Relationship between kinematic gait parameters during three gait modifications designed to reduce peak knee abduction moment

PurposeGait modifications designed to change a single kinematic parameter have reduced first peak internal knee abduction moment (PKAM). Prior research suggests unintended temporospatial and kinematic changes occur naturally while performing these modifications. We aimed to investigate i) the concomitant kinematic and temporospatial changes and ii) the relationship between gait parameters during three gait modifications (toe-in, medial knee thrust, and trunk lean gait).MethodsUsing visual real-time biofeedback, we collected 10 trials for each modification using individualized target gait parameters based on participants’ baseline mean and standard deviation. Repeated measures ANOVA was performed to determine significant differences between conditions. Mixed effects linear regression models were then used to estimate the linear relationships among variables during each gait modification. All modifications reduced KAM by at least 5%.ResultsModifications resulted in numerous secondary changes between conditions such as increased knee abduction during toe-in gait and increased knee flexion with medial knee thrust. Within gait modifications, relationships between kinematic parameters were similar for toe-in gait and medial knee thrust (i.e. increased toe-in and decreased knee abduction), while increased trunk lean showed no relationship with any other kinematic parameters during trunk lean trials.ConclusionTwo main mechanisms were found as a result of this investigation; the first being a pattern of toeing-in, knee abduction, flexion, and internal hip rotation, while trunk lean modification presented as a separate gait pattern with limited secondary changes. Future studies should consider providing feedback on multiple linked parameters, as it may feel more natural and optimize KAM reductions.     

Analysis of the factors that correlate with increased knee adduction moment during gait in the early postoperative period following total knee arthroplasty

Background

Analysis of dynamic knee loading during gait is essential to prevent mechanical failures following total knee arthroplasty. External knee adduction moment during gait is the primary factor producing medial joint reaction force, and an increase in the moment is directly related to an increase in the medial compartment load on the knee.

Assessments of loads in the knee joint

A method of gait analysis was used to estimate the loads in the knee joint. An analysis was made of the repeatability of the measurements for a group of 72 patients. Data from 418 patients were reviewed to show the variation with coronal angle of the knee of the loading.     

膝屈伸肌群等速肌力训练改善膝骨性关节炎患者步态的效果分析

目的探讨膝屈伸肌群等速肌力训练改善膝骨性关节炎(KOA)患者步态的效果。方法采用前瞻性研究方法,为保证研究的安全性和科学性,选择2013年2月~2015年10月在我院诊治的KOA患者98例,根据入院顺序分为观察组与对照组各49例,两组都给予玻璃酸钠关节腔内注射和关节松动治疗,对照组给予积极康复训练,观察组给予膝屈伸肌群等速肌力训练,治疗观察时间都为4周。结果观察组与对照组的疗效优良率分别为93.9%和75.5%,观察组明显高于对照组(0.05)。治疗后观察组与对照组的Lysholm膝关节功能评分分别为(86.33±11.31)分和(75.84±10.71)分,都明显高于治疗前的(56.24±12.55)分和(56.24±11.12)分,组内与组间对比差异都有统计学意义(0.05)。观察组治疗后的屈肌PT与AOPT值分别为(21.87±3.67)N·m和(99.23±11.48)°,而对照组分别为(18.34±4.11)N·m和(89.02±10.45)°,都明显高于治疗前(0.05),且组间对比差异有统计学意义(0.05)。两组在治疗期间都无严重并发症,但观察组的恶心、呕吐、腹痛、腹胀等并发症发生率明显少于对照组(0.05)。结论膝屈伸肌群等速肌力训练在KOA患者中的应用能显著缓解疼痛、增强膝关节功能,具有很好的安全性,从而促进步态改善,具有重要的推广价值。     

A three dimensional approach for quantifying resultant loading at the knee

Background

Clinical effectiveness of lateral wedges for knee osteoarthritis is inconsistent across studies. One explanation is that knee loading is not fully described by the peak frontal-plane knee moment. The purpose of this study was to propose a 3D resultant approach to describing moments at the knee and evaluate how this moment changes in response to lateral wedges.

