To investigate the effects of augmentation with bone cement on the biomechanics of the dynamic hip screw (DHS) fixation in the intertrochanteric fracture specimen that has a normal bone density.MethodsTwentyfour matched pairs of the embalmed male upper femora (48sides) were used to make the specimens of the intertrochanteric fracture of Type A2. All the specimens were fixed with DHS. The right femur specimen from each pair was fixed by augmentation with DHS (the augmentation group) and the left femur specimen was fixed with the conventional fixation (the control group). Thebiomechanical tests on the bending stiffness and the torsional stiffness were performed with the servohydraulic testing machine in the two groups.ResultsThe maximum load and the maximum torque were 3 852.160 2±143.603 1 N and 15.5±2.6 Nm in the augmentation group and 3 702.966 7±133.860 1 N and 14.7±3.4 Nm in the control group. There was no significant difference in the biomechanical effects between the two groups (P＞0.05). Conclusion The augmenting fixation with bone cement in the intertrochanteric fracture specimen with a normal bone density has no significant effect on the strength of the DHS augmentation or on the overall stability of the fractured bone.
ObjectiveTo discuss the effect of three different ways of annulus fibrosus incision on the biomechanical strength of intervertebral disc.
MethodsA total of 30 goats underwent intervertebral disc nucleus pulposus extraction at L3, 4 and L4, 5 by the working channel in group A (n=10), by circular incision in group B (n=10), and by square incision in group C (n=10). The body weight, male and female ratio, age, intraoperative blood loss, and wound healing time were recorded and compared among 3 groups. The survival rate and wound healing situation were observed after operation. At 24 weeks after operation, the goats were sacrificed, MRI images were taken to observe the signal intensity of nucleus pulposus. The disc height of L3, 4 and L4, 5 was measured to calculate the loss of disc height; biomechanical test was used to assess the strength of the disc and anulus. Histological staining was also conducted to observe the repair effect at L4, 5.
ResultsThere was no significant difference in body weight, male to female ratio, age, intraoperative blood loss, and wound healing time among groups (P>0.05). All goats survived to the end of the experiment. MRI examination showed decreased signal intensity in 3 groups, indicating intervertebral disc degeneration. According to modified Thompson classification method, the degree of intervertebral disc degeneration of group A was significantly higher than that of groups B and C (P<0.05), but no significant difference was found between groups B and C (P>0.05). Difference was not significant in intervertebral space height before operation among 3 groups (P>0.05). But after 24 weeks, the intervertebral space height in group A was significantly higher than that in groups B and C (P<0.05), and the intervertebral space height loss in group A was significantly lower than that in groups B and C (P<0.05). The biomechanical strength in group A was also significantly higher than that in groups B and C (P<0.05), but no significant difference was found between group B and group C (P>0.05). HE and Masson staining showed good continuity of annulus fibrosus and clear layers in group A; poor continuity of annulus fibrosus and obvious scar tissues were observed in groups B and C.
ConclusionApplication of working channel may have less destruction of annulus fibrosus, it plays a positive role in the maintenance of biomechanical strength and repair of annulus fibrosus.
Objective To ascertain whether augmentation pedicle screw fixation with polymethylmethacrylate (PMMA) can enhance the stability of unstable thoracolumbar burst fractures of osteoporotic spine. Methods Six fresh frozen female osteoporotic spines (T10-L5) were harvested and an anterior and posterior columnunstable model of L1 was made. Each specimen was fixated with plate and the stability test were performed by flexion, extension, axial rotation and lateral bending. The test of fatigue was done with MTS 858.The tests were repeated after screws were augmented with PMMA. To compare the biomechanical stability of 6 different conditions:○anormal specimens(control), ○bdefectmodel fixed with plate, not augmented and not fatigued, ○cafter fatigued, not augmented, ○dscrews augmented with PMMA, not fatigued, ○e after augmented and fatigued. ResultsIn ○b,○d and ○e conditions, the ranges of motion(ROM) were 6.23±1.56，4.49±1.00，4.46±1.83 inflexion and 6.60±1.80，4.41±0.82，4.46±1.83 in extension. There was no significant difference (Pgt;0.05), they were significantly smaller than those in ○a and ○c conditions (8.75±1.88，1.47±2.25 and 8.92±2.97，12.24±3.08) (Plt;0.01).Conclusion The results demonstrated that augmentation pedicle screws fixation with PMMA can increase the stability of osteoporotic spine.
