoperative assessment of the reconstruction (evaluation of occlusion), and complications were recorded. A definitive histologic diagnosis was obtained in dogs that had mandibular resection for mass removal. Long-term complications were determined. A minimum time frame of 2-year in-hospital follow-up was required for case inclusion.

RESULTS

Mandibular reconstruction was successfully performed in all dogs' defects where gaps of 5-9 cm were bridged. Surgical reconstruction rapidly restored cosmetic appearance and function. All dogs healed with new bone formation across the gap. New bone formation was present within the defects as early as 2 weeks after surgery based on palpation, and new bone formation bridging the gap was documented radiographically by 16 weeks. Minor complications occurred in all dogs in the early postoperative period, and included early firm swelling and gingival dehiscence in 1 dog; late plate exposure in 3 dogs; and exuberant/cystic bone formation in 2 dogs (related to concentration/formulation of rhBMP-2/CRM). Two dogs had minor long-term complications of late plate exposure and a non-vital canine tooth; the plates and the affected canine tooth were removed. Long-term in-hospital follow-up was 5.3 years (range, 2-12.5 years); further long-term telephone follow-up was 6.3 years (range, 2-12.5 years). All owners were pleased with the outcome and would repeat the surgery again under similar circumstances.

CONCLUSION

The efficacy and success of this mandibular reconstruction technique, using rhBMP-2/CRM with plate fixation, was demonstrated with bridging of large mandibular defects regardless of the underlying cause, and with excellent cosmetic and functional results. Complications were common, but considered minor and easily treated. The complications encountered revealed the importance of tailoring the use of BMPs and fixation methods to this specific anatomic location and indication.

Regenerating Mandibular Bone Using rhBMP-2: Part 1-Immediate Reconstruction of Segmental Mandibulectomies

OBJECTIVE

To describe a surgical technique using a regenerative approach and internal fixation for immediate reconstruction of critical size bone defects after segmental mandibulectomy in dogs.

STUDY DESIGN

Prospective case series.

ANIMALS

Dogs (n = 4) that had reconstruction after segmental mandibulectomy for treatment of malignant or benign tumors.

METHODS

Using a combination of extraoral and intraoral approaches, a locking titanium plate was contoured to match the native mandible. After segmental mandibulectomy, the plate was secured and a compression resistant matrix (CRM) infused with rhBMP-2, implanted in the defect. The implant was then covered with a soft tissue envelope followed by intraoral and extraoral closure.

RESULTS

All dogs that had mandibular reconstruction healed with intact gingival covering over the mandibular defect and had immediate return to normal function and occlusion. Mineralized tissue formation was observed clinically within 2 weeks and solid cortical bone formation within 3 months. CT findings at 3 months showed that the newly regenerated mandibular bone had ∼50% of the bone density and porosity compared to the contralateral side. No significant complications occurred.

CONCLUSION

Mandibular reconstruction using internal fixation and CRM infused with rhBMP-2 is an excellent solution for immediate reconstruction of segmental mandibulectomy defects in dogs.

Regenerating Mandibular Bone Using rhBMP--2: Part 2-Treatment of Chronic, Defect Non-Union Fractures

OBJECTIVE

To describe a surgical technique using a regenerative approach and internal fixation for reconstruction of critical size bone defect non-union mandibular fractures.

STUDY DESIGN

Case series.

ANIMALS

Dogs (n = 6) that had internal fixation of defect non-union mandibular fracture.

METHODS

In 5 dogs, the repair was staged and extraction of teeth performed during the initial procedure. After 21-98 days (mean, 27 days) pharyngotomy intubation and temporary maxillomandibular fixation were performed. Using an extraoral approach, a locking titanium miniplate was contoured and secured to the mandible. A compression resistant matrix (CRM) infused with rhBMP-2 was implanted in the defect. The implant was then covered with a soft tissue envelope followed by surgical wound closure.

RESULTS

All dogs healed with intact gingival covering over the mandibular fracture site defect and had immediate return to normal function and correct occlusion. Hard-tissue formation was observed clinically within 2 weeks and solid cortical bone formation within 3 months. CT findings in 1 dog at 3 months postoperatively demonstrated that the newly regenerated mandibular bone had 92% of the bone density and porosity compared to the contralateral side. Long-term follow-up revealed excellent outcome.

