Outcomes of 25 female dogs treated for ectopic ureters by open surgery or cystoscopic-guided laser ablation.

OBJECTIVE: To report outcomes after the correction of ectopic ureter (EU) by open surgery or cystoscopic-guided laser ablation (CLA) in female dogs. STUDY DESIGN: Retrospective study from 2011 to 2018. ANIMALS: Twenty-five female dogs. METHODS: Data collected included signalment, clinicopathologic data, procedural data, complications, and short-term and long-term outcomes. Complications were graded as minor or major if a surgical revision was required. Continence status was scored subjectively (1 = completely incontinent to 10 = fully continent). RESULTS: Fifteen dogs had bilateral EU and 24 had intramural EU (iEU). Open surgical correction included 13 neoureterostomies, 2 neocystoureterostomies, and a combination of these in 2 dogs. Eight dogs underwent CLA. Eighteen dogs experienced minor complications (72%), and 2 experienced major complications (8%). One-month postoperative continence was achieved in 20/25 (80%) dogs (median score of 10). Incontinence recurred at a median time of 24.9 months in 5 dogs but responded to medical treatment. Overall, dogs remained continent for 66 months (median) and 22/25 (88%) dogs achieved continence with adjunction of medical/surgical treatment in incontinent ones. Fewer minor complications and postoperative recurrences of incontinence were documented after CLA than neoureterostomy (P < .01 and P < .05). CONCLUSION: Ectopic ureter correction by open surgery or CLA resulted in a subjectively good prognosis, most dogs reaching continence within a month of surgery, although incontinence occasionally recurred in the long term. CLA was associated with fewer complications and incontinence recurrences than neoureterostomy. CLINICAL SIGNIFICANCE: Cystoscopic-guided laser ablation should be preferred to correct iEU to prevent short-term complications and the recurrence of incontinence. Further studies should investigate the cause of postoperative recurrence of urinary incontinence.

Biological and biomechanical evaluation of the ligament advanced reinforcement system (LARS AC) in a sheep model of anterior cruciate ligament replacement: a 3-month and 12-month study.

PURPOSE: The purposes of this study were to assess tissue ingrowth within the Ligament Advanced Reinforcement System (LARS) artificial ligament (LARS AC; LARS, Arc sur Tille, France) and to study the biomechanical characteristics of the reconstructed knees in a sheep model of anterior cruciate ligament (ACL) replacement. METHODS: Twenty-five female sheep underwent excision of the proximal third of the left ACL and intra-articular joint stabilization with a 44-strand polyethylene terephthalate ligament (mean ultimate tensile failure load, 2,500 N). Animals were killed either 3 or 12 months after surgery. Explanted knees were processed for histology (n = 10) or mechanical tests including tests of laxity and loading to failure in tension (n = 15). RESULTS: Well-vascularized tissue ingrowth within the artificial ligament was only observed in the portions of the ligament in contact with the host's tissues (native ligament and bone tunnels). Ligament wear was observed in 40% of explanted knees. The ultimate tensile failure loads of the operated knees at both time points were inferior to those of the contralateral, intact knees (144 ± 69 N at 3 months and 260 ± 126 N at 12 months versus 1,241 ± 270 N and 1,218 ± 189 N, respectively) (P < .01). In specimens with intact artificial ligaments, failure occurred by slippage from the bone tunnels in all specimens explanted 3 months postoperatively and in half of the specimens explanted 12 months postoperatively. CONCLUSIONS: This study provides evidence that the LARS AC has a satisfactory biointegration but that it is not suitable for ACL replacement if uniform tissue ingrowth is contemplated. Despite good clinical performance up to 1 year after implantation, none of the reconstructions approached the mechanical performance of the normal ACL in the ovine model. Partial tearing of the artificial ligament, which led to a significant decrease in ultimate tensile strength, was observed in 40% of cases in the ovine model. CLINICAL RELEVANCE: The LARS is not a suitable scaffold for ACL replacement. Further animal studies are needed to evaluate its potential for augmentation of ligament repair.

