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.

Preoperative computed tomography, surgical treatment and long-term outcomes of dogs with abscesses on migrating vegetal foreign bodies and oropharyngeal stick injuries: 39 cases (2010-2021)

OBJECTIVES

This study evaluated success rates of surgical treatment of head and neck abscesses and draining tracts for suspected migrating vegetal foreign body and oropharyngeal penetrating injuries, and compared the outcomes according to whether a vegetal foreign body was identified in preoperative computed tomography (CT) examination.

MATERIALS AND METHODS

This retrospective study involved 39 dogs that underwent CT and subsequent surgical exploration of abscesses and/or draining tracts in the head and neck, in a single institution between 2010 and 2021. Recorded data included signalment, history, physical examination, CT and surgical findings. The postoperative follow-up period was at least 8 months. Cases were classified according to whether a foreign body was identified on CT or was only suspected because of the presence of cavities and/or draining tracts on CT.

RESULTS

A vegetal foreign body was identified on CT in 11 of 39 cases and later confirmed at surgery in 10 cases. In 28 of 39 cases, a vegetal foreign body was not identified on CT, but in seven of these 28 cases it was found at surgery. Resolution of clinical signs was achieved in 11 of 11 cases when a vegetal foreign body was identified on CT and in 26 of 28 cases without a foreign body identified on CT. Two cases of recurrence were observed in animals in which no foreign body was detected.

CLINICAL SIGNIFICANCE

In this population of dogs undergoing surgery after preoperative CT scan, we observed resolution of clinical signs after a single surgical procedure in 95% of the cases. All animals in which a foreign body was identified were cured.

Needle arthroscopy for exploration of the elbow joint: a case series of six dogs with preliminary cadaveric study

CASE HISTORY

Dogs (n = 6) suffering from elbow-associated lameness for a median of 3.5 (min 2, max 12) months duration requiring arthroscopic exploration according to imaging results were prospectively included in this study.

CLINICAL FINDINGS

Dogs that met the inclusion criteria were of various breeds with a median body weight of 18 (min 13.2, max 34.5) kg and median age at presentation of 11 (min 6, max 96) months.

RESULTS

of imaging modalities (radiographs and/or CT) were consistent with developmental elbow disease in all of the dogs.

ARTHROSCOPIC FINDINGS

Feasibility of the needle arthroscopy procedure was first assessed in a preliminary cadaveric study. Disease-free cadaveric forelimbs (n = 12) were collected from adult dogs (n = 6) euthanised for reasons unrelated to the present study. Elbow exploration was performed, beginning with needle arthroscopy (1 mm, 0° angle scope) followed by standard arthroscopy (2.4 mm, 30° angle scope) through a medial approach. The ease of introduction, range of motion and the quality of visualisation were assessed subjectively and presence of iatrogenic introduction lesions and extent of field of vision (assessed by the number of anatomical structures visualised) were scored and statistically compared. Needle arthroscopy allowed inspection of all structures at risk for medial/caudal compartment disease in all joints considering the occasional need for multiple portals. In the clinical setting, elbow exploration was found to be similar to that in cadaver joints in 4/6 dogs. The lower quality of vision provided by needle arthroscopy was a limitation of the technique, and 2/6 clinical cases required conversion to standard arthroscopy for full visualisation of the joint. No introduction lesions were noted with needle arthroscopy in either the cadaveric or clinical studies.

CONCLUSIONS AND CLINICAL RELEVANCE

Needle arthroscopy allowed safe visualisation of all the structures of the medial and caudal compartment in disease-free cadaveric elbows, suggesting that needle arthroscopy is an appropriate technique for diagnosis and assessment of lesions of developmental elbow disease. However, the low quality of vision provided by the 1 mm scope, and the small diameter of the sleeve, which limited fluid inflow, combined with fragility of the device were major drawbacks that prevented consistent full exploration of the joint and detailed lesion assessment in clinical situations. Improvement of the device is thus necessary before use of the technique in clinical practice can be recommended.

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.

Surgical treatment of a distal oesophageal stricture by mucosal radial incision and dilation in a kitten with secondary megaoesophagus

Case summary

A 7-month-old intact female Maine Coon cat was presented with a 2-month history of regurgitations. Contrast radiographic and endoscopic examinations revealed a diffuse megaoesophagus secondary to a severe lower oesophageal stricture. An epiphrenic diverticulum was noted. Endoscopic balloon dilation was unsuccessful. Gastrotomy was thus performed in order to incise the oesophageal wall radially along the stricture site, and then to dilate the stricture. A diameter of 20 mm was reached. With the aim of preventing stricture recurrence, submucosal injections of triamcinolone acetonide were performed. An 18 Fr oesophagogastric feeding tube was placed and a left gastropexy was performed in order to exert some traction on the gastroesophageal junction, with the aim of reducing the oesophageal diverticulum. Twelve months postoperatively, clinical signs had completely resolved and follow-up radiographs revealed marked improvement of the oesophageal dilatation.

