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 explore the biomechanical difference between the different fixations of cortical bone plate allograft. Methods Twenty-seven cadaveric femurs were harvested and were made into the simulated fracture models, which were equally divided into Groups A, B and C. In Group A, the models were fixed with 2 bone plate allografts (110 mm×10 mm×3 mm); in Group B, the models were fixed with 2 struts (110 mm×10 mm×3 mm) and 5 bone screws; in Group C, the models were fixed with 1 strut (110 mm×10 mm×3 mm) and 5 bone screws. The biomechanical tests for the three-piont bending, torsion, and compression were performed. The parameters studied included the values of the displacements in the three-piont bending tests and the compression tests, and the maximum loads during the bending, the compression, and the torsion. Results As for all the stiffness parameters tested, Group A showed the greatest displacements among the threegroups（P＜0.05）, except the compressive stiffness parameter, which was similar to that in Group B. The maximum loads of the three-point bending, the torsion, and the compression in Group A were 1.65±0.34 kN, 554.3±49.34 N, and 7.78±0.82 Nm, respectively; in Group B, they were 1.12±0.37 kN, 428.00±37.40 N,and 3.39±0.22 Nm, respectively; in Group C, they were 0.71±0.46 kN, 218.67±36.53N, and 1.74±0.12 Nm, respectively. Group A had a significantly greater strengththan the other 2 groups(P＜0.05). Conclusion The strength of the cortical bone plate allograft is related to its different fixations. The two cortical bone plate allografts have a greater strength and stiffness than the struts fixed with the bone screws, which can meet the clinical requirement.
To evaluate the changes in stabil ity of the wrist after experimental traumatic triangular fibrocartilage complex (TFCC) lesions, and to provide basic theoretical criteria for cl inical treatment. Methods Fourteen adult cadaver upper extremities specimens were included. Two of 14 specimens were tested in pre-experiment. The specimens were tested in a INSTRON 8874 biomechanics measuring instrument. First a dorsal arthrotomy (ART) was performed, and second test was with 1 of 4 different experimental lesions according to Palmer’s classification of traumatic TFCC lesions (n=3). 1A: central perforation; 1B: ulnar avulsion with or without fracture of processus styloideus ulnae; 1C: distal avulsion with l igament injury; 1D: radial avulsion. Forced internal∕external rotation torque were recorded in the interval — 60° to 60° of flexion. Results The average torque of the dorsal ART was (0.713 ± 0.121) Nm, and the 1B-1 lesion (ulnar avulsion without ulnar styloid fracture) was (0.709 ± 0.134) Nm, the 1B-2 lesion (ulnar avulsion with ulnar styloid fracture) was (0.409 ± 0.113) Nm. The difference between the 1B-1 lesion and the dorsal ART was not significant but the difference between the 1B-2 lesion and the dorsal ART was significant (P lt; 0.05). The average torque of the 1C lesion in about 45° of wrist extention and flexion were (0.878 ± 0.184) Nm and (0.988 ± 0.197) Nm, and the dorsal ART were (1.510 ± 0.173) Nm and (1.540 ± 0.093) Nm. The difference between the two groups was significant (P lt; 0.05). The 1A lesion and 1D lesion did not alter significantly wrist stabil ity. Conclusion The 1B-2 lesion and 1C lesion alter significantly the stabil ity of the wrist.
【Abstract】 Objective To determine the three-dimensional stabil ity of atlantoaxial reconstruction withanterior approach screw fixation through C2 vertebral body to C1 lateral mass and Gall ie’s technique (ASMG) for C1,2instabil ity. Methods Twenty-five human cadaveric specimens (C0-3 ) were divided randomly into 5 groups (n=5). Thethree-dimensional ranges of motion C1 relative to C2 were measured under the five different conditions：the intact state group (group A), type II odontoid fracture group (group B), posterior C1,2 transarticular screw fixation group (group C), ASM group (group D) and ASMG group (group E). The three-dimensional ranges of motions C1 relative to C2 by loading ± 1.5 Nm were measured under the six conditions of flexion/extension, left/right lateral bending, and left/right axial rotation. The obtained data was statistically analyzed. Results In each group, the three-dimensional ranges of motion C1 relative to C2 under the six conditions of flexion/extension, left/right lateral bending, and left/right axial rotation were as follows: in group A (8.10 ± 1.08), (8.49 ± 0.82), (4.79 ± 0.47), (4.93 ± 0.34), (28.20 ± 0.64), (29.30 ± 0.84)°; in group B (13.60 ± 1.25), (13.80 ± 0.77), (9.64 ± 0.53), (9.23 ± 0.41), (34.90 ± 0.93), (34.90 ± 1.30)°; in group C (1.62 ± 0.10), (1.90 ± 0.34), (1.25 ± 0.13), (1.37 ± 0.28), (0.97 ± 0.14), (1.01 ± 0.17)°; in group D (2.03 ± 0.26), (2.34 ± 0.49), (1.54 ± 0.22), (1.53 ± 0.30), (0.80 ± 0.35), (0.76 ± 0.30)°; in group E (0.35 ± 0.12), (0.56 ± 0.34), (0.44 ± 0.15), (0.55 ± 0.16), (0.43 ± 0.07), (0.29 ± 0.06)°. Under the six conditions, there were generally significant differences between group A and other four groups, and between group B and groups C, D and E (P lt; 0.001), and between group E and groups C, D in flexion/ extension and left/right lateral bending (P lt; 0.05). There was no significant difference between group E and groups C, D in left/right axial rotation (P gt; 0.05). Conclusion In vivo biomechanical studies show that ASMG operation has unique superiority in the reconstruction of the atlantoaxial stabil ity, especially in controll ing stabil ity of flexion/extension and left/right lateral bending, and thus it ensures successful fusion of the implanted bone. It is arel iable surgical choice for the treatment of the obsolete instabil ity or dislocation of C1, 2 joint.