A fistula flap technique for correction of type II atresia ani and rectovaginal fistula in 6 kittens.

OBJECTIVE: To report a surgical technique and long-term outcomes of type II atresia ani (AA) and rectovaginal fistula (RvF) correction, using a fistula flap technique in kittens. STUDY DESIGN: Clinical study. ANIMALS: Domestic shorthaired female kittens (n = 6) with type II AA-RvF. METHODS: Diagnosis of type II AA-RvF was made by clinical examination and vaginography. The anomaly was surgically corrected by a fistula flap technique for reconstruction of the anal canal and anus, and by vaginoplasty. Kittens were monitored for short and long-term complications. RESULTS: All 6 kittens were fecal and urinary continent in the immediate postoperative period. Postoperative complications occurred in 2 kittens: partial dehiscence between the anal and vaginal opening and a stenosis at the level of the rectal mucocutaneous anastomosis. Dehiscence healed by second intention and stenosis was treated by anoplasty. No long-term complications (median follow-up, 12 months; range, 12-17 months) were observed. CONCLUSIONS: Reconstruction of the anal canal and anus using the fistula as a local flap in combination with a vaginoplasty can be effective to treat feline type II AA and RvFs.

3D-Printed Osteoinductive Polymeric Scaffolds with Optimized Architecture to Repair a Sheep Metatarsal Critical-Size Bone Defect.

The reconstruction of critical-size bone defects in long bones remains a challenge for clinicians. A new osteoinductive medical device is developed here for long bone repair by combining a 3D-printed architectured cylindrical scaffold made of clinical-grade polylactic acid (PLA) with a polyelectrolyte film coating delivering the osteogenic bone morphogenetic protein 2 (BMP-2). This film-coated scaffold is used to repair a sheep metatarsal 25-mm long critical-size bone defect. In vitro and in vivo biocompatibility of the film-coated PLA material is proved according to ISO standards. Scaffold geometry is found to influence BMP-2 incorporation. Bone regeneration is followed using X-ray scans, µCT scans, and histology. It is shown that scaffold internal geometry, notably pore shape, influenced bone regeneration, which is homogenous longitudinally. Scaffolds with cubic pores of ≈870 µm and a low BMP-2 dose of ≈120 µg cm-3 induce the best bone regeneration without any adverse effects. The visual score given by clinicians during animal follow-up is found to be an easy way to predict bone regeneration. This work opens perspectives for a clinical application in personalized bone regeneration.

Surgically treated congenital cleft palate in a 4-month-old kitten: medium-term clinical and CT assessment.

Case summary: A 4-month-old female domestic shorthair kitten was presented for a congenital cleft palate causing nasal discharge and sneezing episodes. CT revealed a palatal bone defect involving 20% of the palatal area. Surgical correction of both the hard and soft palate defects was performed using the overlapping and medially positioned flap techniques, respectively. Complete healing of the wound and full resolution of the clinical signs occurred within a 1-month period. At 2 months postoperatively, two punctiform oronasal fistulae were observed rostrally without associated clinical signs. Control CT, performed 6 months postoperatively, revealed a 50% enlargement of the palatal bone defect. At 12 months postoperatively, the cat was still in good general condition without any clinical signs. Relevance and novel information: To the best of our knowledge, this is the first report to describe the treatment of a congenital cleft palate in a kitten using the overlapping flap technique with a successful medium-term clinical outcome, despite the formation of two oronasal fistulae. This suggests that, as in dogs, full restoration of oronasal compartmentation is not mandatory to achieve functional outcome. The increase of the palatal bone defect over time may play a role in late oronasal fistulae formation and should be considered for surgical planning.

A wear model to predict damage of reconstructed ACL.