Objective To demonstrate the anatomical and biomechanical basis of scaphoid ring sign in advanced Kienbock’s disease. Methods The study consisted of two sections. The ligaments stabilizing the proximal pole of the scaphoid were observed in 5 specimens. Under 12 kg dead weight load through the tendons of the flexion carpal radial, the flexion carpal ulnar, the extension carpal radial, and the extension carpal ulnar for 5 minutes, the stresses of the scaphoid fossa and lunate fossa were measured in the case of neutral, flexion, extension, radial deviation and ulnar deviation of the wrist joint under normal and rupture conditions respectively by FUJI prescale film and FPD-305E,306E.Results Based on anatomical study, the ligaments stabilizing the proximal pole of the scaphoid consisted of the radioscaphocapitate ligament, long radiolunate ligament and scapholunate interosseous ligament; and the latter two ligaments restricted dorsal subluxation of the proximalpole of the scaphoid. When compared rupture condition with normal condition, thescaphoid fassa stress of radial subregion was not significantly different (0.90±0.43 vs 0.85±0.15), and the ones of palmar, ulnar and dorsal subregions decreased (0.59±0.20, 0.52±0.05 and 0.58±0.23 vs 0.77±0.13, 0.75±0.08 and0.68±0.09) in the case of extension; the scaphoid fassa stresses of all subregions increased or had no difference in the case of neural, flexion, radial deviation and ulnar deviation. The lunate fossa stresses of all subregions increased in thecase of neural, and the ones of all subregions decreased or had no difference inthe case of flexion, extension, radial deviation and ulnar deviation.Conclusion Rotary scaphoid subluxation should be treated operatively at Ⅲ B stage of Kienbock’s disease to avoid traumatic arthritis of theradioscaphoid joint.
Objective To evaluate the effect of self-designed antirotation reduction internal fixator(ARRIF) on treating different spine segment fracture.Methods From August 1999 to March 2003, 76 patients(48 males and 28 females, aged from 22 to 59 with an average of 34.1) with thoracolumbar fracture were operatively treated by ARRIF. The follow-up period ranged from 6 to 21 months(15 months in average). Classification according to injury segment: flexion compression racture 27 cases, burst fracture 42 cases, flexion distraction injury 3 cases, flexion revolving type fracture dislocation 2 cases, shear force type dislocation 2 cases. Classification according Frankel’s grade:A grade 16 cases, B grade 15 cases, C grade 27 cases, D grade 10 cases, E grade 8 cases.Operation duration, volume of bleeding, incidence postoperation complication and effect of reduction fixation were observed. Results The operation duration of ARRIF was 1.2 h in average, and there was about 200 ml volume of bleeding during operation. The nerve function showed one Frankel’s grade improvement after operation were as follows:A grade 8 cases(50%), B grade 11 cases (73.3%), C grade20 cases(74.1%), D grade 3 cases (30%); 2 Frankel’s E cases have no nerve function changes.The nerve function damage have no aggravation in all the patients,the postoperation Cobb’s angle was averagely corrected 22°. The horizontal displacement of dislocation vertebrae was averagely corrected 28% in sagittal plane, the statistical analysis had significant variance(Plt;0.01).ARRIF had no complications of the breakage of screws and rods. Conclusion ARRIF proves to be a valid internal fixator in reducing and fixing different thoracic lumbar segment spine fracture.
