Comparison of statics characteristics between anterior transpedicular screws system and vertebral body screws system in lower cervical spine / 中国骨伤

<p><b>OBJECTIVE</b>To compare statics characteristics between anterior transpedicular screws (ATPS) system and vertebral body screws (VBS) system in lower cervical spine.</p><p><b>METHODS</b>Sixteen fresh cervical specimens were collected and dissected into 32 different units (functional spinal unit, FSU), 8 units in C3,4, C4,5, C5,6 and C6,7 each. The subjects were randomly divided into group A and B. The anterior transpedicular screw-plate system and anterior vertebral body screw-plate system were implanted separately in group A and B. Then, the maximum axial pull out strength was tested and compared between two fixation system.</p><p><b>RESULTS</b>Maximum pull out strength was (604.68 +/- 48.76) N in group A and (488.24 +/- 32.42) N in group B, and there was significant difference between two groups (t = 2.147, P < 0.05). There was no statistically significant difference in all FSU between anterior transpedicular screws system and vertebral body screws system (F(A) = 2.27, F(B) = 2.05, P > 0.05).</p><p><b>CONCLUSION</b>The pull out strength of anterior transpedicular screws system is better than vertebral body screws system, and the anterior transpedicular screws has the biomechanical feasibility in clinic.</p>

Biomechanical study on the novel minimally invasive anterior anatomic locking plate for mid-distal humeral shaft fractures / 医用生物力学

Objective To test the mechanical properties of a self-developed novel anterior mid-distal humerus anatomic locking plate (hereinafter referred to as the new plate) and to improve its design to provide theoretical support for its clinical application. Methods Twenty intact humerus from embalmed human cadavers were obtained and used for the biomechanical test on mid-distal humeral shaft fracture models by using the new plate (group A) and 4.5 mm LC DCP（limited contact dynamic compression plate）(group B), respectively. Both groups were compared under axial compression, medial-lateral bending, medial-lateral three-point bending and external rotation torque. Results The stiffness, strength and stress shielding of the new plate for mid-distal humeral shaft fractures under four different loads were superior to those of 4.5 mm LC-DCP, and the differences were statistically significant(P<0.05). Conclusions The new plate can satisfy the requirements of physical training at early stage for fixed mid-distal humeral shaft fractures, which gives great clinical values.

Biomechanical test and clinical application of EZ extraction screws device / 医用生物力学

Objective To evaluate the effect of EZ extraction screws device on screwing out the reduced screws，broken screws, skidded screws in biomechanical test and clinical application. Method 4 femurs, tibias, radius, ulnas of 4 fresh skeleton specimen were divided into two big groups randomly as Group A and Group B1, B2 and B3: In Group A the screws were taken out by screwdriver; In Group B, the screws were clamped in medulla cavity filled with the bone cement,;B1 was the group of measuring skidded screws with the biggest torsion; B2 was the group of measuring skidded screws with the biggest torsion by one handle; B3 was by two handles. Four mechanics test models were made, and the clamping screws were divided into two types of 4.5 mm and 3.5 mm each for 60. The experiment specimen were tested on the universal testing machines with exerting 2 kN axial loading, and surveyed the greatest torque, the torsion angle and the power loss as well as the efficiency when drawing out. The empirical datum after statistics processing were compared among the groups. And EZ was also used for 12 example patients in the preliminary clinical practice. ResultsGroup A showed the biggest torque as 1.42～1.96 N·m for drawing out; Group B1 as 2.87～3.27 N·m; Group B2 as 3.06～4.83 N·m; Group B3 as 4.12～8.36 N·m. The significant difference （P<0.05）was found in each group. The average value of torsion angle in each corresponding group is 1.59°,0.77°,0.28° and 0.16°, respectively with the obvious difference （P<0.05）; The average value of power loss in each group is 12, 21, 32 and 45J respectively; and the power (mechanical efficiency) in each corresponding group is 0.20, 0.35, 0.53 and 0.75 T/s, respectively, which also showed the obvious difference （P<0.05）. EZ used in 12 cases were successfully screwed out with all the broken screws and maintained the integrity of the bone without any postoperative complications. Conclusions EZ extraction screw device has sufficient torsional strength and stiffness with enough clamping force, and could pull out stably and reliably, which is an ideal tool for the stub screws, crooked screws and slipped screws in skeleton.

