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.

Long-term outcomes of atrophic/oligotrophic non-unions in dogs and cats treated with autologous iliac corticocancellous bone graft and circular external skeletal fixation: 19 cases (2014-2021).

OBJECTIVES: To determine the short- and long-term outcomes and complications in dogs and cats undergoing surgical treatment for viable oligotrophic and nonviable atrophic non-unions using circular external skeletal fixation and autologous corticocancellous bone graft. MATERIALS AND METHODS: In this case series, the medical records and radiographs of all dogs and cats with radius/ulna and tibia/fibula viable oligotrophic and nonviable atrophic non-unions treated with corticocancellous bone graft and circular external skeletal fixation at two referral veterinary hospitals between 2014 and 2021 were retrospectively reviewed. The long-term follow-up was 1 year or greater. RESULTS: Thirteen dogs and six cats with 19 non-union fractures met the inclusion criteria for the study. Eighteen non-union fractures (94.7%) healed and one did not. Five patients (26%) had minor perioperative period complications (<3 months). The patient that did not achieve bone union underwent revision surgery with internal fixation (plate and screws) and autologous cancellous bone graft. Fifteen (78.9%) cases returned to full function and three (15.8%) cases returned to acceptable function in the long-term follow-up period. CLINICAL SIGNIFICANCE: The use of circular external skeletal fixation associated with autologous corticocancellous bone graft for the treatment of radius/ulna and tibia/fibula atrophic/oligotrophic non-union fractures in dogs and cats was considered successful in the majority of patients and was free of major or catastrophic complications.

Erythropoietin as promoter of engraftment for treatment of radius/ulnar non-union fracture in a dog: Case report.

Background: Fractures with large bone defects and non-unions are a great challenge for veterinary orthopaedists. In small dog breeds, this complication is commonly encountered in fractures of the radius and ulna due to poorer vascularisation of the distal antebrachium region. Case Description: A case of radius/ulnar non-union in a 1.5-year-old Pinscher occurring after trauma and two successive unsuccessful osteosyntheses is described. During the operative revision, after the removal of existing bone implants, the bone defect was filled with cortical autologous bone graft. Autocancellous bone mixed with erythropoietin was applied proximally and distally to the cortical autograft for stimulation of bone healing. The post-operative period was without complications. As early as the 9th post-operative week, the animal was able to bear weight on the limb, without signs of lameness, pain, and swelling. Radiologically, a very good bridging of the graft was observed. Fifteen weeks after the operative revision, the fracture was completely healed with excellent clinical outcome. Conclusion: The application of autogenous cortical bone graft and cancellous autograft mixed with erythropoietin demonstrated an excellent therapeutic effect and resulted in complete regeneration of the large bone defect over a 15-week period.

Complications associated with cheek tooth extraction in the horse.

Common indications for cheek tooth extraction in the horse include dental fracture, periodontal disease, severe decay/ caries, mandibular fracture with alveolar/tooth involvement, and periapical abscess. Complications secondary to extraction of cheek teeth are prevalent. Typical complications may include retained root tip(s), collateral damage of neighboring teeth and alveolar bone, mandibular fracture non-union or delayed union, cemental ankylosis, dilacerated root(s), oroantral/oronasal fistula, palatal deviation of cheek teeth, bone sequestration, sinus involvement, alveolar plug failure, and palatine artery laceration. This paper presents a series of cases that had complications following cheek tooth extraction. Anticipation of problematic extractions, recognition of complications, and appropriate treatment will aid the clinician in managing the inevitable cheek tooth extraction complication.

Long-Term Assessment of Bone Regeneration in Nonunion Fractures Treated with Compression-Resistant Matrix and Recombinant Human Bone Morphogenetic Protein-2 in Dogs.

OBJECTIVE: The aim of this study was to assess bone density, bone architecture and clinical function of canine nonunion distal appendicular long bone fractures with a defect treated with fixation, compression-resistant matrix and recombinant human bone morphogenetic protein-2 (rhBMP-2). STUDY DESIGN: Prospective cohort study with dogs at least 1-year post treatment. Computed tomography was performed and quantitative measurements from previous fracture sites were compared with measurements from contralateral limbs. Subjective evaluation included gait assessment and palpation. RESULTS: Six patients met the inclusion criteria. The rhBMP-2 treated bone exhibited higher density at the periphery and lower density in the centre, similar to the contralateral limb. All patients were weight bearing on the treated limb and all fractures were healed. CONCLUSION: The rhBMP-2-treated bone underwent restoration of normal architecture and density. Acceptable limb function was present in all patients. The results of this study can serve as a basis for long-term response in treating nonunion fractures in veterinary patients.