Accurately evaluating the local biomechanics of arterial wall is crucial for diagnosing and treating arterial diseases. Indentation measurement can be used to evaluate the local mechanical properties of the artery. However, the effects of the indenter’s geometric structure and the analysis theory on measurement results remain uncertain. In this paper, four kinds of indenters were used to measure the pulmonary aorta, the proximal thoracic aorta and the distal thoracic aorta in pigs, and the arterial elastic modulus was calculated by Sneddon and Sirghi theory to explore the influence of the indenter geometry and analysis theory on the measured elastic modulus. The results showed that the arterial elastic modulus measured by cylindrical indenter was lower than that measured by spherical indenter. In addition, compared with the calculated results of Sirghi theory, the Sneddon theory, which does not take adhesion forces in account, resulted in slightly larger elastic modulus values. In conclusion, this study provides parametric support for effective measurement of arterial local mechanical properties by millimeter indentation technique.
ObjectiveTo design a new type of transarticular cuboid bone plate by measuring and collecting the anatomic data of the articular surface around cuboid, and to carry out comparative biomechanical study.
MethodsThe angle α (between the fifth metatarsocuboid joint and the fifth metatarsal bone) and the angle β (between the fifth metatarsocuboid joint and the calcaneocuboid joint) were measured in 100 adults on medial oblique X-ray film and 30 adult foot specimens. Based on literature data, the transarticular cuboid bone plate was designed with an angle α of 70° and an angle β of 30°. Six adult cadaver feet were chosen and were transected approximately 15 cm proximal to the ankle. Five strain gauges were placed at the calcaneus, cuboid, and the fourth and fifth metatarsal bones. The vertical pressure was loaded on the foot at 0-600 N, the strain value was measured. Then the cuboid fracture model was established and 600 N load was given on foot to measure the strain value and compare with the strain value before fracture. The specimens were randomly divided into groups A and B (n=3). Fracture was fixed with transarticular cuboid bone plate and 9 screws in group A and with double plate and 8 screws in group B, then the 600 N load was given to measure the strain value and vertical displacement of the fracture fragments.
ResultsAfter loads of 0-600 N on the foot, the strain value of the 5 points showed an increased trend. No significant difference was found in the strain value between pre- and post-fracture at a, d, and e points P>0.05), but it was significantly larger at post-fracture than pre-fracture at b and c points (P<0.05). After fracture fixation, no significant difference was shown in the strain value at 5 points between groups A and B when loads of 0-600 N was given P>0.05). The experimental data showed that the strain value change mainly focused on the fracture site under the same load, so the strain value after fracture fixation was similar to that before fracture at b and c points P>0.05). The vertical displacement values of medial and lateral fracture fragments in group A[(0.804±0.011) mm and (0.672±0.036) mm] were significantly less than those in group B[(1.126±0.083) mm and (1.007±1.103) mm] (t=-6.711, P=0.003; t=-5.307, P=0.006).
ConclusionThrough biomechanical study, a new type of transarticular cuboid bone plate has better fixation effect.
Objective
To evaluate the fixation strength of expansive pedicle screw (EPS) at different bone mineral density (BMD) levels, further to provide theoretical evidence for the clinical application of the EPS in patients with osteoporosis.
Methods
Fresh human cadaver spines (T12-L5 spines) were divided into 4 levels: normal BMD, osteopenia, osteoporosis, and severe osteoporosis according to the value of BMD, 12 vertebra in each level. Conventional pedicle screw (CPS) or EPS was implanted into the bilateral vertebra in CPS group and EPS group, respectively, 12 screws in each group per BMD level. Screw pullout tests were conducted. The maximum pullout strength, stiffness, and energy absorption were determined by an AG-IS material testing machine with constant rate of loading in a speed of 5 mm/ min.