Relevance and novel information

Lower oesophageal strictures should be considered when evaluating regurgitations or megaoesophagus in a kitten. Surgical mucosal radial incision is a therapeutic option in cases of lower oesophageal stricture refractory to balloon dilation, and can lead to a marked improvement of clinical signs and of the oesophagus diameter leading to clinical success.

Custom-made macroporous bioceramic implants based on triply-periodic minimal surfaces for bone defects in load-bearing sites

The architectural features of synthetic bone grafts are key parameters for regulating cell functions and tissue formation for the successful repair of bone defects. In this regard, macroporous structures based on triply-periodic minimal surfaces (TPMS) are considered to have untapped potential. In the present study, custom-made implants based on a gyroid structure, with (GPRC) and without (GP) a cortical-like reinforcement, were specifically designed to fit an intended bone defect in rat femurs. Sintered hydroxyapatite implants were produced using a dedicated additive manufacturing technology and their morphological, physico-chemical and mechanical features were characterized. The implants' integrity and ability to support bone ingrowth were assessed after 4, 6 and 8 weeks of implantation in a 3-mm-long, femoral defect in Lewis rats. GP and GPRC implants were manufactured with comparable macro- to nano-architectures. Cortical-like reinforcement significantly improved implant effective stiffness and resistance to fracture after implantation. This cortical-like reinforcement also concentrated new bone formation in the core of the GPRC implants, without affecting newly formed bone quantity or maturity. This study showed, for the first time, that custom-made TPMS-based bioceramic implants could be produced and successfully implanted in load-bearing sites. Adding a cortical-like reinforcement (GPRC implants) was a relevant solution to improve implant mechanical resistance, and changed osteogenic mechanism compared to the GP implants. STATEMENT OF SIGNIFICANCE: Architectural features are known to be key parameters for successful bone repair using synthetic bioceramic bone graft. So far, conventional manufacturing techniques, lacking reproducibility and complete control of the implant macro-architecture, impeded the exploration of complex architectures, such as triply periodic minimal surfaces (TPMS), which are foreseen to have an unrivaled potential for bone repair. Using a new additive manufacturing process, macroporous TPMS-based bioceramics implants were produced in calcium phosphate, characterized and implanted in a femoral defect in rats. The results showed, for the first time, that such macroporous implants can be successfully implanted in anatomical load-bearing sites when a cortical-like outer shell is added. This outer shell also concentrated new bone formation in the implant center, without affecting new bone quantity or maturity.

Efficacy of HYADD®4-G single intra-discal injections in a rabbit model of intervertebral disc degeneration

BACKGROUND

Various biomaterials/technologies have been tested for treatment of intervertebral disc (IVD) degeneration (IDD). Only few non-surgical options exist.

OBJECTIVE

Assessment of efficacy and safety of the hyaluronic acid derivative hydrogel HYADD®4-G in IDD using a well-established rabbit annular puncture model.

METHODS

Rabbits were punctured at two IVDs to induce IDD. Thirty days after, IVDs were injected with HYADD®4-G or saline. IVD hydration, height, appearance and tissue organization were assessed by radiographs, MRI and histopathology. Safety of HYADD®4-G injection was evaluated in non-punctured IVDs.

RESULTS

HYADD®4-G injection restored disc height to over 75% of the pre-punctured disc, saline injections led to 50% of initial disc height. Compared to saline, HYADD®4-G treatment resulted in improved water retention as revealed by MRI quantification. 83.3% of HYADD®4-G injected discs had normal appearance and reached grade I of the Pfirrmann scale. Regarding tissue organization and cellularity, HYADD®4-G treatment resulted in significantly lower IDD scores than saline (p < 0.01). HYADD®4-G injected into healthy IVDs did not induce inflammation or foreign body reactions.

CONCLUSIONS

Intra-discal HYADD®4-G injection is safe and has therapeutic benefits: IDD could be limited through restoration of disc height and hydration and maintenance of normal IVD tissue organization.

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.