Impingement with surrounding tissues is a major cause of failure of anterior cruciate ligament reconstruction. However, the complexity of the knee kinematics and anatomical variations make it difficult to predict the occurrence of contact and the extent of the resulting damage. Here we hypothesise that a description of wear between the reconstructed ligament and adjacent structures captures the in vivo damage produced with physiological loadings. To test this, we performed an in vivo study on a sheep model and investigated the role of different sources of damage: overstretching, excessive twist, excessive compression, and wear. Seven sheep underwent cranial cruciate ligament reconstruction using a tendon autograft. Necropsy observations and pull-out force measurements performed postoperatively at three months showed high variability across specimens of the extent and location of graft damage. Using 3D digital models of each stifle based on X-ray imaging and kinematics measurements, we determined the relative displacements between the graft and the surrounding bones and computed a wear index describing the work of friction forces underwent by the graft during a full flexion-extension movement. While tensile strain, angle of twist and impingement volume showed no correlation with pull-out force (ρ = -0.321, p = 0.498), the wear index showed a strong negative correlation (r = -0.902, p = 0.006). Moreover, contour maps showing the distribution of wear on the graft were consistent with the observations of damage during the necropsy. These results demonstrate that wear is a good proxy of graft damage. The proposed wear index could be used in implant design and surgery planning to minimise the risk of implant failure. Its application to sheep can provide a way to increase preclinical testing efficiency.

Remnants-preserving ACL reconstruction using direct tendinous graft fixation: a new rat model.

BACKGROUND: Anterior cruciate ligament (ACL) repair techniques are new emerging strategies prevailing, in selected cases, over standard reconstruction of the ACL with excision of its remnants. Mid-substance ACL tears represent a challenge for ACL repair techniques, and remnants-preserving ACL reconstruction (rp-ACLR) using an autograft remains the recommended treatment in this situation. However, morbidity associated with the autograft harvesting prompts the need for alternative surgical strategies based on the use of synthetic scaffolds. Relevant small animal models of mid-substance tears with ACL remnants preservation and reconstruction are necessary to establish the preliminary proof of concept of these new strategies. METHODS: A rat model of rp-ACLR using a tendinous autograft after complete mid-substance ACL transection was established. Twelve weeks following surgery, clinical outcomes and knee joints were assessed through visual gait analysis, Lachman tests, thigh perimeter measurements, magnetic resonance imaging, micro-computed tomography, and histology, to evaluate the morbidity of the procedure, accuracy of bone tunnel positioning, ACL remnants fate, osteoarthritis, and autograft bony integration. Results were compared with those obtained with isolated ACL transection without reconstruction and to right non-operated knees. RESULTS AND DISCUSSION: Most operated animals were weight-bearing the day following surgery, and no adverse inflammatory reaction has been observed for the whole duration of the study. Autograft fixation with cortical screws provided effective graft anchorage until sacrifice. Healing of the transected ACL was not observed in the animals in which no graft reconstruction was performed. rp-ACLR was associated with a reduced degeneration of the ACL remnants (p = 0.004) and cartilages (p = 0.0437). Joint effusion and synovitis were significantly lower in the reconstructed group compared to the transected ACL group (p = 0.004). Most of the bone tunnel apertures were anatomically positioned in the coronal and/or sagittal plane. The most deviated bone tunnel apertures were the tibial ones, located in median less than 1 mm posteriorly to anatomical ACL footprint center. CONCLUSION: This study presents a cost-effective, new relevant and objective rat model associated with low morbidity for the preliminary study of bio-implantable materials designed for remnants-preserving ACL surgery after mid-substance ACL tear.

One stage functional end-to-end stapled intestinal anastomosis and resection performed by nonexpert surgeons for the treatment of small intestinal obstruction in 30 dogs.