Osteoprogenitor cell therapy in an equine fracture model.

OBJECTIVE: To compare the efficacy of osteoprogenitors in fibrin glue to fibrin glue alone in bone healing of surgically induced ostectomies of the fourth metacarpal bones in an equine model. STUDY DESIGN: Experimental. ANIMALS: Adult horses (n = 10). METHODS: Segmental ostectomies of the 4th metacarpal bone (MC4) were performed bilaterally in 10 horses. There was 1 treatment and 1 control limb in each horse. Bone defects were randomly injected with either fibrin glue and osteoprogenitor cells or fibrin glue alone. Radiography was performed every week until the study endpoint at 12 weeks. After euthanasia, bone healing was evaluated using radiography and histology. Analysis of radiographic data was conducted using a linear-mixed model. Analysis of histologic data was conducted using a general linear model. Statistical significance was set at P < .05. RESULTS: Radiographic grayscale data as a measure of bone healing revealed no significant difference between treatment and control limbs. Radiographic scoring results also showed that the treatment effect was not significant. Histologic analysis was consistent with radiographic analysis showing no significant difference between the area of bone present in treatment and control limbs. CONCLUSION: Injection of periosteal-derived osteoprogenitors in a fibrin glue carrier into surgically created ostectomies of MC4 does not accelerate bone healing when compared with fibrin glue alone.

Clinical application of recombinant human bone morphogenetic protein in cats and dogs: a review of 13 cases.

Databases (2001-2008) for cases in which recombinant bone morphogenetic protein (rhBMP) was used to aid in management of orthopedic disease were reviewed and cases were categorized as non-unions, delayed unions, and cases expected to heal with difficulty. If follow-up in the medical record was < 6 mo for live animals, owners were surveyed by telephone. Thirteen cases (11 dogs, 2 cats) were identified; OP-1 (rhBMP-7) was used in 3 cases and INFUSE (rhBMP-2) in 10. Mean time from injury to rhBMP use for non- and delayed union cases was 156 d; mean time from rhBMP use to radiographic healing was 101 d. No systemic side effects were reported. All patients achieved clinical and radiographic bone union following rhBMP administration. Recombinant human BMP was used in 13 veterinary patients to successfully achieve bone union without serious deleterious effects in a variety of clinical applications.

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.

Canine Elbow Dysplasia: Ununited Anconeal Process, Osteochondritis Dissecans, and Medial Coronoid Process Disease.

Elbow dysplasia is a major cause of front limb lameness in medium to large dog breeds. Underlying causes include ununited anconeal process, medial coronoid process disease, and osteochondritis dissecans. When a definitive diagnosis of elbow dysplasia is made, the surgeon can improve elbow function but cannot entirely prevent progression of osteoarthrosis. Conventional surgical treatment with joint debridement and removal of loose osteocartilaginous bodies is not rewarding if joint incongruity persists; the result is overloading and subchondral bone exposure with erosion of the cartilage of the medial humeral condyle and medial coronoid area of the ulna leading to medial compartment disease.

Transverse stress fractures of the proximal tibia in 10 cats with non-union patellar fractures.

Ten cats with a mean age of eight years and five months had suffered proximal transverse tibial fractures; in four of them both tibiae had fractured at different times. All the cats also had bilateral non-union patellar fractures, and nine of them had evidence of fractures elsewhere, including acetabular, ischial, humeral condylar and rib fractures, which had occurred before or after the tibial fractures. All the tibial fractures were proximal and transverse. Radiographically, there was thickening and sclerosis of the cranial cortex adjacent to and at the level of the fracture, changes that were compatible with stress fractures. The outcome of repair of the tibial fracture was known in nine of the cats; eight of them healed and one resulted in a non-union. Two of the cats were euthanased as a direct result of the fracture or complications with the repair.

Clinical Efficacy of Bone Reconstruction Surgery with Frozen Cortical Bone Allografts for Nonunion of Radial and Ulnar Fractures in Toy Breed Dogs.

