ABSTRACT
Objective To study the stability of plate-assisted intramedullary nailing for fixing proximal third tibiafractures, compare and observe biomechanical characteristics of anterolateral or posteromedial plate-assisted intramedullary nailing after fixation of proximal third tibia fractures. Methods Eight artificial tibia of 4th-generation sawbones were divided into two groups based on location of the assisted plate, namely, anterolateral plate group and posteromedial plate group, with 4 specimens in each group. Each two locking bolts were fixed to theintramedullary nail proximally and distally, and each three bicortical screws were fixed to the plate proximally and distally. The specimens were osteotomized with a 10-mm defect which located 0. 5 cm to the proximal locking bolt of intramedullary nail or 5-6 cm distally to the knee joint line, in order to simulate an AO/ OTA 41-A2 type proximal third tibia fracture after fixation of intramedullary nail. After osteotomy was finished, axial compression test, three point bending test, cyclic loading and overstress test were conducted by mechanical testing machine. The results of axial stiffness and three-point stiffness between two groups were compared and analyzed. Results Axial compression test showed that the average axial stiffness in posteromedial plate group was lower than that in anterolateral plate group, but no significantly statistical differences were found between the two groups. Three point bending test showed that the average bending stiffness in posteromedial plate group was significantly higher than that in anterolateral plate group when stimulating either varus stress (plate located at pressure side of the fracture, t = 3. 679, P<0. 05) or valgus stress (plate located at tension side of the fracture, t = 8. 975, P<0. 05). Conclusions Plate-assisted intramedullary nailing for fixation of proximal third tibia fractures can minimize the angulation malalignment, improve the stability of nailed proximal tibial fragment and allow the early weight bearing. Both anterolateral and posteromedial plate-assisted intramedullary nail can provide satisfactory axial stability for proximal third tibia fractures, while posteromedial plate-assisted intramedullary nail shows better bending stability than anterolateral plate in countering varus or valgus stress deformity. This study provides an essential basis for clinical decision making about plate-assisted intramedullary nailing for fixing proximal third tibia fractures.
ABSTRACT
Objective: To clarify the value of the cortical endo-button as an internal fixator in Latarjet procedure through biomechanical analysis. Methods: Ten pairs of shoulder joints from 6-7 months old male pigs were selected. Each pair was randomly divided into screw group and endo-button group. A 25% glenoid defect model was created, and the porcine infraspinatus tendon and its associated bone were used to simulate conjoint tendon and coracoid process in human body. The bone grafts were fixed with two 3.5 mm screws and double cortical endo-buttons with high-strength sutures in screw group and endo-button group, respectively. The prepared glenoid defect model was fixed on a biomechanical test bench and optical markers were fixed on the glenoid and the bone block, respectively. Then fatigue test was performed to observe whether the graft or internal fixator would failed. During the test, the standard deviations of the relative displacement between the graft and the glenoid of two groups were measured by optical motion measure system for comparison. Finally the maximum failure load comparison was conducted and the maximum failure loads of the two groups were measured and compared. Results: There was no tendon tear, bone fracture, and other graft or internal fixation failure in the two groups during the fatigue test. The standard deviation of the relative displacement of the screw group was (0.007 87±0.001 44) mm, and that of the endo-button group was (0.034 88±0.011 10) mm, showing significant difference between the two groups ( t=7.682, P=0.000). The maximum failure load was (265±39) N in screw group and (275±52) N in endo-button group, showing no significant difference between the two groups ( t=1.386, P=0.199). There were 3 ways of failure: rupture at bone graft's tunnel (6/10 from screw group, 3/10 from endo-button group), tendon tear at the cramp (2/10 from screw group, 2/10 from endo-button group), and tendon tear at the internal fixator interface (2/10 from screw group, 5/10 from endo-button group), showing no significant difference between the two groups ( P=0.395). Conclusion: Although the endo-button fixation fails to achieve the same strong fixation stability as the screw fixation, its fixation stability can achieve the clinical requirements. The two fixation methods can provide similar fixation strength when being used in Latarjet procedure.