Leiomyoma in the nasal cavity of a dog

A 7-year-old, 34-kg, neutered male Labrador retriever was presented with a 1-year history of intermittent sneezing with occasional left-sided epistaxis. CT revealed a mass in the left nasal cavity. Histopathological analysis of rhinoscopy-guided tissue biopsies was consistent with chronic necrotic and ulcerative rhinitis. Surgical debridement by ventral rhinotomy was subsequently performed and histopathological diagnosis was leiomyoma. Complete resolution of the nasal discharge and reduced sneezing frequency were observed after surgery. Fourteen months postoperatively, CT detected no regrowth of the mass.

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.

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.

Effects of a viscosupplementation therapy on rabbit menisci in an anterior cruciate ligament transection model of osteoarthritis

The aim of this study was to evaluate the morphological, microstructural, and mechanical effects of a viscosupplementation therapy on rabbit menisci at an early stage of osteoarthritis (OA). Anterior cruciate ligament transection (ACLT) was performed in twelve male New-Zealand White rabbits on the right knee joint. Six of these twelve rabbits received a mono intra-articular injection of high molecular weight hyaluronic acid (HA) two weeks after ACLT. Six additional healthy rabbits served as controls. Medial menisci were removed from all right knees (n=18) six weeks after ACLT and were graded macroscopically. Indentation-relaxation tests were performed in the anterior and posterior regions of the menisci. Collagen fiber organization and glycosaminoglycan (GAG) content were assessed by biphotonic confocal microscopy and histology, respectively. Viscosupplementation significantly (p=0.002) improved the surface integrity of the medial menisci compared to the operated non-treated group. Moreover, the injection seems to have an effect on the GAG distribution in the anterior region of the menisci. However, the viscoelastic properties of both operated groups were similar and significantly lower than those of the healthy group, which was explained by their modified collagen fiber organization. They displayed disruption of the tie fibers due to structural alterations of the superficial layers from which they emanate, leading to modifications in the deep zone. To conclude, the viscosupplementation therapy prevents macroscopic lesions of the menisci, but it fails to restore their collagen fiber organization and their viscoelastic properties. This finding supports the role of this treatment in improving the lubrication over the knee.

A comparative study of tissue-engineered constructs from Acropora and Porites coral in a large animal bone defect model

Objectives

To compare the therapeutic potential of tissue-engineered constructs (TECs) combining mesenchymal stem cells (MSCs) and coral granules from either Acropora or Porites to repair large bone defects.

Materials and Methods

Bone marrow-derived, autologous MSCs were seeded on Acropora or Porites coral granules in a perfusion bioreactor. Acropora-TECs (n = 7), Porites-TECs (n = 6) and bone autografts (n = 2) were then implanted into 25 mm long metatarsal diaphyseal defects in sheep. Bimonthly radiographic follow-up was completed until killing four months post-operatively. Explants were subsequently processed for microCT and histology to assess bone formation and coral bioresorption. Statistical analyses comprised Mann-Whitney, t-test and Kruskal–Wallis tests. Data were expressed as mean and standard deviation.

Results

A two-fold increaseof newly formed bone volume was observed for Acropora-TECs when compared with Porites-TECs (14 sd 1089 mm³versus 782 sd 507 mm³; p = 0.09). Bone union was consistent with autograft (1960 sd 518 mm³). The kinetics of bioresorption and bioresorption rates at four months were different for Acropora-TECs and Porites-TECs (81% sd 5% versus 94% sd 6%; p = 0.04). In comparing the defects that healed with those that did not, we observed that, when major bioresorption of coral at two months occurs and a scaffold material bioresorption rate superior to 90% at four months is achieved, bone nonunion consistently occurred using coral-based TECs.

Discussion

Bone regeneration in critical-size defects could be obtained with full bioresorption of the scaffold using coral-based TECs in a large animal model. The superior performance of Acropora-TECs brings us closer to a clinical application, probably because of more suitable bioresorption kinetics. However, nonunion still occurred in nearly half of the bone defects.

Cite this article: A. Decambron, M. Manassero, M. Bensidhoum, B. Lecuelle, D. Logeart-Avramoglou, H. Petite, V. Viateau. A comparative study of tissue-engineered constructs from Acropora and Porites coral in a large animal bone defect model. Bone Joint Res 2017;6:208–215. DOI: 10.1302/2046-3758.64.BJR-2016-0236.R1.

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.

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.

