Evaluation of a free vascularized medial tibial bone graft in dogs

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.

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.

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.

Vascular perfusion of the dorsal and palmar condyles of the equine third metacarpal bone

REASONS FOR PERFORMING STUDY

Palmar osteochondral disease (POD) is an overload arthrosis that commonly affects fetlock joints of racing Thoroughbreds (TB) but the aetiopathogenesis of the disease has not been well defined.

OBJECTIVES

The aim of this study was to compare India ink perfusion in the dorsal and palmar condyles of the third metacarpal bone (McIII) in both passively flexed and maximally extended fetlock joints from paired equine cadaver limbs.

STUDY DESIGN

Descriptive cadaver study comparing perfusion of condyles of McIII in paired cadaver limbs in flexion (control group) and maximal extension (intervention group).

METHODS

Pairs of forelimbs were acquired from 5 TB horses subjected to euthanasia for reasons unrelated to lameness. Limb pairs were perfused intra-arterially with India ink and then randomly assigned to passive flexion or maximal extension of the fetlock joint. Limbs were sectioned sagittally in 3 mm sections through the fetlock and 12 sections per limb processed using a modified tissue-clearing technique. Sections were subsequently digitally imaged and bone perfusion evaluated with image analysis software.

RESULTS

Greater perfusion of the dorsal condyle than of palmar condyle was observed in 78% of sections from limbs in passive flexion and 92% of maximally extended sections. Perfusion to the palmar aspect of the condyle was significantly decreased (P < 0.0001) when the limbs were placed in maximal extension compared to passive flexion.

CONCLUSIONS

The palmar condyle of McIII had less perfusion than the dorsal condyle when the fetlock joint was in passive flexion and this difference was exacerbated by maximal extension. Based on the anatomical location of POD lesions, perfusion differences between the dorsal and palmar condyles of McIII may be associated with development of these lesions.

Vascularized Ulnar Bone Grafts for Limb-Sparing Surgery for the Treatment of Distal Radial OsteosarcomaS

The objective of this retrospective study was to compare vascularized free or roll-in ulnar bone grafts for limb-sparing surgery in dogs with radial osteosarcoma with the cortical allograft, metal endoprosthesis, or distraction osteogenesis techniques. Overall, the ulnar graft techniques used in this study demonstrated excellent healing properties. Complications included recurrence of the tumor in 25% (2/8) of the dogs, metastasis in 50% (4/8) of the dogs, implant loosening in 37.5% (3/8) of the dogs, implant failure in 12.5% (1/8) of the dogs, and infection in 62.5% (5/8) of the dogs. Mean survival time was 29.3 mo (range, 9 to 61 mo). The mean metastasis-free interval was 33.67 mo (range, 8 to 54 mo). Tumors recurred locally in two dogs at 10 mo and 20 mo postoperatively. This study yielded similar long-term complications as other limb-sparing options (such as cortical allografts and metal endoprostheses) and allowed dogs to bear weight on the operated limb with acceptable limb function. More research is needed regarding specific healing times for ulnar vascularized grafts, time until implant removal, and the extent of radial bone that could ultimately be replaced by the ulna.

Distal limb and paw injuries

Distal limb reconstruction is complicated by the paucity of local tissues and the frequent association of orthopedic injury with cutaneous loss. Second-intention healing or skin stretching techniques are used for wounds involving less than a 30% circumference of the limb. Skin grafts are recommended for reconstruction of larger superficial wounds after establishing a bed of granulation tissue or for immediate reconstruction of clean wounds overlying healthy muscle. Wounds complicated by orthopedic injury benefit from early reconstruction using vascularized tis-sue. Weight-bearing surface reconstruction and management of partial amputation injuries are functionally difficult because of the environmental stress placed on the paw pads. Paw pad grafts, paw pad transposition techniques, centralization of digits, and microvascular free tissue trans-fer of paw pads can be considered for weight-bearing surface reconstruction. Definitive guidelines describing when each of these techniques should be used have not been established.

Surgical Approaches to Recipient Vessels of the Fore- and HindLimbs for Microvascular Free Tissue Transfer in Dogs

OBJECTIVE

To develop and evaluate surgical approaches to the arteries and veins of the fore- and hindlimbs for use as potential recipient vessels for free tissue transfer.

