In vitro biomechanical testing of a micro external skeletal fixator

OBJECTIVE To biomechanically test the properties of three different Universal Micro External Fixator (UMEX™) configurations with regard to their use in very small animals (<5kg) and compare the UMEX system to the widely used IMEX External Skeletal Fixation (SK™) system in terms of stiffness, space needed for pin placement and weight. METHODS Three different UMEX configurations (type Ia, type Ib, and type II modified) and one SK configuration type Ia were used to stabilize Delrin plastic rods in a 1 cm fracture gap model. These constructs were tested in axial compression, craniocaudal bending, mediolateral bending, and torsion. Testing was conducted within the elastic range and mean stiffness in each mode was determined from the slope of the linear portion of the load-deformation curve. A Kruskal Wallis one-way analysis of variance on ranks test was utilized to assess differences between constructs (p <0.05). RESULTS The UMEX type II modified configuration was significantly stiffer than the other UMEX configurations and the SK type Ia, except in craniocaudal bending, where the SK type Ia configuration was stiffer than all UMEX constructs. The UMEX type Ia configuration was significantly the weakest of those frames. The UMEX constructs were lighter and smaller than the SK, thus facilitating closer pin placement. CONCLUSIONS Results supported previous reports concerning the superiority of more complex constructs regarding stiffness. The UMEX system appears to be a valid alternative for the treatment of long-bone fractures in very small animals.

Arthrodesis tarsocrural or tarsometatarsal in 2 dogs using circular external skeletal fixator

An external fixation technique, using a circular fixator, to obtain arthrodesis was evaluated in 2 dogs with infected open lesions and soft tissue damage. In both cases, articular cartilage was curetted, and devitalized bone and necrotic soft tissue were removed. No bone graft was used. The wounds were maintained open and the dogs received postoperative antibiotic therapy. The arthrodesis site was compressed progressively as needed. Infection was eradicated and bony union was obtained in both dogs. It was concluded that the use of a circular fixator is an effective method to achieve arthrodesis.

Use of a type IIB external skeletal fixator in experimental tarsocrural arthrodesis in dogs

The aim of the present study was to evaluate the usefulness of type IIb external skeletal fixators with a transarticular pin in experimental tarsocrural arthrodesis. Twelve adult mongrel dogs of both sexes, ranging in age from two to five years and weighing 12 to 25kg, were used. The configuration of the fixator consisted in the application of a transarticular Steinmann pin and of centrally threaded pins to the proximal portion of the tibia and calcaneus and to the distal portion of the metatarsal bones. In addition, Schanz pins were inserted into the medial and lateral side of the tibia and into the medial side of the metatarsal bones. Radiographs were taken 15; 30 and 45 days after surgery. Bone fusion of the treated joints were observed at 30 days in all animals, and the implants were removed after 45 days. Loosening of the centrally threaded pins was observed in all groups, especially for those applied to the calcaneus. The configuration of the external fixator proposed here was found to be satisfactory in terms of bone union for all joints during the same period, irrespective of the weight of the animal.

Use of a type IIB external skeletal fixator in experimental tarsocrural arthrodesis in dogs

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of a novel transcortical pin-sleeve system in a calf model

Le desserrage des tiges est une complication fréquente des plâtres avec tiges transcorticales (TP) chez les grands animaux, nécessitant souvent leur retrait prématuré avant la guérison des fractures. Les charges excessives centrées sur le cortex à l’interface os-tige proximo-externe et disto-interne causent de l'ostéolyse. En utilisant un modèle de veau nouveau-né, ce projet a évalué un nouveau système de tige-manchon et anneau integré dans un plâtre (PS) optimisé pour réduire la contrainte péri-implant et le stress à l'interface os-implant. On a émis l'hypothèse que les PS se traduiraient par une ostéolyse péri-implant moindre par rapport aux TP. Dix veaux en bonne santé, de 3 semaines d'âge, ont été implantés avec les TP ou PS dans le métacarpe droit, à raison de 2 implants par veau. Les veaux ont été observés quotidiennement pour le confort et la boiterie et ont été euthanasiés à 28 jours. Les données recueillies comprenaient les radiographies à la chirurgie et à l'euthanasie et les mesures histomorphométriques de contact os-implant sur des échantillons non-décalcifiés avec les implants in situ. Les données ont été analysées en utilisant le test de Cochran-Mantel-Haenszel, une valeur de P <0,05 a été considérée comme significative. L'épaisseur corticale était plus importante pour les implants distaux que proximaux pour les deux groupes lors de la chirurgie (P = 0,03), mais était similaire entre les groupes (P > 0,3). Les veaux avec TP ont développé une boiterie plus tôt (au jour 21) que les veaux avec PS (P = 0,04). Histologiquement, il y avait plus de contact direct os-implant cortical pour les implants PS distaux que les implants TP (P = 0,04). La jonction métaphyso-diaphysaire osseuse où les implants proximaux étaient situés est impropre aux deux systèmes; chacun a un minimum de contact os-implant et de l'ostéolyse extensive. Le système PS n'ayant pas causé une ostéolyse importante lorsque implantés dans l'os diaphysaire et peut-être une alternative convenable aux TP pour des fractures comminutives des membres distaux.

