V. Viateau

Animal Models for Bone Tissue Engineering Purposes

To assess the efficacy of engineered tissues, it is necessary to have (1) appropriate large animal models that mimic the clinical setting and (2) relevant methods of monitoring the biofuntionality of these tissues. However, developing these tissue constructs is a step-by-step process in which numerous variables such as scaffold design, source of stem cells and mode of growth factor application have to be optimized. After an in vitro optimization phase, the use of small animal models to optimize these various parameters and sort out any teething problems is recommended before launching into large animal models. Depending on the experimental aims, engineered tissues can be transplanted into either ectopic sites (subcutaneously or intramuscularly) or orthotopic sites. In all these experimental studies, non invasive imaging methods (X-ray, magnetic resonance, in vivo fluorescence, ultrasound imaging methods, etc.) as well as detailed quantitative molecular and histological analyses have been used to monitor the in vivo behavior of the engineered constructs. In this chapter we take stock of the present state of the art in this field.

Minimally invasive video-assisted cervical ventral slot in dogs. A cadaveric study and report of 10 clinical cases.

OBJECTIVES To investigate the feasibility of a minimally invasive video-assisted (MIVA) cervical ventral slot (VS) in dogs without the use of fluoroscopy, and to report our initial clinical experiences in dogs. METHODS Two surgical approaches to an intervertebral disk space (IVDS) were performed in eight intact canine cadavers to determine the feasibility of MIVA-VS using the Destandau Endospine™ Devicea (DED) without fluoroscopic guidance. In a subsequent clinical study, 10 client-owned dogs admitted for a Hansen type 1 disk extrusion underwent a MIVA-VS. Recorded data in both studies included: incision lengths, correct targeting of the IVDS, technical problems encountered during the procedure, and potential damage to major anatomical structures. In the 10 clinical cases, duration of the procedure and clinical outcome at five and 12 days, and after a minimum of three months were also recorded. RESULTS Correct exposure of the targeted IVDS was achieved in all cases. There was no major iatrogenic damage. Mean skin incision length was 39 mm and mean surgery time was 52 minutes. The technique provided increased illumination and magnification of the surgical field. Recovery was uneventful in all cases. CLINICAL RELEVANCE The present study provided evidence that MIVA-VS using the DED was feasible and a relatively fast and safe procedure for the treatment of cervical disk herniation. Advantages of the technique seemed to include shorter incisions, less dissection and improved visibility.

Use of preoperative computed tomography for surgical treatment of recurrent draining tracts

OBJECTIVES To evaluate a rational decision-making approach based on preoperative computed tomography for surgical planning in dogs and cats with recurrent draining tracts. METHODS Retrospective evaluation of case records of animals that underwent preoperative computed tomography for surgical treatment of thoracic/abdominal recurrent draining tracts. Cases were classified according to whether a source of inflammation and/or infection, in particular foreign bodies, was identified (group 1), suspected (group 2) or neither identified nor suspected (group 3) at computed tomography. Surgery consisted of removal of the source of inflammation and/or infection (group 1), debridement or abscess drainage (group 2) or en bloc resection of diseased tissues (group 3). Clinical outcome was evaluated at least 12 months after surgery. RESULTS A source of inflammation and/or infection was found in 100% (8 of 8), 41% (7 of 17) and 25% (3 of 12) of cases in groups 1, 2 and 3, respectively. Recurrent draining tracts resolved in 100% (8 of 8), 94% (16 of 17) and 92% (11 of 12) of cases in groups 1, 2 and 3, respectively. CLINICAL SIGNIFICANCE The proposed strategy provided a 95% (35 of 37) cure rate, after a single procedure in 81% (30 of 37) of cases. Recovery of a foreign body at surgery was not a prerequisite for the resolution of the recurrent draining tracts.

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 mm3 versus 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.

Computed tomographic study of the optimal safe implantation corridors in feline thoraco-lumbar vertebrae

OBJECTIVE To define the implantation corridors in feline thoraco-lumbar vertebrae (T10-L7) using computed tomography (CT) for optimal safe placement of the implants (screws/pins) in spinal column stabilization. STUDY DESIGN Computed tomographic study. MATERIALS AND METHODS Computed tomography images of feline spinal column (n = 10) were used to define the optimal safe implantation corridors (OSIC) in the transverse plane. The OSIC were defined as corridors allowing the greatest amount of bone purchase with safe margins for implantation of the bicortical implants. They were characterized by their insertion point, optimal angle (from the midsagital plane), maximum and minimum safe angles (from the same insertion points), length, and width. RESULTS The OSIC are located within the vertebral bodies. Insertion points were situated at the level of the vertebro-costal joint or the base of the transverse process of the vertebral body for thoracic and lumbar vertebrae, respectively. The mean optimal angle of the OSIC was 90.2° with a maximum deviation angle from optimal angle of 10° dorsally and 8.8° ventrally in thoracic vertebrae, and 90.5° with a maximum deviation angle from the optimal angle of 8.4° dorsally and 7.6° ventrally in lumbar vertebrae. CONCLUSION AND CLINICAL RELEVANCE Corridors drilled in the vertebral body perpendicular to the midsagital plane (90°) or with a small angle (≤10°) of deviation from the optimal angle provide an optimal safe placement of bicortical implants. However, perpendicular implant placement may not always be feasible due to surrounding soft tissue structures.

Surgical repair of thoraco-lumbar vertebral fracture-luxations in eight cats using screws and polymethylmethacrylate fixation

OBJECTIVE To report our clinical experience in the surgical treatment of feline thoraco-lumbar vertebral fracture-luxations using optimal safe implantation corridors as previously described in vitro. STUDY DESIGN Retrospective clinical study. MATERIALS AND METHODS Medical records and radiographs of cats with vertebral fracture-luxations stabilized by screws and polymethylmethacrylate (PMMA) using optimal safe implantation corridors between 2009 and 2011 were reviewed. For each patient the data included: signalment, cause of vertebral fracture-luxations, presence of concurrent injuries, pre- and postoperative neurological grade, surgical treatment, imaging findings, and clinical outcome with short-term (2 weeks) and long-term (12 months) follow-up. RESULTS Eight cats with vertebral fracture-luxations involving the lumbar (L)(n = 5), the thoracic (T) spinal segments (n = 2), or the thoraco-lumbar junction (n = 1) were included in the study. Screws and PMMA were used bilaterally in five cats and unilaterally in three cats. No surgical intra-operative complications using the defined corridors were recorded. Implant failure followed by spontaneous recovery was recorded in one case. Two cats died in the postoperative period (≤ 4 days). The short-term and long-term clinical outcome was excellent in four out of eight cats and satisfactory in two out of eight cats. CONCLUSION AND CLINICAL RELEVANCE This pilot study demonstrates the clinical applicability of optimal safe implantation corridors for stabilization of feline thoraco-lumbar vertebral fracture-luxations with screws and PMMA. This technique can be used with limited risks of iatrogenic injuries for stabilization of vertebral fracture-luxation localized between T11-L4.

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.

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.