STUDY DESIGN

Experimental anatomic study.

SAMPLE POPULATION

Canine cadavers (11): 2 preserved and 9 fresh cadavers.

METHODS

Fore- and hindlimbs from 1 preserved cadaver injected with a pigmented silicone/barium mixture, through the common carotid artery and external jugular vein, were cut in 1 cm cross-sections. Tissue sections were used to identify the location of vessels >1 mm that could be used as recipient vessels for free tissue transfer. The other preserved cadaver was used to develop surgical approaches to these vessels. Three surgeons evaluated the written descriptions and illustrations for these approaches using fresh cadavers. Modifications to the surgical approaches were made based on recommendations from these surgeons.

RESULTS

Six approaches were developed to isolate forelimb recipient vessels: palmar access, distal medial antebrachial, mid-antebrachial, proximal antebrachial, distal humeral, and mid-humeral vascular access. Twelve approaches were developed to isolate recipient vessels of the hindlimb: plantar access, dorsal tarsal, cranial distal tibial, craniomedial distal tibial, lateral distal tibial, medial distal tibial, medial femorotibial, lateral distal femoral, medial femoral, proximal medial femoral, groin, and proximal lateral femoral vascular access.

CONCLUSIONS

Six forelimb and 12 hindlimb sites were identified for surgical access to recipient vessels (>1 mm diameter) suitable for use in free tissue transfer for wound reconstruction.

CLINICAL RELEVANCE

For reconstruction of complex wounds of the extremities of dogs, surgeons should consider use of readily accessible recipient vessels that would allow for free tissue transfer to the fore- and hindlimbs.

Modification of the Superficial Cervical Axial Pattern Skin Flap for Oral Reconstruction

OBJECTIVE

To describe an extended pedicle flap based on the superficial cervical artery (SCA) for closure of oral defects in dogs.

STUDY DESIGN

Anatomic study; in vivo experimental study.

ANIMALS

Canine cadavers (13) and 3 dogs.

METHODS

The prescapular branch of the SCA was cannulated and perfused with a lead oxide gelatin mixture. The area perfused by 1 SCA was examined as was the rostral extent of the flap. Staged implantation was performed to evaluate flap performance in vivo. In stage 1, the flap was prepared for implantation into the oral cavity. In stage 2, the flap was fully developed to include the 1 degrees, 2 degrees, and partial 3 degrees angiosome of 1 SCA pedicle. The flap was transposed by a bridging incision and a parapharyngeal tunnel into the oral cavity. The flap was used to reconstruct a partial-thickness defect created in the palate.

RESULTS

The territory of the contralateral SCA was captured in all cadavers. The full flap reached the level of the canine teeth in all cadavers. In live dogs, necrosis was not observed after implantation into partial-thickness defects and dehiscence was minimal. Loss of pliability secondary to de-epithelialization and staging resulted in a limitation of rostral reach of the flap.

CONCLUSIONS

Whereas the flaps did not reach as far rostrally as anticipated, they survived well in the harsh oral environment. The flap may be modified to reconstruct full-thickness palatal defects.

CLINICAL RELEVANCE

The extended SCA pattern flap may be adapted for closure of oral defects.

Evaluation of primary critical ischemia time for the deep circumflex iliac cutaneous flap in cats

OBJECTIVE

To evaluate the primary critical ischemia time for the deep circumflex iliac (DCI) cutaneous flap in cats.

STUDY DESIGN

In vivo model.

ANIMALS

Thirteen young adult female cats.

METHODS

An island skin flap was created on the right side of each cat based on the angiosome of the ventral branches of the DCI vessels. The cats were randomly assigned to a flap ischemia time ranging from 1 to 3 hours in 10-minute intervals. Microvascular clamps were used to occlude the artery and vein for the designated time. Flaps were sutured into position after the ischemic period. On day 3, fluorescein dye was administered and the flaps were evaluated under ultraviolet light to assess percent area of perfusion. On days 7 and 14, the percent area of survival was determined for each flap based on cutaneous morphometry.

