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Objective Aiming at the medial prosthetic loosening failure and lateral cartilage degeneration after unicompartmental knee arthroplasty ( UKA), the effects of prosthetic installation errors of joint line in UKA on knee contact mechanics and kinematics during different physiologic activities were studied using musculoskeletal multi-body dynamic method. Methods Taking the medial natural joint line as 0 mm error, six installation errors ofjoint line including ±2 mm, ±4 mm and ±6 mm were considered respectively, and seven musculoskeletal multi body dynamic models of medial UKA were established, to comparatively study the variations in knee contact mechanics and kinematics during walking and squatting. Results At 70% of walking gait cycle, compared with 0 mm error, the medial prosthetic contact force was increased by 127. 3% and the contact force of the lateral cartilage was decreased by 12. 0% under 2 mm elevation in joint line, the medial prosthetic contact force was close to 0 N, but the lateral cartilage contact forces were increased by 10. 1% under 4 mm reduction in joint line. The tibiofemoral total contact forces were increased by 19. 7% and decreased by 14. 2% under 2 mm elevation and 2 mm reduction in joint line, respectively. At the 100°knee flexion during squatting, compared with 0 mm error, the medial prosthetic contact force and the tibiofemoral total contact force increased by 31. 6% and 11. 1% under 2 mm elevation in joint line, and decreased by 24. 5% and 8. 5% under 2 mm reduction in joint line, respectively. The change in the lateral cartilage contact force was not marked. Moreover, at 70% of walking gait cycle, the varus angle decreased, the internal rotation and the anterior translation increased along with the elevation of joint line in UKA, while it was just the opposite along with the reduction of joint line in UKA. The trends of the varus valgus movement and anterior-posterior translation during squatting were consistent with those during swing phase of walking, but the trend of the internal-external rotation was opposite. Conclusions In order to reduce the risk of medial prosthetic loosening failure and lateral cartilage degeneration, it is recommended that the installation error of joint line in UKA should be controlled in the range of -2 mm to +2 mm. This study provides theoretical basis for UKA clinical failure caused by changes in joint line
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Objective To investigate the effects of design parameters such as neck-shaft angle, femoral offset and anteversion angle of total hip arthroplasty ( THA) prosthesis on contact forces of the hip. Methods A musculoskeletal multi-body dynamic model of THA was established based on AnyBody software. The effects of single or multiple factors on hip contact force were studied when the neck-shaft angle, eccentricity and anteversion angle varied within ±10°, ±20 mm and ±10°, respectively. Results The maximum hip contact force increased by 26. 08% when femoral offset was reduced by 20 mm. The maximum hip contact force increased by 5. 99% when the neck-shaft angle increased by 10°. When the anteversion angle increased by 10°, the hip contact force decreased at 0% -24% of gait cycle, with the peak decreasing by 19. 16% . However, the hip contact force was significantly increased at 38% -70% of gait cycle, with the peak increasing by 67. 78% . Conclusions In extramedullary design of the femoral stem, based on reconstruction of the patient’s anatomical parameters, the offset of the femoral stem can be appropriately increased, and the neck-shaft angle and anteversion angle can bereduced to avoid increasing forces on the hip.
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Objective To compare the biomechanical effects of contiguous three-level cervical Hybrid surgery[anterior cervical discectomy and fusion (ACDF) + cervical disc arthroplasty ( CDA)] and three-level ACDF. Methods The finite element model of C1-T1 cervical-thoracic spine was developed based on CT data. Three models were simulated by the implantation of Prestige LP and Zero-P prostheses, including two Hybrid models (AFA, Prestige LP implanted at C3-4 and C5-6 segments and Zero-P implanted at C4-5 segment; FAF, Zero-P implanted at C3-4 and C5-6 segments and Prestige LP implanted at C4-5 segment) and three-level ACDF model(FFF). The changes in range of motion (ROM) of adjacent levels during flexion, extension, lateral bending and axial rotation, the overall ROM, as well as the intradiscal pressure ( IDP) and facet contact force ( FCF) of adjacent levels were compared. Results The ROM in adjacent levels and the overall ROM of the AFA modelwere closer to the intact model, and the maximum increases in the ROM of the adjacent levels for the FAF and FFF models were 15. 0% and 23. 4% , respectively. For AFA, FAF and FFF models, the maximum increases in the maximum IDP of adjacent levels were 19. 0% , 66. 7% , 147. 6% , and the maximum increases in FCF were 17. 4% , 55. 7% , 80. 1% , respectively. Conclusions This study provides biomechanical basis for three-level cervical Hybrid surgery in treating patients with the contiguous three-level cervical degenerative disc disease.
