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ABSTRACT The aim of this study was to evaluate the biomechanical role of both a non-locking two-hole small fragment dynamic compression plate with 3.5-mm screws and a 4.5-mm cortical screw with a washer applied to a Schatzker type-I tibial plateau fracture. Sixteen right synthetic tibiae were used to create an anterolateral shear tibial plateau fracture (Schatzker type-I fracture). Eight models were fixed with a small fragment non-locked straight dynamic compression plate with one 3.5-mm bicortical screw (plate-screw construction) and eight models were fixed with a 4.5-mm cortical screw and a washer (screw-washer construction), both inserted at 1.0 mm distal to the apex of the fracture. Specimens were tested up to the onset of yielding at a constant strain rate of 5.0-mm/min. Stiffness ranged from 311.83 N/mm to 199.54 N/mm, with a mean + SD of 260.32 + 33.8 N/mm in the plate-screw construction, and from 290.34 N/mm to 99.16 N/mm, with a mean + SD of 220.46 + 63.12 N/mm in screw-washer construction. There was no significant difference (p=0.172). Use of a two-hole small-fragment non-locked plate with one 3.5-mm cortical screw or a 4.5-mm cortical screw with a washer applied at 1.0 mm distal to the apex of the fracture as buttressing present similar stiffness in terms of preventing axial displacement in synthetic tibiae models tested up to the onset of yielding.
RESUMO O objetivo do estudo foi avaliar o comportamento biomecânico de dois tipos de fixação: placa de compressão dinâmica de pequenos fragmentos, não bloqueada com parafuso de 3,5mm e parafuso cortical de 4,5mm com arruela, ambos posicionados no vértice de fratura do platô tibial do tipo I de Schatzker. Dezesseis tíbias sintéticas foram utilizadas para criar uma fratura por cisalhamento na face ântero-lateral do platô tibial (tipo I de Schatzker). Oito modelos foram fixados com placa de compressão dinâmica de pequenos fragmentos não bloqueada com parafuso de 3,5mm, inserido 1,0mm distal ao vértice da fratura (construção placa-parafuso), e oito modelos foram fixados com parafuso cortical de 4,5mm com arruela, inserido 1,0mm distal ao vértice da fratura (construção parafuso-arruela). Os modelos foram testados em compressão axial até o início da falha mecânica na interface construção-osso, com taxa de deformação constante de 5,0mm/min. A rigidez variou de 311,83 N/mm a 199,54 N/mm, com média + DP de 260,32 + 33,8 N/mm nos modelos da construção placa-parafuso, e de 290,34 N/mm a 99,16 N/mm, com média + DP de 220,46 + 63,12 N/mm nos modelos da construção parafuso-arruela. Não houve diferença estatisticamente significativa (p=0,172). A utilização de placa de compressão dinâmica de pequenos fragmentos não bloqueada com parafuso de 3,5mm ou de parafuso cortical de 4,5mm com arruela, posicionados no vértice da fratura do platô tibial do tipo I de Schatzker, apresenta rigidez similar na prevenção do desvio axial da fratura.
Subject(s)
Humans , Tibial Fractures/surgery , Fracture Fixation, Internal/methods , Bone Plates , Bone Screws , Models, AnatomicABSTRACT
OBJECTIVE@#A3 intertrochanteric fracture is an extremely unstable fracture, which is often treated with intramedullary nail, but the implant failure is common due to the posterior medial fragment cannot be reconstructed. A new medial sustainable nail (MSN-Ⅱ) which can reconstruct the femoral medial support by sustainable screw was introduced in this study. The mechanical effect was verified by biomechanical experiment.@*METHODS@#The loss medial support model of intertrochanteric fracture (A3) was made by artificial Sawbones model, fixed with MSN-Ⅱ and PFNA-Ⅱ, underwent axial loading and axial failure tests. The axial stiffness, yield load, displacement of head-neck fragment and torsional angle of fracture site of these nails were recorded and compared for biomechanical differences. The effect of early reconstruction of medial support with MSN-Ⅱ was determined.@*RESULTS@#The axial stiffness, yield load, the displacement of head and neck fragment when the axial load was 1 800 N and torsional angle of the fracture site after the axial failure test of MSN-Ⅱ were (222.76 ±62.46) N /mm, (4 241.71 ±847.42) N, (11.51 ±0.62) mm, (1.71 ±0.10)° respectively, while the PFNA -Ⅱ was (184.58±40.59) N /mm, (3 058.76±379.63) N, (16.15±1.36) mm, (2.52±0.26)°respectively. The difference between the two groups was statistically significant.@*CONCLUSION@#The axial stiffness of MSN-Ⅱ is better than that of PFNA-Ⅱ. The MSN-Ⅱ can bear more loads when fixed A3.3 intertrochanteric fracture and has greater axial and rotational stability. It is an effective means to reconstruct the medial support of A3 intertrochanteric fracture.