OBJECTIVES: To describe stapled 1-stage functional end-to-end intestinal anastomosis for treatment of small intestinal obstruction in dogs and evaluate outcome when the technique is performed by nonexpert surgeons after limited training in the technique. STUDY DESIGN: Case series. ANIMALS: Dogs (n=30) with intestinal lesions requiring an enterectomy. METHODS: Stapled 1-stage functional end-to-end anastomosis and resection using a GIA-60 and a TA-55 stapling devices were performed under supervision of senior residents and faculty surgeons by junior surgeons previously trained in the technique on pigs. Procedure duration and technical problems were recorded. Short-term results were collected during hospitalization and at suture removal. Long-term outcome was established by clinical and ultrasonographic examinations at least 2 months after surgery and from written questionnaires, completed by owners. RESULTS: Mean±SD procedure duration was 15±12 minutes. Postoperative recovery was uneventful in 25 dogs. One dog had anastomotic leakage, 1 had a localized abscess at the transverse staple line, and 3 dogs developed an incisional abdominal wall abscess. No long-term complications occurred (follow-up, 2-32 months). CONCLUSION: Stapled 1-stage functional end-to-end anastomosis and resection is a fast and safe procedure in the hand of nonexpert but trained surgeons.

Effect of the Bone Morphogenetic Protein-2 Doses on the Osteogenic Potential of Human Multipotent Stromal Cells- Containing Tissue Engineered Constructs.

IMPACT STATEMENT: A strategy for improving the efficacy of stem cell-based bone tissue engineering (TE) constructs is to combine bone morphogenetic protein-2 (BMP-2) with multipotent stromal cells (MSC). Previous studies on the potential cooperative effect of BMP-2 with human multipotent stromal cells (hMSCs) on bone formation in vivo have, however, shown contradictory results likely due to the various and/or inappropriate BMP-2 doses. Our results provided evidence that the addition of BMP-2 at low dose only was beneficial to improve the osteogenic potential of hMSCs-containing TE constructs, whereas BMP-2 delivered at high dose overcame the advantage of combining this growth factor with hMSCs. This new knowledge will help in designing improved combination strategies for tissue regeneration with better clinical outcomes.

Laparoscopic ovariectomy with a single-port multiple-access device in seven African lionesses (Panthera leo).

CASE DESCRIPTION 7 privately owned female African lions (Panthera leo) that had been bred for public exhibition and were housed in outdoor pens were evaluated prior to undergoing elective ovariectomy. CLINICAL FINDINGS All animals were healthy. Median age was 15 months (range, 9 to 34 months), and median body weight was 71 kg (156 lb; range, 48 to 145 kg [106 to 319 lb]). TREATMENT AND OUTCOME Surgical sterilization by means of single-incision laparoscopic ovariectomy was elected. A 2- to 3-cm-long skin incision was made just caudal to the umbilicus, and a single-port multiple-access device was bluntly inserted through the incision. Traction was maintained with stay sutures to provide counterpressure, and three 5-mm-diameter cannulae were introduced through the device's access channels with a blunt trocar. The abdomen was insufflated to a pressure of 12 mm Hg with CO2. Each ovary was grasped and suspended with a standard 36-cm-long laparoscopic grasper, and ovariectomy was performed with a 5-mm vessel sealer and divider device. Because of the depth of subcutaneous fat, extensive subcutaneous dissection was necessary to insert the single-port device. In contrast, fat content of the mesovarium was minimal and did not vary markedly among animals. Subjectively, single-incision laparoscopic ovariectomy was easily performed, but all surgeons had experience in laparoscopic surgery. Median duration of the surgical procedure was 29 minutes (range, 21 to 49 minutes). No perioperative complications were encountered. CLINICAL RELEVANCE Findings suggested that the single-incision laparoscopic technique may be an acceptable, minimally invasive option for ovariectomy of large felids.

Stabilization of Olecranon Fractures by Tension Band Wiring or Plate Osteosynthesis: A Retrospective Study of 41 Cases.