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The surgical installation accuracy of the components in unicompartmental knee arthroplasty (UKA) is an important factor affecting the joint function and the implant life. Taking the ratio of the medial-lateral position of the femoral component relative to the tibial insert (a/A) as a parameter, and considering nine installation conditions of the femoral component, this study established the musculoskeletal multibody dynamics models of UKA to simulate the patients' walking gait, and investigated the influences of the medial-lateral installation positions of the femoral component in UKA on the contact force, joint motion and ligament force of the knee joint. The results showed that, with the increase of a/A ratio, the medial contact force of the UKA implant was decreased and the lateral contact force of the cartilage was increased; the varus rotation, external rotation and posterior translation of the knee joint were increased; and the anterior cruciate ligament force, posterior cruciate ligament force and medial collateral ligament force were decreased. The medial-lateral installation positions of the femoral component in UKA had little effect on knee flexion-extension movement and lateral collateral ligament force. When the a/A ratio was less than or equalled to 0.375, the femoral component collided with the tibia. In order to prevent the overload on the medial implant and lateral cartilage, the excessive ligament force, and the collision between the femoral component and the tibia, it is suggested that the a/A ratio should be controlled within the range of 0.427-0.688 when the femoral component is installed in UKA. This study provides a reference for the accurate installation of the femoral component in UKA.
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Humans , Arthroplasty, Replacement, Knee , Knee Joint/surgery , Knee Prosthesis , Gait , RotationABSTRACT
Objective To investigate changes in gait level of patients after hip replacement, the variation trend of bone mineral density (BMD) around the prothesis was studied, so as to reveal the influence pattern of gait level at postoperative initial and long-term stages on bone reomodeling. Methods Based on adaptive bone remodeling theory, the finite element model of femer-prosthesis was developed. The BMD distribution was calculated using the initial and long-term gait level after hip replacement as the remodeling parameters. Gruen method was applied to quantify the BMD changes. Results At the postoperative initial stage, obvious variations existed in constant gait group and changing gait group. The maximum difference occurred in low gait group, resulting in the decrease of BMD by 41% in greater trochanter region. The improvement of gait level would promote the enhancement of BMD in proximal and middle region of the prosthesis, resulting in the increase of BMD by 47%. Long-term gait recovery would promote BMD recovery in middle and end region of prosthesis, with BMD increase by 2%-9%. Conclusions The research findings provide guidance for rehabilitation process of patients after hip replacement.
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A micro silicone oil liquid spring was designed and manufactured in this article. The performance of the liquid spring was studied by simulation analysis and mechanical test. A self-force source power-assisted knee orthosis was designed based on the liquid spring. This power-assisted knee orthosis can convert the kinetic energy of knee flexion into the elastic potential energy of liquid spring for storage, and release elastic potential energy to generate assisted torque which drives the knee joint for extension. The results showed that the average maximum reset force of the liquid spring was 1 240 N, and the average maximum assisted torque for the knee joint was 29.8 N·m. A musculoskeletal multibody dynamic model was used to analyze the biomechanical effect of the knee orthosis on the joint during knee bending (90°knee flexion). The results showed that the power-assisted knee orthosis could effectively reduce the biomechanical load of the knee joint for the user with a body weight of 80 kg. The maximum forces of the femoral-tibial joint force, patellar-femoral joint force, and quadriceps-ligament force were reduced by 24.5%, 23.8%, and 21.2%, respectively. The power-assisted knee orthosis designed in this article provides sufficient assisted torque for the knee joint. It lays a foundation for the subsequent commercial application due to its small size and lightweight.