Subject(s)
Humans , Biomechanical Phenomena , Bone Nails , Bone Screws , Femur , Fracture Fixation, Intramedullary , Hip Fractures/surgeryABSTRACT
OBJECTIVE: Many lumbosacral fixation techniques have been described to offer a more screw-bone purchase. The forward anatomical fixation parallel to the endplate is still the most preferred method. Literature revealed little knowledge regarding the mechanical stability of lumbosacral trans-endplate fixation compared to the traditional trans-pedicular screw fixation method. The aim of this study is to assess the pull-out strength of lumbosacral screws penetrating the end plate and comparing it to the conventional trans-pedicular screw insertion method. METHODS: Eight lumbar and eight sacral vertebrae, with average age 69.4 years, Left pedicles of the 5th lumbar vertebrae were used for trans-endplate screw fixation, group 1A, right pedicles were used for anatomical trans-pedicular screw fixation, group 1B. In the sacral vertebrae, the right side S1 pedicles were used for trans-endplate fixation, group 2A, left side pedicles were used for anatomical trans-pedicular screw fixation, group 2B. The biomechanical tests were performed using the axial compression testing machine. All tests were applied using 2 mm/min traction speed. RESULTS: The average pull-out strength values of groups 1A and 1B were 403.78±11.71 N and 306.26±17.55 N, respectively. A statistical significance was detected with p=0.012. The average pull-out strength values of groups 2A and 2B were 388.73±17.03 N and 299.84±17.52 N, respectively. A statistical significance was detected with p=0.012. CONCLUSION: The trans-endplate lumbosacral fixation method is a trustable fixation method with a stronger screw-bone purchase and offer a good alternative for surgeons specially in patients with osteoporosis.
Subject(s)
Humans , Lumbar Vertebrae , Methods , Osteoporosis , Spine , Surgeons , TractionABSTRACT
Objective To compare cable tension band fixation with other 3 fixations in terms of biomechanical stability for tibial avulsion fractures of the anterior cruciate ligament (ACL).Methods Eighty fresh porcine knees were randomized into 4 equal groups (n =20).For each knee,all the soft tissues were removed only to keep the femur-ACL-tibia complex.The knee complexes were used to create fracture models of standard Meyers-Mc Keever type Ⅲ at the ACL attachment region using a swing saw.The fracture fragments in the 4 groups were subjected to fixation respectively with intramedullary lag screws,high-strength suture,tension band wire and cable tension band.All the specimens were subsequently tested on a Material Testing Machine at a load rate of 60 mm/mm.The 4 groups were compared in terms of ultimate failure load,yield load,and fragmental displacement under single-cycle loading and multi-cyclic loadings.Results Cable tension band fixation displayed significantly higher ultimate failure,higher yield load and lower fragmental displacement than all the other 3 fixations (P ＜ 0.05).Conclusion As cable tension band fixation,which is convenient and economical,provides better biomechanical stability than other 3 fixations for tibial avulsion fractures of the ACL,it may allow earlier functional and weight-bearing exercise after operation.