OBJECTIVES: This article aimed to describe olecranon fracture in dogs and cats and their stabilization with tension band wiring or plate osteosynthesis, and to evaluate complications associated with each technique. METHODS: Medical records of cats and dogs that had been surgically treated for olecranon fractures with either tension band wiring or plate osteosynthesis were retrospectively reviewed. The surgical technique, complications and long-term outcomes were assessed. RESULTS: Forty-one olecranon fractures were included. Fractures were articular, comminuted and open in 90, 31 and 27% of cases, respectively. Tension band wiring and plate osteosynthesis were performed in 22 and 19 fractures, respectively. Complications occurred more commonly after tension band wiring (74%) compared with plate osteosynthesis (27%) (p = 0.002) and these were probably related to it being used in comminuted fractures (p = 0.01) or to errors in technique. Minor complications included Kirschner wires migration (n = 5), pain (n = 3), osteomyelitis (n = 3), skin breakdown (n = 3) and seroma (n = 1). Implant failure requiring further fixation (n = 4) was observed only in the tension band wiring group. Other major complications included skin wound debridement and closure (n = 1) and chronic lameness requiring implant removal (n = 7). Long-term functional outcomes were excellent regardless of the technique used. CLINICAL SIGNIFICANCE: Plate osteosynthesis should be performed for olecranon fracture repair if technically feasible.

Long-bone critical-size defects treated with tissue-engineered grafts: a study on sheep.

Standardized particulate bone constructs, obtained by expanding autologous mesenchymal stem cells (MSCs) onto coral granules in vitro, were transplanted into long-bone, critical-size defects in sheep. Control experiments were also performed in which autologous bone grafts were implanted. Defect cavities were lined with a preformed vascularized membrane (induced by temporarily inserting a cement spacer for 6 weeks prior to bone construct implantation), which served as a mold keeping the engineered bone granules in place. Radiographic, histological, and computed tomographic tests performed 6 months later showed that the osteogenic abilities of the engineered construct and autograft were significantly greater than those of coral scaffold alone. No significant differences were found between the amount of newly formed bone in defects filled with coral/MSCs and those filled with autograft, yet radiological scores differed significantly between the two groups (21% and 100% healed cortices, respectively). The present study on a clinically relevant animal model provides the first evidence that standardized particulate bone constructs can be used to repair large bone defects and that their osteogenic ability approaches that of bone autograft, the bone repair benchmark. By proving feasibility, the present study makes possible the treatment of segmental bone losses with bone constructs engineered from granules, a process which is much simpler than preparing customized massive constructs using computer-assisted techniques. Important parameters, such as the rate of scaffold resorption and the number of MSCs to be seeded on the scaffolds, need to be optimized before reaching pertinent definitive conclusions.

Bone haemophilic pseudotumour of the ulna: A rare complication of haemophilia in a dog.

OBJECTIVES: This case report describes for the first time a bone haemophilic pseudotumour in a dog. CASE DESCRIPTION: A seven-month-old German Shepherd male dog was presented with the complaint of a forelimb weight-bearing lameness with major swelling that expanded dramatically after fine needle aspiration. Radiographs showed a large, well-defined ulnar diaphyseal cystic-like osteolytic lesion. Based on prolonged activated partial thromboplastin time (aPTT) and low factor VIII activity, haemophilia A was diagnosed. Bone scintigraphy, computed tomography, magnetic resonance imaging, and histological findings definitely ruled out malignant neoplasia or inflammation and strongly supported a bone haemophilic pseudotumour over an aneurysmal bone cyst. Segmental ulnar resection  and replacement by a polymethylmethacrylate spacer combined with perioperative bleeding management resulted in a successful outcome. DISCUSSION: This case provided evidence that a bone haemophilic pseudotumour may be the sole presenting clinical sign of haemophilia A in dogs. Early diagnosis, based on history and magnetic resonance imaging findings, is imperative for prompt treatment leading to successful outcome. It is challenging as fine needle aspiration or biopsy is contraindicated. As described in humans, surgical excision of the lesion combined with management of severe postoperative bleeding was associated with successful outcome in the present case. CLINICAL SIGNIFICANCE: A bone haemophilic pseudotumour should be considered in the differential diagnosis of expanding mass associated with osteolysis, especially in young male dogs. Perioperative monitoring of the bleeding disorder and subsequent FVIII replacement therapy was of paramount importance in the present case.