Biomechanical comparison of three methods of internal fixation for distal femoral fractures / 中国骨伤

<p><b>OBJECTIVE</b>To compare the biomechanics of three internal fixations for distal femoral fractures,and to choose suitable clinical internal fixation according to experimental date.</p><p><b>METHODS</b>The fracture models of femoral condydle were made on 12 fresh cadaver femurs (C1 type of AO classification). The fractures were fixed by supracondylar intramedullary interlocking nails (A), L-shaped condyle plates (B) and compressed plates (C) respectively. The straining, displacement, rigidity and intensity of femoral supracondyla of the three internal fixations of distal femoral fractures were observed and analyzed by biomechanics. These three different internal fixation methods were compared by experimental stress analysis. These results were further confirmed by theoretical analysis using finite element method (FFM).</p><p><b>RESULTS</b>Under the same load condition, supracondylar intramedullary interlocking nail fixation was the best on the intensity and rigidity,while for compressed plate and L-shaped condyle plate, the femoral condyle intensity and rigidity were worse (P < 0.05). There were distinct differences in stress and displacement among three methods (P < 0.01).</p><p><b>CONCLUSION</b>Supracondylar intermedullary interlocking nail is the best method among the three internal fixation methods. It has advantage such as screw location, solid fixation and less complication. It is a good internal fixation method for distal femoral fracture.</p>

Influence of pedicle screws with different insertion depth on neighboring uninfused segments in a goat lumbar spinal fusion model / 中国骨伤

<p><b>OBJECTIVE</b>To observe the influences of pedicle screws in various insertion depth on the adjacent segment disc degeneration following lumbar spinal fusion. To explore the relationship between the internal fixation rigidity and incidence of adjacent segment disease.</p><p><b>METHODS</b>Sixteen hybrid male Bohr goats of 10 months old, weighting between 25 and 30 kg, were randomly devided into a control group (N group), and 3 experimental groups, each group had 4 goats. The L4 vertebra of each goat in the experimental groups was fractured, L3-L5 segments were internal fixed with pedicle screws followed by intervertebral joint fusion by a posterior approach. Three experimental groups were devided according to the length of pedicle screws applied, vertebras of goats in L group were internal fixed by the screws at the length of 25 mm, for M group and S group, 20 mm and 15 mm, accordingly. The goats in the control group were treated without any operation. Biomechanical changes and MRI index of upper unfused segment (L2) were measured 24 weeks after operation, and histological changes were observed as well.</p><p><b>RESULTS</b>The pressure and straining of L2 vertebral body and intervertebral disc of L group increased more than N group (P < 0.05), and degenerated cell counting in nucleus pulposus increased as well (P < 0.05). However, MRI index remain unchanged (P > 0.05).</p><p><b>CONCLUSIONS</b>Rigid internal fixation increases the pressure and straining of vertebral body and intervertebral disc of upper adjacent segment, accelerating the degeneration process following lumbar spinal fusion in goats.</p>

Biomechanical study on transarticular screw and plate fixation syetem in the lower cervical spine / 中国骨伤

<p><b>OBJECTIVE</b>To compare the cervical stabilities of transarticular screw fixation alone, and transarticular screw and plate fixation system.</p><p><b>METHODS</b>Twelve specimens of cervical vertebra containing C2-T1 were obtained from human cadaver. The three-column instability model was made at C4.5 and C5.6 levels. The specimens were stabilized with transarticular screw fixation alone, and transarticular screw and plate fixation system respectively. The ranges of motion of segments including intact group, transarticular screw fixation alone group and transarticular screw and plate fixation system group were measured under the torque of 2.0 N x m in flexion, extension, lateral bending, and torsion respectively under nonrestrictive and nondestructive condition.</p><p><b>RESULTS</b>The rang of motion (ROM) and neutral zone (NZ) of both transarticular screw fixation alone and transarticular screw and plate fixation system group were significantly smaller than those of intact group in all directions (P < 0.05). The transarticular screw and plate fixation system group allowed a very smaller ROM and NZ than transarticular screw fixation alone during extension, lateral bending and axial rotation except flexion (P < 0.05).</p><p><b>CONCLUSION</b>Cervical transarticular screw and plate fixation system provides better stability than transarticular screw fixation alone. If the transarticular fixation technique is preferred, transarticular screw and plate fixation system will be beneficial.</p>

Biomechanical research in treating unstable Pilon fracture with anatomic plate of distal tibia / 中国骨伤

