ObjectiveTo compare the strength difference between the interfacial screw and the interfacial screw combined with bone tunnel crossing technology to fix the tibial end of ligament during anterior cruciate ligament (ACL) reconstruction through the biomechanical test.MethodsTwenty fresh frozen pig tibia were randomly divided into two groups (n=10) to prepare ACL reconstruction models. The graft tendons in the experimental group were fixed with interfacial screw combined with bone tunnel crossing technology, and the graft tendons in the control group were fixed with interfacial screw. The two groups of specimens were fixed in the high-frequency dynamic mechanics test system M-3000, and the length change (displacement), ultimate load, and stiffness of graft tendons were measured through the reciprocating test and load-failure test.ResultsThe results of reciprocating test showed that the displacement of the experimental group was (3.06±0.58) mm, and that of the control group was (2.82±0.46) mm, and there was no significant difference between the two groups (t=0.641, P=0.529). The load-failure test results showed that the stiffness of the experimental group and the control group were (95.39±13.63) and (91.38±14.28) N/mm, respectively, with no significant difference (t=1.021, P=0.321). The ultimate load of the experimental group was (743.15±173.96) N, which was significantly higher than that of the control group (574.70±74.43) N (t=2.648, P=0.016).ConclusionIn ACL reconstruction, the fixation strength of tibial end with interface screw combined with bone tunnel crossing technology is obviously better than that of interface screw alone.
Objective To analyze the relationship between the collateral ligament attachment and the epicondylar axis with rotational alignment of the femoral component in the total knee arthroplasty(TKA).Methods Twenty normal cadaver knee joints were anatomized and 2 holes were drilled on the distal femur from the deep and superficial insertions of the medial collateral ligaments to the lateral condylar part, respectively. Then, all the knees were scanned by MRI on the sagittal plane, making the drilled hole located relatively to the posterior condylar joint surface on the axial plane, and the posterior condylar angle (PCA) and thecondylar twist angle (CTA) were measured.Results The colateral ligament had the deep and superficial parts, and the deep part was strained during the knee flexing. PCA and CTA were 4.50±1.26° and 7.10±0.30° respectively, and there was a significant difference between them(P＜0.05), which were significantly greater than those reported abroad. On the sagittal plane, there wasno significant difference between the radiuses of the posterior medial and lateral condylar circles (Pgt;0.05). The distance from the center of the posterior condylar circle to the deep insertion of the medial collateral ligament (MCL) (d1) was 4.22±0.20 mm, and the distance to the superficial insertionof MCL (d2) was 7.36±0.13 mm. The difference between d1 and d2 was significant(Plt;0.05). Conclusion The center of the posterior condylar circle passes from the deep insertion of the collateral ligament, which can be regarded as a fixed flexionextension axis of the knee. By releasing the different parts of the collateral ligaments, the balance of the flexion and extension gap canbe obtained, and then varus, valgus or flexed contracture deformity of the kneecan be realigned. Besides, the rotational orientation of the femoral prothesis can be made by a reference to the epicondylar insertion of the collateral ligament.
This article reviews the progress of biomechanical studies on anterior cervical fusion and nonfusion surgery in recent years. The similarities and differences between animal and human cervical spines as well as the major three biomechanical test methods are introduced. Major progresses of biomechanical evaluation in anterior cervical fusion and nonfusion devices, hybrid surgery, coupled motion and biomechanical parameters, such as the instant center of rotation, are classified and summarized. Future development of loading method, multilevel hybrid surgery and coupling character are also discussed.
A comprehensive, geometrically accurate, nonlinear C0-T1 three-dimensional finite element (FE) model was developed for the biomechanical study of human cervical spine and related disorders. The model was developed with anatomic detail from the computed tomography (CT) images of a 46-year old female healthy volunteer, and applied the finite element model processing softwares such as MIMICS13.1, Hypermesh11.0, Abaqus 6.12-1, etc., for developing, preprocessing, calculating and analysing sequentially. The stress concentration region and the range of motion (ROM) of each vertebral level under axial rotation, flexion, extension, and lateral bending under physiologic static loadings were observed and recorded. The model was proven reliable, which was validated with the range of motion in previous published literatures. The model predicted the front and side parts of the foramen magnum and contralateral pedicle and facet was the stress concentration region under physiological loads of the upper spine and the lower spine, respectively. The development of this comprehensive, geometrically accurate, nonlinear cervical spine FE model could provide an ideal platform for theoretical biomechanical study of human cervical spine and related disorders.
ObjectiveTo clarify the value of the cortical endo-button as an internal fixator in Latarjet procedure through biomechanical analysis.MethodsTen pairs of shoulder joints from 6-7 months old male pigs were selected. Each pair was randomly divided into screw group and endo-button group. A 25% glenoid defect model was created, and the porcine infraspinatus tendon and its associated bone were used to simulate conjoint tendon and coracoid process in human body. The bone grafts were fixed with two 3.5 mm screws and double cortical endo-buttons with high-strength sutures in screw group and endo-button group, respectively. The prepared glenoid defect model was fixed on a biomechanical test bench and optical markers were fixed on the glenoid and the bone block, respectively. Then fatigue test was performed to observe whether the graft or internal fixator would failed. During the test, the standard deviations of the relative displacement between the graft and the glenoid of two groups were measured by optical motion measure system for comparison. Finally the maximum failure load comparison was conducted and the maximum failure loads of the two groups were measured and compared.ResultsThere was no tendon tear, bone fracture, and other graft or internal fixation failure in the two groups during the fatigue test. The standard deviation of the relative displacement of the screw group was (0.007 87±0.001 44) mm, and that of the endo-button group was (0.034 88±0.011 10) mm, showing significant difference between the two groups (t=7.682, P=0.000). The maximum failure load was (265±39) N in screw group and (275±52) N in endo-button group, showing no significant difference between the two groups (t=1.386, P=0.199). There were 3 ways of failure: rupture at bone graft’s tunnel (6/10 from screw group, 3/10 from endo-button group), tendon tear at the cramp (2/10 from screw group, 2/10 from endo-button group), and tendon tear at the internal fixator interface (2/10 from screw group, 5/10 from endo-button group), showing no significant difference between the two groups (P=0.395).ConclusionAlthough the endo-button fixation fails to achieve the same strong fixation stability as the screw fixation, its fixation stability can achieve the clinical requirements. The two fixation methods can provide similar fixation strength when being used in Latarjet procedure.