Bone tissue response induced by bioactive polymer functionalized Ti6Al4V surfaces: In vitro and in vivo study.

Ti6Al4V is commonly used for orthopedic applications. This study was designed to test the potentially added benefit of Ti6Al4V functionalized with a bioactive polymer poly(sodium styrene sulfonate) both in vitro and in vivo. Cell-based assays with MC3T3-E1 osteoblast-like cells were used to measure the cell adhesion strength, cell spreading, focal contact formation, cell differentiation and the mineralization of extracellular matrix on grafted and ungrafted Ti6Al4V discs in combination with FBS and collagen type I. Bone morphogenetic protein-2 (BMP-2) was also included in the cell differentiation assay. Results showed that the grafted surface combined with collagen I gave superior levels in every parameter tested with cell-based assays and was almost equivalent to BMP-2 for cell differentiation. In vivo testing was conducted in rabbits (n=42) with cylinders of grafted and ungrafted Ti6Al4V implanted in defects made to the femoral and lateral condyles and animals that were maintained to 1, 3 and 12months. Hydroxyapatite coated Ti6Al4V cylinders were included as a clinical reference control. Osseointegration was assessed post-mortem using histomorphometric analysis conducted on resin sections of explanted undecalcified bone. Two histomorphometric parameters, that of bone-to-implant contact and the bone area, were analyzed by a trained observer blinded to sample identity. Results showed osseointegration on grafted Ti6Al4V was marginally better than both ungrafted and hydroxyapatite coated Ti6Al4V. Overall, the study found that the grafted Ti6Al4V significantly promoted all aspects of osteogenesis tested in vitro and, although in vivo outcomes were less compelling, histomorphometry showed osseointegration of grafted Ti6Al4V implants was equivalent or better than controls.

Low-dose BMP-2 and MSC dual delivery onto coral scaffold for critical-size bone defect regeneration in sheep.

Tissue-engineered constructs (TECs) combining resorbable calcium-based scaffolds and mesenchymal stem cells (MSCs) have the capability to regenerate large bone defects. Inconsistent results have, however, been observed, with a lack of osteoinductivity as a possible cause of failure. This study aimed to evaluate the impact of the addition of low-dose bone morphogenetic protein-2 (BMP-2) to MSC-coral-TECs on the healing of clinically relevant segmental bone defects in sheep. Coral granules were either seeded with autologous MSCs (bone marrow-derived) or loaded with BMP-2. A 25-mm-long metatarsal bone defect was created and stabilized with a plate in 18 sheep. Defects were filled with one of the following TECs: (i) BMP (n = 5); (ii) MSC (n = 7); or (iii) MSC-BMP (n = 6). Radiographic follow-up was performed until animal sacrifice at 4 months. Bone formation and scaffold resorption were assessed by micro-CT and histological analysis. Bone union with nearly complete scaffold resorption was observed in 1/5, 2/7, and 3/6 animals, when BMP-, MSC-, and MSC-BMP-TECs were implanted, respectively. The amount of newly formed bone was not statistically different between groups: 1074 mm3 [970-2478 mm3 ], 1155 mm3 [970-2595 mm3 ], and 2343 mm3 [931-3276 mm3 ] for BMP-, MSC-, and MSC-BMP-TECs, respectively. Increased scaffold resorption rate using BMP-TECs was the only potential side effect observed. In conclusion, although the dual delivery of MSCs and BMP-2 onto a coral scaffold further increased bone formation and bone union when compared to single treatment, results were non-significant. Only 50% of the defects healed, demonstrating the need for further refinement of this strategy before clinical use. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2637-2645, 2017.

Establishment of a Segmental Femoral Critical-size Defect Model in Mice Stabilized by Plate Osteosynthesis.