OBJECTIVE: To evaluate the effectiveness of frozen cortical bone allografts (FCBA) in the treatment of severe radial and ulnar atrophic nonunion fractures. ANIMALS: Toy breed dogs with nonunion of radial and ulnar fractures (n = 15). METHODS: Severe atrophic nonunion fractures were treated with FCBA (eight infected and seven non-infected fractures). Radiographs obtained immediately after surgery, and 1, 2, 3, 6 and 12 months later were evaluated and scored for the periosteal reaction at the bone regeneration sites, the healing process in the bone connection areas at both the proximal and distal sites, and the bone remodelling process within the allografts. RESULTS: Improvements in the fracture-healing process and weight-bearing function were observed in all cases. Radiographic scores at the bone connection areas and within the allograft improved significantly over time (p < 0.05). There were not any significant differences in radiographic scores between the infected and non-infected groups. CLINICAL SIGNIFICANCE: Bone reconstruction with FCBA is effective in the treatment of radial and ulnar nonunion fractures associated with large bone defects, regardless of the infection status of the surgical site.

Use of stem-cell sheets expressing bone morphogenetic protein-7 in the management of a nonunion radial fracture in a Toy Poodle.

A 12-year-old castrated Toy Poodle was referred to the Kangwon National University Animal Hospital with an oligotrophic nonunion fracture in the distal 1/3 of the left radius and an intact ulna. After fixation by a locking plate and screws, adipose-derived mesenchymal stem-cell sheets expressing bone morphogenetic protein 7 (BMP-7) were transplanted to the fracture site to enhance the healing activity. The fracture was healed at 9 weeks after surgery. In the present case, the mesenchymal stem-cell sheets expressing BMP-7 promoted bone regeneration and healing in a nonunion fracture.

Outcome of nonunion fractures in dogs treated with fixation, compression resistant matrix, and recombinant human bone morphogenetic protein-2.

OBJECTIVES: To report the use of compression resistant matrix (CRM) infused with recombinant human bone morphogenetic protein (rhBMP-2) prospectively in the healing of nonunion long-bone fractures in dogs. METHODS: A longitudinal cohort of dogs that were presented with nonunion fractures were classified and treated with CRM soaked with rhBMP-2 and fracture fixation. They were followed with serial radiographs and evaluated for healing times and complications according to the time frame and definitions previously established for orthopaedic clinical cases. RESULTS: Eleven nonunion fractures in nine dogs were included. Median healing time was 10 weeks (range: 7-20 weeks). Major perioperative complications due to bandage morbidity were encountered in two of 11 limbs and resolved. All other complications were minor. They occurred perioperatively in eight of 11 limbs. Minor follow-up complications included short-term in one of two limbs, mid-term in one of three, and long-term in four of five limbs. Nine limbs returned to full function and two limbs returned to acceptable function at the last follow-up. CLINICAL SIGNIFICANCE: Nonunion fractures given a poor prognosis via standard-of-care treatment were successfully repaired using CRM with rhBMP-2 accompanying fixation. These dogs, previously at high risk of failure, returned to full or acceptable function.

Evaluation of nonunion fractures in dogs by use of B-mode ultrasonography, power Doppler ultrasonography, radiography, and histologic examination.

OBJECTIVE: To investigate the use of ultrasonography to assess nonunion of fractures in dogs and to compare results of ultrasonography, radiography, and histologic examination. SAMPLE POPULATION: 8 nonunion fractures in 6 dogs (1 each in 5 dogs and 3 in 1 dog); dogs ranged from 7 to 94 months of age and weighed 6 to 30 kg. PROCEDURES: Diagnostic assessment consisted of complete clinical and orthopedic examinations, radiography, B-mode (brightness mode) ultrasonography, and power Doppler ultrasonography. Biopsy samples were obtained during surgery for histologic examination. They were stained with H&E and immunolabeled by use of anti-CD31 antibodies. Correlations of power Doppler score, power Doppler count, vessel area, and radiographic prediction with the mean number of vessels counted per hpf were derived. RESULTS: Radiographically, 7 of 8 nonunion fractures were diagnosed as atrophic and were therefore estimated to be nonviable. Vascularity of nonunion fractures during power Doppler ultrasonography ranged from nonvascularized to highly vascularized. Absolute vessel count during histologic examination ranged from 0 to 63 vessels/hpf; 5 nonunion sites had a mean count of > 10 vessels/hpf. Vascularity during power Doppler ultrasonography was highly correlated with the number of vessels per hpf, whereas the correlation between the radiographic assessment and histologic evaluation was low. CONCLUSIONS AND CLINICAL RELEVANCE: Radiographic prediction of the viability of nonunion fractures underestimated the histologically assessed vascularity of the tissue. Power Doppler ultrasonography provided a more accurate estimation of the viability of the tissue and therefore the necessity for debridement and autografts during revision surgery.

Bovine xenograft application for treatment of a metatarsal nonunion fracture in an alpaca (Vicugna pacos).