ABSTRACT
ABSTRACT: Long bone fractures are commonly in surgery routine and several bone imobilization techniques are currently available. Technological progress has enabled to use low cost materials in surgical procedures. Thus, the aim of this study was to evaluate the applicability of polyamide 12 rods, solid and hollow in swine femurs, comparing them through flexion strength. This study had as second aim to fix the locking errors, commom place in interlocking nails, once polyamide 12 allows perforation in any direction by orthopaedic screw. Six groups were used: G1 - eight whole swine femurs; G2 - eight whole swine femurs with drilled medullary canal; G3 - two solid polyamide 12 rods; G4 - two hollow polyamide 12 rods; G5 - eight osteotomized drilled swine femurs with a solid polyamide 12 rod implanted in the medullary canal and locked by four 316L stainless steel screws; and G6 - similar to G5 but using hollow rods instead of solid ones. No significant differences were observed for the modulus of rupture between solid and hollow rods, demonstrating that both rods had similar performances. These results led to the speculation that the addition of other polymers to the hollow rods could increase their strength and thus the bone-implant system. Furthermore, the comparison between G1, G5 and G6 could be analyzed using the finite element method in future. New polymeric materials may be developed based on the data from this study, strengthening the bone-implant system and making possible screws to be placed in any direction, nullifying the detrimental forces on the fracture site.
RESUMO: Fraturas em ossos longos são comumente encontradas na rotina cirúrgica e várias técnicas de imobilização óssea estão disponíveis. Com o avanço tecnológico, tornou-se viável utilizar materiais de baixo custo nos procedimentos, portanto esse estudo objetivou avaliar a aplicabilidade de hastes de poliamida 12, sólidas e vazadas, implantadas em fêmures suínos, comparando-as segundo as forças de flexão e aos erros de bloqueio, corriqueiros nesse implante, uma vez que a poliamida 12 permite sua perfuração em qualquer direção por meio de parafusos ortopédicos. Seis grupos foram usados: G1 - oito fêmures suínos íntegros; G2 - oito fêmures suínos, fresados intramedularmente; G3 - duas hastes maciças de poliamida 12; G4 - duas hastes vazadas de poliamida 12; G5 - oito fêmures suínos osteotomizados e fresados, com haste de poliamida 12 maciça implantada no canal medular e bloqueada com quatro parafusos de aço inoxidável 316L e G6 - diferente de G5 apenas por utilizar hastes vazadas. Não foram observadas diferenças significativas no módulo de ruptura entre hastes sólidas e vazadas, demonstrando que ambas apresentaram o mesmo desempenho. Estes resultados levaram à especulação de que adicionar outros polímeros às hastes vazadas aumentaria sua força e, portanto, do sistema osso-implante. Além disso, a comparação entre G1, G5 e G6 poderia no futuro ser analisada utilizando o método dos elementos finitos. Novos polímeros podem ser desenvolvidos baseando-se nos dados deste estudo, reforçando o sistema osso-implante e também possibilitando o uso de perfurações para o bloqueio no transoperatório em qualquer direção, anulando as forças deletérias atuantes no sítio de fratura.
ABSTRACT
Objective To observe the changes of bone mass in reloaded rats after tail-suspension,and the effect and mechanism of simvastatin on this process.Methods Twenty-four 5-month old rats were divided into 4 groups of 6 animals in each group: Control (CL) group without tail-suspension,unloaded (UL) group with tail-suspension for 6 weeks,other 12 rats received tail-suspension for 3 weeks,then reloaded for subsequent 3 weeks (UL+RL) or combined with simvastatin treatment (UL+RL+SIM) at a dose of 10 mg/kg/d.All rats were sacrificed 6 weeks later,and the left femur was used for examination of bone mineral density,left tibia was used for bone histomorphometry analysis,the right femur and tibia were harvested for biomechanical test,and expression levels of type I collagen by real-time PCR and Western blot,respectively.Results 1.BMD of the CL group was significantly higher than those of the other three groups (P<0.05),and was markedly lower than those in the UL+RL and UL+RL+SIM groups (P<0.05).2.The bone histomorphometry showed that BV/TV in the CL group was significantly higher than those in the other 3 groups,and the UL+RL and UL+RL+SIM groups showed a significantly higher BV/TV than that of UL group (P<0.05).The Tb.Th was significantly higher in the CL group than in the UL group.The Tb.Sp in the CL group was significantly lower than those in the other 3 groups (P<0.05).The UL+RL and UL+RL+SIM groups showed significantly lower Tb.Sp than that of the UL group (P<0.05).3.Biomechanical test showed that the maximal load and elastic modulus in the CL groups were significantly higher than those of the other three groups (P<0.05).4.Real-time PCR showed that no significant difference in the mRNA expression level of Col I was found between any two groups.5.Western blot showed that the IOD of Col I is significantly lower than that in the CL group.Conslusions Bone loss,destruction of trabecular bone micro-architecture and biomechanical properties and reduction of type 1 collagen are present in tail-suspension treated rats,which are partially restored after reloading,and this recovery process is not enhanced by simvastatin treatment.