Surgical management of multiple metatarsal fractures in a chinchilla (Chinchilla lanigera)

CASE DESCRIPTION A 3-month-old sexually intact female chinchilla (Chinchilla lanigera) was examined for sudden onset of non-weight-bearing lameness of the right hind limb. CLINICAL FINDINGS On physical examination, the right pes was swollen. An open wound on the medial aspect of the metatarsal region exposed the second metatarsal bone, and the pes was displaced laterally. Radiographs of the right pes revealed oblique displaced fractures of the 4 metatarsal bones. TREATMENT AND OUTCOME Surgical treatment was elected, and enrofloxacin was administered prior to surgery. The protruding fragment of the second metatarsal bone was excised, and the third and fourth metatarsal bones were repaired with intramedullary pins and external skeletal fixation. The chinchilla was bearing weight on the affected limb 9 days after surgery with only mild lameness. The implants were removed 35 days after surgery when radiographs showed bony union of the third and fourth metatarsal bones and continued reduction of the fractures of the second and fifth metatarsal bones. Fifty-six days after surgery, the chinchilla was bearing full weight on the limb, and radiographs showed bony union of the third, fourth, and fifth metatarsal bones. CLINICAL RELEVANCE Findings suggested that intramedullary pinning combined with an epoxy resin external fixator may be an effective technique for metatarsal fracture repair in chinchillas. This method allowed physiologic positioning of the limb and functional hind limb use during fracture healing. Prospective studies of fracture healing in exotic small mammals are indicated.

Viscoelastic properties of rabbit osteoarthritic menisci: A correlation with matrix alterations

The aim of this study was to evaluate the effect of early osteoarthritis (OA) on the viscoelastic properties of rabbit menisci and to correlate the mechanical alterations with the microstructural changes. Anterior Cruciate Ligament Transection (ACLT) was performed in six male New-Zealand White rabbits on the right knee joint. Six healthy rabbits served as controls. Menisci were removed six weeks after ACLT and were graded macroscopically. Indentation-relaxation tests were performed in the anterior and posterior regions of the medial menisci. The collagen fibre organization and glycosaminoglycan (GAG) content were assessed by biphotonic confocal microscopy and histology, respectively. OA menisci displayed severe macroscopic lesions compared with healthy menisci (p=0.009). Moreover, the instantaneous and equilibrium moduli, which were 2.9±1.0MPa and 0.60±0.18MPa in the anterior region of healthy menisci, respectively, decreased significantly (p=0.03 and p=0.004, respectively) in OA menisci by 55% and 57%, respectively, indicating a global decrease in meniscal stiffness in this region. The equilibrium modulus alone decreased significantly (p=0.04) in the posterior region, going from 0.60±0.18MPa to 0.26±012MPa. This induced a loss of tissue elasticity. These mechanical changes were associated in the posterior region with a structural disruption of the superficial layers, from which the tie fibres emanate, and with a decrease in the GAG content in the anterior region. Consequently, the circumferential collagen fibres of the deep zone were dissociated and the collagen bundles were less compact. Our results demonstrate the strong meniscal modifications induced by ACLT at an early stage of OA and highlight the relationship between structural and chemical matrix alterations and mechanical properties.

Indwelling double pigtail ureteral stent combined or not with surgery for feline ureterolithiasis: complications and outcome in 15 cases

Ureteral obstruction secondary to ureterolithiasis in cats is a challenging situation. Ureteral stenting has recently been introduced to prevent complications that often occurred after ureterotomy or other invasive surgeries. The purpose of this study is to describe the stenting technique and perioperative difficulties, as well as long-term outcome and complications with ureteral stenting in 12 cats with ureteroliths. Fifteen 2.5 Fr soft double pigtail multi-fenestrated ureteral stents were placed in an anterograde fashion under open surgical approaches and with fluoroscopic guidance in 12 cats. Nine cats received a unilateral stent and three received bilateral stents. Ureterotomy or ureteral resection and end-to-end anastomosis were performed in three and four cases, respectively. In six cats, papillotomy was performed to facilitate dilatator and stent placement. All cats recovered well from the surgical procedure, except one cat, which died during the anaesthesia recovery period. Postoperative complications included dysuria (three cases, diagnosed at 15 days, 1 month and 3 months, respectively), urinary tract infection (one case, 1 month after surgery), stent migration requiring stent replacement (one case, 19 months after surgery) and stent obstruction requiring stent removal (three cases with previously end-to-end anastomosis between 2 and 8 months after surgery). Nine cats (75%) were alive at a mean follow-up of 453 ± 194 (123–720) days. The median survival time was >415 days. Stent placement appeared to be a valuable and safe option for treating ureteral obstruction in cats. However, periodic and long-term monitoring of stents is warranted.