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PURPOSE: To prevent excessive sliding and subsequent fixation failures in unstable intertrochanteric fractures with posteromedial comminution, extramedullary reduction through overlapping of the anteromedial cortices of both proximal and distal fragments as a buttress has been introduced. The purpose of this study was to compare the biomechanical properties between two reduction methods-intramedullary reduction and extramedullary reduction-in treating unstable intertrochanteric fractures with posteromedial comminution (AO/OTA classification 31-A2.2). MATERIALS AND METHODS: Eight pairs of frozen human cadaveric femora were used. The femora of each pair were randomly assigned to one of two groups: the intramedullary reduction group or the extramedullary reduction group. A single axial load-destruction test was conducted after cephalomedullary nailing. Axial stiffness, maximum load to failure, and energy absorbed to failure were compared between the two groups. Moreover, the pattern of mechanical failure was identified. RESULTS: The mean axial stiffness in the extramedullary reduction group was 27.3% higher than that in the intramedullary reduction group (422.7 N/mm vs. 332.0 N/mm, p=0.017). Additionally, compared with the intramedullary reduction group, the mean maximum load to failure and mean energy absorbed to failure in the extramedullary group were 44.9% and 89.6% higher, respectively (2,848.7 N vs. 1,966.5 N, p=0.012 and 27,969.9 N·mm vs. 14,751.0 N·mm, p=0.012, respectively). In the intramedullary reduction group, the mechanical failure patterns were all sliding and varus deformities. In the extramedullary reduction group, sliding and varus deformities after external rotation were noted in 3 specimens, sliding and varus deformities after internal rotation were noted in 3 specimens, and medial slippage was noted in 2 specimens. CONCLUSION: In unstable intertrochanteric fractures with posteromedial comminution, the biomechanical properties of extramedullary reduction are superior to those of intramedullary reduction. Anteromedial cortex could be the proper buttress, despite a comminuted posteromedial cortex. It could help enhance the stability of the bone-nail construct.
Subject(s)
Humans , Cadaver , Classification , Congenital Abnormalities , Hip FracturesABSTRACT
OBJECTIVE: Many lumbosacral fixation techniques have been described to offer a more screw-bone purchase. The forward anatomical fixation parallel to the endplate is still the most preferred method. Literature revealed little knowledge regarding the mechanical stability of lumbosacral trans-endplate fixation compared to the traditional trans-pedicular screw fixation method. The aim of this study is to assess the pull-out strength of lumbosacral screws penetrating the end plate and comparing it to the conventional trans-pedicular screw insertion method.METHODS: Eight lumbar and eight sacral vertebrae, with average age 69.4 years, Left pedicles of the 5th lumbar vertebrae were used for trans-endplate screw fixation, group 1A, right pedicles were used for anatomical trans-pedicular screw fixation, group 1B. In the sacral vertebrae, the right side S1 pedicles were used for trans-endplate fixation, group 2A, left side pedicles were used for anatomical trans-pedicular screw fixation, group 2B. The biomechanical tests were performed using the axial compression testing machine. All tests were applied using 2 mm/min traction speed.RESULTS: The average pull-out strength values of groups 1A and 1B were 403.78±11.71 N and 306.26±17.55 N, respectively. A statistical significance was detected with p=0.012. The average pull-out strength values of groups 2A and 2B were 388.73±17.03 N and 299.84±17.52 N, respectively. A statistical significance was detected with p=0.012.CONCLUSION: The trans-endplate lumbosacral fixation method is a trustable fixation method with a stronger screw-bone purchase and offer a good alternative for surgeons specially in patients with osteoporosis.