CASE HISTORY: A 15-year-old female huacaya alpaca (Vicugna pacos) was referred because of a non-weight-bearing lameness (4/4) in the left pelvic limb caused by a grade three open metatarsal fracture. The referring veterinarian treated the fracture with conservative management using bandages, but it progressively evolved to a non-union. CLINICAL FINDINGS AND DIAGNOSIS: Clinical examination revealed external wounds on the medial and lateral surfaces of the metatarsus. Radiographs confirmed an open, nonarticular, displaced, diaphyseal fracture of the left metatarsus. TREATMENT AND OUTCOME: Cancellous bone was sourced from bovine proximal and distal femur epiphyses, followed by a thermal shock procedure to achieve decellularisation, to produce a xenograft. Open reduction and internal fixation of the fracture using locking plates was performed. Alignment of the fracture fragments was corrected and the xenograft was placed at the debrided fracture site to stimulate and harness osteogenesis in situ. Clinical and radiographic follow-up was performed up to 40 weeks postoperatively. Clinical evaluations revealed that the alpaca gradually increased weight bearing following bandage removal 10 days after surgery. Serial radiographs showed correct alignment of the left metatarsus, progressive bone modelling and, complete bone union at 12 weeks. Ten months postoperatively the alpaca showed no signs of lameness and resumed normal activity. CLINICAL RELEVANCE: For management of a metatarsal non-union, a combination of bovine xenograft application and angular stable internal fixation progressed toward an excellent long-term recovery.

Incidence of and predisposing factors for nonunion of fractures involving the appendicular skeleton in cats: 18 cases (1998-2002).

OBJECTIVE: To identify the most common sites of and possible predisposing factors for nonunions in cats with fractures of the appendicular skeleton. DESIGN: Retrospective study. ANIMALS: 344 cats treated for fractures between 1998 and 2002, 18 of which developed nonunions. PROCEDURES: Information collected from the medical records included signalment; type of trauma; fracture location, orientation, and type; degrees of displacement and comminution; treatment; and outcome. RESULTS: The tibia and proximal portion of the ulna were identified as the most common sites for nonunions. Factors significantly associated with development of a nonunion included age, body weight, affected bone, fracture type, degree of comminution, and fixation type, with older cats, heavier cats, cats with fractures of the tibia or proximal portion of the ulna, cats with open fractures, cats with comminuted fractures, and cats with fractures stabilized with a type II external skeletal fixator being significantly more likely to develop a nonunion. Eleven of the 18 cats with nonunions had a successful outcome following treatment of the nonunion. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that in cats, fractures involving the tibia and proximal portion of the ulna are more likely to develop nonunions than are fractures involving other sites but that many factors may increase the risk of nonunion. Use of excessively large and rigid type II external skeletal fixators may be associated with development of nonunions; however, type II external skeletal fixators were commonly used to stabilize fractures in sites predisposed to nonunion.

Correlation of serum alkaline phosphatase activity with the healing process of long bone fractures in dogs.

BACKGROUND: Bone healing is monitored mainly by physical and serial radiologic examinations of the fracture site. However, it is sometimes difficult to distinguish a delayed union from a nonunion, and advanced imaging techniques may not be available. Serum biochemical markers of bone formation, such as alkaline phosphatase (ALP) activity, may be clinically useful in evaluating the progress of healing. OBJECTIVE: The purpose of this study was to correlate serial values of serum ALP activity with the process of fracture healing in dogs and to assess its potential as a postsurgical prognostic indicator. METHODS: Changes in serum ALP activity were studied in 83 dogs with closed long bone diaphyseal fractures treated surgically. Physical and radiologic examinations of the fracture site and determination of serum ALP activity and calcium (Ca) and phosphate (P) concentrations were performed on admission (day 0); postoperatively on days 10, 20, and 30; and subsequently on a monthly basis until bone union was completed or signs of nonunion were evident. The dogs were allocated into 3 groups with respect to the fracture healing progress as documented by physical and serial radiologic examination. RESULTS: Group A dogs (n=35) developed a medium-sized callus that led to bone union within 2 months. Group B dogs (n=36) had a hypertrophic callus and delayed union, within 3-5 months. Group C dogs (n=12) had slow progress in fracture healing, with minimal callus formation during a 2-month period. Changes in mean serum ALP activity followed the same pattern in groups A and B, reaching a maximum level on day 10. Group A values returned to normal within 2 months, at which point bone union was complete, whereas group B values remained increased and returned to normal within 3-5 months, thus correlating with delayed union. In Group C, mean serum ALP activities showed no significant changes during the 2-month follow-up period, consistent with failure of bone union (nonunion). Serum P and Ca changes followed a proportional and inverse pattern to ALP changes, respectively. CONCLUSION: Serial determination of serum ALP activity during fracture healing could be an additional tool in predicting fractures at risk of developing a nonunion, helping the clinician to choose the appropriate intervention.

