ObjectiveTo evaluate the stability of the fixation technique for the crossed rods consisting of occipital plate and C2 bilateral lamina screws by biomechanical test.MethodsSix fresh cervical specimens were harvested and established an atlantoaxial instability model. The models were fixed with parallel rods and crossed rods after occipital plate and C2 bilateral laminae screws were implanted. The specimens were tested in the following sequence: atlantoaxial instability model (unstable model group), under parallel rods fixation (parallel fixation group), and under crossed rods fixation (cross fixation group). The range of motion (ROM) of the C0-2 segments were measured in flexion-extension, left/right lateral bending, and left/right axial rotation. After the test, X-ray film was taken to observe the internal fixator position.ResultsThe biomechanical test results showed that the ROMs in flexion-extension, left/right lateral bending, and left/right axial rotation were significantly lower in the cross fixation group and the parallel fixation group than in the unstable model group (P<0.05). There was no significant difference between the cross fixation group and the parallel fixation group in flexion-extension and left/right lateral bending (P>0.05). In the left/right axial rotation, the ROMs of the cross fixation group were significantly lower than those of the parallel fixation group (P<0.05). After the test, the X-ray film showed the good internal fixator position.ConclusionThe axial rotational stability of occipitocervical fusion can be further improved by crossed rods fixation when the occipital plate and C2 bilateral lamina screws are used.
ObjectiveTo evaluate the effect of nickel-titanium three-dimensional memory alloy mesh combined with autologous bone for living model of canine tibial plateau collapse fracture by biomechanical testing. MethodsSixteen healthy 12-month-old Beagle dogs were randomly divided into 4 group, 4 dogs in each group. The dogs were used to establish the tibial plateau collapse fracture model in groups A, B, and C. Then, the nickel-titanium three-dimensional memory alloy mesh combined with autologous bone (the fibula cortical bone particles), the artificial bone (nano-hydroxyapatite), and autologous fibula cortical bone particles were implanted to repair the bone defects within 4 hours after modeling in groups A, B, and C, respectively; and the plate and screws were fixed outside the bone defects. The dogs were not treated in group D, as normal control. At 5 months after operation, all animals were sacrificed and the tibial specimens were harvested and observed visually. The destructive axial compression experiments were carried out by the biomechanical testing machine. The displacement and the maximum failure load were recorded and the axial stiffness was calculated. ResultsAll animals stayed alive after operation, and all incisions healed. After 1-3 days of operation, the animals could stand and move, and no obvious limb deformity was found. The articular surfaces of the tibial plateau specimens were completely smooth at 5 months after operation. No obvious articular surface collapse was observed. The displacement and maximum failure load of specimens in groups A and D were significantly higher than those in groups B and C (P<0.05). But no significant difference was found between groups A and D and between groups B and C (P>0.05). ConclusionThe nickel-titanium three-dimensional memory alloy mesh combined with autologous bone for subarticular bone defect of tibial plateau in dogs has good biomechanical properties at 5 months after operation, and has better axial stiffness when compared with the artificial bone and autologous bone graft.
Objective
To discuss the role of the bone suture anchors for repair of avulsed deep radioulnar ligaments in maintaining the rotatory stability of the distal radioulnar joint.
Methods
Nine upper limbs specimens were selected from fresh adult cadavers to make wrist joint-bone capsular ligaments complex specimen. All the specimens were tested under conditions of intact (normal group), deep radioulnar ligaments injury (injury group), and deep radioulnar ligaments injury repaired with anchoring (repair group). The internal and external rotation torque values were recorded in 45° wrist extension, neutral position, and 45° wrist flexion by AG-IS series MS biomechanical testing system. The statistic software was used to compare difference in rotation torque between groups.