Subject(s)
Humans , Lumbar Vertebrae , Methods , Osteoporosis , Spine , Surgeons , TractionABSTRACT
STUDY DESIGN: An experimental biomechanical study. PURPOSE: This study aims to investigate the behavior of a lamina injury in lumbar burst fractures during reduction maneuvers. OVERVIEW OF LITERATURE: Lumbar burst fractures are frequently accompanied by a lamina fracture. Many researchers concluded that any reduction maneuver will close the fractured lamina edges and possibly crush the entrapped neural elements. This conclusion did not rely on solid biomechanical trials and was based primarily on clinical experience. METHODS: Eighteen fresh-frozen lamb spines were randomly divided into three groups. Using the preinjury and the dropped-mass technique, a burst fracture model was developed. A central laminectomy of 5 mm of the L3 lumbar spine was created to mimic a complete type of lamina fracture. To measure the movement of the fractured laminar edges, two holes were drilled on both sides of the upper and lower regions of the lamina to allow for optic marker placement. A single specific spine movement was applied to each group: traction, flexion, and extension. Gap changes were measured by camera extensometers. RESULTS: After traction, the average values of the upper and lower aspects of the lamina interval showed narrowing of 1.65±0.82 mm and 1.97±1.14 mm, respectively. No statistical significance was detected between the two aspects. The upper and lower regions of the lamina gap behaved differently during extension. At 10°, 20°, and 30°, the upper part of the lamina interval was widened by an average of 0.016±0.024, 0.29±0.32, and 1.73±1.45 mm, respectively, whereas the lower part was narrowed by an average of 0.023±0.012, 0.47±0.038, and 1.94±1.46 mm, respectively. CONCLUSIONS: Neural element crushing may take place, particularly at the lower aspect of the fractured lamina gap during extension and throughout the whole lamina gap during traction. The lamina gap widens during flexion. Reduction maneuvers should be attempted after exploring the fractured lamina to prevent further neurological compromise.
Subject(s)
Laminectomy , Spine , TractionABSTRACT
@#<p style="text-align: justify;"><strong>OBJECTIVE:</strong> Hardware prominence is the most common cause of reoperation in patients who have undergone tension band wiring for fractures of the olecranon. The study was conducted to compare the strength of four different constructs of tension band wiring of the olecranon.<br /><strong>METHODS:</strong> A transverse fracture was created in twenty cadaveric ulnas which were equally divided into four groups according to the method of fixation: 1-Single tension band, transcortical k-wire fixation; 2-Single tension band, intramedullary k-wire fixation; 3-Double tension band, transcortical k-wire fixation; 4-Double tension band, intramedullary k-wire fixation. All specimens were mounted on a universal testing machine using a custom-made fixation jig. They were tested under a single cycle load to failure. The maximum failure load was measured for all specimens.<br /><strong>RESULTS:</strong> There was no significant difference in the maximum load to failure among the four treatment groups.<br /><strong>CONCLUSION:</strong> No differences in the maximum load to failure noted in between treatment groups, regardless if single or double tension band wiring was done, and regardless if k-wire fixation was transcortical or medullary. These findings would support the argument that any of the desired fixation methods may be used.</p>
Subject(s)
Humans , Bone Wires , Elbow Joint , Fracture Fixation, Internal , Fractures, Bone , Olecranon Process , ReoperationABSTRACT
PURPOSE: The purpose of this study was to compare the mechanical stability of three types of plate systems for opening wedge high tibial osteotomy. MATERIALS AND METHODS: Forty-eight fresh frozen porcine tibia specimens were assigned to three different fixation device groups: Aescular group (16 specimens) was fixed with Aescular plates; Puddu group (16 specimens) with a Puddu plate, and TomoFix group (16 specimens) with a TomoFix plate. We compared axial displacements under compression loads from 200 to 2,000 N and maximal loads at failure among 8 specimens per group. We also compared displacements under cyclic load after 100 cycles at a compressive load of 2,000 N among 8 specimens per group. RESULTS: In all three groups, displacement under compression load increased with the increase in the axial compressive load; however, no significant intergroup differences were observed in the mean values under tested loading conditions. The mean maximal loads at failure were not significantly different (6,055, 6,798, and 6,973 N in the Aescular, Puddu, and TomoFix groups, respectively; p=0.41). While the TomoFix group showed less extension and strain during the cyclic load test, the mean values showed no significant differences among groups. CONCLUSIONS: All three plate systems were found to provide fixation stability suitable for bearing axial compression and cyclic loads while walking.