CONCLUSION

Mandibular reconstruction using internal fixation and CRM infused with rhBMP-2 is an excellent solution for the treatment of critical size defect non-union fractures in dogs.

Effect of Escherichia coli-produced recombinant human bone morphogenetic protein 2 on the regeneration of canine segmental ulnar defects

Because bone morphogenetic protein 2 gene transfected Escherichia coli (E-BMP-2) produce recombinant human BMP-2 (rhBMP-2) more efficiently than mammalian cells (Chinese hamster ovary [CHO]-BMP-2), they may be a more cost-effective source of rhBMP-2 for clinical use. However, use of E-BMP-2 for regenerating long bones in large animals has not been reported. In the current study, we evaluated the healing efficacy of E-BMP-2 in a canine model. We created 2.5-cm critical-size segmental ulnar defects in test animals, then implanted E-BMP-2 and 700 mg of artificial bone (beta-tricalcium phosphate; β-TCP) into the wounds. We examined the differential effects of 5 E-BMP-2 treatments (0, 35, 140, 560, and 2240 μg) across 5 experimental groups (control, BMP35, BMP140, BMP560, and BMP2240). Radiography and computed tomography were used to observe the regeneration process. The groups in which higher doses of E-BMP-2 were administered (BMP560 and BMP2240) displayed more pronounced bone regeneration; the regenerated tissues connected to the host bone, and the cross-sectional areas of the regenerated bone were larger than those of the originals. The groups in which lower doses of E-BMP-2 were administered (BMP35 and BMP140) experienced relatively less bone regeneration; furthermore, the regenerated tissues failed to connect to the host bone. In these groups, the cross-sectional areas of the regenerated bone were equal to or smaller than those of the originals. No regeneration was observed in the control group. These findings suggest that, like CHO-BMP-2, E-BMP-2 can be used for the regeneration of large defects in long bones and that its clinical use might decrease the cost of bone regeneration treatments.

Treatment of a nonunion, secondary to gunshot fracture, of the distal radius with circular external fixation and rhBMP-2 in a cat

OBJECTIVE

To report the successful use of recombinant human bone morphogenetic protein-2 (rhBMP-2) in the treatment of an antebrachial non-union, secondary to gunshot fracture, stabilized with circular external fixation in a cat.

PROCEDURE

Following a diagnosis of a highly comminuted gunshot fracture of the distal right radius and ulna, the fracture was stabilized with a circular external fixation. A two-ring frame was placed in closed fashion.

RESULTS

The skin wound healed uneventfully by second intention in 21 days. Twenty-eight weeks after external fixation, bone healing was absent. 0.8mL of 0.2mg/mL of rhBMP-2 in two collagen sponges was placed in the bone defect. Eight weeks after rhBMP-2 implantation, an early bone healing response was noted on radiographic evaluation. Sixteen weeks after rhBMP-2 implantation, fracture union was achieved.

DISCUSSION

To the authors' knowledge, 160 μg is the lowest reported dose of rhBMP-2 that leads to bony union in a cat. However as an individual case study, this report can not be used as evidence that rhBMP-2 at this lower dose is appropriate for use in all cats. Further studies are needed to establish the minimum efficient dose of rhBMP-2 in cats.

Elastic training for the prevention of mandibular drift following mandibulectomy in dogs: 18 cases (2005-2008)

OBJECTIVE

To describe a noninvasive method for preventing mandibular drift (MD) after mandibulectomy in dogs.

STUDY DESIGN

Technique description and case series.

ANIMALS

Dogs (n=18) that had mandibulectomy involving resection of a portion of the mandible caudal to the 2nd mandibular premolar tooth.

METHODS

One orthodontic button was attached to the lingual aspect of the canine tooth of the intact mandible and 1 to the buccal aspect of the ipsilateral maxillary 4th premolar tooth. An orthodontic elastic rubber chain was attached to the buttons creating tension sufficient for maintaining normal occlusion. The rubber chain was replaced weekly by the clients. Follow-up appointments were scheduled 2, 6, 10 weeks postoperatively and monthly thereafter if indicated. The appliance was removed when dogs had resumed normal occlusion of the canine teeth.