Results
In 45° wrist extension, neutral position, and 45° wrist flexion, the internal rotation torque values in normal group were (0.83±0.33), (0.86±0.34), and (0.36±0.30) N·m respectively; the external rotation torque values were (0.86±0.38), (0.44±0.22), and (0.25±0.21) N·m respectively. The internal rotation torque values in injury group were (0.18±0.17), (0.22±0.17), and (0.16±0.15) N·m respectively; the external rotation torque values were (0.27±0.26), (0.13±0.17), and (0.04±0.04) N·m respectively. The internal rotation torque values in repair group were (0.79±0.34), (0.73±0.33), and (0.41±0.23) N·m respectively; the external rotation torque values were (0.80±0.39), (0.41±0.22), (0.41±0.40) N·m respectively. In 45° wrist extension, neutral position, and 45° wrist flexion, the internal and external rotation torque values in injury group were significantly lower than those in normal group and repair group (P<0.05), but no significant difference was found between repair group and normal group (P>0.05).
Conclusion
The deep radioulnar ligaments are important structure for maintaining rotatory stability of distal radioulnar joint. Bone anchoring of the avulsed deep radioulnar ligaments to the ulna fovea is critically important in reconstructing function anatomy of the distal radioulnar joint.
Objective To review the biomechanical research progress of internal fixation of tibial plateau fracture in recent years and provide a reference for the selection of internal fixation in clinic. Methods The literature related to the biomechanical research of internal fixation of tibial plateau fracture at home and abroad was extensively reviewed, and the biomechanical characteristics of the internal fixation mode and position as well as the biomechanical characteristics of different internal fixators, such as screws, plates, and intramedullary nails were summarized and analyzed. Results Tibial plateau fracture is one of the common types of knee fractures. The conventional surgical treatment for tibial plateau fracture is open or closed reduction and internal fixation, which requires anatomical reduction and strong fixation. Anatomical reduction can restore the normal shape of the knee joint; strong fixation provides good biomechanical stability, so that the patient can have early functional exercise, restore knee mobility as early as possible, and avoid knee stiffness. Different internal fixators have their own biomechanical strengths and characteristics. The screw fixation has the advantage of being minimally invasive, but the fixation strength is limited, and it is mostly applied to Schatzker typeⅠfracture. For Schatzker Ⅰ-Ⅳ fracture, unilateral plate fixation can be used; for Schatzker Ⅴand Ⅵ fracture, bilateral plates fixation can be used to provide stronger fixation strength and avoid the stress concentration. The intramedullary nails fixation has the advantages of less trauma and less influence on the blood flow of the fracture end, but the fixation strength of the medial and lateral plateau is limited; so it is more suitable for tibial plateau fracture that involves only the metaphysis. Choosing the most appropriate internal fixation according to the patient’s condition is still a major difficulty in the surgical treatment of tibial plateau fractures. Conclusion Each internal fixator has good fixation effect on tibial plateau fracture within the applicable range, and it is an important research direction to improve and innovate the existing internal fixator from various aspects, such as manufacturing process, material, and morphology.
Objective To investigate the effects of percutaneous cement discoplasty (PCD) and percutaneous cement interbody fusion (PCIF) on spinal stability by in vitro biomechanical tests. Methods Biomechanical test was divided into intact (INT) group, percutaneous lumbar discectomy (PLD) group, PCD group, and PCIF group. Six specimens of L4, 5 (including vertebral bodies and intervertebral discs) from fresh male cadavers were taken to prepare PLD, PCD, and PCIF specimens, respectively. Before treatment and after the above treatments, the MTS multi-degree-of-freedom simulation test system was used to conduct the biomechanical test. The intervertebral height of the specimen was measured before and after the axial loading of 300 N, and the difference was calculated. The range of motion (ROM) and stiffness of the spine in flexion, extension, left/right bending, and left/right rotation under a torque of 7.5 Nm were calculated. Results After axial loading, the change of intervertebral height in PLD group was more significant than that in other three groups (P<0.05). Compared with INT group, the ROM in all directions significantly increased and the stiffness significantly decreased in PLD group (P<0.05). Compared with INT group, the ROM of flexion, extension, and left/right rotation in PCD group significantly increased and the stiffness significantly decreased (P<0.05); compared with PLD group, the ROM of flexion, extension, and left/right bending in PCD group significantly decreased and the stiffness significantly increased (P<0.05). Compared with INT group, ROM of left/right bending in PCIF group significantly decreased and stiffness significantly increased (P<0.05); compared with PLD group, the ROM in all directions significantly decreased and the stiffness significantly increased (P<0.05); compared with PCD group, the ROM of flexion, left/right bending, and left/right rotation significantly decreased and stiffness significantly increased (P<0.05). Conclusion Both PCD and PCIF can provide good biomechanical stability. The former mainly affects the stiffness in flexion, extension, and bending, while the latter is more restrictive on lumbar ROM in all directions, especially in bending and rotation.