Subject(s)
Knee , Osteotomy , Tibia , WalkingABSTRACT
BACKGROUND: To determine relative fixation strengths of a single lateral locking plate, a double construct of a locking plate, and a tibial nail used in treatment of proximal tibial extra-articular fractures. METHODS: Three groups of composite tibial synthetic bones consisting of 5 specimens per group were included: lateral plating (LP) using a locking compression plate-proximal lateral tibia (LCP-PLT), double plating (DP) using a LCP-PLT and a locking compression plate-medial proximal tibia, and intramedullary nailing (IN) using an expert tibial nail. To simulate a comminuted fracture model, a gap osteotomy measuring 1 cm was created 8 cm below the knee joint. For each tibia, a minimal preload of 100 N was applied before loading to failure. A vertical load was applied at 25 mm/min until tibial failure. RESULTS: Under axial loading, fixation strength of DP (14,387.3 N; standard deviation [SD], 1,852.1) was 17.5% greater than that of LP (12,249.3 N; SD, 1,371.6), and 60% less than that of IN (22,879.6 N; SD, 1,578.8; p < 0.001, Kruskal-Wallis test). For ultimate displacement under axial loading, similar results were observed for LP (5.74 mm; SD, 1.01) and DP (4.45 mm; SD, 0.96), with a larger displacement for IN (5.84 mm; SD, 0.99). The median stiffness values were 2,308.7 N/mm (range, 2,147.5 to 2,521.4 N/mm; SD, 165.42) for the LP group, 4,128.2 N/mm (range, 3,028.1 to 4,831.0 N/mm; SD, 832.88) for the DP group, and 5,517.5 N/mm (range, 3,933.1 to 7,078.2 N/mm; SD, 1,296.19) for the IN group. CONCLUSIONS: During biomechanical testing of a simulated comminuted proximal tibial fracture model, the DP proved to be stronger than the LP in terms of ultimate strength. IN proved to be the strongest; however, for minimally invasive osteosynthesis, which may be technically difficult to perform using a nail, the performance of the DP construct may lend credence to the additional use of a medial locking plate.
Subject(s)
Humans , Biomechanical Phenomena , Bone Nails , Bone Plates , Fracture Fixation, Internal/instrumentation , Fractures, Comminuted/physiopathology , Models, Anatomic , Tibial Fractures/physiopathologyABSTRACT
BACKGROUND: The purpose of this study was to determine the tibial fixation strength provided by different intraosseous soft tissue graft lengths within the tibial tunnel. METHODS: Porcine tibial bones and digital flexor tendons were used for testing. Bone mineral densities of proximal tibial medial condyles were measured, and two-strand tendon bundles of 8 mm diameter were used. An intraosseous graft length of 2 cm was used in group 1 (n = 10), and a graft length of 4 cm was used in group 2 (n = 10). Tunnels were 4 cm in length and 8 mm in diameter. Tibial fixation was performed using a suture tied around a screw post with a washer and an additionally inserted 7 x 20 mm bioabsorbable screw. After applying preconditioning loading of 10 cycles, 1,000 cycles between 70-220 N were applied at a frequency of 1 Hz. Graft slippage and total graft movement were recorded. Ultimate tensile strength was measured by pull-out testing at an Instron crosshead speed of 1,000 mm/min. RESULTS: No significant intergroup difference was found for total graft movement after cyclic loading (slippage in group 1, 1.2 mm and group 2, 1.2 mm, respectively, p = 0.917; and total graft movement in group 1, 3.3 mm and group 2, 2.7 mm, respectively, p = 0.199). However, mean ultimate tensile strength in group 2 was significantly higher than that in group 1 (group 1, 649.9 N; group 2, 938 N; p = 0.008). CONCLUSIONS: In a porcine model, ultimate tensile strength was greater for a 4 cm long intraosseous flexor tendon in the tibial tunnel. However, no intergroup difference in graft slippage or total graft movement was observed. The results show that a 2 cm intraosseous graft length in the tibial tunnel is safe and has sufficient strength (> 450 N) for adequate rehabilitation after anterior cruciate ligament reconstruction.