Subject(s)
Biomechanical Phenomena , Knee Joint , Femur , Ligaments , Orthotic DevicesABSTRACT
The simulator testing in vitro and computational simulation of the artificial knee joint wear are important methods to evaluate the wear performance of the prosthesis in vitro and to predict the clinical performance of knee joint products. Based on the method of literature search, this paper compares the mechanical and kinematic loading input curves carried out by Chinese scholars in recent years, standard curves, and Chinese measurement curves of two typical movements of gait. Data of vitro simulator test and computational simulation model are compared, summarized, and analyzed. The results show that the measured data of motion and load cannot be directly used as the loading conditions for the simulator wear test and computational simulation. The mechanics and kinematics data of Chinese people are different from the international standards. The domestic artificial knee joint in vitro simulator wear test methods are similar but the results of different test institutions are somewhat different. The computation wear prediction research is basically synchronized with foreign countries, but the problem that the calculated wear results are lower than that in vitro test is still unsolved. The artificial knee joint wear performance evaluation system based on Chinese knee joint mechanics and kinematics data is the forward direction of the research.
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Osteoarthritis are usual disease in middle aged and elderly people. High tibial osteotomy is a common method which performed to treat medial compartment osteoarthritis in varus knees. Unicondylar knee arthroplasty is an established treatment option for symptomatic osteoarthritis isolated to one compartment, and received remarkably effect. Total knee arthroplasty is the standard treatment of serious knee disease. The knee kinematics have changed after the knee was diseased, and the kinematics after surgery are different from the natural joint. The flexion-extension rotation, anterior-posterior translation and interior-exterior rotation are most important kinematics of tibia-femur joint. The anterior-posterior translation and interior-exterior rotation, which as the secondary kinematics, even are paradoxical after total knee arthroplasty. Secondary kinematics studies played an important role in prosthesis design and postoperative functional assessment. Measurement and description methods of knee joint secondary kinematics were reviewed in this article. The factors influencing secondary kinematics were investigated for natural knee joint, osteoarthritis knee joint and knee joint after total knee replacement separately, and the influence of total knee replacement design was emphasized. At last, the impact of knee secondary kinematics to biomechanics, friction and wear were also introduced. After comparison of multi-research results, the measurement precision was found to need further improvement due to the restrict of measuring technology and description methods. Many factors influence knee secondary kinematics, including activities, measurement environment and individual difference. The anterior-posterior translation was found complex after total knee replacement, and the prosthesis design played an important role. Posterior cruciate ligament-retaining knee replacement lead forward slide of the femoral component during flexion, which paradoxical from natural knee. The anatomical design prosthesis were hopeful to realize more natural kinematics. The component malalignment and soft tissue balance during surgey also have significant role in knee secondary kinematics. The knee secondary kinematics study is of great significance to biomechanics and wear.
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Objective To investigate the biomechanical effects of femoral offset (FO) on total hip arthroplasty (THA) patients with developmental dysplasia of the hip (DDH). Methods Based on the musculoskeletal dynamic software AnyBody and the related data from a female patient with Crowe Ⅳ DDH, the corresponding patient-specific lower extremity musculoskeletal multi-body dynamic model was constructed to analyze both hip joint forces and abductor forces within ±20 mm variation of FOs. The dynamic finite element (FE) model of S-ROM stem with varying offsets was also established. The dynamic load during a whole walking gait cycle calculated by the multi-body musculoskeletal model was applied to this FE models, and the Von Mises stress, contact stress, and stem-sleeve micromotion were then analyzed. Results A variation of ±20 mm offset had small influences on peak forces of hip joints. However, the decrease in FO could lead to an obvious increase in peak abductor force, while the increase in FO could lead to an obvious increase in the maximum Von Mises stress, contact stress, and micromotion of S-ROM prosthesis stem. Conclusions The change in FO had an obvious influence on the abductor forces, the maximum Von Mises stress, the contact pressure and the consequent fretting wear of THA patients with DDH, which should be carefully considered by surgeons.
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Objective To establish the musculoskeletal multi-body dynamic foot-ground contact model and explore its applicability at different speed. Methods The gait data of the subjects at different speed were collected, and the foot-ground contact model was established based on the full body model from the musculoskeletal multibody dynamic software AnyBody. Then the calculated ground reaction forces (GRFs) and ground reaction moments (GRMs) at different speed (slow walking, normal walking, fast walking and jogging) were compared with the measurements from the force plates. Results The predicted GRFs and GRMs correlated well with the experimental measurements at slow, normal and fast speed (stride speed ranged from 0.69 to 1.68 m/s). The correlation coefficients between predicted and measured GRFs were greater than 0.875 and the correlation coefficients for GRMs were greater than 0.9. Conclusions The developed foot-ground contact model could simultaneously predict GRFs and GRMs with good accuracy, thus eliminating the dependency on force plates. The model could be applied to low-speed gait conditions, such as the elderly and pathological gait.