<p><b>OBJECTIVE</b>To investigate the mechanical characteristics of new anatomic plate of distal tibia from view of biomechanics.</p><p><b>METHODS</b>Twelve fresh adult moist ankle specimens were randomly divided into four block groups (every group had 3 specimens), 3 tibial specimens as a normal control (normal group N), 9 specimens were resulted in unstable distal tibial Pilon fracture. Using steel plate fixation with a new anatomic distal tibial plate (group A), reconstruction plate (group B), clover plate (group C). Group B and group C as control group to test the remote axial compressive strength, remote axial stiffness, reversing biomechanical properties, contacted characteristics of the tibial astragaloid articular surface.</p><p><b>RESULTS</b>The remote axial compressive strength, remote axial stiffness, reversing biomechanical properties, contacted characteristics of tibial astragaloid articular surface the in distal tibial Pilon fracture instability of group A were near normal group N (P>0.05). Group A was best than group B and C (P<0.05).</p><p><b>CONCLUSION</b>The new anatomic plate of distal tibia was relatively strong, which can reach effective and stable fixation for unstable distal tibial Pilon fracture.</p>

Biomechanical study of new type two-head automatic pressure external fixator (TAPEF) for the treatment of intertrochanteric fracture / 中国骨伤

<p><b>OBJECTIVE</b>To investigate the mechanical characteristics of new type two-head automatic pressure external fixator in the view of biomechanics.</p><p><b>METHODS</b>Fifteen fresh and humid specimens were selected and divided into experimental group (5 cases) and control group (10 cases). The control group were respectively applied with DHS (5 cases) and traditional external fixator (5 cases). In order to compare the different apparatus, the strength, stiffness and twist mechanical function of femoral intertrochanteric fracture with different device were measured respectively when the specimens were under the pressure of 0-1800 N and loading speed 1.4 mn/min.</p><p><b>RESULTS</b>The strength, stiffness, twist mechanical function and maximum endurance of femora in the experimental group were obviously superior than that of DHS and traditional external fixator (P < 0.05).</p><p><b>CONCLUSION</b>Two head automatic new type pressure external fixator can embed more tightly without sliding, also can prevent the occurrence of coxa vara effectively.</p>

A biomechanical evaluation of the sacroiliac anatomy type bar-plate internal fixation system / 中国骨伤

<p><b>OBJECTIVE</b>To evaluate the biomechanical personality of the sacroiliac anatomy type Bar-plate system (SABP), which was of fixation usage to the fracture or dislocation of the sacroliliac joint.</p><p><b>METHODS</b>Twenty fresh and freeze cadaver pelvises were prepared with pelvic fracture model,compared with different internal fixation systems such as Galveston technique, transiliac rod fixation, reconstruction plate and sacroiliac joint screws using experimental stress analysis methods,and then the stability of the pelvic was obtained and evaluated.</p><p><b>RESULTS</b>Using new SABP system to treat pelvic sacroiliac joint fracture and dislocation was higher 10%, 11%, 16%, 21% in the strength; more 12%, 14%, 21%, 31% in rigidity; less 13%, 14%, 22%, 25% in straining;less 10%, 12%, 16%, 20% in shifting than the Galveston technique, transiliac rod fixation, reconstruction plate and sacroiliac joint screws, with remarkable statistic difference (P < 0.05), and it was even better than cadaver pelvis.</p><p><b>CONCLUSION</b>To treat pelvic facture, the fixation with new SABP system is of better strength, rigidity and stability, and the SABP system is an ideal new application.</p>

Stress test and clinical application of the minimal-invasive dynamic hip screw / 中国骨伤