ABSTRACT
ABSTRACT: Often fractures of long bones in horses are comminuted and form bone gaps, which represent a major challenge for the fixation of these fractures by loss of contact between the fragments. Bone grafts help in treating this kind of fracture and synthetic materials have been gaining ground because of the limitations of autologous and heterologous grafts. In this study were performed compressive non destructive test in 10 bones with complete cross-bone gap in mid-diaphyseal of the third metacarpal bone of horses. Using a mechanism of "crossing" the 10 bones were used in the three groups (control, castor oil poliuretane and chitosan) according to the filling material. After the test with maximum load of 1000N bone had a gap filled by another material and the test was repeated. Deformations caused on the whole bone, plate and bone tissue near and distant of gap were evaluated, using strain gauges adhered to the surface at these locations. There was a reduction in bone deformation from 14% (control) to 3,5% and 4,8% by filling the gap with Chitosan and castor oil respectively, and a reduction of strain on the plate of 96% and 85% by filling gap with chitosan and castor respectively. An increase in intensity and direction of deformations occurred in bone near to gap after its filling; however, there was no difference in bone deformations occurring far the gap.
RESUMO: Frequentemente, as fraturas de ossos longos nos equinos são cominutivas, formando falhas ósseas, que representam um grande desafio no momento de sua fixação, devido à perda de contato entre os fragmentos. Os substitutos ósseos sintéticos auxiliam no tratamento desse tipo de fratura. Neste estudo, foram realizados ensaios compressivos não destrutivos em 10 ossos com falha óssea transversal completa em diáfise do terceiro metacarpiano de equinos. Utilizando um mecanismo de "crossing", os 10 ossos foram utilizados nos três grupos (controle, mamona e quitosana) de acordo com o material de preenchimento da falha. Para cada peça, realizaram-se ensaios referentes aos três grupos, com carga máxima de 1000N, por não se tratarem de ensaios destrutivos. Foram avaliadas as deformações causadas no osso, na placa e no tecido ósseo próximo e distante da falha, por meio de extensômetros. Observou-se que houve redução da deformação do osso de 14% (controle) para 3,5% e 4,8%, com o preenchimento da falha com quitosana e mamona, respectivamente. Houve redução da deformação na placa de 96% e 85% com o preenchimento da falha com quitosana e mamona, respectivamente. Houve aumento em intensidade e direção das deformações ocorridas no osso próximas à falha após seu preenchimento, contudo não se observaram diferenças nas deformações ocorridas no osso distantes a falha. Dessa forma, conclui-se que o preenchimento das falhas com quitosana e poliuretana de mamona trouxe benefícios quanto à redução das deformações no foco da fratura, alívio das cargas na placa, contudo elevou as cargas no tecido ósseo próximo à falha.
ABSTRACT
Este é o primeiro estudo que compara o comportamento biomecânico de duas diferentes placas de avanço da tuberosidade tibial (ATT). Com o objetivo de minimizar a incidência de falhas de implante, foram realizados ensaios biomecânicos em 10 pares de membros pélvicos de cadáveres de cães. No membro pélvico direito, foi colocada placa de ATT fixa por garfo, e no membro pélvico esquerdo placa fixa por parafusos. Os ensaios foram realizados utilizando-se máquina universal de ensaios mecânicos Kratos(r), modelo KE3000, dotada de célula de carga de 3000N, com velocidade de ensaio de 20mm/min. O parâmetro força e os gráficos gerados foram gravados por meio de sistema de aquisição analógica TRACOMP-W95 (TRCV61285). A média da carga máxima até a falha foi de 128,70kg/F (mínimo 104,55kg/F e máximo 151,80kg/F) e de 141,99kg/F (mínimo 111,60kg/F e máximo 169,65kg/F) no grupo utilizando garfo e parafusos, respectivamente. O desvio-padrão dos grupos garfo e parafuso foi baixo, 12,99 e 17,21, respectivamente. Foi encontrada diferença significativa (P=0,03) entre as médias dos grupos. Com base nos resultados obtidos, conclui-se que existe diferença estatística significativa na resistência promovida entre as placas testadas, quando se observou que a placa fixa por parafusos promove maior resistência.(AU)