Subject(s)
Animals , Anterior Cruciate Ligament/injuries , Anterior Cruciate Ligament Reconstruction , Biomechanical Phenomena , Bone Density , Models, Animal , Swine , Tendons/transplantation , Tensile Strength , Tibia/surgeryABSTRACT
OBJECTIVE: The purpose of this study was to compare different positions of plates in lateral malleolar Danis-Weber B fractures on synthetic bone: a lateral plate and a posterior antiglide plate. METHODS : Short oblique fractures of distal fibula at the level of the syndesmosys were simulated with a fibular osteotomy in sixteen synthetic fibula bones (Synbone®). Eight fractures were fixed with lateral plating associated with an independent lag screw, and the other eight were fixed with posterior antiglide plating with a lag screw through the plate. A strain gage was installed at the center of each plate at the osteotomy site. Supination and external rotation forces were applied to each of the two groups at the bend. RESULTS : The lateral position plate group suffered more deformity in response to supination forces compared to the group with the posterior antiglide plate, but this result was not statistically significant. In the tests with external rotation forces, the posterior antiglide plating group had significantly higher resistance (p < 0.05). CONCLUSION : When subjected to external rotation forces, osteosynthesis with posterior antiglide plate models simulating type B fractures of the lateral malleolus of the ankle is more resistant than that of the neutralization plate. .
OBJETIVO: Comparar a resistência mecânica da fixação do maléolo lateral do tornozelo com placa em posição lateral ou posterior com o maléolo em modelos de fíbula sintética, com simulação de fraturas tipo B de Danis-Weber. MÉTODO: A simulação da fratura em 16 fíbulas sintéticas (Synbone®) foi feita por corte oblíquo com serra oscilatória de 1 mm. Em oito modelos, a falha foi fixada por placa de neutralização (posição lateral); as demais por placa anticisalhante (posição posterior). Em seguida instalamos um extensômetro no centro de cada placa, visando a mensurar a deformação determinada pelas forças em supinação produzidas durante experimento na bancada nos dois grupos. Outro ensaio foi produzido com força de rotação externa sobre o implante. RESULTADOS : O grupo com osteossíntese de neutralização sofreu deformação maior aos esforços em supinação quando comparado com o grupo com placa anticisalhante, porém sem significância estatística. Nos ensaios com força em rotação externa houve significância estatística em favor da eficiência das placas posteriores (p < 0,05). CONCLUSÃO : A osteossíntese com placa anticisalhante em modelos que simulam fraturas tipo B do maléolo lateral do tornozelo é mais resistente do que a placa de neutralização quando submetidas às forças em rotação externa. .
Subject(s)
Ankle Injuries , Bone Plates , Clinical Trial , Fibula , Fracture Fixation, Internal , Tibial Fractures , Biomechanical PhenomenaABSTRACT
[Objective]To describe the clinical applycation of domelike decompression of the lumbar vertebral canal and evaluate the outcomes.To evaluate the effects on lumbar stability of domelike decompression through biomechanical canal study.[Method]Domelike decompress of the lumber vertebral canal were performed in 197 patients,with an average age of 52.7 and an average history of 6 years and 8 months,The surgicall outcomes were evaluated with modify Japanese Orthopedic Association Low Back Pain Score(M-JOA).Biomechanical study were performed on lumbar specimens from thirty fresh porcine model which were divided into three groups,Group A(n=10)was biomechanically tested after simulated laminectomy decompression,Group B(n=10)was biomechanically tested after simulated domelike decompression,Group C(n=10)was biomechanicaliy tested on intact,All were tested in flexion extension,torsion,and lateral bending and axial rotation moments as well as axial compressive loads.Load deflection curves were obtained each time,and stiffness values were calculated from the curves,Differences were checked for significance(P
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Peritrochanteric fractures are common in the elderly, and the mortaliy and morbidity rates after conservative treatment of the fractures are usually high. In these fractures the internal fixation now allows the patient more rapid functional gain. It has been known that for stabilization of fracture the sliding hip screw is superior to other fixation devices. To investigate the biomechanical difference between two different materials of dynamic hip screw, eight intertrochateric and eight subtrochanteric femur fractures were artificially induced in human cadavers. Two femurs were used as the control. In eight cadaver intertrochanteric fractures (Group I), four of them were treated with stainless steel compression hip screw and four were treated with titanium compression hip screw. Eight cadaver subtrochanteric fractures (Group II) were divided by two groups as equal number. One group was treated with stainless steel compression hip screw and the other was treated with titanium compression hip screw with plate. Each femur was secured in a fixation device of the Instron and loaded in a vertical compression. Collapse or fixation failure during vertical compression were observed and recorded continuously in slow speed with deformation rate of 3mm/min. Biomechanical analysis of maximal loading force in the control and experimental two groups were performed. The results were as follows; 1. The mean maximal loading force was 625 kp in control group. 2. The mean maximal loading force in each 4 intertrochanteric fractures fixed with stainless steel DHS (dynamic hip screw) and plate was 92.59 kp, and with titanium DHS and plate was 71.57 kp. There was no statistical significance between stainless steel DHS and plate fixation and titanium DHS and plate fixation. (p>0.05) 3. The mean maximal loading force in each 4 subtrochanteric fractures fixed with stainless DHS and plate was 140.12 kp, and with titanium DHS with plate was 169.4 kp. There was no statistical significance between stainless steel DHS and plate fixation and titanium DHS and plate fixation. (p>0.05) 4. The breakage of metal implant was not occurred at the maximal loading force 600 kp in both group. There was no difference of fixability and stability according to the metal quality, as the results of the experiment of compression loading force to the stainless steel DHS and titanium DHS fixation on intertrochanteric and subtrochanteric fractures in cadaverous femurs.