Evaluation of serum biochemical markers of bone metabolism for early diagnosis of nonunion and infected nonunion fractures in rabbits.

OBJECTIVE: To evaluate the use of serum concentrations of biochemical markers of bone metabolism (osteocalcin [OC], bone-specific alkaline phosphatase [BS-ALP], and deoxypyridinoline [DPYR]) to compare healing in infected versus noninfected fractures and in fractures with normal repair versus delayed (nonunion) repair in rabbits. ANIMALS: 32 female 9- to 10-month-old New Zealand White rabbits. PROCEDURE: A femoral fracture defect was made in each rabbit. Rabbits were assigned to the following groups: the bone morphogenetic-2 gene treatment group with either noninfected nonunion or infected (ie, inoculation of defects with Staphylococcus aureus) nonunion fractures or the luciferase (control) gene treatment group with either noninfected nonunion or infected nonunion fractures. Serum samples were obtained before surgery (time 0) and 4, 8, 12, and 16 weeks after surgery. Callus formation and lysis grades were evaluated radiographically at 16 weeks. RESULTS: Serum OC and BS-ALP concentrations decreased from time 0 at 4 weeks, peaked at 8 weeks, and then decreased. Serum DPYR concentration peaked at 4 weeks and then decreased, independent of gene treatment group or fracture infection status. Compared with rabbits with noninfected fractures, those with infected fractures had lower serum OC and BS-ALP concentrations at 4 weeks, higher serum OC concentrations at 16 weeks, and higher serum DPYR concentrations at 4, 8, and 16 weeks. Combined serum OC, BS-ALP, and DPYR concentrations provided an accuracy of 96% for prediction of fracture infection status at 4 weeks. CONCLUSIONS AND CLINICAL RELEVANCE: Measurement of multiple serum biochemical markers of bone metabolism could be useful for clinical evaluation of fracture healing and early diagnosis of osteomyelitis.

Effect of hyperbaric oxygen treatment on incorporation of an autogenous cancellous bone graft in a nonunion diaphyseal ulnar defect in cats.

OBJECTIVE: To determine whether hyperbaric oxygen treatment (HBOT) would affect incorporation of an autogenous cancellous bone graft in diaphyseal ulnar defects in cats. ANIMALS: 12 mature cats. PROCEDURE: Bilateral nonunion diaphyseal ulnar defects were created in each cat. An autogenous cancellous bone graft was implanted in 1 ulnar defect in each cat, with the contralateral ulnar defect serving as a nongrafted specimen. Six cats were treated by use of hyperbaric oxygen at 2 atmospheres absolute for 90 minutes once daily for 14 days, and 6 cats were not treated (control group). Bone labeling was performed, using fluorochrome markers. Cats were euthanatized 5 weeks after implanting, and barium sulfate was infused to evaluate vascularization of grafts. Ulnas were evaluated by use of radiography, microangiography, histologic examination, and histomorphometric examination. RESULTS: Radiographic scores did not differ between treatment groups. Microangiographic appearance of grafted defects was similar between groups, with all having adequate vascularization. Differences were not observed between treated and nontreated groups in the overall histologic appearance of decalcified samples of tissue in grafted defects. Mean distance between fluorescent labels was significantly greater in cats given HBOT than in nontreated cats. Median percentage of bone formation in grafted defects was significantly greater in cats given HBOT. CONCLUSIONS: Hyperbaric oxygen treatment increased the distance between fluorescent labels and percentage of bone formation when incorporating autogenous cancellous bone grafts in induced nonunion diaphyseal ulnar defects in cats, but HBOT did not affect revascularization, radiographic appearance, or qualitative histologic appearance of the grafts.

Repair of a delayed-union stress fracture of the dorsal cortex of a metacarpal bone in a horse.

A delayed union metacarpal stress fracture was repaired in a horse, using lag-screw fixation in conjunction with dc electrical stimulation. Twelve weeks after surgery, radiographic and scintigraphic evaluations revealed that the fracture line was not discernible and that there was a decrease in radiopharmaceutic uptake, as compared with that in previous bone imaging studies. In this horse, DC stimulation of a delayed union stress fracture in a bone resulted in a healing pattern similar to that in human beings with delayed union fractures when treated with electrical stimulation.