Changes in gastrocnemii activation at mid-to-late stance markedly affects the intact and anterior cruciate ligament deficient knee biomechanics and stability in gait

IntroductionWe aimed to quantify the sensitivity in biomechanical response and stability of the intact and anterior cruciate ligament deficient (ACL-D) joints at mid-to-late stance periods of gait to the alterations in activation of gastrocnemii (Gas) muscles.MethodsA validated kinematics-driven musculoskeletal finite-element model of the lower extremity is used to compute knee joint response and stability under reported kinetics–kinematics of healthy subjects. Activation in Gas is altered under prescribed gait data at the mid-to-late stance of gait and associated changes in remaining muscle forces/contact forces/areas/ACL force and joint stability are computed in both intact and ACL-D joints.ResultsIn the intact joint, the anterior-tibial-translation (ATT) as well as ACL and joint contact forces follow variations in Gas forces. Both the stability and ATT of an ACL-D joint are restored to the near-intact levels when the activity in Gas is reduced. Knee joint instability, excessive ATT as well as larger peak articular contact stresses with a posterior shift in contact areas are estimated under greater Gas forces.ConclusionsACL-D joint is unstable with ATT > 10 mm under larger activities in Gas. Gas is an ACL-antagonist while hamstrings and soleus are ACL-agonists. The near-intact joint stability and ATT of an ACL-D joint can be restored at a lower activation in Gas; or in other words, when activation in ACL-antagonist muscles drops compared with that in ACL-agonist muscles. Results could help analyze the gait of ACL-D copers and non-copers and provide better understanding towards improved preventive, diagnostic, and treatment approaches.     

A mathematical modelling study investigating the influence of knee joint flexion angle and extension moment on patellofemoral joint reaction force and stress

BackgroundPatellofemoral pain (PFP) is the most common orthopaedic condition among runners. Individuals with PFP exhibit greater patellofemoral joint (PFJ) reaction force and stress when compared with pain-free controls. However, it is not clear whether PFJ reaction force and stress are the highest (or lowest) when knee joint flexion angle and extension moment are in which combinations. We aimed to investigate the influence of knee joint flexion angle and extension moment on PFJ reaction force and stress.MethodsA PFJ sagittal model was used to quantify PFJ reaction force and stress. Based on the public dataset of the previous study, peak knee joint flexion angle and extension moment at various running speeds was calculated. Based on the calculated peak value, simulation ranges were set to knee joint flexion angle of 10–45° and extension moment of 0–240 Nm. The quadriceps force, effective lever arm length at quadriceps muscle, and PFJ contact area were determined as a function of the knee joint flexion angle and extension moment, and finally PFJ forces and stress were estimated.ResultsPFJ reaction force increased as the knee flexion angle and extension moment increased. Although PFJ stress also increased as the knee extension moment increased, it was at the highest and lowest at 10° and about 30° knee joint flexion angles, respectively.ConclusionsIncorporating knee flexion posture (approximately 30°) during running may help in reducing PFJ stress, which would be useful in the prevention of pain and act as an optimal treatment program for PFP.     

Gender differences in the restoration of knee joint biomechanics during gait after anterior cruciate ligament reconstruction

Background

The aim of our study was to evaluate the effects of gender on recovery of knee joint biomechanics over the stance phase of gait after reconstruction of the anterior cruciate ligament (ACL).

新型国产膝关节假体用于全膝关节置换术的临床研究

目的 通过随机对照临床试验,验证新型国产膝关节假体临床应用的安全性和有效性.方法 本研究采用多中心、随机、单盲、阳性平行对照设计,自2017年3月至2019年3月在全国6家医院共招募72例受试者,试验组和对照组各36例.试验组使用新型国产膝关节假体,对照组使用成熟的膝关节假体.所有受试者在术前和术后3个月、6个月、1年...     

Application of an artificial neural network to the control of an active external orthosis of the lower limb

The object of this paper is to present a real-time application of an artificial neural network (ANN). The application for which this network is demonstrated is a motorised orthosis with six degrees-of-freedom for use by a paraplegic; a ‘walking machine’. Theoretical networks and training methods need modification to function correctly with a real application. Several complex phenomena that are very diffucult to model have to be accommodated; the starting threshold of the activators, nonlinearity, noise, and the non-biunivocity between successive system states (position, velocity, actuator controls). The modifications made to the network and the associated training method partially alleviate these difficulties.     

A 2D approach to tomographic image reconstruction using a Hopfield-type neural network

OBJECTIVE: In this paper a new approach to tomographic image reconstruction from projections is developed and investigated. METHOD: To solve the reconstruction problem a special neural network which resembles a Hopfield net is proposed. The reconstruction process is performed during the minimizing of the energy function in this network. To improve the performance of the reconstruction process an entropy term is incorporated into energy expression. RESULT AND CONCLUSION: The approach presented in this paper significantly decreases the complexity of the reconstruction problem.     