Ultra-som pulsado de baixa intensidade em fraturas diafisárias: aplicação clínica em cães

Os efeitos da estimulação ultra-sônica sobre a consolidação óssea têm sido demonstrados por trabalhos experimentais e clínicos. Este estudo teve por objetivo investigar a aplicação clínica do ultra-som pulsado de baixa intensidade como tratamento adjuvante de fraturas diafisárias em cães. Foram utilizados 16 cães de raças variadas, com faixa etária entre sete meses e seis anos, peso corpóreo entre 2,5 e 43kg, portadores de fraturas diafisárias fechadas recentes localizadas no rádio e ulna, fêmur ou tíbia e fíbula, estabilizadas por procedimentos de osteossíntese (fixação esquelética externa, pinos intramedulares ou a associação desses métodos). Os cães foram divididos em dois grupos: fraturas estabilizadas tratadas por ultra-som de baixa intensidade (grupo tratado, n=8); fraturas estabilizadas, não tratadas por estimulação ultra-sônica, (grupo controle, n=8). Os animais foram avaliados por exames clínicos e radiográficos nos períodos pré-operatório, pós-operatório imediato e a cada 30 dias posteriores aos procedimentos cirúrgicos. Realizou-se tratamento com ultra-som pulsado (sinal senoidal com freqüência de 1,5MHz, largura de pulso de 200µs e freqüência de repetição de 1kHz) de baixa intensidade (30mW cm-2), aplicado de modo estacionário no foco de fratura. A terapia ultra-sônica foi realizada 20 minutos por dia, durante 21 dias consecutivos, a partir do período compreendido entre o 1° e o 9° dia pós-operatório. O teste t de Student, empregado na análise estatística, mostrou diferença significante (P<0,001 e alfa=0,05) entre as médias dos parâmetros de tempo para consolidação óssea observadas nos animais dos grupos tratado (média de 67,5 dias) e controle (média de 106 dias). Este protocolo de estimulação ultra-sônica promoveu sinais clínicos e radiográficos acelerados da consolidação óssea nas fraturas tratadas. Os resultados deste estudo sugerem que o ultra-som pulsado de baixa intensidade pode ser indicado como terapia adjuvante de fraturas diafisárias recentes em cães.

Expressão dos fatores de crescimento obtidos do plasma rico em plaquetas, no tratamento de fraturas experimentais do radio de cães

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aspectos radiográficos e densitométricos de fraturas experimentais do radio de cães tratadas com plasma rico em plaquetas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Healing and expression of growth factors (TGF-β and PDGF) in canine radial ostectomy gap containing platelet-rich plasma

Objectives: To evaluate bone healing in an experimental radial ostectomy in dogs treated with autologous platelet-rich plasma (PRP), through histological, densitometric, radiographic studies, as well as expression of growth factors in the ostectomy gap. Methods: Twenty-one dogs were randomly divided into either a control or a PRP group. All underwent unilateral ostectomy of the radius to generate a gap of 2.0 mm, that was stabilized with external skeletal fixation. The ostectomy gap was either filled with PRP or left empty as a control. The radiographic and densitometric studies were performed after surgery, then at intervals until 60 days during the post-surgery period. Histological and immunohistochemical evaluations were performed at seven or 60 days post-surgery. Analyses were performed using a statistical analysis system, and the level of significance was set at p <0.05. Results: The median radiographic healing score in the PRP group increased significantly between day 0 and day 60. Furthermore, at 60 days, the median healing score and the proportion of healed ostectomies in the control group (score 1; 1/6 healed) and the PRP group (score 5; 4/5 healed) were significantly different. There were differences between groups in radiographic and densitometric values at days 45 and 60. The histological evaluation showed advanced bone healing at 60 days in the PRP group and signs of delayed union in the control group. Clinical relevance: Platelet-rich plasma can be used as an adjuvant therapy because it may promote better bone healing of a radial ostectomy treated with external skeletal fixation in dogs.