Subject(s)
Aged , Humans , Cadaver , Femur , Hip Fractures , Hip , Internal Fixators , Stainless Steel , TitaniumABSTRACT
Autograft is frequently used to restore anatomic morphology and functional properties in bone defects. Disadvantages of the autograft are related to donor site morbidity and include the risk of wound infection, increased blood loss and additional postoperative discomfort. Allograft and xenograft, which are currently employed as the most common alternative to autografts, encounter the complications such as fracture, resorption and nonunion secondary to immunologic rejection. These volumetric and immunologic concerns with biologic implants have stimulated interest in the potential for synthetic, bioinert materials as bone graft substitutes. Hydroxyapatite (HA), a calcium phosphate ceramic, is a well known biocompatible artificial bone substitite without induction of systemic toxic and foreign body reactions. Bone conduction usually occurrs by the implanted HA but biodegradation of HA is poor and the bone formation around HA is slow. Carbonate apatite has been known as that the physicochemical properties are similar of the natural bony apatite and demonstrates no toxic reactions with better biodegradation. Carbonate apatite collagen composite was reported to show more bone formation and biodegradation than hydroxyap atite. In this study, the composite (CA-C) consisted of carbonate apatite and type I collagen was implanted in rabbit tibiae to evaluate the possibility as an artificial bone substitute. Forty HA (HA group) and forty CA-C (CA-C group) were applied in 80 dissected rabbit tibiae and fixed by external fixators. For biomechanical study, the rabbits were sacrificed and the specimens were obtained in 2, 4, 6 and 8 weeks after implantation. Tensile load was applied to the prepared tibiae in Instron and biomechanical properties were investigated. The fracture at the callus occurred as transverse or short oblique fracture in the vertical direction to the axis of applied tensile load. In each group, the tensile strength at breaking point increased significantly with time and at 4 weeks more prominent increase in break strength was observed (p<0.05). HA group showed higher mean strength before 6 weeks and at 8 weeks CA-C group higher mean strength but statistical significance could not be found. There was no significant difference in extension length at breaking point between both groups and time intervals. In summary, carbonate apatite collagen composite revealed similar biomechanical properties as hydroxyapatite, suggesting its clinical usefulness as a bone substitute, but it will be necessary to improve biodegradational property, stiffness of carbonate apatite collagen composite.