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Osteoarthritis are usual disease in middle aged and elderly people. High tibial osteotomy is a common method which performed to treat medial compartment osteoarthritis in varus knees. Unicondylar knee arthroplasty is an established treat?ment option for symptomatic osteoarthritis isolated to one compartment, and received remarkably effect. Total knee arthroplasty is the standard treatment of serious knee disease. The knee kinematics have changed after the knee was diseased, and the kinematics after surgery are different from the natural joint. The flexion?extension rotation, anterior?posterior translation and interior?exterior rotation are most important kinematics of tibia?femur joint. The anterior?posterior translation and interior?exterior rotation, which as the secondary kinematics, even are paradoxical after total knee arthroplasty. Secondary kinematics studies played an important role in prosthesis design and postoperative functional assessment. Measurement and description methods of knee joint secondary kinematics were reviewed in this article. The factors influencing secondary kinematics were investigated for natural knee joint, os?teoarthritis knee joint and knee joint after total knee replacement separately, and the influence of total knee replacement design was emphasized. At last, the impact of knee secondary kinematics to biomechanics, friction and wear were also introduced. After comparison of multi?research results, the measurement precision was found to need further improvement due to the restrict of mea?suring technology and description methods. Many factors influence knee secondary kinematics, including activities, measurement environment and individual difference. The anterior?posterior translation was found complex after total knee replacement, and the prosthesis design played an important role. Posterior cruciate ligament?retaining knee replacement lead forward slide of the femo?ral component during flexion, which paradoxical from natural knee. The anatomical design prosthesis were hopeful to realize more natural kinematics. The component malalignment and soft tissue balance during surgey also have significant role in knee second?ary kinematics. The knee secondary kinematics study is of great significance to biomechanics and wear.
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Objective To investigate the feasibility and primary clinical outcomes of a kind of independent research and development customized 3D printed external fixator in the treatment of tibial fracture.Methods Data of 7 tibial fracture patients who were treated using computer-assisted reduction and 3D printing technique including a new kind of customized external fixator with automatical reduction function from December 2013 to November 2015 were retrospectively analyzed.There were 5 males and 2 females in this cohort.The age of the patients ranged from 25 to 49 years old,with an average age of 38.1 years old.The procedure was as follows.At first,two or three pins were placed separately into the distal and proximal tibia away from fracture site.Then,the CT scanning was performed on the fractured tibia.According to the CT scanning data,the external fixator was designed by computer software and manufactured by the 3D printing technique.The reduction of tibial fracture was achieved automatically after the 3D printed external fixator was connected to the inserted pins.Finally,the accuracy of reduction was assessed by postoperative X-ray image.During the different fracture healing course,the stress environment could be dynamically adjusted by screwing or unscrewing the nuts to fulfill rigid fixation,compression fixation or elastic fixation for the bone healing.Results All the 7 cases had obtained successful reduction by only one time operation with the 3D printed external fixators.The average lateral angulation was 1.42°± 1.13°,and the average anteroposterior angulation was 1.65°± 1.36°,while the average lateral displacement was 1.38± 1.44 mm,and the average anteroposterior displacement was 1.83± 1.30 mm,which were measured from postoperative X-ray image.The individual durations of the operation were 9 min,8 min,9 min,1.5 min,1.4 min,1.4 min and 2.4 min,respectively.All fractures had achieved bony union in 19-25 weeks after operation,with an average time of 21.4±1.6 weeks.All patients were followed up for 6 months when removal of the external fixator,and no refracture occurred.Conclusion The customized 3D printed external fixator has the function of automatical reduction.In addition,it can provide three kinds of fixation modes,which are rigid fixation,compression fixation and elastic fixation.It has the advantages of simple operation,accurate reduction,reasonable fixation,etc.