<p><b>OBJECTIVE</b>To recognize the effect of minimal-invasive dynamic hip screw (MIDHS) on the treatment of intertrochanteric fracture of the hip by biomechanical test and preliminary clinical application.</p><p><b>METHODS</b>Ten artifical made intertrochanteric fractures of femoral specimen from five cadavers were divided into two groups randomly. The fractures in first group were fixed by MIDHS and other group were fixed by dynamic hip (DHS). Biomechanical characteristics of two different devices were compared with the biomechanical character of load-straining, load-displacing, rigidity and strength of femur by statistic analysis. According to the Harris evaluation, healing effect of intertrochanteric fractures was evaluated clinically on the 15 cases.</p><p><b>RESULTS</b>Straining changes of MIDHS were 14% and 11% less than that of DHS on the tensile side and the pressure side respectively; Sinking and horizontal displacement, were 19% and 22% less than that of DHS respectivly. But external and internal stress intensity,axial and bending rigidity were all higher than that of DHS, they were 12%, 11%, 19% and 37%. Maximal destroyed twisting moment (15%) and average twisting rigidity (15%) were both higher than that of DHS, but twisting angle was 18% less. Under the force, of 1 800 N, the open angle of the fracture on transverse section was 2.28 degrees,while the DHS's was 3.60 degrees . The data above were significant differences statistically (P < 0.01). The average Harris score of the 15 cases with intertrochanteric fractures treated by MIDHS was 91, excellent and good rate was 92.7%, without complications of internal fixation failure,postoperative infection and so on.</p><p><b>CONCLUSION</b>The design of minimal-invasive dynamic hip screw is reasonable and effective against rotating, shearing and varus stress force of the fracture, and it provides possibility of implanting the internal fixation with minimal incision. So it is an ideal internal fixation device for the treatment of intertrochanteric fractures.</p>

Influence of the fusion of bone graft in spine of rabbit treated with lower intensity ultrasound / 中国骨伤

<p><b>OBJECTIVE</b>To observe the influence of the fusion of bone graft in spine of rabbits which were treated with lower intensity ultrasound.</p><p><b>METHODS</b>Forty 12-month-old rabbits were made to be the models of bone graft in post-lateral between two homonymy processus transverses in lumbar, and divided into treatment group (B) and control group (A) randomly. Twenty rabbits of treatment group were treated with lower intensity ultrasound, killed after six weeks, and took radiological examination, measured indexs of biomechanics.</p><p><b>RESULTS</b>After 6 weeks of fusion of bone graft, treatment group were higher 6%-7% (P> 0.05) in strength, rigidity, torque andantitwist, maxload than that of control group.</p><p><b>CONCLUSION</b>Lower intensity ultrasound can promote the speed and strength fusion of bone graft in young rabbits.</p>

Three fixation instruments for Schatzker Ⅵ tibial plateau fractures :a biomechanical comparison / 中国基层医药

Objective To compare the biomechanical effect of three fixation instruments for SchatzkerⅥtibial plateau fractures.Methods Twenty four fresh knee specimens were made into models of SchatzkerⅥtibial plateau fractures.The specimens were divided randomly into three groups.Group A were fixed with a lateral periar- ticular plate and a posteromedial antiskid plate,and group B with a lateral periarticutar plate and an anteromedial lim- ited contact dynamic compression plate(LC-DCP),and group C with a lateral periarticular plate and a medical exter- nal fixator.Each model was tested for its biomechanical performance in resisting compression,bending and rotation. Results The performance of group B was higher than group A in anti-compression,anti-bending and anti-rotation, and group C was the poorest,there was no significant difference between group A and group B,and there was signifi- cant difference between group B and group C.Conclusion The biomechanical performance of group B was good. The method might have clinical applications in the treatment of SchatzkerⅥtibial plateau fractures.

Effect of autocontrol micromotion intramedullary interlocking nail on fracture healing: an experimental study / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the effect of autocontrol micromotion locking nail (AMLN) on experimental fracture healing and its mechanism.</p><p><b>METHODS</b>16 goats undergoing both sides of transverse osteotomy of the femoral shafts were fixed intramedullary with AMLN and Gross-Kempf (GK) nail, respectively. The follow-up time was 7, 14, 28 and 56 days. Roentgenographic, biomechanical, histological, scanning electromicroscopic and biochemical analyses were done.</p><p><b>RESULTS</b>(1) The strength of anticompression, antiflexion and antitorsion in the fractural end in the AMLN-fixed group was higher than that of GK nail-fixed group; whereas, the rate of stress shelter in the fractured end decreased significantly (P<0.01). (2) The content of the total collagen, insoluble collagen, calcium and phosphate in the AMLN-fixed group was higher than that in the GK nail-fixed group (P<0.05). (3) Histological observation and quantitative analysis of calluses revealed that AMLN could promote the growth of bridge calluses and periosteum calluses. Hence the fracture healing and remolding process achieved early, which was much better than traditional GK nail fixation. (P<0.05). (4) 7-14 days postoperation, the calluses of AMLN-fixed group was flourish and camellarly arranged and the collagen fibril formed constantly in the absorption lacuna of bone trabecula. 28-56 days postoperation, the collagen fibril was flourish around the absorption lacuna and was parallel to the bone's longitudinal axis. Active bony absorption and formation were seen, so was remolding and rebuilding. Haversian system was intact and the bony structural net was very tenacious because of the deposition of calcium salt. None of the above findings was observed in the GK nail-fixed group.</p><p><b>CONCLUSIONS</b>The design of AMLN accords well with the plastic fixation theory. As the geometry ametabolic system constituted by the intramedullary fixation instruments and the proximal and distal end of the fracture is very firm and stable, the disturbance to the physical stress distributed in the fractural end is light. The generation and conduct of the intermittent physical stress between the fractural parts could reach the balance between stress conduct and stress protection. The feature that the healing and remolding take place at the same time speeds up the fractural healing process.</p>