Biomechanics of the knee joint in flexion under various quadriceps forces

Bioemchanics of the entire knee joint including tibiofemoral and patellofemoral joints were investigated at different flexion angles (0° to 90°) and quadriceps forces (3, 137, and 411 N). In particular, the effect of changes in location and magnitude of restraining force that counterbalances the isometric extensor moment on predictions was investigated. The model consisted of three bony structures and their articular cartilage layers, menisci, principal ligaments, patellar tendon, and quadriceps muscle. Quadriceps forces significantly increased the anterior cruciate ligament, patellar tendon, and contact forces/areas as well as the joint resistant moment. Joint flexion, however, substantially diminished them all with the exception of the patellofemoral contact force/area that markedly increased in flexion. When resisting extensor moment by a force applied on the tibia, the force in cruciate ligaments and tibial translation significantly altered as a function of magnitude and location of the restraining force. Quadriceps activation generated large ACL forces at full extension suggesting that post ACL reconstruction exercises should avoid large quadriceps exertions at near full extension angles. In isometric extension exercises against a force on the tibia, larger restraining force and its more proximal location to the joint substantially decreased forces in the anterior cruciate ligament at small flexion angles whereas they significantly increased forces in the posterior cruciate ligament at larger flexion angles.     

Effect of functional weightbearing versus non-weightbearing quadriceps strengthening exercise on contact force in varus-malaligned medial knee osteoarthritis: A secondary analysis of a randomized controlled trial

BackgroundKnee osteoarthritis progression may be related to altered knee loads, particularly in those with varus malalignment. Using randomized controlled trial data, this secondary analysis of complete datasets (n = 67) compared the effects of a functional weightbearing (WB) and non-weightbearing quadriceps strengthening exercise (NWB) program on measures of medial tibiofemoral joint contact force (MTCF) during walking.MethodsParticipants aged ≥50 years and with medial knee osteoarthritis and varus malalignment were randomly allocated to a 12-week, home-based, physiotherapist-prescribed exercise program comprised of WB exercises (n = 31), or NWB exercise (n = 36). Three-dimensional lower-body motion, ground reaction forces, and surface electromyograms from six lower-limb muscles were acquired during walking at baseline and at 12-weeks follow-up. An electromyogram-informed neuromusculoskeletal model estimated bodyweight (BW) normalized MTCF (peak and impulse), including external and muscular contributions to MTCF.ResultsThere was no between-group difference in the change in peak MTCF (−0.02 [−0.12, 0.09] BW) or MTCF impulse (−0.01 [−0.06, 0.03] BW·s). There was a between-group difference in the muscle contribution to peak MTCF (−0.08 [−0.15, −0.00] BW) and MTCF impulse (−0.04 [−0.08, −0.00] BW·s), whereby the muscle contribution reduced more in the NWB group over time compared to the WB group. There was also a between group-difference in the external contribution to peak MTCF (0.09 [0.01, 0.18] BW), but this reduced more in the WB group than in the NWB group.ConclusionsOur findings suggest no difference in MTCF between the two exercise programs, but differences in the contribution to MTCF between the two exercise programs were observed in those with medial knee osteoarthritis and varus malalignment.     

No associations between self-reported knee joint instability and radiographic features in knee osteoarthritis patients prior to Total Knee Arthroplasty: A cross-sectional analysis of the Longitudinal Leiden Orthopaedics Outcomes of Osteo-Arthritis study (LOAS) data

Background

To describe the prevalence of self-reported knee joint instability in patients with pre-surgery knee osteoarthritis (OA) and to explore the associations between self-reported knee joint instability and radiological features.

Use of gait simulation in the evaluation of a spring-loaded knee joint orthosis for Duchenne muscular dystrophy patients

Conventional knee-ankle orthoses are still widely used in the management of lower-extremities instabilities. Often, these supporting devices maintain the leg in extension during gait and contribute to an increase in postural lumbar lordosis and thoracic kyphosis. This paper presents a new dynamic knee-ankle orthosis equipped with a spring-loaded knee mechanism which provides a more natural and comfortable gait by allowing knee flexion while insuring knee stability during stance. A mathematical model of the dynamic joint is proposed and a nonlinear optimisation technique is used to determine its parameters. A simulation of the dynamic joint behaviour over a gait cycle is presented and its main characteristics are clinically verified in a prototype fitted bilaterally to a Duchenne muscular dystrophy patient.     

A neural network approach to the biopsy diagnosis of early acute renal transplant rejection