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Aiming at comparing the pre-operative and post-operative gait characteristics and therefore establishing post-operative rehabilitation guidance for patients with end-stage knee osteoarthritis (KOA) merged with varus deformity, this study captured the level walking and sit-to-stand trials of 9 patients with 3-dimensional motion analysis system and after which musculoskeletal multi-body dynamic analysis was conducted. The study indicated that the average range of motion (ROM) of the proposed-surgical knee was 24.4°-57.6° and that of the non-surgical knee was 22.5°-71.5°. The knee ROM of control group during level walking was 7.2°-62.4°. When the unilateral KOA patients stood up from chair to complete the sit-to-stand movement, the ground reaction forces (GRFs) symmetry was 0.72-0.85, which means that the non-surgical limb bear the majority of body weight. The GRFs of the bilateral KOA patients were smallest during the sit-to-stand movement. The strategy that the non-surgical limb dominates in loading bearing taken by the unilateral KOA patients to cover most post-operative daily activities could increase the risk of KOA among non-surgical side joints as a result of long-term excessive loading-bearing. The study, on kinematics and biomechanical characteristics of patients with KOA merged with varus deformity, could help to understand the pathogenesis of KOA merged with varus deformity from the perspective of biomechanics and to provide strong clinic guidance for the pre-operative evaluation, prevention and post-operative recovery for patients.
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BACKGROUND:In recent years, many manufacturing techniques have been recently developed for soft tissue engineering scaffolds. Especialy additive manufacturing with a unique material accumulated forming principle can be feasible and reliable to manufacture the highly precise scaffolds with gradient structures and multi-materials for large soft tissue defect repairing. OBJECTIVE:To summarize scaffolds manufacturing technologies in the soft tissue engineering applications developed in recent years and to predict the direction of development. METHODS: A retrieval was performed for the literature about the manufacturing methods of soft tissue scaffolds using key words of “additive manufacturing, microfabrication, vascular tissue engineering, muscle tissue engineering, cartilage tissue engineering, stereolithography, 3D printing, biodegradable hydrogel” in English and Chinese, which were published between January 2010 and September 2013 in PubMed Database and China National Knowledge Infrastructure (CNKI) Database. RESULTS AND CONCLUSION:For large soft tissue defects repairing, structure design of the scaffolds has been shifted from a simple planar structure to a more complex three-dimensional structure, and integration of scaffold structure, materials and cels, and growth factors during the manufacturing procedure can be used to obtain the resolution of vascularization. Additive manufacturings become one of the most promising approaches for the ideal soft tissue scaffolds with gradient and complex structure and multi-materials. In particular, the hydrogel/cellcomposite scaffolds fabrication, a hot but promising approach to develop the soft tissue engineering wil be made progress by the accurate principles and processes of the hydrogel additive manufacturing combined with the introduction of living cels and growth factors.
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ObjectiveTo assess left ventricular twist and untwist in rabbit models with diastolic heart failure(DHF) and systolic heart failure(SHF) by speckle tracking imaging(STI).Methods Thirtythree male New Zealand rabbits were divided into three groups:one group was used to establish DHF model by suprarenal abdominal aortic constriction(n = 12) and the other was used to establish SHF model by abdominal aortic constriction subdiaphragmly above celiac artery origin(n = 11),another was control group established by sham operation(n = 10).After two weeks,left ventricular twist-related parameters were measured.by STE.Finallly,left ventricular catheterization and myocardial pathological examination were performed.Results Compared with control group,peak twist angle (Ptw) and peak twisting velocity(PTV)remained unchanged in DHF group (P ＞ 0.05) and decreased in SHF group (P ＜ 0.05).Isovolumic untwisting rate (IUR) decreased,untwisting half-time(UHT) was prolonged,time to peak twist (tPtw) and peak untwisting velocity (tPUTV) were delayed in SHF and DHF groups.In additon,Peak untwisting velocity(PUTV) decreased in SHF group,but increased in DHF group (P ＜0.05).Ptw correlated correlated positively with LVEF,+ dp/dtmax significantly in both groups (DHF group:r = 0.897,P =0.002; r = 0.719,P = 0.044;SHF group:r = 0.727,P = 0.041; r = 0.780,P = 0.022).A significantly positive correlation was observed between PUTV and - dp/dtmax Tau,LVEDP(r = 0.801,P = 0.017; r =0.814,P = 0.014; r = 0.875,P = 0.004) in SHF group.Conclusions STI is useful in evaluating left ventricular twist and untwist in rabbit model of DHF and SHF.