RESULTS

All flaps had 100 percent area of survival throughout the study. On day 3, all flaps fluoresced uniformly compared with the surrounding skin. On days 7 and 14, all flaps were uniformly viable as confirmed by skin color, consistency, bleeding, and hair re-growth.

CONCLUSION

The DCI cutaneous flap in cats can withstand up to 3 hours of ischemia with predictable survival.

CLINICAL RELEVANCE

In a clinical setting, high success rates can be expected with microvascular transfer of the DCI cutaneous flap in cats when the ischemia time is <3 hours and precise surgical technique is used.

Surgical approaches to recipient vessels of the head and neck for microvascular free tissue transfer in dogs

OBJECTIVE

To develop and evaluate surgical approaches to the arteries and veins of the head and neck for use as potential recipient vessels for free tissue transfer.

STUDY DESIGN

Experimental anatomic study.

SAMPLE POPULATION

Eleven canine cadavers; 2 preserved cadavers and 9 fresh cadavers.

METHODS

The head and neck of one preserved cadaver injected with pigmented silicone/barium, through the common carotid artery and external jugular vein, was cut in 1 cm sagittal sections and cross-sections. These tissue sections were used to identify the location of recipient vessels >1 mm that could be used as recipient vessels for free tissue transfer. The other preserved cadaver was used to develop surgical approaches to these vessels. Three board certified surgeons evaluated the written descriptions and illustrations of the approaches using fresh cadavers. Modifications to the surgical approaches were made based on recommendations from these surgeons.

RESULTS

Seven approaches were developed to isolate recipient vessels of the head and neck region. The infraorbital, temporal, and sublingual approaches were easily performed and provided excellent access to the vessels in the region. The approach to the caudal auricular vessels was found to be more difficult but modification of the approach resolved this problem. Access to the facial artery was difficult; it was consistently <1 mm in diameter and thus its use could not be recommended. The approach to the vessels in the cervical region was easily performed. Because of the large size of the external jugular vein and the common carotid artery, end-to-side anastomosis of the donor to recipient vessels is necessary. The large superficial cervical vessels were easily accessed by a lateral shoulder approach.

CONCLUSIONS

Surgical approaches to potential recipient vessels of the head and neck were consistently achieved and provided relatively easy access to the vessels. Clinical Relevance- The surgical approaches described in this report can be used to isolate arteries and veins of the head and neck that are >1 mm in diameter. These vessels are suitable for use as recipient vessels for free tissue transfer for reconstruction of complex wounds of the head and neck.

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

OBJECTIVE

To report treatment of severe mandibular malocclusion (after left partial hemimandibulectomy, approximately 7 cm gap).

STUDY DESIGN

Clinical report.

ANIMALS

A 14-month-old golden retriever.

METHODS

After corrective osteotomy of the right horizontal mandibular ramus, normal occlusion was reestablished and temporarily maintained while both mandibles were stabilized by miniplates on the lateral alveolar surface spanning the bilateral mandibular defects (right=1.5 cm, left=7 cm). A fenestrated, monocortical rib graft was positioned beneath the left gingival surface to protect the synthetic graft, which was secured to the miniplate. A mandibular reconstruction plate (right) and a locking mandibular reconstruction plate (left) were secured to the ventral borders of the mandibles. Recombinant bone morphogenetic protein-2 delivered in collagen tricalcium phosphate sponges (rhBMP-2 collagen-TCP sponge) was inserted into both mandibular defects.

RESULTS

New bone formation was identified at 3 months and bony remodeling was evident at recheck examinations up to 4 years. Scintigraphy (6 months, 1 year) confirmed graft revascularization and viability. Bone collected (1 year) from the left defect site had robust new bone formation and evidence of continued remodeling. Only minor complications were encountered during the postoperative period and were easily resolved.

CONCLUSIONS

Reconstruction of a large mandibular defect was facilitated by use of an osteoinductive factor (rhBMP-2 collagen-TCP sponge) as a graft substitute.

CLINICAL RELEVANCE

One-step salvage and reconstruction facilitated by use of an osteoinductive factor, as a graft substitute, may be an alternative strategy for repair of large mandibular defects.