The use of tissue-engineered bone constructs is an appealing strategy to overcome drawbacks of autografts for the treatment of massive bone defects. As a model organism, the mouse has already been widely used in bone-related research. Large diaphyseal bone defect models in mice, however, are sparse and often use bone fixation which fills the bone marrow cavity and does not provide optimal mechanical stability. The objectives of the current study were to develop a critical-size, segmental, femoral defect in nude mice. A 3.5-mm mid-diaphyseal femoral ostectomy (approximately 25% of the femur length) was performed using a dedicated jig, and was stabilized with an anterior located locking plate and 4 locking screws. The bone defect was subsequently either left empty or filled with a bone substitute (syngenic bone graft or coralline scaffold). Bone healing was monitored noninvasively using radiography and in vivo micro-computed-tomography and was subsequently assessed by ex vivo micro-computed-tomography and undecalcified histology after animal sacrifice, 10 weeks postoperatively. The recovery of all mice was excellent, a full-weight-bearing was observed within one day following the surgical procedure. Furthermore, stable bone fixation and consistent fixation of the implanted materials were achieved in all animals tested throughout the study. When the bone defects were left empty, non-union was consistently obtained. In contrast, when the bone defects were filled with syngenic bone grafts, bone union was always observed. When the bone defects were filled with coralline scaffolds, newly-formed bone was observed in the interface between bone resection edges and the scaffold, as well as within a short distance within the scaffold. The present model describes a reproducible critical-size femoral defect stabilized by plate osteosynthesis with low morbidity in mice. The new load-bearing segmental bone defect model could be useful for studying the underlying mechanisms in bone regeneration pertinent to orthopaedic applications.

Complications of appendicular fracture repair in cats and small dogs using locking compression plates.

OBJECTIVE: Our objectives were: 1) to review the complications associated with stabilization of appendicular fractures in cats and small dogs using locking compression plates (LCP), and 2) to identify factors that could influence fixation construct stability. STUDY DESIGN: Retrospective clinical study. MATERIALS AND METHODS: Medical and radiographic records of cats and small dogs with appendicular fractures treated with LCP were reviewed. Only cases with adequate follow-up to document clinical union and cases for which complications appeared before the clinical union were included. Complications were classified as implant-related complications or other complications. Cases with implant-related complications were compared to cases with non-implant-related complications for differences in signalment (species, age, body weight, multiple fractures), fracture location and type (fractured bone, fracture localization, closed or open fracture), reduction method (open reduction and internal fixation [ORIF] or minimally invasive plate osteosynthesis [MIPO]) and fixation evaluations (implant size, plate-bridging ratio, plate span ratio, working length, plate screw density, number of screws and cortices engaged per plate and per main fragment, ratio between screw and bone diameter at the narrowest aspect of the bone, and presence of ancillary fixation). RESULTS: Seventy-five fractures from 63 cats (64 fractures) and 10 dogs (11 fractures) met the inclusion criteria. Eight humeral, 13 radio-ulnar, 26 femoral, and 28 tibio-fibular fractures were treated. Primary repair of the fracture was performed using 2.0 mm and 2.4 mm LCP in 22 and 53 fractures, respectively. Overall and implant-related complications were encountered in 13 and seven of 75 fractures, respectively. Fixation failure was not significantly associated with any aforementioned factor considered in this study, and in particular, there was no significant difference in the occurrence of fixation failure between fractures stabilized with two, or more than two, bicortical locking screws per main fragment. CLINICAL SIGNIFICANCE: 2.0 mm and 2.4 mm LCP were used to manage appendicular fractures in cats and small dogs. The overall complication and fixation failure rate were comparable to those reported in previous studies in which various locking plate systems were used.

Comparison of Survival and Osteogenic Ability of Human Mesenchymal Stem Cells in Orthotopic and Ectopic Sites in Mice.