Study of the morphology and biomechanics of sacral fracture / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To observe the morphological characteristics of sacral fracture under different impact loads.</p><p><b>METHOD</b>Ten fresh pelvic specimens were loaded in dynamic or static state. A series of mechanical parameters including the pressure strain and velocity were recorded. Morphological characteristics were observed under scanning electron microscope.</p><p><b>RESULTS</b>The form of sacral fracture was related to the impact energy. Under low energy impact loads, ilium fracture, acetabulum fracture and crista iliaca fracture were found. Under high energy impact loads, three types of sacral fracture occurred according to the classification of Denis: sacral ala fracture, Type I fracture; sacral foramen cataclasm fracture, Type II fracture; central vertebral canal fracture, Type III fracture. Nerve injury of one or two sides was involved in all three types of sacral fracture. The fracture mechanism of sacrum between the dynamic impact and static compression was significantly different. When the impact energy was above 25 J, sacral foramen cataclasm fracture occurred, involving nerve root injury. When it was below 20 J, ilium and sacral fracture was most likely to occur. When it was 20 approximately 25 J, Type I fracture would occur. While in the static test, most of the fracture belonged to ilium or acetabulum fracture. The cross section of sacrum was crackly and the bone board of Haversian system was brittle, which could lead to separation of bone boards and malposition of a few of cross bone boards.</p><p><b>CONCLUSIONS</b>In dynamic state, sacrum fracture mostly belongs to Type I and Type II, and usually involves the nerve roots. Sacrum fracture is relevant to the microstructures, the distribution of the bone trabecula, the osseous lacuna and the Haversian system of sacrum. The fracture of ilium and acetabulum more frequently appears in static state, with slight wound of peripheral tissues.</p>

The biomechanical study and clinical application of internal fixation with Kirschner wire placed in the nerval fossa of ulna for GartlandⅢsupracondylar fractures of humerus in children / 中华创伤杂志

Objective To perform a biomechanical study on and compare the stability of internal fixation with closed Kirschner wire in different spots from the epicondylus medialis to sulcus nervi ulnaris and epicondylus lateralis of humerus in the treatment of GartlandⅢsupracondylar fractures of humerus in children in order to provide basis for avoiding cubitus varus in clinic.Methods Twenty models of su- pracondylar fractures were made from ten humerus samples,then divided into two groups(group A and group B).They were fixed with closed Kirschner'wires.Ulnar Kirschner wire varied.In group A five spots were selected averagely from the epicondylus medialis to the sulcus nervi ulnaris.Kirschner wires entered from one of the five spots into another spot of humerus.In group B Kirschner wires entered defferent spots of humerus from the central spot of sulcus nervi ulnaris.Biomechanical tests were carried out,such as axial load,axial displacement,stress intensity,axial rigidity and anti-twisty ability.Forty-six children with Gart- landⅢsupracondylar fracture of humerus were treated and followed up for more than one year.Results In beth groups,with the angle of Kirschner wires and fracture side increasing,the strain and the vertical displacement decreased,the stress intensity and the axial rigidity increased,and the anti-twists ability was enhanced.There was statistic difference(P＜0.05).The follow-up of the 46 patients showed the elbow joint function recovered well with no cubitus varus malformation.Conclusion Internal fixation with closed Kirschner wires in sulcus nervi ulnaris from the epicondylus medialis and the epicondylns lateralis of humerus for GartlandⅢsupracondylar fracture of humerus in children has the advantages of enhancing bio- mechanical stability,effective prevention of secondary replacement of outlying black of the fracture and a- voidance of cubitus varus.It can be widely used clinically.