ObjectiveTo review the development and clinical application of ankle prosthesis.MethodsThe recent literature on ankle prosthesis design and clinical application was reviewed and analyzed. ResultsCompared with the hip and knee prostheses, the ankle prosthesis develops slowly and has been developed to the third generation. The ankle joint has a special structure of multi-axis movement. The design of the first and second generations of prostheses is not conformed to the biomechanics of the ankle. The third generation of prosthesis is more conform to the characteristics of ankle biomechanics, with high postoperative survival rate and satisfactory clinical outcome. ConclusionAt present, the survival rate of ankle prosthesis is low, and there is still much room for improvement in biomechanics, materials, and other aspects.
Objective To investigate ideal screw implant angle in reconstruction of tibiofibular syndesmosis injury by using a biomechanical test. Methods A total of 24 ankle specimens from adult cadavers were used as the tibiofibular syndesmosis injury model. According to the angle of screw placement, the tibiofibular syndesmosis injury models were randomly divided into groups A (0°), B (10°-15°), C (20°-25°), and D (30°-35°), and the screws were placed at a level 2 cm proximal to the ankle joint. The displacement of fibula was measured by biomechanical testing machine at neutral, dorsiflexion (10°), plantar flexion (15°), varus (10°), and valgus (15°) positions, with axial load of 0-700 N (pressure separation test). The displacement of fibula was also measured at neutral position by applying 0-5 N·m torque load during internal and external rotation (torsional separation test). Results In the pressure separation test, group C exhibited the smallest displacement under different positions and load conditions. At neutral position, significant differences were observed (P<0.05) between group A and group C under load of 300-700 N, as well as between group B and group C under all load conditions. At dorsiflexion position, significant differences were observed (P<0.05) between group A and group C under load of 500-700 N, as well as between groups B, D and group C under all load conditions, and the displacements under all load conditions were significantly smaller in group A than in group B (P<0.05). At plantar flexion position, significant differences were observed (P<0.05) between group D and group C under all load conditions. At valgus position, significant differences were observed (P<0.05) between group A and group C under load of 400-700 N, as well as between groups B, D and group C under all load conditions. In the torsional separation test, group C exhibited the smallest displacement and group B had the largest displacement under different load conditions. During internal rotation, significant differences were observed (P<0.05) between group B and group C under all load conditions, as well as between group D and group C at load of 3-5 N·m. During external rotation, significant differences were observed between groups B, D and group C under all load conditions (P<0.05). No significant difference was detected between groups at the remaining load conditions (P>0.05). ConclusionThe ideal screw implant angle in reconstruction of tibiofibular syndesmosis injury was 20°-25°, which has a small displacement of fibula.