Results
With the decline of BMD from normal to severe osteoporosis level, the maximum pullout strength and the stiffness correspondingly declined (P lt; 0.05). In CPS group, the energy absorption gradually decreased (P lt; 0.05); in EPS group, significant difference was found between other different BMD levels (P lt; 0.05) except between normal BMD and osteopenia and between osteoporosis and severe osteoporosis (P gt; 0.05). At the same BMD level, the maximum pullout strength of EPS group was significantly larger than that of CPS group (P lt; 0.05); the stiffness of EPS group was significantly higher than that of CPS group (P lt; 0.05) except one at normal BMD level; and no significant difference was found in the energy absorption between 2 groups (P gt; 0.05) except one at osteopenia level. No significant difference was found in maximum pullout strength, stiffness, and energy absorption between EPS group at osteoporosis level and CPS group at osteopenia level (P gt; 0.05); however, the maximum pullout strength, stiffness, and energy absorption of EPS group at severe osteoporosis level were significantly lower than those of CPS group at osteopenia level (P lt; 0.05).
Conclusion
Compared with CPS, the EPS can significantly improve the fixation strength, especially in patients with osteopenia or osteoporosis.
Osteoporosis is a degenerative disease characterized by decreased bone mass and destruction of bone microstructure. At present, previous studies have found that the structure and content of type Ⅰ collagen fibers are closely related to osteoporosis. However, there have been few studies on the prevention and treatment of osteoporosis using type Ⅰ collagen fibers as therapeutic targets. In this paper, the relationships between type Ⅰ collagen fibers and osteoporosis, biomechanics, bone matrix and bone strength are discussed. At the same time, the regulation of type Ⅰ collagen-related signaling pathways in osteoporosis is summarized, such as the signaling pathways of cathepsin K, transforming growth factor-β/Sma- and Mad-related protein, transforming growth factor-β/bone morphogenetic protein, c-jun N-terminal protein kinase and Wnt/β-catenin, in order to provide a new therapeutic direction for the prevention and treatment of osteoporosis.
Objective To evaluate the effect of polymethylmethacrylate (PMMA) augmentation on cervical stabil ity after anterior cervical interbody fusion (ACIF) before and after fatigue. Methods Twelve porcine cervical spines (C3-7) were subjected to testing angular displacement parameters, including the range of motion (ROM), neutral zone (NZ), and elastic zone (EZ), in nondestructive flexion and extension, right/left lateral bending, and left/right rotation on Motion Analysis motion capture system and MTS-858 servo-hydraul ic testing machine. Intact cervical spines served as control group (group A); oneleveldiscectomy and fusion was performed with anterior plate fixation based on group A as group B; flexion and extension,left/right lateral bending (5 000 cycles) fatigue testing based on group B as group C; the augmentation screw channel was used based on group C as group D; and flexion and extension, left/right lateral bending fatigue testing were performed based on group D as group E. Results The ROM, NZ, and EZ in group A were significantly different from those in other groups (P lt; 0.05) at flexion/extension, left/right bending, and left/right rotation. The ROM, NZ, and EZ in group B were significantly smaller than those in group C (P lt; 0.05) in flexion/extension, left/right bending, and left/right rotation, but there was no significant difference when compared with group D (P gt; 0.05). The ROM and NZ in flexion/extension and the EZ in flexion in group B were significant smaller than those in group E (P lt; 0.05), but there was no significant difference in the other indexes (P gt; 0.05). The ROM, NZ, and EZ in group C in flexion and extension, left/right lateral bending, and left/right rotation were significantly higher than those in groups D and E (P lt; 0.05). The ROM and NZ in flexion and extension and left/right lateral bending, and the ROM in left/right rotation, and the EZ in flexion and extension, right bending, and left/right rotation in group D were significantly smaller than those in group E (P lt; 0.05), but there was no significant difference in the other indexes (P gt; 0.05). Conclusion PMMA augmentation can significantly increase the instant cervical stabil ity and provide a biomechanics basis in cervical anterior plate fixation.