RESULTS

All dogs maintained normal occlusion, normal jaw function, had no apparent disfigurement, and resumed preoperative activity levels while wearing the appliance. Eight dogs achieved temporomandibular joint stability and normal occlusion 4.5-6 months postoperatively and 8 did not, resulting in MD. One dog was lost for follow-up and 1 was euthanatized.

CONCLUSION

Elastic training using orthodontic buttons and power chain is a viable option for prevention of MD but requires good client compliance. More data and longer follow-up are required to determine the long-term mandibular stabilizing potential of this technique.

CLINICAL RELEVANCE

Elastic training is a quick, simple, cost-effective and noninvasive technique, preserving normal occlusion and function in many dogs after mandibulectomy.

Use of bone morphogenetic proteins for augmentation of bone regeneration

A large body of preclinical and clinical data now documents that recombinant BMPs can be used for skeletal regeneration in humans and animals. Recombinant human BMP-2 and BMP-7 have been approved for use in human patients with long-bone fractures and nonunions and in patients undergoing lumbar fusion or various maxillofacial and dental regenerative procedures. These products have also been made available for veterinary use.

Assessment of distraction regenerate using quantitative bone scintigraphy

In this study, we examined whether quantitative bone scintigraphy can be used to assess new bone formation following distraction osteogenesis (DO). A vertical osteotomy was performed on the right hemimandible of male Sprague-Dawley rats, and a custom-made distraction device was applied. Following the gradual distraction, rats were divided into 2 subgroups, the second and fourth week. Cephalograms were taken and scintigraphic and histomorphometric analysis was performed at the second and fourth week. Scintigraphic findings showed good correlation with histomorphometric results. Results were compared with sham-operated (skin and muscle incision and placement of pin but no osteotomy) and acute distraction (5-mm acute distraction) groups. Scintigraphic mean uptake ratios were significantly higher in the gradual distraction group compared with the sham-operated and acute distraction groups. Quantitative bone scintigraphy is a promising method for the assessment of DO and consolidation. It could offer objective qualitative and quantitative data for the noninvasive evaluation of bony regenerate.

Clinical application of recombinant human bone morphogenetic protein-2 in 4 dogs

OBJECTIVE

To describe outcome in dogs with insufficient bone healing treated with recombinant human bone morphogenetic protein-2 (rhBMP-2).

STUDY DESIGN

Retrospective study.

ANIMALS

Four dogs clinically affected with delayed union or nonunion bone healing.

METHODS

Medical records were reviewed for signalment, clinical problem, treatment, and outcome.

RESULTS

Four dogs that had delayed- or nonunion of bone fracture, osteotomy, or arthrodesis were treated with either minimally invasive, fluoroscopically guided, percutaneous administration or direct surgical application of rhBMP-2. Doses used ranged from 0.2 to 1.6 mg of rhBMP-2. In 3 dogs, a calcium phosphate matrix (CPM) carrier was used whereas in 1 dog commercially prepared rhBMP-2 impregnated in an absorbable collagen sponge (INFUSE Bone Graft) was used. This latter dog had osteomyelitis associated with implant infection before rhBMP-2 administration. Rapid radiographic union was noted in all dogs with excellent long-term outcome. Adverse effects were minimal and included transient worsening of lameness after percutaneous administration of rhBMP-2 in 2 dogs.

CONCLUSIONS

rhBMP-2 stimulated rapid bone formation at delayed- or nonunion sites resulting in radiographic bone union with minimal adverse effects and excellent long-term outcome in 4 dogs.

CLINICAL RELEVANCE

Direct intraoperative administration or fluoroscopically guided, minimally invasive delivery of rhBMP-2 may be an effective treatment modality for bone delayed- or nonunions and could potentially be used to stimulate new bone production in a variety of orthopedic surgical conditions in dogs.

Mandibulectomy and Maxillectomy

In an animal presented for evaluation of an oral tumor, the extent of the disease is based on the systematic evaluation of the tumor, including diagnostic imaging, and the assessment of regional lymph node involvement and distant metastases. The nature of the disease is determined by an incisional biopsy and histopathologic examination. The choice of treatment and expected outcome are based on the stage and expected biologic behavior, which is well known for many oral tumor types. The various mandibulectomy and maxillectomy techniques have been shown to give good functional and cosmetic results.