ObjectiveTo review the research progress on the lower limb biomechanical characteristics of patients with discoid lateral meniscus (DLM) injury after surgery. MethodsBy searching relevant domestic and international research literature on DLM, the postoperative characteristics of knee joint movement biomechanics, tibiofemoral joint stress distribution, lower extremity force line, and patellofemoral joint changes in patients with DLM injury were summarized. ResultsSurgical treatment can lead to varying degrees of changes in the lower limb biomechanical characteristics of patients with DLM injury. Specifically, the kinematic biomechanics of the knee joint can significantly improve, but there are still problems such as extension deficits in the affected knee joint. The peak stress of the tibiofemoral joint decreases with the increase of the residual meniscus volume, and the degree of change is closely related to the residual meniscus volume. Preserving a larger volume of the meniscus, especially the anterior horn volume, helps to reduce stress concentration. The lower extremity force line will deviate outward after surgery, and the more meniscus is removed during surgery, the greater the change in the lower extremity force line after surgery. There are conditions such as cartilage degeneration, position and angle changes in the patellofemoral joint after surgery. ConclusionThe changes in the lower limb biomechanical characteristics after DLM injury are closely related to the choice of surgical methods and rehabilitation programs. However, the mechanisms of biomechanical changes in multiple lower limb joints and individual differences still need to be further studied and clarified.
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.
A three-dimensional finite element model of premaxillary bone and anterior teeth was established with ANSYS 13.0. The anterior teeth were fixed with strong stainless labial archwire and lingual frame. In the horizontal loading experiments, a horizontal retraction force of 1.5 N was applied bilaterally to the segment through hooks at the same height between 7 and 21 mm from the incisal edge of central incisor; in vertical loading experiments, a vertical intrusion force of 1.5 N was applied at the midline of lingual frame with distance between 4 and 16 mm from the incisal edge of central incisor. After loading, solution was done and displacement and maximum principle stress were calculated. After horizontal loading, lingual displacement and stress in periodontal membrane (PDM) was most homogeneous when the traction force was 14 mm from the edge of central incisor; after vertical loading, intrusive displacement and stress in PDM were most homogeneous when the traction force was 12 mm from the incisal edge of central incisor. The results of this study suggested that the location of center of resistance (CRe) of six maxillary anterior teeth is about 14 mm gingivally and 12 mm lingually to incisal edge of central incisor. The location can provide evidence for theoretical and clinical study in orthodontics.
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.
Objective To design customized titanium alloy lunate prosthesis, construct three-dimensional finite element model of wrist joint before and after replacement by finite element analysis, and observe the biomechanical changes of wrist joint after replacement, providing biomechanical basis for clinical application of prosthesis. Methods One fresh frozen human forearm was collected, and the maximum range of motions in flexion, extension, ulnar deviation, and radialis deviation tested by cortex motion capture system were 48.42°, 38.04°, 35.68°, and 26.41°, respectively. The wrist joint data was obtained by CT scan and imported into Mimics21.0 software and Magics21.0 software to construct a wrist joint three-dimensional model and design customized titanium alloy lunate prosthesis. Then Geomagic Studio 2017 software and Solidworks 2017 software were used to construct the three-dimensional finite element models of a normal wrist joint (normal model) and a wrist joint with lunate prosthesis after replacement (replacement model). The stress distribution and deformation of the wrist joint before and after replacement were analyzed for flexion at and 15°, 30°, 48.42°, extension at 15°, 30°, and 38.04°, ulnar deviation at 10°, 20°, and 35.68°, and radial deviation at 5°, 15°, and 26.41° by the ANSYS 17.0 finite element analysis software. And the stress distribution of lunate bone and lunate prosthesis were also observed. Results The three-dimensional finite element models of wrist joint before and after replacement were successfully constructed. At different range of motion of flexion, extension, ulnar deviation, and radial deviation, there were some differences in the number of nodes and units in the grid models. In the four directions of flexion, extension, ulnar deviation, and radial deviation, the maximum deformation of wrist joint in normal model and replacement model occurred in the radial side, and the values increased gradually with the increase of the range of motion. The maximum stress of the wrist joint increased gradually with the increase of the range of motion, and at maximum range of motion, the stress was concentrated on the proximal radius, showing an overall trend of moving from the radial wrist to the proximal radius. The maximum stress of normal lunate bone increased gradually with the increase of range of motion in different directions, and the stress position also changed. The maximum stress of lunate prosthesis was concentrated on the ulnar side of the prosthesis, which increased gradually with the increase of the range of motion in flexion, and decreased gradually with the increase of the range of motion in extension, ulnar deviation, and radialis deviation. The stress on prosthesis increased significantly when compared with that on normal lunate bone. Conclusion The customized titanium alloy lunate prosthesis does not change the wrist joint load transfer mode, which provided data support for the clinical application of the prosthesis.