Subject(s)
Humans , Rabbits , Allografts , Autografts , Axis, Cervical Vertebra , Bone Conduction , Bone Substitutes , Bony Callus , Calcium , Carbon , Ceramics , Collagen Type I , Collagen , Durapatite , External Fixators , Foreign Bodies , Heterografts , Osteogenesis , Tensile Strength , Tibia , Tissue Donors , Transplants , Wound InfectionABSTRACT
With porcine vertebrae, the static and dynamic holding power of the pedicle screws under various conditions were measured to understand the biomechanical nature of the transpedicular screw fixation in spine. The objectives of the present study were; (1) to find the correlation between the insertion depth of the screw and the resulting holding power, (2) to determine the effect of bone cement augmentation on the screw fixation in a loosened hole, and (3) to assess the load-sharing mechanism between the cortical and the cancellous one surrounding the screw in this fixational system. The geomorphological characteristics of each porcine vertebra was measured directly with a micro-caliper. The bone mineral density of the specimens was also measured. Material with screw was holded in the fixed cross head of material testing system(Autograph E-10T). Testing force was applied and graph was obtained in the chart record. The results of the static pull-out tests in this study showed that there was a statistically-significant positive correlation between the screw diameter and the pull-out resistance(p < 0.05). The strength of the fixation did not actually increase as much as the insertion depth of the screw increased in these tests(r=0.457). In low-cycle fatigue tests, the increased number of cycles was required to clinical failure in the deeper-inserted crews. Considering the mechanical failure, a statistically-significant positive correlation between the failure cycle and the insertion depth was observed in both deep and shallow insertion groups(p < 0.05). Nonpressurized PMMA augmentation appeared to restore the ability of the screws to withstand pullout loading of the original value. On the effect of the cortical and cancellous bone, the most important factor was the cortical bone of the entrance near the screw.
Subject(s)
Bone Density , Fatigue , Head , In Vitro Techniques , Pedicle Screws , Polymethyl Methacrylate , SpineABSTRACT
The author analysised the state of playing of human cadaver specimens in orthopedic biomechanical study in china and illustrated ethical problems an countermeasure on this issue.
ABSTRACT
The finite element method was utilized to find the rigidity of the device in changing the parameters, such as geometrical configuration, material property, and loading condition in an external fixation. In the experimental analysis, a universal testing machine(UTM) was used to evaluate the rigidity of EBI, Monofixator and Hoffmann under the different type of lodings, such as axial compression, bending and torsion in changing the parameters. The result was compared with those of the experimental work. The results were as follows: 1) In standard condition, the yielding loads in axial compression were 85Kg in the EBI, 55Kg in the Hoffmann, and 100Kg in the Monofixator, The rigidity figures were 2930N/cm in the EBI, 764N/cm in the Hoffmann, and 2391M/cm in the Monofixator. Z) The experimental method was adapted to figure out the effect of parametric change on the stiffness of 3 different external fixation apparatus(Monofixator,EBI, Hoffmann). A Monofixator with a parametric change of pin diameter from 6mm to 5mm indicated 40% reduction of stiffness in axial compression and 60% reduction of stiffness in torsion. Also, in the case of the change of pin group separation from 20cm to 15cm it showed 64% increase of stiffness in, AP bending. EBI with the increase of the distance between pin and aluminum bar to 8cm showed 32% decrement of stiffness in axial compression and 38% decrement of stiffness in AP bending. The stiffness of the Hoffmann device was remarkable according to the number of the pin used and the distance between the pin and the aluminum bar. 3) Concerning the difference between the experimental analysis and finite element method in a Monofixator, the results of the experimental analysis were 10% to 37% lower than those of the finite element method. The reason is thought to be caused by complete binding. The obtained data shed light on the future guide-lines and future alterations of the design factors in external fixation device. Approprate use of the obtained information is desirable for the optimal,treatment of the fractured long bone.
Subject(s)
Aluminum , External Fixators , MethodsABSTRACT
Objective A biomechanical comparison of three kinds of internal fixation for intercondylar fracture of humerus was, made so as to provide a theoretical basis for clinical practice. Methods 18 fresh humeri were used to reproduce T-type intercondylar fracture, and three different fixation appliances were applied, including cross Kirschner wire with addition of “8” wire, single “Y” type plate, 1/3 tubular plate with reconstruction plate. Biomechanical tests were performed on these specimens. Result Under the same load condition, 1/3 tubular plate with reconstruction plate yielded the best results, while crossing Kirschner wire with “8” wire was the poorest. Conclusion The results showed that 1/3 tubular plate with reconstruction plate was a good internal fixation appliance. It has a proper design and stability, but it is not easy to apply. Therefore, an optimal method should be chosen according to local condition in clinical practice.