This is the first study to compare the biomechanical strength between the two different TTA plates. With the purpose of minimizing the incidence of implant failure, biomechanical tests were performed on 10 pairs of cadaveric hind limbs from dogs. The right hind limb of each dog was used as a model for the TTA plate fixed by fork, and the left pelvic limb was used as a model for the TTA plate fixed by screws. Tests were performed using a universal mechanical testing Kratos (r) machine, model KE 3000, equipped with a load cell of 3000N with a test speed of 20mm/min. The strength parameter and graphs generated were recorded via analog acquisition system TRACOMP-W95 (TRCV61285). The mean load to failure was 128.70kg/F (minimum 104.55kg and maximum 151.80kg/F) and 141.99kg/F (minimum 111.60kg/F and maximum 169.65kg/F) in the fork and screws groups respectively. The standard deviation of the fork and screws groups was low: 12.99 and 17.21 respectively. Significant difference (P= 0.03) between means of the groups was observed. From the results obtained it was concluded that there is a statistically significant difference in the resistance between plates and the plate fixed by screws promotes increased strength.(AU)
Subject(s)
Animals , Dogs , Biomechanical Phenomena , Prosthesis Implantation/veterinary , Tibia/transplantation , Osteotomy/veterinary , StifleABSTRACT
The arthroscopic rotator cuff repair is now considered a mainstream technique with highly satisfactory clinical results. However, concerns remain regarding healing failures for large and massive tears and high revision rate. In recent decades, various repair strategies and construct configurations have been developed for rotator cuff repair with the understanding that many factors contribute to the structural integrity of the repaired construct. The focus of biomechanical test in arthroscopic repair has been on increasing fixation strength and restoration of the footprint contact characteristics to provide early rehabilitation and improve healing. These include repaired rotator cuff tendon-footprint motion, increased tendon-footprint contact area and pressure, and tissue quality of tendon and bone. Recent studies have shown that a transosseous tunnel technique provides improved contact area and pressure between rotator cuff tendon and insertion footprint, and the technique of using double rows of suture anchors to recreate the native footprint attachment has been recently described. The transosseous equivalent suture bridge technique has the highest contact pressure and fixation force. In this review, the biomechanical tests about repair techniques of rotator cuff tear will be reviewed and discussed.
Subject(s)
Rehabilitation , Rotator Cuff , Suture Anchors , Sutures , Tears , TendonsABSTRACT
The arthroscopic rotator cuff repair is now considered a mainstream technique with highly satisfactory clinical results. However, concerns remain regarding healing failures for large and massive tears and high revision rate. In recent decades, various repair strategies and construct configurations have been developed for rotator cuff repair with the understanding that many factors contribute to the structural integrity of the repaired construct. The focus of biomechanical test in arthroscopic repair has been on increasing fixation strength and restoration of the footprint contact characteristics to provide early rehabilitation and improve healing. These include repaired rotator cuff tendon-footprint motion, increased tendon-footprint contact area and pressure, and tissue quality of tendon and bone. Recent studies have shown that a transosseous tunnel technique provides improved contact area and pressure between rotator cuff tendon and insertion footprint, and the technique of using double rows of suture anchors to recreate the native footprint attachment has been recently described. The transosseous equivalent suture bridge technique has the highest contact pressure and fixation force. In this review, the biomechanical tests about repair techniques of rotator cuff tear will be reviewed and discussed.
Subject(s)
Rehabilitation , Rotator Cuff , Suture Anchors , Sutures , Tears , TendonsABSTRACT
This study used a biomechanical test to evaluate the effects of pentoxifylline administration on the wound healing process of an experimental pressure sore induced in rats. Under general anesthesia and sterile conditions, experimental pressure sores generated by no. 25 Halsted mosquito forceps were inflicted on 12 adult male rats. Pentoxifylline was injected intraperitoneally at a dose of 50 mg/kg daily from the day the pressure sore was generated, for a period of 20 days. At the end of 20 days, rats were sacrificed and skin samples extracted. Samples were biomechanically examined by a material testing instrument for maximum stress (N mm2), work up to maximum force (N), and elastic stiffness (N/mm). In the experimental group, maximum stress (2.05+/-0.15) and work up to maximum force (N/mm) (63.75+/-4.97) were significantly higher than the control group (1.3+/-0.27 and 43.3+/-14.96, P=0.002 and P=0.035, respectively). Pentoxifylline administration significantly accelerated the wound healing process in experimental rats with pressure sores, compared to that of the control group.