Tissue constructs containing mesenchymal stem cells (MSCs) are appealing strategies for repairing large segmental bone defects, but they do not allow consistent bone healing and early cell death was identified as a cause of failure. However, little is known about cell survival in the clinical microenvironment encountered during bone healing process. Osteoconductive coral scaffold with or without luciferase-labeled human MSCs were implanted either in a critical segmental femoral bone defect stabilized by plate or subcutaneously in 44 mice. Cell survival was evaluated by serial bioluminescence imaging (BLI) and osteogenic capabilities by histology and microcomputed tomography. Comparisons between groups were performed with two-way analysis of variance test. Twenty mice were sacrificed 2 weeks after surgery for short-term evaluation and 24 mice at 10 weeks for long-term evaluation. BLI provided evidence of fast and continuous cell death: 85% decrease of the BLI signal over the first 2 weeks in both locations; in fact, less than 2% of the initial cell number was present in all constructs analyzed 4 weeks postimplantation and less than 1% of the initial cell number by 8 weeks postimplantation. By 2 weeks postimplantation, the amount of newly formed bone was self-limited and was similar to ectopic and orthotopic groups. By 10 weeks postimplantation, bone formation was significantly enhanced in the presence of MSCs in orthotopic site and the amount of newly formed bone in cell-containing constructs implanted in orthotopic locations was significantly higher than that observed in the ectopic group. Our results indicated that hMSCs promote bone formation despite early and massive cell death when loaded on coral scaffolds. Interestingly, bone formation was higher in orthotopic than ectopic site despite the same survival pattern. Ectopic implantation of cell-containing constructs is suitable to evaluate cell survival, but assessment of bone formation ability requires orthotopic implantation.

Comparative study of the osteogenic ability of four different ceramic constructs in an ectopic large animal model.

Tissue-engineered constructs combining bone marrow mesenchymal stem cells with biodegradable osteoconductive scaffolds are very promising for repairing large segmental bone defects. Synchronizing and controlling the balance between scaffold-material resorption and new bone tissue formation are crucial aspects for the success of bone tissue engineering. The purpose of the present study was to determine, and compare, the osteogenic potential of ceramic scaffolds with different resorbability. Four clinically relevant granular biomaterial scaffolds (specifically, Porites coral, Acropora coral, beta-tricalcium phosphate and banked bone) with or without autologous bone marrow stromal cells were implanted in the ectopic, subcutaneous-pouch sheep model. Scaffold material resorption and new bone formation were assessed eight weeks after implantation. New bone formation was only detected when the biomaterial constructs tested contained MSCs. New bone formation was higher in the Porites coral and Acropora coral than in either the beta-tricalcium phosphate or the banked bone constructs; furthermore, there was a direct correlation between scaffold resorption and bone formation. The results of the present study provide evidence that, among the biomaterials tested, coral scaffolds containing MSCs promoted the best new bone formation in the present study.

A technique for creating critical-size defects in the metatarsus of sheep for use in investigation of healing of long-bone defects.

OBJECTIVE: To develop a technique for use in investigation of healing of long-bone defects by creation of a critical-size defect in the left metarsal III and IV bone (metatarsus) of sheep. ANIMALS: 18 healthy adult sheep. PROCEDURE: Sheep were allocated to 4 groups (3, 3, 5, and 7 sheep in groups 1 to 4, respectively). An ostectomy with various segmental length-to-diaphyseal diameter ratios (0.5, 1.0, 2.0, and 2.0 for groups 1 to 4, respectively) was performed on the left metatarsus of each sheep. The defect was left empty in sheep of groups 1, 2, and 3, whereas the defect was filled with a massive corticocancellous bone autograft in sheep of group 4. RESULTS: All sheep tolerated the surgical procedure well and were able to use the affected limb the day after surgery. Radiographic and histologic examinations conducted 16 weeks after surgery revealed nonunion in all sheep of groups 1, 2, and 3, whereas consistent bone healing with abundant bone formation was observed in all sheep of group 4. CONCLUSIONS AND CLINICAL RELEVANCE: Analysis of these findings suggests that the sheep metatarsal model is a critical-size defect model with low morbidity. It should allow the assessment of new technologies for bone regeneration in conditions closely mimicking the clinical setting. IMPACT FOR HUMAN MEDICINE: Use of this technique in sheep should be of benefit for the preclinical study of osteoconductive, osteoinductive, or osteogenic biomaterials for use in humans.