Objective To investigate whether or not posterolateral rotatory instabil ity of the elbow is due to type-I and type-II coronoid process fracture together with anterior bundle of medial collateral l igament (AMCL) injury so as to provide a theoretic basis for its cl inical treatment. Methods Ten fresh-frozen upper extremities were collected from cadavera which was donated voluntarily with no evidence of fracture, dislocation, osteoarthritis, mechanical injury of the surrounding l igament and joint capsule. They included 9 males and 1 female with an average age of 25.1 years (range, 19-40 years), including 3 cases at left sides and 7 cases at right sides. All specimens were transected at the upper midhumeral and carpal levels preserving the distal radioulnar joints to get the bone-l igament specimens. An axial load of 100 N compressing the elbow joint was appl ied along the shaft of the forearm in the sagittal plane through the biomechanical study system. The load-displacement plot was measured and analyzed at elbow flexion of 90, 60, and 45° and under four conditions (intact elbow, type-I coronoid process fracture, type-I coronoid process fracture with AMCL deficient, and type-II coronoid process fractures with AMCL deficient). Results The posterior displacements were maximum at 90° elbow flexion. Hence, the results at 90° elbow flexion were analyzed: under condition of intact elbows, the posterior displacement was the smallest (2.17 ± 0.42) mm and the posterolateral rotatory stabil ity was the greatest; under condition of type-I coronoid process fracture, the posterior displacement was (2.20 ± 0.41) mm, showing no significant difference compared with that of the intact elbow (P gt; 0.05); under condition of type-I coronoid process fracture with AMCL deficient, the posterior displacement was (2.31 ± 0.34) mm, showing no significant difference compared with that of intact elbow (P gt; 0.05); and under condition of type-II coronoid process fracture with AMCL deficient, the posterior displacement was (2.65 ± 0.38) mm, showing a significant difference compared with that of intact elbow (P lt; 0.05). There was no macroscopic ulnohumeral dislocation or radial head dislocation during the experiment. Conclusion An simple type-I coronoid process fracture or with AMCL deficient would not cause posterolateral rotatory instabil ity of elbow and may not need to be repaired. But type-II coronoid process fractures with AMCL deficient can cause posterolateral rotatory instabil ity of elbow, so the coronoid process and the AMCL should be repaired or reconstructed to restore posterolateral rotatory stabil ity as well as valgus stabil ity.
ObjectiveTo study the biomechanical stability of neckwear-knot-loop-ligature fixation for tibial eminence avulsion fractures by comparing with cannulated screw fixation and suture anchor fixation.
MethodsTwenty-four fresh porcine knee joints were selected. After the model of tibial eminence avulsion fracture (type Ⅲ) was made, 24 samples were randomly divided into 3 groups: neckwear-knot-loop-ligature group (group A), cannulated screw group (group B), and suture anchor group (group C), 8 samples in each group. The Universal electromagnetic and mechanical testing machines were used for the biomechanical tests. After 200 cyclic tests, pull-out test was done until fixation failure. The maximum failure load, yield load, stiffness, and displacement were measured.
ResultsFailure mode: the displacement was beyond limit in 8 samples of group A; screws extraction (5 samples) and bone fragment re-fracture (3 samples) were observed in group B; and suture anchor extraction (4 samples), suture rupture (3 samples), and suture thread cutting (1 sample) were found in group C. Biomechanical test: From groups A to C, the maximum failure load and yield load showed significant decreasing tendency (P<0.05), but the displacements showed significant increasing tendency (P<0.05). The stiffness also gradually decreased, but differences was not significant (P>0.05).
ConclusionCompared with cannulated screw and suture anchor, neckwear-knot-loop-ligature fixation for tibial eminence avulsion fracture has good biomechanical performance and the advantages of firm fixation and simple operation.
ObjectiveTo discuss the biomechanical stability of locked reconstruction plate for internal fixation of transverse and posterior wall acetabular fracture so as to provide a reliable basis for clinical application.