Subject(s)
Adult , Animals , Humans , Male , Rats , Anesthesia, General , Culicidae , Pentoxifylline , Pressure Ulcer , Skin , Surgical Instruments , Wound HealingABSTRACT
PURPOSE: To assess the biomechanical effects and effectiveness of an interspinous spinal spacer (ISS) on the intradiscal pressure using in vitro biomechanical tests. MATERIALS AND METHODS: Six calf spine specimens (less than 2 weeks of age, L1-L5) were divided to two groups the intact and the surgery groups (n=3 each). For the surgery group, an ISS made from PMMA (Greek pi=12-mm) were inserted into the space between the spinous processes of L3-L4. The intradiscal pressures at the various regions of the annulus (anterior, posterior, and posterolateral locations) and the nucleus pulposus were measured using the four pressure transducers under pure compression (700 N) and extension loads (700 N+7.5 Nm). RESULTS: An increase in pressure was observed from neutral to extension at the posterior and posterolateral annulus. After inserting the ISS, the changes in pressure at the adjacent disc levels (L2-L3, L4-L5) were negligible regardless of the loading conditions (p>0.05). However, at the implanted level (L3-L4) statistically significant changes in the pressure were found under extension loading at the nucleus pulposus, posterior and posterolateral regions of the annulus with a pressure drop from 1.48 MPa, 1.42 MPa, 1.71 MPa to 1.11 MPa, 0.961 MPa, 1.08 MPa, at the respective locations (p<0.05). The relative percentage decrease were 25%, 31.7%, and 36.8%. CONCLUSION: On the implanted level, these results showed that the insertion of the ISS with PMMA can effectively reduce the intradiscal pressures by at least 25% quite uniformly over the intravertebral disc during extension. More effective reduction was observed at the posterolateral location. The pressure changes at the adjacent levels were negligible in contrast to the abnormal pressure changes that are frequently reported after conventional rigid fusion. This suggests that the likelihood of adjacent level degeneration after surgery can be minimized using the ISS insertion.
Subject(s)
Polymethyl Methacrylate , Spinal Stenosis , Spine , Transducers, PressureABSTRACT
The purpose of this study was to investigate the clinical, biomechanical, and histologic changes in new distraction osteogenesis (DO) technique combined with a compression stimulation in accordance to different compression-distraction force ratio. 23 adult male rabbits underwent open-osteotomy at the mandibular body area and a external distraction device was applied. In the control group of 8 rabbits, only a 8 mm of distraction was performed by conventional DO technique. In an experimental group of 15 rabbits, a distraction followed by a compression force was performed according to the ratio of compression-distraction suggested by authors. The rate of experimental group I was set up as a 2 mm compression versus 10 mm distraction and the rate of experimental group II was set up as a 3 mm compression versus 11 mm distraction. All the rabbits were sacrificed for a gross finding, biomechanical, histomorphometric and histologic findings at the time of 55 days from the operation day. The results were as follows: 1. On the gross findings, because all rabbits had a sufficient healing time, every distracted new bone had good bone quality and we could not find any difference among all three groups. 2. In the histologic findings, rapid bone maturation (wide lamellar bone formation in the cancellous and cortical bone areas) was observed in two experimental groups compared to the control group. 3. On the bone density tests, the experimental group II showed higher bone density than the other experimental group and control group (control group - 0,2906 g/cm2, experimental group I - 0.2961 g/cm2, experimental group II - 0.3328 g/cm2). 4. On the biomechanical tests, the experimental group II had significantly higher bone microhardness than the other experimental group and control group (control group - 252.7 MPa, experimental group I - 263.5 MPa, experimental group II - 426.0 MPa). 5. On the microhardness tests, when we compared the hardness ratio of distracted bone versus normal bone, we could find experimental group II had significantly higher hardness ratio than the other experimental group and control group (control group - 0.47, experimental group I - 0.575, experimental group II - 0.80). From this study, we could deduce that the modified distraction osteogenesis method with a compression stimulation might improve the quality of bone regeneration and shorten the consolidation period in comparison with conventional distraction osteogenesis techniques.
Subject(s)
Adult , Humans , Male , Rabbits , Bone Density , Bone Regeneration , Hardness , Osteogenesis , Osteogenesis, DistractionABSTRACT
PURPOSE: To compare the mechanical effectiveness between performing conventional partial patellectomy and the separate vertical wiring technique for a comminuted fracture of the inferior pole of the patella. MATERIALS AND METHODS: Twenty patellae from cadavers (ten pairs) were used to model acute comminuted fractures of the inferior pole of the patella. Comminuted fractures of the inferior pole of the patellae were made by an oscillating saw. Then they were fixed with separating vertical wiring on one side and the other side received a partial patellectomy by the pull-out suture technique. We measured the maximal lengths between the superior and inferior poles of the normal patella and after fixation. A biomechanical test was then performed to compare the strength of fixation in the two group. RESULTS: The lengths of patella in the separate vertical wiring group (mean: 5.63 cm) were longer than those in the partial patellectomy group (5.24 cm). The maximal strengths of fixation in the separate vertical wiring (mean: 250.1 Newtons) were higher than in the partial patellectomy (mean: 69.7 Newtons). CONCLUSION: A separate vertical wiring is an effective method for fixation of the comminuted fracture of the inferior pole of the patella.