The present research is to investigate the time effect of sinusoidal electromagnetic fields (SEMFs) at different exposure time on the biomechanical properties in rats, and to find a best time for improving biomechanical properties. Forty female SD rats were randomly divided into five groups, i.e. control group, 45 min SEMFs group, 90 min SEMFs group, 180 min SEMFs group, and 270 min SEMFs group. In addition to the control group, other groups were exposed to 50 Hz and 0.1 mT magnetic field every day for the corresponding time periods. After eight weeks, bone mineral density (BMD), bone biomechanics, bone tissue morphology, micro-CT and pathological examination were performed. The results showed that there was no abnormal pathological finding in the experimental groups. In the 90 min SEMFs group, BMD, femur maximum load, elastic modulus, yield strength, trabecular number (Tb.N), trabecular thickness (Tb.Th) and trabecular area (Tb.Ar) percentage were all significantly higher than those in the control group (P＜0.01), and trabecular separation (Tb.Sp) was significantly lower than that of the control group (P＜0.01). However, for other experimental groups, some indices showed statistical significance compared to the control group (P＜0.05), but some did not (P>0.05). This study showed that under 50 Hz and 0.1 mT SEMFs, 90 min is the best time that can effectively increase bone mineral density, improve the bone tissue microstructure organization and the biomechanical properties.
ObjectiveTo summarize the research progress of killer turn in posterior cruciate ligament (PCL) reconstruction.MethodsThe literature related to the killer turn in PCL reconstruction in recent years was searched and summarized.ResultsThe recent studies show that the killer turn is considered to be the most critical cause of graft relaxation after PCL reconstruction. In clinic, this effect can be reduced by changing the fixation mode of bone tunnel, changing the orientation of bone tunnel, squeezing screw fixation, retaining the remnant, and grinding the bone at the exit of bone tunnel. But there is still a lack of long-term follow-up.ConclusionThere are still a lot of controversies on the improved strategies of the killer turn. More detailed basic researches focusing on biomechanics to further explore the mechanism of the reconstructed graft abrasion are needed.
ObjectiveTo develop a new type of internal fixation device which can be used to treat the minor avulsion fracture of the medial malleolus, lateral malleolus, the base of the fifth metatarsal, and the ulnar styloid process, and investigate the reliability and effectiveness of the device through biomechanical test.MethodsEighty human’s bone specimens with complete medial malleolus, lateral malleolus, the base of the fifth metatarsal, and the ulnar styloid process were selected and measured the anatomic indexes (the height, width, and thickness of medial malleolus, lateral malleolus, the base of the fifth metatarsal, and the ulnar styloid process). The CT three-dimensional reconstruction data of 200 healthy adults which including medial malleolus, lateral malleolus, the base of the fifth metatarsal, and the ulnar styloid process was also selected and measured the anatomic indexes by Mimics software. The plastic rod-hook plate was designed according to the measured results and prepared. Forty fresh porcine lower limb specimens were randomly divided into groups A and B (20 in each group), and 8 adult lower limb specimens including 4 left and 4 right were also randomly divided into groups A and B (4 in each group). All specimens were prepared for avulsion fracture of medial malleolus. Then, the fractures were fixed with plastic rod-hook plate in group A and wire anchor in group B. The load and axial torsion test of ankle joint were carried out by universal biomechanical testing machine.ResultsAccording to the anatomical characteristics, a plastic rod-hook plate was designed successfully. The biomechanical test results between animal and human specimens were consistent. There was a linear relationship between load and displacement in the ankle distal load test. The displacement when loaded to the maximum load was significantly lower in group A than in group B (P<0.05). The torsion angle and torque were significantly higher in group A than in group B when the internal fixation failed in the axial torsion test of the ankle joint (P<0.05), and the torsion angle was significantly smaller in group A than in group B when the torque was 1 N·m (P<0.05), and the maximum torque was also significantly higher in group A than in group B (P<0.05). However, there was no significant difference in torsion angle between the two groups in the maximum torque (P>0.05).ConclusionThe biomechanical properties of plastic rod-hook plate is obviously better than wire anchor, and the fixation of avulsion fracture with plastic rod-hook plate is easy to operate, which is expected to be used in the clinical treatment of minor avulsion fractures such as medial malleolus, lateral malleolus, base of the fifth metatarsal, and ulna styloid process.