MethodsThe models of transverse and posterior wall acetabular fracture were established in 16 anti-corrosion acetabular specimens from 8 adult cadavers, which were randomly divided into experimental group and control group (n=8). Fracture was fixed with 10-hole posterior column locked reconstruction plate in the experimental group, and with 10-hole posterior column reconstruction plate combined with anterior column lag screw and posterior wall screws in the control group. Biomechanical testing machine was used for loading of 5/6 donor body mass the specimen in a speed of 15 N/s; the loading time was calculated and vertical loading.The longitudinal and quadrilateral body displacements of fracture were recorded to compare the biomechanical stability was performed.
ResultsThe quadrilateral body displacement of the experimental group[(1.99±0.32) mm] was greater than that of the control group[(1.75±0.22) mm], but there was no significant difference (t=-1.735, P=0.105). The longitudinal displacement[(1.56±049) mm] and the displacement of the posterior wall fracture block[(0.86±0.33) mm] in the experimental group were lower than those of the control group[(1.64±0.51) and (1.01±0.35) mm], showing no significant difference between 2 groups (t=0.293, P=0.772; t=1.516, P=0.154).
ConclusionFor transverse and posterior wall acetabular fracture, application of locked reconstruction plate can provide sufficient biomechanical stability, reduce the risk of screw placement to acetabular joints.
Objective To evaluate the role of glenoid osseous structure on anterior stabil ity of shoulder so as to provide the biomechanical basis for cl inical treatment. Methods Ten fresh shoulder joint-bone specimens were collected from10 adult males cadavers donated voluntarily, including 4 left sides and 6 right sides. The displacements of the specimens were measured at 0° and 90° abduction of shoulder joint by giving 50 N posterior-anterior load under the conditions as follows: intact shoulder joint, glenoid l ip defect, 10% of osseous defect, 20% of osseous defect, and repairing osseous defect. Results For intact shoulder joint, glenoid l i p defect, 10% of osseous defect, 20% of osseous defect, and repairing osseous defect, the displacements were (10.73 ± 2.93), (11.43 ± 3.98), (13.58 ± 4.86), (18.53 ± 3.07), and (12.77 ± 3.13) mm, respectively at 0° abduction of shoulder joint; the displacements were (8.41 ± 2.10), (8.55 ± 2.28), (9.06 ± 2.67), (12.49 ± 2.32), and (8.55 ± 2.15) mm, respectively at 90° abduction of shoulder joint. There was no significant difference between intact shoulder joint and others (P gt; 0.05) except between intact shoulder joint and 20% of osseous defect (P lt; 0.05). Conclusion When shoulder glenoid l ip defects or the glenoid osseous defect is less than 20%, the shoulder stabil ity does not decrease obviously, indicating articular l igament complex is not damaged or is repaired. When glenoid osseous defect is more than 20% , the shoulder stabil ity decreases obviously even if articular l igament complex is not damaged or is repaired. Simultaneous repair of glenoid osseous defect andarticular l igament complex can recover the anterior stabil ity of the shoulder.
Objective To review the biomechanics of internal fixators for proximal humeral fractures, and to compare the mechanical stabil ity of various internal fixators. Methods The l iterature concerning the biomechanics of internal fixators for proximal humeral fractures was extensively analyzed. Results The most important things for best shoulder functional results are optimal anatomical reduction and stable fixation. At present, there are a lot of methods to treat proximal humeral fractures. Locking-plate exhibites significant mechanical stabil ity and has many advantages over other internal fixators by biomechanical comparison. Conclusion Locking-plate has better fixation stabil ity than other internal fixators and is the first choice to treat proximal humeral fractures.
ObjectiveTo compare the biomechanical stability of acetabular transverse fracture fixed with single column locking reconstruction plate, locking reconstruction plate combined with lag screw, and double columns lag screws.
MethodsAcetabular transverse fractures were established in 20 adult fresh semi-pelvis specimens, and divided into 5 groups randomly (n=4). The anterior columns were fixed with locking reconstruction plates in group A; the posterior columns were fixed with locking reconstruction plates in group B; the anterior columns were fixed with locking reconstruction plates and the posterior columns with lag screws in group C; the anterior columns were fixed with lag screws and the posterior columns with locking reconstruction plates in group D; the double columns were fixed with lag screws in group E. When loading three times weight, the longitudinal displacement of fracture fragment was measured, and the shear rigidity was calculated to compare the stability among groups.
ResultsThe longitudinal displacement of groups A and B were significantly greater than that of groups C, D, and E (P<0.05), and the shear rigidity of groups A and B were significantly lower than that of groups C, D, and E (P<0.05). The longitudinal displacement of group B was significantly greater than that of group A (P<0.05), but no significant difference was found in the shear rigidity between groups A and B (P>0.05). There was no significant difference in the longitudinal displacement and shear rigidity among groups C, D, and E (P>0.05).
ConclusionLocking reconstruction plate combined with lag screw and double columns lag screws have similar stability, they have stronger stability than the single column locking reconstruction plate. The stability of anterior column locking reconstruction plate is better than that of the posterior column locking reconstruction plate.