Osteossíntese de tíbia com uso de fixador esquelético externo conectado ao pino intramedular tie-in em cães

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Stabilization of Juxta-Physeal Distal Tibial and Fibular Fractures in a Juvenile Tiger Using a Hybrid Circular-Linear External Fixator

OBJECTIVE: To report stabilization of closed, comminuted distal metaphyseal transverse fractures of the left tibia and fibula in a tiger using a hybrid circular-linear external skeletal fixator. STUDY DESIGN: Clinical report. ANIMAL: Juvenile tiger (15 months, 90 kg). METHODS: From imaging studies, the tiger had comminuted distal metaphyseal transverse fractures of the left tibia and fibula, with mild caudolateral displacement and moderate compression. Multiple fissures extended from the fractures through the distal metaphyses, extending toward, but not involving the distal tibial and fibular physes. A hybrid circular-linear external skeletal fixator was applied by closed reduction, to stabilize the fractures. RESULTS: The fractures healed and the fixator was removed 5 weeks after stabilization. Limb length and alignment were similar to the normal contralateral limb at hospital discharge, 8 weeks after surgery. Two weeks later, the tiger had fractures of the right tibia and fibula and was euthanatized. Necropsy confirmed pathologic fractures ascribed to copper deficiency. CONCLUSION: Closed application of the hybrid construct provided sufficient stability to allow this 90 kg tiger's juxta-articular fractures to heal with minimal complications and without disrupting growth from the adjacent physes.

The cost and time effectiveness of osseointegration compared to the traditional socket prosthesis

Individuals with limb amputation fitted with conventional socket-suspended prostheses often experience socket related discomfort leading to a significant decrease in quality of life.[1-14] Most of these concerns can be overcome with osseointegration, a direct skeletal fixation method where the prosthetic componentry are directly attached to the fixation, resulting in the redundancy of the traditional socket system. There are two stages of osseointegration; Stage one, a titanium implant is inserted into the marrow space of residual limb bone and Stage two, a titanium extension is attached to the fixture. This surgical procedure is currently blooming worldwide, particularly within Queensland. Whilst providing improvements in quality of life, this new method also has potential to minimise the cost required for an amputee to ambulate during daily living. Thus, the aim of this project was to compare the differences in mean cost of services, cost of componentry and labour hours when using osseointegration compared to traditional socket-based prostheses. Data were extracted from Queensland Artificial Limb Services (QALS) database to determine cost of services, type of services and labour hours required to maintain a prosthetic limb. Five trans-femoral amputee male participants (age 46.4±10.1 yrs; height 175.4±16.3 cm; mass 83.8±14.0 kg; time since second stage 22.0± 8.1 mths) met inclusion criteria which was patient had to be more than 12 months post stage two osseointegration procedure. The socket and osseointegration prosthesis variables examined were the mean hours of labour, mean cost of services and mean cost of prosthetic componentry. Statistical analyses were conducted using an ANOVA. The results identified that there were only significant differences in the number of labour hours (p = 0.005) and cost of services (p = 0.021) when comparing the socket and osseointegration prosthetic type. These results identified that the cost of componentry were comparable between the two methods.

Transducer and base compliance alter the in situ 6 dof force measured from muscle during an isometric contraction in a multi-joint limb.

Although musculoskeletal models are commonly used, validating the muscle actions predicted by such models is often difficult. In situ isometric measurements are a possible solution. The base of the skeleton is immobilized and the endpoint of the limb is rigidly attached to a 6-axis force transducer. Individual muscles are stimulated and the resulting forces and moments recorded. Such analyses generally assume idealized conditions. In this study we have developed an analysis taking into account the compliances due to imperfect fixation of the skeleton, imperfect attachment of the force transducer, and extra degrees of freedom (dof) in the joints that sometimes become necessary in fixed end contractions. We use simulations of the rat hindlimb to illustrate the consequences of such compliances. We show that when the limb is overconstrained, i.e., when there are fewer dof within the limb than are restrained by the skeletal fixation, the compliances of the skeletal fixation and of the transducer attachment can significantly affect measured forces and moments. When the limb dofs and restrained dofs are matched, however, the measured forces and moments are independent of these compliances. We also show that this framework can be used to model limb dofs, so that rather than simply omitting dofs in which a limb does not move (e.g., abduction at the knee), the limited motion of the limb in these dofs can be more realistically modeled as a very low compliance. Finally, we discuss the practical implications of these results to experimental measurements of muscle actions.

Two Surgical Approaches to Fracture Malunion Repair

Two birds were presented with malunion fractures. The first was a young toco toucan (Ramphastos toco) with malunion of the tarsometatarsus that was treated by an opening-corrective osteotomy and an acrylic-pin external skeletal fixator (type II) to stabilize the osteotomy. The second bird was m adult southern caracara (Caracara plancus) with radial and ulnar malunion that was treated by closing-wedge osteotomies. Stabilization of the osteotomy sites was accomplished through 1 bone plate fixed cranially on the ulna with 6 cortical screws and an interfragmentary single wire in radius. In both cases, the malunion was corrected, but the manus of the southern caracara was amputated because of carpal joint luxation that induced malposition of the feathers.

Artrodese do carpo em gatos associada à hidroxiapatita

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)