AIMS: To develop and test a neural network to assist in the histological diagnosis of early acute renal allograft rejection. METHODS AND RESULTS: We used three sets of biopsies to train and test the network: 100 'routine' biopsies from Leicester; 21 selected difficult biopsies which had already been evaluated by most of the renal transplant pathologists in the UK, in a study of the Banff classification of allograft pathology and 25 cases which had been classified as 'borderline' according to the Banff classification in a review of transplant biopsies from Oxford. The correct diagnosis for each biopsy was defined by careful retrospective clinical review. Biopsies where this review did not provide a clear diagnosis were excluded. Each biopsy was graded for 12 histological features and the data was entered into a simple single layer perception network, designed using the MATLAB neural network toolbox. Results were compared with logistic regression using the same data, and with 'conventional' histological diagnosis. If the network was trained only with the 100 'routine' cases, its performance with either of the other sets was poor. However, if either of the 'difficult' sets was added to the training group, testing with the other 'difficult' group improved dramatically; 19 of the 21 'Banff' study cases were diagnosed correctly. This was achieved using observations made by a trainee pathologist. The result is better than was achieved by any of the many experienced pathologists who had previously seen these biopsies (maximum 18/21 correct), and is considerably better than that achieved by using logistic regression with the same data. CONCLUSION: A neural network can provide a considerable improvement in the diagnosis of early acute allograft rejection, though further development work will be needed before this becomes a routine diagnostic tool. The selection of cases used to train the network is crucial to the quality of its performance. There is scope to improve the system further by incorporating clinical information. Other related areas where this approach is likely to be of value are discussed.     

A stereological approach to the study of neural organogenesis in Xenopus laevis

Summary Stereological methods are applied to the study of structural changes undergone, during neurulation, by the neuroepithelium of early embryos of Xenopus laevis. In light microscopy, we evaluate: the section area of the neuroepithelium, the nucleocytoplasmic ratio, the volume fraction of the intercellular spaces, of the nuclei and of the cytoplasm. In electron microscopy, the volumetric density and the surface ratio of mitochondria as well as the surface density of the endoplasmic reticulum are measured. Occasionally, the data found for Xenopus are compared to those found earlier in a similar study of the chicken embryo.     

An accurate method for locating the joint line during revision total knee arthroplasty: A radiologic study in the Chinese population

BackgroundThe systems for precisely locating the joint line during primary and revision total knee arthroplasty are still controversial, and they should be better evaluated in the Chinese population.MethodsA total of 451 standard anteroposterior knee radiographs from 451 healthy Chinese people (283 males and 168 females, the average age of 33.26 years, range 20–50 years) were included to measure the femoral width (FW) and the distances from the adductor tubercle (AT), the medial epicondyle (ME), the lateral epicondyle (LE), and the fibular head (FH) to the joint line (JL). Correlation between FW and distances from landmarks to the joint line was evaluated using Pearson correlation coefficient, and the ratios of ATJL, MEJL, LEJL, FHJL to FW were calculated.ResultsThe average distances from the AT, the ME, the LE, the FH to the JL were 49.4 ± 5.0 mm, 28.3 ± 3.1 mm, 26.9 ± 2.9 mm, 20.0 ± 4.0 mm, respectively. An excellent linear correlation was found between FW and the distance from AT to the joint line (R = 0.836, R² = 0.698); it was more reliable than the LE (R = 0.686, R² = 0.471) and the ME (R = 0.672, R² = 0.452). The average ratios of ATJL/FW, MEJL/FW, LEJL/FW were 0.553, 0.317, and 0.302, respectively. There were significant differences between our results and the studies based on the Western people.ConclusionThe AT can be used as a reliable landmark to locate the JL precisely by the formula (ATJL = 0.548 × FW in males; ATJL = 0.562 × FW in females) in the Chinese population. The LE and ME can be the second choices. Moreover, it may be better to use ratios from the research based on the same race.     

Usefulness of gait parameters obtained from inertial sensors attached to the lower trunk and foot for assessment of gait performance in the early postoperative period after total knee arthroplasty

BackgroundThis study was performed to (i) compare gait parameters obtained from inertial sensors attached to the lower trunk and foot between patients in the early postoperative period after total knee arthroplasty (TKA) and healthy age- and sex-matched controls and (ii) elucidate the association between the gait parameters and patient-reported outcome measures (PROMs).MethodThe gait performance of 19 patients who had undergone TKA was assessed using inertial sensors and PROMs obtained from the Knee Injury and Osteoarthritis Outcome Score (KOOS) 1 week before hospital discharge. The patients walked along a 15-m walkway and we calculated the following gait parameters: walking speed, coefficient of variation (CV) of stride time, unbiased autocorrelation coefficient (AC), harmonic ratio (HR), and symmetry index (SI). The same gait parameter data from 19 age- and sex-matched healthy adults (controls) were obtained from our past study.ResultsThe TKA group demonstrated slower walking speed, larger CV of stride time, lower HR in all three directions, lower AC in the vertical direction, and higher SI in the vertical direction than the healthy control group (all p < 0.05). Correlation analysis revealed that the SI in the anteroposterior direction was significantly correlated with the KOOS symptoms subscore and ADL subscore (p < 0.05).ConclusionsPatients in the early postoperative period after TKA exhibited worse gait performance as assessed by inertial sensors compared with healthy controls. Gait symmetry was correlated with PROMs. These results indicate the usefulness of assessing gait parameters after TKA.